Retro-reflective variable-pitch diffraction grating for use in a

Details Retro-reflective variable-pitch diffraction grating for use in a Retro-reflective variable-pitch diffraction grating for use in a

1992-09-16

1993-07-13

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250237G, 359572, 359573, G01D 534

Patent

active

052276252

ABSTRACT:
A rotary actuator data recording disk file is provided with a retro-reflective diffraction grating for use in measuring the angular position of the rotary actuator arm. The diffraction grating has a diffraction pattern whose pitch varies along the length of the diffraction grating. The variation in pitch is arranged such that, as the rotary actuator arm swings about its pivot axis and the diffraction grating moves across an incident light beam and simultaneously rotates with respect to it, the diffracted beam travels back along the incident path. Thus, the source and detector of a laser position measurement system can remain fixed while measuring the position of a rotary actuator arm to which the diffraction grating is affixed. Due to its low mass and low cost, the diffraction grating can be attached to a rotary actuator arm, sealed into a disk file, used to servo-write the disk file, and left in the disk file when shipped, thus obviating the need for a clean room environment in which to perform the servo-write process.

REFERENCES:
patent: 3603690 (1971-09-01), Hard
patent: 4745293 (1988-05-01), Christensen
patent: 4862468 (1989-08-01), Fink
patent: 4991934 (1989-08-01), Hettrick
patent: 5020910 (1991-06-01), Dunn et al.
patent: 5038032 (1991-08-01), Nishimura et al.

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