| 摘要 |
An automatic exposure imaging system (Fig. 2) 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 (60), automatic exposure control (64), automatic focus sensing (62) and single frame imaging and decoding, with reduced power consumption. A fixed focus distance sensor element array assembly (21b) and optical distance sensing enable automatic initiation of exposure when the image is in-focus (Fig. 4). Exposure provided by image illuminators (50, 54) is automatically controlled by sensing of the cumulative level of reflected light during the exposure period (Fig. 6). Alternatively, exposure time is determined from a look-up table (82a), based upon the level of light reflected during an initial illumination period of fixed duration (Fig. 7). Automatic system turn-off or re-reading can be provided, depending upon whether a dataform is successfully decoded (Fig. 6 and 7). Power use is reduced by terminating the reading of sensor elements upon successful decoding. A complete, light-weight, hand-held reader (10) is described, including provison for transmission of decoded dataform information and a wide range of additional capabilities via plug-in cards (34, 36). Related methods are also described.
|
