A simple optical method for the measurement of glass wool fiber diameter

An optical method for measuring glass wool fiber diameter has been proposed and discussed from the viewpoint of practical use. The method is based on both light scattering and light reflection on the glass wool. The method can measure the mean fiber diameter, d, in the area illuminated by laser light in realtime. The accuracy of the method, i.e., the dimensional resolution, was found to be about 0·7 μm within the diameter range of d7·0 μm.     

ATMOS (ATM optical switching)—system perspective

The expected traffic growth from new broadband services will require network capacities that can be beneficially provided by optical WDM transport networks. Optical packet techniques are essential for large networks to provide flexibility and granularity. A layered network architecture with a transparent optical layer and optical packet layers has been elaborated. Four switching concept options for large optical ATM switch fabrics in the public network and small access nodes are presented. The technology for the related key functions of space and wavelength switching was developed in the RACE ATMOS project and the feasibility of concepts and technologies was verified in four system demonstrators.     

An optical system for measuring nitric oxide using spectral separation techniques

An optical sensor based on differential absorption spectroscopy for real-time monitoring of industrial nitric oxide (NO) gas emission is described. The influence of gas absorption interference from sulfur dioxide (SO₂) in the environment was considered and a spectral separation technique was developed in order to eliminate this interference effect. The absorption spectrum of SO₂ around 226 nm was evaluated by the SO₂ concentration obtained using the experimentally recorded absorption spectrum around 300 nm. The absorption spectrum of NO around 226 nm was obtained by subtracting the absorption of SO₂ from the integral absorption spectrum of SO₂ and NO. The concentration measurements were performed at atmospheric pressure. The technique was found to have a lower detection limit of 0.8 ppm for NO per meter path length (SNR=2) and be immune from the influence from SO₂ on the NO measurement. The sensor based on this technique was successfully employed for in situ measurement of SO₂ and NO concentrations in the flue gas emitted from an industrial coal-fired boiler.     

Large area SiC substrates and epitaxial layers for high power semiconductor devices — An industrial perspective

We review the progress in the industrial production of SiC substrates and epitaxial layers for high power semiconductor devices. Optimization of SiC bulk growth by the sublimation method has resulted in the commercial release of 100 mm n-type 4H-SiC wafers and the demonstration of micropipe densities as low as 0.7 cm⁻² over a full 100 mm diameter. Modelling results link the formation of basal plane dislocations in SiC crystals to thermoelastic stress during growth. A warm-wall planetary SiC-VPE reactor has been optimized up to a 8×100 mm configuration for the growth of uniform 0.01–80-micron thick, specular, device-quality SiC epitaxial layers with low background doping concentrations of <1×10¹⁴ cm⁻³, and intentional p- and n-type doping from 1×10¹⁵ to >1×10¹⁹ cm⁻³. We address the observed degradation of the forward characteristics of bipolar SiC PiN diodes [H. Lendenmann, F. Dahlquist, J.P. Bergmann, H. Bleichner, C. Hallin, Mater. Sci. Forum 389–393 (2002) 1259], and discuss the underlying mechanism due to stacking fault formation in the epitaxial layers. A process for the growth of the epitaxial layers with a basal plane dislocation density <10 cm⁻² is demonstrated to eliminate the formation of these stacking faults during device operation [J.J. Sumakeris, M. Das, H.McD. Hobgood, S.G. Müller, M.J. Paisley, S. Ha, M. Skowronski, J.W. Palmour, C.H. Carter Jr., Mater. Sci. Forum 457–460 (2004) 1113].     

An optical method for measuring nanoparticle size

We describe a method for determining the size of nanoparticles and their optical constants that is based on analysis of the spectrum of extinction of light by these particles. We show that the results of our mathematical modeling agree well with the experimental data.     

An opto-electrical method for measuring the gap of LCD glass plates

We focus on the experimented system development for the measurement of the gap of LCD glass plates. The measurement system includes a laser light source, lens module, image capturing system and the algorithm for calculation of the position of light spots. We emphasize the structure of laser triangulation in an optical system. The software is focused on the algorithm for calculating the position of light point, including centroid calculation method (CCM) and Fourier phase shift (FPS).

Furthermore, to verify the feasibility of the algorithm, we use computer software to simulate experiments. We also discuss the contribution of the noise to the accuracy for the CCM and FPS. To complete the development of the opto-electrical measurement system and to verify the accuracy for the hardware architecture, we use a novel mechanism of multi-track and concentricity, laser light source, lens module, and image capturing system.     

外场多光轴平行性测试的光学系统设计

针对外场条件下因大气环境影响导致多光轴平行性误差的问题,设计了一种可见光、1.06μm激光及812μm的长波红外多光轴平行性测试的光学系统,系统采用卡塞格林系统为共光路并以可见光为基准光轴.卡塞格林系统的主次镜均采用双曲面校正球差及慧差,添加校正透镜减小了轴外像差.设计结果表明,该光学系统成像质量达到了衍射极限,在大气...     

New optical measuring system for solder joint inspection

Due to specularity and complex 3D geometry, the visual inspection of solder joints has been regarded as one of the most difficult tasks and thus has not guaranteed accurate inspection results. This paper deals with an optical sensing system designed to inspect solder joints automatically. Taking into account a specular characteristic, a new optical solder joint inspection system is proposed to obtain the external profile of solder joints accurately. A laser scanning unit scans the area of solder joint and observes the angle of the reflected beam. To realize this measuring principle, the system is so composed that a galvanometer steers the direction of laser beam to a point to be measured, a mirror unit (a parabolic and a conic mirror) gathers the specular components of the reflected beam toward its center and a beam-receiving unit positioned along the mirror unit's center line detects the reflected beam. To classify the defects of solder joint, a statistical pattern recognition method is utilized. To verify the validity of the developed system, a series of experiments was performed for SOPs and QFPs in insufficient, normal and excess soldering condition. Based upon observation of the experimental results, the proposed system is found to show good performance for inspection of solder joint defects.     

An integrated optical sensor for measuring glucose concentration

We used an optical sensor combined with a Mach-Zehnder interferometric waveguide and optical fibers to measure slight changes of aqueous sugar concentrations. The merits of this sensor are simplicity, reliability, high sensitivity and continuous monitoring. The technique is based on the fact that the refractive index of sugar solution changes with the concentration of sugar. In the experiment, one arm of the interferometer is clad with glue and is thus isolated from the sugar solution. The other one is exposed to the sugar solution. A single mode fiber is directly glued onto the interferometric waveguide, to guide the light into the interferometer. If the concentration of sugar covering the waveguide changes, the phase of propagating light in the exposed arm will be changed, while the phase in the other arm is fixed. Hence the output intensity from the interferometer is directly related to the concentration of the sugar solution. The result of this experiment yields the relation between the sugar concentration and output signal. From 0% to 1% concentration of sugar solution, there is only a 1.4×10^–3 refractive index difference. Two sets of experimental data have been obtained, showing a linear relation between the sugar concentration and the output signal from our sensor. This sensor could be used for continuous monitoring of blood sugar in the human body.     

An instrument for measuring low optical rotation angle

This paper develops a linear heterodyne interferometer based on phase-locked extraction for measuring low optical rotation angle. The validity of the proposed design is demonstrated by measuring a half-wave plate. The average relative error in the measured rotation angle of the half-wave plate is determined as just 0.74%. When applied to the measurement of glucose solutions with concentrations ranging from 0 to 1.2 g/dl, the average relative error in the measured rotation angle of glucose solutions is determined to be 1.46%. The correlation coefficient between the measured rotation angle and the glucose concentration is determined to be 0.999991, while the standard deviation is just 0.00051°. The current system is capable of measuring glucose concentration as low as 0.01 g/dl with an error of 6.67% in the rotation angle measurement. Overall, the experimental results demonstrate the ability of the proposed system to obtain highly accurate measurement of the optical rotation angle.     

用于测量流量和含沙量的超声波液位测定系统

本文介绍了实验室内用于测量流量和含沙量的超声波液位测定系统，此系统采用气介式方案，选用复合材料高频换能器作为超声波发射／接收器件，结构简单，静态测量时测量误差在１５０ｍｍ范围内不超过１ｍｍ，并可与微机进行远距离通讯。     

An optical lever for measuring very small rotational oscillations

The optical lever serves to measure small angular displacements. We use one here in conjunction with a twin photodiode and lock-in amplifier to measure the amplitude and phase of a rotational oscillation. This simple combination permits an extremely low noise level; in our experiment the noise level was 10^-13 rad, or .     

An acousto-optical deflection system for use with multi-laser arrays in optical memories

Proposals have been made to utilise arrays of GaAs lasers in optical computer memories. For fast, random access to data the use of acousto-optical deflectors seems feasible. The number of lasers for use with each deflector is normally severely limited, because of the bandwidth limitation which is inherent in acousto-optic devices. This note describes a technique whereby the bandwidth limitation can be largely overcome, so that light from many lasers can be deflected by a single deflector.     

Holographic optical elements — State-of-the-art review: Part I

A state-of-the-art review on holographic optical elements (HOE) is presented in two parts. In Part I a conceptual overview and an assessment of the current status on the design of HOE have been included. It is pointed out that HOE development based on the use of squeezed light, speckle, non-linear recording, comparative studies between optics and communication approaches, are some of the promising directions for future research in this vital area of photonics.     

真空光学系统窗玻璃的设计与分析

根据红外望远镜的工作状态,望远镜窗玻璃主要受到大气压力和重力的影响,由于要求得到高空间分辨率的太阳像,所以对窗玻璃的变形要求很高。用有限元法对处于工作状态下的窗玻璃进行计算,得到不同厚度和不同工作角度窗玻璃的变形数据,然后对变形数据进行比较分析。可看出对应于相同的口径,不同厚度的窗玻璃,在此工作状态下的变形有较大的不同,但在对于厚度不变而只改变观测角度即受力状态的情况下,重力对窗玻璃的影响相对是较小的,通过分析比较得到了比较适合此系统的窗玻璃的口径和厚度。     

The use of circular optical grating for measuring angular rotation of mirrors

This paper explores the feasible use of circular optical grating for measuring the rotation of mirrors that are commonly found in micro-systems. Both theoretical and experimental results show that distortion of the circular grating that is projected onto the mirror surface is a simple function of the angular rotation of the mirror. The circular grating may readily be generated using a standard Michelson interferometer or an LCD projector. Through manipulating the distance between the interferometer and the mirror surface, the diameter of the optical grating may be varied. Furthermore, the additional use of a converging lens enables a significant reduction in the size of the grating: with simple laboratory facility, small circular grating of about 400 μm is achieved for use on micro-systems. With the use of more sophisticated optical elements, the angular rotation of even smaller micro-mirrors may be measured.     

Light scattering properties of a rough-ended optical fibre — theoretical evaluation

Almost uniform wide-angle laser irradiation, for use in medical applications, is achieved by roughening chemically the output end of an optical fibre. The angular distribution of the scattered light is studied theoretically using perturbation theory. The theoretical results evaluated from a simple method of calculation are in sufficiently good agreement with experiment.