Abstract
The objective of this research is to investigate the feasibility of a zoom system using liquid lens as the active element. Different from the conventional zoom lens which uses moving lens element to perform zoom function, the liquid lens changes system power without movement, which potentially provide a compact solution for zoom system. This research proposes three different types of liquid zoom system which have totally different design concept and system feature, and has its own limit on zoom ratio.The first type is double liquid lens zoom system whose variator and compensator are replaced with liquid lens in traditional movable zoom system. The 1.5× zoom ratio had been achieved by double liquid lens zoom system without any movable component. But the large variation of the liquid surface curvature causes serious aberration and deteriorates image quality.The second one is liquid-compensated movable zoom system. A movable lens performs the zoom function, and a liquid lens is used for correcting the image plane. The principle of smallest change has been applied for reducing the variation of the liquid surface curvature during the zooming process. The 2.5× zoom ratio had been achieved but has still been limited by the variation of the liquid surface curvature, and could not be exceed to 3×.The third one is the combination of liquid lens and the concept of optically compensated zoom system. The zoom ratio could be improved to 4× because the zero-crossing of back focal shift during the zoom process, and the liquid lens is disposed to slightly correct the image plane in accordance.This outcome of the research is a liquid zoom system for two mega-pixel image sensor with 60 degree full viewing angle, 4× zoom ratio and a total track less than 30 mm. The high zoom ratio of 4× is equivalent to digital camera but only one moving group compared with the four or five moving groups of the traditional zoom system. In conclusion, the liquid zoom system provides a compact solution for portable devices such as mobile phone camera and PC camera.