JPH0738845B2 - Light source light amount control device in electronic endoscope device - Google Patents

Description

Description: TECHNICAL FIELD 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] In general, an electronic endoscope apparatus includes an endoscope in which an image pickup unit including a solid-state image pickup device such as a CCD is built in at a tip of an insertion portion, and an output signal from the solid-state image pickup device is processed. It is configured to include a processor as a video signal and a monitor device for displaying a color video of a subject based on the video signal output from the processor. In addition, since the endoscope is inserted into a dark place such as a human body, it is necessary to illuminate a region to be observed. To this end, a light source device is provided, and the illumination light from this light source device is emitted from the tip of the insertion portion via the light guide.

As described above, in order to display a subject image as a color image, it is necessary to acquire image signals of each color of R (red), G (green), and B (blue). The image pickup means built in the insertion part having a small diameter is composed of a single solid-state image pickup device in order to reduce the size. Moreover, as described above, in order to improve the degree of image of the image acquired by one solid-state image sensor, a method of driving the solid-state image sensor sequentially is adopted. In this field sequential driving system, R, G, and B color images are sequentially formed as field signals by elements in a time-sequential manner, and image field signals of these three colors are superposed to form a color video signal. .

For this purpose, a rotary color filter disc is interposed in the optical path of the illumination light from the light source lamp in the light source device, and three color filter regions for transmitting R, G, and B wavelength lights are formed in the color filter disc. Then, the color filter is rotated so that the R, G, and B filter regions are sequentially exposed to the illumination optical path, so that the R, G, and B wavelength lights are sequentially illuminated.

When performing the above-described sequential illumination of R, G, and B, it is necessary to adjust the light amount of the illumination light according to the site to be observed. That is, when observing a position far from the tip of the insertion portion, 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 portion, the amount of reflected light becomes large, so to prevent the solid-state image sensor from being saturated,
It is necessary to reduce the light amount of the light source to some extent. Therefore, by interposing a light amount diaphragm member at an intermediate position of the optical path from the light source lamp to the light guide and adjusting the light amount of the light source according to the site to be observed, the light receiving amount of the solid-state imaging device is made substantially constant. Have control. Then, in order to control the light amount of the light source by the light amount diaphragm member, an automatic light amount control circuit (AL
C) is provided.

This ALC is input to the processor from the solid-state image sensor.
When the brightness information of the R, G, and B video signals is extracted, and when the video signal level is higher than a predetermined reference value, the light amount diaphragm member is driven to reduce the diaphragm aperture and illuminate. The amount of light is reduced to prevent saturation of the solid-state image sensor, and when the value is lower than the reference value, the aperture is opened to maintain the image so that it does not become dark so that the image is captured under the best lighting conditions. I am able to do it.

[Problems to be Solved by the Invention] By the way, even under illumination with the same amount of light, the image levels of the R, G, and B image signals are not equal. That is, since the transmittance of light of each wavelength of R, G, B in the color filter disk is not constant, and there is a difference in the sensitivity characteristic of the solid-state image sensor, R from the solid-state image sensor,
The level of the video signal in each field of G and B is not constant. In particular, the signal level of the B (blue) field is about half that of the R (red) field.
Therefore, if the video signals of the R, G, and B fields are input to the ALC as they are, the operation of the ALC becomes unstable and the best illumination condition cannot always be created.

The present invention has been made in view of the above points, and an object of the present invention is to adjust a video signal of each field of R, G, B with respect to a white object so that the video signals have substantially equal levels. An object of the present invention is to provide a light source light amount control device capable of performing control so that the optimum lighting condition can be produced in a stable state by inputting a light amount adjustment signal to an automatic light amount control circuit. .

[Means for Solving the Problems] In order to achieve the above-described 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. After being added by the signal adding means, the output signal is input to an automatic light amount control circuit for controlling the diaphragm 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. The feature is that it is configured.

[Operation] By adopting such a configuration, it becomes possible to make the levels of a plurality of field sequential signals output from the solid-state image pickup device uniform with respect to a white subject, and as a result, the operation of the automatic light amount control circuit can be improved. This makes it possible to stabilize and control the amount of illumination light for maintaining the best imaging conditions.

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

First, FIG. 1 shows the overall configuration of the electronic endoscope apparatus, and FIG.
The schematic configuration of the illumination system and the image signal processing system is shown in the figure.

Reference numeral 1 denotes an endoscope, 2 denotes a control device, and 3 denotes a monitor device, respectively. The endoscope 1 is provided with a CCD 10 as a solid-state image sensor at the tip portion of its insertion portion 1a. In addition, the control device 2
1 has a built-in processor 4 for processing a video signal from a CCD 10 and an illumination system 5 for illuminating an observation target portion such as a body cavity.

The CCD 10 is an emission end 11a of the light guide 11 that transmits illumination light.
It is provided at the tip position of the insertion part of the endoscope together with the lens 12 attached to the. Therefore, under the illumination of the illumination light from the light guide 11, the image of the observation target portion can be captured by the CCD 10. The illumination device 5 has a light source lamp 13, and the illumination light from the light source lamp 13 is incident on the incident end 11b of the light guide 11 via the light amount diaphragm member 14, the condenser lens 15 and the color filter disk 16. It has become.

The processor 4 is a CC for each color of R, G, B output from the CCD 10.
A video signal processing circuit 21 for processing the D output video signal is provided, and the video signals of each color of R, G, B processed by the video signal processing circuit 21 are converted into digital signals by the A / D converter 22. The data is stored in the field memory 23. When a video signal for one field is input to the field memory 23, the R, G and B signals are simultaneously read out and analogized via the D / A converters 24R, 24G and 24B. After being converted into a signal, the encoder 25 mixes them to output a color video signal.

Thus, as described above, when photographing the inside of a body cavity or the like, when photographing a portion near the tip of the insertion portion of the endoscope and when photographing a portion away from the tip of the insertion portion. And, from the light source lamp 13 to the incident end 11b of the light guide 11.
The amount of illumination light incident on must be changed. For this reason, the light amount diaphragm member 14 is a variable diaphragm, and CC
The aperture amount of the light amount aperture member 14 is changed in accordance with the change in the brightness level of the output video signal from D10.

An ALC 26 is provided to drive the light amount diaphragm member 14. The ALC 26 has an aperture drive mechanism 27 having a servo mechanism for driving the light amount aperture member 14, and is based on each CCD output video signal of R, G, B input from the CCD 10 to the video signal processing circuit 21. As a result, a drive signal for the diaphragm 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 wavelength region light of each color of R, G, B of the color filter disk 16, and Depending on the structure of the light amount diaphragm member 14, the light amount of each wavelength light of R, G, B may not be constant. In addition, CC
The sensitivity at D10 is not uniform due to the R, G, and B wavelength lights.

As described above, the output signal of the CCD 10 has a large difference in signal amplitude level between the R, G, and B fields. Therefore, in the present invention, first, the difference between the amplitude levels of the respective field signals is corrected, and then the control signal for the ALC 26 is obtained based on this correction signal.

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

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

In order to read a signal from the horizontal transfer unit H, drive pulses φH ₁ and φH ₂ for horizontal transfer and a reset pulse φH are applied to the horizontal transfer unit H. That is, as shown in FIGS. 4A and 4B, a driving pulse φH ₁ (or φH ₂ ) having a pulse width of H and L of 70 ns and a reset pulse φH having a pulse width of 10 to 40 ns. When and are applied to the horizontal transfer section H,
The CCD output signal waveform as shown in FIG. 4 (c) is obtained. The CCD output signal waveform has a dark signal DS for several pixels (usually about 8 pixels), and after that, image signals, that is, pixel signals at each pixel forming the CCD are output.

Here, looking at the output waveform of the pixel signal, first, a waveform corresponding to the reset pulse φH is generated, and then the period A-B is a field through period in which the signal output is lost. Output is started and BC
The output signal level becomes substantially constant during the CD period until the next reset pulse φH is input after the rising period between them. Therefore, each time the reset pulse φH is applied, a pixel signal for one pixel is output, and this pixel signal includes a field through period and a signal output period.

Therefore, by repeatedly applying the drive signal pulses φH ₁ , φH ₂ , and φH to the horizontal 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 then a signal from which a high frequency component is removed as shown in FIG. 4 (d) is passed through a low pass filter. can get.

Therefore, in the present invention, from the sensitivity characteristics of CCD10,
Pixel signal of B field with low signal amplitude level
Adjust the R, G, and B field signals so that they are at almost the same level by adding the previous pixel signal, and then input them to the ALC26, so that the light intensity adjustment by the ALC26 is stable. Then, control is performed so that the amount of illumination light is such that the best imaging condition is obtained.

The CCD output signal level adjusting mechanism will be described with reference to FIG.

In the figure, 10a is a CCD output terminal for a frame sequential video signal by a solid-state image sensor, 30 is an emitter follower circuit, 31 is a low pass filter, 32 is a clamp circuit, and 33 is a γ correction circuit. Each field signal output from the CCD output terminal 10a passes through the emitter follower circuit 30, the high frequency component is removed by the low pass filter 31, and the clamp circuit 32
Predetermined signal processing is performed by the γ correction circuit 33 via the.

Here, among the output signals from the solid-state image sensor, the signal of the B field having the lowest sensitivity is added by the signal adding means 34.
The delayed signals are added by and input to the low pass filter 31. The signal adding means is composed of a gate pulse circuit 35, a pixel delay circuit 36 and an adding circuit 37. Therefore, when the signal of the B field is output from the solid-state imaging device, the enable signal is input to the gate pulse circuit 35 from the B enable signal input terminal 38 to open the gate, and each pixel signal of the B field. Are sent to the pixel delay circuit 36. The pixel delay circuit 36 delays the input signal by about half a pixel and outputs the delayed signal.
The signal delayed in this way is added to the signal that is not delayed in the adder circuit 37, and this added signal is input to the low-pass filter 31.

The signal read from the horizontal transfer section of the solid-state image sensor is as shown in FIG. This signal is the same as the signal in FIG. 4 (c). Where reset pulse φ
The period interval t ₁ from the rise of H to the field through period where the signal output is missing is the time interval of the signal output period.
It is almost equal to t ₂ . Therefore, this CCD output terminal 1
The signal from 0a is transferred to the pixel delay circuit 36 at time t ₁ (≈
Delay by t ₂ ) minutes. As a result, the pixel delay circuit 36 outputs the waveform signal shown in FIG. This delay signal (b) is added to the signal (a) not passing through the pixel delay circuit 36 in the adder circuit 37. As a result, as shown in FIG. 7C, in each pixel signal forming the field signal, the pixel output immediately before is interpolated in the field through period in which the signal output is missing. When this signal (c) is input to the low pass filter 31 and this signal is smoothed, the signal shown at the same time (d) is obtained. Therefore, the amplitude level I ₂ of this signal (d) is almost doubled as compared with the amplitude level I ₁ of the signal of FIG.

Thus, of the signals output from the solid-state image sensor,
The amplitude level of the signal of the B field can be increased by adding only the signal of the B field having the lowest sensitivity, which is about 1/2 of that of the R field. On the other hand, while the signals of the R field and the G field other than this are being transmitted, the gate pulse circuit 35
Since the gate at is closed, the low-pass filter 31 is used as it is without performing the addition processing described above.
Sent to. As a result, the signal levels in the three R, G, and B fields are well balanced.

Therefore, after adding the signals of the B field in this way, the light amount control signal is input to the ALC 26 from the output stage of the clamp circuit 32 together with the R and G image field signals without adding the signals. It is possible to stabilize the level of the ALC 26, stabilize the operation of the diaphragm drive mechanism 27 based on the signal from the ALC 26, and adjust the illumination light amount so that the best and stable video signal can be obtained. Like

[Effects of the Invention] As described above, according to the present invention, the output signal level generated by the sensitivity characteristic of each color image field in the solid-state imaging device is effectively corrected, and the light amount control signal is input to the automatic light amount control device. Therefore, it is possible to stabilize the control operation of the light quantity by this automatic light quantity control device and stabilize the image displayed on the monitor device.
It is possible to control the amount of illumination light so that the best shooting conditions can be exhibited.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is an overall configuration diagram of an electronic endoscope apparatus, FIG. 2 is an explanatory diagram showing a schematic configuration of an illumination system and an image signal processing system thereof, and FIG. FIG. 4 is a schematic configuration diagram of a solid-state image pickup device, FIG. 4 is an explanatory diagram of a video signal when no addition processing is performed, FIG. 4A is a waveform diagram of a drive pulse for horizontal transfer, and FIG. Reset pulse waveform diagram, (c) is a solid-state image sensor output waveform diagram,
FIG. 6D is an output signal diagram of the low-pass filter, FIG. 5 is an explanatory view of a main configuration of a video signal processing circuit including a signal adding means, and FIG. 6 is an explanatory view of a video signal when performing addition processing. Therefore, FIG. 7A is an output signal waveform diagram of the solid-state imaging device, FIG. 7B is an output waveform diagram of a delay circuit, FIG. 7C is a waveform diagram of an addition signal, and FIG. FIG. 4 is an output signal waveform diagram of a low pass filter. 1: Endoscope, 2: Control device, 4: Processor, 5: Lighting device, 1
0: CCD, 10a: CCD output terminal, 11: light guide, 13: light source lamp, 14: light amount diaphragm member, 16: color filter disc, 21:
Video signal processing circuit, 26: ALC, 27: Aperture drive mechanism, 30: Emitter follower circuit, 31: Low pass filter, 32: Clamp circuit, 34: Signal adding means, 35: Gate pulse circuit, 36:
Pixel delay circuit, 37: Adder circuit, 38: B enable signal input terminal.

Claims (1)

[Claims] 1. An endoscope in which a solid-state image sensor is built in at the tip of an insertion portion, a light source device for illuminating a subject through a light guide provided in the endoscope, and the endoscope. In an endoscope apparatus having a processor for processing an output signal from the solid-state image sensor to obtain a video signal, the signal is delayed to a signal of a specific field among field sequential signals output from the solid-state image sensor. After the signals obtained by the above are added by the signal adding means, the output signal is input to the automatic light amount control circuit for controlling the aperture of the light amount aperture member in the light source device, and the light guide is incident on the basis of this output signal. A light source light amount control device in an electronic endoscope device, which is configured to control a light amount.