Heterodyne grating interferometry system based on secondary diffraction

A heterodyne grating interferometry system based on secondary diffraction comprising a single-frequency laser, an input optical fiber, an acousto-optic modulator, a reading head, a measurement grating, an output optical fiber, a photoelectric conversion unit and an electronic signal processing unit,

• wherein the single-frequency laser emits a single-frequency laser, which enters the acousto-optic modulator through the input optical fiber, and is divided into a reference light and measurement light to be input to the reading head, wherein the reading head and the measurement grating convert the reference light and measurement light into a reference interference optical signal and a measurement interference optical signal and send them to the photoelectric conversion unit through the output optical fiber,
• wherein the photoelectric conversion unit converts the measurement interference optical signal and the reference interference optical signal into a measurement interference electrical signal and a reference interference electrical signal and sends them to the electronic signal processing unit, and calculates 2-degree-of-freedom linear displacement of the measurement grating,
• wherein the reading head comprises an interferometer lens group, the single-frequency laser emits multiple beams of single-frequency laser, the multiple beams of single-frequency laser are divided into multiple beams of reference light and multiple beams of measurement light by the acousto-optic modulator,
• wherein the multiple beams of reference light and the multiple beams of measurement light are transmitted in a space-separated manner, and enter the interferometer lens group at respective different positions, and generate multiple channels of measurement interference signals and multiple channels of reference interference signals, and
• wherein the interferometer lens group comprises a plurality of reflectors, a plurality of quarter-wave plates, a plurality of polarization beam splitters, a plurality of retroreflectors, a plurality of lateral beam splitter prisms and a plurality of refractors.