Differential confocal combination ultra-long focal length measuring method and apparatus

Abstract

The invention belongs to the optical precise measurement technical field and relates to an ultra-long focal distance measuring method and a corresponding apparatus used for a differential confocal combined lens. The method firstly adopts the differential confocal focusing theory to respectively define the focus position of a reference lens and the focus position of the combination of measured lens and reference lens; then the distance delta between two focuses and the distance d<0> between two lenses are measured and then the formula is adopted to figure out the focal distance of the measured lens and the sensitivity for focal distance measurement can be simultaneously enhanced with the pupil filtering technique during the measuring process. The invention firstly puts forward the adoption of the features of the corresponding micro-lens focus while the differential confocal response curve passes the zero point so as to extend the differential confocal microscopy theory to the ultra-long focal distance measurement field and form the differential confocal focusing theory. The invention integrates the differential confocal focusing theory and the lens combination so as to get the advantages that the measurement precision is high and the anti-interference capability is strong. The invention can be applied to the detection for the lens with ultra-long focal distance and the high-precise focal distance measurement in the optical system assembling process.

Description

technical field [0001] The invention belongs to the technical field of optical precision measurement and can be used for the detection of ultra-long focal length lenses and the high-precision focal length measurement in the assembly process of optical systems. technical background [0002] In recent years, ultra-long focal length lenses have been widely used in large-scale optical systems such as high-energy lasers and astronomical telescopes. The processing, testing and assembly of such large-scale lenses are very difficult. As an important parameter of an ultra-long focal length lens, its focal length measurement has always been a difficult point in the field of optical measurement. The main factors are: small numerical aperture and long depth of focus make it difficult to achieve precise focusing; Susceptible to environmental disturbances. Due to the above reasons, traditional fixed-focus methods such as the magnification method or the pentaprism method are difficult to ...

AI Technical Summary

Problems solved by technology

[0007] The purpose of the present invention is to solve the problem of high-precision measurement of small numerical aperture and ultra-long focal length lenses, and propose a method that uses the characteristics of the target position corresponding to the focus of the microscopic objective lens when the differential confocal response curve crosses zero to achieve precise focusing

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