Ning Ling

Fitting capability of deformable mirror

Deformable mirror is the key element for adaptive optical wavefront correction. The number of actuators decides the complexity and cost of adaptive optical system. In this paper computer simulations of wavefront error for fitting different Zernike terms by deformable mirror with different number of actuators are presented. The arrangement of actuator and the influence function of mirror are discussed in respect of fitting error. The minimum number of actuators for fitting different Zernike orders of wavefront are given. Some optical experiments of fitting capability have been done with 19 and 37-element deformable mirrors and a Zygo interferometer.

Small table-top adaptive optical systems for human retinal imaging

Two generations of adaptive optical system for human retina imaging have been developed. The wavefront correcting elements are small PZT 19 and 37 element deformable mirrors (DM) with novel structure. The diameters of these DMs are 24 and 50mm respectively. By using these DMs, the size of whole optical system are rather small and can be fit on table. These systems are successfully used to correct the aberrations of living human eye. High-resolution images of microscopic structure in the scale of single photo-receptor cell and capillary in the human retina have been obtained by real-time correction of adaptive optical systems.

Second harmonic generation of beams with aberrations

Numerical studies of second-harmonic generation of beams with aberrations based on the solution of three-dimensional propagation equations including diffraction and walk-off effects are reported. Because of aberrations of the fundamental wave, the refractive index of an extraordinary wave, the phase-mismatch angle, etc. will vary across the aperture, and results of these studies show that these variations can lead to changes in conversion efficiency, transverse intensity distribution, and phase distortion of the second-harmonic beam. The second-moment radius and the divergent angle of a second-harmonic beam are presented. It has been found that second-harmonic beams are less divergent than fundamental waves, but the M-2 factor can be either worse or better. The calculated results of different orders of Zernike aberrations are given

Adaptive optical system for ICF application

An adaptive optical system has been built for improving optical beam quality in a new inertial confinement fusion (ICF) system. This system is designed to compensate the static and dynamic wavefront errors in the laser generator and amplifier by pre-compensation manner, which includes a 45-channel deformable mirror, two Shack-Hartmann wavefront sensors with 10x10 sub-apertures, a 45-channel high voltage amplifier and a wavefront control computer. Preliminary principle experiment has been done and the experimental results are reported.

Progress on the 127-element adaptive optical system for 1.8m telescope

The 127-element adaptive optical system for the 1.8m astronomical telescope is being developed. In this system, the wavefront correction loop consists of a 127-element deformable mirror, a Hartmann-Shack (H-S) wavefront sensor, and a high-speed digital wavefront processor. The tracking system consists of a tip-tilt mirror, a tracking sensor and a tracking processor. The wavelength for the H-S wavefront sensor ranges from 400-700nm. The imaging observation wavelengths range from 700-1000nm and 1000-1700nm respectively. In this paper, the optical configuration of 1.8m telescope will be briefly introduced. The 127-element adaptive optical system is described in detailed. Furthermore, the preliminary performances and test results on the 127-element adaptive optical system is reported.

Experiments of high-resolution retinal imaging with adaptive optics

At the base of the early reported 19 element adaptive optical system for human retina imaging, a new adaptive optical system has been developed. The wavefront correction element is a newly developed 37 element deformable mirror. Some modifications have been adopted for easy operation. Experiments for different imaging wavelengths and axial positions were conducted. Mosaic pictures of photoreceptors and capillaries were obtained. This would be the most detailed image of capillary distribution cover ±3° by ±3° field around the fovea ever reported. Normal and abnormal eyes of different ages have been inspected. Some preliminary very early diagnosis experiment has been tried in laboratory. This system is being planned to move to the hospital for clinic experiments.

Performance on the 61-element upgraded adaptive optical system for 1.2-m telescope of the Yunnan Observatory

The 61-element upgraded adaptive optical system for the 1.2m telescope of Yannan Observatory for astronomical observation had been in operation since May 2004. In this paper, the 61-element upgraded adaptive optical system for 1.2m telescope of Yunnan Observatory will be briefly described. The performance on the 61-element upgraded adaptive optical system is analyzed. Furthermore, the observational results for the stars will be presented.

Medical and industrial application of adaptive optics in Institute of Optics and Electronics, Chinese Academy of Sciences

In 1980, the first laboratory on Adaptive Optics in China was established in Institute of Optics and Electronics, Chinese Academy of Sciences. Several adaptive optical systems had been set up and applied in Inertial Confinement Fusion (ICF) and retinal high-resolution imaging. In 1985, the first adaptive optical system for ICF equipment was set up in the world. Another 45 element adaptive optical system was first built for correcting the static and dynamic wavefront aberrations existed in the large-aperture Nd: glass laser for inertial confinement fusion in 2001. Two set adaptive optical system with 19-element and 37-element deformable mirror had been developed for human retina imaging in 2000 and 2002 respectively. In this paper, the function and performance of these adaptive optical systems are described and the experiment results are presented.

Applications of Hartmann-Shack wavefront sensors

Hartmann-Shack wavefront sensors[1] are widely used in adaptive optical systems. It can measure the spatial-temporal errors of dynamic wavefront. Not only the phase but also the amplitude of a wavefront can be measured. Unlike an interferometer, it is not necessary to have a real-time reference beam, so it can work in a disturbing environment. Besides used in adaptive optics systems, Hartmann-Shack wavefront sensors also become a powerful tool in two fields: light beam diagnosis and optical testing of optical components and systems. We have developed a serial of Hartmann-Shack wavefront sensors used in these two fields. In this presentation, various applications of Hartmann-Shack wavefront sensors in these fields will be reported.

21-element infrared adaptive optics system at 2.16-m telescope

A 21-element adaptive optics system installed at the 2.16m telescope of Beijing Astronomical Observatory has been in operation. It is made up of a pair of shearing interferometer (SI), a 21-element deformable mirror, a fast steering mirror, a digital wavefront processor, a precise tracking subsystem and a PtSi IR CCD camera. In this paper the performance of the system will be briefly introduced. Its observation results in IR K band and in visible band are reported. For the system, 0.25 arcsec resolution has been achieved in IR K band, which approaches the diffraction limit of the 2.16m aperture. In visible band, 0.13arcsec resolution has been also achieved. For the star of magnitude 9.m2, the compensation of the system is still effective. The error rejection bandwidth of the system can be adjusted in the range from 5Hz to 40Hz according to the beacon magnitude and the strength of the atmospheric turbulence.