Method and apparatus for sensor characterization

摘要

The detailed technology relates to optical sensors, and more particularly relates to characterizing local behaviors of a sensor, and using such characterization information in a sensor-based system. In a particular arrangement, output signals produced from each of plural sensing elements in a 2D optical sensor are checked to determine whether they tend to differ from output signals produced by one or more neighboring sensing elements—when combined across plural captured image frames. The results are stored in an associated memory, and can be consulted in determining how image data captured from the sensor should be used. The technology is particularly illustrated in the context of a watermark decoder for a cell phone camera. A variety of other features and arrangements are also detailed.

主权项

1. A method employing an image sensor that is manufactured by a producer, and subsequently incorporated into an end-product employed by a user, the image sensor comprising plural pixels that each produces a pixel value corresponding to an intensity of incident illumination, in which the pixels should produce identical pixel values given identical incident illumination, the method comprising the acts:
processing plural image frames captured by the sensor, when used in said end-product by the user, to dynamically characterize the sensor performance as a background operation, said processing including: identifying a first neighborhood grouping of sensor pixels, the first neighborhood grouping consisting of a first target pixel and a first set of one or more comparison pixels, the first neighborhood grouping being a subset of the sensor pixels, wherein certain sensor pixels are not included within the first neighborhood grouping; comparing an average pixel value of the first target pixel, computed across said plural frames, with an average pixel value of the first set of comparison pixels, computed across said plural frames to determine whether the first target pixel produces output signals that are larger, on average, than output signals from the first set of comparison pixels; identifying a second neighborhood grouping of sensor pixels, the second neighborhood grouping consisting of a second target pixel and a second set of one or more comparison pixels, the second neighborhood grouping being a subset of the sensor pixels, wherein certain sensor pixels are not included within the second neighborhood grouping; comparing an average pixel value of the second target pixel, computed across said plural frames, with an average pixel value of the second set of comparison pixels, computed across said plural frames to determine whether the second target pixel produces output signals that are larger, on average, than output signals from the second set of comparison pixels; the second set of comparison pixels being different than the first set of comparison pixels; storing error data for at least one of the first and second target pixels, based on results of said comparing acts; decoding a steganographically-encoded digital watermark signal from a further frame of captured imagery, said decoding employing the stored error data; wherein the method adapts through use of the end-product, discerning that at least one of said target pixels that outputs pixel values actually outputs biased pixel values, and employs the stored error data to achieve improved watermark decoding results.