Auto-Synchronous Gain Setting Circuit and Disc Rotation Sensor Removal Technique
Original Publication Date: 1985-Jul-01
Included in the Prior Art Database: 2005-Feb-18
An auto-synchronous gain setting circuit for the front end amplifier of a bar code scanner sets the gain of the amplifier, removing the need for a diagnostic facet locator. The gain setting is more reliable because a high contrast diagnostic bar code label is easier to make and circuitry provides an improved signal-to-noise ratio in the diagnostic bar code return signal, especially in high ambient light. A frequency domain band-pass filter locates the diagnostic bar code data in the video signal, eliminating the need for the home pulse generated by the rotation sensor. Gain setting is done by peak-to-peak signal measurement. The diagnostic bar code label is a special bar code consisting of the following sequence: bar 1, space 1, bar 1, space 1, bar 1, space 4, where the numerals refer to module width.