Depth of Field Extension for Microscopic Structured Light Vision System Based on Image Fusion

Non-contact high-precision three-dimensional(3D) perception of tiny targets is widely required in precision machining, micro-assembly, quality inspection and other fields. This paper studies the depth-of-field (DOF) extension method of microscopic structured light system based on image fusion. Firstly, a microscopic structured light system hardware device with electrically tunable lens (ETL) is introduced, and the overall framework of using this system to capture sequential fringe images and three-dimensional imaging is given. In order to realize the DOF expansion, the key principles of commonly used spatial domain and frequency domain image fusion technologies are analyzed, and the fusion effect of microscopic structured light fringe images is tested respectively. Finally, according to the actual fusion performance, the Laplacian pyramid image with high fusion accuracy is selected for 3D imaging. Experimental results show that this method can better reconstruct two objects at different height positions in the scene compared with the single-focus case, and the measured DOF is greater than 10mm under the measurement field of view of 11mm (W) ×7mm (H).