Method for mismatch detection between the frequency of illumination source and the duration of optical integration time for imager with rolling shutter
First Claim
1. A method for achieving flickerless operation of imagers using a rolling shutter comprising the steps of:
- first detecting flicker in an image frame caused by an illumination source having a non-zero light intensity period; and
adjusting an integration time such that said integration time is an integer multiple of said non-zero light intensity period.
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Accused Products
Abstract
A method for achieving flickerless operation of imagers using a rolling shutter, including the steps of detecting flicker in an image frame and adjusting an integration time such that the integration time is an integer multiple of a light intensity period, is described. The method reduces the task of detecting flicker to detecting a spatial sine wave in the image frame by subtracting two image frames from each other. The subtraction reduces or eliminates image content from the image frames and makes the detection process independent of image content. This method can be practiced based on a very short sequence of image frames (as few as two image frames) and is virtually insusceptible to motion of the image content. Adjustments to the integration time are made by changing the horizontal blanking time of the imager and, thereby extending the duration time of each row of said image frame.
62 Citations
72 Claims
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1. A method for achieving flickerless operation of imagers using a rolling shutter comprising the steps of:
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first detecting flicker in an image frame caused by an illumination source having a non-zero light intensity period; and
adjusting an integration time such that said integration time is an integer multiple of said non-zero light intensity period. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. An image processor for achieving flickerless operation of images comprising:
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a CMOS imager using a rolling shutter; and
a flicker avoidance circuit, wherein said flicker avoidance circuit performs the following functions;
first detecting flicker in an image frame caused by an illumination source having a non-zero light intensity period; and
adjusting an integration time such that said integration time is an integer multiple of said non-zero light intensity period. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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37. A computer system comprising:
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a processor;
a memory device coupled to said processor; and
an image device coupled to said processor, said image device further comprising;
a image processor using a rolling shutter; and
a flicker avoidance circuit, wherein said flicker avoidance circuit performs the following functions;
first detecting flicker in an image frame caused by an illumination source having a non-zero light intensity period; and
adjusting an integration time such that said integration time is an integer multiple of said non-zero light intensity period. - View Dependent Claims (38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54)
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55. A computer system comprising:
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a CPU;
a bus;
a memory device coupled to said CPU via said bus;
a peripheral bus;
at least one input/output device, said at least one input/output device coupled to said CPU via said peripheral bus, said input/output device being a digital camera system;
said digital camera system further comprising an image processor;
said a image processor using a rolling shutter; and
a flicker avoidance circuit, wherein said flicker avoidance circuit performs the following functions;
first detecting flicker in an image frame caused by an illumination source having a non-zero light intensity period; and
adjusting an integration time such that said integration time is an integer multiple of said non-zero light intensity period. - View Dependent Claims (56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72)
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Specification