JPH0478224B2 - - Google Patents

Description

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

[Prior Art] FIG. 5 shows a conventional noise removal circuit called the delay difference noise removal method, which is shown in, for example, Proceedings of the National Conference of the Television Society 3-2, pp. 45-46 (1985). In the figure, 1 is a solid-state image sensor, 2 is a buffer, 3 is a delay circuit that delays a signal for a certain period of time, 4 is a differential amplifier, 5 is a switch circuit, 11 is a drive circuit that drives the solid-state image sensor 1, and 12 is a delay circuit that delays a signal for a certain period of time. A timing generator supplies drive pulses to the drive circuit 11 and gate pulses to the switch circuit 5, 9 is a low-pass filter, and 10 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. 6A 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. 5 is a means for removing this noise.

In FIG. 5, an output signal having a waveform as shown in FIG. 6A is outputted from the solid-state image sensing device 1, and is applied to the delay circuit 3 via the buffer 2, and is applied to the delay circuit 3 as shown in FIG.
A delayed signal like this is obtained. Then, the difference between the input and output of this delay circuit 3, that is, the signals shown in A and B in FIG. 6, is taken by a differential amplifier 4.

On the other hand, from the timing generator 12, a pulse signal shown in FIG.
A gate pulse having a timing as shown in FIG. 1 is outputted and applied to the switch circuit 5. The output of the differential amplifier 4 is sampled by the switch circuit 5 at the timing when the gate pulse becomes "H". At the timing when the gate pulse becomes "H", the input of the delay circuit 3 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 3 is a value representing N. It is a value. Therefore, the output of the differential amplifier 4 has a value indicating only the signal component -S when the gate pulse is "H", so the output of the differential amplifier 4 is By sampling with the switch circuit 5 and smoothing with the low-pass filter 9, an image signal from which noise components have been removed can be obtained from the signal output terminal 10.

[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 12 and the sampling switch circuit 5 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 pulse generation circuit and noise removal circuit are separated. The purpose is to obtain.

[Means for Solving the Problems] The solid-state imaging device according to the present invention uses a gate pulse that is synchronized with the edge of the reset pulse leak within each pixel period of the output of the solid-state imaging device as a gate pulse necessary for noise removal. This method uses pulses.

[Function] In the solid-state imaging device of the present invention, the gate pulse necessary for sampling for noise removal is composed of pulses synchronized with the edge portion of the reset pulse leak during each pixel period of the output of the solid-state imaging device. , the gate pulses obtained from the timing generator are no longer necessary, and there is no fear of gate pulse time lag.

[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 figure, 6 is a differential circuit that detects the rising and falling edges of the reset pulse leak included in the output of the solid-state image sensor 1, and 7 is a clip circuit that detects only the rising edge of the output of the differential circuit 6. , and the differential circuit 6 constitute a detection circuit 13 that detects the edge portion of the reset pulse leak within one cycle of each pixel of the output of the solid-state image sensor 1.
A pulse generating circuit 8 generates a pulse synchronized with the output of the clip circuit 7, that is, the rising edge of the reset pulse leak, and sends it to the switch circuit 5.

Next, the operation will be explained.

The solid-state image sensing device 1 has a portion in which a signal is output and a portion in which a signal is not output in one pixel period, and outputs a signal as shown in FIG. 2A, in which a reset pulse leak appears during the period in which a signal is not output. This signal is applied to a delay circuit 3 through a buffer 2, and a delayed signal as shown in FIG. 2B is obtained from this delay circuit 3. The input and output of this delay circuit 3, ie, the signals shown in FIG. 2A and B, are differenced by a differential amplifier 4.

On the other hand, the output of the buffer 2 is also applied to the differentiating circuit 6. The differentiating circuit 6 detects the rising and falling parts of the reset pulse leak, as shown in FIG. 2C, and sends them to the clip circuit 7. The clip circuit 7 cuts off only the rising portion, as shown in FIG. 2D, and sends it to the pulse generation circuit 8. The pulse generating circuit 8 outputs a gate pulse and applies it to the switch circuit 5 within the imaging signal period as shown in FIG. 2E in synchronization with the output of the clip circuit 7, that is, the rising edge of the reset pulse leak. The switch circuit 5 samples the output of the differential amplifier 4 at the timing when the gate pulse becomes "H" and smoothes it with the low-pass filter 9, so that an image signal from which noise components have been removed can be obtained from the signal output terminal 10. can.

In the above embodiment, the rising part of the reset pulse leak is detected by the clip circuit 7, but the falling part is detected as shown in FIG. 2F, and synchronized with this signal, as shown in FIG. 2E. As shown, the gate pulse may be generated by the pulse generation circuit 8 within the imaging signal period.

Further, in the above embodiment, the edge portion of the reset pulse leak is detected by the differentiating circuit 6, but when the DC level of the output of the solid-state image sensor 1 is stable, the buffer 2 is detected as shown in FIG. V _REF shown in Figure 4A is added to the comparator 30.
By applying this voltage to the reference voltage terminal 31 of the comparator 30, a signal for detecting a reset pulse leak portion as shown in FIG. 4B is obtained from the comparator 15. Therefore, in synchronization with the output of the comparator 15, a pulse may be generated by the pulse generating circuit 8 within the imaging signal period as shown in FIG. 2E and used as a gate pulse.

[Effects of the Invention] As described above, according to the present invention, since the gate pulse is generated from the imaging signal, even when the noise removal circuit such as a sampling switch circuit and the pulse generation circuit are used separately from each other, , gate pulses without time lag or waveform deterioration can be obtained,
This has the effect of providing a solid-state imaging device with high noise removal accuracy.

[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 this invention, and FIG. A block diagram showing the main parts of a solid-state imaging device according to an embodiment, FIG. 4 is a signal waveform diagram for explaining the operation of another embodiment of the present invention, and FIG. 5 is a block diagram showing main parts of a conventional solid-state imaging device. , FIG. 6 is a signal waveform diagram for explaining the operation of a conventional solid-state imaging device. 1... Solid-state image sensor, 3... Delay circuit, 4...
Differential amplifier, 5... switch circuit, 6... differential circuit, 7... clip circuit, 8... pulse generation circuit, 9... low pass filter, 13, 30... detection circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of 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 delay circuit that delays the output of the solid-state imaging device for a certain period, and the delay circuit. A differential amplifier that takes the difference between the input and output of the circuit, a detection circuit that detects the edge portion of the reset pulse leak in each one pixel period of the output signal of the solid-state image sensor, and a a pulse generation circuit that generates a pulse synchronized with the edge portion of the reset pulse leak based on the detection output within the imaging signal period; and a switch circuit that samples the output of the differential amplifier using the pulse obtained by the pulse generation circuit. and a low-pass filter that removes high-frequency components of the signal sampled by the switch circuit. 2. The solid-state imaging device according to claim 1, wherein the detection circuit for detecting the edge portion of the reset pulse leak is comprised of a differentiating circuit and a clip circuit connected to the differentiating circuit. 3. The solid-state imaging device according to claim 1, wherein the detection circuit for detecting the edge portion of the reset pulse leak is constituted by a comparator.