Patent RU-2623702-C1 (RU)
Inventor: BARYSHNIKOV NIKOLAJ VASILEVICH
IPC: G01B11/255
Filed: 2016-07-19
Granted: 2017-06-28
Abstract: FIELD: measuring equipment. 
     SUBSTANCE: device of determining the curvature radius of a large-sized optical part based on a wavefront sensor contains: an optical nozzle 2; an optical system 3 consisting of an afocal system of optical elements 3.1, 3.2, a beam splitting cube 3.3 between them and a point source of radiation 3.4. The optical element 3.1 is a collimating objective for the source 3.4 with the output of collimated radiation to the nozzle 2 and at the same time the elements 3.1, 3.2 match the apertures of the nozzle 2 and the sensor 4 located behind the element 3.2; the fixed location of the part 1 with its controlled surface facing the nozzle 2. The part 1, the nozzle 2 and the system 3 are located in series on a single optical axis. The nozzle 2, the system 3 and the sensor 4 form a single unit with the possibility of small varied displacements compared to the size of the curvature radius of a part surface 1 along the optical axis relative to the location of stationary part location 1. The optical axis of the sensor 4 coincides with the single optical axis of the part 1, the nozzle 2 and the system 3. There is no cube kink 3.3 of spherical wave fronts reflected from a surface of a part 1 back to the nozzle 2 and through the elements 3.1, 3.2 to the sensor 4, a cube 3.3 is used only for radiation input from the source 3.4 to the element 3.1. Method using the specified device is that in the starting position on the nozzle 2 of the single unit, here comes a spherical wavefront reflected from the part 1 with a radius curvature equal to the focal length ƒ n  of the nozzles 2, wherein after the nozzle 2 and the system 3 this wavefront comes to the sensor 4 in the form of a flat wavefront with a curvature radius equal to infinity. After this, by means of an additional small displacement compared with the value of the curvature radius Rz of the part surface 1 Δ of the single unit of the nozzle 2, the system 3 and the sensor 4 along the optical axis, the radius R z  is determined through the definition of the curvature radius of the spherical wavefront reflected from the surface of the part 1 taking into account the sensor 4, taking into account its geometric transformation by the system 3 by calculation using the formula of the segments for the nozzle 2 and the elements 3.1, 3.2 and using formulas for calculating the radius R z  taking into account the rule of signs (from geometric optics). Displacement Δ is chosen so that a spherical wavefront comes to the sensor 4 corresponding to the curvature radius of the spherical wavefront that is admissible as measured by the sensor 4 as small as possible, while the curvature radius of the spherical wavefront R n  at the inlet of the nozzle 2 is connected with the radius R z , the displacement Δ and the focal length ƒ n  by the formula:   from which for a known value of the radius R n , the desired value of the curvatures radius R z  of the controlled surface of the part 1 is determined. 
     EFFECT: reducing the distortions of the spherical wavefront reflected from the controlled surface and, correspondingly, increasing the dynamic range of the device operation, minimizing the root-mean-square error in measuring the curvature radius of the wavefront, and, accordingly, increasing the accuracy of determining the curvature radius of the controlled surface of the part. 
     4 cl, 1 dwg, 1 tbl