Optical encoder

Claim 1

A device for digitally encoding the position of a movable element, said device comprising a code member adapted to be mechanically coupled to the movable element to be encoded and to move in either a forward or a reverse direction in response to movement of the element to be coded, said member defining a plurality of generally parallel tracks containing sectors of two types, the sectors of each track being alternately transparent and opaque and being of approximately equal length, said tracks including a least significant track having sectors which are shorter in length along the direction of movement of the code member than the sectors of the other tracks, the length of the sectors of the other of said tracks being different from one another, each of the transparent sectors of said least significant track defining two boundaries extending crosswise of said least significant track at the transitions between said transparent sector and the adjacent opaque sectors, said boundaries dividing the code member into segments, all of the transitions between transparent and opaque sectorS on all of the tracks being disposed on said boundaries, each segment of the code member containing at least a portion of a sector of each of the tracks of the code member in a unique combination of transparent and opaque sectors, a light source for illuminating the code member, a first photoconductive photocell disposed opposite the least significant track of the code member for receiving light as modulated by said least significant track, said first photocell being disposed on a first fixed line extending crosswise to the direction of movement of the code member, said tracks including a second track of second least significance, a pair of photoconductive photocells mounted in fixed positions opposite said second track of the code member for receiving light as modulated by said second track, said second track having sectors of a greater length than the sectors of the least significant track but of a lesser length than the sectors of the other tracks of the code member, one photocell of the pair of photocells being disposed on a second line extending crosswise to the direction of movement of said code member, said second line being parallel to but ahead of said first line in relation to the movement of said code member, the other photocell of said pair of photocells being disposed on a third crosswise line which is parallel to but behind the first line in relation to the movement of the code member, each of said photoconductive photocells being conductive in an illuminated condition and nonconductive in a dark condition, and circuit means electrically connected to the photocells for electrically reading the output of said photocells, said circuit means including first and second output terminals, means coupling said first photocell to said first terminal to produce energization of said first terminal in one of said conditions and deenergization of said first terminal in the other of said conditions of said first photocell, an inverter connected between said first and second terminals to energize said second terminal when said first terminal is deenergized while deenergizing said second terminal when said first terminal is energized, and a third output terminal, one photocell of said pair being connected between said first and third terminals whereby said third terminal is energized when said first terminal is energized and the last mentioned photocell is illuminated, the other photocell of said pair being connected between said second and third terminals whereby said third terminal is energized when said second terminal is energized and the last mentioned photocell is illuminated.

Claim 2

A device for digitally encoding the position of a movable element, said device comprising a code member adapted to be mechanically coupled to the movable element to be encoded and to move in either a forward or a reverse direction in response to movement of the element to be coded, said member defining a plurality of generally parallel tracks containing sectors of two types, the sectors of each track being alternately transparent and opaque and being of approximately equal length, said tracks including a least significant track having sectors which are shorter in length along the direction of movement of the code member than the sectors of the other tracks, the length of the sectors of the other of said tracks being different from one another, each of the transparent sectors of said least significant track defining two boundaries extending crosswise of said least significant track at the transitions between said transparent sector and the adjacent opaque sectors, said boundaries dividing the code member into segments, all of the transitions between transparent and opaque sectorS on all of the tracks being disposed on said boundaries, each segment of the code member containing at least a portion of a sector of each of the tracks of the code member in a unique combination of transparent and opaque sectors, a light source for illuminating the code member, a first photoconductive photocell disposed opposite the least significant track of the code member for receiving light as modulated by said least significant track, said first photocell being disposed on a first fixed line extending crosswise to the direction of movement of the code member, said tracks including a second track of second least significance, a pair of photoconductive photocells mounted in fixed positions opposite said second track of the code member for receiving light as modulated by said second track, said second track having sectors of a greater length than the sectors of the least significant track but of a lesser length than the sectors of the other tracks of the code member, one photocell of the pair of photocells being disposed on a second line extending crosswise to the direction of movement of said code member, said second line being parallel to but ahead of said first line in relation to the movement of said code member, the other photocell of said pair of photocells being disposed on a third crosswise line which is parallel to but behind the first line in relation to the movement of the code member, each of said photoconductive photocells being conductive in an illuminated condition and nonconductive in a dark condition, and circuit means electrically connected to the photocells for electrically reading the output of said photocells, said circuit means including first and second output terminals, means coupling said first photocell to said first terminal to produce energization of said first terminal in one of said conditions and deenergization of said first terminal in the other of said conditions of said first photocell, an inverter connected between said first and second terminals to energize said second terminal when said first terminal is deenergized while deenergizing said second terminal when said first terminal is energized, and a third output terminal, one photocell of said pair being connected between said first and third terminals whereby said third terminal is energized when said first terminal is energized and the last mentioned photocell is illuminated, the other photocell of said pair being connected between said second and third terminals whereby said third terminal is energized when said second terminal is energized and the last mentioned photocell is illuminated.