The design of optical encoders dates back to the mid-1940s. In the meantime, Balelwin Piano developed the "tuning wheel" device, which aims to make the keyboard produce a homophonic sound to mimic other instruments. The Army learned that Balelwin was able to produce the tuning wheel mode very precisely on the photosensitive glass, so it used this technology to make a code plate. Later, for this instrument, a practical accuracy standard was specified and used to develop a coding system for aerospace and industrial position sensors. The optical encoder is then produced.