JP2000115644A - Solid-state image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image pickup device for performing effective correction to defective pixels and superior improving image quality, without making the constitution of a storage circuit or the like to a large scale. SOLUTION: In order to control the entire system of a video camera, a CPU 11 is provided with a key input part 12, an EEPROM control part 13, a defect detection/correction information preparation part 14, a camera signal control part 15, a TG control part 16 and a diaphragm control part 17. Also, the CPU 11 is provided with an EEPROM 18 as a storage means and a start key 19, a detection level setting key 20, an area-setting key 21 and a priority setting key 22, etc., as operation means. Thus, an image pickup area is sectioned by the area setting key 21, and the priority of the defect correction is attached by the priority-setting key 22. Also, the level of a defect is set by the detection level setting key 20 and the defect is corrected in the priority order of the area and in the order of level of the defects.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid-state imaging device, and more particularly, to a solid-state imaging device having a function of correcting a signal output of a defective pixel.

[0002]

2. Description of the Related Art In a solid-state image pickup device formed of a semiconductor such as a CCD, a defective pixel whose sensitivity is lowered due to a local crystal defect of the semiconductor or the like sometimes occurs. Conventionally, various methods have been proposed for correcting the image quality deterioration caused by the imaging output of the defective pixel by signal processing. As an example, defect data on defective pixels included in a solid-state imaging device is detected at a semiconductor factory where it is manufactured and stored in a non-volatile memory such as a ROM, and is stored in the non-volatile memory during normal photographing. There is a method of specifying a defective pixel based on the defective data and correcting the imaging output.

[0003] On the other hand, with respect to defective pixels that occur after commercialization due to electrostatic destruction or aging of the solid-state imaging device, the video camera is provided with a defect detection and defect correction function. . As a method for detecting defective pixels on the video camera side as shown in FIG. 5, the entire area of the imaging surface 31 of the CCD 3 which is conventionally a solid-state image sensor is set as a defective pixel detection range, and all pixels within the range are detected. Are sequentially scanned in the normal scanning order to obtain light amount data of each pixel, and the light amount data is compared with a predetermined defect threshold value, and those larger than the defect threshold value are regarded as defective pixels. On the other hand, the correction is performed in the order of the pixels having the higher defect levels.

The imaging surface 31 of the CCD 3 is composed of an effective pixel area 32 output as an image, and an invalid pixel area 33 which is output as a black level and does not become an image. On the other hand, when the above-described defect correction is applied, the defective pixel g and the defective pixel h become the effective pixel area 3
The correction is performed in ascending order of the defect level without distinguishing whether the pixel belongs to the pixel group 2 or the invalid pixel area 33.

As a result, if there are many pixels having a defect level higher than that of the effective pixel region 32 in the invalid pixel region 33, the correction of those defective pixels is performed first. However, there was a problem that the operation was not performed sufficiently. In addition, there is a problem that the configuration of the storage circuit and the like becomes large-scale when it is attempted to correct a large number of defective pixels.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a solid-state imaging device which can effectively correct defective pixels without increasing the size of a memory circuit or the like and can improve the image quality. Is to do.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems, and has been made in consideration of the above-mentioned problems, and has an area dividing means for dividing an imaging area of a solid-state image sensor into a plurality of areas; For each of the regions, a defective pixel, a defective pixel detecting unit for detecting an output signal level of the defective pixel, a storage unit for storing information on a defect of the defective pixel, and a region divided by the region dividing unit Priority setting means for setting the priority of defect correction; priority order of the area set by the priority setting means; and further, the level order of the output signal of the defective pixel detected by the defective pixel detecting means. According to, the output signal of the defective pixel is stored in the storage means, comprising a defect correction means for correcting based on information about the defect, comprising a solid-state imaging device, To solve the serial problems.

According to the solid-state imaging device of the present invention, the correction area for the defective pixel can be divided into an arbitrary number of areas, the divided areas can be set with a priority, and the output signal level of the defective pixel in that area can be set. It can be corrected in order of size. Therefore,
Within the predetermined correctable number range, correction is performed in the priority order of the areas and in the order of the magnitude of the output signal level of the defective pixel in the area. Can be focused on, and effective image quality can be improved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention divides an image pickup area of a CCD into a plurality of areas, assigns priorities to the respective areas, and sets a range of the number of correctable numbers in the order of priority and the order of the defect level. The solid-state imaging device is characterized in that the defect correction is performed within the device, and the defect in the central region where the image quality is conspicuous is mainly corrected to improve the image quality.

Next, an embodiment will be described with reference to FIGS. FIG. 1 is a system configuration diagram for performing defect correction, FIG. 2 is a diagram showing a divided area of a CCD and positions of defective pixels, FIG. 3 is a flowchart of defect correction, and FIG. It is a flowchart of the operation which selects a defective pixel and determines an order.

First, a system configuration for defect correction according to the present invention will be described with reference to FIG. This system has a means for designating a priority area for defect correction. When an instruction to perform defect correction is given, the priority area and the detection level are set for the correction means, and a white defect (hereinafter, white defect) is set. Are abbreviated as “defects”), the priority is set in an area to be corrected, and the correction order is set in the same area in descending order of the defect level.

The system is composed of an aperture 1, a lens 2 and a C
The optical system of the video camera is composed of the CD 3, a sample / hold circuit (S / H) 4 for sampling a video signal from the CCD 3, and an analog / digital converter (A / H) for converting the sampled video signal into a digital signal.
D) 5, a camera signal processing unit 6 for processing the digitized video signal, a defect detection circuit 7 for detecting a defect from the output of the CCD 3, a defect correction circuit 8 for correcting the defect and outputting an image, and an aperture 1. Control circuit 9 for controlling the CCD
TG (Timing Generator) 1 for accumulating electric charge in 3
0 is connected.

A CPU 11 is used to control the entire video camera system. CPU11
Is a key input unit 12, an EEPROM,
(Electric Erasable Program ROM) control unit 13, defect detection / correction information creation unit 14, camera signal control unit 15, T
It has a G control unit 16 and an aperture control unit 17. Also, C
The PU 11 is provided with an EEPROM 18 as storage means, a start key 19, a detection level setting key 20, an area setting key 21, a priority setting key 22 and the like as operation means. Incidentally, the internal configuration of the CPU 11 may be constituted by individual circuits.

Next, the operation of the system will be described.
First, the subject 23 is CCD from the aperture 1 through the lens 2
3 and is converted into an image signal. An analog signal of an image output from the CCD 3 is sampled by a sample and hold circuit 4 and converted into a digital signal by an analog / digital converter 5. This digital signal is subjected to normal signal processing by a camera signal processing unit 6 and supplied to a defect detection circuit 7 and a defect correction circuit 8 for defect correction.

When an instruction for a correction operation is input from the start key 19, the key input unit 12 receives the instruction and performs EE.
The PROM control unit 13 is instructed to read the information on the defect detection level and the correction priority from the EEPROM 18, and at the same time, the camera signal control unit 15, the TG control unit 16,
It notifies the aperture control unit 17 that it is in the defect correction operation state.

The EEPROM 18 stores defect data information detected by the defect detection circuit 7, detection level information set by a detection level setting key 20, information of an area division set by an area setting key 21, and priority setting. Information on the priority of each area set by the key 22 is recorded.
Further, defect information measured in a manufacturing process when the CCD 3 is manufactured may be recorded.

The EEPROM control unit 13 includes an EEPROM 1
8 is input to the defect detection / correction information creation unit 14, where information for the defect detection circuit 7 and the defect correction circuit 8 is created based on this information. The correction signal is supplied to the correction circuit 8. In addition, since the detection of the defective pixel is performed in a state where light is not irradiated to the CCD 3, the aperture control unit 17 instructs the aperture control circuit 9 to close the aperture 1 in order to block external light,
The G control unit 16 controls the TG 10 so that the CCD 3 is in the charge accumulation state. Also, the camera signal control unit 15
Indicates to the defect detection circuit 7 and the defect correction circuit 8 that they are in the state of defect detection and defect correction.

In the above-mentioned state, in the video signal photographed by the CCD 3, the defect of the pixel is corrected in the order of the priority of the region and further in the order of the size of the defect in the region, and is output as an improved video signal. .

Next, a description will be given of the relationship between the area division and the priority order, the defect level and the correction order, which characterize the present invention.

As shown in FIG. 2, a defective pixel a
To f, defective pixels a and b are located in area A, defective pixels c and
It is assumed that d exists in the area B, and the defective pixels e and f exist in the area C. The area A is represented by coordinates A ₀ (x _A0 , y _A0 ) and A
₁ (x _A1 , y _A1 ) is a rectangular area having a diagonal line, and an area B is an area from a rectangular area having coordinates B ₀ (x _B0 , y _B0 ) and B ₁ (x _B1 , y _B1 ) as a diagonal line. A is a region excluding A, and a region C is a region obtained by excluding the regions A and B from the imaging surface 31.

As shown in Table 1, the defect levels of defective pixels are higher in the order of defective pixels a and b in area A, defective pixels c and d in area B, and defective pixels e and f in area C. And Note that “1024” in Table 1 is the full scale of the output.

[Table 1]

Further, as shown in Table 2, the priority of defect correction is higher in the order of area A, area B, and area C.

[Table 2]

In the detection level selection, the selection stage is set from "0" to "3" as shown in Table 3, but here "1" of the detection level selection is selected. At this detection level, all pixels having an output level of “16/1024” or more are detected as defective pixels. still,
“16/1024” indicates a level at which the output is “16” when the full scale of the output is “1024” with the aperture closed.

[Table 3]

By the way, it is only necessary to detect all defective pixels and correct them all.
However, as described in the conventional example, the number that can be corrected is actually limited in terms of the circuit scale and the like. In this example, assuming that the number that can be corrected is three and the detection level selection is “1”, as can be seen from Table 1, all six defective pixels a to f are detected. Therefore, three can be corrected, but the remaining three cannot.

Next, the selection of the three corrections will be described. First, correction is performed from the defective pixel in the area A having the highest priority according to Table 2. In the region A, the defect level is “24/1
024 ”and the defect level“ 18/102 ”
4 ”defective pixel b. Since the defective pixel a has a higher defect level than the defective pixel b, the defective pixel a is corrected first, and then the defective pixel b is corrected.

Since the number of correctable pixels is less than three, the defective pixel in the area B having the next highest priority is corrected. Area B
Has a defective pixel c with a defect level of “28/1024”;
There are two defective pixels d having a defect level of “22/1024”, but the defective pixel c is corrected first because the defective pixel c has a higher defect level than the defective pixel d. Since the upper limit of the number that can be corrected is reached, the correction is completed, and the correction of the defective pixel d and the defective pixels e and f in the area C is not performed.

As described above, the defective pixels a, b, and c are corrected. However, in the conventional method, the correction is performed in order from the one having the highest defect level in the entire area of the imaging surface. The correction was performed in the order of the pixels c, e, and a. In this case, the defective pixel b in the area A set at the center of the screen is not corrected, so that the defect near the center, which has a great effect on the image quality, remains as it is. Thus, the quality of the displayed image is improved.

Next, the above-described defect correction will be described with reference to the flowchart of FIG.

First, when an instruction for defect detection / defect correction is input from the start key 19, the defect detection / correction information creation unit 1 is operated based on the data read from the EEPROM 18.
In step 4, setting of a defect detection level (step S101) and setting of a defect detection area (step S102) are performed and transmitted to the defect detection circuit 7. Next, the aperture 1 is closed via the aperture control circuit 9 with a signal from the aperture control unit 17 to block external light (step S103), and a signal from the TG control unit 16 is used to facilitate defect detection. To set the CCD 3 to the accumulation mode via the TG 10 (step S10).
4). Thereafter, the defect is detected by the defect detection circuit 7, and the defect is corrected by the defect correction circuit 8 (step S105).

Next, the selection of a defect to be corrected in step S105 will be described in detail with reference to the flowchart of FIG. The symbols used in FIG. 4 represent the following, respectively. i: area number j: defect correction number k: number of detected defects in area i 1: defect list of area i m: correction list n: detection counter I _max : maximum number of areas J _max : maximum number of correctable areas

First, initialization is performed, and the area number i of the area divided into a predetermined number is set to 0 (step S20).
1). Next area number i increased by route returned from the step 208 it is determined whether or not exceeded the maximum number I _max in the region (step S202), if the past (No), the area to be treated Since there is no correction priority order, the process of the correction priority order ends.

If it does not exceed at step S202 (Y
es), the number of defective pixels in the area with the area number i is detected (step S203). Next, a defect list 1 is created for the defective pixel detected in the area of the area number i (step S204). The defect list 1 is arranged in the descending order of the detection level to prepare for determining the correction priority in the area of the area number i (step S205).

Next, the detection counter n is cleared (step S206), and it is determined whether or not the number _Jmax that can be corrected in all regions of the CCD is not exceeded (step S207). If it exceeds (No), it means that the upper limit of the correctable number has been reached, the area number i is changed to i + 1, and the area is changed to the area of the next priority (step S208). Steps up to S207 are repeated. The area number i becomes the maximum number I by a predetermined repetition.
_If it exceeds _max , the process proceeds from step S202 to the end of the process.

If it does not exceed at step S207 (Y
es) It is determined whether or not the number k detected by the counter n in the area i does not exceed k (step S209). If it exceeds (No), it means that the list of the area i has disappeared, and the area number i is changed to i +
The area is changed to the next priority area as 1 and step S20
Returning to step 2, step S209 is repeated again. If region i in this process is greater than the maximum number of I _max step S2
From 02, the process ends.

On the other hand, if it does not exceed (Yes), the sorted defect list 1 is corrected to the correction list m in descending order of level.
(Step S210). Next, the defect correction number j is set to j + 1 (step S211), the detection counter n is set to n + 1 (step S212), and the process returns to step S207, and the priority is similarly added to the correction list m, and the number of defects that can be corrected is determined. The priority order is determined for the pixels.

In this embodiment, the case where a high-priority area is selected at the center of the screen has been described. However, the present invention is not limited to this, and a high priority may be set by focusing on an arbitrary area. . In addition, it goes without saying that the setting is not limited to setting the next priority area including the high priority area, but may be set dispersedly on the screen.

[0037]

Therefore, according to the solid-state imaging device of the present invention,
Since the correction is preferentially performed on the defective pixels in the area effective for improving the image quality without increasing the size of the configuration of the storage circuit and the like, the quality of the displayed image can be visually improved.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram for performing defect correction.

FIG. 2 is a diagram showing a divided area of a CCD and positions of defective pixels.

FIG. 3 is a flowchart of defect correction.

FIG. 4 is a flowchart relating to selection of a defective pixel to be corrected.

FIG. 5 is a diagram for explaining a conventional defect correction of a CCD.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Aperture, 2 ... Lens, 3 ... CCD, 4 ... Sample hold circuit, 5 ... Analog-to-digital converter, 6 ... Camera signal processing unit, 7 ... Defect detection circuit, 8 ... Defect correction circuit, 9 ... Aperture control circuit, 10 TG, 11 CPU, 1
2 key input unit, 13 EEPROM control unit, 14 defect detection / correction information creation unit, 15 camera signal control unit, 1
6 TG control unit, 17 iris control unit, 18 EEPRO
M, 19: start key, 20: detection level setting key,
21 ... area setting key, 22 ... priority setting key, 23 ...
Subject, 31: imaging surface, 32: effective pixel area, 33: invalid pixel area, ah: defective pixel

Claims (1)

[Claims] A region dividing unit that divides an imaging region of the solid-state imaging device into a plurality of regions; a defective pixel and an output signal level of the defective pixel for each of the regions divided by the region dividing unit. Defective pixel detecting means for detecting; storage means for storing information on the defect of the defective pixel; priority setting means for setting a priority of defect correction for the area divided by the area dividing means; Means for storing the output signals of the defective pixels in the storage means in accordance with the priority order of the areas set by the means and further according to the level order of the output signals of the defective pixels detected by the defective pixel detection means. A solid-state imaging device, comprising: a defect correction unit configured to perform correction based on information related to the solid-state imaging device.