Survey of Approaches to Extended Depth of Field Ke Xu Electrical Engineering, Stanford University

Motivation Focal Sweep Diffusion Optics For any optics system, large numerical aperture(NA) leads Focal sweep obtains distance invariant PSF by moving Diffusion coded photography uses diffusion optics to to higher resolution. However, large NA also results in the objects or sensors. achieve depth invariant PSF. The diffusion optics is shallow depth of field. For some optics system, like implemented using the “kinofrom” type diffuser, and have microscope, the shallow depth of field is not desired. Thus the wedge thickness to be t(u) = aλ ̄u. This diffuser was we try to figure out a way of maintaining large NA while places right at the aperture of the lens system. expanding the depth of field of the imaging system. 2. As we can see from the comparison graph below, As we learned in class, the main principle of extended Theoretical Integrated PSF diffusion has a flatter curve compare to wavefront depth of field (EDOF) is to make point spread 4 3 The obtained images 4 3 function(PSF) at pupil invariant to the distance. are stacked and then post-process to make the EDOF image.

A few other application Deep focus Shallow focus of focal sweep can be coding. found in utilizing Though the diffusion curve Wavefront Coding aberrations to de-blur image, such as spherical aberration is not as flat as the focal and chromatic aberration. sweep, the diffusion coded Wavefront coding adapts the idea of light field imaging by photography has advantage over the focal sweep for that putting some optics elements at the pupil plan and uses A simulation using CodeV is conducted to replicate the no physical element need to be moved. different parts of sensor to capture different depth of the result. The target image here used is the air force target object. After that, post processing technics are used on image, and the optics imaging system used is a the captured image to get EDOF image. microscope system. Reference:

1. Lattice focal length is a feature added 1. Levin, Anat, et al. "4D frequency analysis of computational cameras to the aperture that has arrays of for depth of field extension." ACM Transactions on Graphics (TOG). lenses with different focal lengths. Vol. 28. No. 3. ACM, 2009. 2. Ta n g , Huixuan, and Kiriakos N. Kutulakos. “Utilizing optical aberrations for extended-depth-of-field panoramas.” Computer Vision–ACCV 2012. Springer Berlin Heidelberg, 2012. 365-378. Cubic phase plate 3. Cossairt, Oliver, Changyin Zhou, and Shree Nayar. “Diffusion coded (left) is another form photography for extended depth of field.” ACM Transactions on of wavefront coding, Graphic s (TOG). Vol. 29. No. 4. ACM, 2010. it changes focus 4. Zhou, Changyin, Daniel Miau, and Shree K. Nayar. “Focal sweep camera for space-time refocusing.” (2012). through field uses. 5. Ta n g , Huixuan, and Kiriakos N. Kutulakos. "Utilizing optical aberrations for extended-depth-of-field panoramas." Computer Vision–ACCV 2012. Springer Berlin Heidelberg, 2012. 365-378. Original image Image after microscope Sensor +0.03 Sensor -0.05