Method of reducing flicker noises of X-Y address type solid-state image pickup device

1. A method of reducing flicker noises attributable to the emission frequency of illumination light generated in an X-Y address type image pickup device having a plurality of pixels for performing photoelectric conversion of incident light in a predetermined signal storage time and outputting image data, the method comprising the steps of:

providing two average luminance detection areas in each frame and calculating average luminance of the image data in the two average luminance detecting areas of a plurality of frames;

performing a sum-of-product calculating process on the plurality of values of average luminance to calculate a sum of products; and

changing the signal storage time based on the sum of products;

wherein sum-of-product coefficients used in the sum-of-product calculating process are determined such that each group of coefficients total at 0 (zero) for both of sine terms and cosine terms.

2. A method of reducing flicker noises in an X-Y address type solid-state image pickup device according to claim 1 , wherein one horizontal selection line is allocated as each of the two average luminance detection areas.

3. A method of reducing flicker noises in an X-Y address type solid-state image pickup device according to claim 1 , wherein the alteration of the signal storage time based on the difference in luminance or sum-of-product calculation value is carried out at least when the power supply of the X-Y address type solid-state image pickup device is turned on.

4. A method of reducing flicker noises attributable to the emission frequency of illumination light generated in an X-Y address type image pickup device having a plurality of pixels for performing photoelectric conversion of incident light in a predetermined signal storage time and outputting image data, the method comprising the steps of:

providing two average luminance detection areas in each frame and calculating average luminance of the image data in the tow average luminance detecting areas of a plurality of frames;

performing a sum-of-product calculating process on the plurality of values of average luminance to calculate a sum of products; and

changing the signal storage time based on the sum of products;

wherein one horizontal selection line is allocated as each of the two average luminance detection areas; and

wherein the interval between the two average luminance detection areas is set as V×(½−(remainder of A/B))/(A/B) where A represents the emission frequency (Hz); B represents the frame frequency (Hz) of the X-Y address type solid-state image pickup device; and V represents the total number of horizontal selection lines.

5. A method of reducing flicker noises in an X-Y address type solid-state image pickup device according to claim 4 , wherein the interval between the two average luminance detection areas is set at 1/20 times the total number V of horizontal selection lines where A=100 Hz and B=30 Hz.

6. A method of reducing flicker noises in an X-Y address type solid-state image pickup device according to claim 1 , comprising the steps of:

presetting a first signal storage time which allows reduction of flicker noises under illumination light having a first emission frequency; and

changing the signal storage time to a second signal storage time which allows reduction of flicker noises under illumination light having a second emission frequency when the difference in luminance or sum-of-product calculation value exceeds a predetermined threshold value.

7. A method of reducing flicker noises generated due to a first emission frequency or a second emission frequency of illumination light in an X-Y address type solid-state image pickup device having a plurality of pixels for photo-electrically converting incident light in a predetermined signal accumulation time to output the photo-electrically converting incident light as image data, the method comprising:

providing two average luminance detecting regions in one frame and calculating an average luminance of the image data in the two average luminance detecting regions in a plurality of frames thereof during the signal accumulation time that is set to be an integral multiple of the first emission frequency;

performing a sum-of-product calculation process on the plurality of average luminance to obtain a calculated sum of products;

determining which of the first emission frequency and the second emission frequency the illumination light has from the calculated sum of products; and

changing the signal accumulation time to an integral multiple of the second emission frequency when the frequency is determined as the second emission frequency;

wherein sum-of-product coefficients used in the sum-of-product calculation process are determined such that each group of coefficients total at 0 for both of sine terms and cosine terms.

8. A method of detecting flicker noises generated due to a second emission frequency of illumination light having first and second emission frequencies in an X-Y address type solid-state image pickup device having a plurality of pixels for photo-electrically converting incident light in a predetermined signal accumulation time to output the photo-electrically converting incident light as image data, the method comprising:

providing two average luminance detecting regions in one frame and calculating an average luminance of the image data in the two average luminance detecting regions in a plurality of frames thereof during the signal accumulation time that is set to be an integral multiple of the first emission frequency;

performing a sum-of-product calculation process on the plurality of average luminance to obtain a calculated sum of products; and

detecting the occurrence of the flicker noises attributable to the second emission frequency when the calculated sum of products is not 0;

wherein sum-of-product coefficients used in the sum-of-product calculation process are determined such that each group of coefficients total at 0 for both of sine terms and cosine terms.

9. An X-Y address type solid-state image pickup device having a plurality of pixels for photo-electrically converting incident light in a predetermined signal accumulation time to output the photo-electrically converting incident light as image data, the device comprising:

an average luminance calculation section providing two average luminance detecting regions in one frame and calculating an average luminance of the image data in the two average luminance detecting regions in a plurality of frames thereof during the signal accumulation time that is set to be an integral multiple of a first emission frequency;

a sum-of-products calculation section performing a sum-of-product calculation process on the plurality of average luminance to obtain a calculated sum of products;

a frequency determination section determining which of the first emission frequency and a second emission frequency the illumination light has from the calculated sum of products; and

a signal accumulation time changing section changing the signal accumulation time to an integral multiple of the second emission frequency when the frequency determination means determines that the frequency the second emission frequency;

wherein sum-of-product coefficients used in the sum-of-product calculation process are determined such that each group of coefficients total at 0 for both of sine terms and cosine terms.

10. An X-Y address type solid-state image pickup device having a plurality of pixels for photo-electrically converting incident light in a predetermined signal accumulation time to output the photo-electrically converting incident light as image data, the device comprising:

an average luminance calculation section providing two average luminance detecting regions in one frame and calculating an average luminance of the image data in the two average luminance detecting regions in a plurality of frames thereof during the signal accumulation time that is set to be an integral multiple of a first emission frequency;

a sum-of-product calculation section performing a sum-of-product calculation process on the plurality of average luminance to obtain a calculated sum of products; and

a flicker noise detection section detecting the occurrence of flicker noises attributable to a second emission frequency when the calculated sum of products is not 0;

wherein sum-of-product coefficients used in the sum-of-product calculation process are determined such that each group of coefficients total at 0 for both of sine terms and cosine terms.

11. A method of reducing flicker noises attributable to the emission frequency of illumination light generated in an X-Y address type image pickup device having a plurality of pixels for performing photoelectric conversion of incident light in a predetermined signal storage time and outputting image data, the method comprising:

calculating an average luminance of the image data in a plurality of average luminance detecting areas of at least one frame; and

adjusting the signal storage time according to a sum-of-product calculation performed on the average luminance values;

wherein the sum-of-product calculation includes sine term coefficients having a sum of 0, and cosine term coefficients having a sum of 0.