JPS61177421A - Light source device for endoscope - Google Patents

Abstract

PURPOSE:To prevent the change of the luminous intensity characteristic and the spectral characteristics of an illuminating light by providing a stop means which controls the quantity of light and a means which makes the directional distribution of an incident light uniform. CONSTITUTION:Color signals R, G, and B outputted from a video process part 16 are added by an adder 18 to take out a luminance signal component, and this component is integrated by an integrating circuit 19 having a time constant of an about one-frame period to obtain a dimming signal, and this signal is applied to the control terminal of a driving circuit 20. When the stop means controlled on a basis of the dimming signal is used, the illuminating light whose quantity is controlled is uniformed and irradiated to the incidence end surface of a light guide 9 if this illuminating light is led through a light guide fiber 5, and the luminous intensity characteristic and the spectral characteristic of the illuminating light irradiated to the object side are kept constant independently of the extent of aperture. Thus, the trouble that the contrast of a displayed image in the center part and that in the peripheral part are different from each other by the extent of aperture, the trouble that the hue in the center part and that in the peripheral part are different from each other, or the like are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a light source device for an endoscope in which light distribution characteristics etc. do not change even when the amount of irradiated light is varied.

[Technical Background of the Invention and Problems Therewith] In recent years, endoscopes that use solid-state image sensors to display images of objects on display devices such as cathode ray tubes have been realized.

The electronic endoscope using the above solid-state image sensor forms an optical image on an image guide fiber.

It has the advantage that it is easier to record images compared to the previous model, and with the progress of highly integrated technology, it can be made smaller and smaller in the future.

However, when using the above-mentioned solid-state image sensor, if the amount of light incident on the light-receiving element on the image carrying surface is too large, excessive charge leaks to the surrounding area, causing blurring on the playback screen and the flumink phenomenon. There is a problem that it becomes impossible to faithfully reproduce the image, and that it becomes impossible to take an image until the normal state is restored.

FIG. 4 shows an example of a conventional aperture device for controlling the intensity of illumination light on the light source device side so as to prevent the blooming phenomenon described above from occurring.

That is, light from a discharge lamp 51 as a light source is reflected by a concave reflecting mirror 52 to form a substantially parallel light beam, and a condenser lens 53 irradiates this parallel light beam onto the input end of a light guide fiber 54 as an illumination light transmission means. In the optical system, the central part of the disk is cut out as shown in FIG. 5 on the optical path between the condenser lens 53 and the light guide fiber 54, and a part of the disk is cut out in a substantially fan shape. A shaped aperture 55 is provided, and by moving the aperture 55 in parallel or rotationally (downward in FIG. 5), a part of the light beam is blocked depending on the amount of movement and is directed to the light guide fiber 54. The amount of incident light is varied to adjust the illumination light (2) emitted from the other end of the light guide fiber 54 toward the subject.

However, in this conventional example, when the diaphragm 55 is used to narrow down the light beam, the light beam is blocked from the periphery. Since the angular distribution changes, the light distribution characteristics change, and the illumination intensity of each part within the field of view changes non-uniformly. Furthermore, this shape has the disadvantage that the response speed of the aperture operation is slow, making it unsuitable for automatic light control.

Further, in the light guide fiber 54, the maximum incident angle at which light can be transmitted normally depends on the wavelength, that is, the numerical aperture varies depending on the wavelength. For this reason, when the condensed light is irradiated onto the input end of the light guide fiber 54 as in the conventional example, if the aperture 55 is used to narrow the optical path in the middle of the condensed light, the light is blocked from the peripheral part side where the wavelength dependence is large. Therefore, there was a drawback that the spectral characteristics of the illumination light irradiated from the output gA end side of the light guide fiber 54 to the subject side also changed (depending on the aperture amount).

Further, even if the aperture 55 is disposed in the parallel beam portion, there is a drawback that the light distribution characteristics change.

[Object of the Invention] The present invention has been made in view of the above points, and the light distribution characteristics and spectral characteristics of the illumination light emitted to the subject side change even when the amount of illumination light is changed by changing the aperture amount. It is an object of the present invention to provide a light source device for an endoscope that prevents such problems from occurring.

[Summary of the Invention] The present invention provides a diaphragm means that can adjust the amount of illumination light from the light source, and a plurality of optical The light ffi! is composed of a collection of elements. The light guide is provided with means for inputting the i1-articulated light, making the directional distribution of the light uniform, and outputting it to the incident end surface of the light guide.

[Embodiments of the invention] Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 1 is a configuration diagram showing a first embodiment of an endoscope light source device according to the present invention.

As shown in this figure, the illumination light from a light source 1 is reflected by a concave mirror 2 and turned into a substantially parallel light beam, and then converted into a parallel light beam with a smaller diameter by a convex lens 3 and a concave lens 4, which is the main part of this embodiment. The light is irradiated onto one end surface (incident end surface) 5a of the light guide fiber 5. The above concave lens 4
A diaphragm 6 such as a variable aperture type that can almost arbitrarily change the passing area of the light beam is disposed between the light guide fiber 5 and the light guide fiber 5, and this diaphragm 6 is controlled by a dimming signal to be described later. It is designed to be rotationally driven by a motor 7.

The light guide fiber 5 is arranged so that the fiber arrangement at the input end face 5a into which the light flux is incident and the fiber arrangement at the output end face 5b from which the light flux is emitted are mutually random. In other words, the position of the fiber on the input end face 5a is the same as that on the output end face 5b of the fiber.
There is no specific positional relationship with the position in , but the arrangement is independent of each other. Therefore, even if the area of the luminous flux incident on the input end face 5a changes, the distribution of the luminous flux emitted from the output end face 5b will not be directionally biased, and the light distribution characteristics and spectral characteristics will be kept constant; Only the intensity will change.

The light flux that has passed through the light guide fiber 5 is converged by a condenser lens 8, and is irradiated onto one end surface (incidence end surface) of a light guide 9 inserted into the endoscope insertion section, and is distributed from the other end surface (output end surface). The light is irradiated toward the object through the lens 10.

In the endoscope, an objective lens 12 for imaging is disposed on the distal end side of an elongated insertion section 11, and a color solid-state image sensor 13 is disposed so that its light receiving surface faces the image forming position of the objective lens 12. It is set up. The solid-state image carrier 13 has a color mosaic (or color stripe) filter 13a on its front side, and a filter 13a of R (red) and G (green) on the rear side of this filter.
, B (armor) A large number of light receiving elements each having a photoelectric conversion function corresponding to each color filter are regularly arranged.

Thus, each light receiving element receives light separated into pixels for each color, and the electrical signals corresponding to the photoelectrically converted pixels are sequentially read out by a clock signal (not shown), and these read signals have a low noise index. Preamplifier (preamplifier) 14
The signal is amplified by the signal cable 15 and taken into the video processing section 16. The video processing unit 16 samples and holds the captured signals in R, G, and B color sample and hold circuits corresponding to each color signal, and samples and holds the sampled and held R and G signals.

The B signal is simultaneously read out from each color sample and hold circuit in the readout mode, and after being further amplified, horizontal and vertical synchronizing signals (not shown) are added and input to the monitor color television 17 so that it can be displayed as a color image. It is composed of

By the way, in the above-mentioned endoscope, if the subject is too close and the illumination intensity is too high, or if the subject has a highlighted part with a high reflection intensity, the illumination intensity is too thick (strong) and blooming occurs. Automatic light adjustment means is provided to prevent the entire image from becoming washed out and the contrast not being used sufficiently. The motor 7 of the aperture device is controlled based on the light control signal from the automatic light control means.

That is, the color signals R output from the video processing section 16,
G and B are added in an adder 18 to extract a luminance signal component, and this luminance signal component is integrated in an integrating circuit 19 having a time constant of about one frame period to produce a dimming signal. is applied to a control end of a motor drive circuit 20 as a drive source for the motor 7.

The motor drive circuit 20 may be configured using a power amplifier circuit or the like that increases the amount of rotation of the motor 7 by greatly varying its output current or output voltage as the bias level applied to the control terminal increases. can.

According to the light source device shown in the above embodiment, even when using not only the diaphragm device in the illustrated example that is controlled based on a dimming signal but also any diaphragm means, illumination light adjusted by the optical device can be transmitted to the light guide fiber 5. By guiding the light through the light guide, it is possible to uniformly irradiate the incident end face of the light guide 9, and therefore, the light distribution and spectral characteristics of the illumination light irradiated onto the object side can be kept constant regardless of the aperture amount. can. As a result, problems such as differences in the contrast of the displayed image between the center and the periphery depending on the aperture pin or different color tones do not occur.

2 and 3 show a second embodiment of the invention.

In this embodiment, as shown in FIG. 2, instead of the light guide fiber 5 in FIG. 1, a plurality of convex lenses are arranged in one plane so that the directions of the optical axes are mutually random. This is commonly called a fly's eye lens 21. (The front view is shown in FIG. 3). In this case, the convex lenses constituting the lens 21 are tilted to each other on the same plane so that the parallel light incident through the diaphragm 6 is evenly irradiated onto the front surface of the condenser lens 8. Therefore, the lens 21 has convex and convex portions in each convex lens unit. It is shaped like a surface. This lens 21
is computer-designed so that the light passing through each convex lens is made uniform.

According to this embodiment, the length in the light direction is shorter than in the case of randomly arranging the input and output ends of the light guide fiber (see Fig. 1), and the arrangement is constant as in the case of Fig. 1. Optical and spectral properties will be obtained.

Although FIG. 1 describes an endoscope device configured to enable color images using a color solid-state image sensor equipped with a color mosaic (or color stripe) filter, the present invention does not include a monochrome solid-state image sensor. It is also possible to use an image sensor and arrange a three-color rotating filter on the output side of the light guide fiber 5, thereby making it possible to capture color images by sequential illumination of color planes. The same applies to FIG.

Although the above embodiment describes a light source VR device for an endoscope, the present invention can also be applied to a light source device for a microscope.

[Effects of the Invention] As described above, according to the present invention, 1. It is possible to enter light whose intensity is adjusted, make the directional distribution of the light uniform, and then output it to the input end side of the light guide, and the light distribution and spectral characteristics of the illumination light irradiated to the object side change depending on the aperture. You can avoid it. As a result, problems such as differences in the contrast of the displayed image between the center and the periphery and changes in color tone due to the aperture opening are eliminated, and it is possible to accurately observe the affected area using the endoscope. In particular, it becomes possible to accurately diagnose even the initial symptoms of the affected area. Further, the diaphragm used can be one that is structurally simple.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of an endoscope light source device according to the present invention, FIG. 2 is a block diagram showing a second embodiment of the present invention, and FIG. 3 is a main part of FIG. 2. Front view of the lens body, 4th
This figure is a block diagram of a conventional light source device equipped with a diaphragm, and FIG. 5 is a front view without the diaphragm shown in FIG. 4. 1... Light source 5... Light guide fiber 6...
- Aperture 9... Light guide 21... Fly-eye lens Figure 2 Figure 3r14 Figure 5 Continued from page 11 Inventor Nakamura-husband Hatagaya 2 Co., Ltd., Shibuya-ku, Tokyo ) Inventor: Ken Sugawara, Hatagaya 2 Co., Ltd., Shibuya-ku, Tokyo) Inventor: Hideo Tomabechi, Hatagaya 2 Co., Ltd., Shibuya-ku, Tokyo

Claims (3)

[Claims] (1) In an endoscope light source device that guides illumination light from a light source to a light guide of an endoscope insertion section and illuminates a target object through this light guide, the light source and the incident end of the light guide On the optical path of the light source, there is a diaphragm means that can adjust the amount of illumination light from the light source, and an aggregate of a plurality of optical elements. 1. A light source device for an endoscope, characterized in that a light source device for an endoscope is provided with a uniformizing means for emitting light from an incident end face of a light guide. (2) The endoscope according to claim 1, wherein the uniformizing means is constituted by a fiber bundle in which the fibers are arranged randomly at the input and output ends. light source device. (3) A patent characterized in that the uniformizing means is constituted by a lens assembly formed by arranging the optical axes of each lens in random directions on substantially the same plane orthogonal to the direction of incidence and output of light. A light source device for an endoscope according to claim 1.