Bian to principle

In practical applications, the displacement has two directions, namely a selected direction, the displacement of plus or minus points, so the moire fringe signal is measured by a photoelectric element determining displacement direction. In order to sense, need to have a PI / 2 phase difference of two moire fringe signals. As shown in figure 2, in the position of 1/4 fringe spacing apart put two photoelectric elements, have two phase difference of PI / 2 electrical u01 and u02, get two square wave signals after plastic u01 'and u02'. Grating is moves ahead u01 u02 90 degrees, reverse moves ahead u02 u01 90 degrees, so by distinguishing circuit can be set for the grating direction.

Folds subdivision technology

With the improvement of measurement accuracy, lattice spacing can not meet the requirements for the unit, need to take the appropriate measures of moire fringe subdivision. A niche is the moire fringe signal change is a cycle, issued a number of pulses, in order to reduce pulse equivalent. N pulse, such as a cycle is to improve measurement precision by n, and each pulse equivalent to the original lattice spacing of 1 / n. As segment after the counting pulse frequency increased n times, therefore also call n frequency doubling.

Usually use two kind of segmentation method: first: direct segmentation. In the position of 1/4 moire-fringe spacing difference put two photoelectric elements, two phase difference of 90 o electrical signal can be obtained, using inverter after inverting get four are in turn 90 o ac signal. Similarly, placed between the two moire fringe in four quarter fringe spacing apart optoelectronic components, also can obtain four ac signal phase difference of 90 o, four times the frequency segment. Second: the subdivision circuit.