Large-format grating groove density measurement method based on optical interferometry

Abstract

In this research, an optical interference large-format grating groove density measurement method is proposed. The dual-frequency laser emits two beams of light to the test grating at Littrow Angle. The phase information of the test grating is obtained through the interference of the two diffracted light beams. Therefore, the groove density of the test grating can be calculated by the actual displacement value of the moving grating, according to the grating heterodyne measurement technology and laser interferometry technology. A system was built to verify the feasibility of the proposed method. The experimental results demonstrate that this method is capable of detecting the groove density of gratings ranging from 500 gr/mm to 3000 gr/mm in any region of the entire format, with the repetitive precision exceeding 0.01 gr/mm, and the uniformity repetitive precision surpassing 0.1 gr/mm. This method provides an effective means for fast and high-precision measurement of grating groove density.