Underpulsed scanner with variable scan speed, p. w. m. color balance,

Abstract

Scan exposure in a row or swath scanner is controlled by pulsing light sources with pulses that are separated by dark intervals from each other--and from the detector readout periods. Detector sequencing is thereby made independent of the velocity of the pixel-line advance mechanism. Different pulse widths for different colors provide color correction without calculation, or regularize color-space conversion calculations where needed. In a swath scanner, known technology of printing modes is imported into the scanning context. Order of pixel columns within each swath is reversed for printing--permitting use of novel configurations such as a dual-parallel-flatbed copier in which a single common scan-and-advance mechanism simultaneously transports the scan sensor and printheads. To produce mirror images, this configuration is also used without column reversal. In addition to red, green and blue light sources, an infrared source is used for reading invisible indicia that identify forms or media types. The scan sensor is also used for auxiliary printing functions.