Plane-parallel optical elements, such as optical resonators, laser rods or wave plates, are widely used in many optical setups. Both planar surfaces of the element have to be manufactured with high precision in order to assure proper quality of the element and thus these surfaces have to be accurately measured. However, the interferometric measurement process, usually used for the surface form topography characterization, suffers from multiple interference patterns. This increases the total measurement error. In this paper the frequency-tuned interferometric method, that overcomes this problem, is demonstrated and compared to commonly used techniques using immersion liquid. Using a tunable laser source together with a frequency separation of the phase information from both surfaces, fringes from the first and second surface can be distinguished. Also, the interference between both surfaces can be used to obtain the wedge and thickness values of the specimen.
Solid-state lasers are broadly used in various applications. The most common gain medium is neodymium-doped yttrium aluminum garnet (Nd:YAG). Very important parameters are angle between polished face surfaces and result wave-front deformation. These parameters are usually measured with two different methods. The paper presents a procedure for measurements of the parameters in a single measurement sequence using Fourier transform phase-shifting interferometry. The results are figures of both optical surfaces, and their mutual position, wave-front deformation, and homogeneity of refractive index. Based on the knowledge of these parameters can be done precise correction of resulted wave-front and of the wedge by polishing of face surfaces. The presented method reduces manipulation with the elements is non-sensitive to the operator and allows more precise wavefront correction thanks to the knowledge of inhomogeneity of material.
The demands on the quality of large aperture spherical and mild aspheric optical surfaces continue to rise in modern optical systems. Due to the aperture size of these surfaces measuring of their shape is quite problematic. One of the ways to measure these surfaces is the subaperture stitching interferometry. Its accuracy is highly depended on lattice design and accuracy of the positioning system. Optimal lattice design in relation to transmission element applied in interferometer together with coordinates calculation for the positioning system for measuring individual subapertures is the subject of this paper. To set the required orientation and position of the optical surface relative to the interferometer positioning system with six degrees of freedom was used. Three of them were realized as prismatic kinematic pairs and remaining three as revolution joints. In this paper the choice of coordinate systems for individual axes of the positioning system together with inverse kinematics used for setting the correct position and orientation of the optical surface are described.
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