Opto-electronic scale reading apparatus having light-transmissiv

Details Opto-electronic scale reading apparatus having light-transmissiv Opto-electronic scale reading apparatus having light-transmissiv

1995-12-22

1998-03-10

Le, Que

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250237G, 356373, G01J 350

Patent

active

057264422

ABSTRACT:
An opto-electronic scale reading apparatus includes a reflective scale (410) relative to which a readhead is movable. The readhead includes a light source in the form of the emission end of an optical fiber (300), which directs light via collimating lens (420), beam splitter (310), and deflecting optics (312,314) onto the scale. The light reflected from the scale passes through an index grating (416) to generate a series of spatial fringes in the plane of an analyzer (418). The analyzer comprises a series of elongate light transmitting color filters, extending substantially parallel to the fringes and arranged in a repeating pattern (e.g. red, blue, green, red, blue . . . ); like-colored elements are separated by a distance corresponding to an integer multiple of the fringe pitch. The array (418) encodes the fringes into a plurality of phase-shifted signals, which pass through the beam splitter (310), lens (420) and back along fiber (300). A plurality of corresponding color filters, provided at the other end of the fiber (300) deflect the relevant color light onto individual photodetectors thereby to produce a plurality of cyclically modulating phase-shifted electrical signals, from which the relative displacement of the readhead and scale may be determined. Where the fiber is of plastics material the light is preferably in the infra-red spectrum to produce attenuation.

REFERENCES:
patent: 4814601 (1989-03-01), Jones
patent: 5064290 (1991-11-01), McMurtry et al.
patent: 5214280 (1993-05-01), Rieder et al.
patent: 5302820 (1994-04-01), Henshaw et al.
patent: 5302821 (1994-04-01), Igaki et al.

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