Optical method of measuring angular displacement using four photodiode arrays

A method of measuring angular displacement is investigated that uses two pairs of photodiode arrays arranged in a square and crossed linear images produced with two cylindrical mirrors. According to this method the measurement error can be greatly reduced even when inclination of the rotation axis exists.     

角位移Fabry-Perot干涉测量

提出了一种基于Fabry-Perot板干涉的角位移测量新方法。此方法采用函数近似,只需将初始入射角确定在40°到50°之间,即可由角位移与干涉信号条纹数变化间的函数关系,高精度测量角位移。解决了采用F-P板干涉法测量角位移需精确确定入射光初始角的问题。使用计算机处理采集的干涉信号,对干涉条纹进行细分,实现干涉信号相位测量的高分辨力。理论模拟和实验结果得出本方法可以实现精度为10-5rad数量级的角位移测量。该方法的测量装置采用带尾纤的半导体激光作为光源,由自聚焦透镜准直,出射光束直径为0.5mm,使探测头为小光斑。该装置结构简单,能实现小型化。     

Optical method for measuring optical rotation angle and refractive index of chiral solution

Based on the phenomena of Brewster's angle and the principles of common-path heterodyne interferometry, we present an optical method for measuring the optical rotation angle and the refractive index of a chiral solution simultaneously in one optical configuration. A heterodyne light beam and a circularly polarized heterodyne light beam are separately guided to project onto the interface of a semicircle glass and a chiral solution. One of the beams is transmitted through the solution, and the other is reflected near Brewster's angle at the interface. Then the two beams pass through polarization components respectively for interference. The phase differences of the two interference signals used to determine the rotation angle and the refractive index become very high with the proper azimuth angles of some polarization components, hence achieving an accurate rotational angle and a refractive index. The feasibility of the measuring method was demonstrated by our experimental results. This method should bear the merits of high accuracy, short sample medium length, and simpler operational endeavor.     

Optical approach to angular displacement measurement based on attenuated total reflection

An optical approach for angular displacement measurement (ADM) based on the attenuated total reflection technique is presented. As a laser beam is incident upon a planar optical waveguide, an m line is obtained by scanning the incident angle. Theoretical analysis shows that the m line sharply shifts with a tiny variation of the thickness of the waveguided layer. And the specific schemes for ADM, which are based on the angular interrogation and the intensity measurement, are analyzed. The calculated result of sensitivity demonstrates that the intensity measurement is more efficient than the angular interrogation. Furthermore, small incident angles indicate higher sensitivity to the angular displacement than relatively large incident angles for the intensity measurement.     

Optical method of determining the components of the relative displacement vector

The theory of a laser interference method of determining in real time the relative displacement of two scattering objects in space is put forward and an experimental verification is described. Pis’ma Zh. Tekh. Fiz. 25, 88–94 (December 26, 1999)     

Photoelectric method of measuring the rotation period of a turbine drive shaft

The rotation period has been measured for a turbine shaft in a thermal power station by an optoelectronic method. The electronic unit is screened from electromagnetic interference at line frequency, and the fiber-optic lines provide a measurement error of 5·10⁻⁴%. Translated from Izmeritel'naya Tekhnika, No. 12, pp. 28–29, December, 1996.     

激光瞄准大轴半径测量方法的研究与应用

提高大型轴类工件轴径在线测量精度，其主要困难在于用非接触法时如何精确地确定测量点的位置。采用特殊的机械装置，使激光光斑落在被测工件表面上，通过CCD摄像及图像分析，可获得优于0．01mm的定位瞄准精度。实验表明，对于300mm以下的轴径，这种方法的测量误差不超过0．015mm。     

Optical method for measuring slow crack growth in cementitious materials

The double-torsion (DT) test is commonly used to calculate slow or subcritical crack velocities in (quasi-)brittle engineering materials directly from the measured load relaxation of notched DT-specimens. In cementitious materials a significant part of the recorded load relaxation in the DT-test may be due to specimen creep deformation, and this would then lead to overestimated crack velocities. In this paper we describe a method to optically measure slow crack growth in cementitious materials by carrying out DT-tests under the optical microscope or inside the environmental SEM. Crack tip detection is facilitated by digital image correlation of the time-lapse microscope recordings. DT-tests at 10?% relative humidity in hardened cement paste (with w/c-ratio of 0.4, 0.5 and 0.6) showed that optically measured crack velocities were significantly lower than those calculated from the DT-specimen relaxation. In many experiments the subcritical crack growth rapidly stopped, while an ongoing specimen load relaxation was recorded. At 90?% relative humidity, load-relaxation in the DT-test was much stronger than at 10?% relative humidity, because subcritical cracking and creep-induced relaxation both increase with moisture content.