| As a typical type of aspherical optical surface,off-axis hyperboloid has been widely used in many optical systems.Due to the influence of non-spherical degree and off-axis amount of off-axis hyperboloid mirror,the difficulty of its processing and inspection is greatly increased.Optical inspection is an important support in the process of optical part manufacturing,and the research on the detection method of off-axis hyperboloid is crucial to the precise processing of off-axis hyperboloid mirrors.Computer-generated hologram(CGH)element is increasingly valued in the detection technology of high-precision optical elements due to its advantages of large design freedom and simple structure.This paper studied the off-axis hyperboloid detection technology based on CGH,taking the CGH element as the zero position compensator in the interferometric inspection method.The main contents are as follows:Firstly,the domestic and foreign application status of off-axis hyperboloid and the development of non-spherical detection technology based on CGH are introduced.The classification of CGH is discussed,and the important parameters of CGH are analyzed.The relationship between CGH diffraction efficiency and the duty cycle is given.The layout form of CGH sectorial annular reference type is selected,and phase-type CGH is used for the optical detection of the measured surface.Secondly,based on theoretical research,the design method of system structure is presented for an off-axis concave hyperboloid with a diameter of 40 mm,a vertex curvature radius of 606 mm,a conical coefficient of-1.063,and an off-axis amount of 23.2mm.The primary hologram design result of the detection system is obtained to be better than 0.0001 (?)wavefront error,with a line-spacing of 11.9μm at the densest position.Then,the alignment hologram is designed according to the results of the main hologram design,and the calculated line spacing is 12.8μm at the densest position.Based on the detection of the off-axis concave hyperboloid,the main hologram of an off-axis convex hyperboloid is designed by using CGH and the spherical mirror hybrid compensation detection method.Finally,a detection experiment of off-axis hyperboloid was conducted using processed CGH elements and the CGH detection results of the tested off-axis hyperboloid were compared with the results of the traditional null test method,which verified the CGH detection system and enabled an error analysis of the entire detection system. |
