Direct imaging of exoplanets by reflected starlight is extremely challenging due to the large luminosity ratio to the primary star. Wave-front control is a critical technique to attenuate the speckle noise in order to achieve an extremely high contras . . .

Wavefront sensing from multiple focal plane images is a promising technique for high-contrast imaging systems. However, the wavefront error of an optics system can be properly reconstructed only when it is very small. This paper presents an iterative . . .

We propose a transmission-filter coronagraph for direct imaging of Jupiter-like exoplanets with ground-based telescopes. The coronagraph is based on a transmission filter that consists of finite number of transmission steps. A discrete optimization al . . .

Image Rotation and Subtraction (IRS) is a high-contrast imaging technique that can be used to suppress the speckle noise and facilitate the direct detection of exoplanets. IRS is different from Angular Differential Imaging (ADI), in that it will subtr . . .

We present a novel "spectral subtraction algorithm" (SSA) technique to remove speckle noise. It consists of a low-order and a high-order SSA and is based on a three-dimensional image spectroscopy in which the three-dimensional data cube is available a . . .

Characterization of day-time atmospheric turbulence profiles up to 30 km above the telescope is crucial for designs and performance estimations of future solar multiconjugate adaptive optics (MCAO) systems. Recently, the S-DIMM+ method has been succes . . .

The high-contrast coronagraph for direct imaging earth-like exoplanet at the visible needs a contrast of 10^-10 at a small angular separation of 4Y/D or less. Here we report our recent laboratory experiment that is close to the limits. The test of the . . .

Using an optical vortex coronagraph (OVC) is one of the most promising techniques for directly imaging exoplanets because of its small inner working angle and high throughput. This paper presents the design and laboratory demonstration performance of . . .

Almost all high-contrast imaging coronagraphs proposed until now are based on passive coronagraph optical components. That is, the coronagraph cannot be actively controlled to be optimized for best performance. Pupil apodizing, which modifies the ligh . . .

The light reflected from planets is polarized mainly due to Rayleigh scattering, but starlight is normally unpolarized. Thus it provides an approach to enhance the imaging contrast by inducing the imaging polarimetry technique. In this paper, we propo . . .

Solar-adaptive optics (AO) are more challenging than nighttime AO, in some aspects. A portable solar adaptive optics (PSAO) system featuring compact physical size, low cost, and good performance has been proposed and developed. PSAO can serve as a vis . . .

High-contrast imaging provided by a coronagraph is critical for the direction imaging of the Earth-like planet orbiting its bright parent star. A major limitation for such direct imaging is the speckle noise that is induced from the wave-front error o . . .

Solar conventional adaptive optics (CAO) with one deformable-mirror uses a small field-of-view (FOV) for wave-front sensing, which yields a small corrected FOV for high-resolution imaging. Solar activities occur in a two-dimensional extended FOV and s . . .

An adaptive optics (AO) system based on stochastic parallel gradient descent (SPGD) algorithm is proposed to reduce the speckle noises in the optical system of stellar coronagraph in order to further improve the contrast. The principle of SPGD algorit . . .

A prototype of a multiway fibre bundle connector for astronomical applications is described. The connector provides for connection and disconnection in the fiber trains that feed an astronomical spectrograph. It also provides the more important functi . . .

We propose a coronagraph for direct imaging of Earth‐like planets orbiting nearby bright stars. The coronagraph is based on an apodization pupil composed of two stepped‐transmission filters. We show that the coronagraph can achieve 10−10 high‐contrast . . .

Multi-conjugate adaptive optics (MCAO) can considerably extend the corrected field of view with respect to classical adaptive optics, which will benefit solar observation in many aspects. In solar MCAO, the Sun structure is utilized to provide multipl . . .

We propose a coronagraph for direct imaging of Earth‐like planets orbiting nearby bright stars. The coronagraph is based on an apodization pupil composed of two stepped‐transmission filters. We show that the coronagraph can achieve 10−10 high‐contrast . . .

A method based on the Herzberger approach has been investigated for the selection of glasses for the apochromatic correction at near-infrared (NIR) wavelength. The method avoids the algebraic complexity and simplifies the glass selection processes. Do . . .

Polarimetry plays an important role in the measurement of solar magnetic fields. We developed a high-sensitivity and high-accuracy polarimeter (HHP) based on nematic liquid crystal variable retarders (LCVRs), which has a compact setup and no mechanica . . .

Future ground-based direct imaging of exoplanets depends critically on high-contrast coronagraph and wave-front manipulation. A coronagraph is designed to remove most of the unaberrated starlight. Because of the wave-front error, which is inherit from . . .

We propose a high-contrast coronagraph for direct imaging of young Jupiter-like planets orbiting nearby bright stars. The coronagraph employs a step-transmission filter in which the intensity is apodized with a finite number of steps with identical tr . . .

We propose a multiconjugate adaptive optics (MCAO) system called pupil-transformation MCAO (PT-MCAO) for solar high-angular resolution imaging over a large field of view. The PT-MCAO, consisting of two deformable mirrors (DMs), uses a Shack-Hartmann w . . .