The role of wavelet transform in biometric system of verification or identification is shown. Fingerprints as an example of popular biometric feature have been chosen for analysis and the influence of Gabor wavelet with various scales on the quality of output signal in optical recognition processor is presented.
Design and manufacturing of diffractive optical elements (DOEs) are presented. Mass replication methods for DOEs are explained including UV-replication, micro-injection moulding and reel-to-reel production. Novel applications of diffractive optics including spectroscopic surface relief gratings, antireflection surfaces, infrared light rejection gratings, light incoupling into thin waveguides, and additive diffractive colour mixing are presented.
We describe several methods for optoelectronic processing of 3D images based in digital holography. In all cases, phase-shift digital holography is used to record the complex amplitude distribution associated to the diffraction field generated by 3D objects illuminated with coherent light. First, we review a technique to encrypt a 3D image by using digital holography. Encryption is performed by using random phase codes as key functions. In this way, it is possible to send secure 3D information through conventional digital communication lines. In our approach, decryption is carried out digitally. Next we describe both, digital and optical reconstruction of 3D images starting from digital holograms. Finally, we show how to perform 3D pattern recognition with high discrimination based in the above techniques. Experimental results are presented.
The Research and Technology Project FABIOLA (Fluorescence Applied to BIOLogical Agents Detection) is placed under the Common European Priority Area (CEPA) number 13 on "Radiological, chemical and biological defence" and managed by the Western European Armaments Organization (WEAO) in the frame of SOCRATE MOU (System of Co-operation for Research and Technology in Europe). The six (6) Nations: Finland, France, Greece, Italy, Poland and Sweden have decided to allocate funding to FABIOLA Research and Technology Project with France as the Lead Nation. There are two main objectives of the project : demonstrate the feasibility to improve the detection of BW agents using LIF (Laser Induced Fluorescence), and develop a BW early warning point detection lab-demonstrator based on LIF. The aim of the project is to evaluate the possibility of time-resolved fluorescence and conception of a system used for real-time measurements. It is well known that when bacteria are excited with UV radiation, they exhibit intense fluorescence emission. UV fluorescence is usually very good at discriminating bio from non-bio particle. Laser induced fluorescence is possible at several wavelength. For LIF system the laser source(s) should operate at excitation wavelength in the UV (250nm to 360nm) and the resulting fluorescence (300nm to 600nm) shall be detected with the aim to discriminate between bio-molecular materials (containing amino acids such as tryptophane, tyrosine, and phenylalanie, as well as cell nucleus compounds such as NADH and riboflavin).
Flame radiation intensity and its changes in time domain deliver the quickest and straight information of a combustion process. We have compared combustion of coal-biomass mixture and reference coal through flame image analysis. The aim of the research was finding flame's shape features, that could point to a state of unstable combustion, for the fuels being considered. Several combustion tests have been made in a laboratory stand for pulverized coal mixed with paper sludge (10%) with variable coal flow. The stand was equipped with scaled down (1:10) low-NOx burner. Flame images were recorded by a standard monochrome camera and captured by a frame grabber. After conversion to black-and-white images, changes of some shape parameters such as flame area, its horizontal and a vertical dimensions and shape coefficient have been investigated.
Non-chemical method of detection of sugar concentration in biological (animal and plant source) liquids has been investigated. Simplified set was build to show the easy way of carrying out the survey and to make easy to gather multiple measurements for error detecting and statistics. Method is suggested as easy and cheap alternative for chemical methods of measuring sugar concentration, but needing a lot effort to be made precise.
Human body posses many unique, singular features that are impossible to copy or forge. Nowadays, to establish and to ensure the public security requires specially designed devices and systems. Biometrics is a field of science and technology, exploiting human body characteristics for people recognition. It identifies the most characteristic and unique ones in order to design and construct systems capable to recognize people. In this paper some overview is given, presenting the achievements in biometrics. The verification and identification process is explained, along with the way of evaluation of biometric recognition systems. The most frequently human biometrics used in practice are shortly presented, including fingerprints, facial imaging (including thermal characteristic), hand geometry and iris patterns.
Detecting weapons concealed underneath clothing, analyzing the contents of suspicious-looking envelopes, or even spotting the onset of cancer: these are just some of the exciting prospects that have been turning terahertz wave research into one of the most important topics in photonics. Most broadband pulsed THz sources are based on the excitation of different materials with ultrashort laser pulses. So far, generation of tunable narrow-band THz radiation has been demonstrated using ultrafast solid state lasers as a source of high-intensity optical pulses. The lack of a high-power, low-cost, portable room-temperature THz source is the most significant limitation of modern THz systems. Advances in fiber laser technology can be used to further the capabilities of the homeland security. Using semiconductor saturable absorber mirrors allows for reliable mode-locked operation with different values of cavity dispersion in a broad spectrum ranged from 900 to 1600 nm. Semiconductor saturable absorbers mirrors have been used successfully to initiate and to sustain mode-locking in a wide range of core-pumped fiber lasers. The main advantage of the semiconductor saturable absorber mirrors (SESAM) is the possibility to control important parameters such as absorption recovery time, saturation fluence and modulation depth through the device design, growth conditions and post-growth processing. The SESAM as a cavity mirror in the fiber laser results in compact size, environmentally stable and simple ultrashort pulse lasers that can cover wide wavelength range and generate optical pulses with durations from picoseconds to femtoseconds. Employing SESAM technology for mode-locking, the double-clad fiber laser promises superior pulse quality, high stability and pulse energy without need for power booster that eventually degrades the pulse quality due to nonlinear distortions in the amplifier fiber.
We give an overview of recent achievements in ultrafast fiber lasers; discuss basic properties, technical challenges and methods to achieve stable short pulse operation with high average and peak powers from all-fiber devices. The important aspects of the mode-locked fiber lasers relevant to practical security systems are presented. Particularly, the effect of the amplified spontaneous emission (ASE) on the performance of the SESAMs in mode-locked fiber lasers has been investigated. We show that high level of ASE intensity typical for fiber lasers can saturate the absorption and degrade significantly the nonlinear response of the SESAM. We studied the effect of the absorber recovery time and demonstrated that the ion-irradiated SESAMs with fast nonlinear response are less affected by the ASE radiation and, consequently, in the presence of the high-power ASE they exhibit better self-starting capability compared with slow absorbers. The promising method for noise suppression based on the cavity-enhanced optical limiting is another important issue described. Optical limiting and saturable absorption are studied by placing two-photon absorption material and InGaAs quantum wells in a microcavity. We show that field enhancement that occurs in a cavity affects strongly the limiting threshold and dynamic range of roll-over in the nonlinear response.
To achieve energy levels sufficient for different security systems, power scaling technique should be employed. We present a stretched-pulse double-clad ytterbium-doped fiber laser mode-locked with SESAM. High modulation depth in the nonlinear response of the SESAM allows for self-starting pulse operation without any dispersion compensation in the laser cavity. The chirp on the output pulses is highly linear and can be compensated for with dispersion in photonic bandgap fiber. The results is a fully self-starting source of 150-fs pulse with 63-nJ of energy at a 8-MHz repetition rate.
Fibre optic have been using in security technology for 25 years. It started from simple systems where an alarm was generated only when a fibre (placed inside a fence, a net or a wire) was cut or broken. Now, there is a growing interest in research of sensors for disturbance localization. These sensors can be specially useful for perimeter security. In comparison with other sensors, they are passive, multikilometer-long devices and can be sensitive to variety of parameters. The fiber optic sensors with intruder localisation can be divided into three classes, that base on: interferometers, internal modes interference and Brillion scattering. In this paper, we will present our research of interferometer-based sensors as well as state of art of the other sensors.
Integrated optical distance measurement systems based on the Time-of-Flight (TOF) principle open up 3D vision for various applications like e.g. inspection systems. The introduced single pixel consists of both, a PIN photodiode and a signal-processing circuit on chip. Due to eye-safety reasons, the optical illumination power is limited (Popt<2mW). For diffuse reflecting objects in distances up to several meters, signal attenuation of about -50dB occurs with 1-inch optics. Therefore high responsivity of the photodiode is required: R=0.36A/W at 660nm. Resolutions of centimeters matter TOF far below 1ns, i.e. the photodiode has to feature high bandwidth (f3dB=1.35GHz). Distance information is gained by correlation between the modulated transmission signal and the run- ime delayed, attenuated received signal. The readout circuit consists of three stages: the first stage is a broadband current amplifier, realised with current mirrors. The correlation is performed in the second stage by a switching mixer. Amplification and smoothing is performed in the third, active integrator stage. The distance information is derived from the output signal by external sampling and simple data processing. A standard deviation of better than 1% (2%) for distances up to 2m (3.7m) is achieved for measurement durations of 10ms. The primary linearity error of less than 6cm is educed by error correction. The pixel has a fill factor of ~10%, including the overall pixel area of ~460µm×170µm and the photodiode with a diameter of 100µm. The chip was realised in a 0.6µm BiCMOS ASIC process.
In this paper, the application of the optical correlators for face thermograms recognition is described. The thermograms were colleted from 27 individuals. For each person 10 pictures in different conditions were recorded and the data base composed of 270 images was prepared. Two biometric systems based on joint transform correlator and 4f correlator were built. Each system was designed for realizing two various tasks: verification and identification. The recognition systems were tested and evaluated according to the Face Recognition Vendor Tests (FRVT).
We describe the application of nearly wavelength-independent optical processors to develop several broadband security techniques. Our achromatic optical configurations, based in the appropriate combination of a small number of diffractive and refractive lenses, are designed to work under temporally incoherent illumination. In this way, we are able to develop a method to reconstruct color Fourier holograms, an optical system to perform color pattern recognition and a technique to encrypt and decrypt color input objects, in all cases under white-light illumination. Moreover, we extend these ideas to work under both spatially and temporally incoherent illumination. This allows us to perform color pattern recognition and optical encryption techniques under natural light.
The last two decades have witnessed an exciting advanced research field that stems from non-classical atomic theory, quantum mechanics. This field promises an important applicability in secure data communications, known as quantum cryptography. Quantum cryptography takes advantage of the inherent random polarization state of single photons, which is not reproducible by a third party or an eavesdropper located between the source and the destination. Thus, when polarization states of photons are associated with binary logic an algorithm may intelligently developed according to which a cryptographic key is disseminated by the source terminal to the destination. This is a process known as quantum key distribution. However, as photons propagate in a non-linear medium such as fiber, their polarization state does not remain intact and thus the quantum key distribution and quantum cryptography becomes vulnerable to attacks. In this paper we consider the applicability of quantum cryptography in a pragmatic fiber-optic medium and in a popular communication network topology. We identify major weaknesses for each step of the quantum key distribution process, and also potential attacks to incapacitate quantum cryptography in fiber communications, so that better countermeasure strategies can be developed.
The work presents the encryption process in the optical arrangement with the Talbot array illuminator (TAIL). The object to be encrypted is multiplicated, forming a periodical structure. Then the obtained periodical structure is placed in an optical set-up with a TAIL. The encryption is based on the Fresnel diffraction behind the TAIL. The encrypted image has a form resembling an elementary cell of the amplitude sampling filter. The decryption is based on the Talbot effect.
Invented in late 1940s, holography has played a very important role in many technical applications. While the 60s and 70s belonged to, say, a classical period of the holography and diffractive optics (optical elements, lenses, beam splitters), the last two decades have shown an enormous expansion of various mainly synthetically designed and created holographic elements. Ever since its invention, holograms have also attracted our attention, because of their true three-dimension perception of a depicted object and related optical features. These phenomena caused, the holograms have become very well and easily publicly recognized, but still very difficult to falsify. Holography based optically variable microstructures and related advanced anti-counterfeit measures are thus ones of the leading features in security elements used for the protection against falsification of valuables, documents (banknotes, visa, passports, ID cards, tax stamps, etc.), serving for the protection of interests and many others.
Our talk deals with the survey of currently exploited technologies to produce several protective optical elements. A special attention will be paid to the synthetically developed special optical elements by means of the unique technology - the electron beam lithography, what is one of the world's most advanced technologies used for the protection against falsification. The computer-synthesized security elements are recorded with an incredible resolution of up to 500.000 dpi and are specially developed for the security of the most important state valuables and documents. Finally, we shall discuss some technological possibilities for its future development.
Results of researches of processes for forming visually observable identification elements on CD substrates are given. The opportunity of forming identification elements in an area of information block recording without data distortion is shown. The results of experimental researches on recording holographic identification elements on CD substrates are presented.
We propose to represent complex non-periodic deterministic multilayer nanostructures as numbers in base equal to the number of constituent layer types, e.g., binary numbers for binary multilayers. We have shown that such numbers have correlation with geometrical and spectral properties of nanostructures in question. Possible applications for number identification and information coding are discussed. Numbers corresponding to fractal multilayers (fractal numbers) are shown to possess distinct factorization properties, which can be applied in non-symmetric cryptography. Using multilayers as reverse engineering proof optical keys or embedded identification elements is also considered.
A combination of dielectric thin film and laser absorption dye technologies was introduced to fabricate a clear reflective aircrew's laser eye protection (LEP) visor. The interlayer and thin film layer materials for the high and low refractive indices are optimized. A clear visor with 26 % visibility was achieved for more than four optical densities (OD) LEP. In addition, an oxide compound film coating was explored to seek extra protection for the delaminating of the fragile multilayer dielectric thin film coating. As a side effect, applying surface-active agents on the oxide compound film resulted in good dustproof and anti-fog properties.
Proc. SPIE 5954, Nighttime activity of moving objects, their mapping and statistic making, on the example of applying thermal imaging and advanced image processing to the research of nocturnal mammals, 59540P (24 September 2005); https://doi.org/10.1117/12.621991
The paper presents method of acquiring a new form of statistical information about the changes at scenery, overseen by thermal imaging camera in static configuration. This type of imagers reach uniquely high efficiency during nighttime surveillance and targeting. The technical issue we have solved, resulted from the problem: how to verify the hypothesis that small, nocturnal rodents, like bank voles, use common paths inside their range and that they form a common, rather stable system? Such research has been especially difficult because the mentioned mammals are secretive, move with various speed and due to low contrast to their natural surroundings - as leaves or grass - nearly impossible for other kind of observations from a few meters distance. The main advantage of the elaborated method showed to be both adequately filtered long thermal movies for manual analyses, as well as auto-creation of the synthetic images which present maps of invisible paths and activity of their usage. Additional file with logs describing objects and their dislocations as the ".txt" files allows various, more detailed studies of animal behavior. The obtained results proved that this original method delivers a new, non-invasive, powerful and dynamic concept of solving various ecological problems. Creation of networks consisted of uncooled thermal imagers - of significantly increased availability - with data transmissions to digital centers allows to investigate of moving - particularly heat generated - objects in complete darkness, much wider and much more efficiently than up today. Thus, although our system was elaborated for ecological studies, a similar one can be considered as a tool for chosen tasks in the optical security areas.
We present a class of diffractive elements that can be used in medical applications. We describe their physical properties, in particular the point spread functions and modulation transfer functions. Our analyses consist of the detailed numerical simulations. The obtained results correspond to the different setup parameters and confirm usefulness of such structures in medical aspect, especially in presbyopia treatment.
We present an experiment on detection of nitrogen dioxide in free air using cavity enhanced spectroscopy. As a light source a blue pulsed diode laser was applied, while the output signal was detected with a photomultiplier. The absorber concentration was found by investigation of the optical resonator quality. It was done by determination of decay time of radiation pulse trapped in the cavity. Also the measurement of the phase shift between the output signal and modulation signal was used as the alternative method. The detection limit better than 1 ppb was demonstrated. The aim of this experiment was to study potential application of cavity enhanced absorption spectroscopy for construction of fully optoelectronic NO2 detector which could replace the commonly used chemical detectors.
In this work is explored the effectiveness of application of various absorption laser spectroscopy methods for definition of gas components concentration in boilers' smoke gases. O2 and CO absorption spectrums are parsed, optimum absorption lines in near IR spectrum range (about 0.76 microns for O2 and 1.56 microns for CO) are selected and graphics of selected lines intensities and half-widths dependences on the temperature of controllable medium and pressure in it are given. Processes of monitoring of CO and O2 content in boilers smoke gases are simulated at usage of basic laser spectroscopy methods (integral, differential, modulation, correlation, modified correlation) and measurement inaccuracies are analyzed. It is ascertained, that for a decrease of methodical errors of concentration measuring it is necessary to take into account operated medium temperature and pressure. It is shown, that the least inaccuracies of CO and O2 concentration continuous monitoring at the presence of dissipative losses variations are ensured with the modified correlation method though its threshold sensitivity is less, than integral and correlation ones.
The determination of the sequence of line crossings is still a current problem in the field of forensic documents examination. This paper presents the potentiality of the 3D micro-topography to resolve the writing order of signatures (if partially superimposed), to detect the tampering of manuscripts (if the added inscription superimposes itself on parts already written), to analyze pressure variation, and to identify strokes in handwritten. The system used, in this paper for creating 3D micro-topography, is based on conoscopic holography. It is a non-contact three-dimensional measuring system that allows producing holograms, even with incoherent light, with fringe periods that can be measured precisely to determine the exact distance to the point measured. This technique is suitable to obtain 3D micro-topography with high resolution also on surfaces with unevenness reflectivity (which is usual on the surface of the handwritten document). The proposed technique is able to obtained 3D profile in non-invading way. Therefore, the original draft do not be physically or chemically modified, allowing the possibility of multi-analysis in different time, also in case of forensic analysis with the necessity to preserving the original sample. The experiments performed with line crossings data base show that the proposed method is able of "positive identification" of writing sequence in the majority of the tests. When we have not had a positive identification, the result has been "inconclusive". The proposed technique, if correctly used, does not supply "false positive" or "probable" identifications. The possible results are only: "positive identification" and "inconclusive".
In this paper we propose a fragile marking system based on Computer Generated Hologram coding techniques, which is able to detect malicious tampering while tolerating some incidental distortions. A fragile watermark is a mark that is readily altered or destroyed when the host image is modified through a linear or nonlinear transformation. A fragile watermark monitors the integrity of the content of the image but not its numerical representation. Therefore the watermark is designed so that the integrity is proven if the content of the image has not been tampered. Since digital images can be altered or manipulated with ease, the ability to detect changes to digital images is very important for many applications such as news reporting, medical archiving, or legal usages. The proposed technique could be applied to Color Images as well as to Gray Scale ones. Using Computer Generated Hologram watermarking, the embedded mark could be easily recovered by means of a Fourier Transform. Due to this fact host image can be tampered and watermarked with the same holographic pattern. To avoid this possibility we have introduced an encryption method using a asymmetric Cryptography. The proposed schema is based on the knowledge of original mark from the Authentication
The appearance of elliptical polarization for linear polarized radiation reflected by plant leaves was investigated. The leaf cuticle reflectance model was proposed. The evaluation of refractive index and mean angle of cuticle roughness to leaf surface was carried out.
In this paper we present an automatic system for the on-line quality control of printed circuit boards. A line-scan camera permits the acquisition of a 550 mm wide image with a resolution up to 70 microns/pixel. The system detects the following type of errors: cuts and short circuits in tracks, stains, ink excess or faults, pores, omissions, "bites" and track narrowing. The input for the system are just the Gerber data files corresponding to the circuit to be analyzed. All the tolerances and precision factors can be modified directly from the user-friendly interface. For each analyzed board, the type of error detected and its location inside the circuit are indicated in the interface. For each set of analyzed circuits the system provides information for statistical control of the results.
Sensitivities of reflectance of two-material non-polarizing all-dielectric beamsplitter coatings on variations of the angle of incidence, refractive indices and thickness of layers were studied. Taking into account sensitivities and optical specifications, tolerance requirements for these parameters were estimated. Three types of coatings, for 0,2, 0,32 and 0,5 nominal reflectance at 45° incidence in air, were taken into consideration. Coatings were designed on the basis of a buffer layer and internal antireflection.
The initial optical design concerns the determination of the thin-component parameters based on the knowledge of ray coordinates, requirements and restrictions. The ground of the approach is heuristics that relies on an analysis of aims and means. The method may be used twice either as development of some new algorithms or the numerical computation of the optical thin-component model. In the first case, from the beginning we may select relations, and next establish the proper mathematical forms. In the second case we have been changing the introductory state influencing on results in this way. The methodological table plays an important role in this method. Different types of parameters are found in lines of this table while successive components are in columns. In this table we show in the initial state, methodology for applying relations in the right order and check for its correctness.
Computation for the riflescope illustrating possibilities, and advantages of the improved version is given in this paper.