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Comprehensive fixed pattern noise cancellation

  • US 10,341,593 B2
  • Filed: 03/15/2014
  • Issued: 07/02/2019
  • Est. Priority Date: 03/15/2013
  • Status: Active Grant
First Claim
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1. A digital imaging method for use with an endoscope in ambient light deficient environments comprising:

  • actuating an emitter to emit a plurality of pulses of electromagnetic radiation, wherein each pulse comprises an individual wavelength of electromagnetic radiation to cause illumination within the light deficient environment;

    pulsing the emitter at a predetermined interval corresponding to a sensing interval of a pixel array;

    sensing reflected electromagnetic radiation from a pulse with the pixel array to create an image frame in a plurality of cycles, the cycles including an integration time of the pixel array that is controlled using an electronic shutter, wherein a duration of the integration time is variable from cycle to cycle in the plurality of cycles between a readout of a first frame in a first cycle and a readout of a next subsequent frame in a second subsequent cycle and wherein the electromagnetic radiation pulse width and duration are variable during each cycle to adjust a level of light intensity caused by each pulse in the cycle, wherein variation of the integration time is related to the variation in the pulse width and the duration of the electromagnetic radiation pulse;

    wherein the pixel array is actuated at the sensing interval that corresponds to the pulse interval of the emitter;

    stopping the emitter from pulsing for a single iteration;

    creating a dark frame by sensing the pixel array while the emitter is not pulsing a pulse of electromagnetic radiation;

    creating one or more reference frames, based on pixel values in both the dark frame and in a plurality of previous dark frames, for use in removing fixed pattern noise;

    removing fixed pattern noise from the image frame by subtracting stored reference data in the one or more reference frames from the image frame; and

    creating a stream of images by combining a plurality of image frames to form a video stream.

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