Home – Home – Jornals – Avtometriya 2017 number 5

The problems and the possibility of using diffractive elements with a sawtooth relief-phase microstructure in imaging optical systems are analyzed. Particular attention is paid to minimizing the negative adverse effect of diffraction orders on the quality of the image formed by an optical system with a diffractive element due to the transition from single-layer microstructures to structure containing several layers and reliefs. Requirements to the design parameters of the microstructure and operating conditions of the diffractive element in the optical system are formulated that ensure the absence of the visually observable halo due to adverse diffraction orders. A number of examples have shown that incorporation of a diffractive element in a plastic-lens imaging optical system corrects chromatic aberration and provides high resolution in the generated image.

This paper considers the features of the surface structure shapes of multifocal intraocular lenses (IOLs) which, unlike bifocal IOLs form additional foci or increase the depth of focus, which provides good vision not only near and far but also at intermediate distances. The field of clear vision is achieved on the basis of the effects of diffraction, interference, and refraction (change in the radius of curvature of the lens surface). The optical characteristics of the best-known multifocal IOLs (trifocal and quadrifocal lenses and lenses with an extended focal region) are given.

Manufacturing processes and design features of modern diffractive-refractive intraocular lenses are presented. The implantation of multifocal intraocular lenses is the most optimal method of restoring the accommodative function lost after removal of the lens. Diffractive-refractive intraocular lenses are the most widely used implantable multifocal lenses worldwide. Existing methods for manufacturing such lenses implement various design solutions to achieve the best visual measures after surgery. The variety of modern designs of diffractive-refractive Intraocular lenses reflects the demand for this method of vision correction in clinical practice and the importance of further applied research and the development of new technology solutions to design improved lens models.

An improved method of structural lighting for increasing the efficiency of inspection of the cylindrical object surface appearance is considered. The method is based on using a diffractive optical element to reduce the amount of recorded data due to illuminating the test object at an angle to the image recording plane, which is normal to the inspected surface. Implementation of the proposed method implies the use of several identical channels. For this reason, one channel is considered in the present study. Calculations of diffractive elements, a description of the experimental setup, and results of experiments aimed at determining the depth of surface defects on objects simulating fuel pellets and fuel elements are presented. Implementation of the investigated method with defect depth determination in industrial systems of inspection of fuel pellets and fuel elements is expected to improve the quality of the fuel for atomic power stations.

Various issues of creation of diffractive optical elements transforming one laser beam with small divergence to a matrix of converging beams with a diffraction size of focused spots in the plane of object illumination and their application for problems of DNA sequencing and microscopy are considered. The parameters of diffractive elements are calculated and optimized in the approximation of the Fresnel-Kirchhoff diffraction theory. Diffractive elements are fabricated by the method of direct laser writing on a photoresist by using a circular laser writing system. Experimental characteristics of a diffractive element creating a matrix consisting of 33 × 33 beams, which are focused in one plane at a distance of 210 mm, are presented. The degree of nonuniformity of beam intensities determined by the ratio of beam intensities in the central region to intensities of peripheral beams is 1/2.5, which is potentially sufficient to be used in DNA sequencing problems. The maximum distortions of spot positions in the entire focusing field is <0.15 %.

This paper describes a study of the optical methods of the formation of multilevel microrelief in the layers of a Gibrimer-TATS hybrid photopolymer material based on thiol-siloxane and acrylate oligomers. Halftone photolithography and direct laser recording are used to form multilevel structures 3.5 and 6 μm in height, respectively. The characteristic curves and photosensitivity of the material are determined. The process of preparation and treatment of the films is optimized, and it is discovered that the addition of the stages of pre- and post-exposure significantly affects the photosensitive properties of Gibrimer-TATS. The photopolymer is promising as a structural material for the formation of microstructured optical components.

This paper is a review of the studies carried out by the staff of the National Research University of Information Technologies, Mechanics and Optics (ITMO University, Saint-Petersburg) and the Institute of Automation and Electrometry of the Siberian Branch of the Russian Academy of Sciences (Novosibirsk) in the field of development of laser technogical processes for the formation of the structure of diffraction optical elements (DOEs) and photomasks with amplitude binary and semitone transmission. The paper also describes the results of the study of laser thermochemical technology for manufacturing chrome DOEs, technologies for the manufacture of halftone DOEs, and photomasks based on the use of amorphous silicon and LDW glass.

This paper presents a short analysis of papers devoted to the nonparaxial effects arising from the use of the lensacon proposed by Koronkevich with coworkers in 1993, as well as its analogs in a substantially nonparaxial mode. In this case, accounting for the vector character of electromagnetic radiation is required, allowing new effects to be detected, which, in turn, provides an additional impetus to expand the range of applications of the lensacon.

Results of investigations of diffraction phenomena on constant-thickness three-dimensional objects with plane internal surfaces (thick plates) are summarized on the basis of our constructive theory of their calculation as applied to dimensional inspection. It is based on diffraction models of 3D objects with the use of equivalent diaphragms (distributions), which allows the Kirchhoff-Fresnel approximation to be effectively used. In contrast to available rigorous and approximate methods, the present approach does not require cumbersome calculations; it is a clearly arranged method, which ensures sufficient accuracy for engineering applications. It is found that the fundamental diffraction parameter for 3D objects of constant thickness d is the critical diffraction angle _кр = √/ d at which the effect of three-dimensionality on the spectrum of the 3D object becomes appreciable. Calculated Fraunhofer diffraction patterns (spectra) and images of constant-thickness 3D objects with absolutely absorbing, absolutely reflecting, and gray internal faces are presented. It is demonstrated that selection of 3D object fragments can be performed by choosing an appropriate configuration of the wave illuminating the object (plane normal or oblique waves, spherical waves).

A comparative analysis of spatial variations in the energy characteristics of longitudinally polarized, extremely focused, needle laser beams generated by an optical system with selective thin-film transformation of the linear polarization of the beams into the radial one, followed by their subsequent spatial filtering and sharp ring focusing to subwave sizes. For the important special case of ideal radial polarization of a focused beam, longitudinal sections of spatial distributions of the electric energy density and the Poynting vector modulus in the vicinity of the focus were compared by numerical simulation. It is shown that the degree of their difference increases substantially with decreasing angular zone of ring focusing and with the introduction of space-frequency filtering. It is established that the dimensions of the axial zone of beam focusing determined for their central lobes in the first approximation do not depend on the energy characteristics in which they are measured.

This paper describes the development and manufacture of diffraction corrector and simulator for the interferometric control of the surface shape of the 6-m main mirror of the Big Azimuthal Telescope of the Russian Academy of Sciences. The effect of errors in manufacture and adjustment on the quality of the measurement wavefront is studied. The corrector is controlled with the use of an off-axis diffraction simulator operating in a reflection mode. The measured error is smaller than 0.0138λ(RMS).

This paper describes the interferometric method for controlling the assembly quality of a three-lens unit of an optical system of a non-centered nine-component optical system of an aircraft helmet wide-angle display collimator. It is shown that this adjustment method makes it possible to establish optical components, including the off-center aspherical lens, with an error of one micron. The method is contactless and allows for the control of the position of lenses inside the body of the device.

A review of advanced equipment for automated interference measurements developed at the All-Russian Research Institute for Optical and PHysical Measurements is given. Three types of interference microscopes based on the Linnik, Twyman-Green, and Fizeau interferometers with the use of the phase stepping method are presented.