JP3629310B2 - Solid-state imaging device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a solid-state imaging device including a defect correction circuit that corrects a pixel defect of a solid-state imaging device.
[0002]
[Prior art]
Various schemes have been devised for correcting pixel defects in solid-state imaging devices. Japanese Laid-Open Patent Publication No. 63-310280 proposes a method that can cope with a case where the pixel defect length extends over two pixels.
[0003]
Hereinafter, a solid-state imaging device including a conventional defect correction circuit will be described with reference to FIGS. 3 and 4. In FIG. 3, an image pickup signal is output from the image pickup device 1 with a period T and is input to the defect detection circuit 12 to detect a pixel defect having a high signal level (white flaw) and a pixel defect having a low signal level (black flaw). It is. When it is determined that the input of the defect detection circuit 12 is a pixel defect, the defect time detection circuit 13 determines whether the defect is 1 pixel width or 2 pixel width. In addition, the output of the image sensor 1 is delayed by a period T in each of the delay circuits 3, 4, 5, and 6. The output signal of the delay circuit 3 and the output signal of the delay circuit 5 are added at a ratio of 1: 1 by the synthesis circuit 14 and are used for defect correction from the signals one pixel before and one pixel after the output signal of the delay circuit 4 as a reference. Replacement signals are generated. The input signal of the delay circuit 3 and the output signal of the delay circuit 5 are added at a ratio of 1: 2 by the synthesis circuit 15, and defect correction is performed based on the signals before and after two pixels with reference to the output signal of the delay circuit 4. A replacement signal for is created. The output signal of the delay circuit 3 and the output signal of the delay circuit 6 are added at a ratio of 2: 1 by the synthesizing circuit 16, and defect correction is performed from the signals two pixels before and after one pixel on the basis of the output signal of the delay circuit 4. A replacement signal for is created. When the output of the delay circuit 4 is not defective, the switching circuit 17 selects and outputs the output signal of the delay circuit 4. When the output of the delay circuit 4 is defective, the switching circuit 17 is controlled by the defect correction signal output from the defect time detection circuit 13. If the defect is only one pixel, the switching circuit 17 outputs the output signal of the synthesis circuit 14 for one pixel period. When the defect extends over two pixels, the output signal of the synthesis circuit 15 is output at the first pixel, and the output signal of the synthesis circuit 16 is output at the second pixel.
[0004]
The above operation will be described with reference to the timing charts of FIGS. FIG. 4A shows a case where there is only one defective pixel. If an imaging signal is output from the imaging device 1 with a period T and the pixel a4 is a defective pixel, the pixel a4 is replaced with a pixel of (a3 + a5) / 2 by the defect correction signal and output. FIG. 4B shows a case where the defective pixel extends over two pixels. Assuming that the defect of the first pixel is a3, the defect correction signal replaces the pixel of a3 with a pixel of (2 * a2 + a5) / 3, and the defect of the second pixel with a4 is replaced with a pixel of (a2 + 2 * a5) / 3 Is done.
[0005]
[Problems to be solved by the invention]
However, in the fixed imaging device having the above-described conventional defect correction circuit, after detecting a defective pixel, it is necessary to make a correction by determining whether the length of the defective pixel is one pixel or two pixels. In the case of performing mixed readout of n pixels (n ≧ 2 natural number) in the horizontal direction with a solid-state imaging device, the length of the defective pixel is always n pixels or more, and as n increases, the defective pixel has no defect. As a result, the defective pixels are averaged with the peripheral pixels, which makes it difficult to detect the defects.
[0006]
The present invention solves such a conventional problem, and the position of the defective pixel is obtained even when the mixed reading of n pixels in the horizontal direction is performed by the solid-state imaging device from the defective pixel position information of normal one-pixel reading. Solid-state imaging device having a defect correction circuit that can reliably correct a defective pixel by replacing a pixel mixed with the signal component of the defective pixel with a signal having no signal component of the defective pixel The purpose is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an imaging apparatus of the present invention includes a solid-state imaging device that performs horizontal readout in units of one pixel and readout in units of two pixels, and a first that delays an output signal from the solid-state imaging device. A delay circuit; a second delay circuit that delays an output signal from the first delay circuit; a third delay circuit that delays an output signal from the second delay circuit; and the third delay circuit. A fourth delay circuit that delays an output signal from the first delay circuit, a first switching circuit that switches an output signal from the solid-state imaging device and an output signal from the first delay circuit, and the third delay circuit. A second switching circuit that switches between the output signal from the first delay circuit and the output signal from the fourth delay circuit, and an arbitrary ratio between the output signal from the first switching circuit and the output signal from the second switching circuit. And a synthesis circuit for synthesizing with the second A third switching circuit for switching an output signal from the delay circuit and an output signal from the synthesis circuit; and a defect correction signal when the output signal from the second delay circuit is defective. And when the solid-state imaging device performs readout in units of pixels in the horizontal direction, the output signal from the first delay circuit is selected by the first switching circuit, When the output signal from the third delay circuit is selected by the second switching circuit and the solid-state imaging device reads out in units of two pixels in the horizontal direction, the solid-state imaging device is used by the first switching circuit. When the output signal from the fourth delay circuit is selected by the second switching circuit and the defect correction control circuit outputs a defect correction signal, the third switching circuit is selected. From the synthesis circuit It is characterized in selecting the force signal.
[0009]
[Action]
Therefore, according to the present invention, when performing horizontal readout of n pixels in the image sensor, the position information of the pixels mixed with the defective pixels is determined from the defective pixel position information of normal one-pixel readout, and the defect is detected. By replacing the pixel including the signal component of the pixel with a defect correction signal generated after n pixels and after n pixels, the defective pixel can be reliably corrected.
[0010]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a solid-state imaging device according to an embodiment of the present invention. In FIG. 1, 1 is an image sensor that outputs an imaging signal at a period T, 2 is a defect correction circuit that corrects a pixel defect of the image sensor, 3, 4, 5, and 6 are delay circuits that delay the imaging signal by a period T, 7 , 8 and 10 are first, second and third switching circuits for outputting any one of the signal inputs, 9 is an adder as a composition, and 11 is a defect correction signal in accordance with a pixel defect of the image sensor. Is a defect correction control circuit that outputs.
[0011]
Hereinafter, in the embodiment, the operation of the defect correction circuit 2 when the image pickup device 1 performs reading in a normal pixel unit will be described. In FIG. 1, an image pickup signal is output from the image pickup device 1 with a period T and is input to the defect correction circuit 2. In the defect correction circuit 2, the imaging signals are delayed by the period T in the delay circuits 3, 4, 5, and 6, respectively. The first switching circuit 7 outputs the output signal of the delay circuit 3, and the second switching circuit 8 outputs the output signal of the delay circuit 5. The output signals of the first and second switching circuits 7 and 8 are input to the adder 9 and added, and the defect correction replacement is performed from the signal before and after one pixel on the basis of the output signal of the delay circuit 4. A signal is created. The presence or absence of a defect in the output of the delay circuit 4 is set in advance in the defect correction control circuit 11. If there is no defect, the output of the delay circuit 4 is output by the third switching circuit 10 under the control of the defect correction control circuit 11. Select and output the signal. If the output of the delay circuit 4 is defective, a defect correction signal is output from the defect correction control circuit 11 to the switching circuit 10, and the third switching circuit 10 outputs an output signal of the adder 9, that is, a defect correction replacement signal. The pixel defect of the image sensor 1 is corrected by selecting and outputting.
[0012]
Explaining the above operation, as shown in FIG. 2A, when the imaging signal is output from the imaging device 1 with a period T and the pixel b4 is a defective pixel, the pixel b4 is ( b3 + b5) / 2 pixels are substituted and output.
[0013]
Next, the operation of the defect correction circuit 2 when the image sensor 1 performs the two-pixel mixed readout in the horizontal direction will be described. In FIG. 1, an image pickup signal is output from the image pickup device 1 with a period T and is input to the defect correction circuit 2. In the defect correction circuit 2, the imaging signals are delayed by the period T in the delay circuits 3, 4, 5, and 6, respectively. The first switching circuit 7 outputs the input signal of the defect correction circuit 2, and the second switching circuit 8 outputs the output signal of the delay circuit 6. The output signals of the first and second switching circuits 7 and 8 are input to the adder 9 and added, and the defect correction replacement is performed from the signals before and after two pixels with reference to the output signal of the delay circuit 4. A signal is created. The presence / absence of a defect in the output of the delay circuit 4 is obtained from defective pixel position information of normal one-pixel readout. If there is no defect in the output of the delay circuit 4, the third switching circuit 10 outputs the output signal of the delay circuit 4 Select to output. When the output of the delay circuit 4 is defective, a defect correction signal is output from the defect correction control circuit 11 to the switching circuit 10, and the switching circuit 10 selects an output signal of the adder 9, that is, a replacement signal for defect correction. By outputting, the pixel defect of the image sensor 1 is corrected.
[0014]
The above operation is illustrated in FIGS. 2B and 2C. Since the defective pixel b4 is mixed and read out in the horizontal direction in the image pickup device 1, the defective pixel b4 is mixed with the pixel b3 like the image pickup device output in FIG. 5B, and the image pickup device output in FIG. As described above, two kinds of outputs when mixed with the pixel b5 are conceivable. The horizontal position of the defective pixel in normal pixel-by-pixel readout is detected in advance, and when the image sensor 1 performs mixed readout of two pixels, it is determined in advance which pixels are mixed in the horizontal direction. Therefore, it can be easily obtained. As an example, when a pixel whose horizontal position is “1” and a pixel whose horizontal position is “2” are mixed, the pixel whose horizontal position is “m” is the pixel one pixel before when m / 2 is too zero. If too much is 1, it is mixed with the pixel after one pixel. In this way, it can be determined whether the defective pixel is mixed with the preceding or subsequent pixel at the time of the mixed reading of the two pixels. As a result, in the case of FIG. 5B, the defective pixel b4 is mixed with the previous pixel b3, and the pixel b3 is changed to the pixel (b1 + b2) / 2 + (b5 + b6) / 2 by the defect correction signal corresponding thereto. The pixel of b4 is also replaced with the pixel of (b1 + b2) / 2 + (b5 + b6) / 2 and output. Since b1 and b2 and b5 and the pixels of b6 are premixed by incorporating two pixels before and after the two pixels including the defective pixel by 1/2, I and be b3 and b4 is substituted by the same signal The In the case of FIG. 6C, the defective pixel b4 is mixed with the pixel b5 after one pixel, and the pixel of b4 is replaced with the pixel of (b2 + b3) / 2 + (b6 + b7) / 2 by the defect correction signal corresponding thereto. , B5 are also replaced with (b2 + b3) / 2 + (b6 + b7) / 2 pixels and output. Since the pixels b2 and b3 and b6 and b7 are premixed by incorporating two pixels before and after the two pixels including the defective pixel by 1/2, I and it b4 and b5 is substituted by the same signal The
[0015]
Similarly, when the image pickup device 1 performs the n-pixel mixed readout in the horizontal direction, the defective pixel is obtained by obtaining the excess of m / n from the horizontal position m of the normal read-out defective pixel in units of one pixel. Is calculated by the number of pixels before and after the pixel, and a replacement signal for defect correction is generated from the signals before and after n pixels, and the output signal of the defect correction control circuit 11 corresponds to the mixed pixel. Thus, by replacing defective pixels mixed as n pixel widths, it is possible to correct pixel defects corresponding to mixed reading of n pixels.
[0016]
In this way, in the image pickup apparatus 1 that performs mixed read in the horizontal direction by the image pickup device, when normal one-pixel unit reading is performed, defect correction is performed from one pixel before and after one defective pixel as in the conventional case. When creating a replacement signal for n pixels and performing a mixed readout of n pixels, a defective signal and a pixel mixed with the defective pixel are created before and after each n pixels, and a defect correction replacement signal is created. A complete correction can be performed by replacing the defective pixel mixed with an n pixel width in the direction in which the defective pixels are mixed in the defect correction signal.
[0017]
【The invention's effect】
As is clear from the above embodiments, the present invention creates a replacement signal for defect correction before and after n pixels of a defective pixel when mixed readout of n pixels in the horizontal direction is performed in a solid-state imaging device. By replacing the defective pixel and the pixel mixed with the defective pixel, there is an advantage that the defective pixel can be reliably corrected.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a solid-state imaging device according to an embodiment of the present invention. FIG. 2 is a timing diagram illustrating an operation of the solid-state imaging device according to an embodiment of the present invention. FIG. 4 is a timing diagram showing the operation of a conventional solid-state imaging device.
DESCRIPTION OF SYMBOLS 1 Image pick-up device 2 Defect correction circuit 3, 4, 5, 6 Delay circuit 7 1st switching circuit 8 2nd switching circuit 9 Adder (synthesis | combination circuit)
10 Third switching circuit 11 Defect correction control circuit

Claims (1)

A solid-state imaging device that performs horizontal readout in units of one pixel and readout in units of two pixels, a first delay circuit that delays an output signal from the solid-state imaging device, and an output signal from the first delay circuit A second delay circuit that delays; a third delay circuit that delays an output signal from the second delay circuit; a fourth delay circuit that delays an output signal from the third delay circuit; A first switching circuit that switches between an output signal from the solid-state imaging device and an output signal from the first delay circuit; an output signal from the third delay circuit; and an output signal from the fourth delay circuit; A second switching circuit that switches between the output signal from the first switching circuit and the output signal from the second switching circuit at an arbitrary ratio, and from the second delay circuit Output signal and output from the synthesis circuit Includes a third switching circuit for switching a signal, and a defect correction control circuit for outputting a defect correction signal when there is a defect in the output signal from said second delay circuit to the third switching circuit,
When the solid-state imaging device reads out in units of pixels in the horizontal direction, the first switching circuit selects an output signal from the first delay circuit, and the second switching circuit selects the third switching circuit. Select the output signal from the delay circuit,
When the solid-state imaging device reads out in units of two pixels in the horizontal direction, the first switching circuit selects an output signal from the solid-state imaging device, and the second switching circuit selects the fourth delay circuit. Select the output signal from
When the defect correction control circuit outputs a defect correction signal, an output signal from the synthesis circuit is selected by the third switching circuit.

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