All-in-focus image reconstruction under severe defocus

Abstract

Limited depth-of-focus is a problem in many fields of optics, e.g., microscopy and macro-photography. We propose a new physically based method with a space variant point spread function (PSF) to accomplish all-in-focus reconstruction (image fusion) from a multi-focus image sequence in order to extend the depth-of-field. The proposed method works well under strong defocus conditions for color image stacks of arbitrary length. Experimental results are provided to demonstrate that our method outperforms state-of-the-art image fusion algorithms for strong defocus on both synthetic as well as real data images.

Stereoscopy and refocusing from axial scanning in 3D imaging

“…thick specimens in microscopy), a pre-processing procedure, known as registration, need to be done to correct the differences [1]. In [2], a simple optical system which incorporates an electrically focus-tunable lens (ETL) and does not require registration was considered. This calibrated optical system behaves as a thin lens with an effective focal length that can be varied by changing the electrical current through the ETL.…”

“…3, a set of 2 images acquired by the optical system proposed in [2] is shown. Figure 4(a-b) shows the right and left eye views for bx=-1.2mm and bx =+1.2mm respectively.…”

Speeded-Up Focus Control of Electrically Tunable Lens by Sparse Optimization

“…Polymer-based ETLs achieve a faster focal change than other ETL types, while maintaining a relatively large aperture size. Consequently, they have been exploited in a wide range of optical systems, from micro-scale systems such as microscopes (e.g., two-photon microscopy 3–6 , light-sheet microscopy 7,8 , selective-plane illumination microscopy 9,10 , confocal microscopy 11 , photoacoustic mictoscopy 12 , and phase microscopy 13 ), optical coherence tomography 14 , optical diffraction tomography 15 , and laparoscopes 16 , to larger-scale systems such as still cameras 17 , video cameras 18 , depth cameras 19 , projectors 20 , video see-through head-mounted displays (HMDs) 21–23 , and optical see-through HMDs 24,25 .…”

“…In most of these systems, focal sweep of the ETL is applied in focal stacking, multi-focal, and extended depth-of-field (DOF) imaging and display 3–7,9,11–13,15,17,18,20,22–25 . The sweep patterns vary from a unit step function to various periodic ones (e.g., sinusoidal, rectangular, triangle, and staircase waves).…”

Large aperture focus stacking with max-gradient flow by anchored rolling filtering

“…This phenomenon will yield ghost edges in the result. The frequency-domain method proposed by Alonso and co-workers [13,14] could partly overcome this problem. In their work, each frequency component was reconstructed by solving a linear equation based on a plane-wise approximation of the 3D scene.…”