Abstract: A mirror driven by a resonant mechanical oscillator is used to scan a modulated laser beam across a rotating dielectric drum. The incident laser beam line scans the drum to form a charge image thereon which is toned as the drum rotates through a toner bath. The toned image is then transferred to paper by rolling contact. The laser beam scan velocity across the drum varies sinusoidally because of the resonant nature of the drive system. The data flow which modulates the laser beam is rate-controlled by a variable clock to accommodate the periodic variations in scanning velocity. The modulation rate -- the data flow rate -- is varied periodically to match the periodically varying scan rate to produce a uniform image element density or spacing across the scan lines of the dielectric surface. The variable clock is also applied to the laser beam modulator to compensate for the periodic variations in the charge density of the image caused by the nonlinear scan velocity.

Abstract: A mirror driven by a resonant mechanical oscillator is used to scan a laser beam across a document. The incident laser beam line scans the record and is absorbed or reflected depending upon the presence or absence of an image on the record. The reflected intensity modulated light is detected by photomultiplier tubes which provide a video analog signal. An A/D device digitizes the analog signal forming a DATA OUT signal. The laser beam scan velocity across the document varies sinusoidally because of the resonant nature of the drive system. The data flow, or bit density of DATA OUT, has a corresponding sinusoidal variation. A write rate controller provides a variable clock which accompanies the DATA OUT. The variable clock has a periodic variation which matches the scan velocity. The rate of the variable clock matches the bit density of DATA OUT causing DATA OUT to be entered into a data bank properly notwithstanding its nonuniform bit density.