JPH09205586A - Defective picture element detecting and correcting system for ccd solid-state image pickup element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a defective picture element detecting and correcting system by which a CCD camera is not required to make defective picture element detection for every start and a defective picture element other than a white level point is corrected without remarkable design change or cost increase. SOLUTION: Information relating to addresses of all defective picture elements and levels once detected are stored in a nonvolatile memory 11 provided at the outside of a conventional defective picture element detection correction IC 13 and the storage content of the nonvolatile memory 11 is transferred automatically to nonvolatile memories 17-18 in the defective picture element detection correction IC 13 at image pickup at start after power interruption. Then the correction is made by using the storage content of the nonvolatile memories 17-18 in IC.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects an abnormal defective pixel in a solid-state image pickup device of a CCD camera, and corrects a pixel corresponding to the defective CCD (referred to as a defective pixel) to a normal pixel. The present invention relates to a defect detection and correction system for a CCD solid-state image sensor.

[0002]

2. Description of the Related Art In a CCD camera, external light incident through a lens is received by a solid-state image pickup element formed by arranging a large number of light receiving elements (so-called sensors) in a matrix in a plane. Each light receiving element (sensor)
An analog electric signal having a magnitude corresponding to the amount of light received at each position coordinate is output.

The output of each light receiving element (sensor) of the solid-state image pickup device is scanned and converted into digital signals one by one by an A / D converter, and then supplied to a signal processing circuit. The signal processing circuit converts the digital signal into a display signal and supplies the display signal to the display. As a result, an image corresponding to the sensor matrix on a one-to-one basis is displayed on the screen of the display.

However, it is inevitable that a large number of pixels forming the solid-state image pickup device include defective products that do not generate an electric signal of a predetermined level, and a display corresponding to such a pixel is inevitable. Pixels on the screen are so-called defective pixels that do not have normal brightness.

The defective pixels are classified into white dot defective pixels and black dot defective pixels. The defective pixel of the white dot is due to a defective CCD that outputs an electric signal of a predetermined magnitude or more with respect to the amount of incident light, and the brightness is stronger and brighter than that of a normal pixel, which is a so-called white dot. In addition, the defective pixel with black dots is due to a pixel that outputs an electric signal having a magnitude equal to or smaller than a predetermined value with respect to the amount of incident light, and has a lower brightness and a darker brightness than a normal pixel.

Conventionally, manufacturing measures have been taken to eliminate CCDs having defective pixels as much as possible. However, in preparation for a CCD having defective pixels, a solid-state image sensor of a CCD camera and a signal processing circuit are prepared. A defective pixel detection / correction circuit for detecting a defective pixel and correcting the defective pixel is provided between and, and is generally integrated into an IC.

C equipped with a conventional defective pixel detection / correction IC
In the CD camera, the defective pixel detection operation is performed as follows. At startup, the incident light of the solid-state image sensor is made zero by an operation such as closing the iris, the output level of each pixel is compared with a predetermined reference value, and a pixel with an output above this reference value is detected and this is defective. Certified as a pixel. Then, the detected position or address of the defective pixel on the matrix is stored in the RAM, which is a volatile memory in the IC.

The correction operation of the defective pixel at the time of image pickup is performed as follows. R, which is a volatile memory when detected
Correction is performed by replacing the output of the sensor having the address matching the address stored in AM with the output of the normal pixel in the vicinity.

[0009]

However, since the RAM of the conventional defective pixel detection / correction IC is a volatile memory, the power of the camera system is shut off and the defective pixel information stored therein is erased. I will end up. Therefore, there is a problem in that the operation for detecting and storing the defective pixel as described above must be performed every time the camera system is started.

Further, the above-mentioned conventional defective pixel detection / correction IC
In principle, since only defective pixels with white dots can be detected, there is a problem that pixels other than white dots cannot be removed from the screen.

Further, the above conventional defective pixel detection / correction IC
However, there is a problem in that it cannot be used in the case of a CCD camera that does not have a mechanical iris for adjusting the light amount by controlling the load accumulation time.

On the other hand, a non-volatile memory may be used in place of the RAM which is a volatile memory for storing defective pixels of the defective pixel detection / correction IC, but there are problems in manufacturing and problems such as memory capacity. There is also a cost problem.

Therefore, the present invention solves the problems of the conventional defective pixel detection / correction system described above, and it is not necessary to perform the operation for defective pixel detection even after the power is interrupted, and the defective pixels other than the white dots are also corrected. There is a problem in a defective pixel detection / correction system for a CCD solid-state image sensor that can be applied to a camera that does not have a mechanical iris for automatic light amount adjustment.

[0014]

In order to solve the above problems, a defective pixel detection / correction system for a CCD solid-state image pickup device according to the present invention addresses defective pixels in a large number of sensors constituting the CCD solid-state image pickup device. And information regarding the output level are stored in the non-volatile memory, and the information is automatically supplied from the non-volatile memory to the correction means for correcting the signal of the defective pixel at the time of imaging.

With the above configuration, even if the power of the image pickup system is turned off, the defective pixel information is not erased because it is stored in the nonvolatile memory. At the time of start-up after interruption of the power supply, the defective pixel information is automatically read from the non-volatile memory and supplied to the correction means, so it is not necessary to carry out an operation for detecting the defective pixel every time of start-up.

Further, the non-volatile memory stores not only the information on the defective pixels of white dots detected by the integrated circuit for defective pixel detection and correction, but also the information on the defective pixels of black dots detected by other means. , Is supplied to the correction means for correcting the signal of the defective pixel at the time of image pickup. Therefore, the correction range of the defective pixel is widened, and the defective pixel such as the black dot can be corrected without being limited to the defective pixel of the white point, so that the screen quality is improved.

Further, if a defective pixel is detected and stored in a non-volatile memory, the defective pixel information is not erased. Therefore, even a CCD camera, for example, which has no mechanical iris for adjusting the incident light quantity of the solid-state image pickup device at the time of image pickup. Can be applied.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The most preferable embodiment of the defective pixel detection / correction system for a CCD solid-state image pickup device according to the present invention is applied to a CCD camera, and as shown in FIG. A defect level memory 7 including a unit 2, an AGC circuit 3 corresponding to a detection unit and a correction unit, an A / D converter 4, a defect correction circuit 5, a comparator 6, and a RAM that is a volatile memory. A defective address memory 8 composed of a volatile memory RAM, an address counter 9, a microcomputer 10, an EEPROM 11 corresponding to a nonvolatile memory, and a signal processing circuit 1.
And 2.

The optical system 1 is composed of a plurality of lenses and receives light from a subject of a CCD camera and outputs it to the CCD solid-state image pickup section 2. The optical system 1 has a mechanical iris so that the amount of incident light can be adjusted. The mechanical iris is not essential for the defective pixel detection correction according to the present invention.

The CCD solid-state image pickup unit 2 is constructed by arranging a large number of sensors in a matrix of M rows and N columns in a plane perpendicular to the light emitted from the optical system 1. That is, this sensor matrix corresponds to a shooting screen. These sensors output in parallel electric signals having a magnitude corresponding to the amount of incident light.

The position of the sensor in the solid-state image pickup section 2 is represented by a horizontal address and a vertical address. The horizontal address is the order X (where X = 1 to N) in the horizontal line (row) to which the sensor belongs, and the vertical address is the order Y (where Y = 1 in the matrix of the horizontal line to which the sensor belongs).
~ M). In other words, the CCD position is the address (X,
It is represented by Y).

The address (X, Y) of this sensor also corresponds to the position of the pixel on the pixel matrix of the displayed image and 1
One to one.

The output of each row from the first row to the M-th row of the sensor matrix of the solid-state image pickup section 2 is sequentially scanned in the horizontal direction by a scanning circuit (not shown), and as a result, the output signal of each sensor has a period T. Will be output in series to the AGC circuit 3.

The AGC circuit 3 amplifies the output signal from each sensor and outputs it to the A / D converter 4. The A / D converter 4 converts the analog signal from the AGC circuit 3 into a digital signal having a gradual level and outputs it.

In FIG. 1, the defect correction circuit 5, the comparator 6,
A defective pixel detection / correction IC 13 is a portion surrounded by a dotted line, which includes the defect level memory 7, the defect address memory 8, and the address counter 9.

The function of the defective pixel detection / correction IC 13 is as follows.
(1) Detecting a defective pixel of a white dot based on the output signal of the A / D converter 4, (2) Defect pixel of a white dot detected in the defective pixel detection / correction IC 13 and defective pixel detection / correction IC
Each defective pixel information regarding the defective pixel of the black dot detected outside 13 is stored at the time of the correction operation, and (3) it is corrected by replacing all the defective pixels with normal pixels in the vicinity.

The defect correction circuit 5 inputs the output signal of the A / D converter 4 and the correction control signal from the defect address memory 8 at the same time. The defect correction circuit 5 uses the A / D converter 4 when the correction control signal is logic 1 (“1”).
Input signal from the normal CC near the defective pixel CCD
Correction is performed by substituting the output signal of D. or,
In this defect correction circuit 5, the correction control signal is logical 0 ("
In case of 0 ″), the above correction operation is not performed.

The comparator 6 has one input terminal (+) with A /
Input the output signal of D converter 4, and input the other input terminal (-)
A defective pixel detection reference signal (defect detection threshold level signal) is input to and a write control signal is output to the defect level memory 7 and the defect address memory 8.

When the output signal of the sensor is smaller than the threshold level of the defective pixel detection reference signal, the comparator 6 recognizes that the sensor is normal and sets the level of the write control signal to "0". When the output signal of the sensor is equal to or higher than the threshold level, the sensor is recognized as a defective pixel generating a white defective pixel and the level of the write control signal is set to "1".

The defect level memory 7 is composed of a RAM which is a volatile memory, and operates to store the output from the A / D converter 4 under the control of the write control signal from the comparator 6. That is, the level of the write control signal from the comparator 6 is "
When it is 1 ", that is, when there is a defective pixel, the A / D at that time
The output signal of the converter 4 is stored, and when the write control signal is "0", that is, when the pixel is normal, the write operation is not performed.

The defective address memory 8 is composed of a RAM which is a volatile memory, and performs an operation of storing the output of the address counter 9 under the control of the write control signal from the comparator 6. That is, when the write control signal is "1", that is, when the pixel is defective, the address output from the address counter 9 is stored, and when the write control signal is "0", that is, when the pixel is normal. Does not perform a write operation.

Therefore, when the comparator 6 detects the sensor of the defective pixel, the address and the signal level of the defective pixel are stored in the defective address memory 8 and the defective level memory 7, respectively.

The address counter 9 comprises a horizontal counter and a vertical counter. The horizontal counter counts horizontal addresses and the vertical counter counts vertical addresses. The vertical counter repeats counting 1 to M, and the horizontal counter counts 1 to N at each count m of the vertical counter.

The microcomputer 10 is connected to a defect level memory 7 and a defect address memory 8 which are volatile memories by a bus 13, and is connected to an EEPROM 11 which is a non-volatile memory by a bus 14.

The microcomputer 10 performs the following defective pixel input / output function for the defective pixel detection / correction IC 13.

(1) The defective pixel information stored in the defective level memory 7 and the defective address memory 8 which are volatile memories by the defective pixel detection operation in the defective pixel detection / correction IC 13 is read out via the bus 13 and is read out. , EEPROM 11 which is a non-volatile memory.

(2) Information on defective pixels detected by the defective pixel detection means outside the defective pixel detection / correction IC 13 is manually or automatically written in the EEPROM 11.

(3) At the time of restarting after the power supply is interrupted, that is, at the time of imaging, the EEPROM 1 which is a non-volatile memory
All the defective pixel information stored in 1 is read out, and this is written in the defect level memory 7 and the defective address memory 8 which are volatile memories.

The EEPROM 11 is a so-called non-volatile RAM whose stored contents are not lost even when the power is off. EE
In the PROM 11, the microcomputer 10
Information about all defective pixels is stored.

The defective pixel detection / correction system for a solid-state image sensor having the above-described configuration operates as follows.

1. Detecting operation of defective pixel of white spot (1) Image pickup operation is performed with the iris of the camera closed or with the lens cap attached. At this time, since the incident light is zero, there is no incident light on the solid-state imaging unit 2,
Therefore, all sensors must have a zero output signal if normal.

(2) The sensor matrix is scanned in period T. That is, the output of one sensor is A every cycle T.
It is output as a digital signal through the GC circuit 3 and the A / D converter 4, and is input to the defect correction circuit 5 and the comparator 6.

(3) The horizontal counter of the address counter 9 counts at a cycle T and repeats counting 1 to N, and the vertical counter counts at a cycle N and repeats counting 1 to M. When the horizontal counter reaches N, the count of the vertical counter increases by 1, and the horizontal counter returns to 1.

(4) When the output signal of the A / D converter 4 is equal to or higher than the defective pixel detection reference signal level, that is, when the defective pixel is detected, the comparator 6 outputs the defective level memory 7 and the defective address memory 8. The write control signal is set to "1".

(5) When the write control signal is "1", the defective address memory 8 has an address counter 9 at that time.
The horizontal counter and vertical counter counts, that is, the horizontal and vertical addresses of the defective pixel are stored.

(6) When the write control signal is "1", the defect level memory 7 stores the output level of the A / D converter 4 at that time, that is, the output level of the defective pixel. (7) The above-described operation of detecting defective pixels of white dots is performed for all pixels, and the addresses and levels of the detected defective pixels of white dots are stored in the defect level memory 7 and the defective address memory 8.

(8) The level information and the address information stored in the defect level memory 7 and the defect address memory 8 are automatically EEPR by the microcomputer 10.
It is also written and saved in the OM 11.

2. Detection Operation of Black Pixel Defective Pixel (1) The address and level of the black dot defective pixel are detected in a quality inspection or the like at the time of manufacturing the solid-state imaging unit 2. (2) The address and level of the detected black dot defective pixel are manually or automatically written in the EEPROM 11 via the microcomputer 10.

(3) The microcomputer 10 is EE
The address information and the level information of the defective pixel of the black dot written in the PROM 11 are automatically and simultaneously automatically set in the defect level memory 7.
And the defective address memory 8 respectively.

3. Correction operation during image pickup (1) If there is no power cutoff after the defective pixel detection operation,
Since the contents stored in the defect level memory 7 and the defect address memory 8 are not erased, the defect pixel correction operation by the defect correction circuit 5 is performed by the defect level memory 7 and the defect address memory 8 including the defective pixel of the white dot and the defective pixel. All defective pixel information of defective pixels of black dots is used as it is.

(2) When the power is interrupted, the microcomputer 10 automatically reads the information on all defective pixels stored in the EEPROM 11 into the defect level memory 7 and the defective address memory 8 at the time of restart. . Thereafter, the defect correction circuit 5 performs a correction operation using the stored contents of the defect level memory 7 and the defect address memory 8.

(3) The correction operation by the defect correction circuit 5 of the above (1) and (2) is performed as follows. The defect correction circuit 5 has a function of storing the output level of a normal pixel near the defective pixel.

During image pickup, the address counter 9 counts the address of the sensor matrix in synchronization with the scanning of the solid-state image pickup section 2. The defect correction circuit 5 replaces the input signal from the A / D converter 4 with the stored normal level when the count value of the address counter 9 matches the address stored in the defect address memory 8. By outputting, the defective pixel is corrected.

[0054]

As described above, the CC according to the present invention
In the defective pixel detection and correction system of the D solid-state image pickup device, even if the defective pixel information stored in the volatile memory of the defective pixel detection and correction IC disappears due to the interruption of power, the defective pixel information is stored in the nonvolatile memory. Therefore, the following effect is obtained by the configuration in which the defective pixel information is automatically read from the non-volatile memory and rewritten in the volatile memory of the defective pixel detection / correction IC at the time of imaging at the time of restart.

(1) The user does not have to repeat the operation for detecting a defective pixel each time the system is activated, and the operability of the device can be greatly improved. (2) All defective pixels including defective pixels such as black spots including white spots can be corrected, and the image quality is improved. (3) It can also be applied to a CCD camera without a mechanical iris.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a defect detection and correction system for a CCD solid-state image sensor according to the present invention.

[Explanation of symbols]

1 Optical system 2 Solid-state imaging unit 3 AGC circuit
4 A / D converter 5 Defect correction circuit 6 Comparator 7 Defect level memory 8 Defect address memory 9 Address counter 10 Microcomputer 11 EEPROM
12 signal processing circuit 13, 14 bus

Claims (3)

[Claims] 1. A CCD solid-state comprising an image pickup section comprising a large number of CCD solid-state image pickup elements, means for detecting a defective pixel of the CCD solid-state image pickup element, and correction means for correcting a signal of the detected defective pixel. The means for detecting a defective pixel of the image sensor stores information about the address and output level of the defective pixel in a non-volatile memory, and automatically supplies the information from the non-volatile memory to the correction means at the time of imaging. A defective pixel detection / correction system for a CCD solid-state imaging device, which is characterized in that 2. A detection means for detecting a defective pixel of a white spot of a CCD solid-state image pickup device, a volatile memory for storing information on the detected defective pixel, and based on the information stored in the volatile memory, An integrated circuit having a correction unit for correcting a signal of a defective pixel at the time of image pickup, wherein the integrated circuit is provided with a unit for appropriately inputting and outputting information stored in the volatile memory to a nonvolatile memory. A defective pixel detection / correction system for a CCD solid-state image sensor, comprising: 3. The information on the defective pixel of the white spot detected by the detecting means is written in the nonvolatile memory,
Information about defective pixels other than the defective pixel of the white dot is stored in the non-volatile memory, and all the stored defective pixel information is read and written in a volatile memory in the integrated circuit at the time of imaging. A defective pixel detection / correction system for a CCD solid-state image sensor according to claim 2.