Abstract

The early work of recording computer output on microfilm was done with the cathode ray tube as the image forming device. A system capable of writing in vacuo directly on film with a focused electron beam was developed by the 3M Company for use with their Dry Silver Film, which required only heat to develop the latent image. The Electron Beam Recorder was designed to write on 16-mm film, but to produce the standard microfiche additional equipment is required to transfer the data by contact printing onto 105-mm material. Sometime saved through the dry process is lost again during this step of duplication. By extending the spectral sensitivity of Dry Silver Film into the red region, the film became suitable for exposure with the light of a low-cost He-Ne laser. The system to be designed would allow direct recording on 105-mm film. Performance criteria established with the EBR system governed the specification of the LBR. The properties of the laser and the possible method of scanning the beam dictated the design of a special optical system. The telecentric lens system forms a combined image of computer-generated alpha numeric symbols and static form data from a transparency slide on the microfilm; 48× or 25× reduction is selected by the simple movement of one optical element. Through a combination of acoustooptic and electromechanical deflection of the laser beam, characters are formed at the rate of 25,000/sec within a 5 × 7 dot matrix. To ensure reproducibility through four generations of copy the system is capable of resolving 154 lines/mm at 48× reduction on developed Dry Silver Film. Forms may be superimposed in registration with the symbolic data at the rate of 4 frames/sec. A comparison between Xe flash and incandescent illumination of the form slide leaves the tungsten halogen lamp as the preferred light source.

© 1976 Optical Society of America