JPS63204977A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To prevent the fall of an S/N due to a low sensitivity picture element by substituting a high sensitivity diode output for the output of a low sensitivity diode. CONSTITUTION:Among plural number of photoelectric conversion diodes (three number of D1-D3) to constitute one picture element, the diode of the low sensitivity (e.g., D3) is stored previously in a second memory 8, prepared as a substituting means, and after the output of the respective diodes D1-D3 are successively stored in first memory 7, and the data of the three to constitute the same picture element make a set complete, at the time when the outputs of these three diodes are read out from the first memory 7, and added together, the output data of the defective diode D3 is substituted by the output data of the satisfactory diode (D1 or D2) and transmitted to an adder 4, and the addition of three data is performed. Thus, the fall of the S/N can be prevented.

Description

[Detailed Description of the Invention] [Summary] The present invention provides time delay integration.
When a low-sensitivity photoelectric conversion diode (hereinafter simply referred to as a diode) with large noise or a small signal exists in a solid-state imaging device that uses a By replacing the output with a highly sensitive diode output,
This is to prevent the S/N ratio from decreasing due to low sensitivity pixels.

[Industrial application field]

The present invention relates to a solid-state imaging device capable of correcting low sensitivity diode output in a TDI fil imaging device.

[Conventional technology]

If a low-sensitivity diode exists in a TDI image device, the S/N ratio after TDI processing will deteriorate even if the other diodes are normal. Therefore, a means or method is needed to eliminate the adverse effects of low sensitivity diodes.

As an example of a conventional TDI solid-state imaging device, a 5-pixel 3-stage T
FIG. 3 shows an imaging device with a DI configuration. In the figure, 1 is a photoelectric conversion diode, 2 is a COD shift register, and 3 is an A/D
Converter, 4 is an adder, 5 is an output terminal, 6-1 to 6-2 are one-line delay circuits, and arrows indicate the moving direction of the image on the light receiving surface.

In the example shown in the figure, each pixel is composed of three photoelectric conversion diodes. That is, one pixel is composed of diodes 1-1.1-2.1-3 at the top of the figure,
Below that, the second pixel is 2-1.2-2.2-3, and in the same way, each of the five pixels are each made up of three diodes.

In such a configuration, the three diodes 1 constituting the same pixel view the same image at different timings. That is, the diodes 1 in the second and third stages see the image after a certain period of time has elapsed from the time when the diodes 1 in the first and second stages saw the image.

Therefore, the output of each of these diodes 1 is converted into a digital signal by the A/D converter 3, and then the output of the first stage diode 1 is given a two-stage delay by delay circuits 6-1 and 6-2. , the output of the second stage diode 1 is given one stage delay by the delay circuit 6-3, and is input to the adder 4 at the same timing as the output of the third stage diode 1, and the three are added together. .

In the manner described above, the light receiving time of each pixel is effectively tripled to increase sensitivity.

[Problem that the invention seeks to solve]

Conventional TDI! In the 11 imager, as described above, <TD
I processing increases the sensitivity of each pixel, but if there is a low sensitivity diode (small signal or large noise) in one pixel, even if the other diodes are normal, S/N after TDI processing of that pixel
A problem arises in that the ratio is not improved and, on the contrary, deteriorates.

An object of the present invention is to provide a solid-state imaging device in which the S/N ratio does not deteriorate even if a low-sensitivity diode is present in one pixel.

[Means for solving problems]

As shown in the principle explanatory diagram of FIG. 1, the present invention utilizes a plurality of photoelectric conversion diodes (Di
, D2.03), a low-sensitivity diode (for example, D3) is stored in advance in the second memory 8 provided as a replacement means, and each diode DI, D2. D
The outputs of the 3 diodes are sequentially stored in the memory 7 of the 1, and after the data of the 3 diodes constituting the same pixel are collected, the outputs of the 3 diodes are read out from the 1st memory 7 and added. Based on the data indicating the defective diode stored in the memory 8 of 2, the output data of the defective diode (D3 in this case) is replaced with the output data of the good diode (DI or D2 in this case) and the adder 4, and the three data are added. Note that 100 in the same figure
indicates a signal processing section.

[For production]

The present invention eliminates the output of a defective diode by replacing the output of a defective diode with a low S/N ratio or high noise with the output of another sensitive diode and performing TDI processing. It is possible to prevent a decrease in the S/N ratio after TD■ processing.

〔Example〕

Referring to FIG. 2 below, as an embodiment of the present invention, two pixels,
An example of a three-stage TDI configuration will be described.

In the figure, 1 is a photoelectric conversion diode, 2 is a COD shift register, 3 is an A/D converter, 4 is an adder, 5 is an output terminal, 7 is a first memory that stores the diode output, and 8
9 constitutes a replacement means by a second memory storing address data for replacing the low sensitivity diode output, 9 is a replacement control signal, 10 is a timing signal to the adder 4, 10
0 is a signal processing section.

Next, the operation of this embodiment will be explained.

First, a reference black body is imaged using the solid-state imaging device having the above configuration, and each photoelectric conversion diode 1-1.1-2°1-3
．． 2-1.2-2.2-3 sensitivity was measured and the same TD
■The group, that is, the group of diodes 1-1.1-2.1-3 that constitute the same pixel in the figure, and the group of diode 2
-1.2-2.2-3 In the knob loop, in order to replace a low sensitivity diode with a high sensitivity diode so that the S/N ratio is maximized, a second memory 8 is provided as a means for replacing the address data of both. to be memorized.

After doing this, imaging is started, and the output of each diode 1 is converted into digital data via the A/D converter 3, and each is stored in the first memory 7 at a predetermined value determined for each diode 1. Store it in the address.

Next, when all the outputs of the three diodes constituting the same pixel are collected, they are read out from the first memory 7 and output to the adder 4. This reading is performed by specifying the address to be read from the first memory 7.
This address is referred to in the second memory 8, and if it is the address of a defective diode detected in advance as described above, the storage address of the output of the diode to be replaced is replaced by the replacement control. It is sent to the first memory 7 as a signal 9 . As a result, the output of the substitute diode is sent from the first memory 7 to the adder 4 in place of the output of the defective diode, and the three output data are added in accordance with the timing signal 10.

As described above, in this embodiment, TDI processing is performed by replacing the output of the defective diode with the output of the high sensitivity diode. This reduces the S/
A decrease in the N ratio can be prevented.

Incidentally, an example of the output and noise of three diodes is shown in Table 1.

Table 1 In the conventional case, the S/N ratio after TDI is (15÷10
+ 5) / (1” + 1” + 2”)””
;12.3, but according to the present invention, the output of the low sensitivity diode 1-3 is replaced with the output of the high sensitivity diode 1-1, so the S/N ratio after TDI is (( 15+1
5) + 10) / ((1+1)" + 1")
""#17.9, and the S/N ratio is improved by about 1.5 times.

〔Effect of the invention〕

As explained above, according to the present invention, even if a low-sensitivity diode exists in a TDI imaging device, it is possible to reduce the decrease in the S/N ratio after TDI processing; Also, a highly sensitive imaging device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the principle of the present invention, FIG. 2 is an explanatory diagram of an embodiment of the present invention, and FIG. 3 is an explanatory diagram of a conventional TDI solid-state imaging device. In the figure, 1 is a photoelectric conversion diode, 2 is a CCD shift register, 3 is an A/D converter, 4 is an adder, 5 is an output terminal, 7 is a first memory, and 8 is a second memory as a replacement control means.
100 represents a signal processing section. /1 Inventor theory provisional revision Figure 1 Figure 2

Claims (1)

[Claims] A pixel consisting of a plurality of photoelectric conversion diodes (1) that output electrical signals corresponding to the amount of incident light, a CCD shift register (2) that transfers the charge output from the photoelectric conversion diodes, and A signal processing unit (1
00), and replaces the output of a photoelectric conversion diode with sensitivity lower than a predetermined value with the output of another photoelectric conversion diode among a plurality of photoelectric conversion diodes constituting the same pixel as the photoelectric conversion diode. A solid-state imaging device characterized by comprising: substitution means (8) for sending the signal to the signal processing section.