Optica 3, 1422–1429 (2016)

A current bottleneck in imaging is the limited amount of information that can be digitally captured from an optical system. An assessment of recent literature on coherent microscopy and digital holographic imaging by Hongda Wang and collaborators has highlighted this point by revealing the mismatch between the pixel count of common image sensor chips (less than 4 megapixel) and the space–bandwidth product (SBP) of conventional microscope objectives (8–25 megapixel). To remedy the situation, the authors developed a computational imaging method that makes use of a stack of defocused images with a wide field of view (FOV) to improve the system's SBP and to create high-resolution images. The team use an illumination source at 532 nm, a standard bright-field microscope, a 1.45 megapixel charge-coupled device (CCD) sensor and a demagnification camera adapter (0.35×). A stack of out-of-focus intensity images is generated by vertically scanning the objective lens with respect to the sample plane and an iterative algorithm processes the information within them to recover high-resolution images. A stack of 3–5 out-of-focus images is sufficient to enhance the SBP of the system by a factor of ∼8.