Littrow grating interferometry device and use thereof

A Littrow grating interferometry device, characterized by comprising:

• a light source, a polarizing beam splitting prism, a reflection assembly, a detector, and a first diffraction grating and a second diffraction grating having identical parameters;
• wherein, output light of the light source is composed of first measuring light and second measuring light having different frequencies and mutually perpendicular polarization states, the first diffraction grating and the second diffraction grating are parallel to each other and are positioned to be opposite to each other on two sides of the polarizing beam splitting prism, and both the first diffraction grating and the second diffraction grating reflect diffracted light along an original incident optical path;
• of other two sides of the polarizing beam splitting prism, the reflection assembly is disposed on one side, and the light source and the detector are disposed on the other side;
• a first quarter-wave plate is disposed between the reflection assembly and the polarizing beam splitting prism;
• a second quarter-wave plate is disposed between the first diffraction grating and the polarizing beam splitting prism;
• a third quarter-wave plate is disposed between the second diffraction grating and the polarizing beam splitting prism;
• and
• the polarizing beam splitting prism is used to separate the first measuring light and the second measuring light, such that light in a horizontal polarization state is transmitted and light in a vertical polarization state is reflected;
• the reflection assembly is used to reflect incident light to the detector.