Jiang Wen-han

Hybrid deconvolution of adaptive optics retinal images from wavefront sensing

Adaptive optics can be used to compensate for the wave aberration of the human eyes to achieve high-resolution imaging in real time. However the correction is partial due to the limitation of hardware. We propose a kind of hybrid image post-processing method, which uses the blind deconvolution combined with the residual data in wavefront sensor to restore the partially adaptive optics corrected retinal image. This method is applied in the image restoration of the vivid human retinal images. The results show that it is effective to improve the retinal image quality.

Thermal stability test and analysis of a 20-actuator bimorph deformable mirror

One of the important characteristic of adaptive mirrors is the thermal stability of surface flatness. In this paper, the thermal stability from 13 degrees C to 25 degrees C of a 20-actuator bimorph deformable mirror is tested by a Shack-Hartmann wavefront sensor. Experimental results show that, the surface P-V of bimorph increases nearly linearly with ambient temperature. The ratio is 0.11 mu m/degrees C and the major component of surface displacement is defocused, compared with which, astigmatism, coma and spherical aberration contribute very small. Besides, a finite element model is built up to analyse the influence of thickness, thermal expansion coefficient and Youngs modulus of materials on thermal stability. Calculated results show that bimorph has the best thermal stability when the materials have the same thermal expansion coefficient. And when the thickness ratio of glass to PZT is 3 and Youngs modulus ratio is approximately 0.4, the surface instability behaviour of the bimorph manifests itself most severely.

Effects of Different Zernike Terms on Optical Quality and Vision of Human Eyes

The visual quality of human eyes is much restricted by high-order aberrations as well as low-order aberrations (defocus and astigmatism), but each term of high-order aberrations contributes differently. The visual acuity and contrast of the image on the retina can be gained by inducing aberrations to each term of high orders. Based on an adaptive optics system, the visual acuity of four subjects is tested by inducing aberrations to each Zernike term after correcting all the aberrations of the subjects. Zernike terms near the center of the Zernike tree affect visual quality more than those near the edge both theoretically and experimentally, and 0.1-mu m aberration of these terms can clearly degrade the optical quality and vision. The results suggest that correcting the terms near the center of Zernike tree can improve the visual quality effectively in practice.

Overview of adaptive optics development

自适应光学(AO)是校正动态光学波前误差的技术。本文概述了近50年来AO的发展历程，包括发展初期，“星球大战”期间美国的发展，以及在地基高分辨力成像望远镜，激光系统(特别是惯性约束聚变)以及眼科等方面的应用，此外还给出AO的发展趋势。通过引用每一项技术发展，首创者的首篇文献，给出了比较清晰的发展脉络。