Data read-out system and apparatus useful for angular measurements

Abstract

Data acquired from a source such as a coded disc is processed so as to be free of ambiguities associated with boundary transitions where the data source produces groups of bits which have least significant ordering and higher significant ordering. Wherever a common transition boundary between the bit groups occurs, ambiguities from misalignment of these boundaries are avoided by controlling the higher ordered bit transitions from the lower ordered bit transitions. Circuitry tracks and stores the higher order bits by synchronous updating whenever no misalignment or skew sensitive transitions are encountered. Logic circuitry continuously inspects the lower significant bits to determine the presence or absence of a zone surrounding the common transition boundary and also detects the actual passage and direction of the transition boundary in the lower significant bit group. This logic corrects the counter stored higher order bit counts in conformity with the status of the lower significant bit states. The system output is a composite of the lower significant digits read directly and the controlled and updated higher significant digits with appropriate code conversion. Whenever the data source is an optical coded disc or the like, the data acquired can be enhanced by an arrangement of light collimating and focusing elements relative to the coded transparent/opaque areas of the disc cell tracks.