Recently the authors of this paper dealt with computergenerated holograms (CGHs) for the optical inspection of the surface roughness and waviness of relatively smooth surface roughness standards.1 The idea was to exploit two separate sensors to provide information on one hand about the surface roughness by measuring the contrast parameter as defined in Ref. 1, and on the other hand to inspect the surface curvature. Later, we improved the operational function of the surface sensor.
James Zhiqing Wen,
"Hadamard codes of m not equal to 2n in phase-code multiplexed holographic memories," Optical Engineering 35(12), (1 December 1996). http://dx.doi.org/10.1117/1.601118