JPH11169339A - Automatic light control device for electronic endoscope system - Google Patents

Abstract

(57) Abstract: An electronic endoscope with a simple configuration and capable of performing stable automatic dimming even when there is a period in which a signal output from an imaging element does not include luminance information. To provide an automatic light control device for the system. SOLUTION: CCD (5) for imaging a subject
Light irradiating means (13) for irradiating the subject with light;
An aperture device (12) for driving the aperture mechanism based on the video signal during a period in which the video signal is being output from the imaging element, and the imaging element is not outputting the video signal During the period, the state of the aperture mechanism is maintained in a constant state by feedback control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic light control device for an electronic endoscope system for adjusting the amount of light for illuminating an observation target in the electronic endoscope system.

[0002]

2. Description of the Related Art Conventionally, a CCD (Charge
An electronic endoscope system configured to process a video signal output from a scope unit having a Coupled Device by an image processor to generate a video signal, and display the generated video signal on a monitor device such as a CRT. It has been known.

Normally, an image processor is provided with a light source device for emitting light for illuminating an observation target, and the scope unit transmits light emitted from the light source to the observation target. A light guide (optical fiber bundle) is provided.

Light that has entered the light guide from the light source passes through the light guide and is applied to the observation target, and the reflected light from the observation target is imaged on the light receiving surface of the CCD via an imaging optical system. The image processor stores the video signal received from the scope unit in a memory, converts the video signal into a video signal of a predetermined format (for example, an NTSC or PAL compliant video signal), and converts the video signal into a monitor device connected to the image processor. Output to

[0005] In order to adjust the brightness of the screen displayed on the monitor device, the amount of light incident on the light guide from the light source device is adjusted (light adjustment is performed). An aperture mechanism is provided between the light source device and the light guide to perform dimming. Usually, feedback control is performed so that the brightness of the observation target displayed on the screen of the monitor device is substantially constant. Automatic dimming using is performed.

[0006]

In the automatic light control, a video signal output from a CCD is used as a signal indicating information relating to the luminance of an observation target. That is, the amount of light incident on the light guide from the light source device is adjusted while monitoring the intensity of the video signal. However, the video signal generally has a period that does not include the luminance information signal. The automatic dimming operation in a period in which the luminance information is not included is an unstable operation in which the closed-loop control is substantially interrupted. This is more remarkable as the proportion of the intermittent period (period not including the luminance information) in the video signal is larger, and the automatic dimming in such a situation has to be unstable control.

In view of the above circumstances, the present invention can perform stable automatic light control with a simple configuration even when a signal output from an image sensor includes a period in which luminance information is not included. It is an object to provide an automatic light control device for an electronic endoscope system.

[0008]

In order to achieve the above object, an automatic light control device of an electronic endoscope system according to the present invention receives an optical image of a subject and generates a video signal corresponding to the optical image. An image sensor for outputting, a light irradiating unit for irradiating the subject with light, a diaphragm mechanism for adjusting an irradiation light amount of the light irradiating unit, and a video signal during a period in which the video signal is output from the image sensor. First control means for driving the aperture mechanism based on the second control means, and a second control means for maintaining the state of the aperture mechanism in a constant state during a period when the image sensor is not outputting the video signal, It is characterized by having. That is, based on the video signal output from the image sensor, the automatic dimming mode for keeping the brightness of the subject constant, during the period when no video signal is output from the image sensor,
It is configured to operate in a mode in which the aperture position is fixed (claim 1).

The second control means maintains the state of the aperture mechanism during a period during which the immediately preceding video signal is being output during a period when the image sensor is not outputting the video signal. (Claim 2). During the no-signal period, the initial aperture position of the automatic dimming process in the next video signal period does not deviate significantly from the target position in order to maintain the aperture position during the immediately preceding video signal period. Is performed at high speed.

[0010] The second control means controls the aperture mechanism in a closed loop while the video signal is not being output (claim 3). That is, since the closed-loop control is performed so as to maintain the aperture position instead of simply stopping the motor or the like for driving the aperture, the aperture position does not shift and the operation of the aperture mechanism is stabilized.

The automatic light control device of the electronic endoscope system further includes an image pickup device driving unit for driving the image pickup device, and the first control unit or the first control unit in synchronization with a drive signal of the image pickup device driving unit. The second control means is selectively used (claim 4).

The second control means controls a current state of the aperture mechanism with a target of a state of the aperture mechanism during a period in which the video signal is being output (claim 5). .

In addition, a single-plate type color image sensor can be used as the image sensor. further,
The electronic endoscope system includes a signal generation circuit configured to generate a Y signal, an RY signal, and a BY signal based on a video signal output from the imaging element, and the Y signal, the RY signal, A signal processing circuit that performs predetermined signal processing on a BY signal; the first control means refers to a Y signal output by the signal generation circuit when the diaphragm mechanism is driven; It can be configured to be used as YIRIS (claim 7).

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of an electronic endoscope system 100 according to an embodiment of the present invention.

The electronic endoscope system 100 includes a scope section 7, an image processor 21, and a monitor device 29. The scope section 7 includes an insertion section 4 made of a flexible conduit.
And a CC as a solid-state imaging device
D image sensor 5 (hereinafter abbreviated as CCD) and CCD 5
The objective lens 6 is disposed in front of (the left side in the figure).
Note that the CCD 5 is a so-called single-plate type color CCD, and a color filter is provided on the light receiving surface. An optical image of the observation target (imaging body) is formed on the light receiving surface of the color CCD 5 by the objective lens 6. The light guide 1 made of an optical fiber bundle is inserted through the scope section 7. One end (light emitting end) of the light guide 1 is arranged at the front end (left end in the figure) of the insertion section 4 and irradiates the observation target with light through the light distribution lens 2.

The scope section 7 is detachably connected to the image processor 21 via a connection section 8. Scope part 7
A signal processing device 10 for subjecting the video signal from the CCD 5 to a predetermined signal processing is built in the vicinity of the coupling section 8.
The other end of the light guide 1 reaches the inside of the image processor 21 via the coupling unit 8, and is fixed at a position where the end surface of the light guide 1 faces the condenser lens 11.

The lamp 13 is driven by the lamp power supply 16. The illumination light emitted from the lamp 13 is condensed by the condenser lens 11 in a state where the light amount is adjusted by the aperture mechanism 12 which is a light amount adjusting means, and the light guide 1
Incident on the end face of. The light that has entered the light guide 1 passes through the light guide 1, is emitted from the end face on the distal end side of the insertion section 4, and is emitted toward the observation target via the irradiation lens 2.

The illumination light reflected by the observation target forms an image on the light receiving surface of the color CCD 5 by the objective lens 6. The CCD 5 transmits a color video signal corresponding to the optical image formed on the light receiving surface to the signal processing device 10. As will be described later in detail, the signal processing device 10 drives the CCD 5 and performs various signal processings.
With respect to the luminance signal (Y) and the color difference signals (RY, B-
Y) is output.

The above signal sent to the image processor 21 is input to the preprocessor 22. The two color difference signals (RY, B-
Y) and the luminance signal (Y) are A / D converters 18A, 1
After being input to 8B and 18C, respectively, and converted into digital signals, they are stored in the memory 19 in synchronization with the synchronization signal output from the timing generation circuit 17. After the data stored in the memory 19 is subjected to predetermined image processing such as freeze processing and interpolation processing, the data is read out in synchronization with the TV synchronization signal output from the timing generation circuit 17, and the D / A converter 23A , 23B, and 23C, are converted into analog signals, processed by the signal processing circuit 28, and output to the monitor device 29 as RGB video signals. Monitor device 29
Displays a color image based on the RGB video signal sent from the signal processing circuit 28.

On the other hand, based on a video signal output from the CCD 5, a luminance information signal YIRIS corresponding to the luminance signal Y is provided.
Are generated and output in the signal processing device 10. The luminance signal Y is a signal after various types of signal processing have been performed in the signal processing device. In contrast, the luminance information signal YIRIS
Is a signal obtained by converting a video signal output from the CCD 5 into a signal corresponding to a luminance signal before performing other processing, and has a value closer to the luminance of the observation target. Hereinafter, the activation information signal YIRIS will be described in detail with reference to FIG.

FIG. 2 is a block diagram showing a configuration of the signal processing device 10 built in the scope unit 7. As shown in FIG. The signal processing device 10 includes a driver 102, a timing generator 101,
A matrix circuit 103 and a signal processing circuit 104 are provided.

The timing generator 101 generates a pulse for driving the CCD and outputs the pulse to the driver 102. CCD5
The accumulated charges are output to the signal processing device 10 in synchronization with the CCD driving pulse. The video signal output from the CCD 5 is sampled and subjected to color separation processing by the matrix circuit 103 in synchronization with the timing pulse generated by the timing generator 101, and the color difference signal R
−Y, BY, and a luminance signal Y are output. There is a linear relationship between the intensity of the signal output by the matrix circuit 103 and the intensity of the video signal input to the matrix circuit. That is, the output signal of the matrix circuit 103 and the light receiving level of the CCD 5 are in a proportional relationship. Here, the Y signal is a luminance signal. However, if automatic dimming is performed based on the value of the Y signal, the following inconvenience may occur.

As a video signal, a portion where the voltage output of the CCD 5 with respect to the amount of light received by the CCD 5 falls within a predetermined range is used. Therefore, the next signal processing circuit 104 performs a clipping process to narrow the dynamic range.
Therefore, for example, when the CCD 5 is exposed with high illuminance, the video information may show a state of being saturated at a predetermined level even though the output signal of the CCD 5 itself is not saturated.

For example, when a triangular wave as shown in FIG. 3 is used as the Y signal input of the signal processing circuit 10, the Y signal output of the signal processing circuit 10 becomes a waveform saturated at a predetermined level as shown in FIG.
Some luminance information is lost.

As shown in FIG. 4, when a signal from which luminance information is partially lost is used as a signal for automatic dimming, the feedback function works well when dimming a portion where the signal indicates a saturated state. It is known that the result is that the aperture operation of automatic light control is extremely slowed down as a result.

In addition to the above-described clipping, the signal processing circuit 104 may perform various kinds of signal processing such as γ correction and contour enhancement depending on the use of the image. For example, the waveform obtained by subjecting the input waveform shown in FIG. 3 to γ correction is a waveform having a different amplification factor depending on the luminance signal level as shown in FIG. FIG. 6 is an example of a signal waveform that has been subjected to both clipping and gamma correction.

As described above, when the luminance signal Y output from the signal processing circuit 104 is used as a signal for dimming, the gain of the feedback loop of automatic dimming depends on the luminance signal level which does not directly correspond to the luminance of the subject. And ideal control may not be possible. For example, when automatic light adjustment is performed in accordance with the luminance signal subjected to the γ correction, the automatic light adjustment itself has a γ characteristic. In addition, the response of the dimming is not constant, and when the dimming operation is slow or fast, the result is mixed during the operation, and a stable dimming state cannot be obtained.

The above problem can be dealt with, for example, by adding an inverse γ correction circuit inside the image processor 21. However, incorporating such a circuit inside the image processor 21 complicates the circuit configuration and increases the circuit scale, which leads to an increase in the cost and size of the apparatus.

The signal processing circuit 104 is connected to the scope unit 7
The reason why it is necessary to provide on the side is that, as described above, it is necessary to replace the scope unit coupled to the image processor 21 with various scope units depending on the application. That is, even when a scope unit having a different CCD type or imaging method is used, the scope unit outputs a signal that satisfies a certain standard or specification, thereby maintaining compatibility between various scope units and the image processor. be able to.

As described above, the Y signal output from the matrix circuit 103 reflects the amount of light received by the CCD 5 faithfully. For this reason, in the present embodiment, the luminance signal Y output from the matrix circuit 103 of the scope unit 7 and before being input to the signal processing circuit 104 is separately extracted, and as a luminance information signal YIRIS for automatic dimming, It is configured to output separately from other video signals (the luminance signal Y and the color difference signals RY and BY output from the signal processing circuit).

Since the YIRIS signal faithfully reflects the amount of light received by the CCD 5, by adjusting the amount of light based on the luminance information signal YIRIS, a dimming error can be greatly reduced. Moreover, since the luminance information signal YIRIS is a signal that has not been subjected to clip processing, the range in which the feedback loop can be linearly controlled can be expanded, and high-speed automatic light control can be performed.

The luminance information signal YIRIS is input to the dimming circuit 20 as shown in FIG. The dimming circuit 20 controls the aperture mechanism 12 so that the luminance information signal YIRIS has a predetermined value, thereby adjusting the amount of light applied to the observation target. That is, when the value of the luminance information signal YIRIS is smaller than a predetermined value (when the luminance is low), the light amount is increased, and when the value of the luminance information signal YIRIS is larger than the predetermined value (when the luminance is high). Aperture mechanism 1 so that the light amount decreases.
By controlling and driving the pixel 2, almost constant luminance is always obtained.

Further, when the level of the luminance information signal YIRIS is low and the value indicated by the luminance information signal YIRIS is smaller than a predetermined threshold, a signal indicating that the level of the luminance information signal YIRIS is low is sent to the system controller 27. I do.
When the level of the luminance information signal YIRIS is low, the system controller 27 can send a predetermined command to the signal processing device 10 to change the charge accumulation time of the CCD 5. In the present embodiment, when the luminance of the observation target is relatively high, the CCD 5 is driven in the frame accumulation driving mode. When the luminance of the observation target is relatively low, the CCD 5 is driven in the four-field accumulation driving mode which is the low shutter mode.
D5 is driven. The frame accumulation driving and the four-field accumulation driving will be described later.
The signal processing device 10 outputs a sample / hold control signal synchronized with the drive signal of the CCD 5 to the system controller 27.

FIG. 8 is a block diagram showing a control system for performing automatic light control. As shown in FIG. 8, the aperture mechanism 12 has an aperture 123, a drive motor 122 for driving the aperture 123, and an aperture sensor 121 for detecting the state (aperture value) of the aperture 123. The aperture sensor 121 is a sensor that outputs a voltage value corresponding to the size of the aperture defined by the aperture 123. The light emitted from the lamp 13 enters the condenser lens 11 through the opening of the stop 123 and enters the light guide 1.

The dimming circuit 20 has a first integrator 201 for integrating the luminance information signal YIRIS output by the signal processing device 10 of the scope section 7. The output of the first integrator 201 is applied to the terminal 1 of the first switch SWa. Further, the output voltage of the aperture sensor 121 is changed to the first switch SW.
a is applied to terminal 2. The output voltage of the aperture sensor 121 is also input to the second integrator 202. Second
The sample / hold circuit 2 is connected to the output terminal of the integrator 202.
03 is connected. Sample / hold circuit 203
Is applied to the terminal 2 of the second switch SWb. The terminal 1 of the second switch SWb has a signal processing circuit 2
A predetermined voltage (target voltage) output from the reference numeral 8 is applied.

The switching of the terminals of the first and second switches SWa and SWb is performed in conjunction with a sample / hold control signal for controlling the operation of the sample / hold circuit 203. That is, in the first switch SWa, the terminal 1
Is connected to the output terminal of the switch, the second
The terminal 1 of the switch SWb is in conduction with the output terminal of the second switch. FIG. 8 shows this state. When the state of the sample / hold control signal changes, the terminals 1 of the first and second switches SWa and SWb become conductive with the output terminals of the respective switches.

That is, when the switches SWa and SWb are both set to the terminal 1 side, the negative terminal of the voltage comparator 204 has the integrated value of YIRIS, and the positive terminal has the target voltage value from the system controller 27. Is entered.
When the switches SWa and SWb are both set to the terminal 2 side, the output voltage of the aperture sensor 201 is applied to the negative terminal of the voltage comparator 204, and the output value of the sample / hold circuit 203 is applied to the positive terminal. , Respectively.

The sample / hold control signal is generated in synchronization with the control signal output from the signal processing circuit 10 of the scope unit 7, and is output from the timing generation circuit 17. This operation will be described below.

In FIG. 2, a timing generator 101 sends a control signal to a driver 102 to switch between frame accumulation and field accumulation and to control the timing of charge accumulation. The CCD driver 102 drives the CCD 5 in four phases (V1 to V4) in the vertical direction and two phases (H1, H2) in the horizontal direction.

In a normal operation state (frame driving), an L level signal is output from the comparator 204. At this time, the timing generator 101 outputs a driving mode signal indicating that the driving is performed in the frame accumulation driving mode and the enable signal H, whereby the driver 102
Is synchronized with the vertical synchronizing signal in the frame accumulation driving mode.
Drive CD5. In driving the CCD 5, charge is accumulated for 1/30 seconds for each of the even-numbered and odd-numbered fields, and signal transfer is performed every 1/60 second for the even-numbered and odd-numbered fields (see the frame in the timing chart of FIG. 7). See section on accumulation mode). That is, in a normal operating state,
The shutter speed is 1/30 second, and the output of the video signal is performed every 1/60 second.

When an H level signal is output from the comparator 204 and the system controller 27 determines that the subject brightness is lower than a predetermined value, the system controller 27 sends a predetermined command to the timing generator 101. Is sent. At this time, the timing generator 101
The driving mode of the CCD 5 is set to a two-field accumulation driving mode, and the enable signal H and L are switched at a period of 1/60 seconds (see the four-field accumulation mode in FIG. 7).

Note that when the enable signal is H, CC
Although charge transfer from the light receiving section of D5 to the vertical transfer section is possible, transfer of charge from the light receiving section of the CCD to the vertical transfer section is prohibited when the enable signal is L. At this time, the driving mode is switched to the four-field accumulation driving in which the charge accumulation time is 1/15 second and the pixel signals of the vertically adjacent pixels are alternately added and read (the four-field accumulation driving in FIG. 7). mode). In the case of four-field accumulation driving, the sum of the pixel signals of the n-th pixel and the (n + 1) -th pixel and the sum of the pixel signals of the (n-1) -th pixel and the n-th pixel alternately every 1/15 second. It is output as an even field / odd field signal (although it is actually the sum of the pixel signals of the even and odd pixels).

At the time of frame accumulation, odd / even field signals are 1/60 second at a shutter speed of 1/30 second.
It is output every second, but when four fields are stored, two adjacent pixels in the vertical direction are added and output at the time of charge transfer.
Double.

When four fields are accumulated, the horizontal resolution is reduced. However, as described above, since the sensitivity can be greatly improved, noise mixing and the like can be suppressed as compared with the case where the output of the CCD 5 when driven by frame accumulation is simply amplified using an amplifier.

When the four-field accumulation is performed, as shown in FIG.
5 and a non-output period occur. However, it is necessary to keep sending the video signal to the monitor device 29 in synchronization with the vertical synchronization signal even during the period when the video signal is not output from the CCD 5. In the present embodiment, while the CCD 5 is driven by four fields, a field signal is stored in the memory 19, and is read out repeatedly and output to the monitor device 29. This operation will be described below.

When a command indicating a low-luminance state is transmitted from the system controller 27 to the signal processing device 10, the timing generator 101 outputs an enable signal in which H and L are alternately switched as shown in FIG.

This enable signal is output to the driver 102 and also to the system controller 27 at the same time. The system controller 27 transfers the enable signal received from the timing generator 27 to the timing generation circuit 17. The timing generation circuit 17
A synchronization signal for writing field data to the memory 19 is output only when the enable signal is H, and the field data is not written to the memory 19 when the enable signal is L. Note that a signal for reading data from the memory 19 is output as usual regardless of the state of the enable signal.

Further, the timing generation circuit 17 performs a predetermined process on a signal corresponding to the enable signal received from the system controller 27, and then performs a sampling /
The sample / hold circuit 203 of the dimming circuit 20 is controlled as a hold control signal. That is, the signal processing circuit 10
Indicates that the sample / hold control signal is set to H (high level) only while the CCD 5 is outputting a video signal,
The sample / hold control signal is set to L (low level) during a period in which no video signal is output from.

The first and second switches SWa, S
Wb selects the terminal 1 when the sample / hold control signal is H, and selects the terminal 1 when the sample / hold control signal is L
In this case, the terminal 2 is selected.

The states of the first and second switches SWa and SWb shown in FIG. 8 are in a state where a normal automatic dimming operation for driving the diaphragm 123 based on the luminance information signal YIRIS is performed. is there. At this time, the sample / hold control signal is H. In FIG. 2, the luminance information signal YI
RIS is integrated by the integrator 201 and the first switch S
It is applied to the negative terminal of the comparator via Wa. On the other hand, the target voltage from the system controller 27 is applied to the positive terminal of the comparator 204. The driving circuit 205 includes the comparator 2
The drive motor 122 is driven based on the output from the control unit 04 so that the integrated value of YIRIS approaches the target voltage.
Adjust the aperture of the lens (dimming).

For example, when the observation target is dark, the integrated value of YIRIS is a relatively small value. Then, the comparator 204
The output from is positive. At this time, the drive circuit 205 drives the drive motor 122 in the direction in which the aperture 123 opens. The driving amount of the motor 122 (that is, the amount of change in the opening of the diaphragm 123) is determined based on the difference between the luminance information signal YIRIS and the target voltage.

FIG. 9A shows a luminance information signal YIRIS during normal (in frame accumulation mode) automatic light control, and FIG.
The output waveform of the first integrator 201 at this time is shown in FIG. CC
D5 alternately outputs video signals of odd-numbered and even-numbered fields every 1/60 second, so that continuous dimming can be performed based on the luminance information signal YIRIS. That is,
The luminance information signal YIRIS and a target value output from the system controller 27 are compared in the comparator 204, and based on the comparison result, the drive circuit 205 controls the drive motor 122 to adjust the size of the aperture of the aperture 123.

The luminance information signal corresponding to each frame
There is a period TA during which no luminance information signal is output as shown as a hold period TA in the figure between YIRIS. During this period TA, since the luminance information does not change even when the diaphragm 123 is driven, the feedback system does not operate in the conventional light control device, and the state of the diaphragm 123 is likely to be unstable. However, when the CCD 5 is driven for frame accumulation, the period during which the luminance information is not output is extremely short, so that the driving control of the diaphragm 123 is not significantly affected.

In the present embodiment, since the sample / hold control signal becomes L during the hold period TA, the terminal 2 is selected in both the first and second switches SWa and SWb. At the same time, the sample / hold circuit 203 is also controlled by the sample / hold control signal to sample and hold the value of the integrator 202. Therefore, the output voltage of the diaphragm sensor 121 indicating the position of the diaphragm immediately before the sample / hold control signal changes from H to L is applied to the positive terminal of the comparator 204 via the second switch SWb. The output voltage of the aperture sensor 121 is applied in real time to the negative terminal of the comparator via the first switch SWa. For this reason, a feedback system is configured in which the target position is the position of the diaphragm 123 immediately before the sample / hold control signal changes from H to L.

When the luminance of the observation target is lower than the predetermined luminance, the CCD 5 is driven in a four-field accumulation driving mode (low-speed shutter mode).

FIG. 9C shows an example of the luminance information signal YIRIS output from the signal processing circuit 10 when driven in the low-speed shutter mode (four-field accumulation driving mode). In the example shown in FIG. 9C, the CCD 5 operates for a period (1/15 second) corresponding to four continuous fields,
The control is performed so as to accumulate the electric charge and transfer the electric charge in synchronization with the vertical transfer clock immediately thereafter. Note that FIG.
The sample / hold control signal is output from the signal processing circuit 10 as shown in FIG. 9E in synchronization with the video signal shown in FIG.

When driven by a low-speed shutter (four-field accumulation mode), a normal automatic dimming operation (ie, feedback control based on the luminance information signal YIRIS) is performed while a video signal is being output from the CCD 5. Will be On the other hand, during a no-signal period (that is, a period during which the start information signal YIRIS is not output) TB, the sample / hold control signal is set to L level, and accordingly, the first switch SWa and the second switch SWb are both Switch to terminal 2. At this time, the sample / hold circuit 203
Is driven to sample and hold the output voltage of the aperture position sensor 121 at the end of the output period of the video signal (that is, immediately before the first and second switches SWa and SWb are switched to the terminal 2). The sampled and held voltage is applied to the positive terminal of the comparator 204 as a target voltage, and the current voltage value of the aperture sensor 121 is applied to the negative terminal of the comparator 204 for comparison. Is switched to the servo system that maintains the state at the last stage of the above.

With the above configuration, the aperture 123 during the no-signal period is stabilized in the last dimming state during the video signal output period. That is, during the non-signal period, the dimming circuit operates in the fixed aperture control mode regardless of a change in the video signal.
Therefore, the stop 1
It is possible to prevent a malfunction such that the opening 23 is opened. Moreover, in order to configure a servo system that controls the drive motor 122 so that the current output value of the aperture sensor 121 matches the output value of the aperture sensor 121 at the end of the video signal period, the drive motor 122 is simply stopped. Thus, the position of the stop 123 is more stable.

As described above, even when the CCD 5 is driven for frame accumulation, the aperture control is performed by sampling / holding the aperture value during the period TA during which no luminance information signal is output. Since the non-luminance information signal period at the time is extremely short as described above, it is also possible not to perform servo control during this period.

As described above, according to the present invention, the position of the diaphragm 123 is always controlled by the closed loop control not only in the video signal period but also in the non-signal period. Even in the operation mode in which the period during which no video signal is output is relatively long, the aperture position can be controlled accurately and stably. In addition, in the no-signal period, the closed-loop control is performed so as to maintain the aperture position during the immediately preceding video signal period, so that the initial aperture position of the automatic dimming process in the next video signal period is largely different from the target position. Since it does not deviate, the automatic light control processing is performed at high speed.

In the above-described embodiment, the case of four-field storage drive has been described. However, the present invention is applied to a case where there is a period during which no video signal is output, such as another drive mode, for example, two-field storage drive. This enables stable and high-speed automatic light control processing.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an electronic endoscope system according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a signal processing device built in the scope unit.

FIG. 3 shows a signal processing device with a built-in scope unit.
5 is an example of a waveform input to a signal processing circuit.

FIG. 4 shows a signal processing device with a built-in scope unit.
4 is an example of an output waveform of the signal processing circuit when the waveform of FIG. 3 is input to the signal processing circuit.

FIG. 5 shows a signal processing device with a built-in scope unit.
4 is an example of an output waveform of the signal processing circuit when the waveform of FIG. 3 is input to the signal processing circuit.

FIG. 6 shows a signal processing device with a built-in scope unit.
4 is an example of an output waveform of the signal processing circuit when the waveform of FIG. 3 is input to the signal processing circuit.

FIG. 7 is a timing chart showing timings of frame accumulation and field accumulation of the CCD.

FIG. 8 is a block diagram illustrating a configuration of an automatic dimming circuit.

FIG. 9 is a timing chart showing a drive timing of a CCD and an integrated signal of an output of an aperture position sensor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 electronic endoscope system 1 light guide 2 light distribution lens 4 insertion unit 5 color CCD 6 objective lens 7 scope unit 8 coupling unit 10 signal processing unit 11 condenser lens 12 aperture mechanism 13 lamp 16 lamp light source 17 timing generator 18A, 18B , 18C A / D converter 20 Dimming circuit 23A, 23B, 23C D / A converter 27 System controller

Claims (8)

[Claims] An image pickup device that receives an optical image of a subject and outputs a video signal corresponding to the optical image; a light irradiating unit that irradiates the subject with light; and an irradiation light amount of the light irradiating unit is adjusted. An aperture mechanism; first control means for driving the aperture mechanism based on the video signal during a period in which the video signal is being output from the imaging element; and the imaging element does not output the video signal. During the period,
A second control means for maintaining a state of the diaphragm mechanism in a constant state; and an automatic light control device for the electronic endoscope system, comprising: 2. The apparatus according to claim 1, wherein the second control unit maintains a state of the aperture mechanism during a period when the immediately preceding image signal is being output during a period when the image sensor is not outputting the image signal. The automatic light control device of the electronic endoscope system according to claim 1, wherein: 3. The automatic light control of an electronic endoscope system according to claim 1, wherein the control unit performs closed-loop control of the aperture mechanism during a period in which the video signal is not output. apparatus. 4. The automatic light control device of the electronic endoscope system further includes an image sensor driving unit for driving the image sensor, and the first control is synchronized with a drive signal of the image sensor driving unit. The automatic light control device for an electronic endoscope system according to any one of claims 1 to 3, wherein the control unit or the second control unit is selectively used. 5. The apparatus according to claim 1, wherein the second control unit controls a current state of the aperture mechanism while targeting a state of the aperture mechanism during a period when the video signal is being output. 5. The automatic light control device of the electronic endoscope system according to any one of items 1 to 4. 6. The automatic light control device for an electronic endoscope system according to claim 1, wherein the image pickup device is a single-plate type color image pickup device. 7. A signal generation circuit for generating a Y signal, an RY signal, and a BY signal based on a video signal output from the image sensor, and a Y signal, an RY signal, and a B-signal.
A signal processing circuit that performs predetermined signal processing on the Y signal, wherein the first control unit uses the Y signal output by the signal generation circuit as a luminance information signal YIRIS referred to when the diaphragm mechanism is driven. 7. Use according to claim 6
6. The automatic light control device of the electronic endoscope system according to 4. 8. The automatic light control device of the electronic endoscope system according to claim 7, wherein the signal processing includes gamma correction.