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Lin Xue, Hiromasa Suzuki, Yutaka Ohtake, Hiroyuki Fujimoto, Makoto Abe, Osamu Sato, Toshiuuki Takatsuji
ANALYSIS OF GEOMETRIC DEVIATION FEATURE INDUCED BY THE FDK FOR COMPUTED TOMOGRAPHY MEASUREMENTS

Recently, due to the ability to precisely measure inner and outer structure of a specimen in one single scan, X-ray computed tomography (CT) has entered the field of dimensional metrology in industry. Unfortunately, it is very difficult to realize industrial-level accuracy with CT for various factors. In this paper we analyze one of the most serious effects, the FDK (Feldkamp–Davis–Kress) effect, which can be observed in most of the common X-ray CT scanners with a cone beam. The FDK is the well-know reconstruction algorithm widely accepted as a standard reconstruction method for cone beam type of CT. However, this algorithm merely provides an approximate result, for the large dimension specimen, the FDK effect on measurement result is severe. Therefore, we aim at improving measurement accuracy by analyzing the geometric deviation induced by the single FDK effect. We conducted quantitative analysis on the FDK effect using numerical phantoms of the sphere and hole plate that are standard specimen for dimensional CT measurements. After discussing the cause of the FDK effect and the deviation distribution feature on different spatial positions for the chosen numerical phantoms, an improvement strategy of measurement accuracy is proposed.

Osamu Sato, Hiroyuki Fujimoto, Sonko Osawa, Makoto Abe, Toshiyuki Takatsuji
BRIEF MACHINE CHECKING FOR COORDINATE MEASURING SYSTEM USING X-RAY COMPUTED TOMOGRAPHY

Form and dimensional measurements using X-ray Com- puted Tomography (X-ray CT) are useful on product development, reverse engineering, production control and quality certification because X-ray CT system can get three dimensional volumetric data of the full body of the target object at one time. Generally, three dimensional coordinate measuring systems (CMSs), in which X-ray CTs are also included, have measurement space distorted by the kinematic and other factors. Therefore, the deformation of the measurement space should be compensated for precise dimensional measurement. Moreover, the compensation function should be checked occasionally. In case of a widely-used coordinate measuring machine (CMM), the mobile frame of the machine is stable over a long period. Therefore, it is not necessary to check whether the compensation function on the CMM works well or not so frequently. In comparison with a CMM, the mobile frame of an X-ray CT is less stable. Thus, the space deformation compensation function on X-ray CTs should be checked at shorter interval than that on CMMs in order to perform precise dimensional measurement using X-ray CTs. In this research, a brief machine checking method for an X-ray CT is proposed. Through the repeating checking, the assessment of the long-term stability of the mobile frame of an X-ray CT is demonstrated.

Meiyun Chen, Soichiro Ueda, Satoru Takahashi, Kiyoshi Takamasu
MEASUREMENT OF SURFACE ROUNDNESS USING A MULTI-BEAM ANGLE SENSOR

This paper analyses existing techniques and proposes a newly technology named Multi-Beam Angle Sensor (MBAS) for measuring the roundness errors. Comparing with other methods, MBAS has just used one sensor and independence on the rotary stage, and can be used as a simple and convenient one in factory-level. Stability can also be improved by using the MBAS. In this paper, the optical probe is based on the principle of autocollimator and has a stability of 0.3 arcsec. Unlike multi- probe methods, the MBAS is constructed to realize the roundness measurement by using only one probe, which is less susceptible to instrumental errors. The experimental results confirming the feasibility of the MBAS for roundness measurement are also presented.

Adam Wo?niak, Grzegorz Krajewski
CMM DYNAMIC PROPERTIES OF THE SCANNING MEASUREMENT OF A 2D PROFILE

Scanning probes CMM became currently treated as a standard in coordinate metrology. Not only because of high quantity of data gathering in short time of probing but also scanning technology significantly decrease the inspection time. Modern manufacturing, especially in highly competitive economy, required more efficient measuring machine and processes, because inspection machine quite often become the bottle neck in whole manufacturing process. More efficient in coordinate metrology means faster cycles of measurement with acceptable accuracy. But in fact, scanning speed significantly influenced error budget.
This article proposes a new method of investigating and identifying principal components of CMM dynamic errors. The principle of the method will be presented and the validity of the method will be experimentally confirmed on a bridge Zeiss ACCURA coordinate measuring machine.

Hengyan Zhou, Lijiang Zeng
FABRICATION OF OPTICAL MOSAIC TWO-DIMENSIONAL GRATINGS WITH A DUAL LLOYD'S MIRROR INTERFEROMETER

Planar encoders can be used to measure two-dimensional (2D) displacements. In order to achieve large measuring ranges, planar encoders require large-size 2D gratings, which can be made by optical mosaic technique. We set up a dual Lloyd’s mirror interferometer to make optical mosaic 2D gratings. The key point to obtain good mosaic gratings is to fine tune the attitude and position of the substrate relative to the exposure beams during consecutive exposures, which can be realized by utilizing the interference fringes formed by the diffraction of the exposure beams from the latent gratings (exposed but undeveloped gratings). As the diffraction efficiency of the latent gratings is extremely low (~ 10-5), we use a high-sensitivity CCD to monitor the interference fringes. The attitude error of the substrate needs to be adjusted only once in order to ensure the groove direction’s parallelism for both dimensions of the grating. Experimentally we made 1 × 2 2D mosaics of 34 × (30+30) mm² area. A Fizeau interferometer is used to measure the mosaics. The Fizeau interferograms are well connected at the joint areas, demonstrating a good mosaic quality.

David I. Serrano-Garcia, Yukitoshi Otani
3-D SURFACE PROFILOMETRY EMPLOYING THE POLARIZATION PHASE SHIFTING TECHNIQUE

Optical measurement techniques have become indispensable tools in many areas of science and engineering. The whole-field, non-contact and highly accurate measurement are among the principal features of these techniques. The purpose of this research is to analyze the case when the sample under study presents polarization properties, as retardance or diattenuation. The use of phase shifting modulated by polarization has the advantage of not requiring mechanical components, such as a piezoelectric transducer (PZT), to obtain the phase shifts. The main purpose of introducing polarization phase shifting techniques, added with replication systems, is to collect all the phase-shifted data in a single exposure in order to minimize time-varying environmental effects. When the sample under study changes the polarization properties of the object-beam, errors associated at the contrast and phase shift values on the final interferogram are obtained. The main purpose of this work is to find a suitable model in charge to modelate when the sample presents polarization properties as retardance or diattenuation. A model based in find a Mueller matrix of the polarization phase shifting interferometer is introduced in order to settle the basis for a non-ideal model.

Takashi Nishikawa
SUPER HIGH VERTICAL RESOLUTION NON-CONTACT 3D SURFACE PROFILER BY FOCUS VARIATION WITH WHITE LIGHT INTERFEROMETRY

This system is developed as a focus variation microscopic system with great versatility and high vertical resolution. Conventional focus variation microscopic systems cannot measure surface topography of smooth surfaces such as a glass surface because the surface has no texture to get effective point focus sharpness. This system can obtain very high point focus sharpness by operating a 3x3x3 voxel operator, we call ‘the Digital Stylus’, to fringe images which are generated by the two beam interferometric objective lens. Furthermore a new algorithm to decide the position of focal point, we call ‘the APF: Approaching Function’ method, is introduced. The decision of the focal position for each pixel is made by Newton’s method with this APF. As 1 picometer is set for the truncation error of Newton’s method the system can calculate the surface topography with 1 picometer vertical resolution. The traceability of surface topography data using an 8 nm Standard Step Height Sample certified by NIST is shown in this paper. Sample data of a super smooth SiC wafer are also presented. This system allows us to get surface topography data by scanning once while other White Light Interferometry Systems require many scans for averaging to reduce the system noise. Not only will it measure super smooth surfaces but also very rough surfaces such as a ceramic bump without any changes of system configuration or parameters. This system will contribute significantly to the efficiency of the study of materials science.

Ryszard Jablonski
MEASUREMENT OF CYLINDER DIAMETER BASED ON SUPERPOSITION OF LASER BEAMS

Nanotechnology approaching the sphere of quantum mechanics has a lot of limits connected with indirect definition of base, which should be directly related to physical constants and laws. It takes place also in measurements based on superposition of laser beams. Commonly, laser diffraction is considered to be a precise technique to measure dimensions of 3D objects, however, when required accuracy is on the level of 100nm the existing solutions do not fit to engineering applications.
T. Young interpreted the diffraction phenomena as a result of interference of the geometrical wave propagating in free space with “the edge wave”. A. Rubinowicz theoretically proved the possibility of division the Kirchhoff diffraction field into two components: incident wave and reflection wave – created by interaction between primary field and the edge of object. These mathematical considerations are commonly accepted in the scientific world, but were never proved experimentally.
In the paper the diffraction on cylindrical object is considered. Two assumptions for the theory were introduced: extensive source of light and spatial aperture in form of cylinder. The modification of the diffraction equations allowed calculating and plotting the diffraction wave with its components, and it can be considered as the first calculation and graphical representation of the real diffraction process based on Young-Rubinowicz theory.
The obtained results can be used for determination the position of the edge of an object and lead directly to the development of diameter measurement method based on strictly defined physical phenomenon.

Li Menglin, Xie Wenfeng, Zhu Jingguo, Ren Jianfeng, Xiao Fang, Meng Zhe
THE ANALYSIS OF DIGITAL PHASE-SHIFT MEASURING METHODS FOR DUAL-FREQUENCY LASER RANGE FINDER

Phase-shift range finder is to measure the phase-shift of the modulation wave during its propagation. The precision of traditional phase-shift range finder is limited by measurement rate and the modulation depth. Usually the modulation depth of laser diode decreases with the increase of modulation frequency which is crucial for high precision with sinusoidal modulation. A new phase-shift range finder with dual-frequency He-Ne laser is introduced. The error model is built in order to analyze the factors influencing the precision of phase-shift laser range finder.
Two digital phase-shift measuring methods are discussed through the principle simulation. The white noise, the frequency offset and other error factors are introduced during the simulation. Then the measurement performances on all-phase spectrum analysis method and a new sub-sampling spectrum analysis are analyzed. The simulation results indicate that all-phase spectrum analysis method is advantageous for high speed and high accuracy measurement, owing to its better performance in error immunity. The sub-sampling spectrum analysis method reduces the hardware requirement and the simulation results show that the accuracy of phase-shift measurement can reach to the Cramer-Rao limit.

Yao Huang, Zi Xue, He Yan Wang
CALIBRATION OF INVAR ANGULAR INTERFEROMETER OPTICS WITH MULTI-STEP METHOD

In National Institute of Metrology, China (NIM), the Small Angle Measuring System which is based on sine principle, is developed as the national primary standard for the plane angle in the angular measuring range ±5°. The measurement uncertainty of this system is dominated by the accuracy of an Invar Angular Interferometer Optics. To calibrate this Invar Interferometer system, a series of known reference standards were given with multi-step method using a double-deck rotary table. The calibration got an uncertainty lower than 0.03 arcsec (k = 2).

Page 391 of 977 Results 3901 - 3910 of 9762