Automatic Threshold Adjustment for Mask Reader Using Reflective Type Photoelectric Sensors
Original Publication Date: 1978-Jun-01
Included in the Prior Art Database: 2005-Feb-21
The electrical output of photoelectric sensors varies, depending upon ambient light condition of mask, etc. In this circuit a diode matrix detects the maximum input logical "1" voltage and the minimum logical "0" voltage so that a switching threshold for a photoelectric reader can be automatically adjusted to minimize error. The switching threshold at the logic inputs is adjusted to be halfway between "1" and "0".