||鄭正元, 古達知, 吳乾埼,|
|An apparatus to determine the displacement (or angle) with respect to scale. The V shaped prism divides one laser beam to two laser beam. These two laser beams meet same point on the scale and the –nth diffracted order of two beams have same direction. So the interference of two –nth diffracted order measures the photodetector. When the read head moves the intensity of interference will change and the photodetector can measure generate sinusoids signal.