Equipment for 2-D profile measuring of aspheric microscope condenser in mass production

摘要

This paper deals with the measurement of aspherics on surfaces of microscope condenser in mass production. The aspheric surface in microscope condenser is a kind of optical surface working under very large numerical aperture and small field of view. To fulfill Kohler illumination for the microscope condenser, the aspheric surface must be fabricated as well as designed capable of projecting an image of the source, large enough to fill the sub stage condenser of the microscope. For larger numerical aperture condenser fabrication, it is crucial to guarantee a reasonable aspheric profile for spherical aberration compensation and even illumination. Here we established the equipment for microscope condenser aspheric profile measuring in mass production. The industry microscope is reconstructed to image the profile, with LED panel light source for even backlighting. The profile, captured with a high resolution CCD, is processed. It can be compared with theoretic aspheric profile directly or interpolated with a predefined polynomial. In this method, supports for aspheric lens fabrication and measurement are designed and employed on the industry microscope. It guaranteed that a table of points can accurately describe the profile of the aspheric surface, introducing less assembling error. Measurement with this method has proved satisfactory for certain high aperture microscope condenser at low cost. For systems requiring still higher accuracy, the CCD resolution may have to be increased and interpolation method optimized accordingly but the online aspheric testing equipment with proper supports could surely improve the accuracy of aspheric surface fabrication at low cost.