Off-axis mirror based optical system design for circularization, collimation, and expansion of elliptical laser beams

In this paper, we present two optical system design methods for beam circularization, collimation, and expansion of semiconductor laser output beam for possible application in LIDAR systems. Two different optical mirror systems are investigated: an off-axis hyperbolic/parabolic mirror system and an off-axis parabolic mirror system. Equations specific to these mirror systems are derived and computer package programs such as ZEMAX and MATLAB are used to simulate the optical designs. The beam reshaping results are presented.     

Single aspherical lens for deastigmatism, collimation, and circularization of a laser beam

An astigmatic and elliptically diverging laser beam generated by a gain-guided laser diode can be converted into a collimated and circular beam with a single specially designed lens. The designed lens also corrects for the astigmatism present in the laser diode. The input surface of the lens has a different concave and convex aspherical profile in the transverse and the longitudinal direction, respectively, for astigmatism correction. The output surface possesses a convex aspherical and a straight profile in the transverse and the longitudinal direction, respectively, for collimation and circularization of the final output laser beam.     

Throughput comparison of microscope objectives and custom lenses for laser diode output beam collimation

The efficiency with which various microscope objectives and custom lenses collimate laser diode emission has been measured. Throughput efficiencies for diode operation above and below threshold are presented.     

A higher-order theory for functionally graded beams based on Legendre's polynomial expansion

In this article a higher-order theory for functionally graded beams based on the expansion of the two-dimensional (2D) equations of elasticity for functionally graded materials into Fourier series in terms of Legendre's polynomials is presented. Starting from the 2D equations of elasticity, the stress and strain tensors, displacement, traction, and body force vectors are expanded into Fourier series in terms of Legendre's polynomials in the thickness coordinate. In the same way, the material parameters that describe the functionally graded material properties are also expanded into Fourier series. All equations of the linear elasticity including Hooke's law are transformed into the corresponding equations for the Fourier series expansion coefficients. Then a system of differential equations in terms of the displacements and the boundary conditions for the Fourier series expansion coefficients are obtained. In particular, the first- and second-order approximations of the exact infinite dimensional beam theory are considered in more detail. The obtained boundary-value problems are solved by the finite element method with MATHEMATICA, MATLAB, and COMSOL multiphysics software. Numerical results are presented and discussed.     

Physically based expansion on conformal Gaussian beams for the radiation of curved aperture in dimension 2

A Gabor-based Gaussian beam expansion to describe the radiation of electric and magnetic currents on a regular curved interface in dimension 2 has previously been proposed. This expansion represents the radiated fields as a superposition of elementary beams, the conformal Gaussian beams, for which an analytical formulation has been developed. In the context of industrial design and optimisation of radomes, computation time is of primary importance. Therefore a new pragmatic approach to represent the radiated fields on a smaller set of conformal Gaussian beams is proposed. This new expansion does not use Gabor frames but is based on the physical properties of the configuration. Few numerical experiments are presented to evaluate its performances.     

Optical amplification of diffraction-free beams by photorefractive two-wave mixing and its application to laser Doppler velocimetry

The Fraunhofer diffraction pattern of a narrow annular slit is recorded holographically to generate a beam that approximates a diffraction-free Bessel beam. The experimental limitations resulting from the annular-slit parameters such as the opening width and the transmission coefficient are discussed. The reconstructed Bessel beam is amplified by two-wave mixing in a photorefractive crystal. Thus the efficient conversion of a relatively large beam with a constant (or Gaussian) intensity distribution into a nondiffracting beam is achieved entirely by direct physical interference. We show that diffraction-free beams reproduced and amplified in this way can be applied to the measurement of the velocity of small objects by the use of the laser Doppler technique. In addition, the advantages of Bessel beams, especially in measuring the velocity of solids, are discussed.     

An efficient design procedure for flexural strengthening of RC beams based on ACI 440.2R-08

The technology of using FRP composites to strengthen concrete members has proven its effectiveness over the years. Accordingly, design guides have been developed to aid engineers in applying this technology. ACI 440.2R-08 is one of the major design guides used in the US and elsewhere in the world. Due to the existence of two major sectional tensile forces in steel and FRP as well as the likelihood of different failure modes, the ACI 440.2R-08 flexural strengthening design procedure leads to an iterative process. In this study an efficient design procedure that eliminates the need for iterations is developed. The FRP area determined from the developed design procedure has been shown to correlate very accurately to the exact area obtained iteratively according to the ACI 440.2R-08 document. Several design examples are solved to illustrate the potential use of this efficient and simple design procedure in expediting the current design computations.     

基于成像球光强测量系统的光学设计

提出一种新的快速测量空间光强分布的方法,完成基于该方法测量系统的光学系统设计,并对光学系统的关键器件进行设计.利用Matlab编程和Solidworks三维建模得到自由曲面反射镜面型,Zemax光学软件设计优化得到双高斯物镜.光线追踪仿真软件LightTools对测量系统进行模拟仿真,验证系统的可行性,并对该构架下测量系统最小角分辨率和动态范围的关键性能指标进行分析.结果表明,设计的基于成像球的测量系统可实现空间光强分布测量.     

Shear design of reinforced concrete beams, slabs and walls

The paper presents the background to the shear design provisions for reinforced concrete beams and slabs used in the Australian practice. Correlation of design equations with experimental results are given. The design provisions are illustrated by examples. The importance of shear strength in the design of structural walls is discussed. A new expression to calculate the shear strength of walls is presented.     

USB2.0的激光光绘机接口系统设计

针对激光光绘机数据传输系统在PCI总线传输模式下难以维护与升级的缺陷,提出了一种新的基于USB2.0协议的激光光绘机接口技术.该技术充分利用了USB2.0高速的数据传输特性,将高速FPGA器件与USB控制芯片CY7C68013有机的结合,使激光光绘系统的使用更灵活、更方便,并有效地降低了设备的成本.介绍了系统的工作原理、硬件设计和相应的软件实现,并通过实验测量分析,证实该技术将完全能够取代PCI总线在激光光绘机接口系统中的应用.     

System for the design, manufacture, and testing of custom lenses with known amounts of high-order aberrations

Now that excimer laser systems can be programmed to correct complex aberrations of the eye on the basis of wave-front measurements, a method is needed to test the accuracy of the system from measurement through treatment. A closed-loop test method was developed to ensure that treatment plans generated by a wavefront measuring system were accurately transferred to and executed by the excimer laser. A surface was analytically defined, and a Shack-Hartmann-based wave-front system was used to formulate a treatment plan, which was downloaded to an excimer laser system. A plastic lens was ablated by the laser and then returned to the wave-front device, where it was measured and compared with the analytically defined wave-front surface. The two surfaces agreed up to 6th-order Zernike terms, validating the accuracy of the system.     

Extensions to a lens design program for the ray-optical design of waveguide lenses and prism couplers

Abstract

The design of integrated optical lens systems requires special software because such systems contain both three-dimensional and twodimensional elements (e.g. bulk prisms and planar waveguide lenses), and the waveguides are often anisotropic. We extended the popular optical computer-aided design program OSLO SIX so that it can evaluate and optimize systems that contain coupling prisms and planar waveguide lenses. We describe our software extensions and through examples we demonstrate their usage and benefits. We confirm our computations by measurement results. Finally, we present a ray-optical interpretation of transverse image line inclination and a method for its elimination.     

基于AVR单片机的激光电源闭环控制系统设计

为使激光器稳定输出,采取控制驱动电流和温度的设计方案,基于AVR单片机设计一种半导体激光器驱动电源控制系统。采用负反馈原理和闭环控制思想分别实现对驱动电流和温度的控制,从而完成高性能半导体激光器的研制。采用AVR作为主控制芯片,以模数、数模等转换芯片作为其外部扩展电路。为保护激光器和其他易损元件,整个驱动电路具有抗电冲击和过流保护等多种功能。通过实验证明:该系统能使激光驱动电路1 h内偏差为0.02%,稳定性良好,温度控制偏差为±0.005℃。该电源控制系统可靠性高,可移植性强,具有较好的应用前景。     

Optical levitation and translation of a microscopic particle by use of multiple beams generated by vertical-cavity surface-emitting laser array sources

An optical levitation and translation method for a microscopic particle by use of the resultant force induced by multiple light beams is studied. We show dependence of the radiation pressure force on the illuminating distribution by numerical calculation, and we find that the strongest axial force is obtained by a specific spacing period of illuminating beams. Extending the optical manipulation technique by means of vertical-cavity surface-emitting laser (VCSEL) array sources [Appl. Opt. 40, 5430 (2001)], we are the first, to our knowledge, to demonstrate levitation of a particle and its translation while levitated by using a VCSEL array. The vertical position of the target particle can be controlled in a range of a few tens of micrometers with an accuracy of 2 microm or less. The analytical and experimental results suggest that use of multiple beams is an effective method to levitate a particle with low total illumination power. Some issues on the manipulation method that uses multiple beams are discussed.     

一种基于粒子滤波的任意姿态头部椭圆轮廓跟踪方法

结合粒子滤波思想,给出了一种适用于复杂背景和较远距离下跟踪任意姿态人体头部椭圆轮廓的方法.该方法采用双重随机采样策略,即在预测值附近通过均匀采样产生初始粒子以保证其多样性,在权值更新后对具有较高权值的粒子进行高斯采样以保证重采样过程的快速收敛性.在权值更新过程中,利用分块颜色直方图实现模板椭圆同粒子椭圆之间的颜色匹配,利用最大梯度距离测度(DMG)对粒子椭圆的边缘拟合程度进行度量,最后利用D-S证据思想对上述两种测度进行融合.实验结果不仅验证了此方法对于复杂背景和人体头部的任意姿态具有较强的鲁棒性和有效性,而且证实,此方法也适用于相对较远的距离范围.     

Optical design and evaluation of a three-dimensional imaging and ranging system based on time-correlated single-photon counting

The design and operation of a noncontact surface profilometry system based on the time-correlated single-photon-counting technique are described. This system has a robust optomechanical design and uses an eye-safe laser that makes it particularly suitable for operation in an uncontrolled industrial environment. The sensitivity of the photon-counting technique permits its use on a variety of target materials, and its mode of operation does not require the continual presence of an operator. The system described has been optimized for a 1-25-m standoff, has a distance repeatability of <30 microm, and has a transverse spatial resolution of approximately 60 microm at a 2-m standoff and approximately 400 microm at a 13-m standoff.     

Optical sensors for vapors, liquids, and biological molecules based on porous silicon technology

The sensing of chemicals and biochemical molecules using several porous silicon optical microsensors, based both on single-layer interferometers and resonant-cavity-enhanced microstructures, is reported. The operation of both families of sensors is based on the variation of the average refractive index of the porous silicon region, due to the interaction with chemical substances either in vapor or liquid state, which results in marked shifts of the device reflectivity spectra. The well established single-layer configuration has been used to test a new chemical approach based on Si-C bonds for covalent immobilization of biological molecules, as probe, in a stable way on the porous silicon surface. Preliminary results on complementary oligonucleotide recognition, based on this technique, are also presented and discussed. Porous silicon optical microcavities, based on multilayered resonating structures, have been used to detect chemical substances and, in particular, flammable and toxic organic solvents, and some hydrocarbons. The results put in evidence the high sensitivity, the reusability, and the low response time of the resonant-cavity-enhanced sensing technique. The possibility of operating at room temperature, of remote interrogation, and the absence of electrical contacts are further advantages characterizing the sensing technique.     

Intracavity generation of radially polarized CO2 laser beams based on a simple binary dielectric diffraction grating

We present experimental results on the intracavity generation of radially polarized light by incorporation of a polarization-selective mirror in a CO(2)-laser resonator. The selectivity is achieved with a simple binary dielectric diffraction grating etched in the backsurface of the mirror substrate. Very high polarization selectivity was achieved, and good agreement of simulation and experimental results is shown. The overall radial polarization purity of the generated laser beam was found to be higher than 90%.     

激光防护光学材料的设计及性能研究

随着激光设备的不断发展，自动化程度的不断提高，它对人眼及各种电子装置的干扰、损伤等的威胁也越来越大，激光防护越来越受到各国的重视。报道了激光防护共轭功能高分子的分子设计，合成系列共轭高分子，采用FT-IR、^1H NMR、UV、GPC和TGA对分子结构和热性能进行表征，测试了高分子的光限幅和非线性光学性能，讨论了高分子材料热性能增强与光限幅产生的机理以及分子结构与高分子光学性能之间的关系。