Optical scanner with automatic activation

Claim 1

An optical scanner for scanning a bar code, the scanner comprising: an optical scanning head having an LED light source, an optical assembly, and a detector, said detector generating a signal representative of modulated light reflected from a surface within a field of view of the scanner; a power supply; a decoder having a preliminary testing portion and a decoding algorithm portion for receiving and processing said signal; a timing controller for controlling application of power from said power supply to said optical scanning head and said decoder, said timing controller providing a scan command during an inactive mode of the scanner so that power is periodically provided to said optical scanning head to scan said surface within the field of view and to said preliminary testing portion of said decoder to conduct comparisons of said signal to a threshold, the threshold being a minimum number of transitions indicative of said bar code, so that when said minimum number of transitions is found, said scanner enters an active mode for processing said signal within said decoding algorithm portion of said decoder to generate a decoded output, and so that when said minimum number of transitions is not found, said scanner remains in said active mode; wherein said scan command comprises a test sequence of distinct scan periods, each scan period having a different scan duration from other scan periods of said test sequence, said test sequence terminating when a good exposure is achieved.