• Journal of the Optical Society of Korea
• /
• v.19 no.5
• /
• pp.521-530
• /
• 2015

Active optics is a key technology for future large-aperture space telescopes. In the design of deformable mirrors for space applications, the design parameter trade-off between the number of regularly configured actuators and the correction capability is essential but rarely analyzed, due to the lack of design legacy. This paper presents a parametric module method for integrated modeling of deformable mirrors with regularly configured actuators. A full design parameter space is explored to evaluate the correction capability and the mass of deformable mirrors, using an autoconstructed finite-element parametric modeling method that utilizes manual finite-element meshing for complex structures. These results are used to provide design guidelines for deformable mirrors. The integrated modeling method presented here can be used for future applied optics projects.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.2435-2439
• /
• 2005

In case of visual sensing systems with multiple mirrors, systematic errors need to be reduced by the system calibration and the mirror position adjustment in order to enhance system measurement accuracy. In this paper, a self calibration method is presented for a visual sensing system designed to measure the three-dimensional information in deformable peg-in-hole tasks. It is composed of a CCD camera and a series of mirrors including two pyramidal mirrors. By using an image of the inner pyramidal mirror taken by the system, the error parameters of the inner pyramidal mirror could be calibrated or adjusted. Also the influence of the plane mirrors is investigated.

• Smart Structures and Systems
• /
• v.21 no.6
• /
• pp.777-791
• /
• 2018

This paper discusses the shape control of deformable mirrors for Adaptive Optics in the dynamic range. The phenomenon of control-structure interaction appears when the mirror becomes large, lowering the natural frequencies $f_i$, and the control bandwidth $f_c$ increases to improve the performance, so that the condition $f_c{\ll}f_i$ is no longer satisfied. In this case, the control system tends to amplify the response of the flexible modes and the system may become unstable. The main parameters controlling the phenomenon are the frequency ratio $f_c/f_i$ and the structural damping ${\zeta}$. Robustness tests are developed which allow to evaluate a lower bound of the stability margin. Various passive and active strategies for damping augmentation are proposed and tested in simulation.

• ETRI Journal
• /
• v.29 no.6
• /
• pp.817-819
• /
• 2007

A low-stress organic polymer membrane is proposed as a deformable mirror that can be incorporated into a cellular phone camera to achieve auto focusing without motor-type moving parts. It is demonstrated that our fabricated device has an optical power of 20 diopters and can switch focus in 14 ms. The surface roughness of the organic membrane is measured around 15 nm, less than ${\lambda}$/20 of the visible light. With curve fitting, we found that the actuated membrane is almost parabolic in shape, which leads to less aberration than spherical surfaces. It is suitable for reflective-optics systems.

• The Bulletin of The Korean Astronomical Society
• /
• v.36 no.2
• /
• pp.132.2-132.2
• /
• 2011

We are developing Adaptive Optics (AO) system for astronomical use. The He-Ne laser works as an artificial light source. The tip-tilt correction servo is added to our AO system. The tip-tilt term, among the Zernike terms, is the biggest contributor of wavefront deformation caused by atmospheric turbulence at small telescopes. The tip-tilt correction servo consists of a Piezo tip-tilt platform with a mirror, a quadrant photodiode as a tip-tilt sensor, and controllers. The Shack-Hartmann wavefront sensor measures the residual wavefront errors and they are corrected by the MEMS (Micro Electro Mechanical System) deformable mirror. The MEMS deformable mirror allows the compact size at low cost compare to adaptive secondary mirror and other deformable mirrors. As the frame rates of the MEMS deformable mirror is about tens of kHz, the frame rates of the detector in wavefront sensor is the bottleneck of the wavefront correction speed. For faster performance, we replaced a CCD which provides frame rates only 70 Hz with a CMOS with frame rates up to 450 Hz.

• Proceedings of the Optical Society of Korea Conference
• /
• 2000.08a
• /
• pp.3-3
• /
• 2000

Adaptive Optical (AO) technology can compensate for wave-front errors in real-time to improve image and beam quality. The research and development on AO in China began in 1979. In 1980, the first laboratory on AO in China was established in Institute of Optics and Electronics (IOE), Chinese Academy of Sciences (CAS). Since then several AO systems have been built in this Laboratory. The 19-element system is the first AO system in the world ever used in inertial confinement fusion (ICF) facility in our knowledge. It corrects the static error of this large laser engineering. The 21-element system was firstly tested at the 1.2m telescope of Kunming Observatory in 1990 and then up-dated as an IR AO system installed at the 2.16m telescope of Beijing Observatory. The 37-element system was used with a turbulence cell in Laboratory on Atmospheric Optics in Hefei to conduct elementary research on Atmospheric Optics. The 61-element system for astronomical observation is newly developed. It has been successfully installed at the 1.2m telescope of Kunming Observatory and a laser guide star system will be integrated with the system. A compact AO system using our newly developed miniature DM for high resolution ophthalmic imaging of retina is also being built. The key elements of these AO systems, deformable mirrors and fast-steering mirrors, are all developed in this Laboratory. In this talk, the main configurations of these AO systems, some test results as well as the specifications of these active mirrors will be presented.

• Journal of Korea Game Society
• /
• v.7 no.1
• /
• pp.31-42
• /
• 2007

In the natural world, most materials such as skin, marble and cloth are translucent. Their appearance is smooth and soft compared with metals or mirrors. In this paper, we propose a new GPU based hierarchical rendering technique for translucent materials, based on the dipole diffusion approximation, at interactive rates. Information of incident light, position, normal, and irradiance, on the surfaces are stored into 2D textures by rendering from a primary light view. Huge numbers of pixel photons are clustered into quad-tree image pyramids. Each pixel, we select clusters (sets of photons), and then we approximate multiple subsurface scattering term with the clusters. We also introduce a novel hierarchical screen-space interpolation technique by exploiting spatial coherence with early-z culling on the GPU. We also build image pyramids of the screen using mipmap and pixel shader. Each pixel of the pyramids is stores position, normal and spatial similarity of children pixels. If a pixel's the similarity is high, we render the pixel and interpolate the pixel to multiple pixels. Result images show that our method can interactively render deformable translucent objects by approximating hundreds of thousand photons with only hundreds clusters without any preprocessing. We use an image-space approach for entire process on the GPU, thus our method is less dependent to scene complexity.