Multispectral iris device

Abstract

The invention relates to an iris device (1) for optical imaging systems (71), comprising an aperture arrangement (5) and to a medical imaging system (72) comprising a sensor (15), in particular a camera (15a). Conventional iris devices (1) known from the art unavoidably suffer a necessary trade-off between the depth of field and the amount of light transmitted through the optical system (71), i.e. in particular the amount of light incident on the sensor (15). This disadvantage results from the fact that iris devices (Wo one) of the art transmit or reject light in the same way for all wavelengths (43), i.e. show a spectrally flat transmission property. The disadvantages of prior art iris devices (1) are overcome by the present invention by providing an aperture arrangement (5) which comprises simultaneously at least two apertures (5a) coaxially arranged with respect to a light-transmission direction (70), each of the at least two apertures (5a) limiting light in a different spectral band (49) of the at least two discrete non-overlapping spectral bands (49). The inventive medical imaging system (72) solves the above disadvantages by further comprising at least one inventive iris device (1).

Claims

1. An iris device for optical imaging systems, the iris device comprising an aperture arrangement, the aperture arrangement comprising an integrated filter system limiting light at different degrees of limitation in at least two different wavelengths, wherein the filter system comprises a plurality of filters including: a first band-stop filter defining a first spectral band and having a first aperture; a second band-stop filter defining a second spectral band and having a second aperture; and a third band-stop filter defining a third spectral band and having a third aperture; wherein the first aperture is smaller or larger than each of the second and third apertures; and wherein the first spectral band is spectrally located between the second spectral band and the third spectral band.

2. The iris device according to claim 1, wherein the filter system comprises at least one filter having at least one light transmitting spectral band.

3. The iris device according to claim 1, wherein the filter system comprises at least one filter having at least one light blocking spectral band.

4. The iris device according to claim 3, wherein the filter system comprises at least one ring-shaped edge filter which surrounds a central aperture region and in that the central aperture region is an aperture.

5. The iris device according to claim 1, wherein the filter system includes at least one filter layer embodied on a substrate.

6. The iris device according to claim 1, wherein the first band-stop filter applies to at least one of a high spectral density of a source of illumination and a high sensor sensitivity, the second band-stop filter applies to at least one of a low spectral density of the source of illumination and a low sensor sensitivity, and a diameter of the first aperture is smaller than a diameter of the second aperture.

7. The iris device according to claim 1, wherein the aperture arrangement includes at least two apertures, and one of the at least two apertures has, for a given spectral band, a variable diameter.

8. The iris device according to claim 7, wherein the iris device comprises a diaphragm having a variable diameter, the diaphragm comprising components having a spectral selective light transmissivity.

9. The iris device according to 1, further comprising an aperture magazine, wherein the aperture magazine receives at least two aperture arrangements each in a respective movable iris receptacle, wherein one of the at least two movable iris receptacles is moved into the optical axis of the optical imaging system for use.

10. The iris device according to claim 9, wherein the aperture magazine is embodied as a filter wheel.

11. An iris device for optical imaging systems, the iris device comprising an aperture arrangement, the aperture arrangement comprising an integrated filter system limiting light at different degrees of limitation in at least two different wavelengths, wherein the filter system comprises at least one filter having at least one light transmitting spectral band, wherein the filter system comprises at least one linear variable edge filter having a spectral filter edge, whose spectral position varies depending on a distance to an optical axis of the iris device.

12. An iris device for optical imaging systems, the iris device comprising an aperture arrangement, the aperture arrangement comprising an integrated filter system limiting light at different degrees of limitation in at least two different wavelengths, wherein the filter system includes at least one filter layer embodied on a substrate, wherein the filter layer comprises a plurality of sub-layers of at least two different dielectric materials having at least one of different refractive indices and different layer thicknesses, wherein the different sub-layers are at least partially embodied on the substrate in an alternating manner, and wherein the filter layer is embodied on an outer portion of the substrate, wherein the outer portion encloses an untreated portion, and the dimension of the untreated portion within the plane of the substrate defines the diameter of the aperture.

13. A medical imaging system comprising: a sensor for detecting an image; and at least one iris device comprising an aperture arrangement, the aperture arrangement comprising an integrated filter system limiting light at different degrees of limitation in at least two different wavelengths.

14. The medical imaging system according to claim 13, wherein the sensor is a camera.

Description

BRIEF DESCRIPTION OF THE DRAWING VIEWS

(1) In the figures:

(2) FIG. 1 illustrates the relationship between the aperture and the amount of transmitted light and the relationship between the aperture and the depth of field;

(3) FIG. 2 illustrates the advantage of a multispectral iris device over a conventional iris device;

(4) FIG. 3 illustrates a first embodiment of the inventive iris device;

(5) FIG. 4 illustrates a second embodiment of the inventive iris device;

(6) FIG. 5 illustrate a third embodiment of the inventive iris device;

(7) FIG. 6 illustrates a fourth embodiment of the inventive iris device;

(8) FIG. 7 illustrates a fifth embodiment of the inventive iris device;

(9) FIG. 8 illustrates a sixth embodiment of the inventive iris device; and

(10) FIG. 9 illustrates a seventh embodiment of the inventive iris device.

DETAILED DESCRIPTION OF THE INVENTION

(11) FIG. 1 shows an iris device 1, which is embodied as a single iris 3. The single iris 3 also represents the aperture arrangement 5, which is shown in five different states comprising an open state 7 and a closed state 9 of an aperture 5a.

(12) In between the open state 7 and a closed state 9 three intermediate states 11 are shown. The upper panel of FIG. 1 shows five exemplary images 13 detected by a sensor 15. The sensor 15 may be embodied as a camera 15a.

(13) It can be seen that for an open state 7 of the iris 3, respectively the aperture 5a, a first image 13a does not show any artifacts caused by a low light intensity, whereas for a closed state 9 of the iris 3, a second image 13b shows artifacts due to the low light intensity.

(14) In the lower panel, five images 13 are shown, whereas the images 13 comprise two objects 17 which are located at different distances to the optical imaging system.

(15) In case of an open state 7 of the iris 3 only one object 17 may be sharply imaged whereas the other object appears blurred in the image. This is shown in the third image 13c, whereas in the fourth image 13d, which corresponds to the closed state 9 of the iris 3, both objects 17 are imaged sharply.

(16) FIG. 2 shows the advantages of a multispectral iris device 1a over a conventional iris device 1b.

(17) The images 13 shown in FIG. 2 are exemplarily taken with an optical microscope with two different operation modes. In the case of the conventional iris device 1b an open state 7 will result in an open state result 7a, whereas the closed state 9 of the Iris 3 will result in a closed state result 9a.

(18) In the open state result 7a, the color reflectance image 19, which is obtained by illumination of a sample with a source of illumination 18, comprises blurred regions 21 and the fluorescence image 23 clearly shows fluorescent structures 25. The fluorescence image 23 is also obtained by illumination with a source of illumination 18, wherein different sources of illumination 18 may be applied for the color reflectance image 19 and the fluorescence image 23.

(19) On the contrary, if the closed state 9 of the iris 3 is chosen, the color reflectance image 19 does not show any blurred regions 21 and is completely focused, whereas the fluorescence image 23 is completely black and does not show any fluorescent structure 25.

(20) Therefore, a conventional iris device 1b always requires deciding a setting of the conventional iris device 1b, which is between the optimum for the color reflectance mode and the optimum for the fluorescence mode.

(21) The right-hand side of FIG. 2 represents the color reflectance image 19 and fluorescence image 23 recorded with the inventive multispectral iris device 1a. As can be seen, the color reflectance image 19 does not show any blurred region 21 and the fluorescence image 23 does, at the same time, show clear fluorescent structures 25.

(22) Thus, the inventive multispectral iris device 1a allows simultaneously providing the optimal setting for the color reflectance mode and the fluorescence mode.

(23) FIG. 3 shows that the first embodiment of an inventive iris device 1, which comprises an aperture arrangement 5 and two apertures 5a, a first aperture 5b represents the open state 7 and has a diameter D which equals the maximum diameter D.sub.max. In other words, the first aperture 5b of the two apertures 5a is limited by an iris frame 27.

(24) The iris frame 27 surrounds a filter system 26 and receives a substrate 29 which comprises a filter 31, which is comprised of a filter layer 32 with a plurality of sub-layers 33 of at least two different dielectric materials 35.

(25) The different dielectric materials 35 may have a different refractive index 36a and/or a different layer thickness 36b.

(26) The filter 31 is embodied in a ring-shape 37, i.e. the filter surrounds a central aperture region 39 with an outer portion 38, the central aperture region 39 having an aperture diameter D which is a first diameter D.sub.1 which is smaller than the maximum diameter of the apertures D.sub.max. The central apertures region 39 is an untreated portion 39a.

(27) The right-hand side of FIG. 3 shows a functional dependence of the transmissivity 41 on the wavelength 43. The simplified filter characteristics 45 shows a bandpass filter 47 which defines two different spectral bands 49, namely, as shown in FIG. 3, the fluorescence band 51 and a residual spectral band 53, which is, simply speaking, comprising all wavelengths 43 spectrally located below the fluorescence band 51. The fluorescence band 51 is a light transmitting spectral band 54 for the filter system 26 of the iris device 1 shown in FIG. 3, whereas the residual spectral band 53 is a light blocking spectral band 56.

(28) The filter characteristics 45 indicate that within the fluorescence band 51, the transmissivity 41 of the bandpass filter 47 equals 1, whereas for the residual spectral band 53 the transmissivity 41 equals 0.

(29) Due to its filter characteristics 45 the ring-shaped filter 31 acts as an iris 3 with a first aperture 5b for all wavelengths 43 smaller than the wavelength 43 of the fluorescence band 51.

(30) All wavelengths 43 of the fluorescence band 51 are transmitted through an iris 3 with a second aperture 5c, which in this case corresponds to an open state 7 of the iris 3.

(31) Therefore, the residual spectral band 53, which may be the spectral band 49 of the color reflection mode, is affected by the first aperture 5b which is in a closed state 9, which consequently increases the depth of field for the residual spectral band 53. On the other hand, the fluorescence band 51 which may be a spectral band 49 with a low light intensity, profits from an open state 7 of the iris 3.

(32) An optical axis 69 is not shown in FIG. 3 for reasons of clarity but may be seen in FIG. 4.

(33) FIG. 4 shows a second embodiment of the inventive multispectral iris device 1a, which comprises three individual substrates 29, each comprising a filter 31. Each of the filters 31 is embodied in a ring-shape 37 and comprises a central aperture region 39 having a first aperture diameter D.sub.1, a second aperture diameter D.sub.2 and a third aperture diameter D.sub.3.

(34) The inventive multispectral iris device 1a is oriented essentially centered and perpendicular to the optical axis 69, which is defined by the optical imaging system (see FIG. 6). A light-transmission direction 70 is indicated as well, which is oriented parallel to the optical axis 69.

(35) In FIG. 4 the third diameter D.sub.3 is smaller than the first diameter D.sub.1, which is in turn smaller than the second diameter D.sub.2.

(36) Furthermore, each of the three filters 31 comprises a filter characteristics 45 being denoted 45a, 45b and 45c. Each filter 31 is a band-stop filter 55, more specifically a multiple band-stop filter.

(37) The first 45a, second 45b and third filter characteristics 45c belong to a first band-stop filter 55a, a second band-stop filter 55b and a third band-stop filter 55c and will be explained in the following with the short-wavelength side 57 of the filter characteristics 45 shown, as the principal is repeated on the long-wavelength side 59.

(38) Each of the filter characteristics 45a, 45b and 45c comprises at least two spectral bands 49, namely a spectral stop band 61 which is the light blocking spectral band 56 and which is spectrally located adjacent to at least one residual spectral band 53.

(39) The embodiment of the multispectral iris device 1a shown in FIG. 4 separates the short-wavelength side 57 in three spectral bands 49a, 49b and 49c, whose separation is valid for all three filter characteristics 45a-45c.

(40) The first filter characteristic 45a yields a zero transmissivity 41 for the first spectral band 49a, the second filter characteristics 45b yields a zero transmissivity 41 for the second spectral band 49b, and the third filter characteristics 45c yields a zero transmissivity 41 for the third spectral band 49c.

(41) Each filter characteristics 45a-45c yields a transmissivity 41 of one for the two out of the three spectral bands 49a-49c which are not the spectral stop band 61 of the corresponding filter characteristics 45a-45c.

(42) FIG. 4 furthermore shows that the spectral band 49a-49c are adjacent to each other but do not overlap, i.e. there is no wavelength which is neither blocked by the first filter 31a, nor by the second filter 31b, nor by the third filter 31c.

(43) Furthermore, the filter characteristics 45a-45c shown in the left-hand side of FIG. 4 are combined with the spatial structure of the filter, i.e. the ring-shape 37 and the corresponding aperture diameter D.sub.1-D.sub.3.

(44) In the present embodiment shown in FIG. 4, the spectral stop band 61 of the first filter characteristics 45a is transmitted through an iris 3 with a diameter D.sub.1, the spectral stop band 61 of the second filter characteristics 45b is transmitted through an iris 3 of diameter D.sub.2 and the spectral stop band 61 of the third filter characteristics 45c is transmitted through an iris 3 of the diameter D.sub.3.

(45) FIG. 5 shows a third embodiment of the inventive multispectral iris device 1a and respective design steps.

(46) The plot shown in the upper left side of FIG. 5 illustrates the desired throughput plot 63 which shows the functional dependence of the throughput 65 on the wavelength 43.

(47) The lower left side of FIG. 5 illustrates the functional dependence of the aperture diameter D on the wavelength 43. This diameter plot 67 is calculated from the desired throughput plot 63.

(48) In the diameter plot 67 a multitude of spectral bands 49 is shown, whereas for each of the spectral bands 49 a diameter D may be determined. This is exemplarily shown for the example spectral band 49e, which has an aperture diameter D.sub.e. The corresponding aperture diameter D.sub.e may also be seen in the lower right panel of FIG. 5, where the corresponding example substrate 29e is provided with an example filter 31e. The example filter 31e has an example filter characteristics 45e, which is shown in the upper right panel of FIG. 5.

(49) In the example filter characteristics 45e the band-stop filter 55 comprises a spectral stop band 61, which corresponds to the example spectral band 49e. In other words, the aperture diameter D.sub.e only applies to the example spectral band 49e which corresponds to the example spectral stop band 61e.

(50) Wavelengths 43 located outside the example spectral stop band 61e are not affected by the example filter 31e and are transmitted through the respective example filter 31e.

(51) In conclusion, each of the plurality of filters 31 of substrates 29 only applies to the corresponding spectral stop band 61 indicated in the upper right panel of FIG. 5.

(52) FIG. 6 shows a fourth embodiment of the inventive iris device 1, wherein the iris device 1 comprises an aperture magazine 64 which is embodied as a filter wheel 66. The filter wheel 66 receives, in the embodiment shown, four aperture arrangements 5 in four moveable iris receptacles 68 of the filter wheel 66.

(53) Only one of the aperture arrangements 5 is inserted into and aligned to the optical axis 69 of the optical imaging system 71. The optical imaging system 71 is only indicated and may for instance be a medical imaging system 72.

(54) FIG. 7 shows a fifth embodiment of the inventive iris device 1 in which a known mechanical diaphragm 73 with components 75 is combined with the inventive filters 31. Each of the components 75 is embodied as a blade 77 with a kidney-shaped, which is only indicated in the left diaphragm 73 of FIG. 7 for reasons of clarity.

(55) The left side of FIG. 7 shows one isolated blade 77 which is fixed at a rotation center 79 and which may be moved towards the optical axis 69, which is indicated as an encircled X.

(56) If all blades 77 of the diaphragm 73 shown in FIG. 7 are rotated towards the optical axis 69, the movement of all blades 77 is synchronized, the aperture diameter D of the resulting filter geometry is a variable diameter D.sub.d.

(57) As the blades 77 of the diaphragm 73 are embodied as filters 31 with a corresponding filter characteristics (not shown), the resulting variable diameter D.sub.d only applies to the spectral band (not shown) which is affected by the filter 31 used.

(58) The right-hand side of FIG. 7 shows a diaphragm 73 with a second embodiment of blades 77 of a different shape.

(59) FIG. 8 shows a sixth embodiment of the inventive iris device 1 which is comprising two edge filters 81, wherein the shown iris device 1 is used for color imaging, in particular to tune the relative intensity of colors inverse proportionally to the sensors sensitivity.

(60) The iris device 1 comprises of two edge filters 81a and 81b having a first filter characteristics 45a and a second filter characteristics 45b.

(61) Each of the edge filters 81 is embodied as a low-past filter 83, i.e. wavelengths 43 shorter than an edge wavelength 85 are completely transmitted, whereas wavelengths 43 longer than the edge wavelength 85 are blocked by the corresponding edge filter 81. The edge wavelength 85 represents a spectral filter edge 86.

(62) The first edge filter 81a has a first edge wavelength 85a and the second edge filter 81b has a second edge wavelength 85b. All wavelengths 43 shorter than the first edge wavelength 85a are completely transmitted by either of the two edge filters 81 and interact with the aperture of diameter D corresponding to the open state 7. Those wavelengths constitute a first spectral band 49a.

(63) Wavelengths of the first spectral band 49a have a first aperture diameter D.sub.1.

(64) Accordingly, the second spectral band 49b located in between the two edge wavelengths 85a and 85b have an aperture diameter D.sub.2 and wavelengths located in the third spectral band 49c have the aperture diameter D.sub.3.

(65) FIG. 9 shows a seventh embodiment of the inventive iris device 1, which is embodied as a linear variable edge filter 87.

(66) The linear variable edge filter 87 comprises a multitude of filter characteristics 45 which are shown in different plots. A first plot 89a shows the dependence of the transmissivity 41 on the wavelength 43, whereas the different edge wavelengths 85 shown correspond to different radiuses D/2.

(67) A second plot 89b represents the desired throughput plot 63 and shows the dependence of the radius D/2 on the edge wavelength 85.

(68) The third plot 89c is a three-dimensional plot of the transmissivity 41, the wavelength 43 and the radius D/2. The third plot 89c shows the dependence of the transmissivity 41 on the spatial coordinate, the radius D/2 and the spectral coordinate, the wavelength 43.

REFERENCE SIGNS

(69) 1 iris device 1a multispectral iris device 1b conventional iris device 3 iris 5 aperture arrangement 5a aperture 5b first aperture 5c second aperture 7 open state 7a open state result 9 closed state 9a closed state result 11 intermediate state 13 images 13a first image 13b second image 13c third image 13d fourth image 15 sensor 15a camera 17 object 18 source of illumination 19 color reflectance image 21 blurred region 23 fluorescence image 25 fluorescent structure 26 filter system 27 iris frame 29 substrate 29e example substrate 31 filter 31a first filter 31b second filter 31c third filter 31e example filter 32 filter layer 33 plurality of sub-layers 35 dielectric material 36a refractive index 36b layer thickness 37 ring-shape 38 outer portion 39 central aperture region 39a untreated portion 41 transmissivity 43 wavelength 45 filter characteristics 45a first filter characteristics 45b second filter characteristics 45c third filter characteristics 45e example filter characteristics 47 bandpass filter 49 spectral band 49a first spectral band 49b second spectral band 49c third spectral band 49e example spectral band 51 fluorescence band 53 residual spectral band 54 light transmitting spectral band 55 band-stop filter, such as a multiple band-stop filter 55a first band-stop filter 55b second band-stop filter 55c third band-stop filter 56 light blocking spectral band 57 short-wavelength side 59 long-wavelength side 61 spectral stop band 63 desired throughput plot 64 aperture magazine 65 throughput 66 filter wheel 67 diameter plot 68 iris receptacle 69 optical axis 70 light-transmission direction 71 optical imaging system 72 medical imaging system 73 diaphragm 75 component 77 blade 79 rotation center 81 edge filters 81a first edge filter 81b second edge filter 85 edge wavelength 86 spectral filter edge 87 linear variable edge filter 89a first plot 89b second plot 89c third plot D.sub.1 first diameter D.sub.2 second diameter D.sub.3 third diameter D.sub.max maximum diameter D.sub.e example diameter D.sub.v variable diameter D/.sub.2 distance to optical axis/radius