Different from traditional electrical readout infrared imaging, optical readout infrared imaging system readout the thermo-mechanical response of focal plane array via visible light. Due to the different parameters of the optical system, usually,the infrared thermal image pixel corresponding to the thermal element of focal plane array is not consistent. And the substrate-free focal plane array brings thermal crosstalk, the image blur. This manuscript analyzes the optical readout infrared imaging principle, proposes an one to one correspondence method between the infrared thermal image pixel and the thermal element of focal plane array, optimizes the digital infrared image by the thermal crosstalk on substrate-free focal plane array. Simulation and experiments show that the algorithm can effectively enhance the contours of the infrared image detail, enhancing image quality.
This paper proposes a new phase shifting method: wave-plate phase shifting method. By different combinations of a quarter-wave-plate, a half-wave-plate, and an analyzer, phase delays are introduced in the interference light path in order to achieve the phase shifting digital holography. Theoretical analysis, numerical simulation, and experiments are conducted to verify the validity of this method. The numerical simulation shows that the result of the wave-plate phase shifting method is consistent with that of the traditional four-step phase shifting method. The experimental results successfully reconstruct the object light intensity in the image plane. Based on the wave-plate phase shifting method, a pixelated wave-plate array structure is designed to achieve real-time phase shifting digital holography. The wave-plate array phase shifting method not only can reconstruct object image of high quality, but also can be used in dynamic phase measurement. Therefore, pixelated wave-plate array structure and wave-plate array phase shifting method could be widely used in practical applications.
This paper presents an improved direct binary search (DBS)-based algorithm for generating holograms to holographic optical tweezers. The simulations show that the improved algorithm greatly enhances computation speed while maintaining high hologram efficiency and high-intensity homogeneous target spots. The improved algorithm was applied to generate holographic optical tweezers in several experiments. The experiments demonstrate that real-time trap and manipulation can be realized with the improved algorithm if the number of trapped microparticles is small.
Using the phase shifting and the grating projection method, the kinematical parameters of dragonfly in free flight were measured. In our experiment, during projecting parallel sine fringes on the dragonfly's wings with a projector, the high speed CCD TV camera (1000 frames per second) recorded the dragonfly and the fringes projected on the dragonfly's wing , then the shape of the dragonfly's wings in every frame could be gutted using SCPM (Spatial-Carrier Phase Measurement) method. According to this data, we designed a program which can show the change of the gesture of the dragonfly's wing, the 3-D figure, the contour line and the curve of any transversal of the dragonfly's wing at any given time. From the figures of the 3-D deformation, we also can see that the deformation is not completely negative, it must could be control by the dragonfly via the veins on the wing.
A novel optical edge projection method to measure the profile of an object is proposed. It can be applied to some special field for example to measure a profile of a specimen with a black and soft surface. A structured black-and-white light edge is projected onto an object surface and the distorted optical edge shadow image is captured by a CCD camera. The border line of the optical edge shadow is extracted and compared with a reference line, the distortion modulated by the height of the object surface is then obtained. By calculating the height, and scanning the optical edge shadow along the object, the height information obtained from a series of images can be determined. Combining the border line in these images, the profile of the object can be measured.
This paper reports a novel freestanding stencil bi-material cantilever structure without sacrificial layer process in detail; the complexity and costs of fabrication process are reduced greatly. This type of microcantilever is made of two material layers (SiNx/Au), which is a 2dimension device, not a 3dimension one. The cantilevers and the support points are at the same plane in the stencil structure. MEMS sacrificial layer process problems are avoided completely in the process of the freestanding stencil bi-material cantilever microstructure so as to simplify process steps. Since two materials selected in the bi-material cantilever have a large mismatch in thermal conductivity and expansion coefficient, and all cantilevers in the device are freestanding completely, this kind of device is sensitive to a lot of physical varieties, such as thermal, infrared, mechanical vibration and electronic signals. This paper illuminates the total fabrication process of freestanding stencil bi-material cantilever structure; and in particular presents an application of uncooled infrared imaging system based on the novel freestanding bi-material cantilever structure in the final part of this paper.
Porous alumina thin membranes containing parallel regular pores of uniform size (nano scale) and normal to substrate surface have been prepared and fabricated. Their fine pore structure has recently made the porous films to be one of the ideal templates for synthesis of nano-structured materials and MEMS (micro-electro-mechanical systems) and separator for separation those small grains from mixed liquid. Unfortunately, the significant macro-mechanical properties of porous alumina thin membrane have not yet been understood clearly. Because the geometry of this kind membrane is multi-scale covered with mm to μm to nm, macro-mechanical behaviors of the porous alumina thin membranes belong to nonlinear mechanics. To measure and calculate those mechanical properties are difficult. Using "temporal speckle pattern interferometry" to measure successfully the large deflection vs perpendicular uniform pressure. Then the mechanical properties of the porous alumina membranes, such as elastic modulus and fracture strength, can be obtained based on plate/shell models and flexile thin membrane model. The results indicate unusual mechanical behavior of it and help us to understand the relations between microstructure and macro mechanical properties.
A new method combining temporal phase analysis with dynamic digital speckle pattern interferometry is proposed to study Portevin-Le Chatelier effect quantitatively. The principle bases on that the phase difference of interference speckle patterns is a time-dependent function related to the object deformation. The interference speckle patterns of specimen are recorded with high sampling rate while PLC effect occurs, and the 2D displacement map of PLC band and its width are obtained by analyzing the displacement of specimen with proposed method.
The phenomena of Portevin-Le CHaltelier (PLC) band propagation and its pulsation were investigated by using dynamic digital speckle pattern interferometry (DSPI). Pulsation of fringe density in the inside of the slip band accompanying with the serrations of load curve was observed. When the load falls in the serrations, the slip deformation happens just like an avalanche, and the specimen takes a shrinkage deformation in the outside of the slip band to compensate the elongation deformation in slip band, even for a tensile test. The maximum elongation in the slip band causing by the avalanchine slip is about 7.6 μm.
A new digital speckle correlation method, the Wavelet Transform based DSCM (WTDSCM) is presented. By this method, the two images of an object before and after loading can be expanded into two series of sub-images according to their frequency band respectively by wavelet transform. Choosing the suitable sub- images pairs mainly contributed by signal speckles, and then inducing the DSCM to calculate the deformation of the object, the probability of mismatch caused by noise could be reduced and the precision of DSCM can be improved. The experimental calibration results indicate that the precision of the WTDSCM is higher than normal DSCM.
In this paper, an advanced image processing method, the discrete dyadic wavelet transform based non-linear filtering method applied to speckle fringe pattern, is presented. By this method, an image can be expanded to a series of sub-images according to their frequency band. The different filtering skills will be applied to the sub-images and the rebuilt image will keep the original characteristic except the speckle noise. For example, it can keep the border of the object in the fringe pattern clearly after filtering the speckle noise. Compare with the other kind of wavelet transforms, the Discrete Dyadic Wavelet Transform need not decreasing sample the original image, so the distortion of the rebuilt image can be greatly avoided. The principle of the dyadic discrete wavelet transform is introduced first, and then a practical algorithm to reduce the speckle noise of a fringe pattern is given. At last part of this paper, a computer simulation result processed by this method is presented.
Experiments for damage evolution of internal structure in Bi- 2223/Ag sheathed tape under tensile loading at 77K were done at BSRF. With increasing of load, the start-up and growth of micro cracks in tape were observed. Depending on the experimental results, it showed that: superconducting capability kept on when the material was at linear elasticity, and would lose when the material came into being plastic flow.
A test system of fiber optic displacement sensor (FODS) was developed and applied to measure Ag clad multi-core (formula available in paper) (Bi2223/Ag) superconductor tape at liquid nitrogen temperature (77K). A method intensity compensation was used to eliminate the fluctuation in light source and fiber attenuation. The sensor's transmission characteristics and calibration function were obtained at 77K. The stress-strain curve of the multi-core Bi2223/Ag tape was presented, and its stress-Jc relationship provided a useful reference to the application of the tape. The obtained result reveal that: (1) this sensor system can normally work at 77K; (2) its linear operating range is up to 1.6mm; (3) multi-core Bi2223/Ag tape's stress-stain relationship and stress-Jc relationship can be measured real time; and (4) it overcomes the weaknesses that cryogenic strain gauges can only measure the surface deformation of these kinds of composite tapes.
Path independent algorithm is frequently used for 2D phase unwrapping. The weighted phase unwrapping technique recently published by Ghiglia and Romero, which is based on least-squares method, obtained by the fast cosine transform, is a robust and fast path independent solution. We have improved weighted phase unwrapping by utilizing intensity modulation analysis to determine the weights for phase-shifting profilometry. An experimental result of object shape measurement is given to prove the validity of this technique, and make a contrast between the binary weight and decimal weight constructed by modulation analysis.
The phenomena of Portevin-Le Chatelier (PLC) band propagation and its pulsation accompanying the serration of load curve in a tensile test of aluminum alloy were directly observed by using dynamic digital speckle pattern interferometry method. In the plastic deformation stage, a slip band is formed and propagates repeatedly along the tensile direction with a certain speed and a certain bandwidth. The propagation speed decreases gradually with the increasing of plastic deformation, and finally the specimen cracks at the position where the band stops. The same slip fringe patterns observed from the front surface and rear surface of the specimen simultaneously show that the slip plane goes through the thickness of specimen. Pulsation of fringe density in the inside of the slip band accompanying with the serrations of load curve was observed. The pulsation period corresponds with the width of the serration. When the load falls in the serrations, the slip deformation happens just like an avalanche, and the time of the avalanche slip is less than 0.03 seconds. Corresponding to the happening of the avalanche slip, dense shrinkage fringes appear on the outside of the slip band. The specimen takes a shrinkage deformation in the outside of the slip band to compensate the elongation deformation in slip band at the moment of avalanche slip, even for a tensile test. The elongation value in the inside of the slip band causing by the avalanche slip is in the order of 10 micrometers by calculating with observed results.
In Fourier transform method for carrier fringe pattern processing, the variety of windows used is compared for their phase retrieving accuracy by computer simulations. The results show that, (1) Two dimensional Fourier transform method is better than the one dimensional transform; (2) The phase errors at image edges are large and should be discarded; (3) No new windows are needed since it is unlikely to improve the phase retrieving accuracy.
In this paper, a novel image processing method, the Wavelet Transform based Non-liner Filtering Method applied to speckle fringe pattern (WTNFM), is presented. When traditional image processing methods, such as median filter, mean value filter or FFT (Fast Fourier Transform), are employed to reduce the speckle noise of an image pattern, some useful information will be lost while the noise being removed. For example, the board of the object in the pattern would become blur. The WTNFM, on the other hand, can reduce the loss of information when the speckle noise is removed from the fringe pattern because it can apply different filtering method to the different area of the fringe pattern. It can keep the board of the object in the fringe pattern clear after filtering speckle noise. The principle of the wavelet transform is introduced first, and then a practical algorithm to reduce the speckle noise of a fringe pattern is given. At last part of this paper, a computer simulation result processed by this method is given.
The paper introduces a novel method to measure accurate thickness. On the basis of the principle of active trigonometry with vertically incident mode, an obliquely incident mode is proposed. The method is specially designed for a reflective surface of an object, such as a thin steel plate, to measure its thickness in real-time. The influence of the small deflection which is caused by mechanical vibrations is discussed and the manner to reduce this influence is given too.
The extra-low temperature has great influence on the mechanical properties of the material which is used widely in aerospace science and others. In our experiment of stretching the Extra-Low-Interstitial (ELI) Ti-5-Al-2.5Sn specimen, we found a new phenomenon of metal mechanics -- multi-necking. The contour of the specimen was also measured. We presented an experimental scheme of digital speckle pattern interferometry in room temperature to observe the in-plate deformation field of the whole process from the beginning of elastic deformation to the end of plastic deformation until fracture. Experimental results of the low temperature and normal temperature are much alike, expect for the difference of the multi-necking quantity. Based on the experiment results, a rough explanation was presented.
In this paper, the evolution properties of micro-deformation field in the copper bicrystals with a symmetric tilt boundary are studied with Digital Speckle Metrology. The micro-speckles are successfully made and the SEM speckle photographs under different loading stages are obtained. The deformation field of the copper bicrystals is quantitatively studied for the first time, and the micro-displacement field and strain field are accurately calculated. The experimental results show that, the evolution characteristics of the displacement field is obviously different from that of the macro-displacement field. These results provide some basic experimental data for the study of micromechanics.
A new electronic shearing speckle pattern interferometry using a special Ronchi grating as the shearing element has been developed and applied to deformation measurement and non destructive testing (NDT) in the practical environment. This special designed Ronchi grating is a kind of phase grating. It can make zero order and all even order beams disappear and among all odd order beams the +/- 1 order beams are much stronger than others. This new shearing element has many advantages, such as small volume, light weight, lower price, lower energy lost and good quality of shearing image. The experimental results show that it is good at electronic shearography.
Surveying deformation of propeller blade under hydrodynamical load is a factual engineering problem when propeller has been developed to a certain stage. This paper develops a photoelectronic method based on subpixel high precision object position surveying. A thin laser beam is incident upon a small reflector adhered to the surveying point on blade, the reflected light is focused on a frosted glass and there appears a facula. The angular deformation of the surveying point causes the facula to move and the motion is detected by an image processing system. The relationship between the motion and the angular deformation under the influence of refraction index is given. The flash method and the facula image grab are also discussed. Finally, angular deformation of 48 surveying points of a highly skewed propeller model of a 2800 TEU container ship under mooring status rotating at 500 and 750 rpm are successfully obtained.
ESPI/DSPI has real time subtraction function and has been used to measure fast deformation. But usually, ESPI/DSPI can not simultaneously acquire two frames which is needed for recording two displacement components (U, V) of in-plane fast deformation. In our experimental setup, the specimen is illuminated by 4 beams symmetrical to normal z. Two beams lie on x-z (y-z) plane with y (x) polarization. By using of a Wollaston prism, two speckle patterns are shifted without overlap. Only one CCD camera is adequate to capture these two patterns as one frame at the same time. An image processing system is used to get fringes patterns as U an V contours real-timely. A strip specimen has been studied by this method.
In this paper, a new digital speckle intensity correlation searching technique which is named as 'differential oriented search' is proposed. This method effectively makes use of the distribution characteristics of the correlation functions, which makes the calculating time be considerably reduced. Experimental results shows that, the method presented here is a kind of high speed, high accurate and practical correlation metrology.
The factors that affect the accuracy of photo-carrier technique are mainly speckle noise, additive random noise, gradient change of phase function and boundary. They have been simulated by a microcomputer and their effects on phase demodulation when FFT method is used have been studied in this paper. Besides, the bandwidth and undistorted demodulation characteristics in photo-carrier measurement have been investigated with FFT analysis method.
A new optical head for an electronic speckle pattern interferometer (ESPI) has been designed. The special design is that of a diffuser and a mirror instead of all optical elements and mechanisms of the existing optical head. Another special design is that of a double frequency grating adopted as a shearing element. The new optical head can be operated as a double beam speckle interferometry and shearography. It is light in weight and has very good anti- disturbance function. The experiments are successful when they are combined with an image processing card and software.
Two methods of extracting velocity vectors from particle image patterns are described. The results are compared with Particle Image Velocimetry using the well established cross- correlation technique for a case of natural convection from a heated tube submerged in a water bath. In an endeavour to improve the accuracy of velocity extraction, velocity gradients have been introduced into the algorithm. The procedure is repeated to a chosen iterative limit. Results presented show the effect of the gradient operator on the velocities obtained in regions where the velocity gradient is large.
A non-contact shape measuring system using fiber optics and digital speckle pattern interferometry (DSPI) is described. Fringe patterns for obtaining the height distributions of the shape are generated by traversing one of the illumination beams. The system utilizes a 4-step phase stepping algorithm to perform the data reduction. A semi-automatic procedure for calibrating the piezoelectric phase shifting device is reported. The equations for calculating the surface height are stated and typical results for two specimens are shown. Advantages and limitations of the technique and the optical system used are discussed.
Speckle pattern interferometry using phase stepping and digital processing is proposed and has been used to measure the shape and deformation of a 3D surface. A four beam arrangement, in which one beam is chosen to act as the reference beam, is described. A low cost piezo-electric translator is incorporated in the arrangement to permit the implementation of phase-stepping. Images are acquired by a CCD camera and PC based image processing system.
As well as providing 3D deformation measurements, the arrangement has also been used to determine the object shape by moving one of the illuminating beams. For the shape and deformation measurements, thirteen independent speckle patterns are acquired and processed. Phase maps are produced using a conventional 3-step technique and hence surface contours, displacements and strains can be obtained.
A speckled object-reference beam is used and has the advantage that the measurements are less sensitive to vibration and whole body motion than a smooth reference beam arrangement. A flat surface mounted in proximity to the surface under investigation acts as a reference plane and is used to improve the accuracy of the measurements by validating the phase-stepping steps and verifying geometric and sensitivity parameters.
The technique has been applied to the measurement of a cylinder under internal pressure. The experimental results are compared with conventional point measurements. The optical arrangement and experimental methodology are described. Advantages and limitations of the technique, together with sources of error and measurement uncertainties are discussed.
In our presentation we will concentrate on the dynamical experi
mental techniques about the deformation of the finite-circular metal
plates after normal impact . Holographic interferometry and defocused
speckle photography are applied to get the full field response.
Synchronization is accomplished with the electronical equipment
specially designed by author. A new loading apparatus is developed to
determine the transverse impact waveforms.
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