JPS6160083A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To make defects such as black and white points arising in a dotted shape on a screen inconspicuous by constituting a device of a pulse generator circuit for driving a solid-state image pickup element, a defect position memory circuit operated by the pulse generator circuit, the 1st and 2nd sample hold circuits, a horizontal correlation error detection circuit, a switch circuit and a subtractor. CONSTITUTION:The figure (a) shows a black point defect of a horizontal line signal. A position D denotes a defect position, and the diagonal line part shows the signal quantity generated in a photodiode 1 due to the light receiving quantity. Since the defect at the position D is corrected by the previous picture element signal, a sample holding pulse at the defect position D is stopped by a detect position memory circuit 12 as shown by the 1st sample holding pulse (b). Consequently, the output of the 1st sample hold circuit 10 is sample-held until a single-previous picture element (c) comes to the signal position of a picture element D as it is, as shown by the figure (c). When said signal is passed through the 2nd sample hold circuit 11 by the sample holding pulse as shown by the figure (d), the defect position D part is corrected by a signal C, that is, the previous picture signal, as shown by the figure (e).

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a solid-state imaging device for a video camera.

Conventional configurations and their problems There are various types of solid-state image sensors, but here we will take as an example an image sensor that uses a photodiode called an MO8 type image sensor and an MO5 field effect transistor, and consider the occurrence of white spot defects or black spot defects. FIG. 1 is an example showing the operating principle of an MO3O3 type element. That is, a large number of photodiodes 1, which are photosensitive elements, are arranged in a matrix, and a horizontal shift register 2 is used to sequentially read out signals accumulated in the photodiodes. Vertical shift register 3 and horizontal changeover switches 41, 42, 43.
...4n, vertical changeover switch 61.52.・・・
...6m has been installed. horizontal shift register 2
As is well known, the start point is synchronized with the horizontal synchronization signal.
Driven by clock pulses and horizontal clock pulses, the angles are 41°, 42.43. , . . . 4n are sequentially opened and closed so that all the switches are operated within one horizontal scanning time. On the other hand, the vertical shift register 3 is driven by a start pulse synchronized with the vertical synchronization signal and a clock pulse synchronized with the horizontal synchronization signal, and switches 61, 5
2. 6m is sequentially opened and closed, and all switches are operated within one vertical scanning time.

By operating these two types of switches, the charge stored in the photodiode is sequentially supplied to a load circuit composed of a resistor 6 and a power source 7, and is extracted as a voltage signal.

Here, if the photodiode 1A is destroyed for some reason and the substrate and cathode are short-circuited, the signal from the photodiode 1A always reaches the signal saturation point and becomes extremely large.

In addition, leakage occurs in the photodiode, and the photodiode 1
′″-“'on'iii””1””6113, ′,
Voltage is generated.

These are collectively referred to as white spot defects of the image sensor, and the level of the latter varies depending on the operating temperature, operating voltage, etc. of the image sensor.

Further, if the situation is opposite to the above, a black spot defect occurs, but the black spot defect is not very noticeable on the screen.

FIG. 2a shows the state of a black dot defect in the horizontal line signal, and FIG. 2b shows the state of a white dot defect in the horizontal line signal.

The shaded area in FIG. 2 indicates the amount of signal generated in the photodiode 1 depending on the amount of received light.

Figure 3 shows an example of correcting such black spot defects and white spot defects by replacing them with the signal amount of the previous picture element.0 Below, the operation of the conventional example shown in Figure 3 will be explained using Figure 4. explain. The solid-state image sensor 8 is driven by the pulse generation circuit 9,
Pulses in synchronization with this are supplied to the first sample and hold circuit 1o and the second sample and hold circuit 11. FIG. 4a shows the signal state of a horizontal line with a defect, and position D is a black spot defect. Figure 4 shows the first sample-and-hold pulse, C the output of the first sample-and-hold circuit 10, d the second sample-and-hold pulse, and e the second sample-and-hold pulse.
The output of the sample and hold circuit 11 is shown.

The first sample and hold pulse is provided by the defect position memory circuit 12.
The defect position memory circuit 12 serves to stop the first sample hold pulse (see Figure 4) at the defect position. The output of the hold circuit 1o is
As shown in FIG. 4C, since the defect position is not sampled and held, the signal of the previous picture element C is sampled and held as it is up to the signal position of the picture element. When this signal is passed through the second sample and hold circuit 11 with the second sample and hold pulse shown in d, the part at the defective position is corrected with the signal C, which is the previous pixel signal, as shown in Fig. 4e. be done. The conventional example shown in FIG. 3 is effective for black-and-white video camera devices, and defective parts other than edge parts can hardly be identified.

However, the subject of the video camera often has many edges, which makes it easy to see defects in the solid-state image sensor.

Purpose of the Invention The present invention solves the above-mentioned conventional drawbacks, and is intended to correct white spot defects or black spot defects that occur in a dotted manner on the screen due to a defect occurring in a part of a solid-state image sensor, and to correct the defect location. The purpose is to remove the horizontal correlation error signal that occurs at the correction location.

Structure of the Invention The present invention includes a solid-state image sensor, a pulse generation circuit for driving the solid-state image sensor, a defect position memory circuit operated by the pulse generation circuit, and a defect position memory circuit connected to the output of the solid-state image sensor and configured to detect the defect position by the output of the defect position memory circuit. a first sample and hold circuit that operates, a second sample and hold circuit that is connected to the output of the first sample and hold circuit and that is operated by the pulse generation circuit, and a horizontal correlation error detection circuit that is connected to the output of the second sample and hold circuit; A solid-state imaging device comprising a switch circuit connected to one output of a horizontal correlation error detection circuit and operated by a defect position storage circuit, and a subtracter that subtracts the output of the switch circuit and the other output of the horizontal correlation error detection circuit. This device is capable of making white dot defects and black dot defects that occur in dots on a screen due to a defect occurring in a portion of a solid-state image sensor less noticeable.

DESCRIPTION OF EMBODIMENTS FIG. 5 shows a block diagram of a solid-state imaging device according to a first embodiment of the present invention. In FIG. 5, the same numbers as in FIG. 3 are the same. In FIG. 6, 14 is a horizontal correlation error detection circuit, 15 is a delay circuit, 16 and 19 are subtracters, and 18 is a switch circuit. The horizontal correlation error detection circuit 14 can be composed of, for example, a delay circuit 16 and a subtracter 16.

The operation of the solid-state imaging device of this embodiment configured as described above will be described below with reference to the main waveform diagram of FIG. 6 and FIG. 7.

In the embodiment shown in FIG. 5, the same numbers as in the conventional example shown in FIG.
. . . . . . . . . . . . . . . . . . . . . . . . . FIG. 6m shows the state of a black spot defect in the horizontal line signal, where position D is the defect position, and the shaded area shows the amount of signal generated in the photodiode 1 depending on the amount of light received. To correct the defective position at position D,
In order to perform correction using the previous pixel signal, the output of the defect position storage circuit 12 is used to store the defect position/pull hold as shown in the first sample and hold circuit b as shown in Fig. 6C. As shown in the figure, the signal of the previous picture element C is sampled and held as it is up to the signal position of the picture element. This signal is transferred to the second sample-and-hold circuit 11 using the sample-and-hold node shown in FIG. 6d.
As shown in FIG. 6e, the portion at the defective position is corrected with the C signal, which is the previous pixel signal. However, if there is a change between a white object and a black object shown by diagonal lines between the defective position of photodiode 1 and the previous picture element C, as shown in the screen shown in FIG. 7A, the part shown in FIG. When enlarged and shown in FIG. 7, in example n, a white output corresponding to one picture element is generated. This operation shows the signal amounts at f, q, and h in FIG. 6, where 0 is the black level.

1 indicates the white level, and the white level for one pixel occurs more often in the n column section.0 To remove this one pixel worth of error signal, the delay circuit 16 delays it by one pixel, and one output is n
The column signal and the n-1 column signal are shown as j and k, and the other output is the i signal of the horizontal correlation error detection circuit 14.

When the signals of the n columns are passed through a subtracter with 9 before passing through the delay circuit 16 and k after passing through the delay circuit 16, an output of 1 from the horizontal correlation error detection circuit 14 is obtained.

The other output of the defective position memory circuit 12 is a switch pulse delayed by about two picture elements, shown in FIG. 6m, which activates the switch circuit 18.

There is no particular problem in the part where the horizontal correlation is taken, but in cases like Fig. 7m where the horizontal correlation cannot be taken, the horizontal correlation error signal (
1) in FIG. 6, only the defective position is switched by the switch circuit 18. By passing the output signal of this switch circuit 18 and the other output of the horizontal correlation error detection circuit 14 through the subtracter 19, the signal shown in FIG. 6 becomes the signal shown in FIG. The correlated error signal is removed, and as shown in FIG. 7C, there is no horizontal correlated error signal at the defect location.

As described above, according to this embodiment, the signal horizontal correlation error detection circuit detects the horizontal correlation error signal, and only the portion at the defective position is switched by the switch circuit, and the other output of the horizontal correlation error detection circuit and this By passing the output of the switch circuit through a subtracter, the horizontal correlation error signal at the defect position is removed, and a smooth luminance signal is obtained.

Effects of the Invention The solid-state imaging device of the present invention includes a defect correction means for correcting defects in the solid-state imaging element, a horizontal correlation error detection circuit connected to the defect correction means, and a defect position memory connected to one of the outputs of the horizontal correlation error detection circuit. By providing a switch circuit operated by the circuit and a subtracter that subtracts the output of the switch circuit and the other output of the horizontal correlation error detection circuit, the horizontal correlation error signal generated in the defective part of the solid-state image sensor is removed. It is possible to obtain a smooth screen, and its practical effect is great. , 14...
...Horizontal correlation error detection circuit, 18...Switch circuit, 19. River...Subtractor.

Name of agent: Patent attorney Toshio Nakao and one other person ξ Figure 1 Figure 2 Figure 3 Figure 1 Figure 6 ”)　　　6--　----n column Fig. 7 IY Ne6ton

Claims (1)

[Claims] a solid-state image sensor, a pulse generation circuit for driving the solid-state image sensor, a defect position storage circuit operated by the pulse generation circuit, and a defect position storage circuit connected to the output of the solid-state image sensor and operated by the output of the defect position storage circuit. a second sample and hold circuit connected to the output of the first sample and hold circuit and operated by the pulse generation circuit, and a horizontal correlation error detection circuit connected to the output of the second sample and hold circuit; a switch circuit connected to one output of the horizontal correlation error detection circuit and operated by the other output of the defect position storage circuit; and a subtraction operation for subtracting the output of the switch circuit and the other output of the horizontal correlation error detection circuit. What is claimed is: 1. A solid-state imaging device comprising a device and a device for obtaining a luminance signal output.