Key Engineering Materials Vols. 295-296

Abstract: A two-color heterodyne interferometer based on the movement of the optical diffraction grating is proposed. The method allows us to measure the phase of synthetic wavelength f s directly and with high accuracy to extend the range of unambiguity for interferometric measurements by using two close wavelengths. Our experiment results show that the uncertainty in displacement measurement caused by the uncertainty in f s is 0.20 µm, smaller than the half of a single wavelength we used. The fringe order of a single wavelength can be determined without ambiguity. The uncertainty in displacement measurement can be improved further by using a single wavelength.

Abstract: A new method and devices for cooling of atomic hydrogen up to the values less than 100 µK aimed for the development of the optical frequency standard with significantly improved parameters (Δν/ν£1 x 10-16) is discussed. The method exploits the unique properties of atomic hydrogen such as atomic hydrogen does not condense at temperatures as low as 20µK and can not be heated by IR radiation in the absence of atom-wall collisions. Therefore, the most efficient and well-known gas cooling technique can be employed, namely, the adiabatic expansion of the volume occupied by the gas. This approach is used in a cryogenic gas expansion machine. It is suggested to use the adiabatic expansion of the volume of the magnetic atomic trap containing atomic gaseous hydrogen for embodiment of this idea.

Abstract: Ensuring the safety of nuclear reactors and their high exploitation reliability requires a 100 % noncontact precise inspection of geometrical parameters of their fuel elements, grid spacers and quality of fuel element surface. For the solution of these 3D inspection tasks we have developed and produced a laser measuring machine (LMM) using multipoint structured illumination, optoelectronic shadow systems as Control and optical low-coherent profilometer as Radar. The results of their industrial testing are presented and discussed.

Abstract: In laser measuring scanners, in addition to the ideal output signal, interfering signals occur. They are due to superimposition of diffracted, reflected, scattered, incident, transmitted and interfering light. The proportions between the mentioned components vary in time and also the total intensity distribution changes. Having the above in view, a close analysis of detector signal was carried out. It was proved that for certain beam parameters the intensity distribution pattern depends on the geometry of object and the real dimension of an object can be calculated by introduction of the size dependent correction.

Abstract: An instrumental method for measuring the properties of liquids has been developed. The instrument, called the fiber-capacitive drop analyzer (FCDA), is based on a specially designed drop sensor by means of the fiber drop analyzing technology and the capacitive drop analyzing technology, and produces a volume-based fiber drop trace (VFDT), which shows the relation between the light intensity passing through the liquid drop and the instant drop volume. Preliminary experiments have been carried out and these prove that VFDT externalizes the overall properties of tested liquids and is suitable for fine discrimination among different kinds of liquids. In this paper, a multi-wavelength drop analysis (MWDA) method is described. In this case, the light source of the FCDA is developed from a single wavelength to a multi-wavelength. A special filter is employed to sort out the signals from the mixed multi-wavelength signals and it becomes possible to get two or three VFDT with different light wavelength at the same time. As one knows, a material will absorb the light on certain wavelengths. It means that, for a mixed liquid, one can get different VFDTs by MWDA at the same time. By this way, the resolution capability of a FCDA is enhanced very much due to more information including in those VFDTs. A special signal process circuit, the key technology of the MWDA, is described in this paper. The test results show that the new circuit had satisfied the MWDA method well and will be very useful to an instrument of the FCDA with MWDA.

Abstract: A binary second order rational polynomial is adopted to simulate and extend the phase distribution on reference plane. In order to get the coefficients of the polynomial accurately, iterative least-square method based on the first order Taylor series expansion is used. The effect of the real reference plane profile error on measuring result is reduced by using extended unwrapped phase to substitute the original unwrapped phase. The effects of the random phase error and the system geometrical parameter error are decreased. The measuring accuracy of the system is improved. The principle of the 3D profile measuring system based on grating projection, the theoretic analysis for accurate estimate of phase distribution on reference plane, and the experimental results are presented.

Abstract: A method for obtaining the core positions of fiber array is described. The technique is based on the use of calibrated mask. Because the mask and the fiber array are simultaneously moved and imaged, the measuring system is relatively simple in image processing, location, and vibration isolation. A prototype system with common components has been built for testing a number of commercial fiber arrays.

Abstract: This paper describes a system that detects and categorizes workpieces with random defects on electrodeposits glossy metal surface. The system is developed on the basis of combination CCD photoelectricity inspection technology, image processing and automatic control technology. In the system, a special illumination apparatus with a light source of diffused light is designed. Workpieces with defects are automatically selected through measurement with image enhancement retreatment, gray scale analysis, image binaryzation, feature extraction and image recognition. Hardware comprises sections of optics, image collection, and control circuits. Software is programmed in Visual C++ and assembly language. The system can resolve the difficulty of detecting random defects on surface under the conditions of high reflection and complex surfaces.

Abstract: Many monitoring methods for dam safety have been proposed in recent years but it is difficult to monitor the arch dam automatically. A novel inspecting method for arch dam safety monitoring is described in this paper. This measurement system is based on the principle of transmitting the comparative displacement one by one. The error and accuracy of the system is analyzed. By this method, a large arch dam can be measured automatically. Long distance data transmission system using CAN bus and Internet is established. It is convenient to monitor the safety of dams from long distances.

Abstract: Flexible coordinate measuring system based on laser tracking measurement system (LTS) is an effective method to detect 3D coordinates of moving target. However, the system suffers from various interferences resulting in low accuracy. This paper extends the application of a Kalman filtering algorithm in LTS to solve the problem. The laser tracking system is introduced. The state model of the laser tracking measurement system is developed and the linearization method of the model is analyzed. A Kalman filtering algorithm is used for the system. The result of the simulation shows that the proposed Kalman filter method works well for the improvement of accuracy of LTS.