JP3514789B2 - CCD video camera system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for constructing a video camera system for inputting a moving image using a CCD image pickup device, and more specifically, a CCD image pickup device having defective pixels is used. The present invention relates to a video camera system for obtaining an image signal having a quality close to or higher than that of a video camera using a defect-free CCD image pickup device.

[0002]

2. Description of the Related Art As a means for inputting an image and converting it into an electric image signal in real time, a two-dimensional CC having a large number of semiconductor light receiving elements formed in a two-dimensional lattice on a silicon substrate.
The D image sensor is generally widely used.

In order to obtain a high-quality image signal using this two-dimensional CCD image pickup device, it is necessary that all the light receiving elements on the CCD image pickup device have no defects. If there is a defect in the CCD image sensor, the signal value obtained from that pixel is significantly different from the signal value of the adjacent pixel,
When the input image signal is displayed on the display device, it is perceived as spots and the image quality is greatly impaired.

To obtain a defect-free CCD image pickup device,
Non-defective products are selected from a large number of manufactured samples by operation confirmation inspection. The yield rate at that time largely depends on the semiconductor manufacturing process technology and the external dimensions of the device, and as a result, greatly affects the cost of the device.

Further, in order to obtain a high quality image signal in the CCD image pickup device, it is required to have a high resolution, that is, a large number of effective pixels. Therefore, it suffices to reduce the area of each light receiving element formed on the CCD image pickup element to increase the density, but in order to maintain the element sensitivity to light and secure a sufficient signal / noise ratio, There is a limit to reducing the area of each light receiving element formed. Therefore, CC
In order to increase the number of effective pixels of the D image pickup device, the external dimensions of the image pickup device must be increased. However, as the surface area of the CCD device increases, the probability of pixel defects in the semiconductor manufacturing process increases, and the yield increases. The rate decreases exponentially.
In the examples so far, the maximum is 200 for HDTV cameras.
A 10,000 pixel CCD image sensor is manufactured.

[0006]

As described above, the conventional C
A video camera system using a CD image pickup device has a very high manufacturing cost due to its low yield rate. Therefore, it has been very difficult to make a video camera system with higher resolution using a defect-free CCD image pickup device in terms of economy and mass productivity.

On the other hand, it is conceivable to improve the image quality of the video camera system by an additional circuit. However, for that purpose, it is necessary to take different setting values and circuit configurations for each CCD image pickup device in accordance with the characteristics of the CCD image pickup device. If such an additional circuit is to be realized by a normal hard logic, the circuit is redesigned for each individual video camera system, which is not economical and is not suitable for mass production. Instead, if the CPU is used to flexibly deal with the stored program, the processing speed may not catch up with the speed of the image data.

It is an object of the present invention to use a defect-free CCD image pickup device in a video camera system having a large number of effective pixels and a high resolution by using a CCD image pickup device having defective pixels which could not be used conventionally. It is an object of the present invention to economically realize performance equivalent to that of a video camera system, and to easily realize a high resolution video camera system that exceeds the current HDTV.

[0009]

In the video camera system according to the present invention, a CCD image pickup device having a defective pixel whose existing position is known is used, and the defective pixel is detected from the signal value of the adjacent pixel. Means are added to estimate and compensate the power signal value.

The means for compensating for the defective pixel is as follows: (1) By inputting an image signal obtained from the CCD image pickup device.
First-in-first-out with one scan line delayed
Obtained from the to-out memory 1 and the CCD image pickup device
Of defective pixels whose location is known from the image signal
Capture signal values for each top, left, and right neighbors
First-in / first-out memory 2 output by
And an image signal obtained from the CCD image sensor and
Output from first-in first-out memory 2
Should be obtained from the defective pixel based on the signal value
The signal value, means for signal value or we estimate the near contact pixel,
From the first-in / first-out memory 1
The output of the defective pixel is estimated by the estimating means
Selector that replaces the signal value of the defective pixel
It consists of a mable logic circuit,
You can also set the position of the pixel whose signal value should be estimated by the estimation means.
Or changing means. Alternatively, (2) the presence position from the image signal obtained from the CCD image sensor
The signal value of the pixel directly above the defective pixel whose position is known.
First-in / first-out to capture and output
A memory and an image signal obtained from the CCD image pickup device.
And from the first-in first-out memory
Obtained from the defective pixel based on the output signal value
Means for estimating power signal value from signal values of adjacent pixels
And the lack of the image signal obtained from the CCD image sensor.
Defects estimated by the means for estimating the output of the defective pixel
A selector for replacing a signal value of a pixel consists of a programmable logic circuit, by programming, and means for setting or changing the position of the pixel to be estimated signal value before Symbol the means for estimating.

[0011]

In a high-definition image, the visual importance of individual pixels among the total pixels is reduced. Therefore, in the video camera system of the present invention, the signal value of the defective pixel is compensated by interpolation or the like, and even if there is a defective pixel in the CCD image pickup device itself, the interpolation is performed from the signal value of the adjacent pixel and it is impossible to determine. By obtaining an image of good quality to some extent, the manufacturing cost is reduced by using a CCD image pickup device having a defective pixel which cannot be used conventionally. Further, with respect to the number and position of defective pixels which differ for each individual CCD image pickup device, a programmable logic circuit is used as means for setting or changing the number and position, and a single hardware is used. Simplify the circuit design and make it suitable for mass production. As a result, performance equivalent to that of a video camera system using a defect-free CCD image sensor can be economically realized, and the problem of low yield that eliminates defects can be solved and higher resolution than before can be realized. And

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention. In the present embodiment, the case where the defective pixel of the CCD image pickup device is estimated and compensated for from a neighboring pixel on the upper, lower, left, and right sides of the defective pixel, is assumed.

First, an interpolation method for estimating a defective pixel in this embodiment will be described. FIG. 3 shows the arrangement of adjacent pixels for estimating the signal value of the defective pixel of the CCD image pickup device in the video camera system of the present invention. Here, in the CCD image pickup device, the column number in the increasing direction from left to right is J, and the direction in which the row number is increasing from top to bottom is I. Then, it is assumed that pixel signal values are sequentially output in the direction in which the column number J increases and the row number I increases in accordance with the driving clock. When the vertical and horizontal positions of the defective pixel in the center of FIG. 3 are (I, J), the estimated value of the defective pixel signal value Y (I, J) is as follows:

[0015]

[Equation 1]

As described above, signal values Y (I-1, J), Y (I, J-1), Y (I, J) of four pixels that are vertically and horizontally close to each other.
+1) and Y (I + 1, J) are averaged.

FIG. 1 is a block diagram of a video camera system for estimating the signal value of a defective pixel based on the interpolation method 1. In FIG. 1, 1 is a CCD image pickup device, 2 is C
CD drive circuit, 3 is a sample hold (SH) circuit, 4
Is an A / D converter, 5 is a column counter, 6 is a row counter, 7 is a pixel position comparison unit, 8 is a timing generation unit, 9,
Reference numerals 10, 11, and 13 are first-in / first-out memories (hereinafter referred to as FIFO), 12 is an average value calculation unit, and 14 is a selector.

In the above structure, the CCD driving circuit 2 generates the pixel data transfer clock CK, the vertical synchronizing signal VS, and the horizontal synchronizing signal HS, and the CCD image pickup device 1 driven by these three lines of signal lines is used. The image signals of the light receiving elements are sequentially output from left to right in the direction of increasing J and further from top to bottom in the direction of increasing I.
In the following description, the number of pixels in the horizontal direction is M. The output of the CCD image pickup device 1 is converted into a digital PCM signal by the sample hold circuit 3 and the A / D converter 4.
The column counter 5 and the row counter 6 have a pixel data transfer clock CK of the CCD drive circuit 2 and a horizontal synchronization signal HS, respectively.
Is counted up by the CCD and the count value
The coordinates J and I of the pixel output by the image sensor 1 are shown.

The pixel position comparison unit 7 detects the position (I,
J), the value of the column counter 5 coincides with J and the value of the row counter 6 coincides with (I-1), that is, the time when the pixel signal immediately above the defective pixel is output from the A / D converter 4. To detect. The timing generator 8 immediately takes in the signal value Y (I-1, J) of the pixel immediately above into the FIFO 9,
Image signal value Y on the left side of the defective pixel after M-1 clocks
(I, J-1) is read into the FIFO 10, and two clocks after that, the image signal value Y (I, J + 1) on the right side is read into the FIFO 11. Further, after M-1 clocks, when the pixel signal value Y (I + 1, J) immediately below is output from the A / D converter 4, the average value calculation unit 12 determines that the four image values for the signal value that the defective pixel should have. The average value of the signal values is calculated, and the selector 14 is switched to output the average value as an estimated value (video output) instead of outputting the defective pixel from the A / D converter 4.

FIFO9 and FIFO10, FIFO
Reference numeral 11 indicates a neighboring pixel signal value of a defective pixel if there is another defective pixel between holding the signal values of the neighboring pixels on the right and left of the defective pixel and then obtaining the average value of the pixel signal values directly under the defective pixel. Is stored and sent to the average value calculation unit 12 sequentially. Further, since the calculation result of the average value is performed after the signal value of the pixel immediately below the defective pixel is A / D converted, the CCD value is higher than the signal value of the defective pixel to be replaced.
It is delayed by the clock corresponding to the number of pixels in the scanning line direction (horizontal direction) of the image sensor 1. The FIFO 13 is for compensating for this delay and for synchronizing the image signal output from the A / D converter 4 and the output of the average value calculator 12.

In the above system configuration, since the position and number of defective pixels are different for each CCD image pickup device, the pixel position comparison unit 7 requires different comparison circuits for each CCD image pickup device. In the present invention,
This comparison circuit is realized by one kind of hardware using a programmable logic element, and is suitable for mass production. In the pixel position comparison unit 7 of this embodiment, the position of the defective pixel to be detected by the comparison circuit and the number thereof are set by programming, that is, by setting the logic block function inside the programmable logic element and the inter-block wiring by an electric program signal sequence. Can be set, and the setting can be changed.

Next, a second embodiment of the present invention will be described.

FIG. 2 is a block diagram showing the structure. The present embodiment is an example in which the signal value of the defective pixel of the CCD image pickup device in FIG. 3 is estimated from two adjacent pixels and compensated. In the present embodiment, the signal value Y (I, J) of the defective pixel is estimated according to the following interpolation method in the arrangement of the defective pixel and the adjacent pixel in FIG. That is, interpolation method 2:

[0024]

[Equation 2]

As described above, the output Y (I-1, J), Y has already been obtained before the output time of the defective pixel.
It is calculated as the average value of the signal values of the two pixels of (I, J-1).

FIG. 2 is a configuration diagram in the case of estimating a defective pixel based on the interpolation method 2. In FIG. 2, 1 is a CCD
Image pickup element 2, CCD driving circuit, 3 sample hold (SH) circuit, 4 A / D converter, 5 column counter, 6 row counter, 7 pixel position comparing section, 8 timing generating section, 9 FIFO, 12 is an average value calculator, 14
Is a selector.

In the above structure, the CCD image pickup device 1, the CCD drive circuit 2, the sample hold circuit 3, A /
The configuration and functions up to the D converter 4, the column counter 5, the row counter 6, and the pixel position comparison unit 7 are the same as in the case of the first embodiment of FIG. In this embodiment, when the pixel position comparison unit 7 detects the timing at which the pixel signal corresponding to the position directly above the defective pixel is output from the A / D converter 4, the timing generation unit 8 immediately outputs the signal value Y of the pixel directly above the defective pixel. (I-1, J) is taken into the FIFO 9. That M
The average value calculation unit 12 calculates the estimated signal value of the defective pixel together with the image signal value Y (I, J−1) on the left of the defective pixel that appears after −1 clock, and switches the selector 14 to switch the estimated signal value. Is output as a substitute for the output of the defective pixel from the A / D converter 4. In this configuration method, the estimated signal value of the defective pixel can be output immediately after the average value is calculated using the signal values of the pixels on the left side.
O13 can be omitted. However, since the number of pixels used for estimation is limited to two pixels on the upper side and on the left side, four pixels in the configuration of FIG.
The estimation accuracy is worse than when using the average value of the individual pieces.

In a high-definition image having an effective number of pixels exceeding that of an HDTV system, the visual importance of individual pixels among the total number of pixels exceeding at least 4 million is reduced. Therefore, in the video camera system of the above-described embodiment, by interpolating the signal value of the defective pixel, even if the CCD image pickup device itself has about 1 to 100 defects, the interpolation is visually performed. It is possible to obtain an image of good quality to the extent that it cannot be discriminated.

In the above embodiment, the adjacent pixels used for the interpolation of the defective pixel are four pixels vertically and horizontally,
The case of two pixels on the top and the left has been described as an example, but the number and position of adjacent pixels are not limited to the above case. Further, as the interpolation method, the average value calculation is shown in the above embodiment, but in general, the linear weight sum, and further other interpolation methods can be applied. As described above, the present invention can be variously applied and various embodiments can be adopted in line with the gist thereof.

[0030]

As described above, according to the video camera system of the present invention, (1) use of an inexpensive CCD image pickup device by allowing the presence of defective pixels, and
A defect-free CCD is solved by solving the problem of low yield that eliminates defects and increasing the number of effective pixels, and (2) estimating and compensating the signal value of a defective pixel from the signal values of neighboring pixels. Compared with a video camera system using an image pickup device, it is possible to obtain a high quality image signal that does not cause visual problems. (3) By using a programmable logic circuit, the position and number of defective pixels of each CCD image pickup device It is possible to deal with the difference of with a single hardware.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, in which a signal value is estimated using four adjacent pixels.

FIG. 2 is a block diagram showing a second embodiment of the present invention, in which a signal value is estimated using two adjacent pixels.

FIG. 3 is a layout diagram of adjacent pixels for estimating a signal value of a defective pixel.

[Description of Reference Signs] 1 ... CCD image pickup device 2 ... CCD drive circuit 3 ... Sample hold circuit 4 ... A / D converter 5 ... Column counter 6 ... Row counter 7 ... Pixel position comparison unit 8 ... Timing generation units 9, 10, 11 , 13 ... First-in first-out memory (FIFO) 12 ... Average value calculator 14 ... Selector

Continuation of front page (56) Reference JP-A-5-64086 (JP, A) JP-A-6-86206 (JP, A) JP-A-63-88971 (JP, A) JP-A-54-124628 (JP , A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 5/228 H04N 5/335

Claims (2)

(57) [Claims] 1. A video camera system using a CCD image pickup device, wherein an image signal obtained from the CCD image pickup device is input to perform one scan.
First-in first-out with delayed line segment output
Memory 1 and the presence position from the image signal obtained from the CCD image sensor
The top, left, and right neighbors of a defective pixel with known
Fast key that captures and outputs signal values for pixels
The first-first-out memory 2, the image signal obtained from the CCD image pickup device, and the frame signal.
Output from the first-in / first-out memory 2
Means for estimating the signal value to be obtained from the defective pixel from the signal value of the adjacent pixel based on the signal value of the defective pixel, and the first-in / first-out memory 1
The output of the defective pixel is estimated by the estimating means
A selector for replacing the signal value of the defective pixel with a programmable logic circuit, and means for setting or changing the position of the pixel whose signal value should be estimated by the estimating means by programming. Video camera system. 2. Video camera system using CCD image sensor
In the stem, The existence position is already known from the image signal obtained from the CCD image sensor.
Capture the signal value of the pixel directly above the known defective pixel
First-in / first-out memory
When, The image signal obtained from the CCD image pickup device and the frame
Output from the first-in / first-out memory
The signal value that should be obtained from the defective pixel based on the signal value
A means for estimating from the signal values of adjacent pixels, The defect image of the image signal obtained from the CCD image sensor
Defective pixel estimated by the means for estimating the output of the element
Selector that replaces the signal value of It consists of programmable logic circuits and
The position of the pixel whose signal value should be estimated by the estimation means
Means to set or change CCD video camera system characterized by having
Mu.