Method and apparatus for reduction of trapezoidal distortion and improvement of image sharpness in an optical image capturing system

摘要

An apparatus and method for acquiring an image of a patterned object such as a fingerprint including a light refracting device, a focusing lens, and a light source. The light refracting device can, for example, be a prism and includes an imaging surface, a light receiving surface and a viewing surface. Incident light from the light source is projected through the light receiving surface and reflected off a surface other than the imaging surface. This reflected light is then projected onto the imaging surface to create an image of the patterned object from substantially all scattered light through the viewing surface. The lens is placed adjacent to the viewing surface to focus the light on an image sensor. The apparatus is configured to reduce or substantially eliminate trapezoidal distortion and improve overall image sharpness in an image of an object created by the apparatus.