High-speed all-in-focus 3D imaging method based on liquid lens focus scanning

Abstract

A large open aperture in an optical system can capture high-resolution images but yields a shallow depth of field. To overcome this issue, we propose a method for retrofitting microscopy imaging systems by using a variable-focus liquid lens to achieve 3D focus scanning. Specifically, the focal length of the imaging system was changed by controlling the liquid lens, and a sequence of images was captured at different focal planes in milliseconds. The image scale and phase were corrected. Then the in-focus pixels were abstracted by employing the Laplacian operator. These pixels were marked in the index table. According to the index table, the focused parts of multiple images were merged, and an all-in-focus image was generated. At the same time, a depth map was constructed based on the image number in the index table and the extracted depth information. Additionally, we have optimized the image processing flow; the processing speed was improved to around 6.5 fps.