Signal preconditioning for touch entry device.

摘要

A touch entry system employing arrays of emitter (X1...XN, Y1...YN) and detector (X1'...XN', Y1'...YN') opto devices located around the periphery of the irradiated field (12) detects intrusion of an opaque element (18) such as a stylus within the field. The detector analog output is converted to a digital signal for input into a microprocessor (80). Digital signals input into the microprocessor (80) can vary due to inconsistencies in conventional opto devices (101, 102, 103). A programmable amplifier (40) responsive to the microprocessor (80) preconditions the analog signals prior to analog to digital conversion to bring all digital signals corresponding to the unblocked emitter beam condition within a normalized range before input into the microprocessor.