Key Engineering Materials Vols. 364-366

Abstract: The rate of increasing storage capacity is being slowed by the inability to produce ever closer flying heights between the sliders and disks. In order to allow the sliders to ‘fly’ faster and more closely to the disk surfaces, it is important to control the surface of substrates of hard disks to a super-smooth level. However, there are no sophisticated instruments and assessment standards for super-smooth surfaces. In this research, the authors attempt to build a measurement and assessment protocol for the evaluation of super-smooth surfaces using a white-light optical instrument CCI (Coherence Correlation Interferometer). The key advantage of this instrument is its exceptionally high vertical resolution which is an order of magnitude better than comparable systems. This paper focuses on discussing the factors influencing the experimental results; they include sampling intervals, the number of measurements, scan size, filter cut-off wavelength etc. Based on the experimental results, an optimum protocol for measurement and assessment are recommended, and then the authors measure and compare the surface roughness of six hard disks derived from differing chemical mechanical polishing (CMP) ‘abrasives’. It has been found that: (1) the roughness values of the six hard disks surfaces have all reached a sub-nanometre level; (2) CMP regimes have little influence on the topography of the hard disk surfaces.

Abstract: Based on the beam coherence-polarization (BCP) matrix approach and propagation law of partially coherent beams, the propagation properties of partially polarized Gaussian Schell-model (PGSM) beams through an aperture lens with spherical aberration were studied. Our main attention was focused on the effect of spherical aberration of the lens, partial coherence, aperture diffraction and polarization on the behavior of the irradiance. The numerical calculation results are given to illustrate how these parameters affect the focusing properties. A comparison with the previous publications is also made, showing some extension has been made in our work.

Abstract: The coupling of laser with fiber has been used for many fields: such as industry, medical treatment, and communications. At the present time, the coupling methods are direct coupling and lens coupling mainly. With the existence of a damage threshold in fiber end face and interior, it very difficult to use the above ways to realize the coupling of high-power, high-energy and narrow pulse laser with optical fiber. In this paper, a new method to reducing laser power density and energy density in optical fiber end face and interior is presented and designed a hollow cone shaped laser-fiber coupler by analyzing the mechanism of damage of optical fiber. When cylindrical Gauss beam incident into the hollow cone coupler will form a light spot, the energy density is of quasiaverage distribution. By using this coupler, we realized the coupling of a high-power (10MW), energy (12mJ), narrow pulse (12ns) and electro-optical Q-switched Nd:YAG laser with the multimode optical fiber (diameter is 600μm) and the coupling efficiency is 70%.

Abstract: This paper presents the inspection technology for a freeform surface component which is named F-theta lens. F-theta lens is widely used in laser scanners, printers, etc. Freeform characterization is one of the main approaches to verify the manufacturing precision of freeform surface. At present, there is still a lack of techniques for the characterization of freeform surfaces. This study aimed to explore some approaches to inspect freeform surfaces. Two types of measurement methods, namely contact and non-contact measurement methods, are employed to measure the F-theta lens surface. The pros and cons, the existing problems, different applications and areas for improvement of the two methods are discussed. A series of advanced measuring instruments are used in the measurement process. A brief description of measurement mechanisms of these instruments is also presented. As a whole, this paper contributes to the development of the precision measurement technology for optical freeform surfaces.

Abstract: In order to obtain competitiveness in the field of industrial manufacturing, a reduction in the development period for the batch machining of products is required. It is essential to analyze the stress distribution and deformations of machining system which is used for manufacturing the aspheric lens using FEM software ANSYS. Finite element simulations have been performed in order to study the influence of machining system which was developed in this study on structures. It is very important to understand the structural behavior of machining system. This research investigated the static analysis and dynamic analysis of machining system for aspheric lens to predict the damage due to loading.

Abstract: This paper reports a novel micro extrinsic fiber-optic F-P interferometric (MEFPI) sensor micromachined on a conventional optical fiber (Corning SMF-28) by using a near-infrared femtosecond laser, for the first time to the best of our knowledge. The strain and temperature characteristics of such a sensor were investigated and the experimental results show that the strain and temperature sensitivities are 0.006nm/με and -0.0017nm/°C, respectively. This type of MEFPI sensors has a number of advantages when compared with conventional EFPI sensors, such as easy fabrication, high integration degree, good reliability, low temperature cross-sensitivity, low cost, and capability for mass-production, offering great potential for a wide range of sensing applications.

Abstract: Aberrations of the human eyes in the horizontal visual field were measured with modified Hartmann-Shack wave front sensor. The characteristic of third to tenth order Zernike aberration rms both temporally and nasally out to 50° is as follows: considerable differences occur among subjects in the pattern of aberrations, particularly for the dominating second-order aberrations; the third to tenth order Zernike aberrations increase with the visual angle, but the increscent magnitude decreases as the Zernike order increases; in despite of imperfect symmetry, the increscent magnitude is the same on the whole; the third-order Zernike aberrations increases up to 2 times from 0° to ±50° visual angle, the forth-order up to 1.8 times, and the fifth to tenth order up to 1.7~1.3 times.

Abstract: This research aimed to develop a novel two-stage micro injection compression molding (μ-ICM) process for fabrication of plastic diffractive optic elements (DOE). The DOE was designed with the spherical coefficients and the Fresnel lens. A piezo actuator was installed inside the mold plate for activating the mold insert for the second compression motion for micro ICM of the DOE lens. The first experiment proceeded to find the operation window of Fresnel lens and then compare the product weight of flat spherical lens by injection molding (IM), injection compression molding (ICM) and μ-ICM. The second experiment was to investigate the effectiveness of micro compression activated by the piezo actuator by the transfer ratio of grooves (TRG) of the DOE lens with spherical lens and Fresnel lens. Results showed that the μ-ICM of the DOE can obtain the highest TRG than that of IM and conventional ICM processes. Therefore, results of this research can be explored to related aspheric optical elements with micro features, such as fine lens used in the zoom lens of camera.

Abstract: Manufactured miniature parts conventional machine tools are substituted by mini-scale manufacturing system called miniaturized machine tool (mMT). However, calibration of mMT is extremely difficult due to its small dimensions. This paper presents a novel optical measuring system to measure integrated geometric errors namely a) three translation errors and b) three rotational errors. The squareness error between two moving axes was calculated by least-square method. These 7-DOF geometric errors were acquired simultaneously in one setup for each motion direction. The proposed measuring system consisted of two laser diodes, two beam splitters and three 2D position sensing detectors (PSDs). Configuration of this measuring system was proved by homogenous transformation matrix (HTM), and the relationship between PSD readings and geometric errors calculated by the algorithm were derived according to the configuration. Simulation were carried out to prove the validity of this algorithm. Sensitivity analysis based on mounting errors of system components is also presented in this paper. It is useful for further experiments in alignment of system components.