Positive resist was used to record holographic plane gratings. In order to have rectangular groove profiles a nonlinearly acting developer liquid was chosen. When gratings were read, the incidence angle of the reading laser was varied from the Bragg angle to the direction of the plate normal. If the grating profiles were rectangular the diffraction efficiency (DE) at normal incidence should have been low. However, noticeable DE:s were detected. The high efficiencies were due to the rounding of the grating groove edges. Thus by measuring the DE at different angles the rounding of the profile could be estimated.
Olli Salminen, Olli Salminen,
"Photoresist grating profile estimation by using different incidence angles", Proc. SPIE 1732, Holographics International '92, (2 March 1993); doi: 10.1117/12.140387; https://doi.org/10.1117/12.140387