Absolute measurement is an effective way to obtain high-precision optical surface measurements. This paper describes a convenient absolute testing approach that allows reconstruction of surfaces using Zernike polynomials. This method requires a classical three-flat measurement and a one-rotation measurement before reconstructing the surface. Utilizing a well-established procedure, the absolute surface profile of the testing surface can be reconstructed with more Zernike orders than are provided by Fritz’s method. In particular, simulation of the testing error through recalculation of the test surface profile at a different angle could provide the optimized angle with a minimum testing error. This implies that an additional rotation measurement for the optimized angle can improve testing accuracy. The experimental results of a 100-mm flat surface provided a reflected root mean square (RMS) of 2.6 nm and a residual RMS of 0.1 nm.
As a result of the coupling process between the incident and the guided waves, the zero-order reflection exhibits a
narrow spectral response. There were some investigations on how to control the reflectance response of filters which
have diffractive structures. But these investigations only considered the case at the 0 deg azimuthal angle. In this work,
one optimized structure of ZODF which had conspicuous spectral shift effect and certain spectral response for the TE
polarization mode was given.
The ratio measurement of reactive ion beam etching rate using optical interferometry was investigated. The principle is that the depth of groove could be showed by the bend of interference fringe. Using interferometric measurement, the depths of groove before and after etching were determined and marked as d<sub>1</sub>, d<sub>2</sub>. One new groove whose bottom was on the substrate was made. There are three photos before etching and after etching new grooves were got. It is found that the ratio is 10:3 under the conditions of experiment. Compared with traditional measurement, this kind of way has some advantages such as simplicity, higher measurement precision and so on.