Apparatus for generating a modulated pulse signal

Abstract

A device for printing an image onto a surface, such as food containers, employs a laser that is scanned across a surface to produce a latent image on a charged photosensitive surface formed on the surface. The surface is moved relative to the laser source while the laser is activated and deactivated according to a pattern of signal pulses from a control circuit. The device thus forms a raster image. To form very fine images, the control circuit must produce pulses with very small steps in duration. The control circuit of the present invention divides a digital value representing a duration of firing of the laser into high and low order bit sequences. The high order bits, representing a value M, are applied to a counter that generates a first pulse M clock cycles long. The low order bits and the first pulse are applied to a delay circuit. The delay circuit generates a delayed version of the first pulse, which is delayed by an amount represented by the low order bits. The first and second pulse signals are logically ORed to produce the control pulse for the laser.