Photoelectric scanning

Most HEIDENHAIN encoders operate using the principle of photoelectric scanning. Photoelectric scanning of a measuring standard is contact-free, and as such free of wear. This method detects even very fine lines, no more than a few microns wide, and generates output signals with very small signal periods. The finer the grating period of a measuring standard is, the greater the effect of diffraction on photoelectric scanning. HEIDENHAIN uses two scanning principles:

The imaging scanning principle for grating periods from 10 µm to approx. 70 µm.

The interferential scanning principle for very fine graduations with grating periods of 8 µm and finer

Other scanning principles

Some encoders function according to other scanning methods. ERM encoders use a permanently magnetized MAGNODUR graduation that is scanned with magnetoresistive sensors.

ECI/EQI rotary encoders operate according to the inductive measuring principle. Here, moving graduation structures modulate a high-frequency signal in its amplitude and phase.