Dual wavelength optical system

Details Dual wavelength optical system Dual wavelength optical system

1982-11-12

1985-03-05

Punter, William H.

Dynamic information storage or retrieval

Information location or remote operator actuated control

Selective addressing of storage medium

350397, 369 44, G02B 530

Patent

active

045027625

ABSTRACT:
In dual wavelength equipment such as a combined read/write unit for an optical disc system, read light of wavelength .lambda..sub.1 is directed through an isolator and a combiner, is reflected from a target back through the combiner and, at the isolator is directed out of the incident beam path to photodetectors. Write light of wavelength .lambda..sub.2 is directed from a position off the read beam path to the combiner where it is re-directed into the read beam path and onto the target. The isolator has a linear polarizer, a polarizing beam splitter, and a retarder functioning together to ensure that at the polarizing beam splitter reflected light is linearly polarized in a direction perpendicular to the incident light. The combiner is typically an interference filter inclined both to the read and write beam path, which transmits .lambda..sub.1 and reflects .lambda..sub.2. Since the filter strongly alters the polarization state of obliquely incident light, a second interference filter located between the polarizing beam splitter and the first filter is used to compensate for the change in polarization state caused by the first filter and by other elements of the optical system.

REFERENCES:
patent: 3463575 (1969-08-01), Gates, Jr.
patent: 4290122 (1981-09-01), Bates et al.
patent: 4332476 (1982-06-01), Stenberg et al.
Smolkin et al., "Light Splitting Device", Soviet Jr. of Optical Technology, vol. 41, 8-1974, pp. 441-444.

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