Research On The Measurement System Of New Centering Instrument Based On Liquid Lenses

Optical surface centering error is one of the common errors in optical lenses processing and systems assembly process.The amount of centering error directly affects the imaging quality of optical lenses.Therefore,lenses centering error measurement and systems centering assembly are the indispensable key links in the manufacturing technology of high-precision optical lenses.The centering instruments can measure the centering error of the optical surface,provide data support and centering error correction datum for centering assembly,and it is an important equipment in optical workshop.Its measurement accuracy and ease of use are important evaluation indicators of the equipment.This paper makes use of the displacement-free zoom ability of the liquid lens to conduct in-depth research in the direction of optical centering measurement,which has certain engineering value.In the reflection laser measurement method,when the traditional centering instrument images the center of curvature of the measured surface out of focus,the measurement range is limited by the focal length of the standard lens,and a standard lens with appropriate focal length parameters should be selected according to the curvature radius of the measured lens,and adjusted to the determined working distance,which is inconvenient to operate.To solve this problem,a new centering instrument scheme based on liquid lens was proposed in this paper.The characteristics of the focal length of the system can be changed by using the liquid lens without moving optical components,under the condition of setting the initial value of the working distance,the focal length can be matched with the radius of curvature of the measured lens,the working distance does not change during the measurement,no need to change lenses and quick focus,and it is easy to realize the automatic control of the optical centering measurement.The centering system designed in this paper uses two liquid lenses,one to adjust the back focus and the other to compensate for the image plane shift.According to the radius of curvature and axial position distribution of the lens group to be measured,determine the centering probe to the appropriate working distance and then fix it.By adjusting the focal length value can make the measurement mode and position of the measurement points of the system conform to the surface parameters of each lens.The system can not only solve the problem of limited working distance of the defocus imaging mode at the curvature center of the measured surface("Unilateral" mode),but also improve the measurement resolution of the defocus imaging mode at the vertex of the measured surface("Bilateral" mode).The theoretical calculation and simulation results show that the resolution of the designed system is better than 0.5?m,and the measurement range of the lens surface curvature radius is-??-2mm and+2mm?+?.The main research work in this paper includes:1.The measurement methods of centering error were reviewed,the development and research status of centering instruments at home and abroad were introduced,and the kinds,principles and applications of liquid lenses were investigated.By comparing the various centering error measurement methods and the strengths and weaknesses of various measurement optical structures,a new optical centering measurement method and the overall scheme of the system were proposed combined with the characteristics of liquid lens.2.Based on the reflective laser measurement method,the mathematical model of centering error of the measured optical lens with multiple lenses was established.According to the orbit diameter on the detector plane and the lateral amplification of decentration in the"Unilateral" or "Bilateral" measurement mode,the size and direction of centering error of each optical surface in the measured optical lens can be calculated3.The measurement principles of the switching lens method,zoom method and focus method studied earlier in this paper were explained.The optical structure design and image quality evaluation of the three methods were completed,and the characteristics of the three optical centering measurement methods were compared4.The design scheme for measurement optical structure of centering instrument based on liquid lenses was mainly introduced,the optical simulation model was given,and the relationship between key parameters in the optical model was analyzed.Through a simulation example of centering assembly of an optical lens with known structural parameters,the feasibility of realizing optical centering measurement method based on liquid lenses-based zooming of displacement-free components was verified.