jcwinterton (11/01/82)
Photochromic reversal memories are hardly new. National Cash Register did a lot of work on them about the time I was using an NCR315 working in a bank. That was the early to mid '60s. Maybe someone should ask them what they found out. I gather it had both a speed and permanence problem and was subsequently dropped.... John Winterton.
bill (11/01/82)
Photochromic materials were indeed tested for use as a memory medium and NCR was one of the principal researchers (in the 1960's). The essential drawbacks of these materials for use as computer memories are: insensitivity, fatigue, and fading. A good deal of light (energy) is required to induce a color change, hence insensitivity. The material will fatigue after many writes (the image fades over time). EG&G put a photochromic dye (triarylmethane ?) behind two quartz windows in goggles and used a Xenon flash- lamp to trigger the photochromic reaction. The flashlamp was triggered by the light from a nuclear detonation. These goggles are designed to protect the vision of fly-boys. Bill Lampeter R.I.T. Photographic Science