High optical subdivision structure of auto-collimation grating interferometer

The invention relates to a high optical subdivision structure of an auto-collimation grating interferometer. The structure comprises a scale grating, a first reflector and a second reflector. A measuring light beam is input to the scale grating in an angle close to the Littrow angle, and diffracted by the scale grating; diffracted light of the diffraction order -1 is placed in a first plane, input to the first reflector, reflected by the first reflector, placed in the first plane again, and then input to the scale grating also in the angle close to the Littrow angle; the measuring light beam is reflected between the scale grating and the first reflector in a reciprocating manner, input to the second reflector vertically, and returned along the original light path; and thus, an auto-collimation structure is formed. The optical subdivision time is increased to N, light is input in the angle close to the Littrow angle, design of the scale grating is simpler, and the times that the light beam is diffracted by the scale grating is increased, namely, the optical subdivision times of the grating interferometer is increased.