JPH0614139B2 - A diaphragm device for a light source device for an endoscope - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a diaphragm device for a light source device for an endoscope, which is suitable for changing the amount of illumination light.

[Technical Background of the Invention and Problems Thereof] In recent years, there has been a realization of an endoscope that can display an image of a subject on a display device such as a cathode ray tube using a solid-state image sensor.

The electronic endoscope using the above solid-state image sensor is easier to record images than the one that forms an optical image on the image guide fiber, and with the progress of high integration technology, it will be improved in the future. It has the advantage that it can be made smaller.

However, when the solid-state image sensor is used, if the amount of light incident on the light-receiving element on the imaging surface is too large, excessive electric charge leaks to the periphery, causing a bleeding blooming phenomenon on the playback screen, and that portion causes an image There is a problem that faithful reproduction cannot be performed and imaging becomes impossible until the normal state is restored.

As a conventional example of a diaphragm device for controlling the intensity of illumination light on the light source device side so that the blooming phenomenon does not occur, there is one as shown in FIG.

That is, the light of the discharge lamp 61 as the light source is reflected by the concave reflecting surface 62 to be a substantially parallel light beam, and the parallel light beam is irradiated by the condenser lens 63 onto the incident end of the light guide fiber 64 as the illumination light transmitting means. In the optical system, the central portion of the disc is cut out on the optical path between the condenser lens 63 and the light guide fiber 64, and a part of the disc is cut out in a substantially fan shape. By disposing a stop 65 having a shape and moving the stop 65 in parallel (downward in FIG. 6), a part of the light beam is blocked in accordance with the amount of movement, and the light is guided to the light guide fiber 64. The amount of incident light is varied to adjust the amount of illumination light emitted from the other end of the light guide fiber 64 to the subject side.

However, in this conventional example, when the light is narrowed down by the diaphragm 65, the light flux is shielded from the peripheral portion, so that the light distribution angle of the illumination light emitted from the tip end surface of the light guide fiber 64 to the subject (object) side. Since the distribution changes, the light distribution characteristics change, and the illumination intensity of each part in the field of view changes nonuniformly. In addition, the maximum incident angle of light guide fiber 64 that can be normally transmitted depends on the wavelength, that is, the numerical aperture differs depending on the wavelength. Therefore, when the condensed light is radiated to the incident end of the light guide fiber 64 as in the above-mentioned conventional example, if it is narrowed down by the diaphragm 65 on the optical path in the middle, the light is shielded from the peripheral side having a large wavelength dependence. Therefore, there is a drawback that the spectral characteristic of the illumination light emitted from the emission end side of the light guide fiber 64 to the subject side also changes (depending on the diaphragm amount).

Further, even if the diaphragm 65 is arranged in the parallel light flux portion, there is a drawback that the light distribution characteristic is changed.

[Object of the Invention] The present invention has been made in view of the above points, and is an aperture stop for an endoscope light source device capable of adjusting the amount of illumination light emitted to the subject side without changing the light distribution characteristics and spectral characteristics. The purpose is to provide a device.

SUMMARY OF THE INVENTION The present invention has a zoom optical system disposed between a light source and an incident end of a light guide that transmits illumination light and emits the light from its emission end, and changes the amount of illumination light by changing the aperture of a diaphragm. On the other hand, by interlocking the zoom optical system along the optical axis, the light distribution angle of the incident light incident on the incident end of the light guide is kept constant and the distribution of the illumination light emitted from the emitting end of the light guide is maintained. The light characteristic and the spectral characteristic are not changed.

Embodiments of the Invention Hereinafter, the present invention will be specifically described with reference to the drawings.

FIGS. 1 and 3 relate to a first embodiment of the present invention, FIG. 1 shows a diaphragm state of the first embodiment, FIG. 2 shows a narrowed state from the state of FIG. 1, and FIG. The figure shows an endoscope in which an automatic light control means is formed by using the first embodiment.

The diaphragm device 1 of the first embodiment has a structure as shown in FIG.

That is, the illumination light of the light source 3 in the light source device 2 is reflected by the concave reflecting mirror 4 to be a substantially parallel light beam, and the iris diaphragm 5 and the zoom optics forming the diaphragm device 1 on the central optical axis of this light beam. The amount of light is controlled by the system 6 so that the light can be condensed and irradiated on the incident end face 7A of the light guide 7 which is detachably mounted on the light source device 2.

The diaphragm 5 is rotated by rotating the rotary ring 8.
The size of the aperture 9 having a circular shape or a shape close to that of the diaphragm 5 can be varied as shown by an arrow A while maintaining its circular shape (for example, like a diaphragm mechanism for a camera). Together with this (size) variable operation of the opening 9, for example, the convex lens front lens 6A of the zoom optical system 6 can be moved back and forth in the optical axis direction (as indicated by arrow B) with respect to the convex lens rear lens 6B. By moving the front lens 6A, the maximum incident angle (incident on the incident end surface 7A of the light guide 7) of the illumination light beam that has passed through the zoom optical system 6, that is, the light distribution angle can be kept constant. I am doing it.

As a mechanism for moving the front lens 6A, a stepped small-diameter portion is provided on the outer circumference of the lens outer frame 10 to which the rear lens 6B is attached, and the rotary ring 8 is rotatably fitted to the lens outer frame 10. A lens inner frame 11 that is slidably movable in the axial direction is fitted inside the outer frame 10, and a front lens 6A is attached to the lens inner frame 11. Then, the lens outer frame 10
A spiral cam groove 12 is formed in a portion of the rotary ring 8 where the rotary ring 8 is fitted, and a pin 13 having a tip projecting inward from the inner surface of the lens outer frame 10 is formed through the cam groove 12. The tip of the protruding pin 13 is housed in the groove 14 of the lens inner frame 11, and is guided to the cam groove 12 by the rotation (rotation) of the rotating ring 8.
Position moves along the optical axis direction, the inner frame 11 accommodating the tip of the pin 12 also moves, and the front lens 6 moves.
A is also designed to move in the optical axis direction.

With the above mechanism, the front lens 6A of the zoom optical system 6 moves, and the light flux passing through the zoom optical system 6 is incident on the incident end face 7 of the light guide 7.
A is held at a constant light distribution angle and focused and irradiated. As the front lens 6A of the zoom optical system is moved in order to keep this light distribution angle constant, the shift of the focus position of the zoom optical system 6 (with respect to the incident end face 7A) is A cam groove 15 is formed, and a fixing pin 16 fixed to the wall surface or the like of the light source device 2 (or via an interposing member) is housed in the cam groove 15, and the zoom optical system is rotated along with the rotation of the rotating ring 8. The whole 6 is moved as shown by an arrow C for correction so that the light distribution angle can be kept constant.

In the embodiment having such a configuration, the size of the aperture 9 of the diaphragm 5 is changed by rotating the rotary ring 8 to adjust the amount of light passing through the aperture 9 and the light is emitted from the emission end of the light guide 7. The amount of illuminating light can be variably adjusted (although if only the size of the aperture 9 is changed, it is reduced from the light beam side incident on the incident end face 7A at a large incident angle), the zoom optical system 6 The light (imaging) state changes, and the incident end surface 7A of the light guide 7 is always irradiated with a constant light distribution angle. For example, when the aperture is closed with the relatively large aperture 9 in FIG. 1, the rotating ring 8 is moved from the state in which the light flux is set to the light distribution angle of a predetermined angle θ through the zoom optical system 6 as shown in FIG.
2 is rotated and narrowed down to a small opening 9 as shown in FIG. 2, the front lens 6A of the zoom optical system 6 is moved to the light guide side by the rotation operation of the rotary ring 8, and the entire zoom optical system 6 is further moved. Also moves in the same direction, and the zoom optical system 6 is maintained at a constant light distribution angle in which the maximum incident angle of the light beam incident on the incident end surface 7A of the light guide 7 is the same as in FIG. Therefore, the amount of illumination light emitted from the emission end of the light guide 7 can be variably controlled while keeping the light distribution angle constant. Further, the spectral distribution shape with respect to the incident angle of the light beam incident on the incident end face 7A is also retained.

Therefore, the intensity of the illumination light emitted to the subject side is variable without depending on the diaphragm amount, while the light distribution characteristics and the spectral characteristics are kept constant. Therefore, depending on the aperture amount, it is possible to eliminate a part of the light source from being unevenly darkened or the color tone being changed.Therefore, the aperture of the light source device for the endoscope used for diagnosing the condition of the affected area from the color tone or the like can be eliminated. Appropriate as a device.

Although the rotating ring 8 is manually rotated in the first embodiment, the rotation of the rotating ring 8 can be controlled to automatically adjust light.

FIG. 3 realizes an endoscope having an automatic light control function by using the first embodiment.

That is, in the endoscope 21 provided with the automatic light control means, the objective lens 23 for image formation is arranged at the tip of the elongated insertion portion 22, and the solid-state image pickup device 24 is arranged at the image formation position of the objective lens 23. To form an image pickup means.

The output of the solid-state image pickup device 24 is amplified by a low noise figure preamplifier 25, further amplified by a local amplifier 26, and applied to one input terminal of a multiplier 28 forming a high speed AGC circuit section 27. , And is applied to one input end of a comparator 30 forming a mechanical automatic light control section 29.

At the other end of the comparator 30, a reference level V
_E1 is applied, and this differential output is integrated by the integrator 32 at the next stage having a time constant of one frame as the integration time constant, and this integrated output is applied to the motor drive circuit 34 via the sample hold circuit 33. To be done. The motor drive circuit 34 outputs drive pulses of a number of pulses corresponding to the input signal level, and the motor 3 is driven by an angle corresponding to the number of pulses.
5 is rotated, and the gear 3 attached to the rotary shaft of the motor 35
A rotary ring 8'provided with a gear meshing with 6 is provided on the outer circumference of the rotary ring 8 '.

The reference level V _E1 is set in advance to a level suitable for image pickup by the solid-state image pickup device 24, so that the amplifier 2
When the output level of 6 is larger than the level V _E1 , the integrator 32 integrates the output level, and the level averaged in one frame period output from the sample hold circuit 33 narrows down the state one cycle before (opening 9 Becomes smaller). For example, if the state one cycle before is FIG. 1, the state is narrowed down to the state shown in FIG. 2, and the amount of illumination light is reduced by this narrowing down, and the output level of the amplifier 26 is reduced in the next frame. When the output level reaches the reference level V _E1 when the output level is averaged over one frame, the aperture amount is held. That is, the level is automatically set to a level suitable for imaging by the solid-state image sensor 24. The drive signal output from the motor drive circuit 34 is a signal that defines the rotation direction together with the pulse.

By the way, since the rotary ring 8'is mechanically movable in the automatic light control unit 29, it takes time to reach a level suitable for imaging (relative to an electrical signal).
Therefore, in the endoscope 21, the AGC circuit section 27 further optimizes the video signal level at a high speed.

That is, the output of the multiplier 28 is input to the bioprocess unit 41 and is applied to one input end of the comparator 42, and is compared with the reference level V _{E2 of the} power supply 43 applied to the other end. It is input to the integrator 44, and the integrated output is applied to the other input terminal of the multiplier 28. The reference level V _E2 is the above-mentioned reference level V _E2.
It is set above _E1 and therefore, as the input signal level being compared (usually less than almost any level V _E2 ) approaches this level value, ie, as the input signal level increases, it goes through the integrator 44. The comparison differential output level, which is a multiplication factor (for the input signal), decreases, and the input signal level input to the video processing unit 41 decreases in the next frame. Since the AGC circuit section 27 has no mechanical moving parts, it is set at an appropriate video signal level at high speed.

The video signal input to the video process unit 41 is
The color signals are separated into R, G, and B color signals and displayed in color on the color monitor 45.

The AGC circuit unit 27 corrects the deviation from the appropriate level in the video signal level even when the automatic light control unit 29 does not reach the sufficiently appropriate automatic light control state during the transient operation period of the automatic light control. Have the function to This AGC
Since the automatic dimming unit 29 is provided in front of the circuit unit 27 with respect to the input signal, the final balanced value of the automatic dimming is independent of the AGC circuit unit 27 in the latter stage.
Will be done by.

According to the endoscope 21 provided with the automatic light control means, a color image having a good SN ratio can be obtained. Also, in the transitional period of automatic light control, it is possible to obtain an image in which the contrast and the like are optimized as compared with the conventional example.

In the first embodiment, the zoom optical system is the front lens 6A,
Although it is formed by the rear lens 6B, a zoom optical system 52 is formed by further providing a third lens in the diaphragm device 51 of the second embodiment shown in FIG.

That is, in the expansion device 1 shown in FIG. 1, the pin 13 attached to the rotary ring 8 is passed through the cam groove 12 of the outer frame 10 and the groove 14 ′ of the inner frame 10 inside the pin 13 as well. The front end of the frame 53 is housed in the cam groove 54 of the frame 53.

A concave lens 55 is attached to the frame 53.

In the second embodiment, by rotating the rotary ring 8, the convex lens front lens 6A is opposed to the convex lens front lens 6A.
The concave lens 55 and the concave lens 55 are moved together in the optical axis direction. In this case, when the rotary ring 8 is rotated by making the groove provided in the frame 53 to which the concave lens 55 is attached the cam groove 54, the convex lens is moved in conjunction with the front lens 6A. Can have different amounts of movement. Similar to the first embodiment, these movement amounts are linked to the size of the opening 9 and are the amounts at which the light distribution angle of the light flux irradiated to the incident end surface 7A of the light guide 7 is always kept constant.

In the second embodiment, by providing the movable concave lens 55, it is not always necessary to move the zoom optical system 52 as a whole, and the zoom optical system 52 may be fixed as shown (of course, movable). ).

The operation and effect of the second embodiment are substantially the same as those of the first embodiment. Further, the automatic light control means can be formed by using the second embodiment.

The present invention is such that the light distribution angle of the light beam incident on the incident end face of the light guide is kept constant even when the size of the aperture is changed by the zoom optical system.
The configuration of the zoom optical system is not limited to that shown in the figure as long as it has such a function. or,
The diaphragm device of the present invention does not necessarily have to be arranged in the optical path of a parallel light beam, but may be arranged, for example, in the condensed light beam. Further, it is clear that the present invention can be applied to an endoscope that does not use a solid-state image sensor.

[Effects of the Invention] As described above, according to the present invention, the zoom optical system is used for the diaphragm device, and the size of the aperture for adjusting the light amount is adjusted so that the zoom optical system is moved to irradiate the incident end face of the light guide. Since the incident light distribution angle is kept constant,
It is possible to change the illumination intensity as a whole to a level suitable for imaging or observation without changing the light distribution characteristic and the spectral characteristic of the illumination light emitted from the emission end of the light guide to the subject side depending on the aperture amount.

[Brief description of drawings]

1 to 3 relate to a first embodiment of the present invention.
FIG. 2 is a sectional view showing the structure of the first embodiment, FIG. 2 is a sectional view showing the first embodiment when an opening state different from that of FIG. 1 is set, and FIG. FIG. 4 is a sectional view showing an endoscope in which automatic light control means is formed, FIG. 4 is a sectional view showing a second embodiment of the present invention, FIG. 5 is a structural view showing a conventional example, and FIG. 6 is a conventional example. It is explanatory drawing which shows the shape of a diaphragm. 1 ... Aperture device, 2 ... Light source device 3 ... Light source, 5 ... Aperture 6 ... Zoom optical system, 7 ... Light guide 7A ... Incident end, 8 ... Rotating ring 9 ... Aperture, 10 ... ... Lens outer frame 11 ... Lens inner frame, 12 ... Cam groove 13 ... Pin, 14 ... Groove 15 ... Cam groove, 16 ... Pin 21 ... Endoscope, 24 ... Solid-state image sensor 27 ... ... AGC circuit part, 29 ... automatic light control part 51 ... diaphragm device, 52 ... zoom optical system 55 ... concave lens

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Nakamura 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd. (72) Inventor Kazutake Sugawara 2-43-2 Hatagaya, Shibuya-ku, Tokyo No. Olympus Optical Industry Co., Ltd. (72) Inventor Hideo Tomamechi 2-34-2 Hatagaya, Shibuya-ku, Tokyo Within Olympus Optical Industry Co., Ltd.

Claims (1)

[Claims] 1. A diaphragm device of an endoscope light source device for variably adjusting the intensity of illumination light radiated to an object side through a light guide by changing the size of an aperture, and collecting light from the illumination light source. The optical system that emits light and irradiates the incident end of the light guide is composed of a zoom lens system, and the zoom lens system is interlocked with the change in the size of the aperture to maximize the incident light irradiated to the incident end face of the light guide. A diaphragm device for a light source device for an endoscope, wherein an incident angle can be maintained at a constant value that does not depend on the intensity of incident light.