Abstract
We demonstrated an electrically tunable optical image system with separable focus function and zoom function based on three tunable focusing composite liquid crystal (LC) lenses. One LC lens in charge of the focus function helps to maintain the formed image at the same position and the other two LC lenses in charge of zoom function assist to continuously form an image at image sensor with tunable magnification of image size. The detail optical mechanism is investigated and the concept is demonstrated experimentally. The magnifications of the images can be switched continuously for the target in a range between 10 cm and 100 cm. The optical zoom ratio of this system maintains a constant~6.5:1 independent of the object distance. This study provides not only a guideline to design the image system with an electrically optical zoom, but also provide an experimental process to show how to operate the tunable focusing lenses in such an image system.
Highlights
An imaging system with electrically tunable focus and zoom functions is important in cell phones, pico projectors, holographic projection systems, and endoscopes [1,2,3,4,5,6,7,8]
We demonstrated an electrically tunable imaging system with separable focus function and zoom function based on three composite liquid crystal (LC) lenses
Each composite LC lens consisted of three indium-tin oxide (ITO) glass substrates with a thickness of 0.7 mm, an isolating layer (NOA 81, Norland Optical Adhesive) with a thickness of 35 μm, mechanically buffered alignment layers (Polyvinylalcohol or PVA), a polymeric layer with thickness of 35 μm, and an LC layer (MLC-2144, Merck, Δn = 0.2493 for λ = 589.3 nm at 20°C) with a thickness of 50 μm
Summary
An imaging system with electrically tunable focus and zoom functions is important in cell phones, pico projectors, holographic projection systems, and endoscopes [1,2,3,4,5,6,7,8]. In 2011, we experimentally realized an electrically tunable optical zoom system using two LC lenses for the object distance in a range from 10 cm to infinity and the maximum optical zoom ratio was 5.6:1 [4]. One LC lens is in charge of the focus function of the object by means of electrically adjusting the focal length in order to maintain the formed image at the same position. Such a formed image at the same position continuously forms an image at the image sensor by the other two LC lenses which perform the function of zoom in and zoom out using electrically changing the focal lengths of the other two LC lenses. This study can provide researchers and engineers a guideline to design the portable devices with an electrically optical zoom
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