JPH0628414B2 - Solid-state imaging device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a solid-state imaging device using a solid-state imaging device such as a CCD, and more particularly to image defect correction of the solid-state imaging device.

[Technical background of the invention and its problems]

As is well known, it is difficult to uniformly form a semiconductor crystal over a predetermined area, and a crystal defect is likely to occur locally.
Electric charges are likely to be abnormally generated in the crystal defect portion.

When such a crystal defect exists in a solid-state image sensor such as a CCD, the component appears as a white dot-like image defect on the screen of the receiver. As a method of correcting such an image defect, as disclosed in Japanese Patent Publication No. 58-25786, there is a method of suppressing the signal level by applying a correction pulse of opposite polarity to the image defect portion. This correction pulse needs to have an amplitude commensurate with the amplitude of the image defect. However, the amplitude of the image defect generally increases as the temperature of the solid-state image pickup element rises, as shown in FIG. Therefore, it is necessary to change the amplitude of the correction pulse according to the temperature change. Therefore, a circuit that amplitude-modulates the correction pulse is necessary to correct the image defect. However, since the pulse width of the pulse handled by the amplitude modulation circuit is very narrow, when the amplitude of the correction pulse becomes small, the current flowing through the circuit also becomes small, and the pulse characteristic deteriorates remarkably.

FIG. 4 shows the relationship between the current flowing through the transistor in the amplitude modulation circuit and the correction pulse output amplitude. As is clear from the figure, the correction pulse output disappears at a certain current or less. For this reason, when the image defect amplitude is sufficiently large, there is no problem, but when the temperature of the solid-state image sensor decreases and the image defect amplitude decreases, the problem that the image defect correction cannot be performed correctly occurs.

[Object of the Invention]

The present invention has been made based on the above circumstances, and an object thereof is to provide a solid-state imaging device capable of correcting image defects in a wide range of temperatures.

[Outline of Invention]

According to the present invention, the amplitude of the image defect correction pulse is composed of a component that changes in response to a temperature change of the solid-state image sensor and a constant component that is irrelevant to the temperature change. This is to prevent the pulse amplitude from dropping below a certain value.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a solid-state image sensor, for example, a CCD image sensor 11 is driven by a CCD drive circuit 12,
The output signal of the image sensor 11 is the video signal processing circuit 1
3 into a video signal.

Further, the image defect synchronizing circuit 14 generates a pulse signal which is synchronized with the image defect signal output from the CCD image sensor 11, and the pulse signal is supplied to the CCD driving circuit 12 as well as the modulating circuit 15 and the amplifier 16. Is supplied to. A signal corresponding to the temperature of the CCD image sensor 11 detected by the temperature sensor 17 is supplied to the modulation circuit 15 through an amplifier 18, and the amplitude of the pulse signal supplied from the image defect synchronization circuit 14 is supplied by this signal. Is modulated. Therefore, the modulation circuit 15 outputs a pulse signal having an amplitude corresponding to the temperature of the CCD image sensor 11. The amplifier 16 amplifies the pulse signal supplied from the image defect synchronizing circuit 14 to a constant amplitude regardless of temperature. The output pulse signal of the amplifier 16 is the pulse signal output from the modulating circuit 15. At the same time, it is supplied to the adder circuit 19 and added. The pulse signals added by the adder circuit 19 are supplied to the pulse width modulation circuit 20, which is shaped into a pulse width suitable for image defect correction and a corrected pulse signal is generated. This correction pulse signal is used for the CCD image sensor 1
No. 1 is applied to the output gate electrode (not shown) to suppress image defects.

Here, by appropriately adjusting the amplitude of the pulse signal output from the amplifier 16 as a constant component that does not depend on the temperature, the correction pulse signal is always guaranteed to be output regardless of the temperature.

FIG. 2 shows the temperature characteristic of the correction pulse in this embodiment. As is clear from the figure, the correction pulse signal does not disappear even when the amplitude is small. It is also possible that the correction pulse signal becomes larger than the image defect amplitude, but in that case, the defect becomes a small black dot on the screen and is less noticeable than the case of a white dot.

According to the above-described embodiment, the amplitude of the pulse signal synchronized with the image defect signal is changed according to the temperature of the CCD image sensor 11, and the pulse signal is amplified to a constant amplitude regardless of the temperature. Are added to generate a correction pulse signal. Therefore, when the temperature is high to some extent, the amplitude-corrected correction pulse signal can be used to perform defect correction according to temperature changes, and when the temperature is low, the defect correction can be performed using a correction pulse having a constant amplitude. It is possible to surely suppress the image defect with respect to a wide range of change.

The present invention is not limited to the above embodiment,
It is possible to apply all of the correction methods for suppressing the image defect by the correction pulse corresponding to the amplitude.

Further, the solid-state image pickup device is not limited to the CCD image sensor, and the present invention can be applied to, for example, a MOS type solid-state image pickup device.

Further, when the pulse width of the pulse signal output from the image defect synchronizing circuit 14 coincides with the image defect signal and is generated, the pulse width modulation circuit 20 is not necessary.

Of course, various modifications can be made without departing from the spirit of the invention.

〔The invention's effect〕

As described above in detail, according to the present invention, it is possible to provide a solid-state imaging device capable of correcting image defects in a wide range of temperatures.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a solid-state imaging device according to the present invention, FIG. 2 is a characteristic diagram showing an example of amplitude and temperature characteristic of a correction pulse used for image defect correction of the present invention, and FIG. FIG. 4 is a diagram for explaining the amplitude and temperature characteristics of the image defect in the solid-state image sensor, and FIG. 4 is a diagram for explaining the characteristic of the correction pulse used for the conventional image defect correction of the solid-state image sensor. 11 ... CCD image sensor, 14 ... Image defect synchronization circuit, 15 ... Modulation circuit, 16 ... Amplifier, 19 ... Addition circuit, 20 ... Pulse width modulation circuit.

Claims (1)

[Claims] 1. A solid-state image pickup device comprising a solid-state image pickup device in which a plurality of photosensitive elements are arranged, and means for generating a video signal from an output signal of the solid-state image pickup device, in synchronization with an image defect of the solid-state image pickup device. A means for generating a pulse signal, a means for detecting the temperature of the solid-state imaging device, a means for changing the amplitude of the pulse signal according to the detected temperature, the changed pulse signal and the generated pulse signal. A solid-state image pickup device comprising: means for adding a pulse signal irrelevant to temperature change to generate an image defect correction pulse signal for the solid-state image pickup element.