Optoelectronics, Instrumentation and Data Processing (v.53, #5)

Diffractive elements for imaging optical systems by A. I. Antonov; G. I. Greisukh; E. G. Ezhov; S. A. Stepanov (421-430).
The problems and prospects of using diffractive elements with a sawtooth relief-phase microstructure in imaging optical systems are analyzed. Particular attention is paid to minimizing the adverse side effect of diffraction orders on the quality of the image formed by an optical system with a diffractive element due to the change-over from single-layer microstructures to structures containing several layers and reliefs. Requirements are formulated for the design parameters of the microstructure and operating conditions of diffractive elements in optical systems that ensure no visible halo caused by adverse diffraction orders. It is shown by a number of examples that the use of a diffractive element in a plastic-lens imaging optical system corrects chromatic aberrations and provides high resolution in the generated image.
Keywords: diffractive optical element; sawtooth relief-phase microstructure; imaging optical system; diffraction efficiency; optical image quality

Unfortunately, there were some misprints, which we want to correct.Unfortunately, there were some misprints, which we want to correct.Unfortunately, there were some misprints, which we want to correct.Unfortunately, there were some misprints, which we want to correct.This paper considers shape features of the surface structures of multifocal intraocular lenses (IOLs), which, unlike bifocal IOLs, generate additional foci or extends the depth of focus, which not only corrects near and far vision but also provides good vision at intermediate distances. Expansion of the field of clear vision is achieved due to the effects of diffraction, interference, and refraction (change in the radius of curvature of the lens surface). The optical characteristics of the most famous multifocal IOLs (trifocal and quadrafocal lenses and lenses with extended focal area) are given.
Keywords: diffractive-refractive lens; multifocal; trifocal; and quadrafocal intraocular lenses; lenses with extended focal area

Manufacturing methods and design features of modern diffractive-refractive intraocular lenses are discussed. The implantation of multifocal intraocular lenses is the most optimal method of restoring the accommodative ability of the eye after removal of the natural 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 provide the best vision function after surgery. The wide variety of available diffractive-refractive intraocular lens designs reflects the demand for this method of vision correction in clinical practice and the importance of further applied research and development of new technologies for designing improved lens models.
Keywords: diffractive-refractive intraocular lens; multifocal lens; eye lens; accommodative function; vision correction; implantation

Application of diffractive elements for improving the efficiency of systems for cylindrical surface inspection by P. S. Zavyalov; V. E. Karlin; M. S. Kravchenko; L. V. Finogenov; D. R. Khakimov (450-456).
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.
Keywords: inspection system; defect depth determination; diffractive optical element; light ring; cylindrical object

Diffractive focusing fan-out element for the parallel DNA sequencer by V. P. Bessmeltsev; P. S. Zavyalov; V. P. Korolkov; R. K. Nasyrov; V. S. Terentyev (457-465).
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%.
Keywords: diffractive optical element; diffractive focusing fan-out element; parallel sequencer; direct laser writing on a photoresist

This paper describes a study of the optical methods for fabrication of multilevel profile in the layers of a Hybrimer-TATS hybrid photopolymer material based on thiol-siloxane and acrylate oligomers. Grayscale photolithography and direct laser writing are used to form multilevel structures 3.5 and 6 μ in height, respectively. The characteristic curves and photosensitivity of the material are determined. The film preparation and treatment processes are optimized, and it is determined that addition of the stages of pre- and post-exposure significantly affects the photosensitive properties of Hybrimer-TATS. The photopolymer is promising as a structural material for the formation of microstructured optical components.
Keywords: hybrid photopolymer; thiol-siloxane-acrylate oligomers; laser writing; photolithography; multilevel diffractive structures; characteristic curve

Laser technologies in micro-optics. Part 1. Fabrication of diffractive optical elements and photomasks with amplitude transmission by V. P. Veiko; V. P. Korolkov; A. G. Poleshchuk; D. A. Sinev; E. A. Shakhno (474-483).
This paper is a review of 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 (IAE SB RAS, Novosibirsk) in the field of development of laser engineering processes for the formation of the structure of diffractive optical elements (DOEs) and photomasks with amplitude binary and grayscale transmission. This paper also describes the results of the study of laser thermochemical technology for fabricating chrome DOEs and technologies for the fabrication of grayscale DOEs and photomasks based on the use of amorphous silicon and LDW glass.
Keywords: laser technology; thermochemistry; laser writing; amorphous silicon; LDW glass; grayscale photomasks

Nonparaxial effects in lensacon optical systems by N. L. Kazanskiy; S. N. Khonina (484-493).
This paper presents a brief overview of papers dealing with the nonparaxial effects arising from the use of the lensacon proposed by Koronkevich and coauthors in 1993, as well as its analogs in a substantially nonparaxial mode. In this case, it is necessary to take into account the vector nature of electromagnetic radiation. This allows detecting new effects, which, in turn, would extend the range of applications of the lensacon.
Keywords: lensacon; nonparaxial mode; overcoming diffraction limit; conical focal domain; fractional axicon; modal and polarization transformations

Results of investigations of diffraction phenomena on constant-thickness three-dimensional objects with flat inner 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 allow 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 $${ heta _{cr}} = sqrt {lambda /d} $$ θ c r = λ / 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 inclined waves, spherical waves).
Keywords: diffraction; light interference; Fourier optics; spectra and images of 3D objects

A comparative analysis is made of spatial variations in the energy characteristics of tightly focused, longitudinally polarized needle laser beams generated by an optical system with selective thin-film linear-to-radial polarization conversion, followed by their spatial filtering and tightannular focusing to subwavelength sizes. For the important special case of ideal radial polarization of a focused beam, longitudinal cross-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 annular focusing and with the introduction of spatial-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 choice of energy characteristics used for their measurements.
Keywords: vector theory of wave diffraction; electric energy density; light energy flux; needle beams; radial polarization; longitudinal polarization

This paper describes the development and manufacture of diffraction corrector and imitator 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 imitator operating in a reflection mode. The measured error is smaller than 0.0138λ (RMS).
Keywords: diffraction optics; interferometry; aspheric optics control

This paper describes the interferometric method for controlling the assembly quality of a three-lens unit of an optical system of a decentered nine-component optical system of an aircraft helmet wide-angle display collimator. It is shown that this alignment 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.
Keywords: interferometer; diffraction; optics; alignment; optical control

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.
Keywords: interferometer; Linnik interferometer; interference microscope; phase stepping method