Angularly-selective illumination

Abstract

An optical apparatus comprises an illumination module (100) comprising a carrier (110), which has at least one light-transmissive region (112), for example. The illumination module (100) comprises a plurality of light sources (111), which are arranged on the carrier (110).

Claims

1. A microscope comprising: an illumination module comprising a carrier and a plurality of light sources, which are arranged on the carrier, wherein the plurality of light sources are configured to be actuated separately for light production purposes, a computing unit, which is configured to actuate the illumination module for the purposes of illuminating a specimen object from a first illumination direction with first light and to capture a first image during the illumination from the first illumination direction by means of at least one detector, wherein the computing unit is furthermore configured to actuate the illumination module for the purposes of illuminating the specimen object from a second illumination direction with second light and to capture a second image during the illumination from the second illumination direction by means of the at least one detector, wherein the computing unit is furthermore configured to determine a distance between imaging locations of the specimen object in the first image and in the second image, wherein the first light and the second light have different wavelengths and/or polarizations, and wherein the illumination of the specimen object from the first illumination direction and the second illumination direction, at least in part, occurs parallel in time.

2. The microscope as claimed in claim 1, wherein the computing unit is furthermore configured to determine a position of the specimen object parallel to the optical axis on the basis of the distance between the imaging locations of the specimen object in the first image and in the second image.

3. The microscope as claimed in claim 1, furthermore comprising: a specimen holder, which is configured to immobilize the specimen object, a motor, which is configured to displace a focal plane of the microscope in relation to the specimen holder, wherein the computing unit is configured to actuate the motor on the basis of the determined distance between the imaging locations of the specimen object in the first image and the second image.

4. The microscope as claimed in claim 1, furthermore comprising: a specimen holder, which is configured to immobilize the specimen object, a manual adjustment unit, which is configured to displace a focal plane of the microscope in relation to the specimen holder, a user interface, which is configured to output an indicator to a user, said indicator proposing an actuation of the adjustment unit on the basis of the distance between the imaging locations of the specimen object in the first image and the second image.

5. The microscope as claimed in claim 1, furthermore comprising: the at least one detector, which comprises a plurality of groups of pixels, which each have different sensitivities in relation to wavelengths and/or polarizations of light.

6. The microscope as claimed in claim 1, furthermore comprising: a plurality of detectors, at least one spectral element, which is configured to produce a plurality of partial beam paths, assigned to the detectors, on the basis of a separation of light in relation to wavelengths and/or polarizations.

7. The microscope as claimed in claim 6, wherein the at least one spectral element is selected from the following group: beam splitter; dichroic element; color filter; polarization filter; grating; filter wheel; and prism.

8. A method, comprising: illuminating a specimen object from a first illumination direction with first light and capturing a first image during the illumination from the first illumination direction, illuminating the specimen object from a second illumination direction with second light and capturing a second image during the illumination from the second illumination direction, and determining a distance between imaging locations of the specimen object in the first image and in the second image, wherein the first light and the second light have different wavelengths and/or polarizations, and wherein the illumination of the specimen object from the first illumination direction and the second illumination direction, at least in part, occurs parallel in time.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The properties, features and advantages of this invention described above and the way in which they are achieved will become clearer and more clearly comprehensible in association with the following description of the exemplary embodiments which are explained in greater detail in association with the drawings.

(2) FIG. 1 is a schematic plan view of an illumination module for angle-selective illumination and with a carrier, which has a light-transmissive region according to various embodiments.

(3) FIG. 2 is a schematic side view of the illumination module for angle-selective illumination according to FIG. 1.

(4) FIG. 3 is a schematic side view of the illumination module for angle-selective illumination according to FIG. 1, wherein, in the example of FIG. 3, a detector is partly arranged in the aperture.

(5) FIG. 4 schematically illustrates an LSM according to various embodiments, wherein, in the example of FIG. 4, the illumination module for angle-selective illumination and with the carrier is arranged in the region between a scanning optical unit of the LSM and an objective of the LSM in the beam path of a laser light source of the LSM.

(6) FIG. 5 schematically illustrates an LSM according to various embodiments, wherein, in the example of FIG. 5, the illumination module for angle-selective illumination and with the carrier is arranged downstream of a specimen holder of the LSM in relation to the laser light source of the LSM, in a passed beam path, wherein, in the example of FIG. 5, furthermore, the detector is partly formed in the aperture that is arranged centrally on the carrier.

(7) FIG. 6A schematically illustrates an LSM according to various embodiments, wherein, in the example of FIG. 6A, the illumination module for angle-selective illumination and with the carrier is arranged in the region between a scanning optical unit of the LSM and an objective of the LSM, mirrored into the beam path of the laser light source.

(8) FIG. 6B schematically illustrates an LSM according to various embodiments, wherein, in the example of FIG. 6B, a further detector is arranged in mirrored-in fashion between the scanning optical unit and the objective of the LSM, wherein the further detector is configured for imaging a specimen object during illumination by the illumination module for angle-selective illumination.

(9) FIG. 7 schematically illustrates a conventional LSM, which comprises an illumination module with a halogen light source for phase-contrast imaging.

(10) FIG. 8A schematically illustrates a microscope with a camera according to various embodiments, wherein the illumination module for angle-selective illumination is arranged in a passed beam path assigned to the camera.

(11) FIG. 8B schematically illustrates a microscope with a camera according to various embodiments, wherein the illumination module for angle-selective illumination is arranged in a passed beam path assigned to the camera.

(12) FIG. 8C schematically illustrates a microscope with a camera according to various embodiments, wherein the illumination module for angle-selective illumination is arranged in a passed beam path assigned to the camera.

(13) FIG. 9A schematically illustrates a microscope according to various embodiments, wherein the illumination module for angle-selective illumination is arranged in a beam path assigned to the camera.

(14) FIG. 9B schematically illustrates a microscope according to various embodiments, wherein the illumination module for angle-selective illumination is arranged in a beam path assigned to the camera and an imaging optical unit is arranged in the region of an aperture that is arranged centrally on the carrier.

(15) FIG. 9C schematically illustrates a microscope according to various embodiments, wherein the illumination module for angle-selective illumination is arranged in a beam path assigned to the camera and the camera is coupled to the illumination module.

(16) FIG. 10A schematically illustrates a microscope according to various embodiments, wherein the illumination module for angle-selective illumination is arranged in a detection beam path.

(17) FIG. 10B schematically illustrates the illumination module for angle-selective illumination and with the carrier and the plurality of light sources according to various embodiments, wherein the light-transmissive region is embodied as an aperture that is arranged on the carrier in off-centered fashion.

(18) FIG. 10C schematically illustrates the illumination module for angle-selective illumination and with the carrier and the plurality of light sources according to various embodiments, wherein the light-transmissive region is embodied as an aperture that is arranged on the carrier in off-centered fashion.

(19) FIG. 11 schematically illustrates the illumination module for angle-selective illumination according to various embodiments, wherein the carrier of the illumination module is formed from light-transmissive material and the light sources of the illumination module are arranged on the surface of the carrier with a low geometric fill factor.

(20) FIG. 12 schematically illustrates the illumination module for angle-selective illumination according to various embodiments, wherein the light-transmissive region of the illumination module is embodied as an aperture that is arranged centrally on the carrier.

(21) FIG. 13 schematically illustrates the illumination module for angle-selective illumination according to various embodiments, wherein the plurality of light sources of the illumination module are implemented by organic light-emitting diodes.

(22) FIG. 14 schematically illustrates the illumination module for angle-selective illumination according to various embodiments, wherein the plurality of light sources are implemented by halogen light sources.

(23) FIG. 15 schematically illustrates the illumination module for angle-selective illumination according to various embodiments, wherein the light-transmissive region and the plurality of light sources are implemented by organic light-emitting diodes.

(24) FIG. 16 is a schematic plan view of an illumination module for angle-selective illumination and with a carrier, on which a detector is attached according to various embodiments.

(25) FIG. 17 is a schematic side view of the illumination module for angle-selective illumination according to FIG. 16.

(26) FIG. 18 schematically illustrates an optical apparatus according to various embodiments with a detector and a computing unit.

(27) FIG. 19 is a flowchart of a method according to various embodiments.

(28) FIG. 20 schematically illustrates the arrangement of a specimen object outside of a focal plane of an optical apparatus.

(29) FIG. 21 schematically illustrates the determination of the z-position of the specimen object in the scenario of FIG. 20.

(30) FIG. 22 schematically illustrates the distance between reference points of a specimen object for illumination from different illumination directions.

(31) FIG. 23 is a flowchart of a method according to various embodiments.

(32) FIG. 24 schematically illustrates the illumination of a specimen object from a plurality of illumination directions with light of different wavelengths and/or polarizations.

(33) FIG. 25 schematically illustrates the illumination of a specimen object from a plurality of illumination directions with light of different wavelengths and/or polarizations.

(34) FIG. 26 schematically illustrates the illumination of a specimen object from a plurality of illumination directions with light of different wavelengths and/or polarizations.

DETAILED DESCRIPTION OF EMBODIMENTS

(35) The present invention is explained in greater detail below on the basis of preferred embodiments with reference to the drawings. In the figures, identical reference signs designate identical or similar elements. The figures are schematic representations of different embodiments of the invention. Elements illustrated in the figures are not necessarily depicted as true to scale. Rather, the different elements illustrated in the figures are reproduced in such a way that their function and general purpose become comprehensible to the person skilled in the art.

(36) Below, techniques are described in relation to an illumination module, which can be used for the angle-selective illumination of a specimen object. The illumination module comprises a plurality of light sources, which are arranged at a distance from one another, and thus can implement illumination of a specimen object from a plurality of illumination directions. Different polarizations are assigned to the different illumination directions. Then, measurement images, which correspond to the individual illumination directions, can be combined with one another. As a result, a result image can be obtained by digital post-processing, said result image having a phase contrast.

(37) Here, various examples relate to the particularly flexible combination of such an illumination module for angle-selective illumination with optical apparatuses of different configuration. Various examples describe how such an illumination module can be combined with an LSM. Further examples describe how such an illumination module can be combined with a reflected-light microscope or a transmitted-light microscope.

(38) By way of example, different examples describe how such an illumination module can be combined with a laser light source of an LSM. Here, the illumination module could be structurally connected or coupled to a PMT that is arranged in transmission geometry and configured to detect a fluorescence signal of a corresponding specimen object. To this end, the illumination module can have a light-transmissive region, for example, through which light can pass to the detector. By way of example, the illumination module could be implemented by a carrier with a centrally arranged recess/aperture as a light-transmissive region; then it can be possible to at least partly arrange the PMT in the aperture. Here it is also possible, for example, for the emission spectrum of the light sources of the illumination module to differ from the detection spectrum of the PMT. Here, the detection spectrum of the PMT can be matched to the wavelength of a laser light source and/or to the wavelength of a fluorescence signal; by way of example, the emission spectrum of the light sources of the illumination module can lie in the infrared spectral range.

(39) In further examples, it would be possible, for example, for the illumination module to have a perforated carrier, wherein no further optical elements are arranged in the aperture or apertures. In other examples, different optical elements can be arranged in the region of the at least one aperture, for example, a lens, a Bertrand lens with angle-selective shadowing, a grating, etc.

(40) In various examples, it may be possible to combine the illumination module with an optical microscope. Here, the illumination module can be arranged in a detection beam path or in a further beam path of the illumination module, for example, wherein the further beam path can at least partly differ from the detection beam path. In various examples, it is possible to combine such an illumination module with an overview camera. By way of example, the overview camera can be configured to capture an overview image of a specimen holder of the microscope. A corresponding beam path that is associated with the camera can therefore have a comparatively low magnification.

(41) By way of example, the microscope can be a conventional reflected-light microscope or transmitted-light microscope. Such techniques can be applied, in particular, in conjunction with wide-field microscopy, in which an overview image of a specimen object is created and fine positioning takes place on the basis of the overview image. The individual configuration and arrangement of the light sources of such an illumination module for angle-selective illumination can vary in different examples. By way of example, an LED array could be used as a corresponding matrix structure. In other examples, use could also be made of light sources with a comparatively large lateral extent, such as halogen light sources or organic light-emitting diodes, for example. By way of example, these could be arranged in different quadrants on the carrier in relation to a centrally arranged aperture, which forms the light-transmissive region. Optionally, it is also possible for organic light-emitting diodes themselves to have a light-transmissive configuration and thus implement the light-transmissive region.

(42) The illumination module having a light-transmissive region can be dispensed with in various examples. By way of example, the illumination module could have a continuous carrier, which is not light-transmissive, in such examples. By way of example, it would be possible here for the at least one detector to be applied, for example adhesively bonded, to the carrier. By way of example, the detector could be applied centrally or in off-centered fashion on the carrier.

(43) Different effects can be obtained by means of such techniques. By way of example, it may be possible to combine different imaging techniques with one another. By way of example, conventional, analog imaging techniques—such as analog, optical reflected-light microscopy or analog, optical transmitted-like microscopy or fluorescence imaging, for example—can be combined with techniques that are based on digital post-processing. Moreover, it is possible to combine fluorescence imaging techniques with techniques from non-fluorescence imaging. By way of example, digital techniques in conjunction with angle-selective illumination—as described in conjunction with DE 10 2014 112 242 A1—may facilitate a fully automatic or at least partly automatic production of a fitting contrast. The corresponding disclosure, in the entirety thereof, is incorporated herein by cross-reference. Therefore, such techniques can also be implemented without in-depth expert knowledge. Particularly in conjunction with the fluorescence imaging, using suitable emission spectra of the light sources of the illumination module renders it possible to avoid biological specimen objects being used up by the techniques of angle-selective illumination and thus adversely affecting the fluorescence imaging.

(44) Moreover, it is possible to implement optical apparatuses which, as described above, combine different imaging techniques but use a common objective to this end. This saves installation space and reduces costs and complexity. By way of example, by means of the techniques of angle-selective illumination, it may be possible to produce phase-contrast images; here, the provision of a specific differential phase-contrast (DIC) optics or Zernike optics may be dispensed with.

(45) FIG. 1 illustrates an exemplary illumination module 100. FIG. 1 is a plan view of the illumination module 100. The illumination module 100 comprises a carrier 101. By way of example, the carrier 101 can be configured as a solid plate. The carrier 101 can be formed from transparent material, i.e., light-transmissive material, such as glass or plastic, for example, or else it can be formed from non-light-transmissive material. By way of example, the carrier 101 could be produced from metal, for example steel or aluminum. The carrier can be embodied as a plate.

(46) In the example of FIG. 1, a total of four light sources 111 are arranged on the carrier 101 in a manner offset in relation to a geometric center, which corresponds to an axis 221. The light sources 111 are arranged in different directions in relation to the axis 221. In particular, the light sources 111 are arranged in different quadrants in relation to the axis 221. By way of example, the light sources 111 can be implemented by way of light-emitting diodes. Other types of light sources 111 can also be used. It is evident from FIG. 1 that the light sources 111 are arranged at different positions in relation to the geometric center of the carrier 101. As a result, the angle-selective illumination can be implemented, for example in a scenario in which the central axis 221 extends along a central ray of a beam path of an optical apparatus, which receives the illumination module 100. In particular, the light sources 111 are arranged more rotationally symmetric in relation to the central axis 221. This may be expedient if the angle-selective illumination should be implemented for very different directions, for example in order to produce a particularly strong phase contrast.

(47) A light-transmissive region 112 is arranged in the region of the geometric center of the carrier 101. In principle, the light-transmissive region 112 is optional. In one example, the light-transmissive region 112 can be implemented by light-transmissive solid material; examples of light-transmissive material would be, for example: glass; plastic; plastics film; etc. By way of example, the light-transmissive material can be embedded in the surrounding material of the carrier 101 and can be securely connected to the latter. By way of example, the light-transmissive region 112 could be implemented as a glass plate, which is embedded in the metallic carrier. In a further example, the light-transmissive region 112 can be implemented by a cutout or an aperture.

(48) While a single, contiguous light-transmissive region 112 is illustrated in relation to the example of FIG. 1, the provision of more than one light-transmissive region may be possible in other examples. By way of example, a plurality of apertures that are separated from one another could be provided. Here, appropriate techniques, as explained above in relation to FIG. 1, can be applied.

(49) What can be achieved as a result of the light-transmissive region is that the illumination module 100 can be combined particularly flexibly with an optical apparatus. By way of example, it may be possible for the illumination module 100 to be arranged within the beam path of the optical apparatus; then, light can pass through the light-transmissive region 112 along the beam path through the illumination module 100. In this way, the illumination module 100 can be flexibly integrated into the optical apparatus.

(50) FIG. 2 is a lateral sectional view of the illumination module 100 from FIG. 1 along the dash-dot-dotted line A-A′ in FIG. 1. In FIG. 2, the surfaces 110A, 110B of the carrier 101 are illustrated. FIG. 2 illustrates, in particular, an upper side 110A and a lower side 110B of the carrier 110. The upper side 110A and the lower side 110B have a plane embodiment; in other examples, these could also have a non-planar form.

(51) It is evident from FIG. 2 that, for example, light incident from above or below can pass along the central axis 221 through the illumination module 100 in the region of the light-transmissive region 112 without significant reflection or absorption. Therefore, it is possible to combine illumination module 100 flexibly with different optical apparatuses such as, for example, an LSM or a conventional reflected-light microscope or transmitted-light microscope. In particular, it may be possible to arrange illumination module 100 in the beam path of an optical apparatus.

(52) FIG. 2 also illustrates the illumination directions 91 respectively associated with the light sources 111.

(53) FIG. 3 illustrates aspects in respect of the arrangement of a detector 230 in the light-transmissive region, which is embodied as an aperture that is arranged centrally on the carrier 110. In one example, in which the light-transmissive region 112 is embodied as an aperture, it is possible to at least partly arrange other optically effective elements, such as, e.g., a detector 230, in the aperture. Such a scenario is shown in FIG. 3. In the example in FIG. 3, a PMT, which may be configured, for example, to detect a fluorescence signal in a biological specimen object, is arranged in the region of the aperture, which implements the light-transmissive region 112. In particular, a sensitive area 231 of the detector 230 is spaced apart from the upper side 110A; this means that the detector 230 projects beyond the upper side 110A along the axis 221. What this can achieve is that light incident from above can be detected by the detector 230 without great losses on account of the illumination module 100.

(54) FIG. 4 illustrates aspects in relation to an LSM 200. The LSM 200 comprises a first illumination module 211, which comprises a laser light source. The laser light source defines a first beam path 261 (illustrated by a dashed line in FIG. 4). A collimator optical unit 212 is provided. A scanning optical unit 213 is arranged in the beam path 261. An objective 214 is arranged close to a specimen holder 215. In relation to the first illumination module 211, the scanning optical unit 213 and the objective 214 are arranged upstream of the specimen holder 215 and directly in the beam path 261. The specimen holder 215 is configured to immobilize a specimen object in the beam path 261. The LSM 200 also comprises a detector 230, e.g., a PMT. The detector 230 is suitable for detecting a fluorescence signal of the specimen object.

(55) In the example in FIG. 4, the detector 230 is arranged downstream of the specimen holder 215 in relation to the illumination module 211, i.e., in the passed beam path 221. In other examples, the detector 230 could also be arranged upstream of the specimen holder 215 in relation to the illumination module 211. To this end, output coupling in relation to the beam path 261 could be provided, for example in the form of a partly reflective mirror as a beam splitter (not illustrated in FIG. 4).

(56) FIG. 4 also illustrate aspects in relation to the illumination module 100 for angle-selective illumination. By way of example, use could be made of the illumination module 100, which was discussed above in relation to FIGS. 1-3. FIG. 4 illustrates an exemplary arrangement of the illumination module 100 in the beam path 261. In the example in FIG. 4, the illumination module 100 is arranged between the scanning optical unit 213 and the objective 214, directly in the beam path 261. Here, it is clear that the light-transmissive region 112 has a lateral dimension that is greater than a beam width of the beam path 261 perpendicular to the beam path 261. Therefore, it is possible for the light to at least partly or largely pass through the illumination module 100 or the light-transmissive region along the beam path 261.

(57) The illumination module 100 defines a further beam path 222 (dot-dashed line in FIG. 4). The beam path 222, too, can be used to illuminate the specimen object (not illustrated in FIG. 4) on the specimen holder 215. For the purposes of detecting a signal during the illumination of the specimen object by the illumination module 100, use can be made, for example, of the detector 230 or a further detector (not illustrated in FIG. 4).

(58) FIG. 5 illustrates aspects in relation to an LSM 200. The LSM 200 according to the example of FIG. 5 substantially corresponds to the LSM 200 according to the example of FIG. 4. However, in the example in FIG. 5, the illumination module 100 is arranged at a different location in relation to the beam path 261. In the example in FIG. 5, the illumination module 100 is arranged in the passed beam path 261, i.e., on the opposite side of the specimen holder 215 in relation to the illumination module 211. In the example in FIG. 5, the detector 230 is partly arranged in the aperture implementing the light-transmissive region 112.

(59) Despite the spatial proximity between the illumination module 100 and the detector 230, an interaction between these elements 100, 230 can be comparatively low. By way of example, this can be achieved by virtue of the detection spectrum of the detector 230 being different from the emission spectrum of the light sources 111.

(60) While the detector 230 is arranged in the aperture of the light-transmissive region 112 in FIG. 5, the detector 230 and the illumination module 100 could be arranged separately from one another in the passed beam path in other examples, for example, according to an arrangement as discussed in FIG. 4.

(61) The examples above illustrated scenarios in which the carrier 110 of the illumination module 100 has a light-transmissive region 112, which is implemented by an aperture, for example. However, in other examples, it is possible for the carrier 110 not to have a corresponding light-transmissive region 112. Such a scenario is illustrated in the example in FIG. 6A.

(62) FIG. 6A illustrates aspects in relation to an LSM 200. In principle, the LSM 200 corresponds to the LSMs 200 discussed in relation to FIGS. 4 and 5 above. In the scenario in FIG. 6A, the illumination module 100 is arranged between the scanning optical unit 213 and the objective 214 in mirrored-in fashion. To this end, provision is made of a partly reflective mirror 243, which merges the beam path 222 associated with the illumination module 100 with the beam path 261. A light-transmissive region 112 is not provided.

(63) FIG. 6B illustrates aspects in relation to an LSM 200. In particular, FIG. 6B illustrates aspects in relation to a further detector 241 (for reasons of clarity, the detector 230 is not illustrated in FIG. 6B; the latter could be arranged in the passed beam path or in the reflection beam path). The further detector 241 can be used to capture signals when the specimen object is illuminated by the further illumination module 100 (not illustrated in FIG. 6B for reasons of simplicity). In the example in FIG. 6B, the detector 241 is arranged between the scanning optical unit 213 and the objective 214 in mirrored-in fashion. To this end, provision is made of a further optical unit 242 and an output coupling unit 243. The arrangement of the detector 241 in FIG. 6B is purely exemplary; by way of example, in other implementations, the detector 241 could be arranged downstream of the scanning optical unit 213 in relation to the specimen holder 215 or else it could be arranged in the passed beam path 261, i.e., downstream of the specimen holder 215 in relation to the illumination module 211.

(64) By way of example, the detector 241 may be a CCD sensor or a CMOS sensor. By way of example, the detector 241 could be part of a camera. By way of example, the detector 241 could produce an overview image. However, the detector 241 could also produce a greatly magnified image.

(65) FIG. 7 illustrates aspects in relation to a conventional LSM 200A according to reference implementations, which also comprises a further illumination module 261A in addition to the illumination module 211 with the laser light source, it being possible to use said further illumination module in combination with a suitable objective (not illustrated in FIG. 7) for phase-contrast imaging purposes. In such a conventional LSM 200A, it may be necessary to replace the objective 214 with a further objective (not illustrated in FIG. 7), depending on the illumination mode (illumination by the illumination module 211 or the illumination module 261A). This increases the required installation space and requires a complicated mechanism. Moreover, it may not be possible, or only possible to a restricted extent, to simultaneously implement an illumination by the illumination module 211 and the illumination module 261A. By way of example, the mirror 261B may be tilted depending on the selected illumination.

(66) FIG. 8A illustrates aspects in relation to an optical microscope 300, for example a reflected-light microscope or a transmitted-light microscope. The microscope 300 comprises an eyepiece 315 and an objective 314. The eyepiece 315 defines a detection beam path 321 (illustrated by the dashed line in FIG. 8A). While the example in FIG. 8A illustrates an eyepiece 315, the detection beam path 321 could also be combined with other units in other examples, for example with a CCD camera, etc. A corresponding statement applies to all examples described herein. The microscope 300 also comprises a specimen holder 215, which is configured to immobilize a specimen object in the beam path 321.

(67) In the example in FIG. 8A, a camera 310, which is used to provide an overview image of the specimen holder 215 or the specimen object, is arranged in the passed beam path 322—which does not extend through the objective 314. The illumination module 100 is also arranged in the passed beam path 322. The central axis 221 is arranged concentrically with a central ray 221 of the passed beam path 322. The central ray corresponds to the optical axis of the microscope 300. The carrier 110 of the illumination module 100 is rigidly coupled to a camera body 311. Here, the illumination module 100 can be configured according to the other examples described herein. In particular, the illumination module 100 comprises a plurality of light sources 111 (not shown in FIG. 8A). The illumination module 110 is arranged in such a way that light along the beam path 322 can pass through the light-transmissive region 112, for instance an aperture that is arranged centrally or in off-centered fashion. The camera 310 is partly arranged in the aperture. As a result of providing the illumination module 110 in the beam path 322, it is possible to carry out a particularly space-saving implementation of the angle-selective illumination.

(68) FIGS. 8B and 8C illustrate aspects in relation to an optical microscope 300, for example a reflected-light microscope or a transmitted-light microscope. In principle, the optical microscope 300 according to FIGS. 8B, 8C corresponds to the optical microscope 300 according to FIG. 8A. In particular, the camera 310 and the illumination module 100 for angle-selective illumination are arranged, once again, in the passed beam path 322. However, in this case, the carrier 110 is not securely coupled to the camera body 311 in the example of FIG. 8B. In the example in FIG. 8B, an imaging optical unit 312 that is associated with the camera 310 is partly arranged in the light-transmissive region 112. In the example in FIG. 8C, the imaging optical unit 312 is, once again, partly arranged in the light-transmissive region 112, with, however, the carrier 110 being rigidly coupled to the camera body 311.

(69) FIG. 9A illustrates aspects in relation to an optical microscope 300, for example a reflected-light microscope or a transmitted-light microscope. In principle, the microscope in FIG. 9A corresponds to the microscope 300 in FIGS. 8A-8C. However, the beam path 322 associated with the camera 310 (illustrated by the dash-dotted line in FIG. 9A) in this case also extends through the objective 314. In particular, the beam path 322 is mirrored into the detection beam path 321. To this end, the microscope 300 comprises an output coupling unit 313, for example a beam splitter such as a partly reflective mirror. The imaging optical unit 312 is arranged in the region of the beam path 322. Moreover, the illumination module 110 is arranged in the region of the beam path 322. In particular, the illumination module 110 is arranged in such a way that light can pass through the light-transmissive region 112 along the beam path 322. The central axis 221 is arranged concentrically with a central ray of the beam path 322. As a result of providing the illumination module 110 in the beam path 322, it is possible to carry out a particularly space-saving implementation of the angle-selective illumination.

(70) By way of example, it would be possible for the camera 311 to capture an image for the specimen object illuminated by the angle-selective illumination by means of the illumination module 110. It would also be possible to provide a further detector (not illustrated in FIG. 9A); the latter could be arranged in the passed beam path 322 or in the reflection beam path 322.

(71) FIG. 9B illustrates aspects in relation to a microscope 300. In principle, the microscope 300 of the example in FIG. 9B corresponds to the microscope 300 of the example in FIG. 9A. In the example in FIG. 9B, the imaging optical unit 312 is partly arranged in the light-transmissive region 112 of the illumination module 100. Here, the light-transmissive region 112 can be embodied as an aperture, as already described above. By way of example, it would be possible for a lens element, a grating and/or a filter of the imaging optical unit 312 to be arranged in the aperture. In this way, a particularly space-saving integration of the illumination module 100 can be ensured.

(72) FIG. 9C illustrates aspects in relation to a microscope 300. In principle, the microscope 300 of the example in FIG. 9C corresponds to the microscope 300 of the examples in FIGS. 8A-8C and 9A-9B. In the example in FIG. 9C, the illumination module 100 is combined with the camera 311. In this way, a particularly space-saving integration of the illumination module 100 can be ensured. By way of example, a sensor area of the camera 311 could be arranged adjacent to, or within, the light-transmissive region 112. By way of example, the camera 311 can be embodied with a secure connection to the illumination module 110.

(73) The microscope 300 of FIGS. 8A, 8B, 8C, 9A, 9B, 9C, 10 could have a further illumination module. The latter could serve to illuminate the specimen object in the case of an observation through the eyepiece. By way of example, the further illumination source could comprise a collimator optical unit and a light source. However, it would also be possible for the illumination module 100 for illuminating the specimen object to be used during the observation through the eyepiece. To this end, for example, a plurality of light sources 111 could be operated at the same time in order to facilitate a uniform illumination of the specimen object.

(74) FIG. 10A illustrates aspects in relation to a microscope 300. In principle, the microscope 300 of the example in FIG. 10A corresponds to the microscope 300 of the examples in FIGS. 8A-8C and 9A-9C. In the example of FIG. 10A, the illumination module 100 is arranged directly in the detection beam path 321 and it has an extent transversely to the detection beam path 321. This can ensure a particularly space-saving integration of the illumination module 100. There is no need to provide a separate further beam path 322.

(75) FIG. 10B illustrates aspects in relation to the illumination module 100. The illumination module 100 comprises a light-transmissive region 112, which is embodied as an aperture that is arranged in an off-centered fashion. Here, the aperture 112 has a distance 119 from the central axis 221, which may be coincident with a central ray of the respective beam path in the case of an arrangement of the illumination module 100 in an optical apparatus 200, 300.

(76) An illumination module 100 according to the example in FIG. 10B may be desirable, in particular in relation to an arrangement of the illumination module 100 in the passed beam path 322 of an optical microscope 300, i.e., in relation to the detection beam path 321 downstream of the detector; see FIGS. 8A-8C. Then, direct light that is produced by centrally arranged light sources 111—i.e., between the central axis 221 and the aperture 112—can be incident in the objective 314.

(77) In the example in FIG. 10B, the distance 119 is selected to be so small that a projection 118 of the smallest aperture of the objective 314 on the carrier 110 (illustrated by the dashed line in FIG. 10B) comprises light sources 111 and the aperture 112 is arranged adjacently. As a result, bright-field imaging can be achieved.

(78) While the example in FIG. 10B was discussed in relation to the light-transmissive region 112 implemented by an aperture, corresponding techniques can also be used in other examples for differently implemented light-transmissive regions.

(79) FIG. 10C illustrates aspects in relation to the illumination module 100. In principle, the illumination module 100 in FIG. 10C corresponds to the illumination module 100 in FIG. 10B. Here, each light source 111 comprises two channels for light with different wavelength and/or polarization. It would also be possible for each light source 111 to have more than two channels.

(80) By means of such techniques, it is possible to implement different illumination directions with light of different wavelengths and/or polarizations.

(81) FIG. 11 illustrates aspects in relation to the illumination module 100. FIG. 11 illustrates an example, in which the carrier 111 is formed from light-transmissive solid material. Then, interstices between the various light sources 111 implement the light-transmissive region 112.

(82) In the example in FIG. 11, the light sources 111 are arranged in a matrix structure with a hexagonal unit cell. Other arrangements of the light sources 111 would also be possible, for example a matrix structure with a rectangular unit cell, etc., or an unordered arrangement. By way of example, it would be possible for respectively adjacent light sources 111 of the matrix structure to have different colors and/or polarizations of the respectively emitted light.

(83) In the example in FIG. 11, the light sources 111 are arranged on the upper side 110A of the carrier 110 (in the plane of the drawing in FIG. 11) with a comparatively low geometric fill factor of less than 30% (in FIG. 11, the geometric fill factor corresponds to the sum of the areas of all black regions relative to the overall area of the carrier 110). As a result of the comparatively low geometric fill factor, it is possible for a significant quantity of incident light to be able to pass through the carrier 110 of the illumination module 100 in the region of the interstices between the various light sources 111.

(84) FIG. 12 illustrates aspects in relation to the illumination module 100. FIG. 12 illustrates an example, in which the carrier 110 is produced from non-light-transmissive material, for example aluminum or a plastics material. In the example in FIG. 12, the light-transmissive region 112 is formed by a centrally arranged aperture. By way of example, in the case of an arrangement of the illumination module 100 in a microscope or LSM, it may be possible for the space within the light-transmissive region 112/the aperture to remain free, or else for other optically effective elements, such as, e.g., a detector, a lens element, etc., to be arranged within the aperture.

(85) While FIG. 12 shows an example in which the light-transmissive region 112 is arranged in a center of the carrier 110, the light-transmissive region 112 may also be arranged away from the center of the carrier 110 in other examples. In principle, it is not necessary either for the light-transmissive region 112 to have a symmetric form in relation to a central axis.

(86) FIG. 13 illustrates aspects in relation to the illumination module 100. In FIG. 13, the various quadrants of the carrier 110 are occupied by laterally extended light sources 111. By way of example, the light sources 111 in the example of FIG. 13 can be implemented by way of organic light-emitting diodes. By means of such a configuration of the illumination module 100, illuminating the specimen object from extended solid angles may be possible.

(87) FIG. 14 illustrates aspects in relation to the illumination module 100. In FIG. 14, the various light sources 111 are embodied as halogen light sources. These are arranged symmetrically in relation to a central axis.

(88) FIG. 15 illustrates aspects in relation to the illumination module 100. In FIG. 15, the light-transmissive region 112 is implemented by light-transmissive organic light-emitting diodes 111. Here, the carrier 110 can be formed from non-light-transmissive material, for example.

(89) From a comparison of FIGS. 10-15, it is clear that the configuration of the illumination module 100 can vary greatly in various examples. In particular, configurations, as illustrated in relation to FIGS. 10-15, may be combined with one another.

(90) FIG. 16 illustrates aspects in relation to an illumination module 1000. The illumination module 1000 according to the example of FIG. 16 corresponds, in principle, to the illumination module 100 according to the example of FIG. 1. Here, the carrier 101 of the illumination module 1000—in contrast to the example in FIG. 1—has no light-transmissive region. A detector 1230 is attached to the carrier 101 in the example of FIG. 16. By way of example, the detector 1230 can be attached to the upper side 110A of the carrier 101; see FIG. 17. Then, the sensor area 1231 is at a distance from the surface 110A. By way of example, the detector 1230 can be adhesively bonded, screwed or fastened differently to the carrier 101.

(91) In the examples in FIGS. 16 and 17, the detector 1230 is arranged centrally on the carrier 101. In particular, this means that the detector 1230 is arranged centrally in relation to the axis 221. In various examples, it would also be possible, however, for the detector 1230 to be arranged on the carrier 101 in off-centered fashion. By way of example, it would be possible for different techniques, which were described above in relation to FIG. 10B, to be applied in relation to the detector 1230. Thus, it would be possible for the detector 1230 to have a distance from the center of the carrier 110, with at least one of the light sources 111 of the illumination module 100 being arranged between the center of the carrier 110 and the detector 1230. Once again, the distance between the detector 1230 and the center of the carrier 110 can correspond to a projection 118 of the aperture of the objective 314 on the carrier 110. This can promote bright-field illumination.

(92) In the examples in FIGS. 16 and 17, the module 1000 in each case has a single detector 1230. However, it would be possible in the various examples for the module 1000 to have more than a single detector, for example two or three detectors. Here, the plurality of detectors can be attached at a distance from one another on the carrier 101. By way of example, the plurality of detectors 1230 could be attached to different sides of the axis 221 or in different quadrants in relation to the axis 221.

(93) FIG. 18 is a schematic illustration of the optical apparatus 200, 300, which is configured for angle-selective illumination according to various examples described herein. The optical apparatus 200, 300 comprises the detector 241, which detects light that is emitted from the light sources 111 of the illumination module 110. The optical apparatus 200, 300 also comprises a computing unit 299. The computing unit 299 is configured to actuate the illumination module 100 or the light sources 111 for separate and/or sequential illumination of the specimen object from a plurality of illumination directions. To this end, different light sources 111 can be activated separately and/or in sequence, for example. By way of example, an illumination direction can denote the illumination from an angle or solid angle. Furthermore, for each illumination direction, the computing unit 299 is configured to actuate the detector 241 for capturing a respective measurement image of the object.

(94) Furthermore, the computing unit 299 is configured to combine the measurement images to obtain a result image. The result image has a phase contrast. Here, the computing unit 299 can be configured to apply techniques of digital post-processing, which are disclosed in relation to DE 10 2014 112 242 A1.

(95) FIG. 19 is a flowchart of a method according to various examples. By way of example, the computing unit 299 could be configured to carry out the method according to FIG. 19.

(96) Initially, a current illumination direction 91 is selected in step 2001. Then, one or more light sources 111 are activated in step 2002 such that the illumination of a specimen object is obtained from the selected illumination directions. An associated measurement image is captured in step 2003, for example by means of a suitable detector 241, for example by means of a CCD detector or a CMOS detector, an overview camera and/or a photomultiplier. To this end, the detector 241 can be actuated in a suitable manner. The measurement image is captured while the specimen object is illuminated from the current illumination directions.

(97) Then, a check is carried out in step 2004 as to whether it is necessary to capture a further measurement image from a further illumination direction 91. If this is the case, steps 2001-2003 are carried out again.

(98) Subsequently, a result image is produced in step 2002. The result image has a phase contrast for an imaged object (phase-contrast image). The phase-contrast image is determined by combining the measurement images, which were captured in the iterations of step 2003.

(99) While the measurement images typically have no, or no significant, phase-contrast, it is possible to produce the phase-contrast image by combining the measurement images, said phase-contrast image having a significant phase-contrast component. Particularly in comparison with other conventional techniques of phase-contrast imaging, the method described in the present case can obtain the effect of a particularly simple implementation of the phase-contrast imaging on the one hand and the effect of a particularly simple, and hence cost effective and robust, configuration of the optical apparatus on the other hand.

(100) By way of example, it would be possible for the illumination directions to form pairs in each case or to be arranged in pair-wise fashion. Here, it may be possible for an illumination direction always to be assigned to only one pair. However, it would also be possible for at least some of the illumination directions to be assigned to a plurality of pairs. At least the measurement images of the illumination directions belonging to one pair can then be combined to obtain a respective result image.

(101) Different criteria for the assignment of two illumination directions 91 to a pair may apply. By way of example, geometric criteria of the illumination directions 91 of a pair may apply, for instance in relation to the optical axis; in this way, it may be possible to produce a particularly high phase-contrast component in the phase-contrast image, for example. By way of example, the illumination directions of a pair could be included symmetrically in relation to the axis of the optical apparatus along which an idealized light ray experiences no, or only little, deflection (optical axis) and/or be arranged symmetrically in relation to a plane containing the optical axis. However, as an alternative or in addition thereto, it would also be possible to take account of a time of illumination and capture as an alternative or additional criterion of the belonging of two illumination directions 91 to a pair; by way of example, those illumination directions 91, for which the respective measurement image is captured immediately in succession or successively in a timely fashion, can form a pair; in this way, a certain robustness in relation to movement artifacts could be obtained, for example. In general, a subsequent evaluation for producing the phase-contrast image can also be taken into account as an alternative or additional criterion for the belonging of two illumination directions 91 to a pair; by way of example, an individual result image could always be produced for the two measurement images of a pair by combining these measurement images.

(102) It would be possible for the two illumination directions 91 of a pair to include correlating angles with the optical axis. By way of example, correlating angles can mean: substantially the same angles or substantially the same angles in terms of magnitude; substantially can be characterized, in particular, in relation to technical limitations in the accuracy, such as, e.g., systematic or statistical errors when capturing the measurement images by the optical apparatus and/or a limitation of an illumination apparatus of the optical apparatus caused by the construction thereof. To the extent that angles which, although they are different in absolute terms, are the same within the accuracy of the optical apparatus, for example, are implemented, this can satisfy such a criterion of substantially the same angles. Such criteria apply below to corresponding specifications of angles and/or other properties of illumination directions 91 or of the optical apparatus.

(103) For the purposes of describing geometric properties of the illumination directions, it may be helpful to describe the illumination directions 91 by way of an illumination vector. The illumination vectors can be defined in relation to an origin of the optical apparatus, for instance in relation to the object and/or an intersection of a focal plane with the optical axis. A length of the illumination vectors can correspond to an amplitude of the illumination from the respective illumination direction, for example; in the subsequent explanation of the orientation of various illumination vectors, it may be possible to dispense with taking account of a length of the illumination vectors. Then, the angle included by an illumination vector with the optical axis may correspond to the angle of the respective illumination direction.

(104) By way of example, it may be desirable for illumination vectors of a pair of illumination directions to include an angle with one another, said angle being greater than 10°, preferably greater than 20°, particularly preferably greater than 40°. As an alternative or in addition thereto, it would also be possible for illumination vectors of a pair of illumination directions to each include an angle with the optical axis, said angle being greater than 5°, preferably greater than 10°, particularly preferably greater than 20°. What this can achieve is that a difference vector between the two illumination vectors of a pair of illumination directions 91 has a significant component perpendicular to the optical axis; this can increase the phase contrast in the phase-contrast image particularly strongly.

(105) In particular, it may be possible for the illumination vectors of two illumination directions of a pair of illumination directions to be transformed into one another by rotation about the optical axis of the optical apparatus through an angle of greater than 25°, preferably greater than 50°, particularly preferably greater than 85°. As a result of this, the difference vector becomes particularly large.

(106) The two illumination directions of a pair of illumination directions can also be arranged in such a way that associated illumination vectors include with one another, by way of rotation about the optical axis, an angle of 160° to 200°, advantageously of 175° to 185°, particularly advantageously of 180°. It would also be possible for the associated illumination vectors to be transformed into one another by way of rotation about the optical axis through an angle of 70° to 110°, advantageously of 85° to 95°, particularly advantageously of 90°. Expressed differently, the two illumination vectors of a pair of illumination directions 91 can lie in a plane and can be arranged symmetrically or substantially symmetrically in relation to the optical axis. The optical axis can lie in this plane (be contained in this plane), for example, if a rotation through 180° transforms the two illumination vectors into one another. In this way, a comparatively large phase-contrast component can be obtained in the phase-contrast image because the two illumination directions of a pair are arranged in complementary fashion to one another in this way.

(107) In general, it may be desirable to use a relatively large number of illumination directions for the purpose of obtaining the phase-contrast image. In particular, the phase-contrast component in the phase-contrast image can increase in the case of an appropriate arrangement of the various illumination directions 91. By way of example, it would be possible to take account of a plurality of pairs of illumination directions. By way of example, it would be possible to illuminate the object sequentially from 2 or 4 or 6 or 8 illumination directions or more illumination directions. By way of example, it would be possible for a first pair of illumination directions to determine a first difference vector of associated illumination vectors. Accordingly, a second pair of illumination directions can determine a second difference vector of associated illumination vectors. The first and second difference vector can include an angle with one another, for example an angle of 70° to 110°, advantageously 85° to 95°, particularly advantageously 90°.

(108) Accordingly, it would also be possible for a first plane to be defined by the illumination vectors of a first pair of illumination directions 91. By way of example, a second plane can be defined by the illumination vectors of a second pair of illumination directions. The first plane and the second plane can include an angle, for example an angle of 70° to 110°, with one another, advantageously 85° to 95°, particularly advantageously 90°. By way of example, the planes can be defined by virtue of the respective illumination vectors lying in the plane. It would also be possible for the planes to be defined by a normal vector that is oriented parallel to a difference vector of the respective illumination vectors; the optical axis can lie in the plane.

(109) Thus, in this way, difference vectors of the illumination vectors of the two pairs of illumination directions 91 can include a comparatively large angle of up to 90° with one another; as a result, the phase-contrast in the phase-contrast image can be increased along various image directions. By way of example, a phase-contrast component in the phase-contrast image can be particularly large along those image directions for which the illumination vectors of a pair of illumination directions have a component perpendicular to the optical axis. In particular, a phase-contrast component in the phase-contrast image can be particularly large along those directions for which the difference vector of the illumination vectors of a pair of illumination directions has a component perpendicular to the optical axis. Therefore, it may be desirable to use complementary and/or symmetrically arranged illumination directions. In order to produce an isotropic phase contrast in the phase-contrast image, it may be desirable for the illumination directions to include uniformly distributed angles with the optical axis.

(110) Such illumination directions 91, or illumination vectors as described above, can be implemented by suitable arrangement and/or extent of the light sources 111 on the carrier 101.

(111) The above-described techniques can also be used to determine a position of a specimen object parallel to the optical axis of an optical apparatus (z-position). To this end, use can be made, in particular, of the different illumination modules described herein, which facilitate an illumination from different illumination directions.

(112) In the three-dimensional space spanned by x, y, z-axes, the z-component of the position may thus be determined; the optical axis defines the z-axis and is e.g. parallel to the latter. On the basis of the z-position determined, e.g. a focus unit of the optical apparatus, for example a motor coupled to a specimen holder, may be driven and, in this way, the object may be positioned in the focal plane of the optical apparatus depending on the z-position determined (focusing of the object). Autofocus applications can be implemented. If no autofocus is present for the motor-driven adjustment of the focal plane but there is a manual adjustment unit instead, an indicator can be output to the user via a user interface, for example. This indicator can instruct the user to undertake a certain actuation of the adjustment unit in order thereby to facilitate focusing of the object. By way of example, the user interface can comprise an optical output and/or an acoustic output. By way of example, the direction of rotation of a setting dial of the adjustment unit could be indicated.

(113) Images of the object which image the object particularly sharply may subsequently be captured. Such techniques may be employed in a wide variety of fields, e.g. in microscopy or in fluorescence measurement or in parallel with phase contrast imaging.

(114) By means of the techniques described herein, it may be possible, in particular, to facilitate particularly fast focusing. To this end, it may be possible for the illumination of the specimen object from different illumination directions to occur at least partly parallel in time. To this end, it would be possible, for example, to carry out the illumination from different illumination directions by means of light with different wavelengths or colors or polarizations. In this way, it is possible to separate the signals that correspond to the different illumination directions.

(115) For the exemplary application of the fluorescence measurement, it may be possible, for example, to determine the z-position before and/or during the fluorescence measurement by means of the techniques described below. It may thus be ensured that the fluorescing object is situated in the focal plane of the optical apparatus during the measurement; in this way, it is possible to increase an accuracy during the fluorescence measurement. The techniques described in detail below are based on evaluating a first image and a second image with illumination of the object from different first and second illumination directions. In this case, this angle-selective illumination may be carried out e.g. in particular with one or more wavelengths that are outside the fluorescence-active range of the fluorescing specimen. In principle, the z-position may thus be determined at the same time as the fluorescence measurement. This may make it possible, for example, in particular, to position moving specimens as a function of time reliably in the focal plane. Furthermore, the z-position may generally be determined from only two illumination processes; by this means, too, it is possible to reduce a light-toxic effect on the fluorescing object. When measuring dyes, the wavelength of the light for determining the z-position may be chosen e.g. outside the excitation range of the dyes. In this way, bleaching of the dyes may be reduced or avoided. One possible light wavelength which is used for determining the z-position would be e.g. in the infrared range.

(116) Determining the z-position may mean in this case: quantitatively determining the z-position, e.g. in relation to the focal plane or in relation to some other suitable reference system of the optical apparatus; and/or qualitatively determining the z-position, e.g. in relation to the criterion of whether or not a specific predefined position parallel to the optical axis, such as e.g. the focal plane, is attained.

(117) FIG. 20 schematically illustrates an optical apparatus 200, 300, e.g., a microscope or an LSM. A beam path of the light extends from an illumination module 100, 1000 to a detector 241. The illumination module 100, 1000 can be implemented in a manner corresponding to the examples described above, i.e., for example, with a carrier and a plurality of light sources arranged on the carrier.

(118) The optical axis 221 and the focal plane 3160 are illustrated in FIG. 20. It is evident from FIG. 20 that the specimen object 3100 is positioned parallel to the optical axis 221 outside the focal plane 3160. The illustration shows a z-position 3150 which is measured in relation to the focal plane 3160 (denoted by Δz in FIG. 20). In such a case, it may be possible particularly simply and rapidly to drive the focus unit of the optical apparatus 200, 300 in order to carry out a focusing. In particular, it may be unnecessary to carry out e.g. a transformation of the z-position 3150 in relation to the focal plane 3160. It would also be possible to determine the position of the object 3100 in some other suitable reference coordinate system of the optical apparatus.

(119) A first illumination direction 91-1 and a second illumination direction 91-2 are furthermore illustrated in FIG. 21. A first image 3230-1 is captured for the first illumination direction 91-1. A second image 3230-2 is captured for the second illumination direction 91-2. As is evident from FIG. 21, the first illumination direction 91-1 includes a first angle 3251-1 with the optical axis 221. Therefore, an imaging location 3220-1 of the object 3100 in the first image 3230-1 in accordance with FIG. 21 appears offset toward the left relative to the optical axis 221. In FIG. 21, the first angle 3251-1 is denoted by a. As is furthermore evident from FIG. 21, the imaging location 3220-2 of the object 3100 in the second image 3230-2 in the illustration in FIG. 21 is offset toward the right relative to the optical axis 221. This is the case on account of the second angle 3251-2 (denoted by β in FIG. 21) included between the second illumination direction 91-2 and the optical axis 221. By way of example, it would be possible for the two illumination directions 91-1, 91-2 to be associated with different colors or polarizations of the respectively employed light.

(120) It is evident from FIG. 21 that an absolute value of the first angle 3251-1 differs from an absolute value of the second angle 3251-2. In general, it would be possible for the first and second illumination directions 91-1, 91-2 to be arranged symmetrically in relation to the optical axis 221. It would e.g. also be possible for one of the two illumination directions 91-1, 91-2 to be oriented parallel to the optical axis 221. In general, it is also possible for the specimen object 3100 to have an offset relative to the optical axis 221, i.e., to be displaced within an xy-plane relative to the optical axis 221. In general, it is furthermore not necessary for the first illumination direction 91-1, the second illumination direction 91-2 and the optical axis 221 to lie in one plane (in the xz-plane in the scenario in FIG. 21). This means that e.g. the first illumination direction 91-1 and/or the second illumination direction 91-2 may be tilted out of the xy-plane.

(121) Instead of the sharply delimited illumination directions 91-1, 91-2, it is also possible to use illumination directions that implement the illumination of the specimen object 3100 over a certain solid angle. To this end, more than two light sources, for example, could be used to implement a single illumination direction or else a light source with a large extent in relation to the specimen object 3100 could be used.

(122) Since the object 3100 is illuminated with finite angles 3251-1, 3251-2 relative to the optical axis 221, a pure phase object which brings about no or only a small attenuation of the amplitude of the light passing through may also be imaged in the first and second images 3230-1, 3230-2. This enables a diverse application of the present techniques to different specimens, in particular, e.g., biological specimens.

(123) FIG. 21 furthermore illustrates a distance 3250 between the imaging locations 3220-1, 3220-2 of the object 3100 in the first and second images 3230-1, 3230-2 (designated by Δx in FIG. 21). Initially, it is possible to qualitatively determine that the distance 3250 does not disappear. In this way, the z-position 3150 may already be determined qualitatively as not equal to zero. By way of example, it would be possible, by iteratively repositioning the object 3100 at different reference positions (not shown in FIG. 21) parallel to the optical axis 221, to determine the z-position 3150 qualitatively as equal or near to zero. For this purpose, the specimen object 3100 could, for instance, be repositioned iteratively parallel to the optical axis 221 until the distance 3250 is minimized. A corresponding control loop could be implemented.

(124) However, it would also be possible for determining the z-position 3150 furthermore to be based on the first angle 3251-1 and the second angle 3251-2. The z-position 3150 may then be determined quantitatively. For this purpose, as set out below, trigonometrical relationships between the first angle 3251-1, the second angle 3251-2 and the distance 3250 may be taken into account.

(125) The following applies to the scenario of FIG. 21:
Δz=a.Math.cos α=b.Math.cos β   (1)
where a denotes a distance between the specimen object 3100 and the imaging location 3220-1 of the object 3100 in the first image 3230-1 along the first illumination direction 91-1 and b denotes a distance between the specimen object 3100 and the imaging location 3220-2 of the object 3100 in the second image 3230-2 along the second illumination direction 91-2 (a and b are not illustrated in FIG. 21). This formula results from the definition of the cosine for right-angled triangles.

(126) By applying the sine law for general triangles, the following is obtained:

(127) $\begin{array}{cc}\frac{\Delta x}{\sin \left(\alpha +\beta \right)}=\frac{b}{\sin \left(90°-\alpha \right)}=\frac{b}{\cos \alpha }.& \left(2\right)\end{array}$

(128) Combining equations 1 and 2 results in:

(129) $\begin{array}{cc}\Delta z=\Delta x.Math.\frac{\cos \alpha \cos \beta }{\sin \left(\alpha +\beta \right)}.& \left(3\right)\end{array}$

(130) With the aid of equation 3, it is possible to determine the z-position 3150 on the basis of the first angle 3251-1 and the second angle 3251-2 and furthermore on the basis of the distance 3250 between the imaging locations 3220-1, 3220-2. In particular, the z-position 3150 may be determined solely by double illumination and simultaneous capture of the first and second images 3230-1, 3230-2. A light loading of the object 3100 may be minimized, e.g. in comparison with the abovementioned scenario with iterative positioning of the object 3100 at different reference positions parallel to the optical axis 221.

(131) It may be desirable to increase an accuracy for determining the z-position 3150. The accuracy for determining the z-position 3150 is typically associated directly with the first angle 3251-1, the second angle 3251-2 and the distance 3250. Therefore, the accuracy when determining the z-position 3150 may be limited at least by a pixel size in the first image 3230-1 and the second image 3230-2.

(132) An error in the distance 3250—designated as Δx′ hereinafter—is transferred as follows to an error of the z-position 3150:

(133) $\begin{array}{cc}\Delta z^{\prime }=\Delta x^{\prime }.Math.\frac{\cos \alpha \cos \beta }{\sin \left(\alpha +\beta \right)}.& \left(4\right)\end{array}$

(134) If the specimen object 3100 has a significant extent in the xy-plane, it may be desirable, e.g. to determine the distance 3250 between specific reference points in the first image 3230-1 and the second image 3230-2. The reference points may mark a specific part of the object 3100, e.g. a particularly prominent part or a part that is particularly important for the imaging. In general, it is also possible to determine the distance 3250 for a plurality of pairs of reference points of the object 3100. In this way, it may be possible, by repeatedly applying equation 3, for different parts of the object 3100, to determine the z-position 3150 in each case. In other words, the z-position 3150 can thus be determined in a spatially resolved manner in the xy-plane.

(135) It may thus be desirable to determine the distance 3250 particularly accurately. In this context it may be possible to apply a wide variety of techniques which enable the distance 3250 to be determined particularly accurately. Such techniques may include e.g.: landmark recognition; determining an optical centroid of the object 3100 in the first image 3230-1 and/or in the second image 3230-2; a user input; an aberration correction. In one simple scenario, e.g. the user could select a specific reference point of the object 3100 in the first image 3230-1 and select the corresponding reference point in the second image 3230-2. By means of landmark recognition, it may be possible, for example, to carry out such a selection of reference points in an at least partly automated manner. It would also be possible to use the optical centroid as a reference point for determining the distance 3250. The aberration correction may be used e.g. to take account of known incorrect imagings on account of aberrations in the optical apparatus 200, 300. By way of example, it may be possible, by taking account of previously known aberrations, e.g., in the illumination apparatus of the optical apparatus and/or in the detector optical unit of the optical apparatus, to take account of distortions in the first and second images that may lead to a displacement of the imaging locations of the object. Such displacements may then be eliminated computationally or reduced computationally and the actual distance may be determined particularly accurately.

(136) A further limitation of the accuracy when determining the z-position 3150 may result from the coherent depth of field of the detector 241 of the optical apparatus 200, 300. In particular, it should be ensured that the specimen object 3100—even in the case of a significant displacement relative to the focal plane 3160—is still imaged in the first image 3230-1 and the second image 3230-2. However, it may be unnecessary to achieve a sharp imaging of the object 3100; in particular techniques described above, such as e.g. the determination of the optical centroid of the object 3100, may also be applied in a case in which the specimen object 3100 is imaged only unsharply in the images 3230-1, 3230-2.

(137) While FIGS. 20 and 21 show a situation in which the specimen object 3100 is positioned along the optical axis 221, that is to say that it intersects the optical axis 221, the techniques described above may also be used to determine the z-position for such scenarios in which the specimen object 3100 has a specific offset parallel to the x-direction and/or parallel to the y-direction relative to the optical axis 221. In general terms, the above-described techniques for determining the position 3150 of the object parallel to the optical axis 221 may thus enable the determination of the z-component of the position of the object 3100 in the three-dimensional space spanned by the x, y, z-axes.

(138) FIG. 21 furthermore shows a situation in which two illumination directions 91-1, 91-2 are used for determining the z-position. In general, it is also possible to use a greater number of illumination directions 91-1, 91-2 for determining the z-position 3150 of the object 3100. By way of example, three or four or ten or more illumination directions 91-1, 91-2 may be used. It would be possible, for example, for the different illumination directions 91-1, 91-2, to apply the abovementioned techniques in each case in pairs, e.g. to apply equation 3 in each case in pairs. In this way, e.g. the z-position 3150 of the object 3100 may be determined multiply and a suitable average value may be formed therefrom. In this way, it may be possible, for example, to determine the z-position 3150 of the object 3100 particularly accurately. In general, it is possible to use a wide variety of techniques for combining a larger data set consisting of imaging locations 3220-1, 3220-2 of a plurality of illumination directions 91-1, 91-2. By way of example, equation 3 could be suitably modified or a plurality of z-positions obtained from the different illumination directions 91-1, 91-2 could be consolidated after multiple application of equation 3. In other words, by means of a plurality of illumination directions 91-1, 91-2 or redundant illumination directions 91-1, 91-, it may be possible to achieve a higher accuracy when determining the z-position 3150; it is possible, for example, in particular, to achieve an accuracy which is higher than a resolution of corresponding images from which the imaging locations 3220-1, 3220-2 are determined.

(139) Here it is possible for the first light used to illuminate the specimen object 3100 from the first illumination direction and the second light used to illuminate the specimen object 3100 from the second illumination direction or, in general, for the light of the different used illumination directions to differ from one another. This means that the first light may have different wavelengths than the second light. As an alternative or in addition thereto, the first light could have a different polarization than the second light. As a result, it is possible for the illumination of the specimen object 3100 from the first illumination direction and the illumination of the specimen object 3100 from the second illumination direction to occur at least partly parallel in time. As a result, particularly fast autofocusing of the specimen object 3100 may be facilitated. Such techniques may also be applied to more than two illumination directions.

(140) By way of example, two detectors could be provided for separating the first light and the second light, said detectors each being associated with a filter that is configured according to the properties of the respective light. Thus, the filters can implement a spectral element that facilitates filtering or separation of the light in respect of its spectral properties. By way of example, the spectral element may be selected from the following group: beam splitter; dichroic element; color filter; polarization filter; filter wheel; and prism. It would also be possible for a detector to be used, said detector having different groups of pixels, which each have different sensitivities in relation to wavelengths and/or polarizations of light.

(141) FIG. 22 schematically illustrates an imaging of specimen object 3100 in the first image 3230-1 (shown by a solid line in FIG. 22) and in the second image 3230-2 (shown by a dashed line in FIG. 22). The specimen object 3100 has a significant extent in the xy-plane, i.e., perpendicular to the optical axis 221. The illustration shows three possible reference points 3600-1, 3600-2, 3600-3, 3600-4 for the imaging of the object 3100 in the first image 3230-1. In principle, the choice of the reference points 3600-1-3600-4 is not particularly restricted. However, the reference points 3600-1-3600-4 illustrated in FIG. 22 may be found particularly reliably in the first and second images 3230-1, 3230-1. By way of example, the distance 3250 could be determined between the first reference point 3600-1 (see FIG. 22), since this is the highest point of the object 3100 in the images 3230-1, 3230-2 and can thus be found easily and reliably. The reference point 3600-4 denotes e.g. the optical centroid of the object 3100 in the images 3230-1, 3230-2.

(142) By way of example, the distance 3250 could be determined with the aid of an image correlation calculation and a search for maximum within the image correlation: In some examples, the position of this maximum can directly determine the value of dx; see equation 3. In order to increase the robustness, it is also possible to use a threshold on the correlation image: in this way, it is possible to span an area in which the centroid is then sought after. The position of the centroid can also then determine dx directly. Such a technique can be advantageous, in particular, if the object comprises a plurality of planes.

(143) FIG. 23 is a flowchart of a method according to various embodiments. The specimen object is illuminated from a first illumination direction in step 4001. A corresponding first image is captured. The specimen object is then illuminated from a second illumination direction in step 4002. Once again, a corresponding second image is captured.

(144) By way of example, for the purposes of illuminating the specimen object, it would be possible to use an illumination module having a plurality of light sources and, for example, a light-transmissive region according to various examples described herein.

(145) By way of example, it would be possible for steps 4001, 4002 to be carried out at least partly parallel in time. By way of example, it would be possible for 4001, 4002 to be carried out in parallel in time as a single-shot measurement. To this end, respectively different light can be used in steps 4001 and 4002, i.e., light that differs in respect of at least one spectral property such as wavelength and/or polarization, for example.

(146) In order to facilitate a separation of the light to capture the first image and the second image, use can then be made of a spectral element with a plurality of detectors or with a detector having a plurality of groups of pixels that are associated with the different spectral properties of the light. FIG. 24 shows an exemplary implementation in which respectively different color or polarization filters 5001, 5002 are associated with the two illumination directions 91-1, 91-2. FIG. 25 shows an exemplary implementation in which different color or polarization filters 5001, 5002 are arranged in a filter wheel 5050. FIG. 26 shows an exemplary implementation in which different color or polarization filters 5001, 5002 are associated with different detectors 230.

(147) Referring back to FIG. 23: The distance between imaging locations of the specimen object in the first and second image is determined in step 4003. By way of example, these imaging locations can be identified on the basis of landmarks.

(148) On the basis of the determined distance, it is then possible, for example, to determine the z-position of the specimen object, i.e., the distance to the focal plane. As an alternative or in addition thereto, it is also possible to implement an autofocus application, in which, for example, the motor of a specimen holder is actuated for focusing purposes.

(149) To summarize, a description has been given above of techniques which—e.g., by applying equation 3 or by repositioning the object parallel to the optical axis—enable the z-position 3150 to be determined particularly rapidly and accurately. A rapid focusing of the object 3100 becomes possible as a result.

(150) In conclusion, techniques in relation to illumination modules for angle-selective illumination were described above. Such techniques render it possible to combine the angle-selective illumination flexibly with various optical apparatuses.

(151) It goes without saying that the features of the embodiments and aspects of the invention described above can be combined with one another. In particular, the features can be used not only in the combinations described but also in other combinations or on their own without departing from the scope of the invention.

(152) While various examples were described above in relation to an LSM and in relation to a microscope with an eyepiece, it is also possible to use corresponding techniques for other optical apparatuses in other examples. In particular, the illumination modules with carrier and light-transmissive region, as described herein, can also be used for other optical apparatuses.

(153) While various examples were described above in relation to fluorescence imaging, corresponding techniques can also be used for other types of imaging. This may mean that use can be made of other detectors which, for example, are not suitable for detecting a fluorescence signal.

(154) While various examples were described above in relation to an illumination module with a carrier, which has a light-transmissive region, corresponding techniques can also be applied to a carrier that has no light-transmissive region in some examples.