A large open aperture in an optical system can capture high-resolution images but yields a shallow depth of field. In order to keep the high-resolution and enlarge the DOF at the same time, back-and-forth movement of the lens should be driven by the rack and pinion motion of a motor.
However, continual forward and reverse rotation is a high-power-consumption task, because positive and negative current are used alternately to control the motor, which quickly triggers a safety stop to prevent overheating. Moreover, it is quite difficult to achieve high-speed responses in such conditions.
To overcome those issue, we investigated a low-cost, readily available method for retrofitting microscopy imaging systems to achieve 3D focus scanning in this study. Specifically, a procedure for fabricating variable focus spinners with dissimilar plates was introduced, and a sequence of 12 images was captured in different focal planes. The image scale and phase were corrected, and the in-focus pixels were abstracted by employing the Laplacian operator. Finally, an all-in-focus sharp image was generated, and a depth map was obtained.
The basic principle of the developed system is useful as a reference, and users could easily build their own spinners and modify and redesign the parameters for specific purposes. This design has a wide variety of potential applications, including in biomedical imaging, chip inspection, 3D sensing, and 3D printing, among other areas.
- Lihui Wang, Jianjiang Cui, Satoshi Tabata, Masatoshi Ishikawa, Low-cost, readily available 3D microscopy imaging system with variable focus spinner, Optics Express, Vol.26, Issue 23, pp. 30576-30587 (2018).[DOI:10.1364/OE.26.030576] *OSA