Study On Measurement Of Freeform Spectacle Lenses Based On Wavefront Aberration

The human eye is a delicate imaging system with various imaging defects due to physiological factors.Therefore,a variety of correction methods have been adopted to compensate the imaging defects of human eye,like spectacle lens,contact lens and laser-assisted subepithelial keratectomy(LASEK)among which wearing spectacle lens has the unique advantages of convenience,safety and low cost.A possible way of achieving supernomal vision with zero aberration on retinal image may be approached with the realization and development of wavefront aberration detection of human eye.At the same time,the wide application of freeform spectacle lenses which is mainly represented by progressive addition lens with suitable appearance and multi-vision correction functions has posed further demands and challenges to the existing spectacle lenses measurement methods.To evaluate the image quality of freeform spectacle lenses,a new method of measuring transmission wavefront aberration of spectacle lenses in real as-worn condition was proposed.The corresponding experimental measurement apparatus was designed and constructed.The experiments of measuring spectacle lenses were carried out.This thesis introduces the study as the following contents:1.Transmission wavefront aberration was captured by the Hartmann-Shack wavefront sensor and then decomposed by the Zernike polynomials to obtain each single aberration and power parameters.The defects of existing focimeter and wavefront measurement of spectacle lenses in real viewing condition were analyzed.Based on a spectacle lens plus eye model in real viewing condition,a new method of measuring transmission wavefront aberration of spectacle lenses in real as-worn condition was proposed,which could obtain ‘as-worn' wavefront aberration and ‘as-worn' power of spectacle lenses on corneal sphere by simulating the real as-worn condition.2.The corresponding experimental measurement apparatus was designed and built.The structures of light source module,lens module and sensor module were determined to ensure the ability of scanning and measuring lenses automatically and accurate position and orientation controlling of each module.The way that light source emitted to the lens was optimized to match the real viewing condition and the wavefront aberration on corneal sphere could precisely captured by Hartmann-Shack sensor with different as-worn conditions and different filed of views.The software was programmed to realize connection and controlling of each moving axis and Hartmann-Shack sensor and achieve the progress of scanning and measuring wavefront aberration of spectacle lens on its corneal sphere automatically under the personal as-worn conditions and pre-defined measuring parameters.3.Spherical single vision spectacle lens and freeform spectacle lens were measured by experimental measurement apparatus.The difference of measurement results between the vertex sphere and corneal sphere was analyzed and different measurement results on corneal sphere with the use of different regions of spectacle lens under the corresponding field of view were compared.As-worn conditions of spectacle lens were then introduced to find out its impact on image quality.The results of experiment verified the feasibility of measurement method proposed by this article and reliability of the measurement apparatus.