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The application of Moiré effect for testing of a lithographic projection lens is reported. The arrangement presented allows measuring magnification, distortion, field curvature and telecentricity of the lens and can be used for its fine tuning. The method is based on two matched two-dimensional gratings, positioned in mutually conjugated planes; one of them can be translated. Visual interpretation of Moiré fringe pattern allows quick diagnostics of position errors exceeding critical dimension, whereas lateral scanning is applied for measuring of smaller magnitude errors. Field curvature and telecentricity are measured by 3D scanning. Presented results are in a good agreement with those obtained elsewhere., ImPhys/Optics

We describe a compact integrated module implementing a low-cost adaptive optics system. It is targeted as a correction system for small telescopes with primary mirror diameter up to 1 m, operating on a natural guide star with magnitude at least 4 (for a 25 cm telescope). It is supposed to provide stable diffraction-limited imaging of stars, double stars, planets and artificial bodies in various seeing conditions. Besides, it allows correcting for static aberrations of the telescope, observer’s ocular aberrations and fine adjustment of focus. The first on-sky tests have demonstrated closed-loop operation with correction for aberrations., Electrical Engineering, Mathematics and Computer Science

A novel liquid crystal (LC) wavefront corrector with smooth modal influence functions is proposed and realized. The device consists of a thin layer of planar aligned nematic LC sandwiched between a glass plate with a conductive electrode and a plate made of ceramic material with a very high dielectric constant. Control electrodes are positioned on the back side of the ceramic plate, opposite to the LC. The modal character of the response is determined by spreading of the electric field in the ceramic plate. The device implemented is operating in a reflective (mirror) mode; however, similar principles can be used to build a transmissive device. Low cost and simplicity of control make it a good alternative to continuous face-sheet deformable mirrors., Micro Electronics, Electrical Engineering, Mathematics and Computer Science

We present a prototype of an adaptive intraocular lens based on a modal liquid-crystal spatial phase modulator with wireless control. The modal corrector consists of a nematic liquid-crystal layer sandwiched between two glass substrates with transparent low- and high-ohmic electrodes, respectively. Adaptive correction of ocular aberrations is achieved by changing the amplitude and the frequency of the applied control voltage. The convex-shaped glass substrates provide the required initial focusing power of the lens. A loop antenna mounded on the rim of the lens delivers an amplitude-modulated radio-frequency control signal to the integrated rectifier circuit that drives the liquid-crystal modal corrector. In vitro measurements of a 5-mm clear aperture prototype with an initial focusing power of +12.5 diopter, remotely driven by a radio-frequency control unit at ~6 MHz, were carried out using a Shack-Hartmann wavefront sensor. The lens based on a 40-?m thick liquid-crystal layer allows for an adjustable defocus of 4 waves, i. e. an accommodation of ~2.51 dioptres at a wavelength of 534 nm, and correction of spherical aberration coefficient ranging from –0.8 to 0.67 waves. Frequency-switching technique was employed to increase the response speed and eliminate transient overshoots in aberration coefficients. The full-scale settling time of the adaptive modal corrector was measured to be ~4 s., Micro Electronics, Electrical Engineering, Mathematics and Computer Science

A reflective-type liquid crystal (LC) wavefront corrector with modal addressing is described. The corrector’s backplane has an array of pixel electrodes interconnected by a network of discrete resistors. The resistive network serves to form the local voltage profile that controls the phase distribution generated in the liquid crystal layer. This design is realized in a bipolar silicon technology. Preliminary numerical analysis is presented; technology and experimental results are discussed., Electronic Instrumentation Laboratory, Electrical Engineering, Mathematics and Computer Science

Liquid crystal (LC) wavefront correctors with modal addressing are described. Three different approaches are considered. The first one is based on a continuous thin-film resistive layer. This layer is used for forming of the local voltage profile that controls the phase distribution across the corrector’s aperture. The second approach is a modification of the first one, where the continuous resistive coating is replaced by a network of discrete resistors. It is based on silicon technology. The third approach makes use of distributed electric field in thick dielectric layers for forming of the modal response of an actuator. Technologies, methods of control and experimental results are discussed for each case., Electronic Instrumentation, Electrical Engineering, Mathematics and Computer Science

New applications of adaptive optics, especially in the potentially mass markets such as laser optics, imaging and medicine, require development of new components with high quality and low price. These requirements are equally applicable to wavefront sensors, wavefront reconstructors and wavefront correctors. The whole concept of adaptive optics as a science-intensive technology needs to be altered, to facilitate low-cost and service-free deployment and user-unaware exploitation. As an example of a technology, that has a good low-cost potential, we describe the technology of piezoelectric deformable mirrors with actuators based on the transversal piezoelectric effect, as an inexpensive alternative to the deformable mirrors with stacked actuators., Electronic Instrumentation, Electrical Engineering, Mathematics and Computer Science

We designed and built an experimental setup for subjective (manually controlled) correction of up to 12 orthogonal terms (excluding tilts and defocus) of the aberration of the human eye. In our experiments, the subject was looking through an adaptive optical system at the USAF resolution chart. By using the arrow keys of the computer keyboard, the subject was able to control the amplitudes of up to 12 orthogonal aberration terms, introduced by a deformable mirror, optically conjugated to the pupil of the eye. Preliminary statistical analysis on a group of 12 participants with 6 correction attempts per participant, demonstrated satisfactory correlation of aberration coefficients obtained by the same person in different correction attempts. The majority of the participants were able to improve the visual acuity by subjective optimization of the figure of the deformable mirror., Electronic Instrumentation, Electrical Engineering, Mathematics and Computer Science

We present an overview of the results of our recent research in the field of adaptive optical components based on silicon microtechnologies, including membrane deformable mirrors, spatial light modulators, liquid-crystal correctors, wavefront sensors, and both spherical and aspherical micro-optical components. We aim at the realization of adaptive optical systems using standard-technology solutions., Electronic Instrumentation Laboratory, Electrical Engineering, Mathematics and Computer Science