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19 March 2012 Structure light with laser speckle for object contour reconstruction
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Proceedings Volume 8257, Optical Components and Materials IX; 825712 (2012)
Event: SPIE OPTO, 2012, San Francisco, California, United States
Invisible grid-pattern structure light has often been used for being shined on objects for contour reconstruction based on the distortion of grid pattern, for vehicle collision prevention etc. However, the structure light can be easily disturbed by surrounding nature light even if infra-red (IR) light source is used because natural light contains quite an amount of IR spectrum. In this paper, it is proposed that the structure light is provided from a highly coherent laser source, so that the structure light pattern reflected from the target object will contain not only the distorted irradiance distribution of grid pattern, but also laser speckle associated with it. The laser speckle pattern depends on the surface roughness of the target object, which provides extra information for extracting the distorted grid pattern from the background irradiance of surrounding natural light. The laser speckle pattern therefore helps to improve the immunity for surrounding light disturbance, and hence the robustness and reliability of contour reconstruction system. A binary surface relief phase-type diffractive optical element(DOE) has been proposed for generating desired pattern directly at far field when working together with laser light source. The design process is based on iterative Fourier transform algorithm(IFTA) in scalar diffraction theory.
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Ting-Xuan Hua, Cheng-Huan Chen, Augustine Tsai, and Wen-Kai Liu "Structure light with laser speckle for object contour reconstruction", Proc. SPIE 8257, Optical Components and Materials IX, 825712 (19 March 2012);

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