A joystick including an optical encoder with film strips in sliding contact

摘要

An optical encoder having a concentric cylindrically disposed reticle and moving unit with each having alternating transparent and opaque regions. A light emitter is located in each of two windows on one side of the recticle and moving unit while a light sensor is located on the other. The spacing of transparent and opaque regions in the reticle relative to that in the moving unit is such that when the transparent regions in one window are aligned those in the other unit are sufficiently non-aligned to produce quadrature and enable detection of both motion and direction of motion.