JPH02122777A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To eliminate a smear signal by holding the output of a dummy signal for one horizontal scanning portion in a shift register outside a solid-state image pickup element, and producing each horizontal scanning output in the next one field and the output differential signal of the dummy signal for one horizontal scanning portion of a shift register as an image pickup output. CONSTITUTION:An image signal SI by of a CCD image sensor 1 is inputted to a sample-and-hold circuit 2, synchronized with a clock pulse CK of a driving circuit 6 of the sensor 1, sample-held, then a holding signal SH is inputted to a shift register 4 by a switching part 3 for a vertical blanking interval tauH, switched so as to be inputted to the negative terminal of a differential amplifier 5 in the other period, and the dummy transfer operation between the vertical shift register and a signal SD is executed in the vertical blanking interval. Thus, the output of the signal SD for one horizontal scanning shifted to the horizontal shift register of the sensor 1 is held in the shift register 4, and the differential signal between the output of each horizontal scanning of the next one field and the output of the signal SD held in the register 4 is made into the image pickup output. Thus, the smear signal can be eliminated.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a solid-state imaging device.

[Conventional technology]

FIG. 4 is a block diagram of an example of a conventional solid-state imaging device.

The solid-state imaging device inputs a sensor signal Sl of CCD image sensor 1 to a sample hold circuit 2, and a sensor drive circuit 6. After sampling and holding in synchronization with the clock pulse CK, the hold signal S11 is input to the negative end of the differential amplifier 5, and the difference between it and the black level reference voltage VB is used as the imaging signal S. , is output as .

[Problem to be solved by the invention]

The conventional solid-state imaging device described above has a drawback in that when capturing an image of a high-brightness object, a portion of the light incident on the light receiving element leaks into the vertical shift register, causing a so-called smear phenomenon.

FIG. 5 is a schematic diagram of a CCD image sensor for explaining the smear phenomenon of the solid-state imaging device shown in FIG. 4, and FIG. 6(a)-
(c) is a waveform schematic diagram of each part for explaining the relationship between the image of the solid-state imaging device of FIG. 4 and the horizontal scanning signal.

In an interline type CCD image sensor, the signal charges are read out from the photodiode PD all at once to the vertical shift register 8■, and then the signal charges for one horizontal scanning line are read out by the vertical shift register 8V over a time period of one field period τF. The operation of transferring the charge to the horizontal shift register 8H and then transferring it from the horizontal shift register 8H to the output circuit 9 is repeated in order, and all signal charges read out from top to bottom are sequentially output to the vertical shift register 8v.

When a high-brightness object H is imaged with an interline CCD image sensor that operates in this manner, incident light leaks into the adjacent vertical shift register 8v in the high-brightness object imaging section, producing a smear signal S5, but the vertical shift Since the register 8v repeats the transfer operation, the transfer and generation of the smear signal SS continues while the high-brightness object H is being imaged.

As a result, as shown in FIG. 6(a), a white line S due to the smear signal is generated in the vertical direction in a portion corresponding to the high-brightness subject H in the image pickup screen (2).

6 [K(b) and (C) are respectively shown in FIG. 6(a>
The hold signal SH of the solid-state imaging device for one horizontal scan corresponding to the A-A' line and the B-B' line of the image ■, respectively.
A and SOB, and in both cases, a smear signal SS is superimposed on the portion corresponding to the horizontal position of the high-brightness object H as noise, as shown by the halftone dotted line.

An object of the present invention is to provide a solid-state imaging device that outputs an imaging signal without a smear signal.

[Means to solve the problem]

The solid-state imaging device of the present invention uses a solid-state imaging device having a vertical shift register that vertically transfers imaging signal charges generated in a photoelectric conversion section and a horizontal shift register that transfers the imaging signal charges to an output circuit. In a solid-state imaging device that outputs an imaging signal, the imaging signal charge for one field is dummy transferred to the vertical shift register during a vertical period after being read out, and the imaging signal charge is transferred to the horizontal shift register by the dummy transfer operation. and a shift register that holds a dummy shift register for one water scan, and outputs a difference signal between the output signal for each horizontal scan for the next one field and the dummy signal for the one horizontal scan as the imaging signal. It is configured as.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

The solid-state imaging device includes a dual switching switch section 3 between the sample hold circuit 2 and the differential amplifier 5 shown in FIG.
This device is similar to the conventional solid-state imaging device except that a shift register 4 inputting the output end is inserted, and a sensor drive circuit 6 supplies drive pulses to the switch unit 6 and the shift register 4.

The image signal S1 of the CCD image sensor 1 is input to the sample and hold circuit 2, and after being sampled and held in synchronization with the clock pulse CK of the drive circuit 6 of the CCD image sensor, the hold signal SH is applied to the vertical blanking period τ by the switch unit 3. , a switching operation is performed so that the signal is input to the shift register 4, and to the negative end of the differential amplifier 5 during the remaining period.

Therefore, a dummy signal SD for one horizontal scan generated by vertical dummy transfer is input to the shift register 4 for each field.

Further, the switch section 3 causes the shift register 4 to form a closed loop except when waiting for input of the dummy signal SD.

Then, by applying the same clock pulse φ□ that drives the horizontal shift register of the CCD image sensor 1 from the sensor drive circuit 6 of the CCD image sensor 1 to the shift register 4, the sum terminal of the differential amplifier 5 from the shift register 4 is The configuration is such that the dummy signal SD input to the sample and hold circuit 2 and the hold signal SH output from the sample and hold circuit 2 correspond to the same vertical register.

FIG. 2 is a timing diagram of clock pulse voltages at various parts for explaining the operation of the block in FIG. 1.

The vertical shift register drive pulse 4) and the horizontal shift register drive pulse φ□ of the CCD image sensor 1 are each shown as a representative one phase out of a plurality of pulses.

The switch drive pulse φ5W of the switch unit 3 switches the movable piece of the switch unit 3 as shown by the broken line in FIG. 1 only when the level is “°H”.

3(a) to 3(f) are waveform diagrams of various parts for explaining the relationship between the image of the solid-state imaging device of FIG. 1 and the horizontal scanning signal.

As shown in FIG. 3(a), the captured image (2) displays high-luminance and low-luminance subjects H and L.

As shown in FIG. 3(b) and (C), respectively, FIG.
The hold signal SH of the sample hold circuit for one horizontal scan corresponding to the A-A' line and the B-B' line in a) is as follows:
The smear signal S5 appears as noise in the part corresponding to the high-brightness object H.

As shown in FIG.
The smear signal S5 is also used for the dummy signal SD for horizontal scanning.
Contains.

As shown in FIGS. 3(e) and 3(f), the imaging signal S.A of the solid-state imaging device for one horizontal scan corresponds to the AA line' and the BB' line in FIG. 3(a). As for SOa, an imaging signal SOA obtained by correcting the smear signal SS is obtained.

Therefore, as shown in FIG. 3(a), there is no smear phenomenon in the image I of this example.

〔Effect of the invention〕

As described above, the present invention allows a dummy transfer operation to be performed with the vertical shift register of a solid-state image sensor during the vertical retrace period after reading out one field's worth of image signal charges, and also allows the dummy transfer operation to transfer the horizontal shift register of the solid-state image sensor. The output of the dummy signal for one horizontal scan transferred to the shift register is held in a shift register outside the solid-state image sensor, and the output of each horizontal scan of the next field and the dummy signal for one horizontal scan held in the shift register are By using the output difference signal as the imaging output signal, there is an effect that smear signals can be removed.

Further, according to the present invention, it is also possible to remove vertical linear noise components other than smear signals, such as white lines caused by crystal defects in vertical shift registers.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of one embodiment of the present invention.
A timing diagram of the clock pulse voltage of each part to explain the operation of the block in the figure, Figures 3 (a) to (f) are the first
Figure 4 is a block diagram of an example of a conventional solid-state imaging device, and Figure 5 is the solid-state imaging device shown in Figure 4. A schematic diagram of a CCD image sensor to explain the smear phenomenon in FIG. It is a schematic diagram. DESCRIPTION OF SYMBOLS 1... CCD image sensor, 2... Sample hold circuit, 3... Switch part, 4... Shift register, 5... Differential amplifier, 6... Sensor drive circuit, ■
... Captured image, L... Low brightness subject, H... High brightness subject, S5... Smear signal, φH... Horizontal shift register drive pulse, φsw... Switch drive pulse, φV... Vertical shift register drive pulse.

Claims (1)

[Claims] A solid-state imaging device that outputs an imaging signal using a solid-state imaging device having a vertical shift register that vertically transfers imaging signal charges generated in a photoelectric conversion section and a horizontal shift register that transfers the imaging signal charges to an output circuit. In,
means for dummy transferring the imaging signal charges for one field to the vertical shift register during a vertical period after reading them; and a dummy shift register for one water scan transferred to the horizontal shift register by the dummy transfer operation. A solid-state imaging device, comprising: a shift register for holding, and uses a difference signal between an output signal for each horizontal scan of a subsequent one field and a dummy signal for the one horizontal scan as the imaging signal.