US Patent 10068120 High dynamic range fingerprint sensing

Improving fingerprint image measurement despite damage to the stratum corneum. Determining whether a fingerprint image is adequate for matching with a database. If not, re-measure those image portions that are inadequate (overexposed or underexposed), such re-measuring a minimal selection of image portions. An amount of time or power to re-measure is minimized. Improving fingerprint image data collection despite fixed pattern noise like saturated bars in blocks of picture elements. Determining a histogram of grayscale values, removing fixed pattern noise, and expanding real histogram values to obtain more bits of precision.