Imaging device, integrated circuit, and flicker reduction method

1. An image capture device which reduces flicker caused by illumination from an image signal which has the flicker, the device comprising:

an image sensor which captures a subject image and generates the image signal;

an integrated value calculating section which calculates, on a frame-by-frame basis, a value of a line integral of luminance values with respect to each of a plurality of horizontal lines that are included in a frame based on an image signal associated with each of the plurality of horizontal lines;

a memory which stores the values of the line integral of multiple images;

an average calculating section which calculates a line average value by working out the average of the values of the line integral on the same horizontal line between the newest frame in the memory and a number of other frames gotten earlier than the newest one in the memory;

a waveform data generating section which generates waveform data comprised of normalized values by performing normalization processing by dividing each of the values of the line integral stored in the memory by the line average value of the same horizontal line and subtracting one from the quotient; and

a flicker extracting section which extracts information about the phase and frequency of the flicker by detecting, in the multiple frames, a horizontal line location where the waveform data gotten from the waveform data generating section has a value of substantially zero.

2. The image capture device of claim 1 , wherein the flicker extracting section includes a counter which increments its count every time the location is detected, and

the flicker extracting section detects the location at least three times and extracts information about the phase and frequency of the flicker by linear regression by reference to the counter's value and information about the location.

3. The image capture device of claim 2 , wherein the frame includes an image in a valid pixel region and an image in an invalid pixel region in a vertical blanking interval with respect to the image sensor, and

the counter increments its count every time the location is detected in the valid pixel region and in the invalid pixel region.

4. The image capture device of claim 1 , wherein at least one of the number of frames stored in the memory and the number of frames retrieved by the average calculating section from the memory is determined by the frame rate of the image sensor.

5. The image capture device of claim 1 , wherein the flicker extracting section calculates the amplitude of the flicker by multiplying the standard deviation of the normalized value by √{square root over ( )}2.

6. The image capture device of claim 1 , wherein the flicker extracting section performs low-pass filter processing on the waveform data.

7. The image capture device of claim 1 , wherein the flicker extracting section detects the location of a horizontal line, where the value of the waveform data becomes substantially equal to zero, in the multiple frames according to a change in the sign of the normalized value, based on respective normalized values before and after the sign changes.

8. An integrated circuit which reduces flicker caused by illumination from an image signal which is generated by an image sensor and which has the flicker, the circuit being configured to:

calculate, on a frame-by-frame basis, a value of a line integral of luminance values with respect to each of a plurality of horizontal lines that are included in a frame based on an image signal associated with each of the plurality of horizontal lines;

calculate a line average value by working out the average of the values of the line integral on the same horizontal line between the newest frame and a number of other frames gotten earlier than the newest one;

generate waveform data comprised of normalized values by performing normalization processing by dividing each said value of the line integral by the line average value of the same horizontal line and subtracting one from the quotient; and

extract information about the phase and frequency of the flicker by detecting, in the multiple frames, a horizontal line location where the waveform data gotten from the waveform data generating section has a value of substantially zero.

9. The integrated circuit of claim 8 , further comprising a memory,

wherein the memory stores the values of the line integral of multiple frames.

10. A flicker reducing method for reducing flicker caused by illumination from an image signal which is generated by an image sensor and which has the flicker, the method comprising the steps of:

calculating, on a frame-by-frame basis, a value of a line integral of luminance values with respect to each of a plurality of horizontal lines that are included in a frame based on an image signal associated with each of the plurality of horizontal lines;

calculating a line average value by working out the average of the values of the line integral on the same horizontal line between the newest frame and a number of other frames gotten earlier than the newest one;

generating waveform data comprised of normalized values by performing normalization processing by dividing each said value of the line integral by the line average value of the same horizontal line and subtracting one from the quotient; and

extracting information about the phase and frequency of the flicker by detecting, in the multiple frames, a horizontal line location where the waveform data gotten from the waveform data generating section has a value of substantially zero.