MICROSCOPE OR ENDOSCOPE ASSEMBLY AND METHOD FOR REDUCING SPECULAR REFLECTIONS

Abstract

The invention relates to a microscope or endoscope assembly (1), in particular for a surgical microscope such as an ophthalmic microscope. Especially in eye surgery, but also in other application concerning life tissue, specular reflections of the illumination light are unwanted because they may hide important information contained in a diffuse reflection at the same location. In order to suppress such unwanted specular reflection, the microscope or endoscope assembly according to the invention comprises an observation region (4), in which an object (6) to be observed, such as an eye, can be arranged. The assembly further comprises an illumination light path (8) which extends from an illumination light entry region (24), where illumination light enters into the assembly, to the observation region. Further, an observation light path (10) is comprised, which extends from the observation region (4) to a light exit region (34), where the light leaves the assembly and may be collected by an observation subassembly (36), such as at least one camera and/or at least one ocular. In the illumination light path, a first polarizing subassembly (16) is arranged, to create polarized illumination light (18). In the observation light path (10) a second polarizing subassembly (32) is arranged, which is configured to filter out the polarized illumination light (18) passing the first polarizing subassembly (16). To ensure coaxial illumination and observation of the object, a beam splitter (30, 40) is provided, which is arranged in the illumination light path (8) between the light entry region (24) and the observation region (4) and in the observation light path (10) between the observation region (4) and the light exit region (34). By the complementary filtering action of the first and second polarizing subassembly, specular reflections by the object can be suppressed and/or eliminated.

Claims

1. A microscope or endoscope assembly (1) comprising: an observation region (4) in which an object (6) to be observed can be arranged; an illumination light path (8) which extends from an illumination light entry region (24) to the observation region (4); an observation light path (10) which extends from the observation region (4) to a light exit region (34); a first polarizing subassembly (16) arranged in the illumination light path (8); a beam splitter (30, 40) arranged in the illumination light path (8) between the observation region (4) and the light entry region (24), and in the observation light path (10) between the light exit region (34) and the observation region (4); and a second polarizing subassembly (32) arranged in the observation light path (10), the second polarizing subassembly (32) being configured to filter out polarized light (18) passing the first polarizing subassembly (16) and the beam splitter (30, 40).

2. The microscope or endoscope assembly (1) according to claim 1, wherein the first and second polarizer subassemblies (16, 32) each comprise at least one linear polarizer (22).

3. The microscope or endoscope assembly (1) according to claim 1, wherein at least one of the first and the second polarizing subassemblies (16, 32) comprises a polarization rotor (44).

4. The microscope or endoscope assembly (1) according to claim 1, wherein the first and the second polarizing subassemblies (16, 32) share a common polarization rotor (44).

5. The microscope or endoscope assembly (1) according to claim 3, wherein the polarization rotor (44) is adapted to be attached to an object (6) to be observed in the observation region (4).

6. The microscope or endoscope assembly (1) according to claim 4, wherein the polarization rotor (44) is adapted to be attached to an object (6) to be observed in the observation region (4).

7. The microscope or endoscope assembly (1) according to claim 2, wherein the at least one linear polarizer (22) is integrated into the beam splitter (40).

8. The microscope or endoscope assembly (1) according to claim 7, wherein the beam splitter (40) is a polarizing beam splitter.

9. The microscope or endoscope assembly (1) according to claim 8, wherein linearly polarized illumination light (18) is incident on the polarizing beam splitter (40), and the polarization direction (20) of the incident polarized illumination light (18) corresponds to the polarization direction (20) of light reflected by the polarizing beam splitter (40).

10. The microscope or endoscope assembly (1) according to claim 8, wherein at least one further polarizing beam splitter (42) is located in the illumination path (8).

11. The microscope or endoscope assembly (1) according to claim 10, wherein the further polarizing beam splitter (42) is located between the polarizing beam splitter (40) and the illumination light entry region (24).

12. The microscope or endoscope assembly (1) according to claim 10, wherein the further polarizing beam splitter (42) splits the illumination light path (8) into two sub-paths (8a, 8b), and wherein a polarization rotor (44) is arranged in at least one of the two sub-paths (8a, 8b).

13. The microscope or endoscope assembly (1) according to claim 12, wherein the polarization direction (20) of the illumination light (12) behind the first polarizing subassembly (16) is the same in both of the two sub-paths (8a, 8b).

14. An upgrade kit for generating a microscope or endoscope assembly (1) according to claim 2 in a microscope or endoscope (2), the upgrade kit comprising at least two devices (16, 32) for linear polarization of light (12, 14) and at least one beam splitter (30, 40).

15. The upgrade kit according to claim 14, wherein the microscope or endoscope (2) is an ophthalmic miscroscope.

16. A method for operating an endoscope or a microscope (2) comprising the steps of: generating polarized illumination light (18) having a polarization direction (20); directing the polarized illumination light (18) onto an observation object (6), wherein at least some of the polarized illumination light (18) is reflected by the object (6); filtering out, from the polarized illumination light (18) reflected by the object (6), light having the same polarization direction (20) as the polarized illumination light (18) directed onto the object (6).

17. The method according to claim 16, wherein the endoscope or microscope (2) is an ophthalmic microscope.

Description

BRIEF DESCRIPTION OF THE DRAWING VIEWS

[0041] In the following, the same reference numerals are used throughout the drawings for elements, which correspond to each other with respect to function and/or design.

[0042] In the drawings

[0043] FIG. 1 shows a schematic representation of a microscope or endoscope assembly according to the invention;

[0044] FIG. 2 shows a schematic representation of another microscope or endoscope assembly according to the invention;

[0045] FIG. 3 shows a schematic representation of another microscope or endoscope assembly according to the invention; and

[0046] FIG. 4 shows a schematic representation of another microscope or endoscope assembly according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0047] First, the configuration of a microscope or endoscope assembly 1 according to the invention will be explained with reference to FIG. 1.

[0048] The microscope and endoscope assembly 1, in short microscope assembly in the following, is adapted to be part of or to be installed in a surgical microscope or endoscope 2, in particular an ophthalmic microscope, without being limited to such an application. The microscope or endoscope 2 is shown only schematically and only in FIG. 1.

[0049] It is further shown to comprise an observation region 4, in which an object 6 to be observed is placed in operation of the microscope or endoscope 2. The observation region 4 may be part of the microscope or endoscope assembly 1. Although the observation region 4 may not be a structural part of the microscope assembly 1 or the microscope or endoscope 2, it is nonetheless a functional part at least in operation, as the technical effects of the components of the microscope assembly 1 or the microscope or endoscope 2 aim to improve for a great part the imaging of the object 6 to be observed in the observation region 4.

[0050] The microscope assembly 1 comprises an illumination light path 8 and an observation light path 10. The illumination light path 8 is the path along which illumination light 12 is directed towards the observation region 4 or, more specifically, onto the object 6 to be observed. In FIG. 1, light in general is schematically depicted by the p and s polarization vectors.

[0051] The observation light path 10 is defined by observation light 14. The observation light 14 is light, for the greatest part or exclusively illumination light 12, which is reflected off the object 6.

[0052] In the illumination light path 8, a first polarizing subassembly 16 is arranged. The first polarizing subassembly 16 generates polarized light 18 having a polarization direction 20 from the observation light 14 incident onto the first polarizing subassembly 16. The polarization direction 20 may be, as exemplarily shown in FIG. 1, linear or circular. To generate linearly polarized light 18, the first polarizing subassembly 16 may comprise a linear polarizer 22. For generating circularly polarized light 18, the first polarizing subassembly 16 may comprise a circular polarizer (not shown). To form such a circular polarizer, a polarization rotor, such as a quarter-wave plate (not shown) may simply be arranged behind the linear polarizer 22, i.e. on the side of the linear polarizer 22 which faces away from the incident illumination light 12.

[0053] The illumination light 12 enters the microscope assembly 1 at a light entry region 24. An illumination subassembly 26 comprising one or more light sources 28 may be located at the light entrance region 24 and be included in the microscope assembly 1 and/or the microscope or endoscope 2. Such an inclusion may e.g. occur if the illumination subassembly already generates polarized light 18, i.e. the first polarizing subassembly 16 is included in the illumination light path 8 in the illumination subassembly 26.

[0054] The microscope assembly 1 further comprises a beam splitter 30 which is located both in the illumination light path 8 and the observation light path 10. At least one of the illumination light path 8 and the observation light path 10 is deflected by the beam splitter 30 by reflection. Between the beam splitter 30 and the observation region 4, the illumination light path 8 and the observation light path 10 preferably are arranged coaxially to one another. The beam splitter 30 preferably is a broadband beam splitter.

[0055] In FIG. 1 and the remaining embodiments, it is only for illustrative purposes, that the polarized light 18 from the first polarization subassembly 16 is reflected at beam splitter 30, i.e. the first polarizing subassembly 22 is located between the light entry region 24 and the beam splitter 30. The reflected light 14 passes through the beam splitter 30. This configuration can also be reversed in that the light entering the microscope assembly 1 at the light entry region 24 passes the beam splitter 30 and the light 14 reflected off the observed object 6 is reflected at the beam splitter 30.

[0056] In the observation light path 10, a second polarizing subassembly 32 is located. The configuration of the second polarizing subassembly 32 may be the same as for the first polarizing subassembly 16, except that the filtering function is complementary, i.e. that the second polarizing subassembly 32 filters out light having the polarization direction 20 which is allowed to pass the first polarizing subassembly 16.

[0057] For example, the second polarizing subassembly 32 may also comprise a linear polarizer 22 which blocks the passage of light having the polarization direction 20 which allowed it to pass (or is generated by) the linear polarizer 22 of the first polarizing subassembly 16.

[0058] The second polarizing subassembly 32 may be located between the beam splitter 30 and a light exit region 34. At the light exit region 34, the observation light 14 may leave the microscope assembly 1. In particular, at the light exit region 34 an observation subassembly 36 such as one or more cameras or one or more oculars may be located.

[0059] In the following, the function of the microscope assembly 1 of FIG. 1 is explained.

[0060] The polarized illumination light 20 hitting the object 6 undergoes both specular and diffuse reflection at the object 6. The specular reflection will maintain the polarization direction 20 of the observation light, the polarized illumination light 20 which undergoes diffuse reflection will have a random polarization which may deviate from the polarization direction of the incident illumination light. Thus, in addition to the pre-defined polarization direction 20, denoted by s in FIG. 1, imparted by the first polarizing subassembly 16, a polarization direction p orthogonal to the polarization direction 20 will be added to the observation light 10 due to diffuse reflection. Both the diffusedly and the specularly reflected light will pass through the beam splitter 30 and will be filtered out by the second polarizing subassembly 32. Thus, at the light exit region 34, or at the observation subassembly 36 respectively, only light having polarization direction p, i.e. observation light 14 not having the polarization direction 20, s, will be observed. This, in turn, means that all specular reflection will be suppressed or eliminated by the second polarizing subassembly 32.

[0061] Thickset arrows 38 indicate both the direction of the light along the illumination light path 8 and the observation light path 10 and its relative intensity compared to the intensity at the light entry region 24.

[0062] Assuming equal distribution between the two orthogonal polarization directions p, s, the light intensity after exiting the first polarizing subassembly 16 will be decreased by half compared to the intensity of the incoming illumination light, as half of the light will be filtered out. Another half of the light is lost at each passing, both reflection and transmission, of the beam splitter 30, as the beam splitter 30 reflects half of the light and transmits the other half of light. Finally, again half of the light is lost at the second polarizing subassembly 32, as one polarization direction 20 is filtered out. Thus, assuming ideal conditions and disregarding any impurities and additional losses, only 6.25% of the incident illumination light entering at the light entry region 24 will be collected at the light exit region 34.

[0063] A simple measure is able to quadruple the light output at the light exit region 34, as is shown exemplarily in FIG. 2. For the sake of simplicity, only the differences to the embodiment of FIG. 1 are explained.

[0064] In FIG. 2, the set-up of the microscope assembly 1 is the same as in FIG. 1 except that the beam splitter 30 is a polarizing beam splitter 40. The polarizing beam splitter 40 reflects completely light having a polarization direction s. The remaining light having different polarization is transmitted through the polarizing beam splitter 40.

[0065] The polarization direction s, which is reflected completely by the beam splitter 40, corresponds to the polarization direction 20 which is imparted to the observation light 20 by the first polarizing subassembly 16 or the linear polarizer 22, respectively. Thus, all the observation light 18 exiting from the first polarizing subassembly 16 is reflected by the beam splitter 40. Of the observation light 14 which is passing through the polarizing beam splitter 40, only light of the orthogonal polarization direction p is transmitted, observation light 14 having the orthogonal polarization direction s is reflected. As this polarization is allowed to pass through the second polarizing subassembly 32 or its linear polarizer 22, respectively, there will be no losses at the second polarizing subassembly 32. As indicated by the arrow 38, 25% of the light passing through the light entry region 24 will exit at the light exit region 34.

[0066] As can be further seen from FIG. 2, the two linear polarizers 22 can be omitted, as the polarization function of the linear polarizer 22 of the first polarizing subassembly 16 can be performed by the polarizing beam splitter 40. The same is true for the linear polarizer 22 of the second polarizing subassembly 32, as the polarizing function in the observation light path 10 now also located on the polarizing beam splitter 40. Thus, the first polarizing subassembly 22 and the second polarizing subassembly 32 both now can be located on the polarizing beam splitter 40.

[0067] To further increase the yield at the light exit region 34, the microscope assembly 1 of FIG. 2 can be further modified. The modification includes adding a further polarizing beam splitter 42 in the illumination light path 8 at a location between the light entry region 24 and the polarizing beam splitter 40. The polarizing beam splitter 42 splits the illumination light path 8 into two sub-paths 8a and 8b. One of the sub-paths 8a, 8b, here, light path 8b, is directed towards the polarizing beam splitter 40, where it is transmitted or, as here, reflected. The other light path 8a is directed directly towards the observation region 4 or the observed object 6, respectively.

[0068] All light reflected off the further polarizing beam splitter 42, i.e. the observation light 12 in the respective sub-path, here 8a, will be linearly polarized. Between the further beam splitter 42 and the observation region 4 in the path of the observation light 12 reflected off the further beam splitter 42, a linear polarizer 22 may be located to filter out any residual light or different polarization. To keep the set-up inexpensive and easy to maintain to be set-up, the linear polarizer 22 in the light path 8a may also be omitted.

[0069] In order to efficiently suppress any specular reflections from the observation area 4 at the light exit region 4, it is beneficial if the polarization direction 20 imparted by the further polarizing beam splitter 42 corresponds to the polarization direction s which is filtered out of the observation light by the polarizing beam splitter 40. In other words, the polarization direction in the sub-paths 8a, 8b should be the same before the illumination light enters the observation region 4. To ensure this, a polarization rotor 44 may need to be inserted into the illumination light path 8, or one of its sub-paths 8a, 8b, respectively.

[0070] This is explained in the following with exemplary reference to sub-path 8b, where the polarization rotor 44 is located between the further polarizing beam splitter 42 and the polarizing beam splitter 40 in order to rotate the polarization direction 20 of the illumination light 12 after having passed the further polarizing beam splitter 42. I.e. the polarization direction p is rotated to the polarization direction s, which then is reflected entirely by the beam splitter 40 and which corresponds to the polarization direction 20 of the illumination light 12 reflected by the further polarization beam splitter 42 in the other sub-path. The polarization rotor 44 may consist of a half-wave plate 46 and a linear polarizer 22 behind the half-wave plate 46, i.e. at the side of the half-wave plate 46 facing away from the light entry region 24. Of course, if the polarizing beam splitter 42 has a different polarization direction than shown in FIG. 3, a polarization rotor 44 may be located in sub-path 8a instead of sub-path 8b, or in both sub-paths 8a, 8b.

[0071] Due to the use of the further polarizing beam splitter 42 and the polarization rotor 44, all of the illumination light 12 can be reflected by the polarizing beam splitter 40, doubling the available light intensity at the light exit region 34.

[0072] The general set-up of having the polarization function of the first polarizing subassembly in the illumination light path 8 and the polarization function of the second polarization subassembly 32 in the observation light path 10, and having a polarizing beam splitter 40 in both the illumination light path 8 and the observation light path 10 can be used to suppress specular reflections at an outermost surface 48 of the object 6.

[0073] Such a set-up is shown in FIG. 4. It is particularly useful in ophthalmic microscopes, where the outermost layer of the eye may produce unwanted specular reflections. Again, only differences to the preceding embodiments are explained.

[0074] In order to reduce the specular reflection at the outermost surface 48 of the object 6, a polarization rotor 44 will be placed onto the object 6, so that it nestles onto the surface 48. The snug fit ensures tight contact between the polarization rotor and the object without any intermediate bubbles which would cause reflections. If necessary, a fluid may be arranged between the polarization rotor 44 and the object 6 to eliminate air and fill out any gaps.

[0075] If the object is an eye, the polarization rotor 44 may be a contact lens 50. The refractive index of the polarization rotor 44 is preferably adapted to the refractive index of the object 6 at least close to the outermost surface 48. Thus, there will be no reflections at the interface between the contact lens 50 and the object 6, however there will be reflections at the outermost surface 52 of the contact lens 50. As the specular reflections maintain the polarization direction 20 imparted by the first polarizing subassembly 16, they will be filtered out by the second polarizing subassembly 32, which in this case is included in the polarizing beam splitter 40, as in the embodiment of FIG. 2.

[0076] Specular reflections at a further internal interface 54 are maintained by this set-up in the light arriving at the light exit region 34, so that any three-dimensional information about the structure of this interface 54, which is transported by the specular reflection, is maintained. This is explained by the following.

[0077] At the polarizing rotor 44, may e.g. a quarter-wave plate which generates circularly polarized light after having passed through by the illumination light 12. In a specular reflection at the internal interface 54 of the object 6, the polarization direction, i.e. the circular polarization is maintained, only the handedness, i.e. sense of rotation of the circular polarization, is reversed, as can be seen at reference numeral 58.

[0078] If the circularly polarized light 58 reflected off the internal surface 54 again passes the polarization rotor 44, it will again be linearly polarized, only shifted in its polarization direction with respect to the polarization direction 20 of the illumination light 12 after having passed the first polarizing subassembly 16. The relative rotation of the linear polarization direction 20, here s, of the polarized illumination light 12, and the polarization direction, here p, of the light resulting from specular reflection at the internal surface 54, results in the observation light 14 being able to pass the polarizing beam splitter 40 unfiltered and proceed to the light exit region 34.

[0079] Any diffuse reflection within the object 6 will also result in light having the same polarization direction p as the light reflected specularly by the internal surface 54 and thus will also reach the light exit region 34.

[0080] In the case of FIG. 4, both the first and the second polarizing subassembly 16, 32 in effect constitute a circular polarizer of which both components are simultaneously located in the illumination light path 8 and the observation light path 10 and where the linear polarizer of both polarizing subassemblies 16, 32 is integrated in the beam splitter being a polarizing beam splitter 40. The polarization rotor part of the circular polarizer is served by the polarization rotor 44, which in this case attaches to the outermost surface 48 of the object 6.

[0081] It is to be understood that the polarization directions p and s in the preceding description are only meant to designate complementary polarization directions and do not carry any physical meaning as to a polarization direction with respect to any electric or magnetic wave directions.

REFERENCE NUMERALS

[0082] 1 microscope or endoscope assembly [0083] 2 microscope or endoscope [0084] 4 observation region [0085] 6 object to be observed [0086] 8 illumination light path [0087] 8a sub-path [0088] 8b sub-path [0089] 10 observation light path [0090] 12 illumination light [0091] 14 observation light [0092] 16 first polarizing subassembly [0093] 18 polarized light [0094] 20 polarization direction [0095] 22 linear polarizer [0096] 24 light entry region [0097] 26 illumination subassembly [0098] 28 light source [0099] 30 beam splitter [0100] 32 second polarizing subassembly [0101] 34 light exit region [0102] 36 observation subassembly [0103] 38 arrow [0104] 40 polarizing beam splitter [0105] 42 further polarizing beam splitter [0106] 44 polarization rotor [0107] 46 half-wave plate [0108] 48 outermost surface of object [0109] 50 contact lens [0110] 52 outer surface of contact lens [0111] 54 internal interface within object [0112] 56 circularly polarized light [0113] 58 reflected circularly polarized light