Shaft position encoders

Claim 2

An optical shaft position encoder comprising: means for producing a plurality of beams of modulated light, said beams of modulated light having phases that are substantially equally spaced with respect to one another; a polarizer for each beam of modulated light, the principal axes of the polarizers being substantially equally angularly spaced with respect to one another; means for analyzing said beams of light, said last mentioned means being adapted to be rotated in unison with the shaft; and means deriving from said analyzing means a signal representative of the angular position of the shaft.

Claim 3

The optical shaft position encoder of claim 1, wherein the means deriving the signal representative of the angular position of the shaft compares a first signal obtained from the beams of light after passage through said analyzing means with a second signal driving one of said means for producing a plurality of beams of modulated light.

Claim 4

The optical shaft position encoder of claim 1, wherein the means deriving a signal representative of the angular position of the shaft is a digital time interval counting means.

Claim 5

The optical shaft position encoder of claim 1, wherein the means for producing a plurality of beams of modulated light is a plurality of light-emitting diodes.

Claim 6

The optical shaft position encoder of claim 4, wherein the plurality of light sources are modulated by driving voltages having phases that are substantially equally spaced with respect to one another.

Claim 7

The optical shaft position encoder of claim 5, wherein the means deriving the signal representative of the angular position of the shaft compares a first signal obtained from the beams of light after passage through said analyzing means with one of the voltages driving one of the light sources.

Claim 8

An optical shaft position encoder comprising: means for producing a pluralIty of beams of modulated light, said beams of modulated light having phases that are substantially equally spaced with respect to one another; a polarizer for each beam of modulated light, the principal axes of the polarizers being substantially equally angularly spaced with respect to one another; means for analyzing said beams of light, said last-mentioned means being adapted to be rotated in unison with the shaft; and means deriving from said analyzing means a signal representative of the angular position of the shaft by comparing the signal emerging from said analyzing means with a signal representative of one of said beams of modulated light.

Claim 9

An optical shaft position encoder comprising: means for producing a pluralIty of beams of modulated light, said beams of modulated light having phases that are substantially equally spaced with respect to one another; a polarizer for each beam of modulated light, the principal axes of the polarizers being substantially equally angularly spaced with respect to one another; means for analyzing said beams of light, said last-mentioned means being adapted to be rotated in unison with the shaft; and means deriving from said analyzing means a signal representative of the angular position of the shaft by comparing the signal emerging from said analyzing means with a signal representative of one of said beams of modulated light.

Claim 10

The optical shaft position encoder of claim 7, wherein the means deriving a signal representative of the angular position of the shaft is a digital time interval counting means.

Claim 11

The optical shaft position encoder of claim 7, wherein the means for producing a plurality of beams of modulated light is a plurality of light sources driven by modulated voltages with phases substantially equally spaced with respect to one another.

Claim 12

An optical shaft position encoder comprising: a plurality of light sources emitting a plurality of beams of modulated light, said sources being driven by a plurality of modulated voltages with phases substantially equally spaced with respect to one another; a polarizer for each beam of modulated light, the principal axes of the polarizers being substantially equally angularly spaced with respect to one another; an analyzer mounted on one end of a rotating shaft whose angular position is to be determined; detector means adapted to supply an electrical signal in function of the intensity of the light impinging thereon; a mirror placed behind said analyzer toward said detector means and a digital time interval counter electrically connected to said detector means and adapted to compare an electrical signal representative of one of the modulated voltages with said electrical signal from said detector means, whereby the phase differential between said electrical signals is representative of the angular position of the shaft.

Claim 13

An optical shaft position encoder comprising: a plurality of light sources emitting a plurality of beams of modulated light, said sources being driven by a plurality of modulated voltages with phases substantially equally spaced with respect to one another; a polarizer for each beam of modulated light, the principal axes of the polarizers being substantially equally angularly spaced with respect to one another; an analyzer mounted on one end of a rotating shaft whose angular position is to be determined; detector means adapted to supply an electrical signal in function of the intensity of the light impinging thereon; a mirror placed behind said analyzer toward said detector means and a digital time interval counter electrically connected to said detector means and adapted to compare an electrical signal representative of one of the modulated voltages with said electrical signal from said detector means, whereby the phase differential between said electrical signals is representative of the angular position of the shaft.

Claim 14

The optical shaft encoder of claim 10, wherein the means deriving a signal representative of the angular position of the shaft is a digital time interval counting means.

Claim 15

The optical shaft position encoder of claim 10, wherein, the plurality of light sources consists of three sources driven by three modulated voltages with electrical phase differences of 120*.

Claim 16

The optical shaft position encoder of claim 12, wherein the principal axes of the polarizers are rotated approximately 60* with respect to one another.