The Development Of High Precision Hartmann Wavefront Detector For Eye Aberration

Harmann wavefront has many advantages such as good real-time performance, easy operation, measuring wavefront slope easily and visual display wavefront distortion, so it is widely applied in many fields such as the laser beam quality diagnosis, optical components and optical system detection, atmospheric disturbances measurement, eye aberration measurement and adaptive optics etc.A hartmann wavefront detector for liquid crystal adaptive optics fundus imaging system is tried to deveop in the paper. Due to the reflection of each layer of the human eye tissue, causing the halo around the spot image; The different polarization characteristics as different place of the cornea, and using liquid crystal spatial light modulator as wavefront correctors in our laboratory, polarization light should be used to correct aberration, therefore light intensity distribution of Hartmann spot image is uneven when polarized. A new thresh algorithm of multimodal and point by point selection thresh is developed to solve above proplem in the paper. The light intensity with power algorithm is studied, and it is merged with the multimodal and point by point thresh selection thresh algorithm together to improve the precision of Hartmann wavefront detector to 1% pixels, and the corresponding PV value of the wavefont is less thanλ/40(λ=500nm). A dynamic tracking centroid detection algorithm is developed to solve the problem of the large eye aberration detection, which expand the dynamic range of Hartmann wavefront detector only by software means without loss of accuracy and increasing the detection time and is also applicable to the atmospheric turbulence measurement. The influence of the microlens arrangement for the centroid detection precision of Hartmann wavefront detector is analyzed, and the reconstruction error the variation of the eye pupil size leads to is analyzed, and the dynamic wavefront reconstruction algorithm is developed to solve above problem. According to the symmetry of the Zernike mode, optimizing the GPU program and decreasing the time of the wavefront reconstruction. The development Hartmann wavefront detector is used in the experiment of adaptive optics retina imaging, and the three microns retinal image of the diffraction limit is obtained.The precision is improved and the dynamic range is expanded of Hartman wavefront detector by software means, and without additional costs, so it has a good application prospect.