Key Engineering Materials Vol. 625

Abstract: This paper will develop an automatic and fast optical measurement system for high density optical fiber connector measurement, which base on the optical project method. It will meet the lot of optical fiber connector measurement need. This system includes a high intensity and high collimated LED source, a high accuracy and high stiffness linear stage, 2 multi-degree-of-freedom adjustment mechanisms and a high resolution coaxial telecentric imaging system and image processing software. The system of measurement results and commercial measuring instruments comparing the results of its error is less than 0.6μm. To measure a V groove needs 750ms, this result may satisfy the requirements of automatic inspection.

Abstract: There is a strong demand to measure an absolute surface profile with a few nanometer uncertainty. The National Metrology Institute of Japan (NMIJ) measure the absolute surface profile using two instruments based on difference methods: the Fizeau type flatness interferometer and the scanning deflectometric profiler. In the Fizeau type flatness interferometer, the measurand is a gap distance between a reference flat and a specimen. To obtain an absolute profile of the specimen, the reference flat was evaluated by a three flat test and a FEM analysis. The three flat test is one of the methods to measure absolute profile of a reference flat; however, the reference flat deforms under the force of gravity, and its absolute value cannot be detected by the three flat test. The deformation value of the reference flat was calculated by the FEM analysis. In the scanning deflectometric profiler, a local slope angle of a specimen is measured using an autocollimator and the surface profile is obtained by integrating with the local slope angles. To obtain an absolute profile of the specimen, the autocollimator which is key elements for the scanning deflectometric profiler was evaluated by using the self-calibration type rotary table. In this paper, we performed the comparison measurement between the Fizeau type flatness interferometer and the scanning deflectometric profile and verified the accuracy of the two instruments based on the different methods.

Abstract: When optical waves make the free electrons on a metal surface resonate, optical energy propagates along the surface as density waves of the free electrons. The longitudinal waves and electrical fields of the electrons are called surface plasmon polaritons (SPPs), which are widely applied in high sensitivity sensors because the excitation of SPPs sensitively depends on the refractive index of the surrounding dielectric sample. Here, we report the identification of fluids by using the color dispersion of SPPs. Silver film on a prism surface is illuminated with white light to excite SPPs. A color component in the white light is thereby selectively coupled with SPPs due to the color dispersion that depends on the refractive index of the fluid on the film. Thus, theoretically, when the refractive index is changed, the color of SPPs changes as well. Our application uses a medium consisting of fluid samples to be identified. The proposed identification method can be applied to fluid analysis for label-free visualization of or as a simple analysis method, since the refractive indices or concentrations of the sample fluids directly affect the color of the SPPs, and this color can be visually identified. We theoretically confirmed that the color of SPPs excited with white light illumination can help to differentiate between water and ethanol. Experimentally, SPPs belonging to the frequency region of the color green were detected when the sample was water, and the color changed to red when ethanol was used instead. In the future, we plan to develop simple, small, sensitive, and low-cost sensors that can determine the concentration and refractive index of fluids on the basis of the color of the SPPs.

Abstract: High-precision length measurements are strongly demanded for not only industry requirements and science purposes.In 2009, a femtosecond optical frequency comb (FOFC) was adopted in Japan as the national standard tool for measuring length. Recently, numerous studies have focused on FOFC-based high-precision length measurement because this approach offers the possibility of development of a ultimate green length traceability system. A single-wavelength helium–neon (He–Ne) laser was used as a length standard. An FOFC emits discrete pulse-train-shaped light. This markedly different characteristic exists between a He-Ne laser and an FOFC is the reason for the challenge. Previous attempts to challenge this problem have not been satisfactory. This has limited the development and applications of FOFC-based length measurement. In this work, we review our efforts of FOFC-based high-precision length measurement toward developing an ultimate green length traceability system.

Abstract: The development of micro-nanomanufacturing technology leads to higher requirement for measurement technology, which gives birth to the ultra-precision measurement technology. As a kind of low coherence interferometry technology, spectral interferometry has been proposed. In this paper, the theory and system of white light spectral interferometry were described in detail, and the measurement principle of micro-structure was analyzed. The spectral interference signal was recorded and the phase information was retrieved from it by using five-step phase shifting algorithm, which includes the phase change on reflection from the stucture. So the optical path difference (OPD) can be obtained, which represents the height information. Three methods including slope method, single wavelength method and least square method were discussed based on the theory deduction and the experimental analysis. A step height standard was measured and the results show that this method has a good accuracy.

Abstract: Surface with nanometer accuracy is required to manufacturing process of integrated circuit (IC) devices. One of the most promising techniques for surface planarization is chemical mechanical polishing (CMP). CMP is a high efficiency process, both due to the varied chemical and physical properties of the surface materials. Conventional CMP uses the slurry, which is composed of abrasive particles suspended in a chemical solution. The abrasive particle is effective for surface planarization by a chemical mechanism with little mechanical abrasion. So chemical reactivity appears to be an essential factor of CMP process. In our conventional study, fullerenols have been proposed as suitable abrasives for copper CMP. The chemical reactivity of fullerenol is suggested by the fact that high removal rate (150 nm/min) and surface flatness (0.6 nm RMS) have been confirmed using fullerenol slurry. In this study, we analyzed the chemical reactivity between fullerenol molecule and copper surface, which is important to understand the material removal mechanism. Using the intrinsic Raman spectroscopic signal of interaction between fullerenol and copper with surface plasmon resonance (SPR), the chemical reactivity over a period of the reaction process was analyzed. Raman spectroscopy is commonly used in chemical analysis, since vibrational information is specific to the chemical bonds and symmetry of molecules. Therefore, it provides a fingerprint by which the molecule can be identified. However, spontaneous Raman spectroscopic signal is typically very weak, and as a result the main difficulty of Raman spectroscopy is separating the weak inelastically scattered light from the intense Rayleigh scattered laser light. Then Raman spectroscopic signal in this study is further enhanced by the SPR, also known as surface enhanced Raman scattering (SERS). The increase in intensity of the Raman spectroscopic signal for adsorbates on copper surface occurs because of an enhancement in the electric field provided by the surface. This technique enables high-sensitive analysis in the near-surface region. The signature of copper-oxygen bond was measured by Raman spectroscopy for fullerenol/copper system by in-process SERS analysis. It is thought to be caused by the hydroxyls of fullerenol molecule adsorbed on the copper surface. This result suggests that fullerenol molecules absorbing onto the copper surface affect the high efficient material removal.

Abstract: Corrector lens assembly is used to expand the field of view of a Cassegrain Telescope. There are usually three to five lenses in it. For the assembly of such a kind of high precision optics, decenter and tilt of each optical component and air space between components are key issues to be qualified. In the present study, four lenses were designed. Individual control of centering of the component and air space were achieved by assembling the component into a precision machined subcell. The lens positions were defined by precision spacers according to the designed values. To compensate various thermal expansions of glass and metal, elastomer material was used. Considering the deviation of manufacturing from design data, manufactured data were put into optical software for re-optimization, and air spaces between lenses were obtained. This gives excellent accuracy at low cost. Base on present lens mounting design and lens manufacturing quality, centering error was eliminated by lateral adjustment, which leaded to a good alignment. In this paper, the method for aligning the optics with the barrel assembly is presented and centering error measured by a double autocollimator is listed. In addition, test results of thermal cycling and vibration tests on the corrector lens assembly are discussed.

Abstract: In this paper, to release this induced errors and improve the accuracy of the measured data, a new spatial synchronization method is proposed to spatially synchronize the three-dimensional surface data sets obtained by variety surface topography measuring instruments. The proposed spatial synchronization method minimizes the geometrical error components using the data interpolation, the least squares method, and the two-dimensional cross correlation function. For verification of the method, it was applied to the measured data sets measured with a chromatic confocal microscopy, a laser scanning confocal microscopy, and an ellipsometer. Based on the experimental results, the accuracy or the proposed method is analyzed and evaluated.

Abstract: Bamboo grows faster than other renewable natural materials. Bamboo fiber, in particular, has attracted attention as an environmentally superior material. Therefore, we propose a sustainable manufacturing system using bamboo. A method is also proposed for extracting bamboo fibers end-milled using a machining center with in-situ measurement. Bamboo fibers with highly precise shapes are efficiently acquired. Previously, we proposed the fabrication of a binder-free composite by a hot press forming method that only uses bamboo fibers extracted by a machining center. We experimentally demonstrated various hot press forming conditions and achieved proper ones to optimize the forming process. However, we have not yet constructed a method to obtain the best fiber extracting and molding conditions considering both its efficiency and performance. Therefore, in this report, we investigate the influence of the length of used bamboo fiber on the characteristics of the molded products, as its length deeply affects the extracting efficiency and focuses on a degradable plastic as a standard of molded product strength.

Abstract: The study deals with an automation of the metal hammering process by use of a linear motor on the basis of CAD data. Metal hammering is one of a traditional handcrafts and only skilled technician can form objective shape from a blank sheet metal without die/mold. It shall be regarded as a type of rapid manufacturing process that is it can be applied to make small amount of sheet metal part. However, to master metal hammering is difficult because of its intricate forming procedure. In this study, a linear servo hammering system, which developed in-house, is adopted as a good mimic of human hammering operation. We have already proposed a calculation method of form difference between workpiece and its CAD data quantitatively in order to assess how workpiece formed accurately and to identify primary factors for the formability. Previous version of our own developed hammering system could form workpiece without considering temporary shape of workpiece with feed-forward control. The operator had to try several times to obtain optimal hammering condition for different shapes of CAD data. It is one of the major differences in comparison with the skilled human operators do. In the study, the authors improved the hammering system to measure shape of workpiece in hammering process. This modification made hammering process to be able to feedback temporary condition to form more accurately. From the experimental result, robustness of the system performance for input shape, compared with that previous system requires several experiments to determine hammering parameter has been demonstrated.