JP2741595B2 - Endoscope light source device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source device for an endoscope, and more particularly to a light source device capable of adjusting the amount of illumination light incident from a light source to an incident end of a light guide. The present invention relates to a light source device for an endoscope. 2. Description of the Related Art Generally, a light source device for an endoscope of this type generally uses an illumination light guide by converting illumination light emitted from a light source lamp into a parallel light beam by a reflecting mirror and converging the parallel light beam by a condenser lens. At the incident end. In the middle of the illumination light path from the light source lamp to the light guide entrance end, a light shielding plate that partially blocks the illumination light is provided so as to be freely inserted and removed, and the amount of illumination is adjusted by controlling the position of the light shielding plate. I was going. [Problems to be Solved by the Invention] However, if a light-shielding plate is put in and out of the illumination light path to block the illumination light, only the illumination light passing through the periphery of the illumination light path enters the light guide as the illumination light amount is reduced. Will be done. Then, since the illumination light is largely refracted in the peripheral portion of the lens, a difference occurs in the optical path after the refraction due to the difference in the wavelength of the light, and the spectral characteristics of the illumination light incident on the light guide are changed, so that the accurate There has been a disadvantage that color reproduction is not performed. In particular, in a so-called electronic endoscope that performs image transmission using a solid-state imaging device such as a CCD (charge-coupled device), light of three primary colors is time-divisionally and alternately incident on an illumination light guide. . As a result, a noticeable shift occurs in the optical path of each of the three primary colors from the condenser lens to the light guide, so that accurate color reproduction is not performed. There was a disadvantage that diagnosis could not be performed. An object of the present invention is to provide a light source device for an endoscope that can solve such a conventional drawback and can obtain illumination light having a good color tone regardless of the adjustment state of the illumination light amount. And [Means for Solving the Problems] To solve the above-mentioned problems, a light source device for an endoscope according to the present invention provides an illumination optical path from a light source through a condenser lens to an entrance end of an illumination light guide. In the middle of the light source device of the endoscope, which is capable of adjusting the amount of illumination light by providing a light-shielding means for partially blocking the illumination light emitted from the light source, so that the amount of illumination light can be adjusted. Light quantity attenuating means for attenuating the light quantity is provided so as to block a part of the illumination light path, and the light shielding means is provided so as to enter and exit the illumination light path from the side where the light quantity attenuation means is not arranged. And [Operation] When the light shielding unit is retracted from the illumination light path, the illumination light not only passes through the light amount attenuation unit but also enters the illumination light guide through a portion where the light amount attenuation unit is not arranged. Therefore, a sufficient amount of illumination light can be obtained. When the light-shielding plate enters the illumination light path, only the illumination light passing through the light amount attenuating means enters the illumination light guide from the condenser lens. As a result, in this state, the light path area of the illuminating light toward the light guide is wider than the illuminating light amount, and light relatively near the center of the light path also enters the illuminating light guide from the condenser lens. Therefore, the shift of the optical path due to the difference in the wavelength of the light does not greatly occur due to the refraction by the condenser lens. Embodiment An embodiment of the present invention will be described with reference to FIG. 1 and FIG. FIG. 2 shows the overall configuration of the present embodiment.
Reference numeral 1 denotes an insertion portion of the endoscope, and 2 denotes an objective lens disposed at the tip of the endoscope. Have been. Reference numeral 4 denotes an illumination light guide for illuminating the field of view of the objective lens. Reference numeral 4a denotes an emission end of the illumination light guide, and reference numeral 5 denotes a light distribution lens for expanding a light distribution angle of illumination light emitted from the light guide emission end 4a. It is. in this way,
An image of a subject (observation light image) illuminated by the illumination light guide 4 is converted into an electric signal in the solid-state imaging device 3 and output. 6 outputs a control signal to the solid-state imaging device 3 and
This is a known image signal control circuit that processes an output signal from the solid-state imaging device 3. A conversion processing circuit 7 that converts the processed image signal into a standard television system and a monitor (not shown) that reproduces an image are sequentially provided. It is connected. Further, a comparison amplifier circuit 9 is connected to an output terminal of the image signal control circuit 6 via a low-pass filter 8. Then, the luminance signal of a voltage corresponding to the brightness of the image output from the image signal control circuit 6 is smoothed by the low-pass filter 8 and input to the comparison amplifier circuit 9. On the other hand, a known setting circuit 19 for setting and outputting an arbitrary reference voltage is connected to the comparison amplification circuit 9, and the smoothed luminance signal is output to the comparison amplification circuit 9.
Is compared with the reference voltage, and the result of the comparison is output as a control signal for controlling the operation of the light shielding plate 10. 4b is an entrance end of the illumination light guide, 11 and 12 are a light source and a reflector arranged in the light source device, and the illumination light emitted from the light source 11 is reflected by the reflector 12 as a parallel light flux. Thereafter, the light enters the condenser lens 13 and is condensed on the incident end 4b of the illumination light guide. In the middle of the illumination light path between the light source 11 and the condenser lens 13,
A movable light-shielding plate 10 for adjusting the amount of light reaching the condenser lens 13
And a light amount attenuating plate 20 for attenuating the amount of passing illumination light. The light amount attenuating plate 20 is fixed in the light source device, and the light shielding plate 10 may be provided on either the front side or the rear side. Although not shown, well-known three primary color filters are provided in the middle of the illumination optical path so as to alternately enter at a speed of about 10 to 30 cycles per second, and time-division illumination of the three primary colors is provided. A method is used. FIG. 1 shows a state in which the light shielding plate 10 and the light amount attenuating plate 20 are viewed from the incident end 4b side of the illumination light guide. The light quantity attenuating plate 20 is formed of, for example, a thin metal plate having a large number of through holes 20a. Illumination light passes through the through holes 20a and is blocked in other portions. The light-attenuating plate 20 may be a metal plate having a large number of circular holes, an ND filter, or the like, in addition to a rectangular hole as shown in FIG. In this embodiment, the light quantity attenuating plate 20 is arranged so as to block half of the illumination light path, and the illumination light passes through the other half as it is. In FIG. 1, a dotted line 15 indicates the outer edge of the illumination light path. In this way, the illumination light amount is, for example,
Attenuated about 20-40%. The light-shielding plate 10 rotates about a rotation shaft 16 and
Enters and exits the illumination light path from the side opposite to the side on which is disposed (the right side in FIG. 1). FIG. 1A shows a state in which the light shielding plate 10 is out of the illumination light path, FIG. 1B shows a state in which the light shielding plate 10 completely shields the illumination light path, and C shows an intermediate state between them. The operation of the light-shielding plate 10 is controlled by the output signal of the comparison amplifier circuit 9 in this embodiment.
That is, the light-shielding plate 10 moves in and out of the illumination optical path so that the amount of light incident on the solid-state imaging device 3 becomes constant according to the setting value in the setting circuit 19. In the light source device of the endoscope according to the present embodiment configured as described above, when the distance between the objective lens 2 and the subject is large, the light shielding plate 10 is retracted from the illumination optical path. Therefore,
Half of the illumination light passes through the light attenuating plate 20 and enters the illumination light guide 4, and the other half of the illumination light passes directly to the condenser lens 13 without passing through the light attenuating plate 20. Incident on. Therefore, it is possible to obtain sufficiently bright illumination light as a whole. When the distance between the objective lens 2 and the subject approaches,
The state 10 blocks a part of the illumination light path. When the objective lens 2 comes very close to the subject, most of the illumination light path is blocked by the light-shielding plate 10, and the illumination light incident on the light guide 4 has a light amount as shown by a hatched portion D by a dotted line in FIG. Only the light that has passed through the attenuation plate 20 is present. Therefore, in this state, the light path area (shaded area) is compared with the illumination light amount.
The light is relatively refracted by the condenser lens 13 and enters the illumination light guide 4 in addition to the peripheral portion of the condenser lens 13. Therefore, due to refraction at the condenser lens 13, a shift in the optical path due to a difference in the wavelength of light does not occur much. In this manner, in this embodiment, a stable illumination with a small change in color tone can be obtained regardless of how the amount of illumination incident on the illumination light guide 4 is adjusted. In the above embodiment, the operation of the light shielding plate is automatically controlled. However, the present invention is not limited to this, and the operation of the light shielding plate may be manually controlled. . Further, the present invention may be applied to an endoscope using an image guide fiber or the like instead of the solid-state imaging device. [Effects of the Invention] According to the light source device of the endoscope of the present invention, it is possible to obtain sufficiently bright illumination light when the light shielding means is retracted from the illumination light path, and to illuminate the light by inserting the shielding means in the illumination light path. When the light quantity is reduced, the light path area is maintained wide by the presence of the light quantity attenuating means, and the optical path does not shift due to the difference in the wavelength of the light. Has an excellent effect of obtaining illumination light of

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view of a light shielding plate and a light quantity attenuating plate according to one embodiment of the present invention, and FIG. 2 is a block diagram showing an overall configuration of the embodiment. DESCRIPTION OF SYMBOLS 1 ... insertion part, 2 ... objective lens, 3 ... solid-state imaging device, 4 ... illumination light guide, 4b ... entrance end part, 10 ...
… Light shield plate, 11… Light source, 12… Reflection mirror, 13… Condenser lens, 20… Light amount attenuation plate.

Claims (1)

(57) [Claims] In the middle of the illumination light path from the light source through the condenser lens to the entrance end of the illumination light guide, light shielding means for partially blocking the illumination light emitted from the light source is provided so as to be able to freely enter and exit from the side of the illumination light path. In the light source device of the endoscope, the amount of illumination light can be adjusted. An endoscope which is provided so as to block a partial area of the illumination light path, and wherein the light shielding means is provided so as to enter and exit the illumination light path from a side on which the light amount attenuation means is not provided. Mirror light source device. 2. 2. A light source device for an endoscope according to claim 1, wherein said light amount attenuating means blocks substantially half of said illumination light path. 3. 3. The light source device for an endoscope according to claim 1, wherein said light amount attenuation means is a metal plate having a large number of through holes.