Abstract: A linear scale measuring device of the absolute type capable of exhibiting high resolution and accomplishing the measuring operation with high accuracy. In the device, A cycle of indented lines for increment data is set to be twice as large as that of indented lines for absolute data. Also provided is an absolute data detection section which detects absolute data values corresponding to the indented lines, and a data converter which converts an output of the absolute data detection section into a digital signal. An operation section which includes a computing element adds either +1 to -1 to the digital signal output from the data converter, or does not add to the digital signal, in accordance with an output signal from an interpolation section.

Abstract: A measuring device is disclosed which is capable of exhibiting increased resolution. The device is constructed to detect a moire fringe produced by two scales as A and B phase signals different in phase by 90.degree. and to convert each of the phase signals into a frequency-modulated signal by means of a carrier of a predetermined cycle to digitally read out the deviation of a phase varied with relative movement between both scales.

Abstract: A position feedback system capable of effectively preventing an NC apparatus from failing in a position signal reading operation due to mechanical vibration of a machine tool or the like, including an up-down counter for counting up or down phase signals supplied from a machine position encoder, a comparator for comparing the counted value with a reference value, and a pulse generator for supplying an up- or down-counting pulse having a time period larger than a minimum time period necessary for the reading operation of the NC apparatus to the comparator to initiate a comparison operation regarding the counter contents which generally reflects the number of phase signals, since spurious noise signals have a tendency to cancel each other out. Based on the comparison, a counting pulse is fed to the NC apparatus and a pulse is applied to the counter to cancel one counted value. The operation is carried out until the counted value becomes the same as the reference value.