JP2636211B2 - Noise elimination circuit for solid-state imaging device for color video - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial Field of Use B Summary of the Invention C Prior Art D Problems to be Solved by the Invention E Means for Solving Problems (FIG. 1) F Function G Example G1 Example of Data Stored in Memory G2 Configuration of Noise Removal Circuit (FIG. 1) H Effects of the Invention A Industrial Field of the Invention The present invention provides, for example, three solid-state image pickup devices made of semiconductor elements such as CCDs for each of red, green, and blue colors. The present invention relates to a noise elimination circuit for a color video solid-state imaging device which removes noise due to crystal defects of semiconductor elements constituting a solid-state imaging body of the used solid-state imaging device.

B. Summary of the Invention The present invention provides a color image pickup device for removing noise caused by crystal defects in a solid-state image pickup device using three solid-state image pickup members, for example, a semiconductor device such as a CCD for each of red, green and blue colors. In a noise elimination circuit of a video solid-state imaging device, first data indicating a crystal defect position of a semiconductor element of each solid-state imaging body is stored in a memory for storing a crystal defect position of the semiconductor element;
Second data indicating which one of the three solid-state imaging elements has a crystal defect in the semiconductor element is stored, and which of the three image sensors outputs an image signal output to be sampled and held by the first data. By determining whether an output is from a solid-state image pickup device and removing noise, a single memory can remove noise due to crystal defects in semiconductor elements of all solid-state image pickup devices.

C. Related Art In recent years, a solid-state imaging device using a solid-state imaging body made of a semiconductor element such as a CCD has been put to practical use.

For example, when a CCD is used as the solid-state image pickup body, a SiO ₂ layer is formed on one surface of a silicon semiconductor substrate, and electrodes are formed on the SiO ₂ layer at regular intervals. An image is optically projected from the opposite side to accumulate electric charge in a portion under each electrode of the semiconductor element, and the accumulated signal is sequentially transferred and read out by a clock pulse applied to the electrode. .

In a solid-state imaging device including a solid-state imaging element using such a semiconductor element, it is difficult to uniformly form a crystal of the semiconductor element over a certain area, and a local crystal defect occurs,
In a portion having the crystal defect, electric charge is easily generated due to a thermal cause, and therefore, the dark current tends to be abnormally large in this portion as compared with other portions. For this reason, when an image is projected and a signal is read out as described above, noise is generated where the dark current is abnormally large. Therefore, as shown in FIG. 2, for example, a noise N larger than the white level is mixed in the video signal S _O , and when the noise N is projected on a reproduction screen, the noise N becomes conspicuous.

One method for removing the noise N is to use a memory. That is, it can be achieved by storing a crystal defect portion of a semiconductor substrate in a memory in advance and controlling an output of an image signal obtained from a solid-state image sensor using an output signal of the memory.

The above-mentioned memory stores contents corresponding to the presence or absence of a crystal defect, and this memory content is usually the presence or absence of a crystal defect for each picture element.

Therefore, it has N _H picture elements in the horizontal direction and
It shall apply to the CCD so as to have a number of picture elements of the N _V requires a memory capacity of N _H · N _V (bits). 300 to 500 pieces is N _H in order to obtain a normal TV image and the same image, N _V 20
Approximately 0 to 300 pieces are required, so storing a crystal defect by the above method results in a large-capacity memory. Therefore, in such a configuration, the memory becomes expensive, and this kind of solid-state imaging device is provided at low cost. It has disadvantages that cannot be obtained.

One method of reducing the memory capacity is not to sequentially store the presence or absence of a crystal defect in the number of picture elements, for example, but to encode and store the position where the crystal defect exists. In order to encode the position where the crystal defect exists, the respective positions of the X and Y coordinates on the plane coordinates of the semiconductor element may be encoded. Here, if the number N _H of picture elements in the horizontal scanning direction is about 500, the positions of the picture elements in the horizontal scanning direction can all be represented by a capacity of about 9 bits. It may be about 8 bits as well as number of picture elements N _V is the 300 or so that exist likewise vertically.
In the case of employing the interlaced scanning method, it is necessary to determine whether a crystal defect exists in a picture element area of an odd field or an area of an even field, so that one bit is required for field determination.

As described above, if the position including the crystal defect (XY coordinates) and the field discrimination are included, all such information can be expressed by a total of about 18 bits. Also, if the maximum number of crystal defects that can be tolerated as a product for one CCD is assumed to be 20, the memory capacity is only about 400 bits, and it can be seen that a small-capacity memory is sufficient for practical use. .

A method of encoding and storing this crystal defect position is disclosed in Japanese Patent Application No. 52-9108, an example of which will be described below. Now, consider a solid-state imaging body having a crystal defect in a semiconductor element at a position as shown in FIG. 3, for example. It is assumed that X _{1 to} X ₃ are crystal defects. Then, the memory stores one crystal defect in 24 bits. Of the 24 bits, 12 bits indicate the absolute value in the horizontal direction, and 12 bits indicate the distance in the vertical direction. For example, in the case of crystal defects X _1, when a reference point X ₀ of at scanning problems during a first horizontal scanning line of the field, respectively 2 Since the X ₀ point third horizontally, the second line in the vertical direction XX0000000110 (However, the bit indicated by X is coded and inserted as data indicating which solid-state imaging body is described later.) The encoded data is stored in the memory element. In the case of crystal defects X _2, 5 position from X ₀ point in the horizontal direction, and each binarized since the third line in the vertical direction from the X ₁ point, horizontal absolute position ......... XX0000000110 vertical relative distance ......... XX0000000011 and the encoded data is stored in the memory element. Further, in the case of crystal defects X _3, in the horizontal direction from X ₀ point
Since it is on the second line in the vertical direction from the 509th X ₂ point, it is converted into a binary number and encoded as a horizontal absolute position XX0111111101 vertical relative distance XX0000000010, and the encoded data is stored in the memory element. Let it.

By storing as described above, for example, when there are three crystal defects as described above, only 24 bits × 3 = 72 bits is required, and a memory element with a small capacity can be used.

FIG. 4 shows an example of a noise elimination circuit using a memory in which a crystal defect of a semiconductor element is stored as described above. The CCD transfer system used in this embodiment is an interline transfer system as shown in FIG.

Since the configuration is well known, a brief description will be given. As shown in FIG. 5, a large number of picture elements (2) are arranged in a vertical direction and electric charges are transferred to one picture element row. And a vertical shift register (3) is provided. The charges transferred to the vertical shift register (3) are sequentially transferred to the horizontal shift register (4) one picture element at a time, and a signal is read out through a terminal (5). It is.

Then, the following drive pulse is supplied to the CCD (10). P _I is an imaging pulse supplied to each picture element (2), P _V is a transfer pulse supplied to the register (3), and P _H is a read pulse supplied to the horizontal shift register (4). .

As shown in FIG. 4, the CCD (10) has a desired subject (1) as shown in FIG.
1) is projected via the optical system (12), and the imaging output obtained at the terminal (5) is guided to the output terminal (14) via the sampling and holding circuit (13). Further, the above-described driving pulse obtained by the scanning circuit (15) is supplied to the CCD (10).
(20) indicates a memory element (ROM in the embodiment) in which crystal defects are encoded and stored, and (21) indicates a synchronization signal generator.
Here, the operation of storing the crystal defects in the ROM (20) is performed by examining the crystal defects of the semiconductor element of the CCD (10) used in manufacturing the noise elimination circuit, and encoding and storing the crystal defects if any. There is. And the synchronization signal generator (21)
Supplies horizontal and vertical synchronizing signals to the scanning circuit (15), and the synchronizing signals supply the sampling pulse generator (1).
Supplying the sampling pulse P _S synchronized with the above-mentioned read pulse P _H 6) to the sampling hold circuit (13). The sampling hold circuit (13) by the sampling pulse P _S is controlled, the imaging signal is outputted to the output terminal (14).

Here, when performing noise removal due to crystal defects of the CCD (10), the scanning circuit (15) is used during the blanking period of the synchronization signal supplied from the synchronization signal generator (21) to the scanning circuit (15). An address is designated from the address designating circuit (19) to the ROM (20), and the 24-bit data of the designated address stored in the ROM (20) is decoded by the decoder (18) in the scanning circuit (15). To supply. Then, the 24-bit encoded data supplied to the decoder (18) is decoded and temporarily stored in the memory (17), and the supply of the imaging signal from the CCD (10) to the sampling and holding circuit (13) is performed. when the line sometimes have crystal defects constitute a sampling pulse generator by the data from the memory (17) from (16) so as to hold the front of the signal does not supply the sampling pulses P _S. That is, as shown in FIG. 6, if there is a crystal defect Xa during one horizontal scanning period, data is read from the ROM (20) during the previous horizontal blanking period, and the data is read at point Xa during the scanning period. comes to not supply the sampling pulse P _S, is held the previous signal.

By removing the noise of the crystal defect as described above, the position of the crystal defect is encoded and stored, so that the memory capacity can be significantly reduced.

On the other hand, as a solid-state imaging device using a solid-state imaging body composed of a semiconductor device such as a CCD, the three primary colors of red, green, and blue are each converted into a single-color imaging signal by an individual solid-state imaging body, and this individual imaging signal is converted. 2. Description of the Related Art There is an image pickup apparatus for color video in which a color image pickup signal is mixed. FIG. 7 is a diagram showing an example of a noise elimination circuit of this type of solid-state image pickup device for color video. As a solid-state image pickup device, a CCD for red (10R) and a CCD for green (1R) are used.
0G) and a blue CCD (10B).
0R), (10G) and (10B) image pickup signals are sampled and held by red, green and blue sampling and holding circuits (13R) and (13R).
G) and (13B) to the signal processing circuit (24). Here, a sampling pulse is supplied from the scanning system circuit (15) to each of the sampling and holding circuits (13R), (13G) and (13B) in the same manner as in FIG. By performing the removal, the color image pickup signal from which the noise has been removed by the signal processing circuit (24) is synthesized.

D Problems to be Solved by the Invention However, as described above, a solid-state image pickup device for color video using three solid-state image pickup devices, as shown in FIG. There is an inconvenience that a ROM as a memory to be supplied is required for each solid-state imaging device. That is, since the crystal defects generated in the semiconductor elements of the respective solid-state imaging devices are not the same, different data is required for each solid-state imaging device. FIG. 8 is a view showing an example of a crystal defect of a semiconductor element constituting the solid-state imaging device. FIG. 8A shows a CCD for red (10R), and FIG. 8B shows a CCD for green (10G). 8C shows a blue CCD (10B). Crystal defects Y ₁ in the absolute distance from the upper left scanning start point (the third line in the vertical direction, the second horizontal direction) to the red CCD (10R), crystal defects Y ₂ is (2 line in the vertical direction ,
And in the horizontal direction in the fourth), the fourth line for green CCD (10G) crystal defects Y ₃ also absolute distances in the (vertical, and a horizontal direction in the second), blue CCD (10B )
(First line in the vertical direction, the second horizontal direction) also in absolute distance crystal defects Y ₄ are the crystal defects Y ₅ is referred to as being (6 line in the vertical direction, the fifth in the horizontal direction). In this case, the crystal defects Y ₁ to Y ₅ is in Figure 3 embodiment as well as respective coding described above, the data of the crystal defects Y ₁ and Y ₂ red ROM (2
0R) to be stored, the data of crystal defects Y ₃ is green ROM (20
G) to be stored, the data of crystal defects Y ₄ and Y ₅ ROM for blue
(20B). Then, each ROM (20R), (2
Depending on the data from 0G) and (20B), each color of sample and hold circuits (13R), to create a sampling pulse P _S is supplied to the (13G) and (13B), performing noise elimination by the sampling pulse P _S Things.

As described above, the number of ROMs (20R), (20G), and (20B) required for the number of CCDs (10R), (10G), and (10B) is because the cost of the ROM is high and the configuration of the noise elimination circuit is high. Cost increases, and the circuit configuration becomes complicated.

In view of the above points, the present invention can share a memory.
It is an object of the present invention to provide a noise elimination circuit for a color video solid-state imaging device including a plurality of solid-state imaging bodies.

E Means for Solving the Problems The noise elimination circuit of the solid-state image pickup device for color video of the present invention comprises, as shown in FIG. 1, for example, three solid-state image pickup devices (10R) for obtaining primary color signals composed of semiconductor elements. ), (10G) and (10B), first data indicating the crystal defect positions of the three solid-state imaging devices (10R), (10G) and (10B), and three solid-state imaging devices (10G) and (10B). 10R), (10G) and (10B)
(20) for storing second data indicating which one has a crystal defect, and three solid-state imaging members (10R) and (10G) based on an output signal of the memory (20). ) And (10B) a sampling and holding circuit for sampling and holding the imaging signal output, and the imaging signal output for sampling and holding the first data with the second data stored in the memory (20) is any solid state. The noise is removed by determining whether the output is from the imaging bodies (10R), (10G) and (10B).

F function The noise elimination circuit of the solid-state image pickup device for color video of the present invention comprises a memory (20) having crystal defect position data and data indicating which of the solid-state image pickup bodies (10R), (10G) and (10B) are present. , Noise can be removed by a single memory (20) due to crystal defects of the semiconductor elements of all the solid-state imaging elements (10R), (10G) and (10B).

G Embodiment Hereinafter, an embodiment of a noise removing circuit of the solid-state imaging device for color video of the present invention will be described with reference to FIG. In FIG. 1, parts corresponding to those in FIGS. 2 to 8 are denoted by the same reference numerals, and detailed description thereof will be omitted.

Example of data stored in G1 memory First, data stored in the ROM (20) is shown below. Vertical and horizontal data indicating the location of crystal defects
The bits are coded and stored in the same manner as the coding in the example of FIG. 3 described above, and the three CCDs are stored in both or one of the upper two bits.
Data indicating which of (10R), (10G) and (10B) has a crystal defect is encoded and stored.

For example, red as with FIG. 8 example above, green, and blue CCD (10R), when it is assumed that there is a crystal defect Y ₁ to Y ₅ in (10G) and (10B), following an example of the encoding Shown in

First, the crystal defects Y _{1 to} Y ₅ are arranged in the scanning line order, that is, in the ROM (2
Arrange in order of addresses stored in 0), red R, green G, blue B
The vertical direction V indicates the relative distance from the immediately preceding crystal defect position, and the horizontal direction H indicates the absolute distance from the leftmost scanning start point. Y ₄ ... (B, V1 line, H2 th) Y ₂ ...... (R, V1 line, H4 th) Y ₁ ...... (R, V1 line, H2 th) Y ₃ ...... (G, V1 line, H2 th) Y ₅ ...... ( B, V2 line, H5th). Here, red R is encoded to 00, green G to 01, blue B to 10 and 2 bits, vertical and horizontal position data are encoded to 10 bits by the above-described method, and the codes of R, G, B are respectively assigned. If the upper two bits of the position data are, for example, a blue B CCD
Crystal defects Y ₄ in (10B), the crystal defects Y ₂ in the CCD (10R) of the horizontal absolute position ......... 100000000010 vertical relative position ......... 100000000001 red R is horizontal absolute position ......... 000000000100 vertical relative position ......... crystal defects Y ₃ in the CCD (10G) of 000000000001 green G is a horizontal absolute position ......... 010000000010 vertical relative position ......... 010,000,000,001.

 The encoded data is stored in the ROM (20).

G2 Configuration of Noise Elimination Circuit As shown in FIG. 1, the noise elimination circuit according to the present embodiment operates during the blanking period of the synchronization signal supplied from the synchronization signal generator (21) to the scanning system circuit (15). An address is designated from the address designating circuit (19) of the circuit (15) to the ROM (20), and the above-mentioned 24-bit data of the designated address stored in the ROM (20) is scanned by the scanning circuit (15). To the separation circuit (22). From the 24-bit data, the separation circuit (22) outputs data in the vertical and horizontal directions, respectively.
This is a circuit for separating bit data into high-order two-bit data and low-order ten-bit data. The separated upper two bits of data are supplied to a decoder (23), which decodes the code of the data and supplies the decoded signal to a sampling pulse generator (16). The separated lower 10-bit data is supplied to a decoder (18). The decoder (18) decodes the code of the data, temporarily stores it in a memory (17), and then supplies it to a sampling pulse generator (16). And each CCD (10R), (10
G) and (10B) to the respective sampling and holding circuits (13R), (13G) and (13B), when a line with a crystal defect is present at the time of supply of the imaging signal, the data from the memory (17) and the decoder (23) CCD (1)
Sampling and holding circuits (13R), (13G) and (13B) to which imaging signals are supplied from (0R), (10G) and (10B)
To, in the manner to hold the previous signal without supplying the sampling pulse P _S from the sampling pulse generator (16),
Noise removal due to crystal defects is performed.

Here, in the sampling pulse generator (16), the sampling hold circuit (13) connected to any of the CCDs (10R), (10G) and (10B) based on the upper two bits of data.
R), sampling (13G) and (decide to stop the supply of the sampling pulse P _S to 13B), one of CCD selected by data of the lower 10 bits (10R), (10G) and (10B) position for stopping the supply of the pulse P _S, is intended to denoising.

By doing the above, ROM (2
0) is one CCD but three CCDs (10R), (10G)
And (10B) noise removal due to crystal defects of the semiconductor element can be performed. For this reason, CCD (10R) as a solid-state image sensor,
The number of parts can be reduced as compared with the conventional case that requires ROMs (20) by the number of (10G) and (10B), which leads to a reduction in manufacturing cost.

The crystal defect data stored in the ROM (20) needs only 24 bits if the above encoding is performed.
For example, if a ROM (20) having 256 addresses is used, 4 bits can be stored at each address, so that 1024 bits, that is, 42 crystal defect data can be stored, and in fact, one CCD (10)
Rarely have more than 10 crystal defects in the ROM
There is no shortage of storage capacity of (20).

In addition, the present invention is not limited to the above-described embodiment, and it goes without saying that various other configurations can be adopted without departing from the spirit of the present invention.

H According to the noise elimination circuit of the color video solid-state imaging device of the present invention, the memory stores crystal defect position data and data indicating which solid-state imaging device is present, By selecting a solid-state imaging device based on the data indicating whether the solid-state imaging device is present, noise removal due to crystal defects of the semiconductor elements of all the solid-state imaging devices can be performed with one memory, and the memory can be reduced. There is an advantage that the cost required for the circuit configuration is reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a noise removing circuit of a solid-state image pickup device for color video according to the present invention, and FIGS. 2, 3, 5, 6, and 8 each show a conventional circuit. FIGS. 4 and 7 are diagrams each illustrating a configuration of a conventional noise elimination circuit of a solid-state imaging device. (10R) is a red CCD, (10G) is a green CCD, (10B) is a blue CCD, (13R), (13G) and (13B) are sampling and hold circuits, (15) is a scanning circuit, 20) RO
M.

Claims (1)

(57) [Claims] 1. Three solid-state imaging devices for obtaining a primary color signal composed of a semiconductor element, first information indicating a crystal defect position of the three solid-state imaging objects, and the first information being the third information. The second information indicating which one of the solid-state imaging objects is the information indicating the crystal defect position of the solid-state imaging object is set to 1 according to a predetermined format.
A memory for storing as unit data; information extracting means for extracting the first information and the second information from the one unit data read from the memory in accordance with the predetermined format; Three sampling and holding circuits for sampling and holding the imaging signal of the solid-state imaging body; and the first information related to the extracted second information based on the second information extracted by the information extracting means. Identifies which of the three solid-state imaging objects is the information about the solid-state imaging body, and at a timing based on the first information, an image of the solid-state imaging body determined based on the second information A noise removal circuit for a color video solid-state imaging device, comprising: a control unit for controlling a sampling and holding circuit from which an output is obtained.