Subwavelength grating polarizers were designed to generate particular cylindrical vector beams. Based on the rigorous vector diffraction theory, the mechanism of the subwavelength gratings converting circularly polarized beam into cylindrical vector beams was analyzed. To obtain the particular type of cylindrical vector beam, a method of design of subwavelength grating polarizers was proposed and the designing procedures has been discussed. The basic function of the polarizer designed in this work is to convert the circularly polarized beam into radially/azimuthally polarized beam. By further improvement, the polarizer could generate complex cylindrical vector beams. Using the Richards-Wolf vectorial diffraction integral, the intensity distributions of the output focused beams from the polarizer were calculated. A phenomenon of divided focal spot was found in the vicinity of the geometrical focus point.
A polarizer element with subwavelength nanostructured grating was fabricated by using focused iron beam. The gratings on the polarizer are variant spatially. By designing the distribution of the gratings, the polarizer can be used to convert circularly polarized light into radially polarized light. The operation wavelength of the element is 532nm, which has been confirmed by an experiment. Parameters associated with the polarized light converted by the polarizer were also measured in the experiment.
Due to the absorptive and scattering nature of water, the characteristic of underwater image is different with it in the
air. Underwater image is characterized by their poor visibility and noise. Getting clear original image and image
processing are two important problems to be solved in underwater clear vision area. In this paper a new approach
technology is presented to solve these problems. Firstly, an inhomogeneous illumination method is developed to get the
clear original image. Normal illumination image system and inhomogeneous illumination image system are used to
capture the image in same distance. The result shows that the contrast and definition of processed image is get great
improvement by inhomogeneous illumination method. Secondly, based on the theory of photon transmitted in the water
and the particularity of underwater target detecting, the characters of laser scattering on underwater target surface and
spatial and temporal characters of oceanic optical channel have been studied. Based on the Monte Carlo simulation, we
studied how the parameters of water quality and other systemic parameters affect the light transmitting through water at
spatial and temporal region and provided the theoretical sustentation of enhancing the SNR and operational distance.
High temperature pressure pipes were widely used in the chemical, oil companies and power plants, but the pipe burst incidents occurred from time to time, which had caused some damages on people’s lives and property. Thus, in this paper, with the aim to solve this problem, a FBG (FBG: Fiber Bragg Grating) strain gauge structure which consists of three FBGs is designed and fabricated based on the theoretical strain and stress analysis. The strain gauge can be used for the real-time surface strain monitoring of high temperature pressure pipes. In the strain gauge, the elastic hightemperature alloy(10MoWVNb) is chosen as the substrate. The three FBGs with a similar performance are fabricated on the substrate with the high-temperature glue. Among the three FBGs, FBG1 is used for the horizontal strain sensing of high temperature pressure pipes., FBG2 is used for the longitudinal strain of high temperature pressure pipes, and FGB3 is used for temperature compensation. The strain gauge has a feature of high temperature resistance, temperature compensation and two-dimensional strain measurement. The experiment result shows that : the sensing ranges of temperature is 0~300°C, the transverse strain sensitivity is 1.110nm/με, the temperature sensitivity is 0.0213nm/°C; The longitudinal strain sensitivity is 1.104nm/με, the temperature sensitivity is 0.0212nm/°C; the temperature sensitivity is 0.0103nm/°C. Therefore, the strain gauge can meet the needs of the high temperature and pressure pipes.
The working principle of LPFG(Long-Period Fiber Grating) is based on coupling effect between propagating core-mode
and co-propagating cladding-modes. The effective refractive index of cladding-modes could be obviously influenced by the environmental changes resulting in LPFG more sensitive than FBG (Fiber Bragg Grating) in sensing areas, such as temperature, strain, concentration, bending and etc. LPFG should have more potential in the field of sensors compared with FBG. One of the challenges in using LPFG for environmental sensing is how to interrogate the signal from the LPFG transmission spectrum, due to the large spectral range of the resonant dip. Nowadays the application of LPFG is normally limited in signal interrogation of FBG as optical edge filter. The signal interrogation of LPFG itself needs further research. Presently research on signal interrogation of fiber grating focuses on wavelength interrogation. The aim of wavelength interrogation is to get the wavelength shift caused by environmental change. To solve these problems, a kind of strain sensing interrogation technique for LPFG with low-cost based on tunable FBGs has been developed. Comparing with the method using Fabry-Perot cavity, tunable FBGs can lower the cost with the guarantee of sensing precision. The cost is further lowered without using expensive optical instruments such as optical switch. The problem of temperature cross-sensitivity was solved by using reference gratings. An experiment was performed to demonstrate the interrogation system. And in the experiment, the sensing signal of LPFG applied 0-1300με was successfully interrogated. The results of the interrogation system and OSA are similar.
The modified base-catalyzed method and the seed growth method were employed to synthesize Eu(TTFA)3-doped silica
hybrid spheres. The transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and
fluorescence spectrometer were used to characterize the doping particles. The results show that all kinds of as-prepared
particles present the spherical morphology and the smooth surfaces. TEM images reveal that silica hybrid spheres are
monodisperse and have an average diameter of sub-micron. FTIR analyses show that synthesized silica colloidal spheres
mainly consist of 4-fold silaxone rings, including incomplete condensed silanols and incomplete hydrolyzed alkoxy
groups. The hybrid spheres doped with Eu(TTFA)3 prepared by different methods exhibit the characteristic
photoluminescence (PL) of the Eu3+ ions and excellent narrow-line emission characteristic of Eu3+ ions. The existence of
silica matrix has obious effect on the absorption properties of the ligand and slight effect on the emission properties of
Eu3+.
In this paper, a general scalar model to analyze the diffraction spectrum of holographic variable line space (VLS) plane
grating at oblique incidence is proposed. The analytic expression for the diffraction spectrum of a VLS plane grating at
oblique incidence with a parallel and uniform beam was obtained on the basis of Fraunhofer diffraction theory. And the
applied scope of the analytic expression is that the grating period is much larger than the incident wavelength. Then
some computing examples are given in the condition of single wavelength incident. This oblique incidence model can
provide a theoretical reference for the real distribution of diffraction spectrum of holographic VLS plane grating. In
future work, the diffraction efficiency and polarization state will be considered.
Today zoom optical system is more used in many fields. It can be satisfied with many special imaging instances with its
superiority on ability of supplying different visual field and resolution. But the conventional zoom system must have
more than two moving elements to realize focus turning and imaging shift compensation at the same time. This makes
the system have large volume and weight, and complicated structure. Liquid lens is a kind of novel optical device based
on biological vision system. By utilizing this device, zoom camera can be designed in a new simple way. In this paper, a
liquid lens operated by a stepper motor had been demonstrated. A new way of designing a micro zoom system without
any moving lens had also been introduced. And a kind of hybrid diffractive-refractive liquid lens had been presented to
improve the imaging quality. A micro bifocal zoom endoscope system including two pieces of liquid lens was contrived.
Finally, it is thought that although many technologies, especially the package method should be solved better, the liquid
lens micro zoom system has very wide potential application in the fields that the system's volume and weight are strictly
limited, such as endoscope, mobile, PDA and so on.
In recent years, a new fiber position sensor based on wavelength encoding plane variable-line-space gratings is
developed and has attracted more and more interest. In this paper the theoretical background to the fiber position sensor
concept is briefly described. The large slope groove density distribution variable-line-space grating with holographic
recording is used in fiber position sensor. The preliminary results obtained were quite noteworthy. Due to the unevenness
of the incident light intensity in different wavelength, the diffractive intensity of different position change quickly. The
diffraction wavelength curve of the system is given. The resolution of the position sensor is also discussed in this paper.
Under the high energy irradiation, the charges (even little) of molecules of polymer can cause the physical and chemical
characteristics evident changes of polymer. The physics and chemical mechanisms which are responsible for radiation induced loss
was analyzed. The radiation damage of polymethylmethacrylate (PMMA), Polystyrene PS and polycarbonate (PC) optical fiber
under γ-ray irradiation was researched experimentally. The visible light transmission of the POF under different irradiation dose
was measured. The results indicated that the radiation damage of three kinds of POF was wavelength-dependent. Under lower dose
below 1KGy, the transmission rate decreased identical in the whole visible light range. When the irradiation dose exceeded 5KGy, the
transmission rate reduced obviously, and the recovery indicated that the visible light transmission rate of the POF in the range of
400nm to 500nm comparing with 600nm to 800nm, decreased seriously under the irradiation dose exceeded 5kGy. The transmission
rate of both PMMA and PC have an evident peak value at the range 550nm-650m, and that of PS has a wide band at the range
500-700nm. We also measured the recovery of three kinds of POF under different irradiation dose by measuring several times the POF
after stopping irradiating.
The Step-index plastic optical fiber (SIPOF) bandwidth calculation model is given. The model includes not only the modal delay but also the attenuation and mode coupling effects. the numerical solution of the power flow equation in Fourier domain which is the main equation in this model is reported. This solution is based on Crank-Nicholson implicit difference method. The frequency response function and bandwidth of four kinds of SIPOFS with different Numerical aperture is researched. The frequency response function and bandwidth under selective excitation is numerically calculated. The results imply that the selective excitation of SIPOF increased effectively the fiber bandwidth. Calculated results are useful for practical application of plastic optical fiber.
Silica spheres doped with Eu(TTFA)3 and/or Sm(TTFA)3 are successfully synthesized by using the modified Stober method (the base-catalyzed method). Transmission electron microscope (TEM) shows that the hybrid particles have spherical morphology and an average diameter of about 210 nm. Energy dispersive spectroscopy (EDS) confirms that the rare-earth (RE) complexes are incorporated into the hybrid spheres. The particles consist of 4-fold siloxane rings as determined by Fourier transform infrared spectroscopy (FTIR). For the samples doped with Eu(TTFA)3 or Sm(TTFA)3, the typical fluorescence spectra of Eu3+ or Sm3+ emissions are detected, respectively. However, for the samples co-doped with Eu(TTFA)3 and Sm(TTFA)3, photoluminescence (PL) shows the absence of Sm3+ emission and reveals the obvious energy transfer from Sm3+ ions to Eu3+ ions. Note that there are energy transfer processes between the ligands and Eu3+ or Sm3+. Therefore, multiple energy transfer processes are achieved within the hybrid spheres. These energy transfer processes maximize the possible fluorescence emission of Eu3+ ion. The lifetimes of the hybrid spheres are also measured. The RE complex/SiO2 hybrid spheres described in this paper may find promising applications in optical devices and materials science.
The research of antofluorescence of the live tissue starts to be used in the disease diagnoses and prevention in recent years. The laser scanning confocal microscope has always played a great role in the autofluorescence research in biomedical field. As the technology of imaging spectrometer got successfully used in the remote sensing fields, microscopical imaging spectrometer for biomedical analyses emerged after the integration of imaging spectrometer and laser scanning confocal microscope. It can get the autofluorescence image and the spectral information of the sample simultaneously, this will supply more information to the diagnoses for difficult diseases. In this paper the principle of a Linear-array Pinholes Laser Scanning Confocal Microscopical Imaging Spectrometer (LP-LSCMIS) developed by the authors is proposed. It can be widely used in the autofluorescence detection of the live tissue in the body, such as the gastric, kidney, etc. The effect of off-focus of linear-array pinholes on microscopical imaging spectrometer subsystem in this device is mainly analyzed. The spatially resolution of fluorescence imaging and the modulation depth of autofluorescence spectrum in the live tissue is affected by the off-focus according to our research. We analyse the modulation depth of the interferogram thinking of the factor of off-focus.
As a relay optical component, fiber optic taper has become more important and more widely used in the integrated taper assembly image intensified sensors for military and medical imaging application. However, the method for evaluating the quality of output images from the fiber optic taper is few. In this article, the Modulation Transfer Function (MTF) is introduced and measured to evaluate the image quality of fiber optic taper. Because fiber optic taper is of a mosaic array architecture, there are some new problems need to be resolved in defining MTF of it. And there also should be some special requirements in MTF measurement. Two methods including edge scanning and point imaging analyzing are introduced in measuring MTF of fiber optic taper, in which the incident light, scanning step and scanning range are specially limited. Experiments show that the results of the measurements consist with the theoretical analysis simulated by computer. And the spatial averaged MTF of fiber optic taper has been gotten by two means. It is concluded that the MTF value measured by point imaging is always some higher than measured by edge scanning, because the point imaging is more weakly effected by the fiber arrangement in taper.
In this paper, rare earth (Eu3+, Sm3+) binary chelates with hexafluoroacetylacetone(HFA), thenoyltri fluoroacetylacetone (HTTA), and dibenzoylmethide(DBM) were synthesized, respectively. Then the fluorescence properties of the chelates Eu(TTA)3, Eu(HFA)3, Eu(DBM)3, Sm(TTA)3, Sm(HFA)3 and Sm(DBM)3 in benzene were investigated. It was found that the fluorescence peak at 614nm related to the transition of 5D0->7F2 of Eu3+ was the strongest in Eu(TTA)3. Based on this, the concentration (between 0.05-0.5wt.%) influence of Eu(TTA)3 on fluorescence intensity in Eu(TTA)3-doped PMMA was studied. The results showed the fluorescence intensity increases with Eu(TTA)3 concentrations except that no fluorescence peak was detected for 0.05wt.% Eu(TTA)3-doped sample. However, the sharp fluorescence peak accidentally occurs at 614nm when 0.04wt% Eu(TTA)3 and 0.04wt% Sm(TTA)3 were co-doped in PMMA. Further investigation revealed that similar fluorescence enhancement occurred for all samples co-doped with Eu(TTA)3 and Sm(TTA)3. It indicated that Sm(TTA)3 has a strong sensitization effect on the fluorescence of Eu(TTA)3. Besides, it was also found the sensitization effect could be decreased with the increasing Sm(TTA)3 concentrations for a fixed Eu(TTA)3-doped content. Finally, two possible energy transfer mechanisms were analysed.
When the size of a needing scene is beyond the scope of an optical sensor, it is difficult to take the whole scene at the same time. In this case, the needing scene can be captured by several optical sensors at one time, the overlapped images can be taken. Using the images, the whole scene is reproduced. This paper presents a robust image mosaics method that employs wavelet transform technique. The new developed registration and fusion algorithm implemented automatically and simultaneously without known camera motion and focal length. Wavelet transform guarantees not only a global optimal solution, but also scale and transform invariance for image alignment. This feature guarantees that the scheme has higher performance than the traditional mosaic techniques. In the same time, the hardware structure and the software designing principle of the Image Mosaics System (IMS) based on the Digital Signal Processor are expounded. To further improve the image mosaics quality, an image enhancement approach is also employed. In the paper, the concept, algorithm and experiments are described. The test results showed that the IMS is efficient and accurate for acquisition of seamless mosaic of the overlapped images, and at the same time, is adaptive to the real-time requirements. An adaptive resolution, seamless and a wide field of view image can be acquired.
Plastic optical fiber (POF) can be taken as short distance transmission system medium for replacing of coaxial cable because of its many excellent characteristics. The bandwidth characteristics of graded-index POF is strongly influenced by the differential mode attenuation (DMA). In this paper, a comprehensive bandwidth calculation model of POF is given. The analytical expression of DMA is fitted by eighth order polynomial from the experimental data, and is used for the calculation of fiber bandwidth. The frequency response function of graded-index plastic optical fiber(GIPOF) is calculated numerically under selective mode excitation condition, and the fiber bandwidth is studied. The calculated results indicated that the selective mode excitation could improve efficiently the fiber 3dB bandwidth. The influence of light source linewidth on fiber bandwidth is also investigated.
Fiber optic taper has been used more and more widely as a relay optical component in the integrated taper assembly image intensified sensors for military and medical imaging application. In this paper, the transmission characteristic of energy in the taper is analyzed, and following the generalized definition of the modulation transfer function for sampled imaging system, a spatial averaged impulse response and a corresponding MTF component that are inherent in the sampling process of taper are deduced, and the mathematical model for evaluating the modulation transfer function of fiber optic taper is built. Finally, the dynamic and static modulation transfer function curves simulated by computer have been exhibited.
It is very difficult to measure the distance of a moving point target which is not cooperative for detecting in the remote sensing field, because that the point target has no geometrical dimensions and textures can be used and is easy to be missed. In this paper, a new algorithm based on the image sequence and the nonlinear regressive filtering algorithm is proposed, in order to determine the 3-D parameters of the moving point target in an efficient passive way. And a new multi-channel optical imaging system is designed, which is composed of a high- resolution center imaging system and four low-resolution sub-imaging systems. By the geometrical relationship of the four sub-imaging system, the initial values of the nonlinear regressive filtering algorithm for estimating can be obtained easily. Finally, the experiments of the proposed algorithm have been done on a real system, and the results proved that the algorithm could passively obtain the 3-D parameters of the moving point target efficiently. Furthermore, in the estimating procedure, the character of the nonlinear regressive filtering algorithm saves lots of memory units and reduces the computing quantity.
Grating waveguides were fabricated based on Nano-imprint lithography (NIL) and silicon mould replication techniques in this paper. Using a silicon mould repeatedly, low-cost grating waveguides can be fabricated in batches. The proposed grating waveguide is soft enough to be an optical sensing element for catheter, smart skin sensing unit of micro-robots, and etc. Further, these grating waveguides were coupled with optical fibers for its convenient applications. There are two main parts in this paper, the first is to fabricate a suitable silicon mould for replication of grating waveguides, and the second is to reprint grating waveguides by using the fabricated silicon mould. Basing on NIL technology proposed in 1995 by Professor Stephen Y Chou, silicon moulds of grating waveguides with pitch 0.75μm were fabricated on (100) silicon wafer. There are several methods to carry out the replication process, such as Hot embossing, Injection moulding, UV-replication and Casting moulding method. In this work, UV-replication and Casting moulding method was selected to fabricate the grating waveguide structures for its easy control and high fidelity. There are two associated challenging issues in the replicating process; one is to prevent the replicated materials from sticking to the mould for easily peeling off the replicated structure, the other is to find matching materials for the waveguide core and cladding to guarantee the optical characteristics of the grating waveguide. Grating waveguides with core size 4μm×20μm were fabricated successfully in this paper that demonstrated the novel idea of this paper.
A new concept that is the Discontinuous Frame Difference in image sequences is proposed in this paper, and is applied to the Optical Flow Algorithm. The modified Optical Flow Algorithm overcomes the shortcoming of the traditional Optical Flow Algorithm that cannot detect the small moving target whose moving displacement is less than one pixel between two continuous frames. The infinite norm of the Discontinuous Frame Difference Vector is used to preprocess the image sequences to get rid of most of pixels taht are not the pixels of the moving target. And then the instantaneous velocities of the pixels remained by preprocessing is calculated by the Optical Flow Algorithm. If the pixels in an area have the moving continuity and consistency, a moving object is determined. For the preprocessing is able to get rid of most of pixels, the calculation quantity of the Optical Flow is reduced greatly. But the preprocessing is probably to lose some candidate pixels of the moving target, so the Gray Intensity Analysis is used to find these pixels back again. The Discontinuous Frame Difference Optical Flow Field Algorithm can be composed of the parallel structure system, which can detect different kinds of moving objects with different velocities. The experiment result proves the effectiveness of the method.
In this paper, a measuring method utilizing Modulation Transfer Function (MTF) to evaluate the imaging performance of fiber optical plates, is proposed. As a kind of relay optical component in optical imaging systems, optical fiber transfer image plates have become more important and more available. By digital simulating the discrete MTF values, algorithm for MTF measure of fiber plates is studied. And MTF experimental results for the performance evaluation of fiber plates with knife-edge effect compared CCD test, are also discussed.
A micro-array imaging system with multi-channel, parallel processing is proposed in this paper. Compared with the single- aperture imaging system, the array imaging system has some advantages- wider view field to prevent losing target, and higher sensitivity for moving as the compound eyes of insects. Utilizing the moving sensitivity, one is able to measure the properties of moving object, like speed, acceleration, direction and so on. A microlens array plays an important role in the micro-array imaging system. Based on the system construction and the visual principle, several experimental and evaluating results are introduced. Meanwhile, new approaches of image capturing and data processing to solve the contradiction between view field and resolution are discussed initially.
In this paper, a novel beam shaping configuration for confocal imaging system is presented, which relies on the reversal effect of axicons-component along with the Gaussian distribution of laser beam. The Gaussian peak of incident light coming into the one side of such component at the central part, may go out from the other side of component near the peripheral part, conversely, the skirt of Gaussian beam combing into the peripheral part may go out of the central part. Thus, the beam shaping is obtained with the component of cone axicons and therefore the superresolution can be realized in a confocal imagin system. Meanwhile, the energy loss is much diminished and the optical power deserted hitherto is recovered.
The parallel confocal method for detecting whole-field 3-D surface topography is proposed in this paper. For the realization of the method, in the confocal optical system, the micro-optic array component composed of a microlens array and a matched pinhole array has been introduced to produce a symmetrical micro-array source. Thus, it can be performed to paralleling measure the tested object surface at the same time with the multi-detecting light beams. The method fully and successfully shows the advantage of optical parallel processing in the confocal system, and overcomes the problem of a long-period scanning required by the original confocal system, from which deviations occur. Meanwhile, some experimental results with the parallel confocal detecting method are presented in the paper.
A new method for replicating microstructure elements is presented. The principle and technological process of the method are introduced. For one polymer, deep binary relief grating on quartz substrate is replicated by using this new method and the relief-transfer efficiency and transparency are measured. The results show that the replicas are of high fidelity of profile and are suitable for practical applications.
We introduce a new type of microlens arrays, which has a continuous relief of parabolic section profile and has no dead area. Because of its continuous relief, this type of microlens arrays has much less chromatic aberration compare to kinoform microlens arrays, and has no dead area problem of other type of refractive microlens arrays. The method called `moving-mask' to fabricate such microlens arrays is presented and the experimental results are also given.
The stability of hologram recorded in DC-MBDCG plate, a new kind of gelatin recording material sensitized with double- sensitive-center method (reported lately by us), is investigated in this paper. The results show that the holograms recording in DC-MBDCG become more stable than in common dichromated gelatin. So, we believe the double- sensitive-center method is effective not only for system sensitizing but also for hologram stability enhancing. The mechanism of the results is discussed herein as well.
Utilizing micro-optics components, a new technique for measuring the properties of optical system is developed in this paper. The micro-optics components have been composed of a microlens array and a matched array of pinholes. Passing through the micro-optics array components, the light beam projects into the tested optical system, and is detected as a power spectrum by CCD plane array at last. By processing and analyzing the information from CCD detector, some main properties of tested optical system can be obtained. The experimental results are satisfactory due to the 2D plane symmetry and high power efficiency of the micro-optics array components.
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