Imaging with Depth Extension - Where are the Limits in Fixed-Focus Cameras?

摘要

The integration of novel optics designs, miniature CMOS sensors, and powerful digital processing into a single imaging module package is driving progress in handset camera systems in terms of performance, size (thinness) andcost. The miniature cameras incorporating high resolution sensors and fixed-focus Extended Depth of Field (EDOF)optics allow close-range reading of printed material (barcode patterns, business cards), while providing high qualityimaging in more traditional applications. These cameras incorporate modified optics and digital processing torecover the soft-focus images and restore sharpness over a wide range of object distances. The effects a variety ofparameters of the imaging module on the EDOF range were analyzed for a family of high resolution CMOSmodules. The parameters include various optical properties of the imaging lens, and the characteristics of the sensor.The extension factors for the EDOF imaging module were defined in terms of an improved absolute resolution inobject space while maintaining focus at infinity. This definition was applied for the purpose of identifying theminimally resolvable object details in mobile cameras with bar-code reading feature.