26 November 2012 A novel optical beam deflection detection system based on aspheric lens for high-speed atomic force microscope
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Abstract
The optical lever detection method has been widely used to detect the cantilever deflection in atomic force microscope (AFM) due to its simple mechanism and high sensitivity. The deflection detection of very small cantilever is a key and difficult issue in the development of a high-speed AFM. In this paper, a specially designed optical beam deflection detection system based on an aspheric lens is presented. The aspheric lens is fixed on an adjustable metal tube above the cantilever to focus the laser beam with a small spot. Two laser line beamsplitter cubes are installed symmetrically and oppositely over the aspheric lens with separately mounting a diode laser and a position sensitive detector (PSD) on two translation stages at the same height. The collimated laser beam is reflected down by one cube and focused by the aspheric lens at an off-centered position. The focused beam is then incident upon the cantilever and reflected back onto the opposite off-centered position. Change in the reflection angle caused by the cantilever deflection results in a parallel shift of the outgoing laser beam after the aspheric lens. The laser beam is finally reflected onto the PSD by the other cube. Experimental results show that the laser beam can be focused with a spot of less than 16 μm in diameter. With above system, the deflection detection of the small cantilever can be realized, which meets the requirement for the use in a high-speed AFM.
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Jianyong Zhao, Guangyi Shang, Weitao Gong, Junen Yao, "A novel optical beam deflection detection system based on aspheric lens for high-speed atomic force microscope", Proc. SPIE 8557, Optical Design and Testing V, 855723 (26 November 2012); doi: 10.1117/12.2000814; https://doi.org/10.1117/12.2000814
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