Calibrated color scanner with reference level adjustment

Abstract

A rotary color scanner has both linear and logarithmic mode static and dynamic calibration to quickly and automatically calibrate the scanner before each scan, as well as during a given scan, without operator intervention of any kind, whether in the factory or in the field. Close calibration is achieved, despite the use of photomultiplier detectors which are inherently particularly susceptible to drift, and despite the use of high intensity lamps whose output typically varies greatly with aging. The system establishes operation at an optimized data throughput rate up to a limit determined by the maximum scan rate of the system, and thereafter switches to operation at an optimized signal/noise ratio.