JPH07327173A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To detect information required for luminance information control in a video signal. CONSTITUTION:A level detection circuit 15 detects luminance data L from a video signal Y2 obtained by sampling and holding a video signal Y1 outputted from a solid-state image pickup element 11 at a sample-and-hold circuit 13 and gives the data L to a digital signal processing section 17. The digital signal processing section 17 applies prescribed signal processing to video data D1 and generates control data C1 for controlling exposure of the solid-state image pickup element 11 and control data C2 for controlling a gain of the video signal based on the luminance data L.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device for converting a video signal taken out from a solid-state image pickup device into digital data and performing various kinds of data processing.

[0002]

2. Description of the Related Art In a solid-state image pickup device using a CCD solid-state image pickup device, the output of the solid-state image pickup device is subjected to processing such as gamma correction and contour correction. In particular, in the case of a color image pickup device, processing such as white balance adjustment and suppression of high-luminance pseudo signals is also performed, so that the number of processing items is large.
In such a signal processing circuit, since it is easy to set conditions for each signal processing and signal deterioration is reduced, there is a tendency to shift from analog signal processing to digital signal processing. In the case of a signal processing circuit that adopts digital signal processing, an analog value is converted to digital data at the input stage of a video signal, and after a predetermined data processing, it is converted to an analog value again at the output part to generate a video signal. Is composed of.

FIG. 2 is a block diagram showing the configuration of a solid-state image pickup device adopting digital signal processing. The CCD solid-state imaging device 1 has a plurality of light receiving pixels arranged in rows and columns, and accumulates information charges generated in response to light emitted from a subject in each light receiving pixel. The CCD drive circuit 2 supplies a multi-phase transfer clock φ _n to the solid-state image sensor 1, transfers and outputs the charges accumulated in each light receiving pixel, and obtains a video signal Y1. The sample hold circuit 3 samples and holds the video signal Y1 output from the solid-state image sensor 1 in synchronization with the driving timing of the solid-state image sensor 1, and outputs a video signal Y2.
The automatic gain control circuit 4 gives a predetermined gain to the video signal Y2 and outputs a video signal Y3 that maintains the average level for each screen substantially constant. The A / D converter 5 converts the video signal Y3 into digital data for each pixel and outputs the video data D1.
Is supplied to the digital signal processing unit 6. The digital signal processing unit 6 responds to a control instruction given from the outside,
The gamma correction, the reference level clamp, the white balance adjustment and the suppression of the high-luminance pseudo signal are performed on the video data D1 in the case of color imaging, and the video data D2 is output. Then, the D / A converter 7 converts the video data D2 into an analog value and outputs it as a video signal Y4.

In the case of such a solid-state image pickup device, exposure control is performed by setting the operation timing of the drive circuit 2 so that the solid-state image pickup device 1 is always maintained in an appropriate exposed state. This exposure control is stored in all the light receiving pixels in the middle of the charge storage period of the solid-state image sensor 1, as disclosed in, for example, Japanese Patent Laid-Open Nos. 3-22768 and 3-48586. After discharging the information charges, the newly accumulated information charges are transferred and output to obtain a video signal. That is, when the brightness of the subject is high and the solid-state image sensor 1 is irradiated with a large amount of light, the charge accumulation period from the discharge timing of the information charges to the read timing is set short by delaying the discharge timing of the information charges. Conversely, when the brightness of the subject is low, the discharge timing of the information charges is advanced and the charge accumulation period is set to be long. Therefore, even if the brightness of the subject changes, the exposure of the solid-state imaging device 1 is always maintained in an appropriate state.

[0005]

When the exposure control of the solid-state image pickup device 1 is made to follow the change in the brightness of the object, the average level of the video signal is detected, and the drive circuit 2 is responsive to the increase or decrease of the average level. A feedback loop is provided to set the drive timing. When video data is processed by digital signal processing as in the solid-state imaging device shown in FIG. 2, the operation timing of the drive circuit is determined based on the luminance data extracted by the digital signal processing unit 6. Composed. However, the automatic gain control circuit 4 is provided between the solid-state image sensor 1 and the digital signal processing unit 6, and the video data D provided to the digital signal processing unit 6 is provided.
Since 1 does not uniquely correspond to the exposure state of the solid-state image sensor 11, the brightness information extracted from the digital signal processing unit 6 cannot be used as it is as the exposure control information.
Therefore, the digital signal processing unit 6 calculates the gain of the automatic gain control circuit 4 and subtracts the gain amount from the luminance information to obtain accurate exposure control information. For this reason, the gain information of the automatic gain control circuit 4 needs to be supplied to the digital signal processing unit 6, and the calculation for calculating the accurate exposure control information is required, resulting in a large load on the digital signal processing unit 6. Become.

It is therefore an object of the present invention to directly obtain the exposure control information and reduce the load of the digital signal processing process.

[0007]

The present invention has been made to solve the above-mentioned problems, and is characterized in that a plurality of light-receiving pixels arranged in a matrix have information charges corresponding to a subject image. A solid-state image sensor for accumulating data, driving means for transferring and outputting the information charges of the light receiving pixels at a constant cycle to obtain a first video signal corresponding to the amount of information charges, and detecting the level of the first video signal. Then, the level detecting means for generating the luminance data corresponding to the signal level, the amplifying means for giving an arbitrary gain to the first video signal to control the average level in screen units, and the first video signal in sequence. An analog-to-digital converter that generates digital image data to generate first video data, and various arithmetic processing is performed on the first video data according to the luminance data to generate second video data. Desi to do In that it comprises analog converter, a - and Le signal processor, the digital to generate a second video signal into the second video data into an analog value.

[0008]

According to the present invention, the signal level is detected from the video signal output from the solid-state image sensor and is supplied to the digital signal processing section, so that the brightness data corresponding to the exposure state of the solid-state image sensor is obtained. be able to. Therefore, this brightness information can be used as it is as the exposure control information, and the load of the arithmetic processing in the digital signal processing unit can be reduced.

[0009]

1 is a block diagram showing the configuration of a solid-state image pickup device according to the present invention. The CCD solid-state imaging device 11 has a plurality of light-receiving pixels arranged in a matrix to receive light from a subject and generates information charges. The CCD driving circuit 12 supplies the solid-state imaging device 11 with a multiphase transfer clock φ _n. The video signal Y1 is output by pulse driving. The solid-state image sensor 11 and the drive circuit 12 have the same configuration as that of FIG.

The sample and hold circuit 13 is configured to perform correlated double sampling which takes in the difference between the reference level of the video signal Y1 and the video information level in synchronization with the drive timing of the solid-state image pickup device 1, and only the video information. Output a video signal Y2. The voltage control type amplifier 14 gives the video signal Y2 a gain that is variably set according to the applied control voltage V _C , and outputs the video signal Y3 amplified to a predetermined level. Each of the sample hold circuit 13 and the voltage control type amplifier 14 can have a MOS transistor configuration, and is integrated on a single semiconductor substrate together with a digital signal processing section 16 and a timing control circuit 19 described later. It's easy.

The level detection circuit 15 takes in the video signal Y2 output from the sample hold circuit 13 and generates luminance data L corresponding to the signal level. The level detection circuit 13 can be configured by a known A / D converter. The A / D converter 16 converts the video signal Y3 into digital data for each pixel and outputs the video data D1.
Is supplied to the digital signal processing unit 17. The digital signal processing unit 17 performs gamma correction on the video data D1, clamps the reference level, adjusts white balance in the case of color imaging, and suppresses high-luminance pseudo signals, and outputs video data D2. Then, the D / A converter 18 converts the video data D2 output from the digital signal processing unit 17 into an analog value and outputs it as a video signal Y4.

By the way, in the digital signal processor 17,
In addition to performing signal processing on the video data D1, control data C1 for exposure control of the solid-state imaging device 11 and control data C2 for gain control of the voltage control type amplifier 14 are generated based on the luminance data L. Is generated. In the process of generating these control data C1 and C2, first, the luminance data L
Are added in one screen unit (one vertical scanning period unit), and the added value is compared with a reference value indicating a proper range of the exposure state and a reference value indicating a proper range of the signal level of the video signal Y3. It As a result, when the added value exceeds each reference value, the control data C1 is generated so as to reduce the exposure of the solid-state image sensor 11, and the control data C2 is generated so that the gain for the video signal Y2 is reduced. . On the contrary, when the added value becomes smaller than the respective reference value, the control data C1 and C2 are generated so as to open the exposure of the solid-state image sensor 11 and increase the gain for the video signal Y2.

The timing control circuit 19 generates a timing signal T for determining the operation timing of the drive circuit 12 in response to the control data C1 given from the digital signal processing section 17 every vertical scanning period. That is, the timing control circuit 19 fixes the read timing of the information charges of the solid-state image sensor 11 and sets the discharge timing of the control data C1.
The charge accumulation period from the discharge timing to the read timing is expanded / contracted by variably setting in accordance with. For example, as the subject brightness increases, the brightness data L
Becomes larger, the control signal C1 is generated in the digital signal processing unit 17 so as to delay the charge discharge timing of the drive circuit 12, and the charge accumulation period of the solid-state imaging device 11 is shortened in response to the control data C1. On the contrary, if the luminance data L becomes smaller due to the reduction of the subject luminance, the digital signal processing unit 17 generates the control data C1 so as to accelerate the discharge timing of the charges, and the charge accumulation period of the solid-state image sensor 11 is extended. Therefore, the exposure of the solid-state imaging device 11 is maintained in an appropriate state according to the subject brightness.

The D / A converter 20 converts the control data C2 given from the digital signal processing section 17 into an analog value for each vertical scanning period, and supplies the analog value to the voltage control type amplifier 14 as a control voltage V _C. To do. The digital signal processing unit 17 generates the control data C2 so as to reduce the gain of the voltage control type amplifier 14 in response to the increase in the brightness data L, and when the brightness data L is large, that is, the video signal Y3. The higher the level is, the lower the control voltage V _C supplied to the voltage controlled amplifier 14 is configured. Therefore, the average level of the video signal Y3 output from the voltage control type amplifier 14 falls within a predetermined range.

As described above, if the brightness data L is obtained from the video signal Y2 before being input to the voltage control type amplifier 14 and supplied to the digital signal processing section 17, the control data C1 and the gain control for the exposure control are obtained. It is possible to directly obtain the control data C2 for. Further, the brightness data L supplied to the digital signal processing unit 17 can also be used as control information other than the above-described exposure control and gain control.

[0016]

According to the present invention, since the brightness information is directly obtained from the video signal before gain control, when the exposure control information of the solid-state image pickup device or the gain control information of the video signal is obtained, The arithmetic processing in the signal processing unit is simplified. Therefore, the load of signal processing in the digital signal processing unit is reduced, and the information necessary for controlling the brightness of the video signal can be detected more accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a solid-state imaging device of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional solid-state imaging device.

[Explanation of symbols]

 1, 11 CCD solid-state image sensor 2, 12 Drive circuit 3, 13 Sample and hold circuit 4 Automatic gain control circuit 5, 16 A / D converter 6, 17 Digital signal processing unit 7, 18, 20 D / A converter 14 Voltage Control type amplifier 15 Level detection circuit 19 Timing control circuit

Claims (2)

[Claims] 1. A solid-state imaging device for accumulating information charges corresponding to a subject image in a plurality of light-receiving pixels arranged in a matrix, and information charges of the light-receiving pixels are transferred and output at a constant cycle to correspond to the amount of information charges. A driving means for obtaining a first video signal; a level detecting means for detecting the level of the first video signal and generating luminance data corresponding to the signal level;
Means for giving an arbitrary gain to the video signal of (1) to control the average level in screen units, and an analog-digital converter for sequentially converting the first video signal into digital data to generate the first video data. A digital signal processing unit for performing various arithmetic operations on the first video data based on the luminance data to generate second video data; and converting the second video data into an analog value. And a digital-analog converter that generates a second video signal. 2. A solid-state imaging device for accumulating information charges corresponding to a subject image in a plurality of light-receiving pixels arranged in a matrix, and information charges accumulated in each light-receiving pixel of the solid-state imaging device are discharged at a first timing. After that, the first transfer signal is output at the second timing and the first charge corresponding to the information charge accumulated in the charge accumulation period from the first timing to the second timing.
Driving means for obtaining the video signal, level detection means for detecting the level of the first video signal, and generating luminance data corresponding to the signal level, and a screen for applying an arbitrary gain to the first video signal. Amplifying means for controlling an average level of the unit, an analog-digital converter for converting the first video signal into digital data in sequence to generate first video data, and the first based on the luminance data. The second control data for performing the various arithmetic processing on the video data to generate the second video data, the first control data for determining the drive timing of the driving means, and the second control data for determining the gain of the amplifier circuit. And a digital-analog converter that converts the second video data into an analog value to generate a second video signal. Body imaging apparatus.