Adjustment of LED Current in Optical Document Sensor
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
In an optical document sensing unit such as for the bill recognition unit in the banking terminal comprising a light-emitting diode (LED) and photo sensor, the lowering of efficiency due to dust built up thereon and the dispersion of amplification factors for the sensor are compensated by adjusting the LED current to produce a predetermined intensity of radiation of the LED, enabling the sensor to positively sense the document passing through the sensing unit. The main processor 1 sets a value in the 6-bit data latch 2 defining an optimum LED current and, then, the data latch 2 produces C code indicative of the value. On the other hand, the crystal oscillator 3 advances the 8-bit free running counter 4 to generate the 8-bit A code which periodically indicates the values of 0 to 255.