Post by plutronus on Sept 3, 2013 21:26:30 GMT -6
Optical Society of America Annual Meeting
Thursday, October 7, 1993, Toronto, Ontario
ThDD64
Thursday, October 7, 1993, Toronto, Ontario
ThDD64
- Steel-Plate Magic Mirror -
K. Frank Lin, Ph.D., MIES
K. Frank Lin, Ph.D., MIES
The so called "light-penetrating mirror" was considered an ingenious achievement in optical and metallurgical techniques in ancient China.[1] The front side of the mirror is a smooth reflecting surface and the rear side is engraved with several Chinese epigraphs. If one faces the mirror to the sunlight and casts the reflected beam on a wall, the pattern on the rear-side will be displayed clearly on the wall. It seems 'magically' that light has penetrated the mirror and carried the
rear-side information out.[2]
A new version of the ancient Chinese "magic mirror" was constructed using a thin piece of 0.5 mm thick [**0.02"...thickness of a rolling paper**] stainless steel plate. One side of the metal plate is a polished mirror surface. A ball-point pen was used to write a few characters on the other side. When laser light is cast on the mirror side, the reflected beam displays the image of the characters on the wall. The pressure of the ball point depressed the rear surface of the plate and changed the microscopic structure of the surface elements. [**now visualizing the inside of the thin metal plate, as though looking inside a sandwich**]...After the pressure was removed, the rear surface elements came to equilibrium state by pulling back the front surface elements and creating a concave track which functions like focusing mirror elements. The Chinese, after accidently dropping a mirror several times on the floor, a few cracks were clearly observed at the wall when casting light on the mirror again. The cracks on the plate are imperceptible with the naked eye. This magic mirror effect has potential applications in metal non-destructive testing.
- Z. M. Zhang, 'International Trends in Optics', Ed., J. W. Goodman. p185 (1991)
- Q. Lin., 'China Reconstructs' (in English), 27. (Feb-March, 1977)
- ** comments by plutronus