Adaptive cross-correlation detector for signals of optoelectronic reflective sensors

A soft- and hardware realization of optoelectronic intellectual sensor for biomedical noninvasive studies based on the analysis of light reflected from living tissues has been described. The main feature of the developed model is use of an adaptive crosscorrelation detector controlled by the digital signal processor. Algorithms and operating mode of detector are defined by the type of particular problem to be solved and conditions of measurements. The proposed model was tested to identify dynamic signals in the following areas: pulsometer, evaluation variability of the cardial rhythm, evaluation of blood saturation by oxygen

Is there any future of optical discs?

Considered in this paper are causes for cutting compact discs out of information technology market. It has been shown a search of new technological solutions for efficient use of CDs in archive data storage

High-speed optical recording in vitreous chalcogenide thin films

Thin films of glassy chalcogenide semiconductor are widely used as recording media in optical data storage. To obtain relief micro- and nanoscale structures on the surface of optical master discs inorganic photoresists based on chalcogenide glassy semiconductors can be used. They have high resolution and allow for exposure by short laser pulses. Implementation of such exposure is promoted by increasing the speed of photostructural transformations at high powers of exposing radiation. This increase in the sensitivity is associated with both local heating by illumination and a high density of excited electron-hole pairs. The exposure mode of the inorganic photoresists based on glassy chalcogenide semiconductor pulses of 10⁻⁸-10⁻⁹ s is close to the threshold of local photothermal destruction. Significant impact on the value of the threshold of photothermal destruction effects the choice of the substrate material which determines the rate of heat removal from the irradiation area. Moreover, one also needs to consider the effect of pulsed annealing of the inorganic photoresist material on the process of selective etching. We have established an inversion of the selective etching of the inorganic negative photoresist based on As₂S₃ in the center of the irradiated zone. The diameter of this zone is about 20% of the diameter of exposing beam. After the selective etching in alkaline solution in the center of protrusions being formed on the substrate, there observed are some dimples with the depth of 30-50 nm. Prior to the processing of irradiated inorganic photoresist by the selective etching these dimples were absent and their appearance is not due to possible local material evaporation of the inorganic photoresist. A possible reason for the inversion of solubility of the inorganic photoresist could be pulsed annealing in the recording process

Perspectives for using technology of laser thermolithography

Analyzed in this work are the requirements to an optical system for laser thermolithographic recording. It has been shown that possibilities of this type recording with decreasing the registered element sizes can be realized only when using special measures for stabilizing both exposing radiation power and duration of laser pulses. Using the thermolithographic method for making super-dense patterns also requires creation of a specific system for dynamic focusing with accuracy better than 100 nm. It has been shown that the specific heat of thermochemical reaction and thermal resistance of a substrate are critical parameters for this method

The new approach to identification of film reflecting holographic marks

The new approach for creation of film reflecting holographic marks for optical security is proposed. Such marks are replicas of a reflecting master hologram recorded on a chalcogenide glass layer. To receive the master hologram, the joint power spectrum of a reference phase mask and an input phase mask or a transformed phase mask is produced at the plane of the hologram writing and is modulated by an inclined laser beam. If an inclined laser beam illuminates the replica recorded on a flexible substrate, phase noise including speckle noise is eliminated because the hologram carrier frequency exceeds greatly the limiting frequency of the phase noise power spectrum. Experimental results have shown the principal possibility to produce the high performance film reflecting holographic marks for security applications. The proposed approach can be combined with technologies for fabrication of rainbow holograms. In this case, the received rainbow holograms are the reflecting holographic marks simultaneously. Therefore, they can be verified not only visually, but also by means of automatic identification

Analysis of properties of optical carriers after long-term storage

Performed in this paper is the analysis of possibilities to create optical information carriers for long-term information storage. Adduced are the results of experimental investigations of properties inherent to optical carriers of the WORM type after 25-year storage. It has been shown that their micro-relief structure formed by using focused laser radiation on thin films of chalcogenide vitreous semiconductors had not been practically changed after storing them for the above mentioned period in non-heated areas

Multilevel computer-generated holograms for reconstructing 3-D images in combined optical-digital security devices

Computer-generated holograms (CGHs) integrated within combined optical-digital security devices (CO/DSDs) are described in this work. They can restore the monochrome and color 3D images in white light. To record them, the Electron Beam Lithography (EBL) is used. Our investigations on optimization of synthesis and recording the CO/DSDs with the integrated in it multilevel CGHs of 3D images possessed horizontal parallax only (HPO) are presented here. The CGH fabrication process is mainly composed of two parts: calculation of the interferogram data (ID) and their recording. Calculation of the ID is done as follows: firstly, the geometrical and optical constants of recording scheme and the object surface represented by the elemental self-radiating areas, are determined, secondly, the basic parameters accounting for discretization of ID in hologram plane is defined. The ID values can be derived by calculation of the necessary elemental object areas bipolar intensities sum. Next, over suitable quantization of ID, recording the rectangle data appropriate for EBL onto glass coated with non-organic photoresist based on As₄₀S₄₀Se₂₀ is performed. We have also investigated reciprocal influence of an optical part of the CO/DSD and a digital one

The influence of obtaining and heat treatment conditions on the structure of As₂S₃-SbSI system

(As₂S₃)₁₀₀₋x(SbSI)x (x = 80 and 90) glasses were prepared by cooling homogenized melts from 720…750 K in cold water. Their structure and structural changes under heat treatment of glasses are confirmed by studies of micro-Raman scattering and X-ray diffraction. In the matrix of these glasses, we observed SbSI nanocrystalline inclusions. It has been shown that the sizes of crystalline inclusions are dependent on the heat treatment regimes

Photo-thermoinduced changes of transmission spectra of As₄₀-xSbxS₆₀ amorphous layers

The results of investigation of the As₄₀-xSbxS₆₀ (x = 0-10) thin films transmission spectra depending on exposure and heat treatment conditions are given. It was established that illumination and annealing of films leads to the absorption edge shift into the longwave spectral region. The values of pseudogap width Eg are determined. Optical characteristic changes of films are caused by photo-thermostructural transformations taking place in them under irradiation and annealing