JPH0478223B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state imaging device, and particularly to a noise removal circuit thereof.

[Prior Art] FIG. 3 shows a conventional noise removal circuit called the delay difference noise removal method, which is shown, for example, in Proceedings of the National Conference of the Television Society of Japan 3-2, pp. 45-46 (1985). In the figure, 1 is a solid-state image sensor, 2 is a buffer, 6 is a delay circuit that delays a signal for a certain period of time, 7 is a differential amplifier, 10 is a switch circuit, 4 is a drive circuit that drives the solid-state image sensor 1, and 5 is a delay circuit that delays a signal for a certain period of time. A timing generator supplies drive pulses to the drive circuit 4 and gate pulses to the switch circuit 10, 11 is a low-pass filter, and 12 is a signal output terminal.

Next, the operation will be explained.

The mechanism of noise generated at the output stage of a solid-state image sensor is described in Japanese Patent Publication No. 11406/1983. FIG. 4A shows the output waveform of the solid-state image sensor 1. S is a signal and N is a noise. During signal readout, the output stage of the solid-state image sensing device 1 is reset every pixel period, but the noise generated by this reset circuit is held and remains at approximately the same level during one pixel period. The circuit shown in FIG. 3 is a means for removing this noise.

In FIG. 3, an output signal having a waveform as shown in FIG. 4A is outputted from the solid-state image sensing device 1, and is applied to the delay circuit 6 via the buffer 2, and is applied to the delay circuit 6 as shown in FIG. 4B.
A delayed signal like this is obtained. Then, the difference between the input and output of this delay circuit 6, that is, the signals shown at A and B in FIG. 4, is taken by a differential amplifier 7.

On the other hand, the timing generator 5 outputs a gate pulse synchronized with the drive pulse of the solid-state imaging device 1 and having a timing as shown in FIG. The output of the differential amplifier 7 is sampled by the switch circuit 10 at the timing when the gate pulse becomes "H". At the timing when the gate pulse becomes "H", the input of the delay circuit 6 is a value representing -S+N based on the feedthrough level V _R when there is no noise, and the output of the delay circuit 6 is a value representing N. It is a value. Therefore, the output of the differential amplifier 7 has a value indicating only the signal component -S when the gate pulse is "H", so the output of the differential amplifier 7 is By sampling and smoothing with the low-pass filter 11, an image signal from which noise components have been removed can be obtained from the signal output terminal 12.

[Problems to be Solved by the Invention] Since the conventional solid-state imaging device is configured as described above, it is recommended that the noise removal circuit consisting of the timing generator 5 and the sampling switch circuit 10 be used separately. In this case, there are problems such as the need for a transmission line for transmitting the gate pulse, and the need to correct the time lag and waveform deterioration of the gate pulse in the transmission line.

This invention was made to solve the above-mentioned problems, and provides a solid-state imaging device that can obtain gate pulses without time lag or waveform deterioration even when the timing generator and switch circuit are separated. The purpose is to obtain.

[Means for Solving the Problems] A solid-state imaging device according to the present invention multiplexes and transmits a gate pulse necessary for noise removal on the output of a solid-state imaging device, and extracts the gate pulse from the transmitted signal using a comparator. is reproduced and applied to a switch circuit to sample the output from the differential amplifier.

[Function] In the solid-state imaging device of the present invention, the gate pulse necessary for noise removal is multiplexed with the output of the solid-state imaging device and transmitted, so the noise removal circuit is separated from the solid-state imaging device or timing generator by a switch circuit, etc. Even in the case where the noise is removed, the time lag of the gate pulse is eliminated, and the accuracy of noise removal is improved.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of the main parts of an example of a solid-state imaging device according to the present invention, and the same parts as those of the conventional device are given the same reference numerals and the explanation thereof will be omitted.

In the same figure, 3 is a subtracter which is an example of an arithmetic unit for multiplexing the gate pulse from the timing generator 5 on the output from the buffer 2, and 8 is an example of an arithmetic unit that converts the output from the subtracter 3 to a reference voltage. The comparator is set to send out an "H" signal when the input signal is lower than the reference voltage, and to send out an "L" signal when the input signal becomes higher than the reference voltage.

Next, the operation will be explained.

The solid-state image sensor 1 has a period in which a signal is output and a period in which a signal is not output in one pixel period, as shown in FIG. 2A.
Outputs the signal shown in . This signal is applied to a subtracter 3 through a buffer 2, which subtracts the gate pulse (FIG. 2B) generated by the timing generator 5, resulting in the signal shown in FIG. 2C. The output signal of this subtracter 3 is applied to a delay circuit 6, and a delayed signal as shown in FIG. 2D is obtained. Then, the difference between the input and output of this delay circuit, that is, the signals shown in FIG. 2C and D, is taken by a differential amplifier 7.

On the other hand, the output of the subtracter 3 is applied to a comparator 8. If a comparator 8 is used that outputs "H" when the input signal is lower than the reference voltage, and "L" when it is higher than the reference voltage, a reference voltage V _S shown in FIG. 2C is applied to the reference voltage input terminal 9. Then, the comparator 8 reproduces the gate pulse shown in FIG. 2E. This gate pulse is applied to the switch circuit 10.
In addition, the output of the differential amplifier 7 is sampled at the timing when the gate pulse becomes "H". At the timing when the gate pulse becomes "H", the input of the delay circuit 6 is based on the feedthrough level V _R when there is no noise, and the timing generator 5
Let V _G be the amplitude of the gate pulse output from the delay circuit ₆ .
The output of the differential amplifier 7 is a value representing N. Therefore, the output of the differential amplifier 7 becomes a noise-free value of -S-V _G at the timing when the gate pulse is "H". Therefore, by sampling the output of the differential amplifier 7 at the timing when the gate pulse becomes "H" and smoothing it with the low-pass filter 11, the image signal from which noise components have been removed is sent to the signal output terminal 12.
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In the above embodiment, the subtracter 3 is used to multiplex the gate pulse from the timing generator 5 on the output of the solid-state image sensor 1, but an adder may be used.

[Effects of the Invention] As described above, according to the present invention, since the gate pulse is multiplexed to the imaging signal and transmitted, and the gate pulse is regenerated on the noise removal circuit side, the noise removal circuit and the solid-state imaging Even when the element and the timing generator are used separately, gate pulses without time lag or waveform deterioration can be obtained, and a solid-state imaging device with high noise removal accuracy can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main parts of a solid-state imaging device according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of the solid-state imaging device of the present invention, and FIG. 3 is a diagram of a conventional solid-state imaging device. FIG. 4 is a block diagram showing the main parts and a signal waveform diagram for explaining the operation of a conventional solid-state imaging device. 1... Solid-state image sensor, 3... Subtractor (or adder), 5... Timing generator, 6...
...Delay circuit, 7...Differential amplifier, 10...Switch circuit, 11...Low pass filter. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A solid-state imaging device having a period in which an imaging signal is output and a period in which no imaging signal is output in at least one pixel period, a timing generator that generates a pulse synchronized with a pulse that drives the solid-state imaging device, and the solid-state imaging device. an arithmetic unit for multiplexing the output of the timing generator on the output of the element; a delay circuit for delaying the output signal of the arithmetic unit for a certain period; and a differential amplifier for taking the difference between the input and output of the delay circuit. , a comparator that divides the output signal of the arithmetic unit into parts lower and higher than a certain voltage; a switch circuit that samples the output of the differential amplifier using the signal obtained from the comparator; What is claimed is: 1. A solid-state imaging device comprising a low-pass filter that removes high-frequency components of a signal.