Facsimile recorder with compensation of the electrosensitive blank nonlinear applied voltage-burn characteristic

Claim 1

A facsimile recorder comprising: photoscanning means for scanning an image on a reference document and generating an electrical signal which varies with changes in intensity of a light beam reflected from said document; an electrosensitive blank including an upper masking layer for burning away to expose a contrasting lower layer at points where electrical pulses are applied to said upper layer; stylus means for scanning said blank in synchronism with said photoscanning means and for applying electrical pulses to said upper layer to burn dots therein of sizes varying with the magnitude of said applied electrical pulses, said blank having a nonlinear applied electrical pulse dot-size burn characteristic; pulse generator means for generating a train of uniform electrical pulses; and control circuit means connected to said photoscanning means, pulse generator means, and stylus means for modifying said electrical signal over a range of reflected light intensities to compensate for said nonlinear burn characteristic and for mixing said modified electrical signal and said train of pulses to produce a series of amplitude modulated pulses at said stylus for burning dots in said upper layer having sizes which vary linearly with changes in the intensity of said reflected light beam, said control circuit means including modulator means having an input connected to said pulse generator means, and electrical signal sensitive variable impedance means connected to an output of said photoscanning means and to said input of said modulator means for presenting a variable impedance to said input to develop thereat said modified electrical signal having a magnitude which varies with the intensity of said reflected light beam as an inverse of said burn characteristic.