JPS61186919A - Image pickup device for endoscope - Google Patents

Abstract

PURPOSE:To prevent the generation of a moire stripe by placing a titled device so that when a television camera has been installed to an adaptor, a separating direction of a double refraction by two filters contains horizontal and/or vertical components to an image pickup element in the television camera. CONSTITUTION:A photographic lens 21 and a crystal filter 22 consisting of three pieces of crystal plates are incorporated in an adaptor 20, and an image pickup element 24 and one piece of crystal filter 25 which has been placed in front of the image pickup element 24 are provided on a television camera 23. In this case, the crystal filter 22 is constituted of three pieces of crystal plates 22a, 22b and 22c in order from an incident side, and a dislocation direction and a dislocation quantity of a beam caused by a double refraction of each crystal plate 22a, 22b and 22c, and the crystal filter 25 become a direction indicated with an arrow and quantities indicated with P1, P2, P3 and P4. Accordingly, when P1, P2, P3 and P4 are selected so as to satisfy P1=P/2, P2<P1, P2<P3+P4, and P3+P4 (P is a width of one picture element in the horizontal direction of the image pickup element 24), a moire stripe generated by a picture element of the image pickup element 24 and an image guide of a fiber scope 9 is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an endoscope imaging device that can be used for both fiberscopes and rigid scopes.

Conventionally, when images from an endoscope are observed through a television monitor, in order to use the same television camera for a fiberscope and a rigid scope, as shown in Figure 2, it is necessary to A television camera is attached to the eyepiece of the endoscope via a mirror adapter. That is, in FIG. 2(A), l is a rigid scope and 2 is a rigid ml.
This is an adapter for a rigid scope attached to the eyepiece of the camera, and a photographing lens 3 is incorporated therein. Reference numeral 4 denotes a television camera attached to the rear of the adapter 2, and includes an image receiving element 5 and a crystal filter 6 disposed in front of the image pickup element 5. Reference numeral 7 denotes a camera control unit that displays an image observed by the rigid mirror 1 on the screen of a television monitor 8 based on a signal from the image pickup device 5.

In this case, the occurrence of moire fringes is removed by a crystal filter 6 within the television camera 4. Further, in FIG. 2(B), 9 is a fiberscope, 10 is a fiberscope adapter attached to the eyepiece of the fiberscope 9, and a photographing lens 11 and, for example, a
A phase filter 12 as shown in No. 417 is incorporated. At the rear of this adapter 10 is a
A television camera 4 is also attached. In this case, the occurrence of moire fringes is removed by a phase filter 12 within the adapter 10. However, since the effect of the phase filter on low frequencies is too strong, there is a drawback that the resolution decreases at the same time as moiré fringes are removed.

In view of the above points, it is an object of the present invention to provide an endoscope imaging device that can be used in fiberscopes and rigid scopes and can prevent the occurrence of moiré fringes without reducing resolution. The purpose is

The purpose of this is to have an adapter that can be attached to the eyepiece of an endoscope, and a built-in adapter that can be attached to the rear of the 8-unit adapter, and a built-in image sensor. In an endoscope imaging device, the endoscope image pickup device is composed of a television camera and an image pickup device in the television camera superimposes the image taken by the endoscope through the photographing lens of the adapter. First and second filters made of a birefringent substance are built-in, and the first and second filters cause birefringence due to the two filters when the TV camera is attached to the adapter. The present invention is solved by an imaging device for an endoscope, which is arranged in an imaging optical path so that the separation direction includes a component horizontal and/or perpendicular to an imaging element in a television camera. .

The present invention will be explained below based on the embodiments shown in the drawings.
In FIG. 1, reference numeral 20 denotes an adapter attached to the eyepiece of the fiberscope 9, into which one closest lens 21 and a crystal filter 22 consisting of three crystal plates are incorporated. 2
3 is a television camera attached to the rear of the adapter 20,
It includes an image sensor 24 and a crystal filter 25 disposed in front of the image sensor 24. Here, the crystal filter 22 is composed of three crystal plates 22a, 22b, and 22c in order from the incident side as shown in FIG.
The direction and amount of deviation of light rays due to birefringence (deviation of extraordinary light with respect to ordinary light) in 5 are shown in Figure 4 (Δ), (B), and (C).
, the direction indicated by the arrow in (D) and P, ,P2. Pj, P
, where each crystal plate 22a, 22b, 2
2c and the crystal filter 25 are shown in FIGS. 5(A), (B), and (C), respectively, when viewed in a cross section perpendicular to the optical axis.
) and (D). Incidentally, in FIG. 5, the bar attached to the black circle indicating the light beam indicates the polarization direction of the light beam. Therefore P+
.

If the crystal filters 22 and 2 are selected so as to satisfy
Since the overall MTF of 5 is as shown in FIG. 6, moiré fringes generated by the pixels of the image pickup device 24 and the image guide of the fiberscope 9 are removed. Furthermore, the fourth
In Figure (E), the hunting indicates the different color portions of the color mosaic filter, and the period of the color mosaic in the horizontal direction is 2P. In practical terms, equation (11, +31 is the following equation (4).

There is no problem in relaxing the conditions as in (5).

2+31. +51 is a conditional expression for removing moire fringes caused by the mosaic filter, and 2f11. +4
1 is a conditional expression for removing moiré fringes caused by one pitch of pixels of an image sensor. If there is no color mosaic filter, P may be replaced with -P in (2) to (5), and if not replaced, use equation (3).

(5) is a conditional expression for removing moiré fringes caused by the nibitch period of pixels in the horizontal direction.

As shown in FIG. 4, the directions of birefringence of the crystal plate 22C and the crystal filter 25 are the same, and the sum of their deviations satisfies equation (3) or (5). Therefore, the resolution of both rigid and fiberscopes does not deteriorate significantly, and Moiré fringes can be removed as necessary.

Also, instead of the formula (11, +31), the following formula, that is, P,
= P -----+61P3 0 Pg = P -----fi1 may be used, and the following expression, i.e., may be used in place of the formula (41, (51), and the value of P4 is It is determined by the combination of , and experimentally it is determined by the combination of .

Even if the directions of birefringence of the crystal plate 22c and the crystal filter 25 are opposite to each other, the same effect can be obtained as long as formula (3) or (5) is satisfied. Furthermore, when the direction of the crystal axis relative to the surface of the crystal is 45°, the amount of single refraction is maximum, and the amount of birefringence is approximately 5.8 for a thickness of 1 inch of crystal.
becomes μ.

Furthermore, it may be a ps-o, in which case the crystal filter 22 is connected to the crystal plate 22 as shown in FIG. 7(A).
a and 22b, or the crystal plate 22b of the crystal filter 22 may be arranged in front of the crystal filter 25 in the television camera 23 (see FIG. 7(B)).
reference). Furthermore, the same effect can be obtained by dividing the crystal plate 22a in FIG. 7(B) into two parts 22a1.22az and providing the crystal plate 22a2 inside the television camera 23 (see FIG. 7(C)). ), in this case, if the amount of birefringence due to the crystal plate 22a1 is PIA and the amount of birefringence due to the crystal plate 22a2 is PlB, each birefringence I P + A and pH are selected so as to satisfy P+a+P+s=P+, and the birefringence I P + A and pH are The directions of refraction are the same, and according to equation (1), Ol is satisfied.

Next, in order to align the crystal plate 22c and the crystal filter 25 in the same direction or in opposite directions, it is sufficient to use a bayonet mount for the attachment part of the adapter 20 and the television camera 23, but if the television camera 23 is attached to a screw mount or the like, If a mounting part without directionality is provided, the crystal filter 25
After attaching the TV camera 23 equipped with the above to the adapter 20 having the crystal plate 22c, the crystal filter 22 including the crystal plate 22c may be rotated around the optical axis from the outside.A specific device for this is described below. Explain.

In FIG. 8, reference numeral 30 denotes an adapter body that supports a shadow lens 21 and a crystal filter 22 in the center, and a screw mount portion 31 thereof is rotatably held by a ring 32 with respect to the adapter body. Reference numeral 33 denotes a ring member that is fixedly attached to the outer circumference of the screw mount portion 31 and has internal teeth 33a formed all around the inner circumferential surface, and a ring member that moves radially from the outside to the internal teeth 33a. Rotation can be prevented by engagement of the locking pawl 34a attached to the movable operating member 34 (FIGS. 8(B) and 8(C)).
reference). The operating member 34 is guided by a washer 35 screwed to the adapter body 30 as shown in FIG. It is elastically pressed in the direction of engagement with the internal teeth of the member 33. According to this configuration,
After attaching the television camera 23 to the adapter 30 using a screw mount, press down the operating member 34 with your finger, rotate the adapter body 30, and release your finger from the operating member 34 at an appropriate position to open the crystal plate 22c of the crystal filter 22. The direction of birefringence can be set to be the same or opposite to the direction of birefringence of the crystal filter 25 in the television camera 23.

FIG. 9 shows another system, in which 40 is a first main body portion 40a which supports a photographing lens 41 in the center and which is configured as an adapter that can also be used for cine photography or still photography. , a second body part 40b attached to the second body part 40a by a suitable method and provided with a screw mount for the television camera 23; The ring 4 is arranged so that the lens barrel part 42 supporting the crystal filter 22 does not move in the optical axis direction but can rotate around the optical axis.
It is held by 3. Reference numeral 44 denotes an elastic body incorporated between the outer peripheral surface of the lens barrel portion 42 and the inner peripheral surface of the second main body portion 40b of the adapter body;
Rotation relative to Qb is prevented with a light force. Reference numeral 45 denotes a cut groove provided on the end face of the lens barrel portion 42 facing the second main body portion 40a, and is formed so that, for example, a coin X or the like can be engaged therein. According to this configuration, the television camera 2 is attached to the second body portion 40b of the adapter by the screw mount.
3, fit a coin or the like into the cut groove 45 of the lens barrel portion 42 and move the lens barrel portion 42 against the second body portion 40b against the rotation blocking force of the elastic body 44. By rotating, the direction of birefringence of the crystal 4122c of the crystal filter 22 can be set to the same direction or the opposite direction to the direction of birefringence of the crystal filter 25 in the television camera 23, and at that position, the elastic body 4
4, it is lightly locked.

FIG. 10 shows a structure of a crystal filter different from that in FIG. 3, in which a crystal plate 51 is provided in place of the crystal plate 22a in FIG. This crystal plate 51 has a direction and a deviation amount P shown by the arrow in FIG. 11(A).

It is formed so as to produce birefringence of , and the deviation amount Ps
As shown in FIG. 11(B), Ps −Q is calculated for the size Q of one pixel in the vertical direction of the image sensor 24.
--- Moiré fringes can be removed by selecting so as to satisfy (1), ). In practice, it is sufficient to satisfy the following, and Q may be replaced with -Q. Here, the deviation of the light beam after passing through the crystal +ffE51.22b, 22c and the crystal filter 25 is as shown in FIG. 12 when viewed in a cross section perpendicular to the optical axis. In Fig. 11 (B), the hunting indicates the different color parts of the color mosaic filter, and the period of the color mosaic in the vertical direction is 2Q. Therefore, equations (11) and (12) are the color mosaic filter. This is a conditional expression for removing moiré fringes in the vertical period of the filter.

FIG. 13 shows the configuration of a crystal filter in which a quarter-wave plate 52 is provided instead of the crystal plate 22b in FIG. 3 or 10, and the first crystal plate is as shown in FIG. 3. In the case of the crystal plate 22a, the deviation of the light beam is shown in Fig. 14 (A).
If the first crystal plate is the crystal plate 51 as shown in Fig. 1O, the deviation of the light beam will be as shown in Fig. 14CB)
become that way.

FIG. 15 shows a three-piece crystal filter 6 equipped with crystal plates 61 and 62 in place of the crystal Jff 22a and 22c in FIG.
3 is a configuration example in which a four-piece crystal filter 64 is provided instead of the crystal filter 25, and here the crystal filter 64 is
are in turn a quarter-wave plate or a quartz plate 65. which produces birefringence in the 45° direction, such as the quartz plate 22b in FIG. Crystal plate 6
6. Consists of 67 and 68. The crystal plate 67 is a quarter-wave plate, and each crystal plate 61, 62, 66, 68 has a direction and a deviation amount P4 shown by arrows in FIGS. 16(A), CB), (C), and (D). ．． It is formed to produce the birefringence of Pt, Ps, and Pq. Each deviation Ips.

Moiré fringes can be removed by selecting P6, Pt, and Pg so as to satisfy P & -P q "' Q Ps" P p, -Q (13).

In practice, it is sufficient to satisfy the following, and the deviation of the light beam after passing through the crystal filter 63 is as shown in FIG. 17(A), and the deviation of the light beam after passing through the crystal filter 64 is as shown in FIG. 17(B). It becomes like this.

In the configuration example shown in FIG. 15, a color mosaic filter may be disposed in front of the image sensor 24, and the period of the color mosaic in the horizontal direction is Pc, and the period of the color mosaic in the vertical direction is Qc.
Then, the amount of deviation of each crystal plate P1Pt , Ps , P
q as Pb" Pc P't"' Qc Pg = P P? =-Q --
-- If the selection satisfies (15), moire fringes caused by the pixels of the image sensor and the color mosaic filter are removed. Practically speaking, it is sufficient to satisfy the following.In addition, when applying the configuration example shown in FIG. 15 to an image pickup tube, as shown in FIG. Expression (
13), (14), (15), and (16) may be satisfied.Also, in other configuration examples, the horizontal period of the color mosaic filter is replaced with the period of the stripe filter, and the vertical direction It can also be applied to a bottle picture tube by replacing the pixel pitch with the scanning line interval.

It goes without saying that similar effects can be obtained by using a birefringent material, such as calcite, in place of quartz in all of the above configuration examples. In the configuration example, the phase filter 12 shown in FIG. 2 CB) may be inserted into the optical path.

FIG. 19 shows a configuration example in which a crystal plate 81.82 is provided in place of the crystal plate 61.62 in FIG. and deviation amount P
It is formed to produce a birefringence of 11+P11, and the deviation NP1. +P11 as shown in FIG. 20(C), P with respect to the distance C between the images of the fiber 83 of the fiberscope on the surface of the image sensor. If the selection is made so as to satisfy =P++=C---(17), moiré fringes caused by the fiber of the fiberscope and the image sensor can be removed. In practice, it is sufficient to satisfy the following. Here, the deviation of the light ray after passing through the crystal plate 81, 52, 82 is as shown in FIG. 21 (A), and the deviation of the light ray after passing through the crystal filter 64 is Figure (B
).

As described above, according to the present invention, there is provided an adapter that can be attached to the eyepiece of an endoscope and that incorporates a photographic lens;
It consists of a television camera that can be attached to the rear of the adapter and has a built-in image sensor, and the image taken by the endoscope is transferred to the image sensor in the television camera through the adapter lens. In the jlA imaging device for an endoscope, the adapter and the television camera each include first and second filters made of a birefringent material, and the first and second filters are connected to the television. When the camera is attached to the adapter, the birefringence separation direction by the two filters is horizontal and /
Or, since it is arranged in the imaging optical path so as to include a vertical component, it is possible to prevent the occurrence of moiré fringes without causing a decrease in resolution unlike in the case of a phase filter, and it is also possible to prevent the occurrence of moiré fringes. A highly effective endoscopic field imaging device can be provided that can be used with fiberscopes and rigid scopes.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of an endoscopic imaging device according to the present invention, FIG. 2 is a diagram showing an example of a conventional endoscopic imaging device, and FIG. 3 is a diagram similar to that of FIG. 1. 4 is a diagram showing the configuration of the crystal filter in the example. FIG. 4 is a diagram showing the state of birefringence of each crystal plate and crystal filter in FIG. 3, and the image plane of the image sensor.
The figure shows the deviation of light rays due to the crystal filter in Figure 3,
FIG. 6 is a graph showing the MTF by the crystal filter in FIG. 3, FIG. 7 is a diagram showing a modification of the crystal filter in FIG. 3,
Figure 8 is a diagram showing a specific mechanism for rotationally adjusting the direction of the crystal plate in the adapter with respect to the direction of the crystal filter in the television camera, and (A) is a cross-sectional view of 5 (B) and (C) ! (
A) 171B-B! , are sectional views taken along the line C-C, and FIG. 9 is a sectional view (A) and a front view (B) showing a mechanism different from that in FIG. 8, as well as FIGS. Figures 11 and 16 show examples of different configurations of crystal filters.
20 and 20 are diagrams showing the state of birefringence of the crystal plate and the image of the image plane of the image sensor or the end face of the fiberscope in each configuration example, FIG. 12, FIG. 14, FIG. 17, and FIG.
FIG. 1 is a diagram showing the deviation of light rays according to each configuration example, and FIG. 18 is a diagram showing the scanning line and stripe filter of the image pickup tube. 20.30.40...adapter, 21.41...
- Side shadow lens, 22.25, 63.64..., crystal filter, 22a, 22b, 22c, 51, 61° 62.
66.68, 81.82...Crystal plate, 23...
TV camera, 24... Imaging S element, 31... Screw mount section, 32... Ring, 33...
- Ring member, 34... Operating member, 35... One gloss, 36... Leaf spring, 42... Lens barrel part, 4
3. ...Ring, 44...Elastic body, 45...
Cut groove, 52.67... Quarter wavelength plate, 69...
...Image tube. Figure 11 Figure 2 (A) Figure 3 Figure 4 Figure 5 (B) (C) (D) Figure 16 Off Figure O S Figure 110 Figure 2 Otsu 111 Figure 112 Figure BiP and Figure 13 Figure 14 Figure 15? Figure 16 (A) (B) (C) (D) Figure 17 (A) (B) ? Figure 18c

Claims (1)

[Scope of Claims] The present invention consists of an adapter that can be attached to the eyepiece of an endoscope and that has a built-in photographic lens, and a television camera that can be attached to the rear of the adapter and that has a built-in image sensor. In an endoscope imaging device in which an image taken by the endoscope is captured by an image sensor in a television camera through a photographing lens of an adapter, the adapter and the television camera each include a lens made of a birefringent material. first and second filters are built-in, and when the television camera is attached to the adapter, the separation direction of birefringence by the two filters is directed to the image pickup device in the television camera. An imaging device for an endoscope, characterized in that it is disposed in an imaging optical path so as to include components horizontal and/or perpendicular to the imaging optical path.