JPH03289928A - Light source light quantity control device of electronic endoscope - Google Patents

Abstract

PURPOSE:To control the quantity of illuminating light for keeping the best image pickup conditions by outputting a signal of a specified field from a solid state image pickup element, adding a signal obtained by delaying the above signal thereto, and inputting the same to an automatic light quantity control circuit. CONSTITUTION:When a signal of B field having the lowest sensitivity is output from a solid state image pickup element, an enabling signal is input from a B enabling signal input terminal 38 to a gate pulse circuit 35, whereby a gate is opened and each pixel signal of the B field is fed into a pixel delay circuit 36. An input signal is delayed for the half pixel and output. The delayed signal is added to a signal not delayed in an addition circuit 37 and input to a low-pass filter 31, so that high-frequency component is eliminated and subjected to designated signal processing by a correction circuit 33 through a clamp circuit 32. The signal is input to ALC as a fixed level light quantity control signal together with the respective image field signals of R and G, whereby the operation of a diaphragm driving mechanism according to a signal from the ALC is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a light source light amount control device in an electronic endoscope apparatus for controlling the light source light amount of an electronic endoscope.

[Prior Art] An electronic endoscope device generally includes an endoscope that has an imaging means made of a solid-state imaging device such as a CCD built into the distal end of an insertion section;
The camera is configured to include a processor that processes the output signal from the solid-state image sensor to generate a video signal, and a monitor device that displays a color image of the subject based on the video signal output from the processor. Furthermore, since the endoscope is inserted into a dark place such as inside the human body, it is necessary to illuminate the area to be observed. For this purpose, a light source device is provided, and the illumination light from this light source device is emitted from the distal end of the insertion portion via a light guide.

As mentioned above, in order to display the subject image as a color image, it is necessary to acquire image signals of each color of R (red), G (green), and B (blue), but unlike an endoscope, it is necessary to obtain image signals of each color. Due to the demand for miniaturization, the imaging means built into the narrow-diameter insertion section is composed of a single solid-state imaging device. Moreover,
In this way, in order to improve the resolution of an image captured by a single solid-state image sensor, a method of driving the solid-state image sensor in a frame-sequential manner has been adopted. This field-sequential drive method uses elements to sequentially form R, G, and B color images as field signals in time series, and then superposes these three color image field signals to create a color video signal. .

For this purpose, a rotating color filter disk is interposed in the optical path of the illumination light from the light source lamp in the light source device, and three filter regions are formed in the color filter disk to transmit each wavelength light of R, G, and B. Then, the color filter is rotated so that each of the R, G, and B filter regions sequentially faces the illumination optical path, thereby sequentially illuminating with R, G, and B wavelength light.

In the case of performing the above-mentioned R, G, B sequential illumination,
It is necessary to adjust the amount of illumination light depending on the region to be observed. That is, when observing a position far from the tip of the insertion tube, the amount of light reflected from the subject decreases and the image displayed on the monitor screen becomes dark, so the amount of light from the light source must be increased. On the other hand, when observing a position close to the tip of the insertion section, the amount of reflected light increases, so it is necessary to reduce the amount of light from the light source to a certain extent to prevent the solid-state imaging device from becoming saturated. Therefore, by interposing a light amount diaphragm member in the middle of the optical path from the light source lamp to the light guide and adjusting the amount of light from the light source according to the area to be observed, the amount of light received by the solid-state image sensor can be kept almost constant. is controlled. In order to control the amount of light from the light source by this light amount diaphragm member, an automatic light amount control circuit (
ALC) is provided.

This ALC extracts the luminance information from the video signals of each color of R, G, and B that are input to the processor from the solid-state image sensor, and when the video signal level is higher than a predetermined reference value, the light amount diaphragm member The aperture is driven to make the aperture aperture smaller and the amount of illumination light is reduced to prevent saturation of the solid-state image sensor, and if the value is lower than the reference value, the aperture is opened to prevent the image from becoming dark. This allows you to take photos under the best lighting conditions.

[Problem to be solved by the invention] However, even under illumination with the same amount of light, R, G,
The video levels of each B video signal are not necessarily equal. That is, R, G, B on the color filter disk
Because the transmittance of each wavelength of light is not constant and there are differences in the sensitivity characteristics of the solid-state image sensor, the level of the video signal in each field of RlG and B from the solid-state image sensor is not constant. . In particular, the signal level of the B (blue) field is about half of the signal level of the R (red) field. Therefore, if the video signals of these R, G, and B fields are input as they are to the ALC, the operation of the ALC becomes unstable and the best illumination conditions cannot necessarily be created.

The present invention has been made in view of the above-mentioned points, and its purpose is to automatically adjust the video signals of the RlG and B fields to almost the same level for a white subject. To provide a light source light amount control device capable of controlling to create and compare the best illumination conditions in a stable state by inputting a light amount adjustment signal to a light amount control circuit. It is in.

[Means for Solving the Problems 1] In order to achieve the above-mentioned object, the present invention provides a signal obtained by delaying a signal of a specific field among field sequential signals output from a solid-state image sensor. The output signal is added to the automatic light amount control circuit that controls the aperture of the light amount diaphragm member in the light source device, and the incident light amount of the light guide is controlled based on this output signal. It is characterized by its structure.

[Function] By adopting such a configuration, it becomes possible to equalize the level of multiple field sequential signals output from the solid-state image sensor for a white subject, and as a result, the operation of the automatic light amount control circuit can be adjusted. In addition to stabilizing the image, it is also possible to control the amount of illumination light to maintain the best imaging conditions.

[Embodiment 1] Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

First, Fig. 1 shows the overall configuration of the electronic endoscope device, and Fig. 2 shows the overall configuration of the electronic endoscope device.
The figure shows the schematic configuration of the illumination system and image signal processing system.

Reference numeral 1 indicates an endoscope, 2 indicates a control device, and 3 indicates a monitor device. The endoscope 1 is provided with a CCD 10 as a solid-state image sensor at the distal end portion of its insertion portion 1a. Also,
The control device 2 includes a processor 4 for processing video signals from the CCD 10 and an illumination system 5 for illuminating an observation target such as the inside of a body cavity.

The CCD 10 is provided at the tip of the insertion section of the endoscope together with a lens 12 attached to the output end 11a of a light guide 11 that transmits illumination light. Therefore, under illumination by the illumination light from the light guide 11, an image of the observation target area can be captured by the CCD 10. The lighting device 5 has a light source lamp 13,
The illumination light from the light source lamp 13 is passed through the light amount diaphragm member 14.
The light enters the incident end 11b of the light guide 11 via the condensing lens 15 and the color filter disk 16.

The processor 4 receives R2O output from the CCD 10,
It has a video signal processing circuit 21 that processes CCD output video signals of each color of B, and the video signals of each color of R, G, and B processed by the video signal processing circuit 21 are converted into digital signals by an A/D converter 22. It is then converted into a file and stored in the field memory 23. Then, when a video signal for one field is input to this field memory 23, the signals of R2O and B are simultaneously read out and sent through D/A converters 24R, 24G, and 24B. The signals are converted into analog signals, mixed by an encoder 25, and output as color video signals.

As already explained, when photographing inside a body cavity, etc., there are cases in which images are taken of a region close to the tip of the insertion section of the endoscope, and cases in which images are taken of a region far from the tip of the insertion tube. Therefore, it is necessary to change the amount of illumination light that enters the incident end 11b of the light guide 11 from the light source lamp 13. For this purpose, the light amount diaphragm member 14 is configured as a variable diaphragm, and the amount of aperture by the light amount diaphragm member 14 is changed in accordance with changes in the brightness level of the output video signal from the CCD 10.

An ALC 26 is provided to drive the light amount diaphragm member 14. This ALC 26 has an aperture drive mechanism 27 equipped with a servo mechanism for driving the light amount aperture member 14, and inputs each R, G, and B CCD output video signal from the CCD 10 to the video signal processing circuit 21. Based on this, a drive signal for the aperture drive mechanism 27 is obtained.

However, when the amount of illumination light emitted from the illumination device 5 side, that is, the light source lamp 13, is constant, there is a difference in the transmittance of the color filter disk 16 for the R, G, and B wavelength region light. Further, depending on the structure of the light amount diaphragm member 14, the amount of light of each wavelength of R, G, and H may not be constant. Furthermore, the sensitivity in C0DIO is not uniform depending on the R, G, and B wavelength light.

In this way, the output signal of the CCD 10 has a large difference in signal amplitude level for each of the R, G, and B fields. Therefore, in the present invention, after first correcting the difference in amplitude level in each field signal, a control signal for the ALC 26 is obtained based on this correction signal.

Before explaining the correction mechanism of this signal, CCD10
Consider the structure of Here, a frame transfer CCD is shown in FIG. 3 as a typical CCD 10.

This CCD is composed of a light receiving section P consisting of a large number of light receiving element groups formed in an island shape, a storage section S and a horizontal transfer section H consisting of a group of elements arranged similarly to the light receiving section P. The signal charges are accumulated in each light-receiving element P by exposing to light, the accumulated signal charges are transferred to the accumulation section S during the vertical blanking period, and the accumulated signal charges are transferred to the accumulation section S during the signal charge accumulation period of the next frame. The signal charges accumulated in are sequentially transferred to the horizontal transfer section H, and the signal charges are read out.

In order to read signals from the horizontal transfer section H, drive pulses φH1+φH2 and reset pulse φ for horizontal transfer are used.
H is applied to the horizontal transfer section H. That is, FIG. 4(a)
And as shown in (b), a drive pulse φH having H and L pulse widths of 70 ns.

(or φH2) and a reset pulse φH having a pulse width of 10 to 40 ns to the horizontal transfer section H, a CCD output signal waveform as shown in FIG. 4(c) is obtained.

This CCD output signal waveform includes a turf signal DS for several pixels (usually about 8 pixels), and then an image signal, ie, a pixel signal, for each pixel constituting the CCD is output.

Here, looking at the output waveform of the pixel signal, first a waveform corresponding to the reset pulse φH is generated, then the period A-B becomes a foot-through period in which the signal output is missing, and when it reaches time B, After the signal output starts, the output signal level becomes almost constant during the CD period after the rising period between B and C, and until the next reset pulse φH is input.

Therefore, each time the reset pulse φH is applied, a pixel signal for one pixel is output, and this pixel signal consists of a foot-through period and a signal output period.

Therefore, by repeatedly applying drive signal pulses φH1, φH2, and φH to the water turbine transfer unit H, signals are transferred from the horizontal transfer unit H. Then, when the pixel signal from the horizontal transfer unit H is transmitted to the processor, this signal is amplified and passed through a low-pass filter.
A signal with high frequency components removed, as shown in Figure (d), is obtained.

Therefore, in the present invention, due to the sensitivity characteristics of the CCD 10, the B field pixel signal with a low signal amplitude level is added to the previous pixel signal, so that the R
, G, and B field signals so that they are approximately the same level, and then input them to the ALC 26.
With this, the light intensity adjustment by the ALC 26 is kept stable, and the illumination light intensity is controlled to provide the best imaging conditions.

The mechanism for adjusting the CCD output signal level will now be explained based on FIG.

In the figure, 10a is a CCD output terminal for a frame-sequential video signal from a solid-state image sensor, 30 is a Yumitsuta follower circuit, and 3
1 is a low-pass filter, 32 is a clamp circuit, 33 is γ
The correction circuits are shown respectively. Each field signal output from the CCD output terminal 10a is sent to an emitter follower circuit 30.
After that, high frequency components are removed by a low-pass filter 31, and predetermined signal processing is performed by a γ correction circuit 33 via a clamp circuit 32.

Here, among the output signals from the solid-state image sensor, the signal adding means 3
4, the delayed signals are added and input to the low-pass filter 31. This signal addition means is composed of a gate pulse circuit 35, a pixel delay circuit 36, and an addition circuit 37.

Therefore, when a B field signal is output from the solid-state image sensor, the enable signal is input from the B enable signal input terminal 38 to the gate pulse circuit 35 to open the gate, and each pixel signal of the B field is input to the gate pulse circuit 35. or is fed into the pixel delay circuit 36. The pixel delay circuit 36 delays the input signal by approximately half a pixel and outputs the delayed signal. The thus delayed signal is added to the non-delayed signal in the adder circuit 37, and this added signal is input to the low-pass filter 31.

Thus, the signal read out from the horizontal transfer section of the solid-state image sensor becomes as shown in FIG. This signal is shown in Figure 4 (
It is the same as the signal in C). Here, reset pulse φH
The time interval from the rise of t to the foot-through period in which the signal output is missing is the time interval t of the signal output period.
It is almost equal to 2. Therefore, the signal from the CCD output terminal 10a is delayed by the time t+ (=t2) by the pixel delay circuit 36. As a result, the pixel delay circuit 36 outputs the waveform signal shown in FIG. 2(b). This delayed signal (b) is added to the signal (a) that does not pass through the pixel delay circuit 36 in an adder circuit 37. As a result, as shown in FIG. 5C, in each pixel signal constituting the field signal, the signal output is interpolated by the previous pixel signal during the missing foot-through period. When this signal (C) is input to the low-pass filter 31 and smoothed, the signal shown in FIG. 3(d) is obtained. Therefore, the amplitude level I2 of this signal (d) is approximately twice as large as the amplitude level 11 of the signal in FIG. 4(d) which is not subjected to addition processing.

In this way, among the signals output from the solid-state image sensor,
The amplitude level of the B-field signal can be increased by adding only the B-field signal, which has the lowest sensitivity, approximately equal to the R-field signal. On the other hand, while other R field and G field signals are being transmitted, the gate pulse circuit 35
Since the gate in is closed, the low-pass filter 3 is directly applied without performing the addition process described above.
Sent to 1. As a result, the signal levels in the three fields of R, G, and B are well balanced.

Therefore, by adding the B field signal in this way and inputting it as a light amount control signal from the pressure stage of the clamp circuit 32 to the ALC 26 together with the R and G image field signals to which the signal is not added, this light amount control signal can be obtained. The amount of illumination light is adjusted so that the level of the light is kept constant, the operation of the diaphragm drive mechanism 27 based on the signal from the ALC 26 is stabilized, and the best and most stable video signal is obtained. You will be able to do this.

[Effect of the Invention 1] As explained above, according to the present invention, the output signal level caused by the sensitivity characteristics of each color image field in a solid-state image sensor is effectively corrected, and the automatic light amount control device can control the light amount. You will be able to input signals,
By stabilizing the light amount control operation by this automatic light amount control device and stabilizing the image displayed on the monitor device,
The amount of illumination light can be controlled to achieve the best shooting conditions.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is an overall configuration diagram of an electronic endoscope device, FIG. 2 is an explanatory diagram showing a schematic configuration of its illumination system and image signal processing system, and FIG. 3 4 is a schematic configuration diagram of a solid-state image sensor, and FIG. 4 is an explanatory diagram of a video signal when no addition processing is performed. FIG. A waveform diagram of the reset pulse, (c) is an output waveform diagram of the solid-state image sensor,
Figure 5 (d) is an output signal line diagram of the low-pass filter, Figure 5 is an explanatory diagram of the main part configuration of the video signal processing circuit including the signal addition means, and Figure 6 is an illustration of the video signal when performing addition processing. The figure (a) is the output signal waveform diagram of the solid-state image sensor, the figure (b) is the output waveform diagram of the delay circuit, the figure (c) is the waveform diagram of the addition signal, and the figure (d) is the waveform diagram of the output signal of the delay circuit. is an output signal waveform diagram of a low-pass filter. 1: Endoscope, 2 Control device, 4: Processor, 5: Illumination device, 10: CCD, 10a: CCD output terminal, 11 Light guide, 13: Light source lamp, 14: Light amount diaphragm member, 16 Dichroic filter Disk, 21: Video signal processing circuit, 26: ALC127: Aperture drive mechanism, 30: Emitter follower circuit, 31: Low pass filter, 32': Clamp circuit, 34: Signal addition means, 35: Gate pulse circuit, 36: Vixel delay Circuit, 37: Addition circuit, 38
:B enable signal input terminal. Figure 1 Figure 2

Claims (1)

[Claims] An endoscope with a solid-state image sensor built into the tip of the insertion section, a light source device that irradiates illumination light toward a subject via a light guide provided in the endoscope, and from the solid-state image sensor of the endoscope. A signal obtained by delaying this signal to a signal of a specific field among the field sequential signals output from the solid-state image sensor in an endoscope apparatus having a processor that processes the output signal of is added by a signal addition means, and the output signal is input to an automatic light amount control circuit that performs aperture control of a light amount diaphragm member in the light source device, and the incident light amount of the light guide is controlled based on this output signal. A light source light amount control device in an electronic endoscope device, characterized in that: