JPH0523551B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image defect compensation device that compensates for pixel signals having defects in an image.

[Prior Art] A conventional device of this type is shown on pages 19 to 24 of the Technical Report of the Television Society of Japan, Vol. 7, No. 14, and is shown in FIG. This third
The figure shows an overall circuit block diagram of a conventional device. In the figure, the image defect compensating device is an image defect compensating device of an image sensor, and 1 is an image capturing unit that inputs an object as an image and converts the image into a signal. , 2 is a clamp circuit that holds the signal output from the imaging unit 1, 3 is a multiplication circuit, 4 is an addition circuit, 5 is an inversion circuit, 6 is a delay circuit, 7 is a multiplication circuit, and 8 is a defect compensation signal generation It is a circuit. 3A and 3B indicate input terminals of the multiplication circuit 3, and 7A and 7B indicate input terminals of the multiplication circuit 7.

The operation of the conventional device based on the above configuration will be explained based on the diagrams for explaining the operation shown in FIGS. 3 and 4. The 0 level of the signal output from the imaging section 1 is clamped to the potential E by the clamp circuit 2. This is shown in FIG. FIG. 4 shows the arrangement of filters, where W indicates an all-color transmitting filter and G indicates a green transmitting filter. The signal shown in Figure 4 is
This corresponds to the filter arrangement shown in the figure.
When the signal shown in FIG. 4 is input to the delay circuit 6, the signal shown in FIG. 4 is output. The multiplier circuit 3 operates to output the clamp potential E when the input terminal 3A is at a low level, and outputs the signal from the input terminal 3B when the input terminal 3A is at a high level. The multiplier circuit 7 operates so that the clamp potential E is output when the input terminal 7A is at a low level, and the signal from the input terminal 7B is output when the input terminal 7A is at a high level. Fourth
As shown in the figure, it is assumed that the nth signal is a signal due to a defective pixel. Correspondingly, a defect compensation signal output from the defect compensation signal generation circuit 8 is shown in FIG.

Incidentally, since the inversion of the defect compensation signal shown in FIG. 4 is input by the inversion circuit 5 to the input terminal 3A of the multiplication circuit 3, the output becomes the signal shown in FIG. Since the defect compensation signal shown in FIG. 4 is input to the input terminal 7A of the multiplication circuit 7, the output thereof becomes the signal shown in FIG. When the defect compensation signal is at a low level, the adder circuit 4 outputs the output signal of the clamp circuit 2 shown in FIG. 4, and when the defect compensation signal is at a high level, it outputs the output signal of the delay circuit 6 shown in FIG. As a result of the above operations, the signal from the n-th defective pixel is changed to n- as shown in FIG.
It is replaced with the signal of the second pixel. This image defect compensation device is based on the principle that signals of pixels that are close to each other have approximately the same value due to the correlation of images.

The defect compensation signal generation circuit 8 includes a storage device, stores the position of a defective pixel in advance, and generates a defect compensation signal based on the position of the defective pixel.

[Problems to be Solved by the Invention] Since the conventional image defect compensation device is configured as described above, when the image changes rapidly, the compensation error becomes large depending on the direction of the change. ,
There was a problem that defective pixels could not be effectively compensated for.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to compensate for defective pixel signals with higher accuracy by reducing compensation errors in an image defect compensation device.

[Means for Solving the Problems] The image defect compensation device according to the present invention converts defective image signals vertically and horizontally from pixel signals output from a plurality of image sensors arranged in a square grid. Absolute value calculation means for calculating the absolute value of the difference between two pixel signals sandwiched in the direction and the diagonal direction and outputting an absolute value signal, and two pixel signals that give the smallest value among the absolute value signals. A minimum difference detection means for detecting, an average value calculation means for performing an average value calculation on two pixel signals detected by the minimum difference detection means and outputting an average value signal, and a replacement for replacing a defective pixel signal with an average value signal. means.

[Function] In the image defect compensation device according to the present invention, the absolute value calculation means calculates and obtains the absolute value of the difference between two pixel signals that sandwich the defective pixel signal in the vertical direction, horizontal direction, and diagonal direction. Two pixel signals giving the smallest value among the absolute value signals are detected by the minimum difference detection means. An average value signal for the two pixel signals is calculated by the average value calculation means, and a replacement means replaces the defective pixel signal with the average value signal. The minimum difference detection means detects two pixel signals with the smallest difference in pixel signal level, and the average value thereof is used to replace the defective pixel signal, so that the defective pixel signal can be compensated with high precision. Furthermore, since the diagonal direction of the defective pixel is also taken into consideration, the defective pixel signal can be compensated for with higher accuracy.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. TV to simplify explanation
An example will be described in which a signal representing an image is subjected to image defect compensation by sequentially scanning line by line, such as a signal. In FIG. 1, 9 is a delay circuit, 9a to 9i are output terminals of the delay circuit 1, and 10 is the output terminal 9a to 9d and the output terminal 9.
Subtraction circuit 10 that calculates the difference between each output from f to 9i
Subtraction means constituted by a to 10d; reference numeral 11 denotes an absolute value circuit 1 that takes the absolute value of the value output from each subtraction circuit 10a to 10d of the subtraction means 10;
Absolute value means constituted by 1a to 11d; 12 denotes each absolute value circuit 11a constituting the absolute value means 11;
A comparison circuit 13 compares each value of the output terminals 9a to 9d of the delay circuit 9 and the output terminal 9.
an average value calculation means constituted by average circuits 13a to 13d that calculate the average value of each output of f to 9i;
14 is each average circuit 13a of the average value calculation means 13;
15 is a defect compensation signal generation circuit that outputs a signal to compensate for the defective pixel, 16 is the output of the output terminal 9e of the delay circuit 9, and the output of the comparison circuit 12. A replacement circuit is shown in which the outputs of the selection circuit 14 and the selection circuit 14 are respectively input, and the signal of the defective pixel is replaced by compensating for the signal and outputted. The defect compensation signal generating circuit 15 includes a storage device, stores the position of a defective pixel in advance, and generates a defect compensation signal based on the position of the defective pixel.

Next, the operation of the image defect compensation apparatus according to this embodiment will be explained. FIG. 2A is a diagram showing a part of a pixel array arranged in the horizontal direction (row direction) and vertical direction (column direction). ). In the same figure, m rows,
Let the n-column signals be expressed as S(m, n).
A case will be described in which there is a defect in the signal of a pixel of m rows and n columns. FIGS. 2B, C, D, and E each show a pattern around a defective pixel.

First, in FIG. 1, the delay circuit 9, when the signal S (m, n) is output to the output terminal 9e,
Signal S (m+1, n+1) to output terminal 9a, signal S (m+1, n) to output terminal 9b, signal S (m+1, n-1) to output terminal 9c, signal S to output terminal 9d.
(m, n+1), and the signal S(m, n-
1), signal S (m-1, n+1) to output terminal 9g,
Signal S (m-1, n) to output terminal 9h, output terminal 9
A signal S (m-1, n-1) is output to each terminal i.
Note that this delay circuit 9 can be constructed of, for example, a CCD or LC delay equalizer.

Next, each of the above output terminals 9a to 9d, 9f to 9i
The signal output from each subtraction circuit 10a to 1
0d and the difference is calculated, and the absolute value of each output of each subtraction circuit 10a to 10d is obtained by each absolute value circuit 11a to 11d, and further, the output of each of these absolute value circuits 11a to 11d is sent to a comparison circuit. The signal difference between two pixels is compared as shown below.

The signal difference between the two pixels above is |S(m-1,n)-S(m+1,n)| |S(m,n-1)-S(m,n+1)| |S(m-1,n-1)-S(m+1,n+1)| |S(m-1,n+1)-S(m+1,n-1)| It is.

Furthermore, the average value circuits 13a to 13d, the selection circuit 14, and the replacement circuit 16 calculate |S(m-1,n)
-S(m+1,n)| is the minimum, S(m-1,n)+S(m+1,n)/2 is S(m,n
) instead of |S(m,n-1)-S(m,n+
1) If | is the minimum, then S(m, n-1)+S(m, n+1)/2 is
) instead of |S(m-1,n-1)-S(m+
1, n+1) | is the minimum, use S (m-1, n-1) + S (m+1, n+1)/2 instead of S (m, n), and |S (m-1, n+1)-
When S(m+1,n-1)| is the minimum, S(m-1,n+1)+S(m+1,n-1)/2 is used instead of S(m,n). These four cases correspond to FIG. 2, B, C, D, and E, respectively.
Since the defect compensation signal generation circuit 15 includes a storage device and stores the position of the defective pixel in advance, the replacement circuit 16 is operated as described above only when a signal from the defective pixel appears at the output terminal 1e.

Note that although the above embodiment shows a configuration using a delay circuit, a circuit having the same function can also be configured using a memory.

[Effects of the Invention] As described above, according to the present invention, the minimum value for detecting two pixel signals that give the smallest value among the absolute value signals calculated taking into account the diagonal direction of the defective pixel signal is Since the difference detection means is provided, an image defect compensation device capable of compensating for defective pixel signals with higher precision is obtained.

[Brief explanation of the drawing]

FIG. 1 is an overall circuit block diagram of an image defect compensation device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of the embodiment device shown in FIG. 1, and FIG.
Figure A is a pixel arrangement diagram, Figures 2B, C, D, and E are pixel array diagrams when the pattern around the defective pixel is changed, and Figure 3 is an overall circuit block diagram of a conventional image defect compensation device. , FIG. 4 is a diagram for explaining the operation of a conventional image defect compensation device. In the figure, 9 is a delay circuit, 10 is a subtraction means, 11 is an absolute value means, 12 is a comparison circuit, 13 is an average value calculation means, 14 is a selection circuit, 15 is a defect compensation signal generation circuit, and 16 is a replacement circuit. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. Pixel signals S(m
-1, n-1) to S(m+1, n+1), the image defect compensation device compensates for a defective pixel signal S(m,n) included in S(m+1,n+1), wherein the defective pixel signal is transmitted vertically, horizontally, and diagonally. The absolute value of the difference between the two pixel signals sandwiched between the two pixel signals is calculated, and the absolute value signal |S(m-1,
n)-S(m+1,n)|,|S(m,n-1)-S
(m, n+1) |, |S(m-1,n-1)-S(m+
1,n+1) | and |S(m-1,n+1)-S
(m+1,n-1)|; and 2 which gives the smallest value among the absolute value signals.
minimum difference detection means for detecting one pixel signal; average value calculation means for performing an average value calculation on the two pixel signals detected by the minimum difference detection means and outputting the average value signal; and replacement means for replacing with an average value signal.