Michael Kovalev

A combination of computer-generated Fourier holograms and light guide substrates with diffractive optical elements for optical display and sighting system

A combination of computer-generated Fourier holograms (CGFH) and light guide substrate with diffractive optical elements (DOE) is described. The experimental results show that this combination can be used in display and sighting systems.

Investigation of Computer-Generated Fresnel Holograms for Wavefront Sensors

The possibility of using computer-generated Fresnel holograms to determine phase aberrations of a wavefront is studied. The results of computer simulation of the propagation of an elementary signal based on the Fresnel integral transform are presented. The principle of operation of a hologram for a wavefront sensor is discussed.

Wave front sensor based on holographic optical elements

A wavefront sensor (WFS) based on holographic optical elements, namely computer generated Fourier holograms is proposed as a perspective alternative to the Shack-Hartmann sensor. A possibility of single and multimode sensor and the dependence of their characteristics were investigated.

Discrete Representation of Holograms of Halftone Objects

A comparative analysis of methods for calculating digital holograms based on discrete transformations for various types of objects is presented. Qualitative results of synthesis and reconstruction of holograms are obtained, as well as examples of the realization of some of the types of holograms considered. The quality of digital hologram recovery is estimated by calculation of signal-tonoise ratio (SNR) and root-mean-square error (RMSE).

Fourier holography in holographic optical sensors

Many areas of optical science and technology require fast and accurate measurement of the radiation wavefront shape. Today there are known a lot of wavefront sensor (WFS) techniques, and their number is growing up. The last years have brought a growing interest in several schematics of WFS, employing the holography principles and holographic optical elements (HOE). Some of these devices are just the improved versions of the standard and most popular Shack-Hartman WFS, while other are based on the intrinsic features of HOE.

Optical position encoder based on structured head diffraction grating

Optical position encoders working according to the interference method consists of a measurement scale and a measuring head moving along each other. The scale has a reflection diffraction grating on its surface and the measuring head has a transmission diffraction grating with same period inside. Laser light passing and diffracting through these two gratings creates an interference signal on an optical detector. Decoding of the interference signal phase allows to determinate current position. Known optical position encoders use complex optical schemes and some phase optical elements to form several quadrature signals with different phase for higher encoder accuracy. Previously we researched such kind of schemes [1, 2]. In this paper we propose to use a common optical scheme without phase elements but with a complex structured measuring head grating for this purpose to simplify an optical scheme and alignment requirements. The optical scheme of position encoder based on measuring head grating with specific structure is research and described in this paper.

Method of accounting errors in the production of computer-generated Fourier holograms during their synthesis

In this paper, we describe and analyze the distortions that occur in the production of Fourier holograms by the projection method using SLM and in a printed way. Mathematical simulation of projection method allowed to take into account the influence of diffraction on apertures on the structure of the obtained hologram. It is shown that the final structure after recording and the simulation result are similar. When analyzing the printed method of obtaining holograms, we took into account the distortions that arise due to incorrect consideration of the resolution of the printer and the wrong choice of the size of the printed hologram Numerical results of simulation and holograms reconstruction are obtained.

Recent progress in holographic wavefront sensing

Many areas of optical science and technology require fast and accurate measurement of the radiation wavefront shape. Today there are known a lot of wavefront sensor (WFS) techniques, and their number is growing up. The last years have brought a growing interest in several schematics of WFS, employing the holography principles and holographic optical elements (HOE). Some of these devices are just the improved versions of the standard and most popular Shack-Hartman WFS, while other are based on the intrinsic features of HOE.