教師著作

Permanent URI for this collectionhttp://rportal.lib.ntnu.edu.tw/handle/20.500.12235/31268

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Author: search.filters.author.M.-C. LuSubject: search.filters.subject.distance measurement

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    Image-based distance and area measuring systems
    (IEEE Sensors Council, 2006-04-01) M.-C. Lu; W.-Y. Wang; C.-Y. Chu
    In this paper, a novel measuring system using a scancounter method via a CCD camera is proposed. The proposed measuring system is an easy-to-construct system to measure the distance between a CCD camera and an object, and to measure the projected area of the object. This measuring method needs not store huge amounts of image data nor use any pattern recognition approach. It quickly obtains the distance and the projected area using simple circuits and formulas. For distance measurement, two laser projectors are set on either side of a CCD camera and produce two parallel rays that project two bright spots on the object and, therefore, on the CCD. An external clock, which is generated by an extra oscillator, is used to measure the time interval between the two bright spots as the CCD scans the image. A circuit for counting the number of external clock pulses between the two bright spots is employed to calculate the interval between them in the video image. Due to the parallel setup of the distance measuring system, there is a linear relationship between the actual distance and the interval of the two bright spots. Therefore, the actual distance from the CCD camera to the object can be calculated from a simple formula. For area measurement, circuits count the number of external clock pulses of the horizontal scan lines covering the projected area of the object. Then, the projected area of the object is calculated from simple algebraic formulas. Finally, several experimental results demonstrate the effectiveness of the proposed system.
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    Three Dimensional Measurement of Distant Objects Based on Laser-Projected CCD Images
    (Institution of Engineering and Technology, 2009-05-01) C.-C. Hsu; M.-C. Lu; W.-Y. Wang; Y.-Y. Lu
    A novel measuring system based on a single CCD camera and two laser projectors to record images and perform three-dimensional measurement of a distant object is proposed here. Because of the alignment of the laser beams which form in parallel with the optical axis of the CCD camera, projected spots will appear on the same scan line in a CCD image. As a result processing of a single scan line rather than the whole image is only required to identify the projected spots in the CCD image. Complex computation of video signals of the whole image via either pattern recognition or image analysis methods is therefore circumvented. On the basic of an established relationship between the distance and pixel counts between the projected spots in the CCD image, the proposed system not only measures the distance from a distant object but also the length of two arbitrarily designated points on the object. To provide better accuracy, intrinsic parameters of the CCD camera are taken into consideration in the measurement. Furthermore, the effect of laser diffusion is also proved to be irrelevant to the measuring accuracy here. Experimental results have demonstrated that the proposed measuring method is capable of yielding accurate results of three-dimensional measurement for a distant object in a very responsive way.
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    Distance measurement based on pixel variation of CCD images
    (ISA, 2009-10-01) C.-C. Hsu; M.-C. Lu; W.-Y. Wang; Y.-Y. Lu
    This paper presents a distance measurement method based on pixel number variation ofimages for digital cameras by referencing to two arbitrarily designated points in image frames. Based on an established relationship between the displacement of the camera movement along the photographing direction and the difference in pixel counts between reference points in the images, distance from an object can be calculated via the proposed method. To integrate the measuring functions into digital cameras, circuit design implementing the proposed measuring system in selecting reference points, measuring distance, and displaying measurement results on CCD panel of the digital camera is proposed in this paper. In comparison to pattern recognition or image analysis methods, the proposed measuring approach is simple and straightforward for practical implementation into digital cameras. Experiment results have demonstrated that the proposed method is capable of yielding satisfactory measurement resultsin a very responsive way.