Identification card decoder

Claim 1

In a security system comprising at least one decoder for a plurality of differently encoded identification cards of a type in which each card includes an encoded light-modifying portion responsive to illumination thereof with a single readout beam of incident light for deriving a unique pattern of output light in accordance with a binary code manifested by the light-modifying portion of that card then being illuminated: a. wherein each of said unique patterns comprises a plurality of simultaneously-occurring separate output light beams including a first reading sequence initiation beam and a first group composed of beams which manifest ONE bits of said binary code intersecting the circumference of a first-radius circle about an optic axis at angularly displaced positions thereof; the relative angular position on said circumference of said firstradius circle of any beam of said first group with respect to that of said first reading sequence initiation beam bearing a given correspondence with the ordinal position in said code of the bit manifested thereby; said output light beams further including a second reading sequence initiation beam and a second group composed of beams which manifest binary ZERO bits of said binary code intersecting the circumference of a secondradius circle about said optic axis At angularly displaced positions thereof, the relative angular position on said circumference of said second radius circle of any beam of said second group with respect to that of said second reading sequence initiation beam bearing said given correspondence with the ordinal position in said code of the bit manifested thereby, and b. wherein said decoder includes a first light sensor situated on the circumference of said first-radius circle and a second light sensor situated in given spaced relationship with respect to said first light sensor on the circumference of said secondradius circle; means for rotating said pattern with respect to said first and second light sensors about said optic axis to thereby illuminate said first light sensor in sequence with said first reading sequence initiation beam and each beam of said first group and illuminate said second light sensor in sequence with said second reading sequence initiation beam and each beam of said second group, said given spaced relationship between said first and second light sensors being such that said first and second light sensors, respectively, are illuminated simultaneously by said first and second reading sequence initiation beams, respectively, and circuit means coupled to said first and second light sensors and responsive to the respective outputs therefrom during said rotation of said pattern for determining the binary code manifested by said pattern.