Holographic grating lithography system and a method for adjusting the self-collimation of the interference optical path thereof

A holographic grating lithography system of manufacturing parallel equidistant striped holographic grating, comprising:

• a coherent light source, a beam splitter, a first reflecting mirror, a second reflecting mirror, a first pinhole filter, a second pinhole filter, a first collimation lens, a second collimation lens, a first Volume Bragg grating, a second Volume Bragg grating, a first photodetector, and a second photodetector,
• wherein a light beam is emitted by the coherent source is split into a transmitted light beam and a reflected light beam after passing through the beam splitter, the first reflecting mirror, the first pinhole filter and the first collimation lens are sequentially placed along the light propagation direction of the reflected light beam, the second reflecting mirror, the second pinhole filter and the second collimation lens are sequentially placed in light path of the transmitted light beam, the reflected light beam is a first exposure light beam after passing through the first collimation lens, the transmitted light beam is a second exposure light beam after passing through the second collimation lens, the first pinhole filter is placed in the position of the object focus of the first collimation lens, the second pinhole filter is placed in the position of the object focus of the second collimation lens, and
• wherein the position near the coherent light source is defined as the front, the position of the light propagation direction is defined as the back, the first Volume Bragg grating is placed in the back of the first collimation lens and the diameter of the first Volume Bragg grating is smaller than the diameter of the first collimation lens, the incidence angle between the exposure light beam and the first Volume Bragg grating is equal to the Bragg angle of the first Volume Bragg grating, the first photodetector is placed in the back of the −1 grade of transmission diffraction light path of the first Volume Bragg grating where the first exposure light beam being incident, used to measure the diffraction efficiency of −1 grade transmission diffraction light, and
• wherein the second Volume Bragg grating is placed in the back of the second collimation lens and the diameter of the first Volume Bragg grating is smaller than the diameter of the second collimation lens, the incidence angle between the second exposure light beam and the second Volume Bragg grating is equal to the Bragg angle of the second Volume Bragg grating, the second photodetector is placed in the back of the −1 grade of transmission diffraction light path of the second Volume Bragg grating where the second exposure light beam being incident, used to measure the diffraction efficiency of −1 grade transmission diffraction light.