Research on subaperture stitching and absolute measurement technique for large rectangular plane mirrors

Large rectangular plane mirrors are widely used in high-power laser systems and synchrotron radiation sources, their surface precision affecting optical system performance. High-precision measurement methods are required to match these mirrors. The oblique incidence absolute measurement technique based on the rotational averaging method is a commonly method for these mirrors. But this method is complex, requires two additional plane mirrors. And it is limited by the angle of incidence, making it impossible to achieve both large aperture and high-resolution measurement simultaneously. Moreover, the method requires disassembling the test mirror during measurement, which significantly complicates the setup and adjustment process. Addressing the aforementioned shortcomings, this paper presents a high-precision measurement method for large rectangular plane mirrors. This method combines subaperture stitching techniques with the absolute measurement approach using the double shear translation method. It divides the test mirror into multiple overlapping subapertures and applies the double shear translation method to conduct absolute measurement on each subaperture region sequentially. Subsequently, employs algorithm to stitch the results together to achieve a complete surface. This method balances large aperture and high-resolution measurement, eliminates the influence of the reference surface. During the measurement process, only translations of the test mirror are required, making setup and adjustment relatively straightforward. Experimental validation of this method has demonstrated its ability to achieve high-precision measurement of rectangular plane mirrors. This paper presents an effective approach for high-precision measurement of large rectangular plane mirrors.