JPH02285320A - Stop device for endoscope - Google Patents

Abstract

PURPOSE:To adjust the brightness and field depth range of an observation optical system while an endoscope insert part is inserted into the somatic cavity by providing a 1st polarizing plate which is arranged at the periphery of a through hole on the optical path of an objective lens system and a 2nd polarizing plate which is arranged rotatably and relatively to the 1st polarizing plate, and changing the state of a stop. CONSTITUTION:This device is provided with the through hole 31 which is interposed in the optical path of the objective lens system atop the insert part and passes a specific quantity of light, the 1st polarizing plate 33 which is arranged at the periphery of the through hole 31, and the 2nd polarizing plate 45 which is arranged rotatably and relatively to the 1st polarizing plate 33. When the 2nd polarizing plate 45 is rotated, the polarizing direction of the 2nd polarizing plate 45 can be changed as to the polarizing direction of the 1st polarizing plate 33 to adjust the quantity of passing light. Further, when the polarizing directions of the 1st and 2nd polarizing plates 33 and 45 are 90 deg. different from each other, only the light from the through hole of a stop main body 30 can be passed and the stop diameter can be varied. Consequently, the quantity of the passing light and stop diameter can be adjusted and the brightness and field depth of an observation image is adjustable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an aperture device for an endoscope that can adjust the brightness of the field of view and the depth of field.

[Problems to be solved by conventional technology and inventions] In recent years,
By inserting a long and thin insertion section into a body cavity, organs inside the body cavity can be observed, and if necessary, in-vivo tissue can be collected using forceps inserted through the forceps channel to diagnose the affected area in detail. Medical endoscopes are widely used. Also, in the industrial field, boilers and turbines.

Industrial endoscopes that can observe and inspect the interiors of engines, chemical plants, etc. are widely used.

When observing using the above-mentioned endoscope, if there is an affected area in the axial direction m with respect to the distal end side of the insertion section, it is easier to observe using a direct-viewing endoscope. Furthermore, when observing the inner wall surface of the body cavity on the side perpendicular to the direction of insertion, it is easier to observe using a side-viewing endoscope. Additionally, you can roughly observe a large area, or
Observations can be made more easily by using endoscopes with different angles of view depending on whether a narrow area is to be observed precisely. However, endoscopes are expensive, and it is extremely uneconomical to prepare endoscopes for these various observation objects. In order to deal with this problem, Japanese Patent Application Laid-Open No. 56-85324
The publication discloses a technique for equipping a distal end optical adapter equipped with an optical system that can change the viewing angle and viewing direction at the distal end of an endoscope insertion section.

In addition, as a connection means for an object that is detachably attached to the distal end of an endoscope, there are two types: a non-rotational connection section that connects the object section while restricting rotation, and a connection section that connects the object section without restricting rotation. By providing this, it is possible to connect the objective part equipped with a rotational focus adjustment means in a non-rotation manner so that the connection part does not come loose during focus adjustment, and also to connect the objective part equipped with a rotational focus adjustment means to prevent the connection part from loosening during focus adjustment. A technique has been proposed that makes it possible to perform a rotational connection to the parts.

Incidentally, the observation optical system of an endoscope is generally provided with a field diaphragm to increase the depth of field so that a wide range can be observed even in the case of a fixed focus. This diaphragm is fixed to the endoscope 1, and the size (caliber diameter) of the diaphragm cannot be changed. With an endoscope that has a deep depth of field with such an aperture, the field of view becomes dark when observing far-point objects, and conversely, the field of view becomes too bright when observing near-point objects. Sometimes. Also,
An endoscope with a shallow depth of field without narrowing down the aperture may provide appropriate brightness when observing far-point objects, but may become too bright when observing near-point objects.

In general, the brighter the field of view, the better, and the deeper the depth of field, the easier it is to see. However, as mentioned above, in endoscopes with fixed apertures, increasing the effective diameter of the observation optical system will result in brighter images but shallower depth of field; was deeper but darker, and it was not possible to optimize both. Therefore, the depth of field, brightness, etc. of the optical system can be changed by attaching a tip optical adapter with a different aperture size to the tip of the endoscope. However, the endoscope insertion part is
After it has been inserted into the body cavity, it is necessary to attach or remove the tip optical adapter without taking out the insertion part from the body cavity, which is not only extremely complicated, but also There is a problem in that it may cause pain to the bacteria to be tested.

The present invention has been made in view of the above problems.C. The state of the endoscope insertion portion inserted into the body cavity is determined by making the state of the diaphragm variable. 11! 'An object of the present invention is to provide an endoscope aperture device that can adjust the bright optical system of a dormitory optical system and the depth of field i range.

[Means J3 and Effects for Solving the Problems J The endoscope diaphragm device according to the present invention is a transparent device that is interposed on the optical path of the objective lens system provided at the distal end of the insertion section and that allows a predetermined amount of light to pass through. It is equipped with a hole, a polarizing plate 'i51 disposed around the through hole, and a second polarizing plate disposed rotatably relative to the first polarizing plate. By rotating the second polarizing plate (V), the polarization direction of the second polarizing plate can be changed with respect to the polarization direction of the first polarizing plate, and the passing light m can be adjusted. . Further, by making the polarization directions of the first and second polarizing plates different from each other by 90 degrees, it is possible to allow light to pass only through the through hole of the diaphragm body, and the diameter of the diaphragm can be changed.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

1 to 5 relate to a first actual droplet example of the present invention, FIG. 1 is a side view of the distal end of the endoscope, and FIG. 2 shows the mounting neck of the endoscope according to the present invention. J1 light diagram, Figures 3(a) and (b) are cross-sectional views taken along line A-A and line B-B in Figure 2, respectively;
FIG. 4 is a schematic configuration diagram of the endoscope apparatus, and FIG. 5 is an explanatory diagram for explaining the operation of the embodiment.

In FIG. 4, the inner JJA restraining device 1 is elongated and has, for example, a large-diameter operating portion 3 connected to the rear end of an insertion portion 2 that is flexible. A connector receiver 4 is provided at the rear end of the operating section 3, and the operating section 3, a light source device, and a video processor are connected to each other via a cable 6 having a connector 5 that can be viewed from the connector receiver 1. A control unit with a built-in unit (not shown)
The device 7 is connected. Furthermore, a color CRT monitor 8 as a display means is connected to this control device 7.

At the distal end side of the insertion section 2, a hard distal end section 9 and a bendable bending section 10 adjacent to the rear of the distal end section 9 are provided. This bending section 10 can be bent vertically and horizontally by rotating an operating knob 11 installed on the operating section 3.

The distal end portion 9 includes a substantially cylindrical distal end main body 12, and a cover 13 is attached to the distal end side of the distal end main body 12. At the rear end side of the cover 13, the tip body 12 is covered with an exterior rubber 14.

In addition, a forceps channel communication hole 15, an observation communication hole 16, and an illumination communication hole (not shown) are formed on the side surface of the distal end side of the cover 13, and are formed in the distal end portion 9, respectively. The forceps channel is communicated with the through hole 17 for the channel, the through hole 18 for observation, and the through hole for illumination (not shown). The forceps channel through hole 17 communicates with an insertion port 19 provided in the operating section 3, so that various treatments can be performed via a surgical instrument inserted through the insertion port 19. It has become.

Furthermore, an objective lens system 21 composed of a plurality of lenses 25.20a to 20f, which are examples of optical members, is disposed within the observation hole 18. This objective lens system 21
An image probe 22 is disposed solidly on the rear end side, so that the object image formed by the objective lens system 21 is formed on this solid-state image sensor 22. and,
The image signal photoelectrically converted by the solid-state Iυ image sensor 22 is input to the control device 7 via a signal line (not shown).
Furthermore, this control 61] the image signal processed by the device 7 is CR
The image of the subject is output to the T monitor 8 and displayed on the CRT monitor 8.

To explain in detail the fixed state of the objective lens system 21, a lens frame 23 formed longer than the thickness of the cover 13 is inserted into the observation through-hole communication hole 16, and the lens frame 23 is inserted into the observation through-hole 18. It is fixed by a screw (not shown) formed around the periphery. The inner periphery on the front end side of this lens frame 23 is set as a mounting section 24, and the front lens 25 of the objective lens system 21 is attached to this mounting section 24, and the rear end side surface of this front lens 25 is connected to the lens. It is in contact with an arrangement portion 24 formed halfway along the inner circumference of the frame 23 .

On the other hand, for example, a filter 26 is provided on the rear end side of the arrangement portion 24.
This filter 26 is in contact with the fixing member 2 fitted to the inner periphery of the lens frame 23.
It is fixed at 7. Further, another lens frame 28 is fitted to the inner periphery of this fixed member 27, and a plurality of lenses 20a, which are an example of optical members, are attached to the inner periphery of this lens frame 28.
f is arranged. In addition, these lenses 25.20
A light shielding agent is applied to the outer peripheries of a to 20f.

A diaphragm device 29 is provided between the lens 20a and the lens 20b. In FIGS. 2 and 3, the diaphragm device 29
The calibration body 30 is formed into a disk shape, and is arranged so that the optical axis of the objective lens system 21 and the ring center are aligned.

The outer peripheral surface of this calibration body 30 is inserted into the outer cover 42. The outer diameter of the outer cover 42 matches the diameter of the optical path formed by the lens frame 28, and the outer periphery of the outer cover 42 is in contact with the inner circumferential surface of the lens frame 28 except for a part, and the outer periphery of the outer cover 42 is in contact with the inner circumferential surface of the lens frame 28. No light passes through the outside of the surface. A through hole 31 having a predetermined diameter is installed in the center of the calibration body 30 with its center aligned with the axis of the calibration body 30, and a plurality of openings 32 are arranged in a circular manner around the through hole 31. A polarizing plate 33 is disposed in this opening 32 . Note that the diagonally shaded direction in FIG. 3(a) indicates the direction of polarization by the polarizing plate 33.

A solar cell 34 is formed in the area around the through hole 31 of the main body 30 and where the polarizing plate 33 is not provided.

Further, a hole 35 is provided in a part of the inner peripheral surface of the lens frame 28 to which the calibration body 30 is attached, and a stator 37 of an electrostatic motor 36 is disposed in this hole 35. The electrostatic motor 36 is supplied with a power supply voltage from the solar cell 34 via a switch 40 via wiring 39 .

A disk-shaped diaphragm adjustment section 41 is provided opposite the calibration body 30. The calibration adjustment section 41 has an outer cover 42 whose inner diameter is the same as that of the calibration body 30 and whose inner diameter is the same as that of the calibration body 30.
and an inner cover 4 whose outer diameter is the same as that of the through hole 31.
3 and has a gear 44 between it. An inner cover 43 is fitted onto the inner circumferential surface of the main body 30 that forms the through hole 31, and the inner diameter of the inner cover 43 determines the minimum diameter of the constriction ring 29. The gear 44 has an axial center opening with a predetermined diameter, and is rotatably set so as to face the polarizing plate 33 of the calibration body 30. Adjacent gears 44 meet each other so that all gears 44 rotate simultaneously in forward and reverse directions at the same speed. Each gear 44011180 is provided with a polarizing plate 45, and each polarizing plate 45 has the same polarization direction, for example, as shown by the diagonal line J in FIG. 3(b). A gear 44a disposed near the opening of the outer cover 42 has a polarizing plate 45a disposed in the opening and meshes with a gear 46. gear 4
6 has an opening with a predetermined diameter at its axial center, and is rotatably disposed within the hole 35 . The rotor 38 of the electrostatic motor 36 is attached to the opening of the gear 46 . As a result, rotor 3
8 is rotated by all gears 44 through gear 46 and gear 44a.
transmitted to.

Next, the operation of the endoscope comparison device configured as described above will be explained with reference to FIG. Note that in FIG. 5, diagonal lines indicate that light is blocked.

The light emitted from the light source device 7 is irradiated onto the test site via the cable 6 through the illumination through-hole and the illumination through-hole communication hole provided in the distal end portion 9 of the insertion section 2 . The return light from the test site due to this illumination light is transmitted to the front lens 2 of the objective lens system 21.
5. Filter 26, diaphragm device 29 and lenses 20a to 2
An image is formed on the solid-state image sensor 22 via 0f. The output signal of the solid-state ms element 22 is given to the control device 7, and the control device 7 processes the video signal. The video signal generated by this control device 7 is input to the CRT monitor 8, and the examined part is displayed on both sides.

It is now assumed that the polarizing plates 45 and 45a have the polarization direction shown by the diagonal line in FIG. 3(b). In this case, the polarizing direction of the polarizing plate 45.45a is different from the polarizing direction of each opposing polarizing plate 33 by 901ff, and the polarizing plate 33.4
No light can pass through 5.45a.

Therefore, as shown in FIG. 5(a), the aperture diameter of the aperture device 29 is the minimum diameter determined by the inner diameter of the inner cover 43.

In this case, the deepest subject! ? 11 depth can be obtained. Furthermore, even when the reflected light i1 from the test site is large, the polarization direction of the polarizing plate 45.45a is changed as shown in FIG.
If it is as shown in a), the amount of light passing through the objective lens system 21 can be minimized, and the observed image of the region to be examined can be made easy to see.

On the other hand, when the area to be examined is relatively dark, the operator turns on the switch 40. Then, electrostatic motor 3
6, a current is supplied from the solar cell 34 and the rotor 38 starts rotating. The rotation of the rotor 38 is transmitted to all the gears 44a, 44 via the gear 46.

44 is the same 3i in forward and reverse directions! Rotate by i degrees. As a result, the polarizing plates 45a disposed in the openings of the gears 44a, 44
, 456 rotations, and the difference between the polarization direction of the polarizing plates 45a and 45 and the polarizing direction of the opposing polarizing plate 33 is smaller than 90 degrees. As a result, the amount of light passing through the aperture device 29 increases.

Further, the electrostatic eater 36 rotates to polarize the polarizing plate 45a.

When the polarization direction of 45 matches the polarization direction of polarizing plate 33,
The switch 40 is turned off to stop the electrostatic motor 37 from rotating. In this case, as shown in FIG. 5(b), the polarizing plates 33, 45a and 45 allow the most light to pass through, and the light a passing through the aperture device 29 becomes the maximum, making it possible to observe the brightest object N1. You can get the image.

As described above, in this embodiment, the electrostatic motor 36 is used to rotate the polarizing plates 45a and 45 to make it possible to adjust the aperture diameter and the passing light a. The brightness and depth of field of the observed image can be adjusted depending on the state. Furthermore, polarizing plates 33.45a and 4 facing each other
By adjusting the polarization direction of 5, the number of light layers is increased or decreased, and the structure is simpler than that of a general blade diaphragm. Further, since the polarizing plates 45a and 450 are rotated using the electrostatic motor 36, which can be configured extremely small, the diameter of the insertion portion distal end portion 9 can be reduced.

Note that the power source for the electrostatic motor 36 does not need to be the solar cell 34, and the power source may be inside the operation unit 3, inside the connector 5,
It may be configured as either control@@7 or the like.

FIG. 6 is an explanatory diagram showing a diaphragm device for an endoscope according to a second embodiment of the present invention.

The second embodiment is an example in which an electrostatic motor for rotating a polarizing plate is provided for every two gears. In other words, gears 48a and 48b having an opening with a predetermined diameter in the center are arranged around the inner cover (not shown) of the diaphragm adjustment section 47 as shown in the calibration body 3 of the first embodiment.
It is rotatably provided opposite to each polarizing plate 33 of 0. Polarizing plates 50 are disposed in the openings of the gears 48a and 48b, and the two gears 48a are adjacent to each other.

48b meshes with the gear 50. The gears 5G each have an electrostatic Tanabata rotor (not shown) attached thereto, and are rotated by rotation of the rotor. Note that each electrostatic motor rotates synchronously, and this rotation causes gears 48a, 4
8b rotates at the same speed in forward and reverse directions.

It is clear that in the embodiment configured in this way, the same functions and effects as in the first embodiment can be obtained. In this embodiment, the electrostatic motor has two gears 48
a, 48b, and the driving force of the electrostatic motor can be reduced.

Note that the electrostatic motor can also be installed in the dead space on the back side of the solar cell 34 in FIG. 3, and in this case, the insertion portion tip 9 can be made even smaller in diameter .

FIG. 7 is an explanatory diagram showing a diaphragm device for an endoscope according to a third embodiment of the present invention.

The frame 51 is placed in contact with the inner peripheral surface of the lens frame 28. On the front end side of the frame 51, a disc-shaped calibration body 53 having a polarizing section 52 around its periphery is fixed to the inner periphery of the frame 51. Further, a disk-shaped aperture adjustment section 54 is rotatably provided within the frame 51. The calibration adjustment unit 54 has an opening 55 with a predetermined diameter whose center coincides with the axis of the lens frame 28.
A polarizing section 56 is provided around the polarizing section 56 to face the polarizing section 52 of the main body 53. An electrostatic motor 57 is disposed between the calibration body 53 and the aperture adjustment section 54. A ring-shaped electrostatic motor 57 has a stator 58 fixed to the calibration body 53Il within the frame 51, and a rotor 5 that rotates in opposition to the stator 58.
9 is provided. The end face of the rotor 59 is I! The diaphragm adjustment section 54 is attached to one surface of the second adjustment section 54 on the side of the calibration body 53, and rotates when the rotor 59 rotates. Note that the electrostatic motor 57 is rotated by being supplied with voltage from a power source (not shown).

In this embodiment, when a switch (not shown) is operated to supply voltage to the electrostatic motor 57 and drive it, the calibration adjustment section 5
4 rotates, and the direction of polarization by the polarizer 54 changes. The polarization direction of the polarizing section 52 provided around the calibration body 53 is constant, and by appropriately setting the rotation angle of the diaphragm adjustment section 540, it is possible to adjust the maximum amount of light passing through and the diameter of the diaphragm.

It is clear that the same effects as in the first embodiment can be obtained in this embodiment as well. Furthermore, the calibration body 53 and the diaphragm adjustment section 54 both have an extremely simple structure consisting of a single polarizing plate. In addition, in this example,
The minimum diameter of the diaphragm is the diameter of the opening 55 of the adjustment section 54, and the maximum diameter is the inner diameter of the electrostatic mortar 957. Note that the end portion of the frame 51 may be embedded in the peripheral surface of the lens frame 28.

FIG. 8 is an explanatory diagram showing a diaphragm device for an endoscope according to a fourth embodiment of the present invention.

This embodiment is an example in which the electrostatic motors 68 and 69 have a sealed structure. The frame 61 is disposed so as to be in contact with the inner circumferential surface of the lens frame 28 or with its end portion embedded. On the front end side of the frame 61, a disc-shaped calibration body 63 having a polarizing section 62 around its periphery is fixed to the inner periphery of the frame 61. Further, a disk-shaped aperture adjustment section 64 is rotatably provided within the frame 61. The aperture adjustment section 64 has an aperture 65 with a predetermined diameter whose center coincides with the axis of the lens frame 28, and a polarizing section 6 around this aperture 65.
6 is provided facing the polarizing section 62 of the main body 63. A cover 6 that closes the opening of the frame 61 is provided on the rear end side of the frame 61.
1 is provided. An electrostatic motor b8 is disposed between the calibration main body 63 and the calibration adjustment section 64, and an electrostatic motor 69 is disposed between the calibration adjustment section 64 and the cover 67.

The ring-shaped electrostatic motor 68 has a stator 70 on the calibration body 63 side.
is fixed, and a rotor 11 that rotates opposite the stator 70 is provided. The end of the rotor 71 is the aperture adjustment section 6
It is attached to the front end surface of 4. On the other hand, in the ring-shaped electrostatic motor 69, a stator 72 is fixed to the cover 67 side, and a rotor 73 that rotates opposite to the stator 72 is attached to the calibration adjustment section 69.
It is attached to the rear end surface of 4. Electrostatic motor 68.69
The rotors 71 and 73 rotate at the same speed in synchronization, and this rotation causes the diaphragm adjustment section 84 to rotate.

An open lower lower portion 4 is provided in a portion near the circumferential surface of the calibration body 63, and a signal line 76 for supplying voltage to the electrostatic motor 68 is inserted through the open lower lower portion 4. Further, an open lower lower 5 is provided in a part near the circumferential surface of the cover 67, and during this time, the lower 5 is connected to a signal l117 that supplies voltage to the electrostatic motor 69.
7 is inserted.

Note that the opening lower portion 4.75 is reliably closed, and the electrostatic motors 68.69 are in a sealed state.

It is clear that this embodiment also has the same functions and effects as the third embodiment. In this embodiment, since the electrostatic motors 68 and 69 are sealed, they are not affected by moisture and can operate stably.

Furthermore, since the electrostatic motors 68 and 69 are disposed on both sides of the diaphragm adjustment section 64, the diaphragm adjustment section 64 can be driven with a relatively large rotational force. In this embodiment, the minimum diameter of the comparison is the diameter of the opening 65 of the diaphragm adjustment section 64, and the maximum diameter is the inner diameter of the electrostatic motor 68, 69.

FIG. 9 is an explanatory diagram showing a diaphragm device for an endoscope according to a fifth embodiment of the present invention.

The frame 78 is disposed so as to be in contact with or embedded in the inner peripheral surface of the lens frame 28 . On the '#j@ side of the frame 18, there is a disc-shaped calibration body 80 with a polarizing section 79 around the frame 78.
is fixed to the inner circumference of the A disc-shaped diaphragm adjustment part 81 is rotatably provided on the inner periphery of the narrow diameter part 85 of the frame 78.

The aperture adjustment section 81 has an opening 82 of a predetermined diameter whose center coincides with the axis of the lens frame 28, and a polarizing section 83 is provided around this opening 82, facing the polarizing section 79 of the calibration body 80. It is being A cover 84 that closes the opening of the frame 78 is provided on the rear end side of the frame 78 . Electrostatic motors 86 and 87 are disposed on both sides of the aperture adjustment section 81 of the narrow diameter section 85 of the frame 78.

The ring-shaped electrostatic motor 86 has a stator 89 fixed to the rear end surface of the large diameter portion 88 of the frame 78, and a rotor 90 that rotates in opposition to the stator 89. The rotor 90 is mounted on the #J end face of the diaphragm adjustment section 81. On the other hand, the ring-shaped electrostatic motor 87 has a stator 91 fixed to the cover 84 side, and a rotor 9 that rotates opposite to the stator 91.
2 is attached to the rear end surface of the aperture adjustment section 81. The rotors 90, 92 of the electrostatic motors 86, 87 rotate in synchronization at the same speed, and this rotation causes the diaphragm adjustment section 81 to rotate. Incidentally, the electrostatic motors 86 and 87 are supplied with power supply voltage from a power supply (not shown).

It is clear that this embodiment also has the same functions and effects as the fourth embodiment. In this embodiment, the stator 89 of the electrostatic motor 86 is fixed to the rear end surface of the large diameter portion 88, so that the electrostatic motor 86 can be securely attached. Furthermore, in this embodiment, light can pass through substantially the entire area of the calibration body 80.

Note that the present invention is not limited to the above-mentioned embodiments. For example, although the explanation has been given using an electronic endoscope having a solid-state lithium image element, the present invention is applicable to an optical endoscope having an image guide. It is clear that it may be applied.

[Effects of the Invention] As explained above, according to the present invention, by rotating the second polarizing plate, the passing light a and the aperture diameter can be adjusted, so that the brightness of the observed image and the subject can be adjusted. The depth of field can be adjusted.

[Brief explanation of drawings]

1 to 5 relate to a first embodiment of the present invention, FIG. 1 is a side view of the distal end of the endoscope, and FIG. 2 is a diaphragm device of the endoscope according to the present invention. 3(a) and 3(b) are respectively cut along lines A-A and B-B in FIG. 2, respectively. FIG. 5 is an explanatory diagram for explaining the operation of the embodiment, FIG. 6 is an explanatory diagram showing a diaphragm device for an endoscope according to a second embodiment of the present invention, and FIG. An explanatory diagram showing an endoscope diaphragm device according to an embodiment, FIG. 8 is an explanatory diagram showing an endoscope diaphragm device according to a fourth embodiment of the present invention, and FIG. 9 is an explanatory diagram showing a diaphragm device according to a fourth embodiment of the present invention. FIG. 2 is an explanatory diagram showing a diaphragm device for an endoscope according to the present invention. 21...Objective lens system, 25.20a-20f...
Lens, 28...Lens frame, 29...Aperture device agent Patent attorney Jun Ito Go to Figure 3, Figure 4, Figure 5, Figure 6, Figure 7!ゝ＼

Claims (1)

[Claims] a through hole that is interposed on the optical path of an objective lens system provided at the tip of the insertion section and allows a predetermined amount of light to pass through; a first polarizing plate disposed around the through hole; and a first polarizing plate disposed around the through hole; A diaphragm device for an endoscope, comprising a second polarizing plate rotatably arranged relative to the plate.