JPH06261326A - Image pickup device using solid-state image pickup element - Google Patents

Abstract

PURPOSE:To obtain the image of high quality by satisfactorily forming an image signal even under various conditions such as in the case when movement exists and the case when a color temperature changes. CONSTITUTION:A movement detection circuit 24 detecting the moving state of a subject, a color temperature setting circuit 28 setting the color temperature and a white balance adjustment circuit 25 are provided. A function selection switch 30 selectively changes over the circuits and the charge accumulation time of CCD 14 is driven/controlled based on the selected circuit. Thus, electronic shutter control corresponding to respective functions is satisfactorily executed. Furthermore, a video amplitude detection circuit is added and an electronic shutter operation is executed by making it correspond to an exchanged electronic endoscope.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus using a solid-state image pickup element, and more particularly to the contents of electronic shutter control of the image pickup apparatus applied to an electronic endoscope, various cameras and the like.

[0002]

2. Description of the Related Art Conventionally, various cameras such as an electronic endoscope using a solid-state image pickup device as an image sensor, that is, a CCD (Charge Coupled Device) and a television camera for observing a narrow place are well known. Then, a color image signal obtained by the CCD is processed and an image is displayed on a monitor or the like. This imaging processing method is a simultaneous method,
There are dot-sequential type and field-sequential type, and in the case of simultaneous type, for example, R (red), G (green), B using a beam splitter or the like.
(Blue) light is separated, and RGB image signals are simultaneously obtained by three CCDs. In the case of the dot-sequential type,
For example, a color filter in which a predetermined color is arranged in a mosaic pattern is C
It is formed on a CD and the CCD simultaneously obtains image signals of a predetermined color. Further, in the case of the frame-sequential system, RGB image signals are sequentially obtained by one CCD on the basis of RGB light that is sequentially irradiated.
Since it can be compactly stored in a CD, it is suitable for an electronic endoscope device or the like that requires a thin insertion tip.

[0003]

By the way, in the above-mentioned conventional image pickup device using a CCD, depending on the condition of the movement of the subject, the conditions of external light, illumination, etc., the conditions of the CCD and the optical system, etc.
There is a problem that a good image signal cannot be obtained. For example, when a subject moves, the resolution is reduced due to the afterimage effect. That is, the CCD accumulates the photoelectrically converted charges for each pixel for a predetermined period and takes out the accumulated charges as an image signal. When the subject moves, the image signal may change during the accumulation period. However, in this case, the resolution is degraded. The faster the movement of the subject, the greater the deterioration of the resolution. Particularly, in the above-mentioned frame sequential image pickup apparatus, RGB image signals are sequentially formed. Therefore, the influence of the movement is greater than that of other apparatuses. growing.

Further, the color temperature changes depending on whether the photographing is performed in the daytime or nighttime, the weather, or the type of the light source when the light source device is provided, which causes a problem that the white balance is lost. Further, in the electronic endoscope apparatus, the scope (electronic endoscope) itself may be replaced and used, and in this case, the white balance is deteriorated due to the optical characteristics of the CCD and the optical system member. Furthermore,
In a frame-sequential device, a color disc is used for R
Each color light of (red), G (green), and B (blue) is irradiated, and an RGB image signal is obtained for each irradiation. Therefore, a difference in level occurs between the RGB image signals due to the difference in sensitivity characteristic with respect to color.
Therefore, in this case, a white crushing phenomenon occurs due to saturation of the R (red) signal, or a state in which faithful color reproduction cannot be performed occurs. This is the same when the RGB light is separated by the beam splitter.

The above white balance can be canceled to some extent by performing white balance processing in the image processing to be performed later on the image signal obtained from the CCD, but this may not be sufficient. Many.

The present invention has been made in view of the above problems, and an object of the present invention is to form an image signal well even under various conditions such as when there is motion and when the color temperature changes.
An object of the present invention is to provide an image pickup apparatus using a solid-state image pickup element capable of obtaining a high quality image.

[0007]

In order to achieve the above object, the invention according to the first aspect uses a solid-state image pickup device provided with an electronic shutter function for controlling the amount of charges accumulated in the solid-state image pickup device. In the conventional imaging device, a motion detection circuit that detects a motion state of a subject, a color temperature correction circuit that corrects a color temperature difference of subject illumination, and a control signal from these circuits drive and control the charge accumulation time of the solid-state imaging device. And an electronic shutter drive circuit for selecting the electronic shutter function corresponding to the above-described motion detection and an electronic shutter function corresponding to the color temperature setting are provided to variably control the electronic shutter corresponding to a plurality of functions. It is characterized by having done.

According to the second aspect of the invention, in addition to the electronic shutter function corresponding to the motion detection circuit and the electronic shutter function corresponding to the color temperature correction circuit, an electronic shutter function corresponding to the white balance adjustment circuit is provided. The feature is that it can be selected. Further, the invention according to claim 3 is an electronic shutter function corresponding to the motion detection circuit,
In addition to the electronic shutter function corresponding to the color temperature correction circuit,
The electronic shutter function corresponding to the signal amplitude detection circuit can be selected. In this case, an electronic shutter function corresponding to the white balance adjustment circuit can be added.

[0009]

According to the above construction, the motion detecting circuit is, for example, G
A moving state is detected from the signal, and at this time, shutter control is performed so that the charge accumulation time in the CCD is shortened. In the case of the color temperature correction circuit, the charge accumulation time is controlled according to the color temperature of the subject illumination, and in the case of the white balance adjustment circuit, the image signal is kept at a constant level when a white subject is photographed. The accumulation time is controlled, and in the case of the signal amplitude detection circuit, the accumulation time is controlled so that the image signal has a constant level when a different electronic endoscope is attached. These controls can be selectively switched, and the electronic shutter function can be activated by the selected circuit according to the subject imaging conditions.

[0010]

1 shows the structure of an image pickup apparatus using a solid-state image pickup device according to the first embodiment.
This is a simultaneous camera device using a single solid-state image sensor (CCD). In the figure, a lens system 11 and a diaphragm 12 are provided in a color separation optical system 10, and a diaphragm driving circuit (which constitutes an ALC circuit) 13 is connected to the diaphragm 12. In the subsequent stage of this diaphragm 12, three CCDs 14A (for G signal),
14B (for B signal) and 14C (for R signal) are arranged,
RGB light separated by a beam splitter (not shown) is guided to these CCDs 14A, 14B, 14C.

An image processing circuit 18 is connected to the subsequent stage of the CCDs 14A, 14B and 14C via amplifiers 16A, 16B, 16C and 17 and the image processing circuit 1 is connected.
Reference numeral 8 performs image processing such as white balance and gamma correction. A monitor 20 is connected to the image processing circuit 18 via an encoder 19, and the CCD 1 is connected to the monitor 20.
The images captured by 4A, 14B, and 14C are displayed.
An automatic gain control (AGC) circuit 22 is connected to the amplifier 17, and the AGC circuit 22 controls the gain of the amplifier 17 based on the input signal from the amplifier 17 so that the level of the video signal is a constant value. I am trying to become.

Further, the CCD 14A, 14B, 14C
Is provided with an electronic shutter drive circuit 23. The electronic shutter drive circuit 23 drives the sweep pulse,
By applying the read pulse to the CCDs 14A, 14B, 14C, the accumulated charge in the controlled period can be read. The motion detection circuit 24 and the white balance adjustment circuit 25 are connected so that the output of the amplifier 16 is input. Further, a color temperature correction circuit 28 is provided, and these circuits are connected to the electronic shutter drive circuit 23 via a function selection switch 30. The function selection switch 30 can be switched by a selection button or the like of an operation unit or the like.

That is, the motion detecting circuit 24 selects the G (green) signal output from the CCD 14A in the first embodiment, and detects the motion state from this G signal. This motion detection is performed by measuring the G signal level (average value, etc.) between predetermined fields.
The motion detection circuit 24 controls the electronic shutter so as to shorten the accumulation time in the motion state. The white balance adjustment circuit 25 is used for, for example, RGB when a white board is photographed.
The electronic shutter is controlled so that the video signal of (1) can be made uniform (see JP-A-2-182094).

The color temperature correction circuit 28 corrects a color temperature difference due to a difference in time zone such as daytime, evening, nighttime, or a difference due to weather, and is set by a function selection button or the like of the operation unit. The electronic shutter is controlled so as to correct the nonuniformity of the level of the video signal due to the difference. Then, the function selection switch 30 selects one of the output A of the motion detection circuit 24, the output B of the white balance adjustment circuit 25, and the output D of the color temperature correction circuit 28 based on the operation of the selection button or the like of the operation unit. The control signal from the selected circuit is supplied to the electronic shutter drive circuit 23.

The amplifier 16A (16B, 16C)
(Although it may be) input the image signal output from
A switch 31 for inputting the output from the AGC circuit 22
Is connected, and the switching device 31 switches so as to select an output signal in conjunction with the switching of the function selection switch 30. That is, the switch 31 has a line E for returning the signal from the AGC circuit 22 to the amplifier 17 and a line F for the diaphragm drive circuit 13, and the signal selected according to the above-mentioned function selection is in each circuit. Is supplied to. Therefore, as described above, the gain control is performed in the AGC circuit 22, and the aperture drive circuit 13 detects the brightness level of the image signal from the input signal and adjusts the aperture 12 to obtain the optimum brightness. It will be automatically controlled.

The first embodiment is configured as described above, and the subject captured by the lens system 11 of FIG. 1 is focused on each of the CCDs 14A, 14B and 14C through the diaphragm 12, and the CCDs 14A and 14B are formed. , 14C are driven and controlled by the electronic shutter drive circuit 23, and image information of one field can be obtained by a vertical synchronization (VD) pulse shown in FIG. In the first embodiment,
G by three CCDs 14A, 14B, 14C
Image signals of (green), B (blue), and R (red) are obtained. These image signals are supplied to the amplifier 17 and the motion detection circuit 24 at the same time.

2 and 3 show the motion detecting operation. When the motion detecting circuit 24 is selected by the function selection switch 30, the motion detecting circuit 24 causes the G signal shown in FIG. Is selected, and the G signal for each predetermined field (4 fields) is extracted by the sampling pulse shown in FIG. 7C, and the levels of this G signal are compared with each other. If there is a predetermined change in the G signal, it is determined that the G signal is in the moving state, and the signal indicating the moving state or the stationary state is supplied to the electronic shutter drive circuit 23.

FIG. 3 shows the control operation of the CCD 14, and when there is no movement, the sweep pulse Pa1 and the read pulse Pb shown in FIG. 3B for each vertical synchronizing pulse of FIG. 3A. Are supplied to the CCD 14. Therefore, FIG.
As shown in (C), the charge once accumulated by the sweep pulse Pa1 is swept out, and the accumulated charges C1, C2, C3, etc. accumulated thereafter are read out as pixel signals by the read pulse Pb. On the other hand, when it is determined that the moving state is reached, the sweep pulse Pa2 and the read pulse Pb shown in FIG. 3D are output.
As shown in (E), the accumulated charges C11, C12, C13 ... Are read after being swept by the sweep pulse Pa2. Therefore, the pixel signal charges are read in a shorter time than when there is no motion, and the influence of motion can be reduced.

When this motion detecting operation function is selected,
The E and F lines are brought into the input state by the switcher 31. First, the image signal supplied from the amplifier 17 to the AGC circuit 22 is returned to the amplifier 17 and gain controlled so that the RGB signal levels become the same. . In other words, since the RGB signals have non-uniform levels due to the optical characteristics of the optical elements, the RGB signals can be adjusted here.

The output of the amplifier 16A is line F
Is supplied to the diaphragm driving circuit 13, and the diaphragm driving circuit 13 detects the brightness from the G signal and controls the overall level of the image signal to a predetermined value (ALC control). According to this, in the above movement state,
The shortage of the electric charge (light amount) due to the shortening of the accumulation time in the CCD 14 is resolved, and the deterioration of the S / N ratio due to the shortage of the electric charge can be prevented.

On the other hand, when the white balance adjusting circuit 25 is selected while photographing the white board, R signal = G signal =
A control signal for bringing the state closer to the B signal is supplied to the electronic shutter drive circuit 23. Therefore, in this electronic shutter drive circuit 23, the CCDs 14A, 14B, and
Each sweep and read pulse of 14C is formed. That is, since the sensitivity generally decreases in the order of R → G → B, the sweep pulse and the read pulse are formed so as to increase the charge accumulation time in this order, whereby a uniform RGB signal is obtained.

When a color temperature (correction coefficient) suitable for the object illumination is selected by the color temperature correction circuit 28, the charge accumulation time of RGB signals is corrected and controlled at a predetermined ratio set for each color temperature. It For example, when the weather is good in the daytime, there is no level difference between the RGB signals, so the charge accumulation times are almost the same, but in the evening, the sensitivity decreases slightly in the order of R → G → B. Then, it is controlled so as to increase the accumulation time. The lines E and F are selected by the switching circuit 31 in this case. According to this
It is possible to obtain a good image even when shooting is performed when the time zone and weather are different, or when shooting is performed under illumination at night.

In this way, the CCDs 14A, 14B,
The image signal output from the amplifier 14C and output from the amplifier 17 is subjected to predetermined processing in the image signal processing circuit 18, and the processed image signal is processed by the encoder 19
It is supplied to the monitor 20 via the monitor 20 and an image (video) of the subject is displayed on the monitor 20.

FIG. 4 shows the configuration of the second embodiment of the present invention. This second embodiment is a frame sequential device used in an electronic endoscope. In FIG. 4, a light source device 40 is provided in the electronic endoscope device, and a light guide 41 is provided up to the tip.
Is provided. In the light source device 40, a light source power source section 42, a lamp 43, a diaphragm 44, a diaphragm driving circuit 45 are provided, and further, R (red), G (green), B (blue) color disks 46 are provided. Therefore, in the field-sequential device, by rotating the color disk 46 at a predetermined speed, it is possible to sequentially send the RGB color lights into the body to be observed.

On the other hand, CC is formed on the focal plane behind the lens system 48.
A D49 is arranged, and the CCD 49 has an amplifier 50, an amplifier 51, and an AGC circuit 5 as in the first embodiment.
2, an image processing circuit 53, an encoder 54, and a monitor 55 are provided. An electronic shutter drive circuit 56 is provided in the CCD 49, and a motion detection circuit 57, a white balance adjustment circuit 58, and a video amplitude detection circuit 59 are connected so as to input the output from the amplifier 50. Further, a color temperature correction circuit 60 is provided,
These circuits are connected to the electronic shutter drive circuit 56 via the function selection switch 64, and the function selection switch 64 can be switched by a selection button or the like on the operation unit or the like. However, the color temperature correction circuit 60 is selected depending on the type of the lamp 43 in the light source device 40.

That is, FIG. 5 shows the total image pickup characteristic by the color temperature difference between the two types of light sources. For example, when the color temperature is 5000 ° K for a xenon lamp or the like, the RGB signal levels are as shown by the chain line graph I-5000. Is almost constant, but when the color temperature of the halogen lamp is 3200 ° K, the solid line graph I-3200
As described above, the RGB signal increases in the order of B → G → R. Therefore, the white balance is lost due to the change of the light source. Therefore, in the second embodiment, the difference in the light source is dealt with by controlling the electronic shutter.

Further, a changeover circuit 65 interlocking with the function selection switch 64 is connected. The changeover circuit 65 has lines E and F similar to those of the first embodiment, and is connected to the light source power source section 42 of the light source device 40. It has a line G. That is, the light source power supply unit 42 can change the power supply voltage of the lamp 43, and thereby the brightness of the lamp 43 can be changed.

According to the configuration of the second embodiment described above, RGB image information is sequentially obtained for each field in synchronization with the vertical synchronizing signal every 1/60 seconds. Here, when the motion detection operation function is selected, the motion detection circuit 57 extracts, for example, a G (green) signal between predetermined fields, thereby detecting a motion state. Then, as in the case of FIG. 3, the sweep pulse Pa2 that is delayed when there is motion is formed as compared with when there is no motion, and FIG.
As shown in, the sweep pulse Pa2 and the read pulse P
The accumulated charge will be read out in a short time between b.

At this time, in the switching circuit 65, the lines E,
F and G are selected, and like the above, the AGC circuit 5
2 performs signal processing, and the diaphragm drive circuit 45 adjusts the light amount. In the electronic shutter operation in the moving state, the S / N ratio is slightly deteriorated due to the shortening of the charge storage time. Therefore, in the second embodiment, the line G is selected without relying only on the diaphragm drive circuit 45, and the charge ) The shortage is solved by the control of the light source power supply unit 42. That is, the image signal is supplied to the light source power supply unit 42, and the power supply voltage of the lamp 43 is changed according to the level of the image signal. Then,
As the power supply voltage rises, the output of the lamp 43 increases and the accumulated charges increase, which can improve the S / N ratio. In this case, the light source voltage may be controlled according to the motion state by supplying the output of the motion detection circuit 57 to the light source power supply unit 42.

When the color temperature correction circuit 60 selects a color temperature of 5000 ° K for a xenon lamp or the like, there is no level difference between the RGB signals as shown in FIG. Accumulated time. On the other hand, if a color temperature of 3200 ° K for a halogen lamp or the like is selected, R →
Since the sensitivity decreases slightly in the order of G → B, it is controlled to increase the accumulation time accordingly. The white balance adjusting circuit 58 is the same as in the first embodiment.

Furthermore, when the video amplitude detection circuit 59 is selected (other functions are not selected) when the electronic endoscope (scope) itself is replaced, the signal amplitude is detected from the input RGB signal, This detection signal is supplied to the electronic shutter drive circuit 56. Therefore, the electronic shutter drive circuit 5
In 6, the electronic shutter is controlled so that the amplitude level of the RGB signal becomes constant. At this time, the switching circuit 6
In line 5, lines E and F are selected. In the above case, it is possible to store the control signal of the electronic shutter in the memory and set the control information according to different electronic endoscopes.

In addition to the above-mentioned image pickup device, there is a dot-sequential (simultaneous type) device using one CCD as a device using a solid-state image pickup element, but this device can be similarly applied. . In the above embodiment, the motion detection circuit 2
4 and 57 have shown the example in which the motion detection is performed based on the G (green) signal, but this may be another signal, and when the color difference signal and the luminance signal are formed, the detection may be performed based on the luminance signal. it can.

[0033]

As described above, according to the present invention,
A motion detection circuit that detects the motion state of the subject, a color temperature correction circuit that sets the color temperature, and a white balance adjustment circuit are provided so that these circuits can be selectively switched, and the charge of the solid-state image sensor is based on the selected circuit. Since the storage time is drive-controlled, the electronic shutter function can be used to obtain high-quality images when there is movement, the color temperature changes, or the white balance is adjusted. Become.

Further, since a video amplitude detection circuit is added to enable the electronic shutter operation corresponding to the exchanged electronic endoscope, a good image can be obtained by the electronic shutter operation corresponding to various functions. There is an advantage.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image pickup apparatus using a solid-state image pickup element according to a first embodiment of the present invention.

FIG. 2 is a waveform chart showing processing relating to a motion detection function in the embodiment.

FIG. 3 is a waveform diagram showing an electronic shutter operation relating to the motion detection function.

FIG. 4 is a block diagram showing a configuration of a second embodiment.

FIG. 5 is a graph showing differences in color temperature characteristics due to differences in light sources.

[Explanation of symbols]

 12, 44 ... Aperture, 13, 45 ... Input light automatic control (ALC) circuit, 14A, 14B, 14C, 49 ... CCD, 18, 53 ... Image processing circuit, 22, 52 ... Automatic gain control (AGC) circuit, 23 , 56 ... Electronic shutter drive circuit, 24, 57 ... Motion detection circuit, 25, 58 ... White balance adjustment circuit, 28, 62 ... Color temperature correction circuit, 30, 64 ... Function selection switch, 31, 65 ... Changeover switch, 42 ... light source power supply section, 59 ... video amplitude detection circuit.

Claims (3)

[Claims] 1. An image pickup apparatus using a solid-state image pickup device provided with an electronic shutter function for controlling the amount of electric charge accumulated in the solid-state image pickup device, and a motion detection circuit for detecting a motion state of a subject and a color temperature difference. A color temperature correction circuit for correction, an electronic shutter drive circuit for driving and controlling the charge accumulation time of the solid-state image sensor by control signals from these circuits, an electronic shutter function corresponding to the motion detection, and an electronic corresponding to color temperature setting. An image pickup apparatus using a solid-state image pickup device, wherein a function switching circuit for selecting a shutter function is provided, and an electronic shutter is variably controlled corresponding to a plurality of functions. 2. A white balance adjusting circuit for controlling the electronic shutter so as to maintain a white balance by inputting an image signal output from the solid-state image pickup device, and the function switching circuit performs the movement. The solid-state image pickup device according to claim 1, wherein an electronic shutter function corresponding to a white balance adjustment circuit is selectable in addition to a function corresponding to a detection circuit and a function corresponding to a color temperature correction circuit. The imaging device used. 3. A signal amplitude detection circuit for detecting the amplitude of an image signal output from the solid-state image sensor and controlling the electronic shutter so as to improve the influence of the optical characteristics of different solid-state image sensors. Further, in the function switching circuit, in addition to the function corresponding to the motion detecting circuit and the function corresponding to the color temperature correcting circuit, an electronic shutter function corresponding to the signal amplitude detecting circuit can be selected. An image pickup device using the solid-state image pickup device according to claim 2.