JPH0675568B2 - Light control device for endoscope - Google Patents

Description

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

[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 color 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, in the case of using the above-mentioned solid-state image sensor, 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 reproduction screen, and that portion is the image. There is a problem in that the image cannot be reproduced faithfully and the image cannot be captured until the normal state is restored.

FIG. 6 shows 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. This device is disclosed in
No. 58-86136.

That is, the light of the discharge lamp 41 as the light source is reflected by the concave reflection surface.
It is reflected by 42 to be a substantially parallel light beam, and this parallel light beam is condensed by a condenser lens 43 as a light guide fiber 44 as an illumination light transmission means.
In the optical system for irradiating the entrance end of the disc, the central portion of the disc is cut out on the optical path between the condenser lens 43 and the light guide fiber 44 as shown in FIG. A diaphragm fan 45 with a notched fan shape is provided.
By parallelly or rotationally moving 45 (downward in FIG. 7), a part of the light flux is shielded according to the amount of movement to change the amount of light incident on the light guide fiber 44. The amount of illumination light emitted from the other end to the subject side is adjusted. The solid line in the drawing shows the open state of the diaphragm, and the broken line shows the closed state.

However, in this conventional example, as the light is shielded from the peripheral portion when the light is narrowed down by the diaphragm 45, the light distribution angle distribution emitted from the tip end surface of the light guide fiber 44 to the subject (object) side. Changes the light distribution characteristic, and the illumination intensity of each part in the field of view changes nonuniformly. Further, this shape has a drawback that the response speed of the diaphragm operation becomes slow and it is not suitable for automatic light control.

Further, the maximum incident angle of light guide 44 which can be normally transmitted depends on the wavelength, that is, the numerical aperture varies depending on the wavelength. For this reason, when the condensed light is radiated to the incident end of the light guide 44 as in the above-mentioned conventional example, if it is narrowed by the diaphragm 45 on the optical path in the middle, it is shielded from the peripheral side of the optical path and the center Since the amount of light passing through the section increases, the spectral characteristic of the illumination light emitted from the light emitting end side of the light guide 44 to the subject side also changes (depending on the diaphragm amount), which causes a color shift.

Further, even if the diaphragm 45 is arranged in the parallel light flux portion, the light distribution characteristic is changed.

Further, since one end of the diaphragm spring 45 is driven by being connected to a solenoid, there is a drawback that a diaphragm spring and a solenoid are required as components for diaphragm operation, and extra space is required. It was

[Object of the Invention] In view of the above points, the present invention provides a uniform light distribution intensity without changing the light distribution characteristic of the illumination light emitted to the subject side depending on the diaphragm amount, and does not cause deterioration of the spectral characteristic. Moreover, it is an object of the present invention to provide an endoscope light quantity control device which does not require an extra space and has a good response speed.

[Summary of the Invention] An apparatus of the present invention is an endoscope apparatus configured to illuminate an object with illumination light through a rotary filter for three-color separation, and to image the colored light with a solid-state image sensor. A luminance signal is obtained from the converted three-color electric signal, and the speed control unit of the rotary filter is controlled according to the magnitude of the luminance signal level, so that the luminance signal level is always at an appropriate level. The rotation speed is controlled so that the irradiation light amount on the subject can be automatically adjusted.

Embodiments of the Invention Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a first embodiment showing a configuration of a light amount control device for an endoscope according to the present invention, and FIG. 2 shows a configuration of a rotary filter used in the device of FIG.

In FIG. 1, reference numeral 1 is a tip portion of an endoscope, and the tip portion 1 is composed of an imaging portion A and an illumination portion B. In the imaging portion A, an imaging lens 2 that converges light from a subject, a solid-state imaging device 3 such as a charge imaging device (CCD) that receives the converged light image, and an electric signal imaged by this device are amplified. A preamplifier 4 is provided. Also, the lighting part B
A light guide fiber 5 that guides the illumination light from an illumination means described later and an illumination lens 6 for illuminating the subject with the light are provided in the. The light guide fiber 5 is extended toward the hand side, and three color lights are made incident on the end face of the light guide fiber 5 from the illumination means 7. The illuminating means 7 collects white light from a light source lamp 8 having a reflecting mirror, a light-transmitting lens 9, a light-transmitting plate (a plate having a light-transmitting hole having a constant diameter) 10 and a lens 11.
Through the lens 13 for irradiating the three-color separation rotary filter 12 in a parallel light state, and the three color lights of R (red), G (green), and B (blue) transmitted through the lens 13 to the incident end face of the light guide fiber 5 sequentially. It is configured to be incident. Rotary filter 12
Is designed to be rotated by the motor 14,
Is equipped with a rotation detector 15 so that the rotation speed of the motor can be detected. The rotation detection unit 15 detects the number of rotations of the motor as a pulse-like electric signal, the signal is smoothed by the low-pass filter circuit 16 and converted into a DC voltage, and then input to one input terminal of the comparison amplifier 17. It is like this. A comparison output on the brightness detection side (described later) that is compared with the DC voltage on the rotation detection side is input to the other input terminal of the comparison amplifier 17. The difference voltage between the two inputs of the comparison amplifier 17 is input to the servo amplifier 18, and the output thereof controls the rotation speed of the motor 14. Therefore, the rotation detection unit 15, the low-pass filter circuit 16, the comparison amplifier 17, and the servo amplifier 18 form a speed control unit.

By the way, as shown in FIG. 2, the rotary filter 12 has three windows formed on a circular light-shielding plate 19, and three-color filters of an R filter 20, a G filter 21, and a B filter 22 are provided on each window.
It is configured such that they are arranged in a substantially annular shape on the same circumference with an equal light-shielding interval l. R, G, B color filters 20, 21, 22
Both ends of are formed in an arc shape that is recessed inward to improve the rise and fall of the transmission and blocking of the illumination light. or,
The light-transmitting regions of the R, G, B filters 20, 21, 22 are B filters 22 for compensating the spectral sensitivity characteristic of the solid-state image sensor 3, for example, CCD.
Of the R filter 20 and the region of the R filter 20 are minimized. That is, the light receiving sensitivity of the CCD varies depending on the wavelength region, and by correcting the decrease in sensitivity particularly in the blue wavelength region, when performing imaging using the CCD,
The electrical signal outputs (CCD output) of the optical images corresponding to red, green, and blue are made to have almost the same level. Further, the rotary filter 12 has three read pulse detection holes H ₁ , H ₂ , and H ₃ formed on the same circumference in the vicinity of the outer periphery of the rotary filter 12, and one rotation of the rotary filter 12 near the outer circumference. A start pulse detecting hole Hs for detecting the is formed. The holes H _{1 to} H ₃ and the holes Hs are detected by a hole detecting photointerrupter 23 provided near the outer peripheral edge of the rotary filter 12, as shown in FIG. As shown in FIG. 2, the photo interrupter 23 is composed of a photo interrupter 23a for detecting a read pulse and a photo interrupter 23b for detecting a start pulse. For these photo interrupters, for example, photo couplers are used. The read pulse and start pulse obtained by the hole detection are input to the timing generator unit 24 as shown in FIG. 1, and the timing generator unit 2 generates a timing signal for setting the read period of the solid-state image sensor 3. It has become so. The timing generator 24 uses the clock signal from the reference clock generator 25 to generate a timing signal.

On the other hand, the electric signal of the solid-state image pickup device 3 passes through the preamplifier 4 and is further amplified by the amplifier 26 on the near side, and is then composed of a signal processing unit (not shown) (mainly composed of a frame memory corresponding to each color of R, G, B). Is supplied to the resistance circuit 27. The resistor circuit 27 is composed of three resistors 27a, 27b, 27 connected in series between the output terminal of the amplifier 26 and the ground point.
The signal level of each color is detected so as to correspond to the brightness of the subject. The detected signal level of each color image is taken out through the switch circuit 28. The switch circuit 28 uses the switching timing signals created by the timing generator section 24 to generate R, G, B
It can be switched every time. The extracted signal level of each color is further passed through a low-pass filter circuit 29 to be converted into a DC voltage corresponding to the brightness level of the subject and supplied to one input end of the comparison amplifier 30. A reference voltage source 31 is connected to the other input terminal of the comparison amplifier 30 to supply a constant DC voltage E. Therefore, the comparison amplifier 30 compares the reference luminance signal level corresponding to the voltage E with the detected luminance signal level to obtain the difference voltage, and supplies this to the input terminal of the comparison amplifier 17. Thus, the speed of the rotary filter 12 can be controlled according to the change in the luminance signal level.

Next, the operation of the apparatus configured as shown in FIGS. 1 and 2 will be described with reference to the timing chart of FIG. In FIG. 2, if the rotary filter 12 is rotated in the illustrated arrow direction, the photo-interrupter 23a, 23b are respectively holes Hs, upon detecting the H _1, Figure 3 start pulse and FIG as shown in (a) ( The read pulse as shown in b) is simultaneously detected. Until this state is further rotated by the light-shielding interval l, the end face of the light guide fiber 5 is shielded from light, and no illumination light is incident during this period as shown in FIG. Then, since the R filter 20 comes to the front position of the fiber 5 after passing the light shielding interval l, the R light is incident on the fiber 5 during this R filter period. When the R filter 20 passes the position of the fiber 5, the hole H ₂ is detected by the photo interrupter 23b, and at that time, the read pulse is output again as shown in FIG. Then, again, the light-shielding interval l
After that, the G filter period comes, and during that period, G light is emitted as shown in FIG. Then, when the G filter period has passed, the hole H ₃ becomes a photo interrupter.
It is detected at 23b and the read pulse is output again as shown in FIG. Similarly, the B filter period arrives again at the light shielding interval l, and during that period, B light is emitted as shown in FIG. After that, the holes Hs and H ₁ are simultaneously detected again by the photo interrupters 23a and 23b, and the start pulse and the read pulse are output again as shown in FIGS.

When a read pulse as shown in FIG. 3 (b) obtained from the photo interrupter 23b is input to the timing generator unit 24 in this way, the timing generator unit 24 causes the solid-state image sensor 3 to read a predetermined number of signals. The reference clock of (1) is taken out from the reference clock generation unit 25 and supplied to the solid-state image sensor 3. Therefore, the read clock signal supplied to the solid-state image sensor 3 is as shown in FIG. 3 (d), and a fixed number of clocks having a constant frequency are generated within the light-shielding period (non-irradiation period) in FIG. 3 (c). It is supplied to the image pickup device 3.

By the way, in FIG. 1, the rotation filter 12 is configured so that its rotation speed is automatically controlled in accordance with the brightness of the object, but the read clock signal has a constant frequency from the time when the read pulse is detected. The predetermined number of clock signals are output from the timing generator unit 24. Therefore, when the rotation speed of the rotary filter 12 increases, the period corresponding to the light-shielding interval l, that is, the light-shielding period required for reading, shortens, and when the rotation speed decreases, the period conversely increases. Therefore, how to set the interval l becomes a problem. If the interval 1 is set narrower with the lower rotation speed as the reference, when the rotation speed is high, the light-shielding period necessary for reading becomes too short, and the rotation imaging element 3 is not completed before the reading period by the reference clock ends. Illumination light is received by
A so-called smear phenomenon occurs, which exceeds the limit of the read capacity of the solid-state image sensor. On the contrary, if the interval l is set wide based on the one having a higher rotation speed, the non-illumination period becomes large, and the circumferential widths of the R, G, B color filters 20, 21, 22 become narrower, so that the illumination period becomes longer. Is limited, and the illumination efficiency, that is, the light receiving rate of the solid-state image sensor 3 is reduced.

In consideration of the above points, even if the light shielding interval l of the rotary filter 12 is narrowed to some extent, if the clock frequency is controlled so as to increase the frequency of the read clock signal as the rotation speed increases, the The signals can be sufficiently read from the image sensor. Next, an apparatus configured to make the frequency of the read clock signal follow the rotation speed of the rotary filter will be described.

FIG. 4 shows a second embodiment of the present invention. Instead of the reference clock generator 25 shown in the apparatus of FIG. 1, a phase comparator 32, a low-pal filter circuit 33, a VCO (voltage controlled oscillator) is provided. ) 2
PLL (phase-locked loop) consisting of 4 and divider 35
A circuit is used, and a clock signal that follows the rotation speed is supplied to the timing generator unit 24. That is, the phase comparator 32 causes the photo interrupter to
The phase of the read pulse from 23 and the output obtained by dividing the output of VCO34 is compared, and the difference voltage corresponding to the phase difference is applied to VCO34 through low pass filter circuit 33, and the frequency of the clock signal oscillated by VCO34 is The frequency of the read pulse can be tracked and changed. Therefore, if the number of rotations of the rotary filter 12 is increased, the generation cycle of the read pulse is also shortened, the frequency of the clock signal output from the VCO 34 is also increased, and this clock signal passes through the timing generator section 24 and is predetermined for each input of the read pulse. , And is output as a clock signal for reading 3 of the solid-state image sensor. When the frequency of the read clock signal is increased, the signal charge accumulated in the solid-state image sensor 3 is read out in a short time, which eliminates the possibility of smearing.

FIG. 5 shows a third embodiment of the present invention, in which a VCO (voltage controlled oscillator) 36 is used in place of the reference clock generator 25 shown in the apparatus of FIG. A clock signal that follows the number of rotations is supplied to the timing generator unit 24 as in the case of. That is, the difference voltage obtained by comparing the luminance signal level output from the low-pass filter circuit 29 and the reference luminance signal level in the comparison amplifier 30 is added to the VCO 36, and the frequency of the clock signal oscillated by the VCO 36 is changed to the luminance signal. The change can be made in accordance with the change in level, that is, the change in the number of revolutions. Therefore, if the number of rotations of the rotary filter 12 is increased, the generation cycle of the read pulse output to the timing generator unit 24 is also shortened, but the luminance signal level output from the low pass filter circuit 29 is lowered and the comparison amplifier 30 outputs a positive signal. Output voltage is VCO3
In addition to 6, the oscillation frequency of VCO36 will rise. As a result, a predetermined number of read clock signals having an increased frequency are output from the timing generator 24 for each input of the read pulse, and the accumulated signal of the solid-state image sensor 3 can be read even within a short light-shielding period due to the increase in the rotation speed. You can

[Advantages of the Invention] As described above, according to the present invention, it is possible to automatically perform light control without deterioration of the light distribution characteristic of the illumination light or deterioration of the spectral characteristic, and moreover, to perform mechanical adjustment as in the conventional case. Since it is not configured to reduce the amount of light, the response speed required for dimming is increased without taking up extra space, and the dimming range that can be imaged can be expanded by the speed control of the rotary filter. There is.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a light amount control device for an endoscope according to the present invention, FIG. 2 is a front view showing the configuration of a rotary filter used in the device of FIG. 1, and FIG. 1 is a timing chart for explaining the operation of the apparatus of FIG. 1, FIG. 4 is a block diagram showing a second embodiment of the present invention, FIG. 5 is a block diagram showing a third embodiment of the present invention, and FIG. 7 is a configuration diagram showing the light source device of FIG. 7, and FIG. 7 is a front view partially showing a diaphragm splash used in the device of FIG. 1 ... End of endoscope, 3 ... Solid-state image sensor 5 ... Light guide fiber 7 ... Illumination means, 8 ... Light source lamp 12 ... Rotation filter for three-color separation 14 ... Drive motor, 15 ... Rotation detector 16,29 …… Low-pass filter circuit 17,30 …… Comparison amplifier 18 …… Servo amplifier, 20 …… Red filter 21 …… Green filter, 22 …… Blue filter 23 …… Photointerrupter 24 …… Timing generator 25: Reference clock generator 27 ... Resistor circuit, 28 ... Switch circuit 31 ... Reference voltage source

Claims (1)

[Claims] 1. A rotary filter that decomposes light from a light source that illuminates an object into three colors in a time series during a light-shielding period, and a solid body that receives an optical image separated into three colors by the rotary filter and converts it into an electric signal. An image sensor, a brightness level detection unit that detects the brightness signal level from the output from the solid-state image sensor and compares it with a reference value, and a rotation speed is detected by the rotary filter, and the detected value and the brightness level are detected. A light quantity control device for an endoscope, comprising: a speed control means for controlling a rotation speed of a rotary filter based on a comparison output from a detection means to adjust an illumination light quantity.