A method of designing asymmetric double-sided off-axis aspheric mirror detection compensation zoom light path

With the development of multispectral common-aperture high-precision detection technology, the asymmetric double-sided off-axis aspheric mirror is playing an increasingly important role in characterizing the correcting phase difference, increasing the relative caliber of system, expanding the view angle of field, simplifying system structure, and reducing weight and volume. But high-precision detection is a key step restricting the applications of these mirrors. At present, the compensation method of the interference test is the most effective mean of off-axis aspheric surface detection which has a simple structure, large compensation range, small number of components and is easy to control. However for the detection of asymmetric double-sided off-axis aspheric mirrors, two sets of alone compensators are still used, in which the efficiency is low and the switching compensator will reduce the accuracy of detection. Aiming at this problem, in this paper we propose a zoom null compensation method which is based on the Offner refracting compensation method. In this method, the off-axis aperture stop causes the light to be off-axis and split, the common lens group is moved to zoom, and the mirror folds the light path. There are two off-axis apertures are provided for off-axis and splitting, four lenses which form three lens groups are used to move positions for zooming, two mirrors are used to fold light. An optical design software is used to simulate the experiment, and implements the design for the high-precision detection of optical path for the asymmetric double-sided off-axis aspherical mirror by using this set of null compensation method. The simulation result shows that the theoretical residual wave aberration increases up to 0.0003λ root-mean-square (RMS) and 0.0001λ RMS with the designed system compensation, which meet the requirement for detection. At the same time, the tolerance analysis is carried out according to the design result, the actual residual wave aberrations within the existing tolerance range are 0.0326λ RMS and 0.0316λ RMS, which meet the requirements for manufacturing and assembly. The present work provides a new idea for the high-precision detection of asymmetric double-sided off-axis aspheric mirror. At the same time, the quality of the detected beam in this paper is achieved under ideal conditions, and the quality of beam will be considered in the next research work.