| 摘要 |
An optical reader includes targeting illuminators (e.g., LEDs) which generate a predetermined illumination pattern upon a target. The optical reader captures an image of the target and processes the captured image to determine whether the target is off-pitch or skewed, by analyzing the appearance and characteristics of the predetermined illumination pattern. The illumination pattern may consist of two identical triangles adjacently located but slightly separated so as to cause the pattern to be symmetrical when the target is at perfect alignment, but having shifting characteristics when the target is off-pitch or skewed. The optical reader may use the knowledge of pitch and skew to adjust the captured image. Triggerless operation of the optical reader is provided by placing the optical reader in a cradle and stand having a base with a known target printed on or affixed thereto, within the viewpath of the optical reader. So long as the known target is in the view of the optical reader, it remains in a standby mode, and leaves the standby mode and begins reading when a target is interposed or the optical reader is removed from the cradle. Automatic gain control circuitry is provided having a gain control level which is continuously adjusted when the optical reader is in a standby mode. When the optical reader leaves the standby mode and begins reading, the gain level is pre-adjusted, resulting in a faster read of good data.
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