On extending depth of field in fast photographic lenses

Modern smartphone cameras are equipped with multiple camera modules. These modules are typically five millimetres in length limiting the focal length of the lens. To preserve resolution the entrance pupil of these lenses are relatively large compared to the focal length. Large apertures are subject to large amplitudes of optical aberrations. These perturbations can only be compensated within a short total track length by the use of high order polynomial surfaces. Fast lenses char- acteristically have a shallow depth of field whereby a small region in object space is adequately in-focus. This can be an undesirable effect for spatially-dependent imaging applications such as biometric sensing and user authentication. A large depth of field can reduce the need for mechanical refocusing and computation- ally intensive focusing algorithms. Traditionally in photographic optics, reducing pupil diameter directly results in an increased depth of field. However, due to res- olution requirements the aperture cannot be stopped down. This thesis proposes novel approaches to extending depth of field for fast miniaturised camera lenses by employing optical design methods in whole or in major part. Utilising the lens parameters to increase the usable depth of field offers low-cost solutions that can possible replace voice coil motors and reduce the power consumption in camera modules.

Funder

Science Foundation Ireland
FotoNation Ltd

Publisher

NUI Galway

Rights

Attribution-NonCommercial-NoDerivs 3.0 Ireland

cbn

Collections

University of Galway Theses (PhD Theses)