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The manufacturing of optical components introduces varying surface errors with diverse impact to the optical performance. In this paper we propose a measurement technique to detect form and mid-spatial-frequency errors of specular freeform surfaces. Results from simulation and experimental measurements are presented. The aim of a manufacturer of optical components is to produce its products as precise as possible according to the given parameters of the designer. However, errors due to the manufacturing process are not avoidable. Regarding surface deviations, one distinguishes between form deviations, mid-spatial-frequency errors and roughness. The proposed measurement technique in this paper is able to detect form and mid-spatial-frequency errors in one measurement. Therefore, the investigated surface is scanned with a single laser beam. The direction if the reflected beam is measured using Experimental Ray Tracing. From the direction of the incident and the reflected beam, the surface gradient at the investigated position can be determined. Proper integration methods lead to the reconstruction of the surface. Knowing the model of the investigated optical components, the form deviations and the mid-spatial-frequency errors can be calculated. Considering the model as unknown, the mid-spatial frequency-errors can still be determined, by separating the mid-spatial-frequency components from the low-frequency form information of the reconstructed surface. In this paper we propose a measurement technique for the measurement of form and mid-spatial-frequency errors of specular freeform surfaces. The measurement principle as well as results from simulation and experimental measurements of freeform surfaces are shown and evaluated.
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