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Aiming at the observation of micro structures and micro optical elements, we proposed a fast and nondestructive microscopic observation method based on lensless digital holography technology. Firstly, the basic principle of lensless digital holographic microscopy imaging technology based on spherical wave is introduced. CCD was adapted as photoelectric converter, designed the lensless digital holographic microscopy imaging system based on Michelson interference optical path,and the reflection mirrors were used to form a folded back optical path, which made the system structure simple,compact, and have a better portability. And we used USAF1951 resolution plate performed resolution calibration experiment and got that the resolution of the system was 6.69 μm,amplified factor was 3.375, and working distances was 12 mm. A practical measurement of the surface structure of wafer was also carried out. Experiments verified the feasibility and effectiveness of the system, and the method is expected to be applied to perform quantitative measurement for the surface topography of MEMS, micro optical elements and so on.
This research focuses on the effects of an increasing pressure on the soot formation during combustion of vaporized liquid fuel. Firstly, soot formation is measured in a laminar diffusion flame of n-heptane up to 3.0 bar. The soot volume fraction in the diffusion flames has been measured using Laser Induced Incandescence (LII) calibrated by means of the Line of Sight Attenuation (LOSA) technique. The 2-D images of soot distributions have been captured, and the integral soot volume fractions show power law dependence on pressures. Secondly, a specially designed High fueling system (called "doped flame") is presented in this paper. This setup allows for soot measurements in laminar diffusion flames of liquid fuel blends at elevated pressure. Fuels with two typical molecular structures, namely linear and saturated cyclic hydrocarbons, are examined in both non-oxygenated (n-hexane and cyclohexane) and oxygenated form (1-hexanol and cyclohexanol). The experiment data suggests that soot is more prevalent for cyclic structures relative to their linear counterparts.
A binary phase computer-generated hologram(CGH)is designed for precisely testing an aspherical surface in Cassegrain optics. the design principle and is reviewed, Key questions about Optimal Designing of CGH phase function, calculation of Step position and depthare discussed.the concept of virtual glass is introduced for modelling tested surface quickly, the diffraction order is separated by joining coaxial carrier in allusion of center hole of primary mirror in cassegrain system, complexity of phase quantification is simplified, the optimal depth is gotten by numerical simulation,reducing the processing difficulty. design methods are proposed. an instance and simulation is presented and the CGH is produced. root-mean-square(RMS)error obtained from surface testing is 0.018λ,the test result is compared with that of compensatory mirror test meth, which is 0.019λ(RMS).It is demonstrated that the results show a good agreement.The design method is effective,can be used insurface testingof primary mirrorin Cassegrain optics.
Combining the advantages of both Structured Light and Close Range photogrammetry is an effective method for large scale optical 3D measurement. A number of coded targets are required to be pasted on the measured objects, which produces a series of shortcomings and limitations. This paper proposes a structured light measurement based on inverse photography. An auxiliary inverse camera is installed on a structured light system. When the single local measurement is operated, the inverse camera observes a large LCD screen that is used as an oriented target. According to the multiple imaging constraints for inverse camera, local 3D data of multiple structured light measurements are unified in a global frame defined with the large LCD screen, to achieve the whole data of large scale 3D measurement. The proposed methods exhibit the advantage of information inverse transmission, and can reach the result of contact-less and large scale 3D measurement.
The 3D image-based face recognition technology has made great progress in recent years, with good performance achieved under some constrained conditions. However, the technology is still limited by some factors such as facial pose and expression. To solve this kind of impact, the recognition methods must be improved. This paper shares the development status of 3D image face recognition by discussing a series of face matching methods and fuse-improve methods. And separately through three angles:spatial matching methods, local feature based methods and global feature based methods, to state some improvement of 3D face recognition methods. Besides, some experimental results of improved methods are listed and the reasons about effectiveness of the methods are analyzed. Finally, the paper summarizes some challenges which hinder the improvement of 3D face recognition methods, and explore the future research trend.
Infrared imaging detection of astronomical objects is of great importance in astronomy and astrophysics. A high-performance infrared detector is crucial to infrared astronomical observations. The performance test and evaluation of an infrared focal plane array (IRFPA) detector in this article are significant for infrared astronomy. According to the particularity of astronomical application, we give test principles and methods of performance parameters such as gain, readout noise, linearity and dark current, by analyzing characteristics of an IRFPA detector. A laboratorial testing platform is established to realize the performance test of an IRFPA detector with a wavelength range of 1~14 μm. We have completed a performance test of an IRFPA detector made of a domestic 3~5 μm HgCdTe chip. The test results reveal that the linearity of the IRFPA detector is pretty good, over 99.9%. Due to the relatively large readout noise and dark current, there is still a wide gap between the IRFPA detector and high-performance astronomical detectors abroad.
Objective:To study using the confocal laser microscopy Raman Spectroscopy for Rapid Analysis of edible oil saturated fatty acids(SFA), monounsaturated fatty acids(MUFA)and polyunsaturated fatty acid(PUFA) the content and proportion. Methods:Cleaning Raman spectroscopy information by derivative pretreatment, using partial least squares to establish optimized Raman quantitative prediction model of SFA, MUFA, PUFA, which providing accurate data base for the calculation of the proportion of fatty acids. Results:Determination coefficient R2 of SFA, MUFA and PUFA quantitative analysis model were greater than 0.99, the RPD is greater than 3, indicating that the model has high stability and good predictive ability. Conclusion:Laser Raman spectroscopy combined with chemometrics methods can quickly and accurately determine the content and proportion of edible oil SFA, MUFA, PUFA, providing a practical detection methods for the rapid detection of edible oil quality.
Color correction is the essential safeguard method to keep the image color constancy for a color camera. In traditional color correction methods, the color calibration coefficients are mostly obtained by the polynomial regression model, whose correction accuracy is often insufficient. So a high order polynomial fitting method based on LASSO (Least Absolute Shrinkage and Selection Operator) regression model is proposed, considering that LASSO can compress the polynomial coefficients efficiently to guarantee the model complexity and improve the correction precision as well. The experiments are conducted using D65 standard light source and ColorChecker 24 as the imaging object. The results characterized by CIELAB color difference function show that compared with traditional linear regression and quadratic polynomial regression methods, the images corrected by LASSO method has a better effect, with the mean color difference value about 5.
Linear target detection is one of the important courses in the artificial target recognition processing from the remote sensing imagery. The internal key technology is how to extract the long straight edges of the target from the background efficiently. Hough Transform is one of the classic methods for line detection. In view of the large scale and complex background in one remote sensing image, Standard Hough Transform (SHT) may generate too many short lines to distinguish the useful long linear targets. An improved method based on probabilistic Hough Transform (PHT) is proposed. Firstly, it divides the primary remote sensing image into sub-blocks and Canny operator is applied to detect edges inside each blocks. Then SHT is used to detect short lines and cluster them into groups to avoid most of the interfering lines. Finally, the parallel line pairs are extracted and filtered from the rest lines to confirm the long linear targets. Experiments show that the novel method can detect the linear target efficiently from the complex background.
In this paper, a piece of CdSe single crystal with a size of Φ30×40 mm3 has been grown by the modified vertical unseeded vapor sublimation method. The accurate (001) face was obtained by X-ray diffraction test after crystal was cleavaged. A CdSe infrared waveplate with size of 20×20×3 mm3 was got by cuting, grinding and polishing. Then the surface of CdSe infrared waveplate was polished by chemical mechanical polishing method in liquid maxed alkaline solution and polishing liquid. The results show that polishing treatment can effectively reduce the scratch, defects and surface roughness of structure layer, and the infrared transmittance of the plate in the range of 2-20 μm is high(up to 70%), which can satisfy the processing requirements of infrared waveplate.
(Ba1-xCax)(Ti0.98Sn0.02)O3(BCTS,x=0.00,0.01,0.02,0.03) lead-free ceramics were prepared by traditional solid-state reaction method. Effect of microstructure on phase structure and piezoelectric properties with different sintering temperatures were studied. According to the results by X-ray diffraction, all samples possess pure perovskite phases without second phases. By scanning electron microscopy (SEM) images show that the grain was uniform, phases structure was more dense and with less porosity, the grain growth of spiral structure, when the sintering temperatures is 1450℃. The optimum electrical properties can be obtained at x=0.01 and sintering temperatures is 1450℃:d33=346 pC/N.
Transport of intensity equation (TIE) is a powerful tool for phase retrieval and quantitative phase imaging,which requires a series of intensity images along the optical axis. The numerical difference is used to estimate the first order axial differential of light intensity at the focal plane, and the phase information can be obtained directly by solving the transport of intensity equation. It does not require coherent illumination and works well on conventional bright-field microscopes. In recent years, Transport of intensity equation has been widely studied at home and abroad. It shows great application prospect in the fields of adaptive optics, X-ray diffraction optics, electron microscopy and optical microscopic imaging. This paper proposes a multi-mode imaging system based on transport of intensity equation, which combines the traditional microscope and the computational imaging, and gives the ability of obtaining the quantitative phase to the traditional microscope.The versatility and effectiveness of the system are demonstrated by microexamination of several transparent colorless specimens, such as unstained pollen grains and live HeLa cells.
In order to accurately reconstruct the height of the tested object, phase unwrapping plays an important role in the three-dimensional (3D) shape measurement system based on phase analysis. The traditional phase unwrapping method often requires additional projected images, and/or needs a time-consuming 2D spatial phase unwrapping algorithm. Meanwhile, Fourier Transform Profilometry (FTP) only needs to collect one or two deformed fringe pattern to restore the 3D shape of the measured object. It is fast and easy to implement and suitable to measure the dynamic object. A new phase unwrapping method is presented in this paper, in which the phase order can be correctly retrieved from integer multiples of 2π and the phase different between the wrapped phase and the unwrapped reference phase. If the measured object is more complex, some virtual phase plane created by adding or subtracting 2nπ from the reference phase will be used to get the correct phase order. Finally, the natural continuous phase distribution of the measured object can be obtained from the combination of the multi-step phase unwrapping results. The feasibility of this method is proved by the results of simulation and 2 actual experiments. It is proved that this method is fast, no spreading error and can be efficiently used in the measuring system based on FTP method.
In the area of modern materials stress and strain measurement, DIC(digital image correlation) has the advantages of non-contact, full field, low requirement of experimental conditions and high precision. It is an effective and practical method of stress and strain measurement, which is widely used in experimental mechanics and other fields. In this paper, the development of DIC in materials stress and strain is summaried and DIC is compared with other measurement techniques. Then, the system structure, related algorithms and search methods of DIC are introduced. Finally, the latest applications and new products of DIC in stress and strain of materials are listed.
Incoherent digital holography is one of the important research fields of the current international frontier. Due to the use of coherent light source a lot of speckle noise and spurious interference will be introduced in traditional holography. And it requires high equipment and strict recording conditions, which will seriously limit its application range. Incoherent holography with incoherent light source can completely avoid these problems. FINCH is one of the most important types of incoherent holography. In this paper, the principle and characteristic of FINCH is briefly introduced. Suppression of DC term and conjugate image, improvement of imaging resolution and the reconstructed image quality and the applications of FINCH are analyzed in detail.