Method of interval interpolation

Claim 1

In a position measuring system comprising a measuring scale, a scanning unit for scanning the scale and generating at least two periodic analog signals in response to relative movement between the scale and the scanning unit, an evaluating arrangement for processing the analog signals, means for generating digital signals corresponding to the analog signals, and an interpolating arrangement, included in the evaluating arrangement and responsive to the digital signals, which comprises a computer for computing interpolation values within a signal period of the periodic analog signals, wherein the computer comprises means for correcting the digital signals prior to the computation of interpolation values by use of a plurality of previously determined correction values in order to improve accuracy of the interpolation values, the improvement comprising: a plurality of detector elements responsive to the analog signals, each detector element operative automatically to generate a respective correction signal in response to at least one of the analog signals during relative movement between the scale and the scanning unit, each of said correction signals indicative of a respective signal parameter characteristic of at least one of the analog signals and chosen from the group consisting of: direct voltage component, amplitude, and phase difference of the analog signals and means for providing the correction signals as the correction values to the computer; said detector elements and providing means cooperating automatically to determine and supply the correction values to the computer.