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The azimuthal angle relation for obliquely excited standing-wave surface plasmon is analytically studied in detail and thereby a near-field spatial frequency filtering model is proposed, in which the azimuthal angle relation and criterion similar to Heisenberg uncertainty principle are combined to describe the spatial resolving power of surface plasmon self-interference virtual probe imaging system. It is revealed that the incidence coupling possesses spatial anisotropy due to polarization modulation, and the mechanism for spatial resolution degradation is the compression of spatial frequency bandwidth in the near-field domain.

A simple and effective method for fabricating high fill-factor aspheric microlens array using digital maskless lithography is reported. The method use the contour planes of the designed profile as binary image, which replace physical mask by DMD display. On the lithography system, the dose accumulated over multiple exposures and the exposure dose reconstructed in wafer, then the designed profile developed. Aspheric microlens arrays with hexagonal base and square base were produced by the method, and they were gapless at each microlens periphery, so the microlens array with fill-factor of 100%.

In this paper, a planar polymer sub-wavelength grating whose period structure is modulated by different refractive index is proposed. The guided mode resonant of the proposed grating is analyzed with effective medium theory and the eigenvalue equation of the thin film waveguide, and the reflectance properties of the grating are simulated with rigid coupled-wave analysis. The reflectance property shows obvious polarization dependent. The influences of the grating period, thickness and the incident angle on the resonant wavelength are also analyzed. It is shown that the resonant wavelength shows redshift with the increase of grating period, dual resonant peaks occur when the grating thickness is of some certain values, and the resonant peak of normal incidence will split into 2 peaks on the condition that oblique incidence. This planar polymer sub-wavelength grating may find application in filters, polarization elements, reflectors and so on.

A new model of integrative ommatidium for bionic optical compound eye is proposed in this paper. The structure of the integrative ommatidium for bionic optical compound eye is constructed. The ray matrix of the integrative bionic optical compound eyes is deduced detailedly with ray-matrix method, and the principle points and focal points of the integrative bionic compound eye are calculated. The ray matrix of the integrative bionic compound eye is related tightly with the length of the cylinder waveguide part, so as the image principle point and the image focal point. The length of the cylinder waveguide has no influence on the position of the object principle point and the object focal point of the integrative bionic compound eye. However, difference length of the cylinder waveguide will lead to different positions of the image principle point and image focal points. Self-focus effect can be employed to fabricate the integrative bionic optical compound eyes with some nonlinear optical polymer.

This paper presents a facile and effective method to fabricate microlens array in polydimethylsiloxane (PDMS). The microlens array model is fabricated in photoresist via digital maskless grayscale lithography technique and the replica molding technique is used to fabricate PDMS microlens array. A convex PDMS microlens array with rectangular aperture and concave PDMS microlens array with hexagonal aperture are fabricated. The morphological characteristics of the microlens arrays are measured by microscope and 3D profiler. The results indicate that the profiles of the PDMS microlens arrays are clear and distinct. This method provides a simple and low-cost approach to prepare large area, concave or convex with arbitrary shape microlens array, which has potential application in many optoelectronic devices.

A novel method is proposed to fabricate continuous relief micro-optic elements using real-time maskless lithography technique based on digital mirror device (DMD). To evaluate the method, aspheric and spheric micro-lens array was fabricated by following the proposed principle. Firstly distribution of the required exposure dose of lens array was obtained and sliced into a number of contours of equal proportions. Then the contour planes instead of virtual masks were converted into binary image. On the lithography system, the dose accumulated over multiple exposures and the required exposure dose profiles were reconstructed. Finally in the photoresist layer, virtual profiles of lens array were formed, consistent with the original designed elements. The method is feasible and reliable for the fabrication of arbitrary continuous relief micro-optic elements.

Three methods of quantization are employed to design quantized GRIN lens, whose optical properties are expected to approach that of the ideal one. Detail operations for quantization are described in this paper. In order to verify and check the validities of the methods, full-vector BPM method has been carried out to simulate the focus properties of the quantized GRIN lens, and that of the ideal one for comparison. Analysis indicates that all the quantized GRIN lenses perform similar optical properties as the ideal one does. Thereinto, the performances of the GRIN lens quantized equally according to n(r) and the one quantized with hybrid method are quite close to that of the ideal GRIN lens. The methods of quantization presented in this paper can be as the reference framework for designing expected GRIN lenses before fabricating them with a simpler process of definite parameters.

Electron excitated temperature is one of the most important parameters of Ar plasma-arc. Emission spectrum diagnosis technique has been widely used in the research of electron temperature for its easy operation and small disturbance, where the spectral analysis is the focused content. However, there is still no report about spectral analysis of Ar plasma-arc under different experimental parameters. In this paper, we use the fiber spectrograph for collecting the spectral distribution of the Ar plasma-arc. Then we change the experimental parameters, analyze the influences of the electric current and air current on the spectral distribution. The results show that all these experimental parameters have great influence on the characteristics of spectrum such as spectral line intensity, background signal, etc. It is found that electric current below 100 A, air current below 10 A/min are good for spectral analysis, while two different wavelengths of 696.5 nm and 763.5 nm are suitable for temperature field testing and analyzing. This research provides a good foundation for density field, pressure field and velocity field testing and analyzing, it is also beneficial for us to understand the inner mechanism of Ar plasma-arc.

In the paper, the characteristic of imaging with digital micro-mirror device (DMD) illuminated by a partially coherent light is discussed using Abbe's method. When a mask is sampled by DMD, the intensity in the substrate is modulated by sinc function and cut off by pupil function, according to oblique illumination theory and Fourier transform property of exponential function, a fast partially coherent imaging algorithm for DMD-based dynamic projection photolithography is proposed to combine Hopkins's method with Abbe's method. In the algorithm, the transmission cross coefficient (TCC) matrix of DMD projection photolithography is constructed as two-matrix multiplication according to illuminate source points. The new development presented in this paper utilizes matrix multiplication technique to speed up the computation of TCC matrix by tenfold on an average, which is beneficial to real time mask shift and mask optimization in DMD-based gray-tone photolithography.

During laser spectroscopic measurement, a part of laser energy will be converted into heat in the processes of excitation and light emission. Temperature monitoring can help to evaluate such nonradiative process. Upconversion luminescence of phosphor Y 2 O 3 :Er,Yb under laser excitation at 980 nm was investigated in this work. Point temperature of the phosphor was monitored using the fluorescent intensity ratio (FIR) technology. Laser induced temperature rising was identified by comparison with a theoretically ideal temperature calibration function: lnR = 3.1738–1167/ T . The monitored temperature of laser heating rises monotonically with increasing laser power. Circumstances around heating point will modify the calibration function, but the linear slope of lnR ~ 1/ T is constant.

In this paper, twin-object-beam electronic speckle interferometry is used to study the longitudinal corrosion of carbon steel. The displacement expression of this technique is deduced and optical fibers are used to reduce the influence of the optical system and improve the quality of speckle pattern. Twin-object-beam electronic speckle interferometry cannot only quantitatively cipher out off-plane displacement as a result of corrosion, but also estimate the change of corrosion speed.

The technique of using computer-generated hologram (CGH) for 2-D and 3-D display based on virtual optics was researched widely. A new way, modified peak signal to noise ratio (PSNR) method was used to assess 3-D image quality reconstructed by CGH, and an iterative arithmetic was proposed to synthesize CGH perfectly. Furthermore, in the paper a novel way to encrypt 3-D information was proposed. Simulation experiments showed that CGH was an effective encryption technique, and Modified PSNR was a proper definite quantity analysis method for 3-D imaging.

We present the digital-division-mask technique for the first time to solve the problem of decline in transverse resolution, which is caused by using digital micro-mirror device (DMD) to make binary optical elements (BOEs). One high-frequency gray-tone mask can be divided into several low-frequency masks by fixed or variable low-frequency period sampling. And the superimposed lithography effect of these low-frequency masks in the spatial or temporal domain is the same as that of the original high-frequency gray-tone mask. The paper firstly analyzes the digital-division-mask technique in theory and describes the feasibility and advantages. Then taking the diffractive surface fabrication of refractive–diffractive hybrid lens as an example, we conclude that the digital-division-mask technique improves the edge sharpness of lithography pattern, and enhances the diffractive efficiency of BOEs by experiment.

This paper presents a technique to diagnose the three-dimensional temperature fields of arc plasma with orthographic and double-wave spectral tomography. First, the system with two orthographic directional CCD image real-time cameras is adopted to get the information of spectrum intensity related to the gray scale of arc plasma. Second, the improved computerized tomography iterative technique which accords with the least-square and max-entropy criterions, simultaneously, has been used to reconstruct the distributions of different emission coefficients, which shows superiority to the conventional tomography algorithms. Finally, based on plasma physical theory, the spectrum relative-intensity method has been used to reconstruct the distribution features of three-dimensional temperature fields. The experimental results have shown the effectiveness of this measurement system with high-precision and real-time ability. (C) 2009 Elsevier Ltd. All rights reserved.

For reconstructing based on incomplete projection data, an improved max-entropy reconstruction algorithm is presented in this paper. Both least-square and max-entropy are used in this algorithm, and the penalize-function method is used in iterative processing. The numerical simulation of three different tested fields has been done. Compared with conventional three-dimensional reconstruction algorithms, this novel algorithm has a higher reconstruction precision as well as a better astringency, particularly in the case of easy tested field. For the reconstruction of asymmetric complicated tested field, it also has a good result if suitable projective direction and iterative times can be choosen. Finally, the application of this novel algorithm to diagnose the temperature field of arc plasma is presented.

Two theoretical problems associated with the measurement of temperature or strain from the normalized power of Brillouin signal in a distributed fiber sensor are studied. One problem is the position-dependent of the coefficient relating the Brillouin power to the local temperature or strain. The other problem is the backward infection of the defect (local temperature or strain change). These two problems will degrade the measurement accuracy of a distributed Brillouin fiber sensor by changing the distribution of pump power. To eliminate these two problems, new reference functions are proposed to normalize the Brillouin signal. Simulation results by using fourth-order Runge–Kutta algorithm show that these new reference functions can eliminate the influence of these two problems on distributed Brillouin fiber sensor.

During selective laser sintering (SLS), transient temperature has direct effect on prototyping mechanism and quality. The infrared thermograph non-contact testing method is proposed in this paper. The testing results are compared with numerical simulation results. The results indicate that the on-the-spot survey trend agrees with the simulation trend, and the proposed method provides a steady experimental base for selecting sintering parameters and calculating thermophysical parameters reasonably.

The digital virtual mask technique based on digital micro-mirror device (DMD) is applied in the field of micro-engineering such as the machining of micro-optical elements. On the premise of universality, the error of digital virtual mask technique is theoretically deduced, combined with the functional diagram used in the experiment. Based on the expanding application of Rayleigh's criterion, the reference of calculating the error of the lithography mask technique is given. And the method of improving the technique is also discussed.

The measurement of Brillouin frequency shift in fiber sensor with edge technique is proposed. The relation between measurement accuracy of Brillouin frequency shift and signal to noise ratio (SNR) is analyzed. The edge technique is realized by choosing the frequency of electrical local oscillator and adopting lowpass filter (LPF). The system with edge technique measures the frequency shift by the edge signal rather than the maximum signal, because the edge signals are higher sensitive to the variation of frequency than the maximum signal. From the calculated results, the SNR required is 37 dB to achieve frequency shift resolution of 0.5 MHz by using double-edge technique, comparing with 65.1 dB in conventional detection system measuring the maximum signal, edge technique improves the measurement accuracy of Brillouin frequency shift greatly. In addition, by choosing the frequency of electrical local oscillator, the highest measurement accuracy of Brillouin frequency shift is achieved.

In this paper, digital mask technique is presented, and a high-quality projecting reduction lithography system has been set up successfully. The core device of digital mask technique is digital micromirror device (DMD) which belongs to one of the electrically addressed spatial light modulators. The output image of DMD can be equivalent to a gray-scale mask of high precision, which can control the exposure precisely. If it is combined with a high-quality projecting reduction system, the fabrication of submicron diffractive optical elements can be realized successfully. The overall design of the system is described in detail, and some diffractive optical element masks are fabricated. Experimental results verify that the system is feasible. In the end, system characteristics and system error are summarized.