Distortion Correction in Testing of Off-Axis Asphere with Computer-Generated Hologram

Research on measurement of depth aspheric surface using multifocal lens

“…In 1969, Lesem introduced the concept of phase holograms for coaxial reproduction of a single image [2] , in recent years, the main work of computer-generated hologram has been focused on the testing of aspheric surface shapes with large aperture and large asphericity. In 2013, in order to correct the distortion introduced in the null testing with computer generated hologram (CGH) for off-axis aspheric, a mapping distortion method is proposed based on affine transformation of the test ray [3] , in the same year, Xi'an Institute of Space Radio Technology proposed a computational holographic surface shape testing method for small-diameter depth aspheric surfaces, and the design and preparation process of its computer-generated hologram were explained in detail, and the surface shape testing of small-diameter depth aspheric surfaces was realized with high accuracy [4] In general, the testing accuracy of computer-generated hologram method is very high, but it can only measure a specific aspheric surface, so it has the disadvantage of low versatility [5] Non-null testing can effectively improve the versatility of depth aspherical interference testing, the method will reduce the interference fringe density to the detector, and then through the algorithm to eliminate the system error to complete the face shape testing [6][7] , based on this, this paper proposes a depth aspherical surface shape detecting method, this method can effectively complete the depth aspherical surface shape testing without limitation of individual compensation. It should be noted that when the focus spacing of the multifocal lens depends on the asphericity, so when the focus spacing is determined, any depth of asphericity that satisfies the R-number under the asphericity can be detected by simply placing the parts to be measured at different positions from the focus position.…”