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Speckle projection provides rich textures for correlation, and has been widely used in three-dimensional(3D) reconstruction. However, for objects with high dynamic range(HDR) surface, conventional uniform speckle projection usually causes over-exposure and over-dark regions simultaneously in the captured images, leading to miss-match and errors in 3D result. It is difficult to perform defect elimination via adjustment of speckle intensity globally or the camera exposure time. To tackle this problem, this paper proposed a novel adaptive speckle projection method to distinguish the appropriate projection intensity of specific parts in the speckle pattern, thereby avoiding over-exposure, while the dark regions not being affected. First, uniform intensity patterns of multiple gray-levels are projected onto the surface of testing object, the appropriate projection intensity at each pixel position in the camera coordinate system is calculated, and the saturated area in the captured image is marked. Then, a set of orthogonal fringe patterns are projected onto the testing object to establish the coordinates mapping relationship between the camera and the projection system, and the adaptive speckle pattern under the projection coordinate system is generated. Finally, the generated adaptive speckle pattern is used to scan the testing object, and the spatial-temporal correlation algorithm is used for 3D shape retrieval. Experimental results demonstrate feasibility of 3D shape reconstruction of HDR surfaces with the proposed method, and obvious advantages compared with the traditional methods in terms of reconstruction completion and measurement accuracy. Keywords: adaptive speckle, high dynamic range, coordinates mapping, spatial-temporal correlation, 3D reconstruction
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