Diffraction-limited depth-from-defocus imaging with a pixel-limited camera using pupil phase modulation and compressive sensing

The axial resolution of depth-from-defocus (DFD) imaging is generally restricted by the imaging device pixel pitch. Here, we propose a method of improving the axial resolution of DFD-based imaging with a pixel-limited camera to the minimum value determined by the diffraction limit, using pupil phase modulation and compressive sensing. Phase modulation at the pupil plane is employed to enhance the image defocus change and to reduce the correlation between varyingly defocused pixel-limited images. A compressive-sensing-based sparsity constraint is applied to object reconstruction. We experimentally verify the method with sparsely distributed objects and demonstrate diffraction-limited axial resolution with a pixel-limited camera.