Key Engineering Materials Vols. 364-366

Abstract: Four-mirror systems with a very large aperture and a long focal length were investigated and designed. Their design idea is given. Through the derivation of primary aberration formula, the aberration properties were analyzed and discussed, and the method to determine its initial structure is reported. As examples, two four-mirror systems with spherical and parabolic primary mirror, 100m focal length, and 10m entrance pupil were optimally designed. Their imaging quality approaches diffraction limit within field of view of 0.4 and 0.5 degrees respectively.

Abstract: A high dynamic range image camera (HDRI) is a kind of camera which captures the HDRI image. HDRI means the image with high dynamic range, it can record the gray information of the object with much wider dynamic range. HDR image has great applications in many fields. The existing HDRI camera needs either the special image sensor or can capture the still object only. In this paper, a new kind of camera is proposed. In this camera, a space light modulator (SLM) is used to acquire images with different exposure, then a HDRI is made with these images. This camera can acquire dynamic image and it is cheap and easy to extend.

Abstract: In PIS (Programmable Imaging System) testing, where the spatial frequency of the spatial light modulator is inconsistent with that of the image device, Morie Fringes are generated. To further develop the PIS instrument, it has to abate the effects of Morie Fringes on the image quality. In this paper, we implemented an approach using spatial filtering in the Fourier Spectrum. Since “ringing” phenomenon is caused by the “notch filter”, to prevent it, a multiple-point Gauss Filter based on the “notch filter” has been designed. The tests have indicated that this approach can efficiently reduce the effects of the issue on the image quality, and the images reconstructed are clear and almost free from “ringing”,thus reaching the requirements for the instrument.

Abstract: Based on the analysis of characteristics of progressive lens, it can be found that lens uneven change of curvature is an important reason of defect on progressive lens processed by single-point diamond cutting technique. By applying least square fairing method to fair the surface which is fitted and interpolated by Double Cubic B-Spline method, the curvature change of progressive surface becomes even. The processing experiment shows that the method in this paper can eliminate the defect effectively in the ultra-precision processing of progressive lenses.

Abstract: In this work, an FPGA hardware based image processing algorithm for preprocessing the images and enhance the image quality has been developed. The captured images were processed using a FPGA chip to remove the noise and then using a neural network, the surface roughness of machined parts produced by the grinding process was estimated. To ensure the effectiveness of this approach the roughness values quantified using these image vision techniques were then compared with widely accepted standard mechanical stylus instrument values. Quantification of digital images for surface roughness was performed by extracting key image features using Fourier transform and the standard deviation of gray level intensity values. A VLSI chip belonging to the Xilinx family Spartan-IIE FPGA board was used for the hardware based filter implementation. The coding was done using the popular VHDL language with the algorithms developed so as to exploit the implicit parallel processing capability of the chip. Thus, in this work an exhaustive analysis was done with comparison studies wherever required to make sure that the present approach of estimating surface finish based on the computer vision processing of image is more accurate and could be implemented in real time on a chip.

Abstract: Dimming control is used for energy saving scheme in most of the general lighting system. There are different kinds of dimming control methods in the lighting device. This paper aims to provide a general discussion on the power circuit to lighting up the LED devices and it also discusses the possible way to dim the LEDs. Moreover, this paper based on the 3W high power LED and aims to find out the best operating factors that can fully utilize LED and to provide best energy saving scheme.

Abstract: Ultra-precision raster milling (UPRM) can directly achieve the fabrication of threedimensional non-axisymmetric freeform components with nanometeric surface finish and submicrometric form accuracy. During the past few years, a lot of research on computerized numerical control (CNC) machining technologies has been conducted; however, little of this research makes any contribution to UPRM. This paper studies the mechanism of scallop height generation for UPRM. Through analyzing the cutting edge locus and the scallop height generation mechanism, a model for feed-intervals and for raster-interval scallop height generation, are presented. Parameters such as selection of feed direction (vertical cutting and horizontal cutting), feed rate, spindle speed, tool nose radius, swing distance, feed length and raster distance have been taken into consideration in the scallop generation models.

Abstract: To analyze the effects of fabrication and alignment errors on optical systems with complex apertures such as a segmented telescope, a visual basic routine (VBR) is developed using CODE V’s COM interface. One of the eminent features of this VBR is its graphical user interface (GUI). The GUI facilitates the user to model different types of segmentations quickly and precisely. The input parameters describe the basic shapes of the segments (polygon or sector), the chamfers at their corners, and the gaps between them. Fabrication errors (i.e. surface errors and alignment errors such as decenters and tilts for each segment) can also be introduced easily and effectively through the GUI. Geometrical and diffraction-based analyses can then be performed to study and analyze the effects of these errors on the imaging quality of the optical system. Results of tolerance analysis are presented for a test system, which require a very stringent tolerance to be placed on the discrepancy among the radii of curvature for different segments. In short, the VBR is a user friendly and a flexible tool with its application scope in designing complex aperture optical systems.

Abstract: In this paper, a framework of surface generation model in the fast tool servo (FTS) machining of optical microstructures will be described. The integrated model is totally composed of a tool path generator (TPG), a surface topography model (STM) and an optimization model (OM). To develop the tool path generator, two parts should be involved. The first part is the tool path generated based on cutting conditions such as the feed rate and spindle speed, the geometry of optical microstructures, and diamond tool geometry. Another part is the synchronized motion generated by the tool actuation of the FTS at a bandwidth higher than the rotational frequency of the spindle. The surface topography model will be generated based on the TPG and used to predict the technological aspects of FTS machining. It takes into the account the kinematic and dynamic characteristics of the cutting process. The former includes the tool path generated by the tool path generator. The later includes the relative vibration between the tool and the workpiece caused by the axial error motion of the spindle as well as the synchronized motion of the FTS system. The optimization model will be undertaken by an iterative algorithm, which will be developed based on the TPG and STM. The OM will be expected to output the verified tool path, the suggested optimum cutting conditions, and the diagrams with predicted cutting performance characteristic and process parameters being investigated. Eventually, the successful development of this surface generation model can contribute for the knowledge of ultra-precision machining with FTS and the further development of the performance of the machining system.

Abstract: In this study, ageing effect for xenon through experiment has been studied. The study focuses on the modeling, ageing characteristics of xenon car headlight. The modeling of the lamp is based on spline interpolation algorithms. In this model, the voltage drop at the electrodes is considered as the aging factor. Ageing characteristics under the flicker condition for 4 types of xenon car headlight lamps have been measured. The flicker time is 4 seconds turn on and 2 seconds turn off, and the total testing time is 48 hours. The luminous, voltage and current of the lamp are measured. It is found that even a short period of flicker significantly affects the life time of the lamp.