The national standard of length in Japan changed from the iodine-stabilized He–Ne laser to a femtosecond optical frequency comb (FOFC) in 2009. This means that there are different frequencies and their combination, adjacent pulse repetition interval length (APRIL), which can be used as a scale since an FOFC is a phase-coherent combination of several hundreds of thousands of wavelengths. Thus, the following questions arise naturally: Which parameters can be used as a scale? What are their characteristics? The goal of this paper is to answer these questions. We show the similarity and the difference between wavelength and APRIL for length measurement, and we discuss new concepts of APRIL-based length measurement. The status of the experiment is reported.

This paper discusses the analysis and optimization of a novel optomechanical zeroth-order grating transducer based on an anomalous diffraction phenomenon, namely Wood’s type anomaly, in which tiny changes in the displacement of the nanostructured grating elements lead to a dramatic increase or decrease of the optical reflection amplitude. With this special feature, this structure is an ideal sensor component to observe very small displacement. This device is very sensitive to wavelength, the period and the width of the grating. Here, we analyze the performance of the structure with different parameters and optimize the original structure corresponding to 850 nm through 3-D Finite Difference Time Domain method (FDTD). Simulation demonstrates the new structure is of higher sensitivity and signal strength, namely extinction ratio. Moreover, in order to enlarge the tiniest size of the original structure which is closely related to the incident wavelength, we change the wavelength to longer ones, e.g. 1053 nm, 1310 nm, 1530 nm. The calculation predicts the optimized structure designs of those wavelengths are of performance similar to the original one’s but much less strict demand for processing precision, which makes it possible to be fabricated with current surface micromachining processing similar to that used for the fabrication of polysilicon MEMS. Besides, structures of several visible incident wavelengths, such as 532 nm, 632.8 nm, 670 nm, 753 nm, are also analyzed and optimized, which gives great convenience to the installation and calibration of such device as well as observation of its performance. All the calculated data enable us to apply the structure into fields required for different sensitivities with different grating designs and thus broaden the further usage of such novel structure, as structures of different parameters are of different sensitivities and signal strengths.

In recent years, high-resolution microscopy using structured illumination has been practically applied for fluorescent bio-imaging. However, there is a large amount of speckle noise in reflected- and scattered-light images, because structured illumination is typically generated by laser-beam interference. Hence, this high-resolution imaging technique cannot be effectively used in industrial applications. In this study, we attempted to generate structured illumination using two-beam interference of low-coherence light, and to develop a high-resolution and low-speckle imaging technique for industrial applications. First, we constructed an optical system consisting of a Michelson interferometer configured in such a manner that it achieved zero optical path-length difference and allowed the interference fringes to be manipulated. Second, we observed a sample pattern of 0.2-µm-sized dots to confirm the generation of interference fringes under structured illumination. Then, we endeavored to observe other sample dotted patterns with several types of pitches. In one case, the pattern pitch of 0.4 µm was beyond the diffraction limit of 0.5 µm. In this experiment, we could obtain an image and observe the fringe patterns corresponding to features of low-coherence interference. The patterns show a moiré effect due to the combination of the periodic sample patterns and the structured illumination, and we confirmed that the moiré-pattern width corresponded to the coherence length of the light source. Finally, we reconstructed a resolution-improved image from an image stack resulting from spatial scanning of the generated structured illumination. As a result, the narrow pitch pattern of 0.4 µm was successfully resolved with relatively less speckle noise.

In order to realize efficient high-mix low-volume production, improvement of yield rate by reducing production flaw is important technique. Manufacturing of touch panel display with large scale wiring board is a typical example of the high-mix low-volume production. AIST has proposed Laser assisted Ink-Jet printing (LIJ) technology, which can repair the flaw of circuit with silver nanoparticle ink. To establish in-process repairing system for touch panel display, a first production flaw detecting system is demanded with combining to the LIJ technology. Therefore, the aim of this study is to develop a new first production flaw detecting system, which detects flaw of large-scale circuit quickly. In this report, we mention to a basic concept of proposed system, and performed some preliminary experiments using developed measurement systems. Demanded performance for first production flaw detecting system was discussed. And the concept of basic style of detecting system and optical set-up was selected. A preliminary first production flaw detecting system with galvano-scanner and multi photodiode array was developed to confirm a detection of flaws and pattern profile. Some basically experiments have been conducted to check the performance of this system. An imitated flaw was scratched on the circuit patterns and the experimental results show the sclatched flaw has been detected by this equipment. The height detecting technique for this system was mentioned and preliminary experiment using developed system. By using laser trigonometry method, displacement of height information was detected sufficiently.

To develop a micro tactile probe used with a micro coordinate measuring machine (CMM), a novel technique for detecting a three dimensional displacement of a small sphere with high sensitivity has been proposed. In this technique, a surface of a metal sphere is included as a spherical mirror in an optical system and changes of optical path arise from displacement of the sphere is detected with a sort of the astigmatic method. In the optical system, three eccentric collimated beams are generated and each beam moves parallel to the optical axis. The beam is converted to spherical wave by an objective lens and moving toward the focal point. At this time, if a spherical mirror (metal sphere) is placed in the position of which center falling on the focus, incident angles of all rays become right angle and reflected rays go back on the incident paths. On the other hand, if the spherical mirror moves from the point in the small distance, return path of each reflected ray is changed large. This change can be detected with the astigmatic method using a condenser lens and a CCD. The relationship between displacement along three axes and the change of the spot radius made by astigmatic method was calculated using a ray tracing code. As a result, the change of the spot shape was simulated only with the motion along one axis. This result shows the feasibility of three dimensional displacement detection by the proposed method.