激光双谱线功率的不一致性与拍波干涉仪对准精度的关系

双谱线功率一致性是拍波干涉测长方案对激光光源提出的特殊要求。本文从拍波干涉仪对准方法的实际出发,在分析双谱线拍波干涉仪输出信号的基础上,研究了双谱线功率不一致与拍波干涉仪对准精度的关系,提出了基本对准盲区和盲区扩大量的新概念,建立了描述盲区扩大量与双谱线相对功率差之间关系的解析表达式。为设计拍波干涉仪的激光稳定环路和提高拍波干涉仪的对准精度提供了理论分析工具。     

Development in laser interferometry for position sensing

Interferometric developments which improve the performance of the laser interferometer as a position sensing device are described. The double pass attachment is an optical accessory which doubles the resolution of the Hewlett-Packard linear and plane mirror interferometers. Unlike previous attempts to extend resolution optically, this device does not fold just one of the two interfering beams and hence does not introduce error due to its own motion. Simple addition of a quarter wave plate to the attachment gives a differential version of the plane mirror interferometer. Various configurations of this differential interferometer, and their application to machine tools and to integrated circuit lithographic and inspection equipment, are discussed. A new ‘wavelength tracking’ device, based on differential interferometry, directly and precisely monitors changes in laser wavelength inside a highly stable mechanical cavity. Easily incorporated as an additional interferometer axis, the device improves compensation for changes in laser wavelength.     

波长移相干涉仪的算法研究

叙述了波长移相干涉仪的基本原理,分析了其特点,对传统硬件移相干涉仪和波长移相干涉仪进行了比较,指出了它们的优缺点和应用范围.以美国New Focus公司的可调谐半导体激光器为例,简述了实现波长调谐的硬件.文中将波长移相干涉仪算法分成三类:加权多步波长移相算法、基于傅里叶变换的波长移相算法和多波长算法,对这三类算法进行了较详细的叙述和分析,指出了各自的优缺点和应用范围.基于傅里叶变换的波长移相算法,提出了结合差分运算的适合于台阶测量的新算法,克服了已有算法中需要参考基准和参考面的缺点,提高了算法的实用性.     

激光干涉仪波长的自动实时补偿

介绍了激光干涉仪在现场测量中激光波长的补偿,通过分析激光干涉仪测量数据处理公式,提出了波长补偿值用终端修正的方式进行自动实时补偿的理论。     

Optoelectronic modulation of a laser interferometer in the infrared for accurate electron density variation measurements

An improved method for high-electron-density (10(17) cm(-3)) measurement in a shock-generated plasma is described. A laser interferometer operated at 3.39 mum is regularly modulated (1 MHz) by a LiNbO(3) electro-optical crystal. Thus electron-density variations of 8x10(15) cm(-3) mus(-1) and fluctuation of 8x10(14) cm(-3) can be simultaneously and accurately measured in a 4x4-cm conventional shock tube. Experimental results in reflected shock waves are presented.     

Changes of optical properties of retroreflector installed in LHD

This article describes changes of optical properties of retroreflectors installed on the inner wall of the vacuum vessel of the Large Helical Device. They were made of stainless steel and were used for a CO(2) laser polarimeter. The reflectivity for a CO(2) laser beam dropped up to 40% after the start of glow discharge cleanings and main plasma experiments. Then it decreased gradually. The reflectivity in a wavelength range shorter than 10 mum decreased significantly through one experimental campaign (about 4 months). On the other hand the reflectivity in a wavelength range longer than 50 mum was larger than 70%. Decrease in the reflectivity in the central region of mirrors was more significant (the reflectivity for visible beams became almost zero) than that in the edge. The distribution of the reflectivity along the radial direction is expected to be related to the shape of the retroreflector. The parallelism of the reflected beam to an incident one also deteriorated. The changes in the polarization angle and in the ellipticity of reflected light polarization were not observed from the visible to the far infrared range.     

利用Fizeau干涉仪测量激光波长

采用Fizeau干涉仪测量激光波长,测量的重复精度为5×10^-7.     

Linewidth reduction of a distributed-feedback diode laser using an all-fiber interferometer with short path imbalance

The linewidth of a distributed-feedback (DFB) diode laser at 1156 nm, of which free-running linewidth was 3 MHz, was reduced to 15 kHz using an all-fiber interferometer with 5-m-long path imbalance. Optical power loss and bandwidth limitation were negligible with this short optical fiber patch cord. This result was achieved without acoustic and vibration isolations, and the frequency lock could be maintained over weeks. In addition to its simplicity, compactness, robustness, and cost-effectiveness, this technique can be applied at any wavelength owing to the availability of DFB diode lasers and fiber-optic components.     

具有隔离器功能的激光干涉仪的研究

提出了一种具有隔离器功能的激光干涉仪.既可以进行干涉测量,又具有隔离器功能,可以防止反射光回到光源,使光源保持稳定,确保了测量精度.该干涉仪由常规干涉仪和双级隔离器的结构有机的结合起来,其中某些元件合二为一,使一个元件起到双重功能的作用,同时使干涉光路和隔离光路也相互重合起来.理论分析和实验研究表明:该方案是可行的.隔离度与双级隔离器的隔离度相同,达到了48dB.该装置的干涉测量精度与一般干涉仪一样取决于激光波长,但该装置结构紧凑,简化了测量系统,实际使用更为方便.     

An Astigmatic Wavelength Meter

An astigmatic scheme of a laser wavelength meter based on a single air-gap Fizeau interferometer is described. For a multimode laser, the accuracy in determining the center of gravity of a spectrum is within 1 GHz. Two complementary testing techniques are proposed for the instrument. By using them, it was shown for the first time that, for this type of meters, a systematic error arises and increases with a decrease in the radiation-spectrum width. The effect is periodic in the lasing frequency and results from a weak beam that is brought about by a reflection from the front surface of the interferometer. Moreover, in the previously designed optical schemes, this effect is so strong that unambiguous determination of the wavelength of a single-frequency radiation is impossible. The use of an astigmatic scheme helps additionally attenuate the influence of the third beam, thus eliminating the ambiguity in the results and reducing the absolute error to a value of ±1.5 GHz.     

雷尼绍与多普勒激光干涉仪测量方法比较

介绍了雷尼绍激光干涉仪和多普勒激光干涉仪的测量原理,并对这两种激光干涉仪的测量方法进行了比较。结果表明,当只需要测量机床的线性定位精度时,两者都比较适合。当需要测量机床的所有几何误差时,由于多普勒激光干涉仪采用了激光向量技术,测量周期大大缩短,测量效率较高。     

Improvement and validity of shock measurements using heterodyne laser interferometer

The improvement and validity of shock measurements using only the laser head (heterodyne laser interferometer) of a commercial laser Doppler vibrometer was investigated by comparing acceleration waveforms measured by a homodyne laser interferometer with those measured by a heterodyne laser interferometer. The acceleration waveforms were generated from the displacement waveforms obtained with a reference quadrature homodyne laser interferometer by applying a numeric differentiation process twice. The differences between the two acceleration waveforms were found to be small with the measurement uncertainty in case of high acceleration level. In a further investigation, the accuracy of the shock measurements taken by the homodyne and heterodyne laser interferometers were compared in computational simulation. The results indicated that the accuracy of the heterodyne laser interferometer was superior to that of the homodyne laser interferometer.     

Frequency selection of the radiation of a fiber laser with a reflection interferometer

This paper considers the results of using a two-mirror multiple-beam reflection interferometer (RI) which has a response function in reflection similar to the response function of a Fabry-Perot interferometer in transmission. The two-mirror cavity of the RI included two flat mirrors, one of which was highly reflective, and the other had an asymmetric coefficient of reflection from different sides. The light reflected from the RI was brought to an optical fiber through a collimator lens. The optical fiber, collimator, and RI constituted an integrated fiber RI, which was first used for continuous tuning of the wavelength of an erbium ring fiber laser with a continuous generation in the spectral range 1520–1566 nm.     

一种波长调制干涉仪光强实时反馈控制系统

提出了一种实时反馈控制系统,保证波长调制干涉仪的激光光强在波长调谐过程中的稳定性,以减小波长调制干涉仪因激光光强的波动产生的相位误差。该控制系统由光电探测器、数据采集卡、光电调幅器和控制软件等组成。实验结果表明,该系统的响应速度超过了干涉仪获取干涉图的速度,不仅能够稳定输出理想的光强值,而且还提高了干涉仪的测量精度。     

Instantaneous laser Doppler velocimeter using a fast wavelength tracking Michelson interferometer

A new species of laser Doppler velocimeter is presented based on wavelength detection with a two-beam interferometer. A finite optical path difference, Deltaphi, of the interferometer creates a sensitivity of the interference to wavelength changes. By means of a fast feedback system, the phase, Deltaphi/lambda is kept constant. Wavelength changes are immediately answered by changes of Deltaphi generated with a Pockels cell. The Pockels cell voltage represents a continuous signal proportional to the instantaneous velocity component of the scattering object. A time resolution of 1 micros or lower can be obtained. The field of applications includes velocity recordings in gas flows containing tracer particles as well as velocity recordings of moving surfaces. A number of experiments are described demonstrating the performance of the system.     

Application of blue laser direct-writing equipment for manufacturing of periodic and aperiodic nanostructure patterns

This study presents the novel development of low cost, highly efficient blue laser direct-writing equipment for using mask-less laser lithography to manufacture periodic and aperiodic nanostructure patterns. The system includes a long-stroke linear motor precision stage (X, Y), a piezoelectric nano-precision stage (Y, θz), a 3-DOF (degrees of freedom) laser interferometer measurement system, and a blue laser direct-writing optical system. The 3-DOF laser interferometer measurement system gives the control system feedback for displacement (X, Y, θz) of the equipment. The laser processing equipment consists of a blue laser direct-writing optical head, a field-programmable gate array (FPGA) alignment interface, and an optical head servo controller. The optical head operates at a wavelength of 405 nm. Processing the nanostructures on thermo-reaction inorganic resists with precise control of the laser intensity, taking advantage of the threshold effect to exceed the limitations of optical diffraction, and reduces the nanostructure hole size. The equipment can be used to fabricate various periodic nanostructure patterns, aperiodic nanostructure patterns, and two-dimensional patterns. The equipment positioning accuracy is within 50 nm at a speed of 50 mm/s, and the minimum critical dimension can be achieved about 100 nm or so.     

激光干涉仪测量失真正弦波形位移误差估计式

本文在分析介绍了激光干涉仪测量位移原理的基础上,指出了标准振动台稳态正弦绝对校准法中,激光干涉仪测量的只是工作台面运动的路程而非矢量位移,因此对于测量含有谐波失真的正弦波形将引入测量原理性误差。文中利用波形加速度失真度系数详细推导并给出了谐波失真所引入的测量误差的估计式,对准确评价传感器校准精度具有重要意义,同样也有助于我们对激光干涉仪测量精度的认识。     

‘Open-loop’ tracking interferometer for machine tool volumetric error measurement—Two-dimensional case

The tracking interferometer, or the laser tracker, is a laser interferometer with a steering mechanism to regulate the laser beam direction to follow a retroreflector (“target”). Applying the multilateration principle, it measures the target's three-dimensional position at an arbitrary location in the workspace. Its application to the volumetric accuracy measurement for coordinate measurement machines or machine tools has been long studied. In this paper, we propose the ‘open-loop’ tracking interferometer, where the laser beam is regulated toward the command target position. This eliminates the automated tracking mechanism and thus may significantly reduce the manufacturing cost of conventional tracking interferometers. The objective of this paper is to validate this ‘open-loop’ tracking interferometer concept by investigating its measurement uncertainty both experimentally and analytically. To simplify the problem, this paper focuses on the measurement of the target's two-dimensional position by using a single-axis ‘open-loop’ tracking interferometer prototype.     

单片机控制的Fizeau激光数字波长计

详细介绍了采用8098单片机控制Fizeau干涉仪测量激光波长的实现方法,包括系统的硬件和软件设计,文章最后给出了系统的测量指标,其测量范围400-1100nm,测量精度<0.001nm.