OPTICAL ARRANGEMENT AND METHOD FOR CORRECTING CENTRATION ERRORS AND/OR ANGLE ERRORS

Abstract

The invention relates to an optical arrangement and a method for correcting centration errors and/or angle errors in a beam path. The beam path here comprises an optical compensated system in which at least two optical elements are present and aligned relative to one another such that imaging aberrations of the optical elements are compensated. According to the invention, a correction unit is arranged in an infinity space of the beam path and between the at least two optical elements, wherein the correction unit changes the propagation direction of radiation propagating along the beam path and the correction unit either has a reflective surface or is embodied to be transmissive for the radiation. The correction unit is movable such that the angle of a change in the propagation direction can be set.

Claims

1. An optical system for correcting centration errors and/or angular errors, comprising, in a beam path: an optical compensated system having a plurality of optical elements in which at least two optical elements of the plurality of optical elements are aligned relative to one another such that imaging aberrations of the at least two optical elements are compensated; and a correction unit arranged in an infinity space of the beam path and between the at least two optical elements, wherein the correction unit changes the propagation direction of radiation propagating along the beam path and the correction unit either has a reflective surface or is embodied to be transmissive for the radiation, and wherein the correction unit is adjustable such that the angle of a change in the propagation direction can be set.

2. The optical system according to claim 1, wherein the correction unit includes a mirror.

3. The optical system according to claim 1, wherein the correction unit includes a prism pair and each prism of the prism pair is rotatable about a normal of an entry face of the relevant prism.

4. The optical system according to claim 1, wherein the correction unit is adjustable in a controlled or feedback-controlled manner.

5. The optical system according to claim 1, wherein one of the optical elements of the compensated system is inclined relative to the beam path.

6. The optical system according to claim 5, further comprising a detector that is configured to be inclined relative to the beam path, wherein an object field inclination with respect to one of the optical elements of the compensated system is compensated by the inclination of the detector.

7. A method for correcting centration errors and/or angular errors in a beam path of an optical system, the optical system including an optical compensated system having a plurality of optical elements in which at least two optical elements of the plurality of optical elements are aligned relative to one another such that imaging aberrations of the at least two optical elements are compensated and a correction unit arranged in an infinity space of the beam path and between the at least two optical elements, wherein the correction unit is configured to change the propagation direction of radiation propagating along the beam path and the correction unit either has a reflective surface or is embodied to be transmissive for the radiation, and wherein the correction unit is adjustable such that the angle of a change in the propagation direction can be set, the method comprising the steps of: measuring a current imaging aberration and ascertaining a target position of the correction unit that results in a minimization of a current imaging aberration as a calibration value; moving the correction unit into the target position; measuring the current imaging aberration and comparing it to a permissible tolerance value; ascertaining a new target position if the current imaging aberration exceeds the permissible tolerance value or ending the method if the current lateral chromatic aberration falls below the permissible tolerance value.

8. A method for correcting centration errors and/or angular errors in a beam path of an optical system, the optical system including an optical compensated system having a plurality of optical elements in which at least two optical elements of the plurality of optical elements are aligned relative to one another such that imaging aberrations of the at least two optical elements are compensated and a correction unit arranged in an infinity space of the beam path and between the at least two optical elements, wherein the correction unit is configured to change the propagation direction of radiation propagating along the beam path and the correction unit either has a reflective surface or is embodied to be transmissive for the radiation, and wherein the correction unit is adjustable such that the angle of a change in the propagation direction can be set, the method comprising the steps of: defining an object field and arranging a sample at the center of the object field; ascertaining the position of the imaged representation of the sample in an image field as a reference position; and comparing the ascertained image field position to an expected image field position as a calibration value; and generating control commands corresponding to the calibration value and controlling the correction unit.

9. The method according to claim 8, further comprising: interchanging at least one optical unit arranged in the beam path between the optical elements of the compensated system for another optical unit, and repeating the steps of ascertaining the position of the imaged representation of the sample in an image field as a reference position, generating control commands, and controlling the correction unit.

10. The method according to claim 8, further comprising storing the ascertained calibration values in relation to the optical elements and/or optical units that are located in each case in the beam path in a repeatedly retrievable form.

11. The method according to claim 10, further comprising: ascertaining the optical elements and/or optical units located in the beam path of the compensated system as a current configuration; retrieving the calibration values stored in accordance with the ascertained configuration; and generating control commands on the basis of the retrieved calibration values.

12. The method according to claim 7, further comprising storing the ascertained calibration values in relation to the optical elements and/or optical units that are located in each case in the beam path in a repeatedly retrievable form.

13. The method according to claim 12, further comprising: ascertaining the optical elements and/or optical units located in the beam path of the compensated system as a current configuration; retrieving the calibration values stored in accordance with the ascertained configuration; and generating control commands on the basis of the retrieved calibration values.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The invention is explained in more detail below on the basis of exemplary embodiments and figures. In the figures:

[0040] FIG. 1A shows a schematic illustration of a compensated system with a microscope objective and a tube lens and also of the lateral chromatic aberration of the microscope objective (upper partial image), the tube lens (middle partial image) and the resulting lateral chromatic aberration (bottom partial image), with the resulting lateral chromatic aberration being zero;

[0041] FIG. 1B shows a schematic illustration of the lateral chromatic aberration of the microscope objective (upper partial image), the tube lens (middle partial image) and the resulting lateral chromatic aberration (bottom partial image), with the resulting lateral chromatic aberration not being equal to zero;

[0042] FIG. 2 shows a schematic illustration of a first exemplary embodiment of an optical arrangement according to the invention with an occurring centration error and a lateral chromatic aberration in the image plane;

[0043] FIG. 3 shows a schematic illustration of the first exemplary embodiment of an optical arrangement according to the invention with a corrected centration error and without residual lateral chromatic aberration in the image plane;

[0044] FIG. 4 shows a schematic illustration of a second exemplary embodiment of an optical arrangement according to the invention with a prism pair in the infinity space of the beam path;

[0045] FIG. 5 shows a schematic illustration of a prism pair and of a drive and a control unit;

[0046] FIG. 6 shows a schematic illustration of a third exemplary embodiment of an optical arrangement according to the invention with a correction unit and an additional optical element in the infinity space of the beam path; and

[0047] FIG. 7 shows a schematic illustration of a fourth exemplary embodiment of an optical arrangement according to the invention, in which one of the optical elements of the compensated system and a detector are designed so they are able to be inclined.

DETAILED DESCRIPTION

[0048] FIG. 2 shows, as a first exemplary embodiment of the invention, a microscope 1 with an optical arrangement 2. An objective 5 and a tube lens 6 are present as the optical elements of a compensated system 4 in a beam path 3 of the compensated system 4. A correction unit 8 comprising a mirror 9 is present on the optical axis 7 of the beam path 3 in the infinity space of the beam path 3 between the objective 5 and the tube lens 6. Said mirror 9 is adjustable by being controlled or feed-back controlled by way of a drive 10, wherein the drive 10 is controllable by way of control commands of a control unit 11. Radiation captured by way of the objective 5 travels from an object field 12, for example on or in a sample (not illustrated) to be imaged and/or observed, along the optical axis 7 to a first interchangeable component 14 and a second interchangeable component 15 as respectively reflective additional optical units in the beam path 3. The second interchangeable component 15 has, based on its position relative to the optical axis 7, an angular error . The radiation deflected with this angular error is incident on the mirror 9 of the correction unit 8 and is reflected toward the tube lens 6, by way of whose effect the radiation is focused at the plane of an image field 13. A detector 18 for capturing image data can be arranged in the plane of the image field 13.

[0049] Owing to the angular error imparted on the radiation, the ray course shown by way of example is focused not along the optical axis 7 into the image field 13, but rather a deviation from the optical axis 7 occurs. The absolute value of the deviation here also can be dependent on the wavelength of the captured radiation. FIG. 2 shows by way of example the profiles of rays of two wavelengths, the points of incidence of which in the image plane 13 are located away from the optical axis 7 as lateral chromatic aberration.

[0050] If such a lateral chromatic aberration is ascertained or if required calibration values are held retrievably in a database, corresponding control commands are generated by way of the control unit 11 and transmitted to the drive 10. The drive 10 is used to incline the mirror 9 of the correction unit 8 by a correction angle . The correction angle (3 is chosen such that the rays of all wavelengths are incident again on the optical axis 7 into the image plane 13 or on the detector 18 and no lateral chromatic aberration occurs any more (FIG. 3).

[0051] In further embodiments of the invention, in particular of the method and the configuration of the control unit 11, alternative or additional imaging aberrations such as axial chromatic aberration, coma and/or astigmatism can be corrected.

[0052] The correction unit 8 can be embodied for an inclination of the adjustable mirror 9 about the x-axis x, the y-axis y and/or the z-axis z of a Cartesian coordinate system, and correspondingly it is also possible for multiaxial angular errors to be corrected.

[0053] The correction unit 8 in a second exemplary embodiment according to FIG. 4 can have a (difference) prism pair consisting of a first prism 16 and a second prism 17. Both prisms 16, 17 can be rotated in each case and independently of one another about the normal of an entry face of the relevant prism 16, 17 in a manner controlled by the drive 10. The drive 10 is designed for a delivery movement of each individual prism 16, 17.

[0054] The mode of action of such a prism pair is illustrated in FIG. 5. A ray that is incident along the optical axis 7 onto the entry face of the first prism 16 is deflected by the effect of the first prism 16 in the direction of the front arrow. Due to the effect of the second prism 17, a deflection in the direction of the middle arrow can take place. The effectively effective deflecting effect and direction of the ray after passage through the prism pair can be obtained from the vector addition of the two prismatic effects and is symbolized by the beam path 3 in the direction of the rear arrow.

[0055] The effective prismatic effect can be advantageously set so that the lateral chromatic aberration in the plane of the image field 13 is corrected. The lateral chromatic aberration of the prism pair can additionally be used to correct the lateral chromatic aberration. The latter can be constant over the image field 13. The center of the image field 13 here can be offset slightly in the case of an optimally corrected lateral chromatic aberration.

[0056] An improved embodiment consists in the use of two achromatic prisms 16, 17, whereby the offset of the image field center can be compensated in the case of an optimally corrected lateral chromatic aberration. Each prism 16, 17 of the difference prism pair consists for example of two individual prisms that are advantageously bonded or cemented together and are made from materials (e.g. glasses) having different dispersion properties.

[0057] A third exemplary embodiment of an optical arrangement 2 according to the invention with a correction unit 8 and two additional optical elements 9, 14 in the infinity space of the beam path 3 is shown in FIG. 6. The correction unit 8 is arranged downstream of the objective 5 and is itself embodied as a first interchangeable component 14. The latter is adjustable and additionally acts as a correction unit 8. An angular error caused by the second interchangeable component 15 can be corrected by correspondingly inclining the correction unit 8 by the correction angle . The second interchangeable component 15 is for example a reflector turret, output coupling mirror or an additional beam splitter turret.

[0058] In a fourth exemplary embodiment, at least one of the optical elements of the compensated system 4, in the case illustrated the tube lens 6, can be movable in a controlled fashion, in particular able to be inclined (FIG. 7).

[0059] The tube lens 6 can here be set individually with respect to the different additional interchangeable components 14, 15 that are effective currently in the infinity space. With the tilt or inclination of the tube lens 6, the inclination of the object field 12 that is to be imaged sharply into the plane of the image field 13 also changes. Optionally, the image field 13, e.g. the detector 13 in the form of for example a camera sensor or the camera, can be inclined to compensate for the inclination and be able to capture a perpendicularly illuminated image field 13.

[0060] In the exemplary embodiment according to FIG. 7, an angular error is introduced into the beam path 3 due to the second interchangeable component 15. Said angular error is compensated by correspondingly inclining the tube lens 6 by the correction angle using the control unit 11 and the drive 10. In addition, the image field 13 is correspondingly inclined by inclining the detector 18 used using the drive 10.