Design and Fabrication of High Resolution Diffractive Optical Encoder

Rotary encoders are angular measurement devices that are used in many industrial applications. High-precision angle measurement technology is the basis for servomotor functionality; it determines the capabilities of semiconductor processing, ultra-precision machining, and precision alignment. The present study adopted an optical pickup scheme and, by generating an incident beam on a grating’s narrow structure, used the diffraction phenomenon to develop a high-precision absolute optical encoder for solving the problem of signal to noise ratio (SNR) reduction due to code disc shrinkage in geometric optical designs. Experimental results prove that the structure of the diffractive optical encoder proposed in the present study can achieve a resolution of 14 bit/rev; with the addition of a two-dimensional or binary sine-wave grating design, signal subdivision technology can be used to further improve the signal resolution to 10-12 bit/rev, thus achieving ultra-high precision measurement.