Compared with the original vibration mode shape, the crack location can be identified easily. Multiple image encryption based on known-plaintext attack and modified G-S phase retrieval algorithm Author s : Sudheesh K. Rajput; Naveen K. Nishchal Show Abstract. We propose a novel multiple image encryption based on fractional Fourier transform FRT and known-plaintext attack with modified Gerchberg-Saxton G-S phase retrieval algorithm.
Multiple images to be encrypted are encoded into corresponding phase-only masks POMs using modified G-S algorithm. The individual keys can be generated with the help of all the POMs. Now a random intensity image is encrypted using double phase encoding in which POM and random phase masks RPM are used as keys. For decryption, with the concept of known-plaintext attack using intensity image and RPM as keys, the POM is obtained. We present simulation results with four different gray-scale images. Numerical simulation results support the proposed idea of the multiple image encryption.
A variable-focus cylindrical liquid lens array based on two transparent liquids of different refractive index is demonstrated. An elastic membrane divides a transparent reservoir into two chambers. The two chambers are filled with liquid 1 and liquid 2, respectively, which are of different refractive index. The micro-clapboards help liquid 1, liquid 2 and the elastic membrane form a cylindrical lens array. Driving these two liquids to flow can change the shape of the elastic membrane as well as the focal length. In this design, the gravity effect of liquid can be overcome.
A demo lens array of positive optical power is developed and tested. Moreover, a potential application of the proposed lens array for autostereoscopic 3D displays is emphasized. Balajee; D. Roy Mahapatra ; G. Hegde Show Abstract. We present a mathematical modelling and analysis of reflection grating etched Si AFM cantilever deflections under different loading conditions. A simple analysis of the effect of grating structures on cantilever deflection is carried out with emphasis on optimizing the beam and gratings such that maximum amount of diffracted light remains within the detector area.
The digital image correlation DIC method has been well recognized as a simple, accurate and efficient method for mechanical behavior evaluation. However, very few researches have concentrated on the relationship between the characteristics of the camera lens and the measurement error of the DIC method. The modulation transfer function MTF has commonly used for evaluation of the resolution capability of camera lens.
In practice, when the DIC method is used, it is possible that the captured images become too blur to analyze when the object is out of the focus of the camera lens or the object deviates from the line-of-view of the camera. In this paper, the traditional MTF calibration specimen was replaced by a pre-arranged speckle pattern on the specimen.
For DIC images grabbed from several selected locations both approaching and departing from the focus of the camera lens, corresponding MTF curves were obtained from the pre-arranged speckle pattern. In a wavefront sensing system, the raw data for surface reconstruction, either the slope matrix or curvature matrix, is obtained through centroiding on the focal spot images. Centroiding is to calculate the first moment within a certain area of interest, which encloses the focal spot.
As the distribution of focal spots is correlated to the surface sampling condition, while a uniform rectangular grid is good enough to register all the focal spots of a uniformly sampled near flat surface, the focal spots of aspherical or freeform surfaces have varying shapes and sizes depending on the surface geometry.
In this case, the normal registration method is not applicable. This paper proposed a dynamic focal spots registration algorithm to automatically analyze the image, identify and register every focal spot for centroiding at one go. Through experiment on a freeform surface with polynomial coefficients up to 10 th order, the feasibility and effectiveness of the proposed algorithm is proved.
With the development of manufacturing industry, the in-situ 3D measurement for the machining workpieces in CNC machine tools is regarded as the new trend of efficient measurement. We introduce a 3D measurement system based on the stereovision and phase-shifting method combined with CNC machine tools, which can measure 3D profile of the machining workpieces between the key machining processes. The measurement system utilizes the method of high dynamic range fringe acquisition to solve the problem of saturation induced by specular lights reflected from shiny surfaces such as aluminum alloy workpiece or titanium alloy workpiece.
We measured two workpieces of aluminum alloy on the CNC machine tools to demonstrate the effectiveness of the developed measurement system. In this paper, a multi-camera DIC system with semi-circular configuration which can capture images from three different view angles at the same time is introduced. A cracked cylindrical were reconstructed with images obtained by the proposed three-camera systems, with the help of digital image correlation method is also demonstrated and discussed.
An experimental analysis of the real contact area between an electrical contact and a glass plane Author s : Michael Down ; Liudi Jiang; John W. The exact contact between two rough surfaces is usually estimated using statistical mathematics and surface analysis before and after contact has occurred. To date the majority of real contact and loaded surfaces has been theoretical or by numerical analyses.
A method of analysing real contact area under various loads, by utilizing a con-contact laser surface profiler, allows direct measurement of contact area and deformation in terms of contact force and plane displacement between two surfaces. A laser performs a scan through a transparent flat side supported in a fixed position above the base. A test contact, mounted atop a spring and force sensor, and a screw support which moves into contact with the transparent surface. This paper presents the analysis of real contact area of various surfaces under various loads.
The surfaces analysed are a pair of Au coated hemispherical contacts, one is a used Au to Au coated multi-walled carbon nanotubes surface, from a MEMS relay application, the other a new contact surface of the same configuration. The availability of high resolution CCD and CMOS sensors together with the increasing computer capacity have enabled the development of different interferometrical techniques speckle interferometry, digital holography, digital sherography which are well suited for real time measurements.
Two or more interferograms are recorded on a digital sensor at different times and the deformation of the object occurring between the exposures is calculated from the phase change. Since the process to investigate can be very fast we cannot use the well-known temporal phase shift method for the determination of the phase but we use a spatial carrier method which allows to determine that phase from one single hologram.
We will show that this method can be used as well for shearography. Applications of digital holographic techniques for the investigation of vibrations, defect detection in mechanical structure and time resolved measurement of deformation of microelectromechanical systems MEMS are presented together with some investigation of mechanical structures by using digital shearography with spatial carrier. The measurement of the rotating object is of great significance in engineering applications.
In this study, a high-speed dual camera system based on 3D digital image correlation has been developed in order to monitor the rotation status of the wind turbine blades. The system allows sequential images acquired at a rate of frames per second fps. An improved Newton-Raphson algorithm has been proposed which enables detection movement including large rotation and translation in subpixel precision. The simulation experiments showed that this algorithm is robust to identify the movement if the rotation angle is less than 16 degrees between the adjacent images.
The subpixel precision is equivalent to the normal NR algorithm, i. As a laboratory research, the high speed camera system was used to measure the movement of the wind turbine model which was driven by an electric fan. The blade was coated with randomly distributed speckles and 7 locations in the blade along the radial direction were selected. The displacement components of these 7 locations were measured with the proposed method. Conclusion is drawn that the proposed DIC algorithm is suitable for large rotation detection, and the high-speed dual camera system is a promising, economic method in health diagnose of wind turbine blades.
Some discussion on high-speed-imaging-based optical coherent measurement Author s : Y. Yan; C. Yang ; H. Miao Show Abstract. Optical coherent detection is a precise and non-contact method for measurement of tiny deformation or movement of an object. In the last century, it can only be used on the static or quasi-static measurement of deformation between two statuses. Recently it has been applied on dynamic measurement with the help of high-speed camera.
The advantage of this technique is that it can offer a full-field measurement. However, due to the limited capturing rate of high-speed camera, its capability in temporal domain cannot meet the requirements of many applications. In this study, several issues in high-speed-camera-based optical interferometry are discussed.
For example, introduction of carrier in temporal and spatial domain, signal processing in temporal-frequency domain, and the introduction of dual-wavelength interferometry in dynamic measurement. The discussion leads to a clue to select suitable technique to fulfill whole-field dynamic measurement at different ranges.
A phase-stepped white light ellipsometer Author s : Lionel R. Watkins Show Abstract. We demonstrate our new instrument experimentally by measuring the retardation of an achromatic waveleplate and determining the thickness of silicon dioxide films on a silicon substrate. One-dimensional surface profile measurement by detection of reflecting direction of a scanned laser beam Author s : Osami Sasaki ; Ryo Shinozaki; Takamasa Suzuki Show Abstract. A laser beam is scanned on an object surface with a fast scanning system which consists of a rotating mirror, a flat mirror, and a concave spherical mirror.
Propagation direction of the laser beam reflected by a sample surface is detected with a lens and a position sensitive detector. A one-dimensional surface profile of the sample surface is measured by integrating a slop distribution obtained from the propagation direction of the reflected beam. The measurement is insensitivity to mechanical vibrations because of a high-speed scanning of a few milliseconds. The required positioning accuracy of the sample surface is lower than a few millimeters. The measurement repeatability is less than 10 nm.
Full-field displacement measurement by double symmetrical illumination through reflection holograms Author s : V. Sainov ; A. Baldjiev ; E. Stoykova Show Abstract. Phase stepping is introduced simply by precise increments of the diode lasers current. Photovoltaic PV cells, or solar cells, take advantage of the photoelectric effect to convert solar energy to electricity. With rapidly increasing of demands of new and green energy, solar energy industry becomes more important in the global economic development.
PV cells are the building blocks of all PV systems because they are the devices that convert sunlight to electricity. Characterization and performance testing are critical to the development of existing and emerging photovoltaic technologies and the growth of the solar industry. As new solar products are being developed and manufactured, the energy conversion efficiency and other critical parameters must be accurately measured and tested under globally recognized standard testing conditions which include solar cell temperature, spectral distribution and total irradiance level of solar radiation on the cell to be tested.
The aim of this paper is to investigate one of critical parameters — solar cell temperature effect on measurement of spectral responsivity of the cell. When a reference solar cell is illuminated by solar radiation, the cell temperature will vary with different irradiance levels. Consequently it will affect the accurate measurement of spectral responsivity of the cell. In order to better understand the temperature effect on the measurement, temperature coefficients of reference solar cell in spectral range from nm to nm are measured in temperature range from 25 oC to 35 oC.
Over the years, numerous attempts have been made to fabricate these molds using various approaches such as lithography, FIB, laser ablation, and precision diamond turning. Amongst these approaches, diamond turning is by far the most commonly used method to generate the micropatterned rollers for roll-to-roll fabricating of precision optical parts such as BEF and 3D films. However, micro-burrs are frequently produced during the micro-cutting process which not only makes the mold un-usable but also increases the cost of machining.
Efforts have been made to study the burr formation process during the micro-cutting by FEM simulation, micro-scratching and diamond turning. Influences of the machining parameters such as rake angle, cutting edge radius, included angle and cutting speed on the burr formation were systematically investigated. The results showed that i tool rake angle, included angle and cutting edge radius have profound effect on burr formation and achievable surface finish, ii simulation can supply very useful information for setting the machining parameters to suppress the burr formation during micro-cutting process.
The generation of microstructures by ultrashort pulse laser irradiation is - depending on process parameters and the applied material - often accompanied with the creation of substructures like ripples or micro canals on the ablation ground. This side effect can be used to create local topographic modifications on a microscopic scale which can change functional properties of the surface.
The combination of micro structuring and functionalisation within one production step can only be successful if the interaction mechanisms are well known. In this study the options to modify the wetting behavior on stainless steel, Al 2 O 3 ceramic and PMMA plastic were analyzed. Therefore the contact angles of water drops on picoseconds-laser-produced samples were measured by a self-made measuring system. Test measurements offered post-process effects on surfaces of steel and ceramic. On those substrates the final contact angle adjusts after several hours up to days.
This allows generation of hydrophilic up to super-hydrophobic effects on precise defined areas. The combination technique offers novel options particularly for micro fluidic. Chan ; S. Lin; Y. Zou; C. Chen; T. Liu; C. Chen; H. Wang Show Abstract. Simulations were conducted to evaluate the performance of the proposed system and study effects of system parameters on the limitation of the proposed system.
The traditional monitoring ways have some disadvantages, which are difficulties in obtaining data of the cavity, monitoring the unmanned cavity and calculating volume of the cavity accurately. To solve these problems, this paper describes how to develop a high precision 3D laser scanning system, which enables scanning the cavity rapidly, obtaining the same resolution point cloud, calculating volume of the cavity, marking the deformation area correctly and providing visualized environment.
At the same time, this device has realized remote control functionality to avoid people to work on the underground. State of the art of compact optical 3D profile measurement apparatuses: from outer surface to inner surface measurement Author s : Toru Yoshizawa ; Toshitaka Wakayama Show Abstract.
This paper is not an original paper, but a review paper passed on our previous papers. However, in surface profile measurement, conventional systems have several short comings including being very large in size and heavy in weight. Therefore we propose to realize a compact portable apparatus on the basis of pattern projection method using a single MEMS mirror scanning. On the other hand, in the case of inner profile measurement for pipes or tubes, we propose to use optical section method by means of disk beam produced by a conical mirror.
We introduce the state of the art of these systems including commercialized products for practical purpose. Three-dimensional 3-D shape measuring techniques, using a combination of grating projection and a most frequently used mathematical tool--Fourier fringe analysis, have been deeply researched and increasing in numbers. Such kind techniques are based on the idea of projecting and superposing a carrier fringe pattern onto the surface of the tested object, and then reconstructing its corresponding 3-D shape from the deformed fringe pattern modulated by the height of the tested object and captured by a camera from other view direction.
This paper mainly reviews the basic principles and its typical applications of the combined technology based on grating projection and Fourier fringe analysis that we have developed over past ten years in the research field of dynamic 3-D shape measurement. Meanwhile, the advantages and challenges of this technique and the current development of real-time measurement in this research filed are also described as a discussion and conclusion in this paper.
Holography, in which three-dimensional 3D information and texture of object is encoded with interference fringe is a promising approach for 3D display. However, it is challenge to make photographic hologram of living object. In addition, it is impossible to record scene combining real-existing objects with virtual ones using photographic holography. In this paper, we propose a method for capturing and displaying 3D real-existing scene. Firstly, the 3D shape and color texture of scene is captured with fringe projection method.
Secondly, the information of scene is encoded with computer generated fringe, which is called Computer-generated Hologram CGH. The real-color Rainbow-hologram is chosen for display static scene. Three Fresnel holograms corresponding to red, green and blue component of scene are adopted for display dynamic scene. The apparatuses for 3D capture and display are introduced and the experimental results are demonstrated. High-speed shape measurement is required to analysis the behavior of a breaking object, a vibrating object or a rotating object. A shape measurement by a phase shifting method can measure the shape with high spatial resolution because the coordinates can be obtained pixel by pixel.
The key-device is a grating projector. The projector can shift the projected grating in high-speed. So, authors proposed a light source stepping method using a linear LED device. A grating projector is composed with the linear LED and a Ronchi ruling. Grating pattern can be projected when the linear LED is turned on. The phase of the projected grating on the object can be shifted with changing the position of lighted linear LED easily and quickly.
Authors call this method a light source stepping method. In this paper, a linear LED grating projector is developed. The characteristic of the linear LED grating projector such as the wavelength, directional characteristics, response are evaluated. The results show that this projector is useful for high-speed shape measurement. The three-dimensional 3D metrology for specular reflecting surfaces attracted much attention due to their various applications in optics, electronics, or semiconductor industry.
Fringe reflection technique is an effective tool to measure the specular surface slopes gradient information , and then reconstruct the surface shape from gradient. The performance of the compact specular 3D shape measurement system is demonstrated with experiments. In phase measuring deflectometry PMD , the fringe pattern deformed according to slope deviation of a specular surface is digitized employing a phase-shift technique.
Without height-angle ambiguity, carrier-removal process is adopted to evaluate the variation of surface slope from phase distribution when a quasi-plane is measured. This paper investigates nonlinear carrier components introduced by the generalized imaging process in PMD and the nonlinear carrier removal methods. To remove the nonlinear carrier components in PMD, the reference subtraction technique, series-expansion technique and Zernike polynomials which are normally used in fringe projection profilometry are analyzed on accuracy, processing time and experimental simplicity.
The theoretical analysis and the experiment results show that the new technique is accurate, simple and time-saving. Pattern recognition by using joint transform correlator with JPEG-compressed reference images is studied. Human face and fingerprint images are used as test scenes with different spatial frequency contents.
Recognition performance is quantitatively measured by taking into account effect of imbalance illumination and noise presence. The feasibility of implementing the proposed JTC is verified by using computer simulations and experiments. Ensemble of hybrid genetic algorithm for two-dimensional phase unwrapping Author s : D. Balakrishnan ; C. Quan ; C. Tay Show Abstract. The phase unwrapping is the final and trickiest step in any phase retrieval technique. Phase unwrapping by artificial intelligence methods optimization algorithms such as hybrid genetic algorithm, reverse simulated annealing, particle swarm optimization, minimum cost matching showed better results than conventional phase unwrapping methods.
In this paper, Ensemble of hybrid genetic algorithm with parallel populations is proposed to solve the branch-cut phase unwrapping problem. In a single populated hybrid genetic algorithm, the selection, cross-over and mutation operators are applied to obtain new population in every generation. The parameters and choice of operators will affect the performance of the hybrid genetic algorithm. The ensemble of hybrid genetic algorithm will facilitate to have different parameters set and different choice of operators simultaneously. Each population will use different set of parameters and the offspring of each population will compete against the offspring of all other populations, which use different set of parameters.
The effectiveness of proposed algorithm is demonstrated by phase unwrapping examples and advantages of the proposed method are discussed.
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Gao ; S. Cheng; X. Huo ; Q. Zhang Show Abstract. Repeated plastic instability accompanying serrated yielding in stress—strain curves and localization of deformation is observed during plastic deformation of many metallic alloys when tensile specimens are deformed under certain experimental conditions of temperature, strain rate, and pre-deformation. The 3D DIC system, with displacement measurement accuracy up to 0. Unlike tensile test performed on aluminums alloy, the widths of PLC bands of TMW alloy specimen, ranging from 4 mm to 4. Window size selection of windowed fourier ridges for phase discontinuity in quality-guided phase unwrapping Author s : Ming Zhao ; Qian Kemao Show Abstract.
Windowed Fourier ridges algorithm can provide a quality map to assist the quality-guided phase unwrapping. Its performance for discontinuous phase maps is investigated in this paper, where the influence of window size in the algorithm is examined. Three discontinuous phase boundaries, straight, curved, and fused, are tested for both noiseless and noisy situations.
Encouraging results are observed. We present a method for quantitative phase recovery using the axially defocused intensity information based on the phase optical transfer function in defocused situation. The image formation process is linearized by subtraction of two intensity images with equal and opposite defocus distances and quantitative phase information is separated and extracted by solving an inverse problem with Wiener filtering. Experiments confirm the accuracy and stability of the proposed method outperforms the transport-of-intensity reconstruction method.
Because of larger measurement ability of wave-front deviation and no need of reference plat, the lateral shearing interferometry based on four step phase shifting has been widely used for wave-front measurement. After installation shearing interferograms are captured by CCD camera, and the actual phase data of wave-front can be calculated by four step phase shift algorithm and phase unwrapping. In this processing, the pixel resolution and gray scale of CCD camera is the vital factor for the measurement precision.
In this paper, Based on the structure of lateral shearing surface interferometer with phase shifting, pixel resolution more or less for measurement precision is discussed. Also, the gray scale is 8 bit, 12 bit or 16 bit for measurement precision is illustrated by simulation.
Fabrication of multilevel spiral phase plates by focused ion beam milling Author s : V. Pramitha ; A. Vijayakumar ; Shanti Bhattacharya Show Abstract. Circular spiral phase plate with eight levels is fabricated directly on an indium-tin-oxide coated glass plate. Scanning electron microscopy images demonstrate the realization of multilevel phase plate on glass plate using focused ion beam milling. The greatest limiting factor in widespread use of this technique is the low efficiency because the structure is fabricated by point-by-point scanning.
In recent years, computer generated hologram is used for parallel fabrication via multi foci. In this paper, we proposed a new rapid fabrication method which use desirable multi-focus pattern as scanning cell instead of single focus point or foci array to polymerize. We establish a femtosecond laser experimental setup involved in a liquid crystal spatial light modulator.
The computer generated hologram pattern on spatial light modulator is used to produce desirable foci array. The position and intensity of each focus in the pattern can be controlled well by optimal design. We use multi foci in a line as scanning cell to fabricate some revolving structure and the Fresnel lens can be expected. This work provides a new method to greatly improve the efficiency of two-photon polymerization production in fabricating revolving structures. As the demand for precision optical components with sub-millimeter feature size steadily increasing, numerous efforts have been made in developing new techniques and in improving the existing approaches to efficiently and economically produce those components.
Glass molding process GMP is one of these methods to enable mass production of precision glass optical components in recent years. One of the key issues in GMP is precision mold insert fabrication. Since the mould are normally made of hard and brittle materials such as tungsten carbide WC and silicon carbide SiC , precision diamond grinding is by far the principal choice used to machine the GMP mould.
As the feature size of optical component gets smaller, the size of mould and grinding wheel used to fabricate the mould gets smaller too. This makes the grinding process a very time consuming and expensive task. This research aimed to improve the small mold fabrication processes by developing an effective way of producing small diamond wheels and in-process monitoring wheel profile. Diamond wheels of around 0. This paper reports on the evolution of femtosecond laser induced periodic surface structures LIPSSs on titanium surface irradiated with different wavelengths.
By SEM observations, it is noted that different nanostructures with respective surface features depend highly on the laser wavelength and the laser fluence. The period of LIPSSs formed at the laser fluence just above the ablation threshold is shorter than the laser wavelength, as well as dependence on the incident wavelength.
Experiments using wavelength of and nm, studies are performed in more detail. The period and the depth of the grooves of LIPSSs are increased with the increase of laser fluence at wavelength of nm. The created structures on the surface at the laser fluence of 0. The redistribution of the electric field intensity plays a crucial role in the creation of the HSFLs formed on the ridges of the LIPSSs, and the period decreases to half.
As compared with the surface nanostructures formed at wavelength of nm, the formation of identical HSFLs is induced with smaller laser fluence at wavelength of nm. We found that high spectral discrimination of visible light of this multi-dielectric layers MIS device is due to the optical filtering property by these multi -layers and the mid-band gap impurity states existed at the interface between the Si substrate and these dielectric layers.
Show Abstract. The performances of two liquid level sensors based on Fiber Bragg grating are studied. We investigate on enhancement of strain sensitivity of the FBG for liquid level measurement. Two different sensor heads arrangement are fabricated to exploit the strain sensitivity of FBG and use it for the liquid level measurement. The measurement sensitivity of a FBG based fiber optic liquid level sensor can be improved by controlling the parameter such as diameter of the FBG. Fractional domain asymmetric cryptosystem and cryptanalysis Author s : Sudheesh K.
Most of the reported optical techniques of encryption in literature belong to the category of symmetric cryptosystems, in which the keys used for encryption are identical to the decryption keys. In an environment of network security, a symmetric cryptosystem would suffer from problems in key distribution, management, and delivery. In this paper, we present the results of an asymmetric cryptosystem that uses fractional Fourier transform domain amplitude- and phase- truncation approach.
The conventional random phase masks are replaced with structured phase masks to further enhance the key size and hence security of cryptosystem. The scheme also uses the concept of interference and polarization selective diffractive optical element. Cryptanalysis has been carried out considering various types of attacks using phase retrieval algorithm. Numerical simulation results have been presented. Color image cryptosystem based on discrete cosine transform in gyrator transform domain spiral-phase encoding Author s : Muhammad Rafiq Abuturab Show Abstract.
A new color image cryptosystem is proposed, which is based on discrete cosine transform and spiral phase encoding in gyrator transform domain. The random phase mask is replaced by a multiple-key spiral phase mask, because it is difficult to replicate and easy to align. In this scheme, a color image is decomposed into red, blue and green color channels. Each channel is encoded independently by using discrete cosine transform and then encrypted into a spiral phase mask. The resulting image is gyrator transformed. The operations are performed twice continuously to get multiplexed encrypted image at output plane.
The rotation angles of gyrator transform along with the order, the wavelength, the focal length and the radius of a spiral phase mask of each channel provide multiple choice for the parameter of the proposed security system as encryption keys. The proposed optical setup avoids alignment problems. The performance, feasibility and effectiveness of the proposed algorithm are demonstrated by the numerical simulation results.
A novel method for image encryption under spatially incoherent illumination is proposed. The LED array is used as the spatially incoherent source. Both the encryption process and decryption process are numerically simulated. Experiments are carried out to demonstrate the basic ideal of the proposed method. The incoherent light is modulated by the spatial light modulator on the input plane as the input image to be encrypted. Then a random phase only mask is used as the key to encode the image, finally a Fourier lens is adopted to image the encrypted image on the output plane.
The encrypted intensity distribution is recorded by a CCD. In the numerical simulations, the random phase only mask is generated by a rand function. The incoherent image is composed of many source points, and any two points of these sources are spatially incoherent, but each point is self-spatially coherent. Under this property, the point spread function for the encryption system can be considered as the interference of two beams, one is the spherical beam and the other is the random phase beam.get link
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Then the encryption system can be considered as a decryption system, and the output image is the same as the original image. The random phase mask, the distance between the random phase mask and the SLM, and the wavelength of the laser can be seen as the keys of the encryption systems. Only when all these parameters are correct, can one get the right decrypted image.
The factors which could affect the practical experiment, such as quantization noise and displacement tolerances are also investigated. Compared with the conventional coherent encryption system, the incoherent encryption system proposed in this paper is free of the flaws of the optical elements, the dust particles on the elements, and other unstable factors of the environment. Robust video watermarking scheme using computer generated holographic technique Author s : Jianzhong Li Show Abstract. A novel blind video watermarking scheme offering a low computational complexity is presented in which the computer generated holograms are used as the watermarks.
In the scheme, the original video is divided into nonoverlapping groups of pictures GOPs. A quantization method is used to insert the mark hologram into the low frequency wavelet coefficients of every GOP. The extraction procedure does not need the original video. Experimental results demonstrate that the presented scheme is transparent and robust to a variety of attacks, including compression, noise addition, filtering, occlusion, cropping and temporal attacks, etc.
One of the most important advantages of the suggested method is its simplicity and practicality. Real time monitoring of petroleum leakage detection using etched fiber Bragg grating Author s : B. Shivananju ; M. Kiran; S. Nithin; M. Vidya; G. Hegde; S. Asokan Show Abstract. Detection of petroleum leakages in pipelines and storage tanks is a very important as it may lead to significant pollution of the environment, accidental hazards, and also it is a very important fuel resource.
Petroleum leakage detection sensor based on fiber optics was fabricated by etching the fiber Bragg grating FBG to a region where the total internal reflection is affected. This acts as high sensitive, fast response fluid optical switch in liquid level sensing, petroleum leakage detection etc.
In this paper we present our results on using this technique in petroleum leakage detection. Modeling and simulation of fiber Bragg grating pressure sensor for underwater application Author s : Preeta Sharan ; Sanjay S. Srinivas Show Abstract. This paper includes design and simulation of high sensitivity Fiber Bragg Grating FBG sensor for pressure measurement under water. This paper involves simulation of a super structure FBG which is encapsulated with a polymercompletely- filled metal cylinder.
An observation has been made to see the effect of polymer coating on the FBG for pressure sensitivity. Measurement of index of refraction of unknown solution using a microstructure fiber Bragg grating Author s : C. Kang; Z. Chen; M. Shih Show Abstract. We demonstrate an application of fiber Bragg grating to measure the index of refraction of an unknown liquid by using a cladding depleted FBG. The measurements of the index of refraction were calibrated by the index oil with known index of refraction.
Samples of liquid with difference percentage of sugar content were prepared and measured the index of refraction using this method. It shows that accuracy of index of refraction measurement as high as 0. From the sensitivity of the FBG center wavelength changing with strain changes on the surface, the design of a FBG strain-based asphalt pavement pressure sensor is described by designing a special FBG asphalt box-film packaging structure.
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The compactness and simplicity of the device are achieved by using the corresponding package obtained from common available asphalt. Numerical analysis and experimental results show that the response of the sensor has good regularity for a wide range of travel 0MPa to 5. In the load range, the FBG center wavelength increases from Linearity, travel and sensitivity are experimentally determined by different packaging parameters. A design chart that includes the travel 0MPa to 5. Wavelength-swept laser technique is an active demodulation method which integrates laser source and detecting circuit together to achieve compact size.
The method also has the advantages such as large demodulation range, high accuracy, and comparatively high speed. In this paper, we present a FBG interrogation method based on wavelength-swept Laser, in which an erbium-doped fiber is used as gain medium and connected by a WDM to form a ring cavity, a fiber FP tunable filter is inserted in the loop for choosing the laser frequency and a gas absorption cell is adopted as a frequency reference. The laser wavelength is swept by driving the FP filter. If the laser wavelength matches with that of FBG sensors, there will be some strong reflection peak signals.
Detecting such signals with the transmittance signal after the gas absorption cell synchronously and analyzing them, the center wavelengths of the FBG sensors are calculated out at last. Here, we discuss the data processing method based on the frequency reference, and experimentally study the swept laser characteristics. Finally, we adopt this interrogator to demodulate FBG stress sensors. So it is very suitable for most FBG measurements. A high sensitive pressure sensor based on Fiber Bragg grating FBG integrated with a thin metal diaphragm was designed and demonstrated.
To enhance the pressure sensitivity FBG is firmly glued across the diameter of the diaphragm. Under pressure, the diaphragm deforms and produces an induced strain along the length of the fiber causes shift in Bragg wavelength of the FBG. Pressure measurement is made by measuring the Bragg wavelength shift against change in pressure. The sensor was tested up to the maximum pressure of psi and the corresponding pressure sensitivity was found to be 0. The experimental results show good agreement with the theoretical results and possess good linearity and repeatability.
This sensor can be used for the measurement of medium pressure, liquid level and depth of underwater. The fibers aligning is very important in fusion splicing process. The core of polarization maintaining photonic crystal fiber PM-PCF can not be seen in the splicer due to microhole structure of its cross-section. Firstly, the light source of halogen lamp is connected to one end face of conventional SMF. If there exists visible light, they are believed to align roughly.
Now the light source of halogen lamp is changed into a broadband light source with 52nm wavelength range. The other end face of the other conventional SMF is connected to an optical spectrum analyzer. They are translationally and rotationally adjusted in the splicer by monitoring spectrum. When the transmission spectrum power is maximum, the aligning is precise. A simple 1x2 plastic optical fiber coupler based vibration sensor Author s : Kishore P. A simple noncontact fiber optic vibration sensor is designed using multimode fiber optic coupler.
The sensor works on principle of reflection intensity modulation. A single fiber port of the coupler is used as sensing head. A linear change in light intensity during its displacement from the reflecting surface within 1 mm of linear region shows a high sensitivity of 2. In comparison with dual-fiber and bifurcated-bundle fiber, this sensor eliminates the dark region and front slope which facilitates the easy alignment. The high degrees of sensitivity, economical along with advantages of fiber optic sensors are attractive attributes of the designed sensor that lend support to real time monitoring and embedded applications.
Fiber optic liquid level sensor using multimode fused coupler Author s : Sengupta D. An intensity based fiber optic liquid level sensor for continuous measurement is described. The sensing principle is based on intensity of reflected light which is disturbed by the change in proximity of the fiber probe and the reflector. A Mechanical CAM is used in the sensing arrangement. It converts the rotatory motion into a linear displacement.
A reflector which is attached to the end of the CAM follower reflect the incident light. As the displacement of reflector occur the intensity of reflected light also changes and is a measure of change in liquid level. The prototype designed sensor can sense liquid level upto 17cm.
The proposed sensor can find potential applications in transportation and process industries. In this study, the novel rotation algorithm is proposed for the phase unwrapping algorithm. The main advantage of proposed algorithm is that it can simultaneously resolve the shifting error, holes, two types of noise i. Unfortunately, these common algorithms can not resolve the problems of the shifting error and holes. Therefore, compared to these common algorithms, the proposed rotation algorithm is more effective and useful for resolving the problems of holes and noise.
Phase analysis plays a role in optical science and technology. For instance, phase analysis technique has been widely used for 3-D shape and deformation measurement by fringe projection profilometry. To analyze the phase distribution of a single fringe pattern, various fringe pattern analysis methods such as a Fourier transform, a wavelet transform, and the windowed Fourier transform have been developed.
In this study, a fast phase analysis technique, i. By the proposed method, the phase error caused by the random noise of the camera can be dramatically decreased because the intensity information is much richer than one-dimensional intensity data, which utilizes a two-dimensional DFT algorithm. The fundamental principle and primary simulation and experimental results are presented. Theses results show that phase analysis can be performed under extremely low signal-to-noise ratio measurement condition.
Partial differential equations PDEs and ordinary differential equations ODE based image processing methods have been demonstrated to be a powerful tool for optical fringe processing. Development of a fast and accurate color-encoded digital fringe projection profilometry Author s : Z. In the past two decades, fringe projection profilometry FPP has been widely used in three-dimensional 3D profile measurement for its fast speed and high accuracy.
CDFPP has the advantage of being fast speed, non-contact and full-field. It is one of the most important dynamic 3D profile measurement techniques. However, due to color cross-talk and gamma distortions of electro-optical devices, phase errors arise in using conventional phase-shifting algorithms to retrieve the phase in CDFPP. Therefore, it is important to develop methods for phase error suppression in CDFPP and thus realizing fast and accurate profile measurement.
In this paper, a phase error suppression technique is proposed to overcome color cross-talk and gamma distortions. The proposed method is able to carry out fast and accurate surface profile measurement. The real data experimental results show that the proposed method can effectively suppress phase errors and achieve accurate measurements in CDFPP. Precision heterodyne ellipsometry with an improved conic fitting algorithm Author s : Lionel R. Watkins; Matthew J.
Collett Show Abstract. Ellipsometers based on heterodyne interferometers are inherently capable of precise measurements, with the ellipsometric angles determined from the amplitude and phase of a pair of quadrature signals.
These signals are generally displayed as a Lissajous figure and the primary limitation to accuracy is determined by the goodness-of-fit to the ellipse, especially for ellipses with high ellipticity. A Michelson interferometer was constructed and a polarizer-quarterwave plate combination used to generate ellipses of moderate to extreme ellipticity. We show experimentally that our method yields excellent fits, even for axis ratios approaching 1, yielding a one-sigma error of 0.
Thareja Show Abstract. Dynamics of single and two collinearly colliding laser ablated plumes studied using fast imaging and the spectroscopic measurement is reported. The two expanding plumes colliding with each other resulting in the formation of a stagnation layer at the interface region which depend on mean free path and distance between the two plumes.
The thin films of ZnO deposited on glass polycrystalline substrate are observed to have preference for single orientation. The presence of low ionic species in the overlap region seems to play a role in getting singly oriented thin films. Optical behavior of spirooxazine incorporated vinyl functional silicates thin film under UV irradiation Author s : S. Nazri ; M. Malek; M. Zainuddin ; N. Aziz; N. Mohamed Show Abstract. Photochromic film of Spirooxazine-incorporated organosillicates material was prepared by sol-gel method and deposited on quartz substrate.
The film was examined through the variation of UV irradiation power and exposure time for optical behavior characterizations. Investigations have been carried out by UV-Vis spectrophotometry and spectroscopic reflectometry. On the other hand, we observed that the photo transformation absorption peak was also change at the region of nm to nm when different duration of UV irradiation applied. In addition, this UV curing process also increased the refractive index of film since the structures become compacted due to reduction of pore size volume in the system.
Thus it will limit the film ability to performed photo transformation which will contribute to the reduction of film coloration upon UV irradiation. It is concluded that consideration of power and duration of UV irradiation is significant for designing the function of photochromic film in led their successful use in various applications. A general analytical transient temperature field expression of KDP crystal irradiated by sinusoidal modulated laser is obtained by the integral transform method, based on the heat conduction equation of the orthotropic material.
The influence of radius, power and frequency of the laser on the transient temperature field of KDP crystal is simulated by Matlab. The results show that the temperature of material has stepwise distribution with time, which shows periodical stable distribution after some time, and it increases with the decrease of the laser radius and the increase of the laser power. The above results provide a theoretical basis for the photothermal displacement technology used in the measurement of the opto-thermal parameters of the KDP crystal.
We report an easily fabricated, broadband and high-absorbance coating for terahertz absolute radiometry. The spectral property of this coating was characterized in THz region with a home-made terahertz time-domain spectrometer. The measured results showed an extremely low spectral reflectance ranging from 0. We assembled a terahertz radiometer with this coating as absorber. This coating is highly absorptive both in terahertz region and in visible light; therefore, the power responsivity of this radiometer is easily traceable to Chinese National Laser Power Standard.
This coating is useful in traceability of terahertz sources and detectors to the SI units, and it will play an important role in infrared and far infrared absolute radiometry. The mechanical and thermal stress on lens will cause the glass refractive index different, the refractive index of light parallel and light perpendicular to the direction of stress. The optical system stress distribution result is calculated from finite element simulation, and the stress coordinate need to rotate to optical path direction.
Meanwhile, weighting stress to each optical ray path and sum the ray path OPD. The Z-direction stress OPD can be fitted by Zernike polynomial, the separated to sag difference, and rigid body motion. The fitting results can be used to evaluate the stress effect on optical component. Photo-thermal modifications in ultrafast laser inscribed chalcogenide glass waveguides Author s : Gayathri Sivakumar ; Tamilarasan Sabapathy ; Arunbabu Ayiriveetil ; Ajoy K.
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