One, according to light in the grating is reflected is still transmitted into the transmission grating and reflective grating
The transmitted grating is a line pattern made from the surface of the glass that is equal to the distance between the light and the light.
The reflective grating is on the surface of the ruler or stainless steel strip, and the light is processed into a mirror with strong reflective light, and the grating stripe is produced by the photographic etching process.
Second, according to the grating shape can be divided into linear grating and circular grating
Linear gratings are used to detect linear displacements. A circular grating is used to detect angular displacements.