Imperfections of Scalar Approximation in Calibration of Computer-Generated Holograms for Optical Surface Measurements

Computer-generated hologram (CGH) null correctors are used as accuracy standards for interferometric measurements of optical surfaces and optical systems. Diffractive optics calibrators (DOCs) have been developed to evaluate the phase tolerance of CGHs based on scalar approximation by measuring variations in duty cycle and etching depth. However, if the grating period of a CGH < 5 lambda, the scalar approximation is not accurate for phase analysis and reconstruction. In this study, the measurement errors of DOCs with small-period CGHs were investigated and experimentally verified. Results show that the imperfections of scalar approximation in CGHs cannot be ignored and the development of rigorous evaluation methods to improve the measurement accuracy of CGHs is of great practical significance.

Automated summary

The study investigates and experimentally verifies the measurement errors of DOCs with small-period CGHs, showing that imperfections of the scalar approximation in CGHs cannot be ignored. Developing rigorous evaluation methods to enhance the measurement accuracy of CGHs is of significant practical importance.