– detect position through code by reflector or by passing light transmission to photo detector
– displacement (relative) is measured in the form of a pulse train with a frequency equal to the speed of movement
Figure 3.33 Optical digital position sensor: (a) and (b) rotary shift, TX-RX parallel, (c) and (d) horizontal shift, TX-RX forming angle.
– motion detection utilizes two signals with different pulse times
Figure 3.34 Rangakain test to determine the direction of movement / position
– absolute position detected using digital number code
• for extreme change detection one code is used as a clock signal
• other alternatives use code that allows only one change as in Gray code
• Angular code is better than linear code due to the direction of thermal expansion on the code plate
Figure 3.35 The clock pulses generated based on binary numbers
– small position displacement measurements can be done with Moire pattern
• the upright and oblique pattern strengthens the (size) shift x direction to the line pattern in the y direction
• changes are read optically
Figure 3.36 Small position changes using Moire mode