Yasuhiro Takaya

Measurement of axial and transverse trapping stiffness of optical tweezers in air using a radially polarized beam

The trapping efficiency and stiffness of optical tweezers using radial polarization are evaluated; the ray-tracing method and a proposed measurement method are used for numerical and experimental analyses, respectively. The maximum axial trapping efficiency with radial polarization is 1.84 times that with linear polarization, while the maximum transverse trapping efficiency decreases by 0.58 times. Further, the axial and transverse trapping efficiencies are found to be 1.19 times larger and 0.83 times smaller, respectively, than the values with linear polarization. From the experiments, the axial and transverse stiffness values are 1.2 times larger and 0.8 times smaller, respectively, with radial polarization. Hence, radial polarization enhances the axial trapping properties while reducing the transverse trapping properties.

Development of The Nano-CMM Probe based on Laser Trapping Technology

Abstract The 3D nano-position sensing probe serves as an important technology in the development of the nano-CMM used in microfabrication systems. This paper discusses the laser trapping probe whose principle is based on the dynamic properties of optically trapped particles and the Linnik microscope interferometer. Its potentials as a nano-CMM probe were investigated in fundamental experiments. Single-beam gradient-force optical traps of silica particles in air were successfully demonstrated by using an object lens with N.A. of 0.80. Positional detection accuracy of 30nm was also confirmed through measurements of fringe changes with the shifts of the probe sphere.

Vibrational Probing Technique for the Nano-CMM based on Optical Radiation Pressure Control

Abstract A microprobe system with a micrometer size probe sphere is required to establish the nano-CMM that is a three dimensional coordinate measuring machine with a measuring range of mm and accuracy of nm order. In this paper, the newly developed vibrational probing technique for the microprobe sytem is presented. The principle is based on the single-beam gradient-force optical trap and the forced vibration method. An optically trapped silica particle in air is vibrated using the laser beam scanning method. Frequency response is examined to estimate the radial spring constant of the microprobe system. Fundamental measurements of a micro-step specimen fabricated using a FIB (Focused Ion Beam) process are demonstrated to investigate the position detection sensitivity.

Roll-to-roll fabrication of a low-reflectance transparent conducting oxide film with subwavelength structures

The transparent conducting oxide (TCO) film is a significant component in flat panel display, e-paper and touch panel. The tin-doped indium oxide (ITO) material is one of the most popular TCOs. However, ITO has high refractive index, so the phenomenon of high-reflectance limits the wide use of ITO. In this study, the structure and mass production process of new low-reflectance TCO film is verified. Laser interference lithography and the roll-to-roll UV embossing process are used to fabricate subwavelength structures on PET film; then ITO was deposited on structures by roll-to-roll sputtering. When the dimension of structures reaches 300 nm pitch, the optical reflectance and electrical performance of film are reduced to 8.1% at wavelength 550 nm and its transmittance rate is 84.3% at the same wavelength, and the sheet resistance of this film is 50.44 ?/?. This result indicates that the new TCO proposed in this study is suitable for touch panel and other display applications.

Probing technique using circular motion of a microsphere controlled by optical pressure for a nanocoordinate measuring machine

A new surface probing technique using the circular motion of an optically-trapped microsphere is proposed for a nanocoordinate measuring system. The probe sphere is oscillated circularly in the plane perpendicular to the probe axis and the circular orbit of the probe sphere is monitored for the detection of the position and normal vector direction of the surface. The principle of detection is based on changes in the circular orbit of the microsphere. When the probe approaches a work surface, the orbit of the probe sphere becomes elliptical. The minor-axis length and the minor-axis angle of the ellipse are then used as parameters to detect the position and normal vector direction of the surface, respectively. In this study, the circular motion probe is shown to have a resolution of position detection of 39 nm, and the accuracy of measuring a normal vector to the surface is on the order of 3 degrees.

Nano position sensing based on laser trapping technique for flat surfaces

The main purpose of this study is to develop a nano-CMM (coordinate measuring machine) that can measure three-dimensional shapes of a micro component. An improved probe is the key for achieving the nano-CMM. Subsequently, we propose a laser trapping probe, which is an optically controlled glass micro-sphere based on the laser trapping technique. In the coordinate measurement of a flat surface using the laser trapping probe, the measurement uncertainty is increased due to the influence of a standing wave. In this paper, the position sensing properties and accuracy of the laser trapping probe along the direction of the laser axis are experimentally investigated for measuring flat surfaces with low uncertainty. The influence of the standing wave results in a positional fluctuation and resonance frequency shift of the probe. However, this positional fluctuation of the probe is highly repeatable. It is found that the laser trapping probe can sense the specimen surface by adjusting to an appropriate oscillation frequency. Consequently, the laser trapping probe could determine a surface position with a repeatability of ±64 nm.

Nano-Position Sensing Using Optically Motion-controlled Microprobe with PSD Based on Laser Trapping Technique

Abstract A position sensing microprobe has been developed which satisfies harsh requirements to establish a nano-CMM (coordinate measuring machine) proposed for measuring microparts with a target accuracy of less than 50 nm within a 10 mm cubed working volume. This paper deals with dynamic properties and position sensing accuracy of the improved microprobe system for the nano-CMM using an optically trapped probe sphere of 8.0 ^m in diameter. The probe sphere is forced to vibrate with about a hundred nanometer amplitude and high frequency based on optical radiation pressure control. It is possible to measure its dynamic motions with a higher accuracy using the newly developed optical system with a position sensing detector (PSD). It is experimentally suggested that the improved microprobe system can achieve nano-position sensing in the lateral direction.

High-precision on-machine 3d shape measurement using hypersurface calibration method

We present a high-precision fringe pattern projection technique based on a novel 4D hypersurface calibration method, and its application to on-machine measurement of raw-stocks in die-making industry. Our fringe pattern projection technique has the following feature. In the calibration stage, coordinates (x, y) of a CCD image sensor correspond uniquely, for every calibration plane with height Zi (i=1,..,n), to a phase φ of a projected fringe pattern, and coordinates (X , Y) of a machine tool. These relationships are converted to hypersurfaces in 4D spaces of (x, y, Z, φ), (x, y, Z, X), and (x, y, Z, Y), which are considered to be a sort of function. Using these hypersurfaces, a measured data of (x, y, φ) is transformed to machine tool coordinates (X, Y, Z). Our hypersurface calibration method is expected to minimize systematic errors, because it inputs an observed data (x, y, φ) into precise interpolation functions created using actual measurement data, and accordingly systematic errors are cancelled. The repeatability, systematic errors, and random errors obtained from the experiment show that our measurement system has a potential for highly accurate non-contact 3D shape measurement.

Fundamental study on the new probe technique for the nano-CMM based on the laser trapping and Mirau interferometer

The nano-CMM as a coordinate measuring machine for micron-sized 3-D shapes is required to satisfy the measuring range of about a cubic centimetre and the accuracy of less than 50 nm. In order to develop such a nano-CMM, the probe with a microsphere must achieve detecting accuracy of nanometre order and a contact pressure force of less than 10−5 N. In this paper, a new probe technique for nano-CMM using a laser trapped microsphere is proposed. The principle of measurement based on the laser trapping technique and the microscope interferometer is presented. Computer simulations of radiation pressure force are performed to develop the laser trapping probe experimental system. Three-dimensional trapping of a microsphere is achieved. The contact position is estimated by measuring the displacement of the microsphere.

In-Process Measurement Method for Detection and Discrimination of Silicon Wafer Surface Defects by Laser Scattered Defect Pattern

Abstract A new optical measurement method for evaluating the defects on a silicon wafer surface quantitatively, which will be able to be applied to in-process measurement, is presented. The experimental system for measuring the defects consists of the Fourier transform optical system using of a high-power objective. In order to verify the feasibility of application of this method to in-process measurement, scanning experiments for small particles, which are typical defects on the silicon wafer surface, are carried out. It is shown that the proposed method is effective for detecting and discriminating the small defects with the size of sub micrometer order.