Rotationally Tunable Two-Beam Interferometer with a Fixed Photosensitive Element. Part II. Interferometer Based on a Beam-Splitter Unit

A tunable (in terms of the angle of convergence of intersecting light beams) two-beam interferometer with fixed mirrors and a fixed photosensitive element is considered. The photosensitive element is based on a symmetric beam-splitter unit where tuning of the interference pattern period is ensured by only one type of motion: interferometer rotation with respect to the motionless source of the collimated light beam. It is demonstrated that the period can be controlled in this way for convergence angles from 30 to 180° for beams with diameters of 10% or more of the beam-splitter unit length. In this region, the greatest width of the range of convergence angle tuning can exceed 40°, and the admissible beam diameter approaches 40% of the beam-splitter unit length. Comparisons with a similar interferometer based on a beam-splitter cube are performed, and possible areas of application of the considered interferometer are determined.     

Limiting characteristics of a rotationally tunable two-beam interferometer with a fixed photosensitive element

Results of calculations of the limiting characteristics of a rotationally tunable two-beam interferometer on the basis of a beam-splitter cube with fixed mirrors and a fixed photosensitive element are presented. The convergence angle is changed solely by rotating the beam source with respect to the interferometer. It is shown that the convergence angle can be varied in the interval from 46 to 166° with sufficiently wide light beams.     

Tunable holographic interferometer with a beam-splitting unit and fixed mirrors

This paper presents a holographic interferometer configuration with inclined fixed mirrors based on a beam-splitting unit in which the convergence angle of the partial beams is tuned only by rotating the interferometer relative to the radiation source. The continuous range of tuning is close to the maximum possible (0–180°). The path lengths of the interfering beams are automatically aligned due to the mirror symmetry of the system. The position of the axis of rotation providing minimal aperture limitations in almost the entire range of tuning is determined. A comparison is made with an alternative configuration based on a beam-splitter cube.     

Reconfigurable holographic interferometer with fixed mirrors

The configuration of a two-beam interferometer with fixed inclined mirrors for recording holographic gratings is described. The convergence angle of the partial beams is adjusted in the range from 0 to 180° by changing the angle of incidence of the primary beam on the entry edge of the beam-splitting cube without additional adjustment of the mirrors. The path lengths of the interfering beams are automatically aligned by the mirror symmetry of the system. The optimal kinematics of adjusting the convergence angle is found that allows working with beams of sufficiently large diameter in the whole range of adjustment. The interferometer is highly resistive to vibration due to lack of adjustment devices.     

High sensitivity all-fiber Sagnac interferometer temperature sensor using a selective ethanol-filled photonic crystal fiber

An all-fiber Sagnac temperature sensor based on 3?dB tapered coupling and ethanol selective-filled photonic crystal fiber was demonstrated theoretically and experimentally. The ethanol selectivity-filled photonic crystal fiber has noncircular symmetry and thus exhibits birefringence. The ethanol selective-filled photonic crystal fiber, acting as the sensing element, was inserted in a Sagnac loop interferometer to measure temperature. The output spectra of Sagnac interferometer applied different temperatures were measured and analyzed. Experimental results have shown the temperature sensitivity of the Sagnac interferometer is 1.65?nm/°C in the range of 25–33°C.     

Investigation of Inherent Gas-Bearing-Torques Acting on a Spinning Sphere Gyro

During testing of a “spinning sphere airborn in a rotating housing” torques were observed, which are inherent in the system. The components of these torques about the spin axis caused a speed difference between sphere and housing, the components 90° to the spin axis caused a gyroscopic precession of the sphere. Both effects were measured and plotted as function of the tilt angle between the spin axis and the vertical direction. Curves of similar shapes were obtained by calculating the speed of the sphere with respect to the stationary gaspocket, established by the eccentricity and the attitude angle. The Precession-torques show a maximum value at an approximate 45° till angle, the speed difference shows it at 90° A vertical spin axis proved to be the only torque-free position.     

光栅复制拼接光路中入射光角度对拼接误差的影响

设计了一种基于干涉检验法的复制拼接光栅测量光路。针对光栅复制拼接光路中入射光角度难以精确测量的问题,分析了光栅拼接实验中入射光角度对光栅拼接的影响。建立了光栅拼接误差模型,分析了五维拼接误差的容限要求。按照光栅复制拼接光路的要求,设计了一种干涉仪角度调节装置。根据误差模型和拼接光路分析了500mm×500mm大尺寸中阶梯光栅复制拼接光路中入射光角度误差与拼接误差的关系。结果显示:入射光角度误差为1°,拼接光路中绕x轴,y轴的转动误差Δθx,Δθy和沿z轴的位移误差Δz的计算值与实际值之间分别相差0.002 1μrad,0.003 3μrad和0.348 2nm时,引起波前差为2.590 1nm。根据这一计算结果,给出了干涉仪角度调节装置的设计指标,即设置角度调节分度为0.1°时,可满足大尺寸光栅复制拼接要求。     

An attitude sensing device

A device for sensing the attitude of an arbitrarily located object has been developed by the Polar Geophysical Institute, Kola Research Center, Russian Academy of Sciences, for carrying out geophysical research. The device is capable of determining three angular coordinates of an object: the angles of roll and pitch with respect to the Earth’s horizontal plane and the azimuth angle with respect to the direction toward the magnetic north. The measurement range of the azimuth is from −180° to 180° with an error of ≤1°. The angles of roll and pitch can be measured in the range from −60° to 60° with an error of ≤0.5°. The device is reliable and easy to operate.     

Four-point bisensitivity velocity interferometer with a multireflection etalon

A four-point bisensitivity velocity interferometer system for any reflector (VISAR) with a renovative delay etalon is proposed and demonstrated. In this interferometer, we introduce a new film-coating strategy to accurately measure small velocity with relatively short and cheap etalon. Laser pointing to the etalon is split into two beams with different incident angles with each beam going through the etalon in different path. The beam with the smaller incident angle is reflected three times before it leaves the etalon, while the other beam with larger incident angle goes through the etalon to and forth only once. The delay time of the laser beam with smaller incident angle is almost three times longer than that of the beam with larger incident angle. In the example of the laser with a smaller incident angle, the velocity per fringe of this interferometer can be reduced by approximately three times. The etalon is optimized so that four laser beams can be penetrated in the vertical direction at the meantime. With an etalon of 200 mm in diameter and 150 mm in length, a four-point bisensitivity velocity interferometer can achieve the velocity per fringe of 100 and 350 m/s fringe. A measurement has been successfully undertaken for the steel flyer driven by the explosive where the developed interferometer applies.     

条纹周期动态可调的通用型干涉仪

提出一种新型结构的通用型干涉仪,用于实现不同结构、不同形状的光学透镜、光学晶体等元件的快速目视观察与精确测量。该干涉仪利用可相对旋转的双光楔对条纹周期进行动态调制完成实时检测。以两块雅敏干涉平板为主体结构,在双光路中各自放入一对楔角完全相同的光楔对,建立条纹周期和条纹倾斜方向与光楔对相对旋转角度之间的关系,并采用光学晶体畴反转实时检测验证干涉仪的测量性能。试验结果表明,干涉仪的相位检测精度约为0.2 rad(λ/30),条纹周期(一对黑白条纹)为0.105~5.993 mm/pair,光路中光楔对的相对转角可在0~179°调节。干涉仪具有完全对称的光路结构,由于较高的稳定性和抗干扰能力,可针对不同类型光学元件的结构特点进行条纹周期的实时调制,并可达到较高的检测精度。     

Evaluation of carbide grades and a new cutting geometry for machining titanium alloys

A new cutting geometry consisting of a high clearance angle (from 10° to 15°) together with a high negative rake angle (from ?10° to ?15°) is proposed for increasing cemented tungsten carbide tool life during the machining of titanium alloys. This geometry would allow the use of a conventional insert (with an included angle of 90°) of any suitable shape (e.g. round, square or triangular) on a modified tool holder. The new geometry is found to yield longer tool life than does a high clearance angle (+15°) alone or a conventional tool with a low negative rake angle (?5°) and a low clearance angle (+5°). Further, the lower cobalt grade (Carboloy grade 999) and finer carbide grain size tools (Carboloy grade 895) are found to yield longer tool life than the higher cobalt grade medium carbide grain size tools (Carboloy grade 883), which are currently the most commonly used grade. A new ceramic tool material, an Si-Al-O-N compound, is found not to be suitable for machining titanium alloys because of rapid wear.     

Absolute angle measurement using a phase-encoded binary graduated disk

A new absolute angle measurement method using a phase-encoded binary graduated disk (PE-BGD) is presented. An absolute position binary code (APBC) is encoded by shifting the positions of binary patterns, and can be sub-divided by detecting their positions with sub-pixel resolution of a multi-element detector. Using an n-bit linear shift feedback register, we expressed a recursive APBC dividing the full circle by 2ⁿ − 1 angular positions. An experimental setup was constructed with a microscopic imaging system, a rotation stage having a precision angle encoder, and two kinds of PE-BGDs which employed 10-bit and 13-bit APBC. The resolution of the APBC, which equals to signal period of the PE-BGD, used in each disk is 0.352° and 0.044°, respectively. We evaluated its performance by comparing the readouts of the proposed system and the angle encoder, throughout the full circle range and for one signal period. In the full circle range, the differences between two measurement systems were less than 1/50 of the resolution of the APBC. We also proved that the absolute angle could be measured with small nonlinearity error, which was less than 1/600 of the signal period.     

Polarized light microscopy of weakly birefringent biological specimens

A simple, but little known technique for producing marked colour contrast in images of weakly birefringent biological samples obtained with a polarized light microscope is investigated. The technique involves inserting a full wave plate at a small angle of horizontal rotation with respect to the analyser or polarizer, rather than at the conventional angle of 45° commonly employed in the field of mineralogy for examining strongly birefringent specimens. Inserting the full wave plate at a small angle (typically less than 10°) enhances the contrast between regions of tissue having different optical path differences and, in particular, different orientations of optic axes; improving the detection of structures of interest with the polarized light microscope.     

A microwave two-wave interferometer for plasma diagnostics

The scheme and the main elements of an interferometer simultaneously operating at frequencies of the 8-and 4-mm ranges are presented. To combin e two radiations in a common waveguide section and separate them by sending to the corresponding receivers, a special separation filter has been developed. A homo-dyne technique for transferring phase measurements to an intermediate frequency is employed in the interferometer. The range of unambiguously measured phase shifts is 1.5°—360°, and the phase-shift measurement error is within 5%.     

硅微光机械加速度地震检波器中M-Z光波导干涉仪结构设计

提出了一种新型的硅基M-Z干涉型光电集成加速度地震检波器。对硅基微光电机械加速度地震检波器的M-Z光波导干涉仪系统进行了系统研究和优化设计,采用K9玻璃作为基底层和包层材料,Bak7玻璃作为波导层材料,波导的宽度为4 μm,厚度为0.4 μm。M-Z光波导干涉仪的Y分支设计中采用上升反正弦S型弯曲,为适用于该干涉仪的信号臂和参考臂大跨距的特殊结构,应用波导转向镜实现了大角度光路转折,反射转向镜的内介质采用镀制金属铝膜得以实现,并利用BPM进行了仿真。为了防止TE模偏振光的偏振态经铝膜全反射后发生变化,加了4个长度为1 mm的TE模偏振器以保持其偏振态。实验结果与理论相符。     

工作波长为13.9nm的Laminar分合束光栅研制

目的：基于衍射光栅分合束元件的软X射线Mach－Zehnder干涉系统在惯性约束聚变,X射线激光等领域都有重要的应用前景。针对该干涉系统的特点设计、制作了工作波长为13.9nm的矩形分合束光栅。方法：利用全息曝光－离子束刻蚀工艺制作了特定参数的矩形光栅,利用长行程面型仪（LTP）对其线密度进行了测量,利用原子力显微镜测量其槽深与占宽比,利用国家同步辐射实验室（NSRL）U27实验站测量其衍射效率。结果：该矩形光栅的参数为线密度1000l/mm,槽深13±0.2nm,占宽比0.4±10%,Au膜厚度为40±0.5nm;在工作波长为13.9nm,81.2°入射时,其0级与-1级衍射光衍射效率乘积的最大值为8.6％,同时0级与-1级衍射效率亦接近,约为27％和30％。结论：测量结果充分证明矩形光栅作为13.9nm激光的分合束元件是能够获得高分合束效率(>7%),且矩形分合束元件易于制作。     

Low‐temperature‐SEM study of dihedral angles in the ice‐I/sulfuric acid partially molten system

The transport and mechanical properties of partially molten materials are influenced by the wetting behaviour of the melt with respect to the crystalline solid. The equilibrium microstructure of an ice + melt system was examined using low‐temperature scanning electron microscopy. The samples were prepared by spraying a liquid solution of H₂O‐H₂SO₄ into liquid nitrogen and packing the frozen particulates into aluminium capsules. Samples were then sintered at –35 °C or –55 °C (above the eutectic temperature, T_E=–62 °C) for various durations and were quenched in liquid nitrogen to capture the equilibrium microstructure. This paper reports the first quantitative measurements of dihedral angle in this system. The measured median dihedral angle between the solid and vitrified melt is approximately 26 ± 2° at –35 °C and increases slightly as temperature decreases and approaches the solidus (32 ± 3° at –55 °C).     

Thermal characteristics of louvered fins with a low-reynolds number flow

A heat recovery system is crucial for the effective use of energy where heat rejection from production processes is unavoidable and must be reused. The response of the louvered fins to the low-Reynolds number hot gas is yet to be reported in the literature for the application of a heat exchanger on low-speed hot plume arising from heat sources in production processes. This study focuses on the effects of the louvered fin heat exchanger’s design parameters, which include the louver pitch and louver angle, on the convective heat transfer, which defines the thermal interaction between the hot, buoyant, naturally-induced air and the louvered fins. The resulting Colburn factors (j) are compared with those derived under forced convection with a similar range of low Reynolds number (233 to 1024). All experiments are done on a 15:1 scaled-up model. The fin aspect ratios between the fin spacing and louver pitch are set at 0.75, 1, and 1.5, while the louver angles are set at 18°, 23°, 30°, 35°, and 40°. The Colburn factor strongly depends on the louver angle, especially at the lower range of the Reynolds number. The decreasing aspect ratio induces more hot buoyant air into the louver-formed channels, increasing the heat transfer rate. When the fin angle increases towards 30°, a larger Colburn factor is produced. However, the heat transfer characteristic drops as the angle goes beyond 30°. The highest j for the low speed flow is attained when the louver angle is 30° and the fin aspect ratio is 1.     

基于数字光处理技术的小型星模拟器设计

提出了基于数字光处理(DLP)技术的星模拟器系统的技术方案。根据星模拟器技术指标,确定了总体光学结构;在确定数字微镜元件(DMD)芯片规格的基础上,计算出星模拟器光学系统的焦距、单星张角、相对孔径等光学系统参数;最后,介绍了星图模拟软件的设计方法。计算及模拟结果表明,设计的小型星模拟器实现了星图视场为10.5°×7.5°,模拟星等为2.0~8.0等星,单星张角优于40″;将采样周期控制在毫秒量级,能为星敏感器提供任一时刻、任一惯性坐标系下指向的模拟星图,可满足航天工程中对小型星模拟器的动态性、大视场、宽星等范围、短采样周期等需求。     

基于保偏镜组的外差干涉测量几何误差分析

角锥棱镜由于本身缺陷会导致失偏效应。在平面镜外差干涉仪中,使用一种保偏反射镜组替代角锥棱镜,以减小外差干涉仪的非线性误差。根据这个平面镜外差干涉仪的基本光路图,基于偏振分光棱镜和角锥棱镜的基本光学特性,分析了平面镜外差干涉仪中3个偏振分光棱镜偏摆角、仰俯角和滚动角,保偏反射镜组中2个偏振分光棱镜之间的间距和角度,以及角锥棱镜的偏摆角和仰俯角等误差对干涉仪的影响。推导出外差干涉仪中各个光学元件的最大安装误差,并规定好其加工精度,确保外差干涉仪性能。