JPH089259A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To increase the dynamic range of a solid stage image pickup device toy changing nonlinearly the overflow drain voltage within a single vertical scanning period and therefore preventing the output of a CCD solid-state image pickup element from being set at its saturation level. CONSTITUTION:In a camera system which applies the photoelectric conversion to the incident light and outputs the video signals, a CCD solid state image pickup element 7 is provided to apply the photoelectric conversion to the incident light into the signal charge together with a timing signal generator 1 which drives the element 7, a detecting part 2 which detects a read pulse that is generated by the generator 1 to the element 7, and an overflow drain voltage generating part 6 which generates a voltage waveform that varies nonlinearly within a single vertical scanning period of the read pulse detected by the part 2 and applies this waveform to the element 7.

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,
In particular, it relates to the dynamic range of a solid-state image sensor using a CCD (charge coupled device).

[0002]

2. Description of the Related Art FIG. 4 shows a CC of an interline transfer system.
FIG. 2 is a block diagram of a D solid-state image pickup device, and as shown in the figure, a photosensor (light-receiving unit) 21 that is two-dimensionally arranged in pixel units and photoelectrically converts incident light into signal charges and stores the signal charges, and these photosensors 21. An image pickup area 24 is configured by a vertical register (vertical charge transfer section) 23 which is arranged for each vertical column of and which vertically transfers the signal charges read out through the read gate 22. The vertical register 23 transfers the signal charges read from the photosensor 21 to the horizontal register (horizontal charge transfer unit) 25 in a cycle of one horizontal scanning period, and the horizontal register 25 performs one scan transferred from the vertical register 23. The signal charge of the line segment is transferred horizontally. At the output end of the horizontal register 25, a charge detection unit 26 including, for example, a floating diffusion amplifier is arranged, and the charge detection unit 26 detects the signal charge transferred by the horizontal register 25 and converts it into a signal voltage. Then, the pixel signals corresponding to the signal charges accumulated in each photo sensor 21 are output in time series.

In the above CCD solid-state image pickup device, its dynamic range is determined by the amount of charge that can be accumulated in the photosensors 21, but the maximum amount of charge that can be accumulated in each photosensor 21 varies and is above the limit. When the amount of light is incident, element unevenness occurs on the screen. For this reason,
In order to equalize the amount of charge handled by each photo sensor 21, an overflow drain (OFD) voltage that discharges excess charge is applied to the photo sensor 21, and the charge accumulated in the photo sensor 21 is saturated by changing the OFD voltage value. Level Q is set to an appropriate value. Therefore, as shown in FIG. 5, when the light amounts a and b exceeding the saturation level (CCD saturation level) Q of the photosensor 21 are incident, the accumulated charge amount is saturated and the light amounts c and d that do not exceed the saturation level Q. When is incident, the charge amount corresponding to that is read out.

[0004]

Therefore, when the photosensor 21 receives a predetermined amount of light or more, the signal charges are saturated, so that the signal charges of the light amounts a and b are read out at the same level as a1 and b1. Therefore, there is a problem that the dynamic range is narrowed. The present invention has been made in view of the above problems, and changes the overflow drain voltage nonlinearly within one vertical scanning period so that the output of the CCD solid-state imaging device is not saturated and the dynamic range is increased. The purpose is to spread.

[0005]

A solid-state image pickup device according to the first invention of the present application is a camera system for photoelectrically converting incident light and outputting it as a video signal, and a CCD solid-state image pickup device for photoelectrically converting incident light into signal charges. A timing signal generator for driving the CCD solid-state image pickup device, a detector for detecting a read pulse generated by the timing signal generator for the CCD solid-state image pickup device, and one vertical pulse of the read pulse detected by the detector. An overflow drain voltage generator for generating a voltage waveform that changes non-linearly during the scanning period and applying the voltage waveform to the CCD solid-state imaging device is provided. In the solid-state imaging device according to the second invention of the present application, the overflow drain voltage generating unit generates a voltage corresponding to one vertical scanning period, and a voltage waveform from the voltage generating unit is nonlinearly shaped and output. And a signal output from the detection unit is input to the voltage generation unit, and a non-linear overflow drain voltage is generated based on the voltage generated by the voltage generation unit. In the solid-state imaging device of the third invention of the present application, the overflow drain voltage generating unit converts a non-linear voltage data corresponding to one vertical scanning period in advance, and a voltage data read from the memory into an analog signal. And a signal output from the detection unit is input to the memory to generate a nonlinear overflow drain voltage based on the read nonlinear voltage data.

[0006]

According to the present invention, the overflow drain voltage generating section generates an overflow drain voltage which changes non-linearly within one vertical scanning period based on the read pulse from the timing signal generator detected by the detecting section. The CCD solid-state image pickup device is applied with the signal charges. Therefore, it is possible to output a signal charge corresponding to incident light from the CCD solid-state image pickup device, thereby expanding the dynamic range.

[0007]

FIG. 1 is a block diagram showing an embodiment of the solid-state image pickup device of the present invention. The timing signal generator 1 generates a signal for driving the CCD solid-state imaging device 7 of the camera, and the detection unit 2 detects the read pulse generated by the timing signal generator 1 and inputs it to the OFD voltage generation unit 6. To do. The OFD voltage generator 6 generates an overflow drain voltage that changes non-linearly in one vertical scanning period detected by the detector 2 and applies it to the CCD solid-state image sensor 7, and the CCD solid-state image sensor 7 converts the incident light 8 into a signal charge. Photoelectric conversion and output. The OFD voltage generator 6 generates a voltage corresponding to one vertical scanning period, for example, a voltage generator 3 for generating a triangular wave or square wave voltage, and a voltage waveform from the voltage generator 3.
For example, a voltage waveform shaping unit 4 that non-linearly shapes and outputs a time constant circuit using a resistor and a capacitor, and a voltage output unit 5 that adjusts and outputs the voltage level shaped by the voltage waveform shaping unit 4 Then, a voltage is generated in the voltage generator 3 by the input from the detector 2, and a non-linear overflow drain voltage is generated based on this voltage.

FIG. 2 is a block diagram showing another embodiment of the OFD voltage generator. The OFD voltage generator 6 has a memory 9 in which nonlinear voltage data corresponding to one vertical scanning period is stored in advance, a D / A converter 10 for converting the voltage data read from the memory 9 into an analog signal, / A
A voltage output unit 11 that adjusts and outputs the voltage level from the converter 10 and generates a non-linear overflow drain voltage based on the non-linear voltage data read from the memory 9 by the input from the detection unit 2. You may do it.

FIG. 3 is an explanatory diagram of accumulated charges in the solid-state image pickup device according to the present invention. FIG. 3A shows a vertical synchronizing signal for driving the CCD solid-state image pickup device 7. Based on the vertical synchronizing signal input from the timing signal generating section 1, the detecting section 2 reads out as shown in FIG. 3B. Generate a pulse,
The signal charge accumulated in the photosensor 21 shown in FIG. 4 is applied to the CCD solid-state image sensor 7 as a timing signal for reading, and the OFD voltage generator 6 generates a non-linear overflow drain voltage as shown in FIG. CCD
The saturation level of the photo sensor 21 is determined by applying it to the solid-state image sensor 7. Therefore, as shown in FIG. 3D, the CCD solid-state imaging device 7 becomes saturated with the nonlinear OFD characteristic, and the accumulated charge amount of the photosensor 21 is, for example, the incident light 8
Is the order of intensity, a, b, c and d are incident lights 8 which are photoelectrically converted by the CCD solid-state image sensor 7 and are accumulated in the photosensor as accumulated charges a2, b2, c2 and d2.

Each of the accumulated charges a2, b2, c2 and d2 is saturated in the middle of the vertical scanning period due to the nonlinear OFD characteristic, but at the end of the vertical scanning period, each accumulated charge a2, b2, and d2. While c2 and d2 change substantially linearly, the OFD characteristic is non-linear, and therefore, at the read timing position at the end of the vertical scanning period, the accumulated charge a2 according to the intensity of each incident light 8 is obtained. , B
Since 2, c2 and d2 are obtained at different levels, it is possible to widen the dynamic range. The transfer of the accumulated charges from the CCD solid-state image sensor 7 is the same as in the conventional example shown in FIG.

[0011]

As described above, according to the present invention,
Since the overflow drain voltage applied to the CCD solid-state image pickup device is changed non-linearly within one vertical scanning period, at the read timing position at the end of the vertical scanning period, it depends on the intensity of each incident light. Since the accumulated charge can be output, it is possible to provide a CCD solid-state imaging device in which the dynamic range of the CCD solid-state imaging device is widened.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing another embodiment of the OFD voltage generator of FIG.

FIG. 3 is an explanatory diagram of accumulated charges of the solid-state imaging device according to the present invention.

FIG. 4 is a block diagram of a CCD solid-state image sensor according to the present invention.

FIG. 5 is a diagram of accumulated charge amount of a conventional photo sensor.

[Explanation of symbols]

 1 Timing signal generator 2 Detection part 3 Voltage generation part 4 Voltage waveform shaping part 5 Voltage output part 6 OFD voltage generation part 7 CCD solid-state image sensor 8 Incident light 9 Memory 10 D / A converter 11 Voltage output part

Claims (3)

[Claims] 1. In a camera system for photoelectrically converting incident light and outputting it as a video signal, a CCD solid-state image sensor for photoelectrically converting incident light into a signal charge, and a timing signal generator for driving the CCD solid-state image sensor. A detector for detecting a read pulse for the CCD solid-state image sensor generated by the timing signal generator, and a voltage waveform that nonlinearly changes within one vertical scanning period of the read pulse detected by the detector, A solid-state image pickup device comprising: an overflow drain voltage generator applied to the CCD solid-state image pickup device. 2. The overflow drain voltage generator includes a voltage generator that generates a voltage corresponding to one vertical scanning period, and a voltage output unit that nonlinearly shapes and outputs a voltage waveform from the voltage generator. 2. The solid-state imaging device according to claim 1, wherein a signal from the detection unit is input to the voltage generation unit, and a non-linear overflow drain voltage is generated based on the voltage generated by the voltage generation unit. 3. The overflow drain voltage generating section includes a memory in which nonlinear voltage data corresponding to one vertical scanning period is stored in advance, and a voltage output section for converting the voltage data read from the memory into an analog signal. 2. The solid-state imaging device according to claim 1, wherein the signal from the detection unit is input to the memory, and a nonlinear overflow drain voltage is generated based on the read nonlinear voltage data.