JP2989101B2 - Electronic shutter control device for electronic endoscope - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic endoscope apparatus, and more particularly, to the control contents of a control device for controlling an electronic shutter of a solid-state image pickup device.

[0002]

2. Description of the Related Art An electronic endoscope apparatus has an electronic shutter function for controlling the accumulation time of electric charges serving as pixel information of a CCD (Charge Coupled Device), which is a solid-state imaging device. Exposure control at the time of image formation can be performed in place of ALC (Automatic light control) using an aperture member or the like described above. That is, the ALC detects the luminance of the image signal and controls the amount of incident light with a diaphragm member or the like. In the electronic shutter, based on the luminance information of the image signal, when the image is bright, the accumulation time is short, When is dark, extend the accumulation time,
By controlling the amount of charge stored in the element, an image with optimal brightness can be obtained.

[0003]

However, in the above-described electronic shutter control, a control signal for charge accumulation, that is, a sweep pulse or a read pulse is generated during a blanking period of a horizontal synchronizing signal. When the observation object is bright, there is a problem that exposure control accuracy is reduced and an exposure error occurs.

FIG. 5 is a waveform diagram showing a conventional control operation. In the control device, a horizontal synchronizing signal shown in FIG. 1B is applied during a vertical scanning period (1 V) shown in FIG. ,
For example, 262.5 pieces are generated. If the control signal or the like is formed during the effective period of the horizontal synchronization signal, there is a disadvantage that noise is generated on the image. Therefore, the control pulse of the electronic shutter is formed during each blanking period B of the horizontal synchronization signal. . In the example of FIG. 7C, the sweep pulse Pa is formed from the horizontal synchronization signal 1 to the blanking period B of the horizontal synchronization signal 131 based on the exposure control signal, and the readout pulse Pb is the last blanking period B and the vertical synchronization signal. It is formed during a signal blanking period. Then, as shown in FIG. 3D, the accumulated signal accumulated in each element of the CCD is once swept by the sweep pulse Pa and further accumulated, and the accumulated charge amount shown in FIG. Will be.

FIGS. 1C and 1D show the case where the end of the electronic endoscope is not close to the object to be observed and the exposure time is set to be long. Even if the sweep pulse Pa is output during the blanking period B of the previous horizontal synchronization signal 130 shown by the broken line, the increase in the charge amount 101 has little effect on the charge amount 100. However, as shown in FIGS. (E), (F), and (G), when the tip of the electronic endoscope approaches the object to be observed and the exposure time becomes short, that is, the blanking period of the horizontal synchronizing signal 260 In the sweep pulse Pa generated up to B, the graph 102
As shown in FIG. For this reason, when the charge is accumulated after the sweep pulse Pa of the previous horizontal synchronization signal 259 indicated by the broken line, the increased charge amount 1
03 greatly affects the charge amount 102. Therefore, when close-up shooting is performed, the exposure accuracy in the electronic shutter control is deteriorated, and an exposure error is increased as compared with the case where close-up shooting is not performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to improve the accuracy of exposure control and achieve good photographing even when the intensity of incident light is high in close-up photographing or the like. Another object of the present invention is to provide an electronic shutter control device for an electronic endoscope.

[0007]

In order to achieve the above object, the present invention relates to an electronic endoscope apparatus for forming an image signal by controlling an electronic shutter of a solid-state image pickup device, wherein an incident light intensity is higher than a predetermined value. When high, a mask circuit for forming a mask of a predetermined width at least in the vertical direction outer periphery of the monitor screen is provided,
When the incident light intensity is lower than a predetermined value, a control pulse for the electronic shutter is formed by the driving pulse generated during the blanking period of the horizontal synchronization signal, and when the incident light intensity is higher than the predetermined value, the above-described mask circuit is used. A driving pulse is generated within a valid period of a horizontal synchronization signal in a masked area, and a control pulse for an electronic shutter is formed by the driving pulse.

[0008]

According to the above arrangement, when the incident light intensity is higher than a predetermined value, a driving signal pulse is generated not only during the blanking period of the horizontal synchronizing signal but also within the effective period. 256 (8-bit configuration) pulses are formed in the pulse horizontal synchronization signal. Then, a control pulse such as a sweep pulse or a read pulse is formed by the high-density signal pulse and the exposure control signal, whereby the electronic shutter operation is performed. At the same time, a mask is inserted in a region where a driving pulse is generated within the effective period of the horizontal synchronization signal.

That is, when the object to be observed becomes relatively bright in close-up photography or the like, exposure control is performed at the end of the vertical scanning period (at the lower side of the screen). On the other hand, when forming a mask,
Since the image signal in the mask insertion region is removed, the image is not adversely affected in this mask region even if the control pulse is used during the effective period of the horizontal synchronization signal. Therefore, at least the lower mask region is formed,
In this area, a control pulse is formed even during the effective period of the horizontal synchronizing signal. Therefore, when the accumulation time becomes short in close-up photography or the like, high-precision exposure control is performed, and a good image can be obtained.

[0010]

FIG. 1 shows the configuration of an electronic shutter control device according to an embodiment. A CCD 10 is disposed at the tip of an electronic endoscope, and this tip has irradiation light for photographing. Is supplied from the light source unit into the body cavity or the like. The CCD 10 includes a signal processing circuit 11 for performing processing such as amplification and gamma correction.
The signal processing circuit 11 is connected to an A / D converter 12 for converting a video signal into an analog signal.
A level comparator 14 for determining the brightness of an image and a PWM (pulse width modulation) signal generating circuit 15 are connected to a stage subsequent to the A / D converter 12. Compare with the video level setting value,
A current incident light intensity is determined. The PWM signal generation circuit 15 forms an exposure control signal having a width based on the output of the level comparator 14, and the charge accumulation time of the CCD 10, which is the exposure time, is determined by the exposure control signal.

In the subsequent stage of the PWM signal generating circuit 15,
Mixer 1 for electronic shutter control other than close-up photography
6 are provided. In addition, the device has a C
A CD timing generator 18 is provided, and a driving pulse generated for each blanking period of the horizontal synchronizing signal is supplied from the timing generator 18 to the mixer 16. Therefore, the drive pulse and the exposure control signal form a shooting pulse (substrate pulse) Pa for shooting that is not in the close state.

On the other hand, for controlling close-up photography, a monostable multivibrator having a variable resistor 20 (monomulti)
21, an AND circuit 22, a mixer 23, and a frequency dividing circuit 24 for obtaining a pulse having a frequency f1. The mono multi 21 is a CCD timing generator 1
A switching position signal for switching to electronic shutter control for close-up photographing is formed based on the vertical synchronization signal VD input from 8. That is, the switching position signal is a signal for setting the switching position E, as shown in FIG. 4B described later, and a signal corresponding to a mask position for generating a mask in the vertical scanning direction. This switching position E
Is a variable resistor 2 corresponding to a predetermined value of the incident light intensity.
When the exposure control signal exceeds the switching position E, a close-up photographing state is set when 0 is set at an arbitrary position (for example, the 250th horizontal synchronization signal of 262.5).

The AND circuit 22 receives an exposure control signal from the PWM signal generating circuit 15 and a switching position signal from the mono-multi 21 described above. The AND circuit 22 determines whether or not close-up photography has been performed. (Whether it is in a state of outputting a high-density sweep pulse). That is, the AND output means a state in which the exposure control signal exceeds the switching position or a state in which the sweep pulse is used in the mask area. The output of the AND circuit 22 is supplied to the mixer 23. On the other hand, in the frequency dividing circuit 24, as shown in FIG. 2, 256 times between one horizontal synchronizing signal (1H) in FIG.
A number of driving pulses (8-bit configuration) are formed. Therefore, when both the drive pulse and the AND output signal are output, the mixer 23 forms the sweep pulse Pa for close-up photography.

The output line of the A / D converter 12 includes:
The mixer 26 and the mask circuit 27 are connected. The mask circuit 27 masks an outer peripheral portion of the screen based on the vertical synchronization signal VD and the horizontal synchronization signal HD input from the CCD timing generator 18. Is formed. The mask signal is supplied to the mixer 2
6 is added to the video signal output from the A / D converter 12. In the embodiment, as shown on the monitor screen 50 in FIG. 3, a mask M1 leaving a substantially circular image display portion shown in FIG. M2 is applied. That is, the mask M2 is obtained by adding a mask having a width D to the upper and lower sides of the screen 50 in the vertical scanning direction of the mask M1, whereby an image area for outputting a control pulse within the effective period of the horizontal synchronizing signal is formed. Completely shielded. It should be noted that the vertical mask may be displayed only on the lower side (at least the lower side mask may be present).

The embodiment has the above configuration, and its operation will be described with reference to FIG. The switching position signal output from the mono-multi 21 in the vertical synchronization signal of FIG. 4A is the signal of FIG. 4B. First, when the tip of the electronic endoscope is not close to the object to be observed, the luminance signal (incident light intensity) is not high. For example, the exposure control signal S1 shown in FIG. Signal generation circuit 15
Output from The exposure control signal S1 is supplied to the mixer 16
At the same time, the signal is also supplied to the AND circuit 22, but this AND circuit 22 does not satisfy the AND condition with the switching position signal of FIG. 4B, so that only the mixer 16 operates. .

In the mixer 16, the driving pulse shown in FIG. 4D output from the timing generator 18 and the exposure control signal S1 are mixed to form a sweep pulse Pa shown in FIG. 4E. , CCD10. Therefore, in this case, the charge amount 110 shown in FIG. 4 (F) is accumulated and read out as an image signal.

On the other hand, the tip of the electronic endoscope is close to the object to be observed, and exceeds the switching position E (the intensity of the incident light exceeds the predetermined value) as shown in FIG. 4) When the exposure control signal S2 is output, the AND condition is satisfied by the switching position signal of FIG. 4B in the AND circuit 22 of FIG. 1, and the mixer 23 operates. At this time, since the driving pulse shown in FIG. 3B is input to the mixer 23 from the frequency dividing circuit 24, as shown in FIG. The driving pulse formed within the effective period of the horizontal synchronizing signal is output to the mixer 16. As a result, the mixer 16
4A, the sweep pulse Pa shown in FIG.
10. Therefore, in the case of close-up shooting in which the incident light intensity is larger than a predetermined value, finer sweep control is performed, and a highly accurate exposure operation can be performed by the electronic shutter operation, as compared with the case where the incident light intensity is small. Errors can be eliminated.

At the same time as the above operation, the AND circuit 2
The AND output of 2 is supplied to the mask circuit 27, and the mask M2 shown in FIG. 3B is displayed during close-up photography. Therefore, as shown in FIG.
The driving pulse (H) is output within the lower mask width D, and a signal like the waveform 201 is mixed in the video signal waveform 200, but adversely affects the video signal in the image display area. Never.

In the above embodiment, an example has been shown in which the sweep pulse is output during the effective period of one horizontal synchronizing signal, and the read pulse is output during the blanking period. For example, it is possible to reverse the relationship between the sweep pulse and the read pulse, output the sweep pulse during the blanking period of the vertical synchronization signal, and output the read pulse during the valid period of the vertical synchronization signal. .

[0020]

As described above, according to the present invention,
When the incident light intensity is higher than a predetermined value, a mask circuit for forming a mask having a predetermined width is provided at least on the outer periphery in the vertical direction of the monitor screen, and when the incident light intensity is lower than the predetermined value, the mask circuit is generated during a blanking period of a horizontal synchronization signal. A sweep pulse for the electronic shutter is formed by the drive pulse thus generated, and when the incident light intensity is higher than a predetermined value, the sweep pulse is formed within a valid period of the horizontal synchronizing signal in the area masked by the mask circuit. Therefore, in close-up shooting or the like, the accuracy of exposure control can be increased as compared with other shooting, and a favorable image display without exposure errors as a whole can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an electronic shutter control device for an electronic endoscope according to an embodiment of the present invention.

FIG. 2 is a diagram showing a driving pulse formed within a valid period of a horizontal synchronization signal.

FIG. 3 is an explanatory diagram showing a mask area according to the embodiment.

FIG. 4 is a signal waveform diagram showing an operation of the example.

FIG. 5 is a waveform chart showing an operation in a conventional electronic shutter control device.

[Explanation of symbols]

 10: CCD, 11: Signal processing circuit, 14: Level comparator, 16, 23, 26 ... Mixer, 18: CCD timing generator, 20: Level comparator, 21: Monostable multivibrator, 22: AND circuit, 24: frequency dividing circuit, 27: mask circuit.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) A61B 1/00-1/32

Claims (1)

(57) [Claims] 1. An electronic endoscope apparatus for forming an image signal by controlling an electronic shutter of a solid-state imaging device, wherein a mask having a predetermined width is formed at least in a vertical direction outer periphery of a monitor screen when an incident light intensity is higher than a predetermined value. To provide a mask circuit
When the incident light intensity is lower than a predetermined value, a control pulse for the electronic shutter is formed by the driving pulse generated during the blanking period of the horizontal synchronization signal, and when the incident light intensity is higher than the predetermined value, the above-described mask circuit is used. An electronic shutter control device for an electronic endoscope, wherein a driving pulse is generated within a valid period of a horizontal synchronization signal in an area to be masked, and a control pulse for an electronic shutter is formed by the driving pulse.