Orthogonal ray scheme: a method for processing interference patterns and reconstructing the shape of a test convex mirror

This report is devoted to the processing of the interference pattern of the tested mirror, obtained using the orthogonal ray scheme, where the convex testing surface is illuminated by a collimated beam, which is perpendicular to the optical axis of the surface. The interference pattern is created by two wavefronts, one of which is reflected from the mirror, while the other wavefront bypasses the mirror and travels directly to the detector plane. The result of interference pattern processing is a topography map formed by several tangential profiles. The proposed method is suited for large diameter convex spherical and aspherical mirrors and does not require a priori information of surface under the test, such as the vertex radius of curvature and the conical constant. Theoretical foundation of the data processing method are presented.

Printing special surface components for THz 2D and 3D imaging

The paper reports an off-axis large focal depth THz imaging system which consists of three 3D printed special surface components (two aspherical mirrors and an axicon). Firstly, the optical design software is used to design and optimize the aspherical parabolic mirror. Secondly, the optimized mirror is prepared by a 3D printing and metal cladding method. Thirdly, a THz axicon is designed for generation of quasi-Bessel Beam and a new geometric theoretical model of oblique incident light for axicon is established. Finally, the imaging system based on the special surface components is constructed. Its maximum diffraction-free distance is about 60 mm, which is 6 times higher than the traditional system. To verify the effectiveness, THz two-dimensional imaging experiments and three-dimensional computed tomography experiment are carried out. The results are consistent with the design and calculations.

Методика измерения параметров вогнутых крупногабаритных асферических зеркал с помощью датчика волнового фронта

A methodology has been developed for measuring radius R _v and eccentricity (conic parameter k ) of large concave aspherical mirrors using a wavefront sensor. Analytical expressions that directly relate Zernike coefficients a _4 and a _9 to parameters R _v and k of the mirror are obtained. It is shown that the technique does not require accurate mirror alignment before measurements. A computer analysis showed that the developed scheme enables measurements with errors of δ R _v < 0.1% and δ k < 0.01 for mirrors with radii from 100 to 2000 mm and with errors of δ R _v < 0.01% and δ k < 0.001 for mirrors with radii of more than 5000 mm.