Method and apparatus for detecting origin of measurement

摘要

An interpolation circuit generates two-phase square wave signals PA and PB from two-phase sinusoidal wave outputs ØA and ØB supplied from a photoelectric encoder. A gate signal generator slices a primary origin signal ØZ supplied from the photoelectric encoder with a predetermined reference level VRef to generate a gate signal Z. A first counter begins to count position pulses generated from the two-phase square wave signals PA and PB when the gate signal Z becomes active. A count value of the first counter is divided by two when the gate signal Z becomes non-active and the divided value is preset into a second counter. The second counter counts the position pulses generated from the two-phase square wave signals PA and PB. A comparator feeds an output origin signal PZ when a count value of the second counter reaches a predetermined offset value N.