Automatic exposure single frame imaging systems

Abstract

An automatic exposure imaging system operating on a single frame image capture basis is adapted for single chip CMOS type construction. For reading dataforms, such as two-dimensional bar codes and matrix codes, the system can provide automatic gain control, automatic exposure control, automatic focus sensing and single frame imaging and decoding, with reduced power consumption. A fixed focus distance sensor element array assembly and optical distance sensing enable automatic initiation of exposure when the image is in-focus. Exposure provided by image illuminators is automatically controlled by sensing of the cumulative level of reflected light during the exposure period. Alternatively, exposure time is determined from a look-up table, based upon the level of light reflected during an initial illumination period of fixed duration. Automatic system turn-off or re-reading can be provided, depending upon whether a dataform is successfully decoded. Power use is reduced by terminating the reading of sensor elements upon successful decoding. A complete, light-weight, hand-held reader is described, including provision for transmission of decoded dataform information and a wide range of additional capabilities via plug-in cards. Related methods are also described.