Extended depth of focus imaging with birefringent plate

In this paper we present a simple approach to obtain extended depth of field for any optical imaging system just by adding a birefringent plate between the lens and the detector. The width of the plate is properly designed such that one polarization state contains in-focus near field information while the other polarization state contains in-focus far field details. Both images are superimposed one on top of the other and thus an all-optical spatially sharp imaging is obtained containing both fields. The width of the plate is also designed such that there is a longitudinal overlapping of the two regions (the near and the far) such that continuously well focused imaging is generated. The presented approach for extending the depth of focus is significantly simple compared to the use of birefringent and bi-focal lenses published recently. Preliminary numerical as well as experimental results verify the proposed approach.