Optical encoder with varying grating pitch

Details Optical encoder with varying grating pitch Optical encoder with varying grating pitch

1989-07-03

1990-09-11

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

25023118, H01J 314, G01D 534

Patent

active

049565532

ABSTRACT:
An optical encoder includes a light source for emitting coherent parallel light and a scale having a grating track for defracting parallel light emitted from the light source. The grating track of the scale includes a plurality of linear adjacent gratings extending in a lengthwise direction. Each of the gratings extends in a widthwise direction direction to define a pitch of the grating. Each grating includes a non-transmitting portion and an adjacent transmitting portion extending in lengthwise direction. The aperture ratio defined by the ratio between a width of the transmitting portion and the pitch of each grating is substantially constant for each of the gratings along the grating track. However, the pitch of each of the gratings of the grating track varies along the grating track. A light spot positioning detector is provided for receiving positive and negative defracted light beams of a same order defracted from a grating track for determining a position of the scale.

REFERENCES:
patent: 3166624 (1965-01-01), Vargady
patent: 3985448 (1976-10-01), Wiklund et al.
patent: 4011435 (1977-03-01), Phelps et al.
patent: 4443108 (1984-04-01), Webster
patent: 4528448 (1985-07-01), Doggett
patent: 4631416 (1986-12-01), Trutna, Jr.
patent: 4778273 (1988-10-01), Michel
patent: 4823001 (1989-04-01), Kobayashi et al.

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