High-Speed Facsimile Recording with Laser Light Sources

This paper describes improvements in facsimile receivers for newspaper transmission made by replacing conventional crater tube light sources with He-Ne laser lights. This replacement allows the system to operate at wider frequency bandwidth and provides stronger writing light intensity and longer system durability. The light intensity of the writing source is modulated by a Teglass acoustooptic modulator developed at the present laboratory and is operated under Raman-Nath mode of diffraction. Instabilities in the system have been corrected by a feedback loop using one of the two first-order diffracted lights as an intensity watcher. Experiments show that a filmed image with a transmission density of 3.9 and density rising time of 1μs can be obtained by using an acoustooptic modulator operated at a driving frequency of 40 MHz, an RF power of 300 mW, and an incident light beam diameter of 1 mm.