Papers by Keyword: Charge Coupled Devices (CCD)

Abstract: Using high-resolution CCD chip and high-speed A/D converter chip, the design of the Video Communication System is given in this article, which successfully realizes the drive of the high-resolution area CCD and achieves the digital image signal. Based on the thought of SoPC’s (System on Programmable Chip) high integration, on the ALTERA company's DE2 platform, FPGA is used to achieve the driving timing of CCD, Silicon delay lines are used to properly align the pixel rate CCD clock signals with respect to one another, and the push-pull transistor circuits are designed to translate TTL level driving clock signal to the voltage levels required by the CCD. The system demonstrates some application values by analysis.

Abstract: With the development of the computer vision and information on optics, three-dimensional grating surface measuring apparatus has been increasingly widely used, which is mainly used in industrial inspection, quality control, reverse engineering, virtual reality, cultural reproduction and other areas. It has high precision, fast, non-contact advantages. And the image acquisition system is one of the core and first part of three-dimensional grating surface measuring apparatus, which determines measuring accuracy in the three-dimensional shape. This paper mainly introduces image acquisition system's hardware configuration and software development methods in the apparatus, and finally gives the experimental results.

Abstract: In this paper, a measurement system of temperature field in laser molten pool by CCD based on DSP is presented. The paper also presents the system of hardware, software process, and the method of image processing by DSP. To solve the real time problem in the processing of measuring the temperature field, the system uses DSP as the main CPU, processing the image without a computer. By this method, the system can become simple and efficient and measure the laser molten pool temperature field quickly and exactly. Gradient image of temperature field is displayed on LCD after real time processing by this system. The final picture of temperature field can be directly analyzed.

Abstract: This paper introduces a method of auto focusing based on fuzzy-control. Using this method, we design the scheme of optimization for focus. Variance function is used as approximately evaluate function for a large-scale in this system, and Square-gradient function is used as precise evaluate function in certain scale. Fuzzy-control is adopted the control of optimization for focus. The experiment testified that auto-focusing in this system is so accurate that accord with the required precision, and the image of collecting is clear. The machine of auto-focusing is simple, and the control of whole system is easy to implement.

Abstract: Laser direct manufacturing and re-fabricating have been used in many important fields in recent years. However, simulation and measurement of velocity fields in carrying gas and powder particles are still a challenge. In this paper finite difference method has been selected to simulate the velocity fields of powder/gas fluid. A novel DPIV system has been developed to measure the velocity fields. The DPIV system mainly consists of Nd+:YAG laser and CCD camera. Comparing the result of DPIV measuring with computer simulating, a good agreement can be obtained. After further developing, DPIV will become a useful device for laser manufacturing.

Abstract: This paper adopted the photoelectric micro measurement system based on CCD which was independently developed by Laboratory of Process Automatic and Detection Harbin Institute of Technology to detect dimension of the small precise parts. Under the various focusing status, it was discovered that articulation of focusing has huge effect on the measurement of measurand. According to the characteristics of measurand, we adopted the entropy function as the evaluation function of automatic focusing, developed a special software to process entropy value of the picked images, and obtained the relationship of focusing evaluation function and measurement error through a large number of experiments. The experimental result effectively verified the effect of articulation of focusing on dimension measurement.

Abstract: The profile and temperature distribution of laser molten pool are mainly factors which have directly effect on quality of laser processing (laser melting and laser cladding). It is very necessary to study measurement method of melting process in laser molten poo1 on-line, for improving processing design and inspecting laser processing quality. A system of dynamic process measurement for laser molten pool was developed. The melting process of laser scanning molten pool formed by high power CO2 Laser was measured. Its temperature distribution was analyzed by special analysis software. It was shown that a section of integrated molten pool would come into being in the middle of the laser scanning line spot after a period of scanning time, and then the molten pool got increased in length with the time, and a little increased in width at the same time, the result was consistent with that of computer numerical simulation. Compared with laser focusing spot, laser scanning spot was more uniform in temperature distribution, that could be propitious to improve the quality of laser processing.

Abstract: The detection technique of small module gears has a very important research and application value. In this paper, a composite measuring method is presented based on combining traditional mechanical contact measurement with optical image non-contact measurement. First of all, this paper analyzes the basic principle of composite probe composed of optical fiber stylus and CCD imaging system. The tail-end of the stylus is shaped into a micro-sphere, where a small refection mirror is designed. When the laser is transmitted through the fiber, a round facula can be seen from the CCD camera. The micro-sphere is kept contact with the surface of the measured gear at the time of measuring and the error of the measured gear will be reflected by the offset of the facula center. Meanwhile, the sub-pixel extraction algorithm for the center of facula image is presented. Then the calibration principle and method of probe system is analyzed in detail. Finally, the data processing principle of the presented method is discussed for gear measurement.

Abstract: This paper deals with an on-line mismachining error measurement for curve grinding based on digital image processing. Using CCD camera, the contour of the workpiece’s finished surface is captured and the image is preprocessed for denoising and edge detecting. The worktable is guided by the image of the finished workpiece to follow the path of the finished contour and then the real curve of the finished workpiece is measured by fitting a curve according to the moving path of the worktable. Finally, the machining error is obtained by comparing the measured curve with the theoretical curve of the workpiece. This method is applied to a CNC curve grinding machine MD9040. A measurement experiment is given. The experiment results show that the measurement method offers high detection precision and can be used in wide fields, especially for measuring the parts with complex curve.

Abstract: A kind of dynamic tracking system for conducting high accuracy measurement of transparent liquid concentration is designed by means of line matrix CCD receiving fringes in accordance with the relations between liquid concentration and refractive index as well as the relations among refractive index, interference light wavelength of optical fiber F-P interferometer and grade orders. The detecting system can recognize or detect 0.01% of concentration variations via measuring a group of alcohol.