In conventional digital camera photography, object or objects in an image of a scene are in focus at one distance (or distance range) from the camera often results in other objects at other distances in the same scene being out of focus. This is especially the case when imaged objects are at different distances close to the camera, such as within 10 feet or less, where optimal focus may be limited to a single limited distance range. Such conventional digital cameras may have a focusing mechanism to change the limited distance range where objects in the image will be in focus. However, the focusing mechanism does not prevent objects outside this distance range being out of focus in the image. Thus, it would be desirable to provide imaging having an extended depth of field where the same object extending over a range of distances, or different objects at different distances are all in focus in an image of a common scene captured by a digital camera.
Prior research has developed optical systems for extending the depth of field either by the use of an apodization filter or by computer processing of purposefully blurred images, such as described in the following academic literature: J. Ojeda-Castaneda, L. R. Berriel-Valdos, and E. Montes, Opt. Lett. 8, 458 (1983); T.-C. Poon, and M. Motamedi, Appl. Opt. 26, 4612 (1987); J. Ojeda-Castaneda, and L. R. Berriel-Valdos, Appl. Opt. 29, 994 (1990); E. R. Dowski, and W. T. Cathey, Appl. Opt. 34, 1859 (1995); J. van der Gracht, E. R. Dowski, W. T. Cathy and J. P. Bowen, Proc. SPIE 2537, 279 (1995); H. B. Wach, W. T. Cathey, and E. R. Dowski, Jr., Appl. Opt. 37, 5359 (1998); S. C. Tucker, E. R. Dowski, and W. T. Cathey, Optics Express 4, 467 (1999). Related research is also cited on axilenses which are optical elements that concentrate light energy along an optical axis, such as described in: L. M. Soroko, in Progress in Optics, E. Wolf, ed. (Elsevier, N.Y., 1989), pp109-160, and references therein; J. Sochacki, S. Bara, Z. Jaroszewicz, and A. Kolodziejczyk, Opt. Lett. 17, 7 (1992); J. Sochacki, A. Kolodziejczyk, Z. Jaroszewicz, and S. Bara, Appl. Opt. 31, 5326 (1992).
It is a feature of the present invention to capture images through a circularly symmetric multifocal aspheric lens providing a blurred image which is then digitally processed to provide an image with an extended depth-of-field over which object or objects in the image are in focus. Prior approaches in extending depth of field described in the above-identified literature have neither utilized a circularly symmetric aspheric lens, nor have provided processing of blurred images obtained through such a lens to obtain images with improved focus over a large depth of field.