Optical system of a stereo video endoscope with a lateral viewing direction, and method to produce the same

Abstract

An optical system for use with a stereo video endoscope with a fixed, lateral viewing direction, including: laterally-viewing distal and proximal optical assemblies, similarly configured left and right lens system channels; the distal optical assembly couples incident light from an object space into the left and right lens system channels; the distal optical assembly includes an entrance lens, a deflection prism group and an exit lens in a direction of incident light; the deflection prism group includes first and second prisms in the direction of incident light; the first prism includes first entrance and first exit sides at an angle relative thereto; the second prism includes a second entrance side, a reflection side and a second exit side; and the first entrance side of the first prism and the reflection side of the second prism enclose an angle that is greater than a total reflection angle of the second prism.

Claims

1. An optical system for use with a stereo video endoscope with a fixed, lateral viewing direction, the optical system comprising: a laterally-viewing distal optical assembly; and a proximal optical assembly comprising: a left lens system channel; and a right lens system channel similarly configured to the left lens system channel; wherein the distal optical assembly is configured to couple incident light from an object space into the left lens system channel and into the right lens system channel of the proximal optical assembly; the distal optical assembly sequentially comprises an entrance lens, a deflection prism group and an exit lens in a direction of the incident light; the deflection prism group sequentially comprises a first prism and a second prism in the direction of the incident light; the first prism comprises a first entrance side and a first exit side at an angle relative thereto; the second prism comprises a second entrance side, a reflection side and a second exit side; and the first entrance side of the first prism and the reflection side of the second prism enclose an angle that is greater than a total reflection angle of the second prism.

2. The optical system according to claim 1, wherein the distal optical assembly is configured such that the incident light from a field of view contact the reflection side of the second prism at an angle that is greater than the total reflection angle.

3. The optical system according to claim 2, further comprising at least one aperture that borders the field of view, wherein the angle between the first entrance side and the reflection side is selected based on a material of the second prism that establishes a refraction index and the total reflection angle, and a maximum viewing angle that is established by the field of view such that total reflection of all incident light beams from the field of view occurs at the reflection side of the second prism.

4. The optical system according to claim 3, further comprising one of an anti-reflection coating disposed on the reflection side of the second prism.

5. The optical system according to claim 1, further comprising one or more of a reflective coating disposed on a first partial surface of the reflection side of the second prism, and an anti-reflection coating on a second partial surface of the reflection side, wherein the first and the second partial surfaces supplement each other to form an entire surface of the reflection side.

6. The optical system according to claim 5, wherein a distance between the first entrance side and the reflection side in the first partial surface is larger than a distance between the first entrance side and the reflection side in the second partial surface.

7. The optical system according to claim 5, wherein incident first light beams from the object space are reflected at the first partial surface of the reflective surface and are coupled into the left lens system channel, and incident second light beams from the object space are reflected at the second partial surface of the reflective surface and coupled into the right lens system channel.

8. A stereo video endoscope with a fixed, lateral viewing direction, the stereo video endoscope comprising the optical system according to claim 1.

9. A method of forming an optical system of a stereo video endoscope with a fixed, lateral viewing direction, wherein the stereo video endoscope comprises a laterally-viewing distal optical assembly and a proximal optical assembly, and wherein the proximal optical assembly comprises a left lens system channel and a right lens system channel configured similarly to the left lens system channel, and wherein the distal optical assembly is configured to couple incident light from an object space into the left lens system channel and into the right lens system channel of the proximal optical assembly, and wherein the distal optical assembly sequentially comprises an entrance lens, a deflection prism group and an exit lens in a direction of incident light, wherein the deflection prism group sequentially comprises a first prism and a second prism in the direction of incident light, wherein the first prism comprises a first entrance side and a first exit side at an angle relative thereto, and wherein the second prism comprises a second entrance side, a reflection side and a second exit side, wherein the method comprises: selecting or arranging the first and the second prisms such that the first entrance side of the first prism and the reflection side of the second prism enclose an angle that is greater than a total reflection angle of the second prism.

10. The method according to claim 9, wherein the optical system is further provided with at least one aperture that borders the field of view of the optical system, the method further comprising selecting the angle between the first entrance side and the reflection side based on a material of the second prism that establishes a refraction index and the total reflection angle and a maximum viewing angle that is set by the field of view such that total reflection of all incident light beams from the field of view occurs at the reflection side of the second prism.

11. The method according to claim 10, further comprising providing an anti-reflection coating on the reflection side of the second prism.

12. The method according to claim 9, further comprising providing one or more of a reflective coating on a first partial surface of the reflection side of the second prism and an anti-reflection coating on a second partial surface of the reflection side, wherein the first and the second partial surfaces supplement each other to form the entire surface of the reflection side.

13. A method for repairing a stereo video endoscope with a lateral viewing direction, wherein an optical system of the stereo video endoscope comprises a laterally-viewing distal optical assembly and a proximal optical assembly, and wherein the proximal optical assembly comprises a left lens system channel and a right lens system channel configured similarly to the left lens system channel, and wherein the distal optical assembly is configured to couple incident light from an object space into the left lens system channel and into the right lens system channel of the proximal optical assembly, and wherein the distal optical assembly sequentially comprises an entrance lens, a deflection prism group and an exit lens in a direction of incident light, wherein the deflection prism group sequentially comprises a first prism and a second prism in the direction of incident light, wherein the first prism comprises a first entrance side and a first exit side at an angle relative thereto, and wherein the second prism comprises a second entrance side, a reflection side and a second exit side, wherein the method comprises: replacing the deflection prism group with a replaced deflection prism group, wherein replaced defection prism group includes a replaced first prism and a replaced second prism selected or arranged such that the first entrance side of the replaced first prism and the reflection side of the replaced second prism enclose an angle that is greater than a total reflection angle of the second prism.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The embodiments are described below, without restricting the general idea of the invention, using exemplary embodiments with reference to the drawings, wherein express reference is made to the drawings with regard to all details that are not explained in greater detail in the text. In the following:

(2) FIG. 1 illustrates a schematically simplified representation of an optical system of a stereo video endoscope according to the prior art in a side view,

(3) FIG. 2 illustrates a stereo video endoscope in a schematically simplified representation,

(4) FIG. 3 illustrates a schematically simplified representation of the optical system of a stereo video endoscope, wherein the beam path of the left lens system channel is represented, and

(5) FIG. 4 illustrates a schematically simplified representation of the optical system of a stereo video endoscope, wherein the beam path of the right lens system channel is represented.

(6) In the drawings, in each case the same or similar elements and/or parts are provided with the same reference numbers, so that in each case a repeated introduction is omitted.

DETAILED DESCRIPTION

(7) FIG. 2 shows a schematically simplified perspective representation of a stereo video endoscope 2 comprising a proximal handle 4 to which for example a rigid endoscope shaft 6 is connected. The endoscope shaft 6 can be both flexible or semi-flexible. An entrance window 10 through which light from an object space 11, for example from a surgical and/or observation field enters an optical system (not shown in FIG. 2) of the stereo video endoscope 2, is located on a distal tip 8 of the endoscope shaft 6. The optical system of the stereo video endoscope 2 is arranged for example in a distal section 12 of the endoscope shaft 6. The optical system images objects that are located in the object space 11 on image sensors. These image sensors are for example those with a high resolution such as HD, 4K or the following technologies.

(8) The shown stereo video endoscope 2 is a surgical instrument. In addition, the endoscope has a fixed, lateral viewing direction. The entrance window 10 is mounted at an angle in the endoscope shaft 6 so that an optical axis of the entrance lens of the optical system (not shown) encloses a fixed angle with a direction of longitudinal extension L of the endoscope shaft 6 of the stereo video endoscope 2. This angle can be for example between 10° and 30°.

(9) A change in the viewing direction about the longitudinal axis of the endoscope shaft 6 is effectuated by a rotation of the handle 4. The optical system in the distal section 12 also rotates during this rotation of the handle 4. To retain the horizontal position of the displayed image, the rotary wheel 14 is held while rotating the handle 4. As a result, the image sensors in the inside of the endoscope shaft 6 do not also perform the rotational movement.

(10) FIG. 3 shows an optical system 20 in a schematically simplified representation according to an exemplary embodiment. Only the left lens system channel 48L is portrayed in the optical system for reasons of simplifying the representation.

(11) FIG. 4 shows a corresponding representation of an optical system 20 according to an exemplary embodiment, wherein the right lens system channel 48R is represented in this representation.

(12) FIG. 3 shows the beam path of beams of light that enter the left lens system channel; correspondingly, FIG. 4 shows the beam path of beams of light that enter the right lens system channel 48R. The light beams that are imaged in the left lens system channel originate from a field of view of the left channel 54L; the light beams that are imaged in the right lens system channel 48R originate from a field of view of the right channel 54R.

(13) FIG. 3 shows an example of a light beam 56 that enters the optical system 20 at a wide angle relative to the optical axis 22. It enters into a region of the second prism 34 that will also be termed the “B-down region”. This B-down region 58 is typically not used by beams of light that are imaged in the left lens system channel 48L. The light beams that enter the right lens system channel (see FIG. 4) are contrastingly reflected in the B-down region 58 of the reflection side 42 of the second prism 34. It can accordingly happen that the light beam 56 which is reflected in the B-down region 58 of the second prism 34 enters the right lens system channel 48R and generates a ghost image there.

(14) In order to inter alia suppress or completely eliminate this phenomenon, the optical system 20 is configured such that the first entrance side 36 of the first prism 32 and the reflection side 42 of the second prism 34 enclose an angle α that is greater than the total reflection angle θ.sub.C of the second prism 34.

(15) The total reflection angle θ.sub.C is calculated using the known formula (1) as set forth above;
Θ.sub.C=arcsin(n1/n2)  (1)

(16) where n1=1 stands for air, and n2>1 is the refraction index of the material of the second prism 34.

(17) The first and the second prism 32, 34 can be produced from the same or identical material. At least materials with at least approximately the same refraction index can be used for the two prisms 32, 34. For example, the two prisms 32, 34 can be made of the same glass.

(18) The refraction index of the material is the refraction index that is used in Snell's law of refraction. It is therefore not the complex refraction index.

(19) The optical system 20 is configured such that the light beams entering the optical system 20 from a field of view 54L, 54R contact the reflection side 42 of the second prism 34 at such an angle that is greater than the total reflection angle. It is therefore possible for the reflection side 42 of the second prism 34 to remain uncoated, i.e., not with a vapor-deposited reflective layer such as Al or Ag. It is also provided for the reflection side 42 of the second prism 34 to be provided with an anti-reflection coating as is for example known from photographic optical systems.

(20) It is furthermore provided that the optical system 20 can comprise at least one aperture 60R, 60L that borders the field of view 54L, 54R of the optical system 20. In the portrayed exemplary example, separate apertures 60L, 60R are provided for the left and the right lens system channel 48L, 48R, namely the left aperture 60L and the right aperture 60R.

(21) The angle α between the first entrance side 36 of the first prism 32 and the reflection side 42 of the second prism 34 is selected taking into account a material of the second prism 34 that establishes a refraction index n2 and hence a total reflection angle θ.sub.C, and taking into account a maximum viewing angle that is established by the field of view 54L, 54R such that total reflection occurs for all incident light beams from the field of view 54L, 54R by the reflection side 42 of the second prism 34.

(22) Conversely, this means that light beams that enter the optical system 20 from outside of the field of view 54L, 54R, such as the light beam 56 that causes a ghost image in conventional systems, are not totally reflected on the reflection side 42 of the second prism 34. Such light beams leave the optical system 20, or more precisely the reflection side 42 of the second prism 34, and are absorbed for example by a black interior of a tube accommodating the optical system 20.

(23) By optimizing the behavior between the angle of incidence controlled by the menisci or apertures 60R, 60L on the reflection side 42 of the second prism 34 for all beams that enter from within the fields of vision 54L, 54R, total reflection can be produced on the reflection side 42. For example, an angle of incidence at the first entrance side 36 of the first prism 32 must be −7.6° (the minus sign that is used means a clockwise rotation in the depiction in the figures), wherein the angle is α=36°, and S-LAH 58 is used as the material for the prisms. In such a case, all of the light beams contacting the reflection side 42 are totally reflected. A coating on this surface can be entirely dispensed with, or the surface can be provided with an anti-reflection coating.

(24) According to another exemplary embodiment, a first partial surface 62 of the reflection side 42 of the second prism 34 can be provided with a reflective layer, and a second partial surface 64 of the reflection side 42 can be uncoated, or can be provided with an anti-reflection coating. The first and the second partial surface 62, 64 can be for example portrayed in FIG. 4. Furthermore, the second partial surface 64 can correspond to the B-down region 58, for example. The first and the second partial surface 62, 64 can supplement each other, for example, to form the entire surface on the reflection side 42. This makes it possible for light beams 56 that cause ghost images in conventional systems to leave the reflection side 42 of the second prism 34 in the B-down region 58.

(25) The first and the second partial surface 62, 64 can be furthermore arranged on the reflection side 42 of the second prism 34 such that a spacing between the first entrance side 36 of the first prism 32 and the reflection side 42 of the second prism 34 is always greater in the first partial surface 62 than a corresponding spacing between the first entrance side 36 and the reflection side 42 in the second partial surface 64. In other words, the second partial surface 64 of the first entrance side 36 consistently lies closer than the first partial surface 62.

(26) Different than shown in FIG. 4, the first and the second partial surfaces 62, 64 can overlap. In one exemplary embodiment, it can be provided for incident first light beams from an object space 11 to be reflected in the first partial surface 62 of the reflection surface 42 and to be coupled into the left lens system channel 48L. Incident second light beams from the object space 11 are reflected in the second partial surface 64 of the reflection surface 42 and coupled into the right lens system channel 48R.

(27) In a method to produce an optical system 20 of a stereo video endoscope 2 with a fixed, lateral viewing direction that comprises a laterally-viewing distal optical assembly 24 and a proximal optical assembly 26, the first and the second prism 32, 34 of the deflection prism group 30 of the distal optical assembly 24 can be selected or arranged such that the first entrance side 36 of the first prism 32 and the reflection side 42 of the second prism 34 enclose an angle α that is greater than the total reflection angle θ.sub.C of the second prism 34.

(28) This selection and arrangement can comprise not only the geometric design of the first and second prism 32, 34 and their arrangement in the optical system 20, but can also the selection of the materials, or respectively glasses used to produce these prisms 32, 34 that determine the respective refraction index of the prisms 32, 34.

(29) The procedure is similar in a method for repairing a stereo video endoscope 2 with a lateral viewing direction. For example, the deflection prism group 30 of a conventional optical system 20 is replaced with a deflection prism group 30 that fulfills the aforementioned requirements. It is also possible to completely exchange the entire distal optical assembly 24, or even the optical system 20.

(30) While there has been shown and described what is considered to be preferred embodiments, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.

REFERENCE NUMBER LIST

(31) 2 Stereo video endoscope 4 Handle 6 Endoscope shaft 8 Distal tip 10 Entrance window 11 Object space 12 Distal section 14 Adjusting wheel 20 Optical system 22 Optical axis 24 Distal optical assembly 26 Proximal optical assembly 28 Entrance lens 30 Deflecting prism group 32 First prism 34 Second prism 36 First entrance side 38 First exit side 40 Second entrance side 42 Reflection side 44 Second exit side 46 Exit lens 48L Left lens system channel 48R Right lens system channel 50L Left lens group 50R Right lens group 52L Left image sensor 52L Right image sensor 54L Field of view of the left channel 54L Field of view of the right channel 56 Light beam 58 B-down region 60L Left aperture 60R Right aperture 62 First partial surface 64 Second partial surface L Direction of longitudinal extension α Angle θ.sub.C Total reflection angle