Research on Magnetic Fluid Based Optical Deformable Mirrors with Fluid Mechanics

Magnetic fluid based liquid mirrors represent a promising technology. Compared with the conventional solid mirrors, magnetic fluid deformable mirrors (MFDMs) have the advantages of large strokes, low cost and easy scalability. In this paper, the brief history of the development of MFDMs was first introduced, the working principle of MFDMs with fluid mechanics and electromagnetic field was presented next and then the advantages of MFDMs as well as their challenges are discussed.

Reflective Liquid-Like Films of Silver Nanoparticles

Reflective liquid-like films of silver nanoparticles simultaneously have metallic luster and the macroscopic properties of a fluid. Owing to their special properties, the films can be potential materials for the component of a new kind of liquid mirrors. The influence of different sizes of nanoparticles on the films reflectivity has been considered in this study. A great improvement on the reflectivity of the films has been found with the increase in the silver nanoparticles’ size. Additionally, the volume of the liquid substrate also has an effect on the reflectivity of the films. Characterization of the films by X-ray diffraction indicates that the liquid-like films are mainly composed of fcc silver nanoparticles rather than silver compounds.

ESAD Shearing Deflectometry: A Primary Flatness Standard with Sub-Nanometer Uncertainty

To overcome the limitations of conventional interferometry, a technique has been developed which allows the absolute topography measurement of near-plane and slightly curved optical surfaces of arbitrary size with low measurement uncertainty. The Extended Shear Angle Difference (ESAD) method combines deflectometric and shearing techniques in a unique way to minimize measurement errors and to optimize measurand traceability. A device for the topography measurement of optical surfaces up to 500 mm in diameter, achieving sub-nanometer repeatability, reproducibility and uncertainty, was built at the Physikalisch-Technische Bundesanstalt (PTB). The ESAD method is optimally suited for creating a primary standard for straightness and flatness with highest accuracy by which the three-flat test or liquid mirrors can be replaced as starting points of the traceability chain in flatness measurement. In the following, the improved ESAD device which uses optimized opto-mechanical components is presented. Central aspects of the proper design and use of deflectometric systems are highlighted, including the optimal use of pentaprisms.