Fig. 1. Two-plane parameterization model of the 4D light field^[1]

Fig. 2. Two visualizations of a light field^[23]. (a) Light field is visualized as a uv array of xy images, in which each image in the array represents the rays leaving one point on the uv plane bound to all points on the xy plane; (b) light field is visualized as a xy array of uv images, in which each image represents the rays arriving at one point on the xy plane from all points on the uv plane

Fig. 3. Phase-space diagrams of light field^[1]. (a) A regular array of light rays from a set of points in the u plane to a set of points in the x plane; (b) a set of light rays arriving at the same position in the x plane; (c) a set of light rays approaching a location behind the x' plane; (d) a set of light rays diverging after converging at a location before the x″ plane

Fig. 4. Plane-direction parameterization model of the 4D light field, in which we have x≈θ at paraxial approximation

Fig. 5. 2D imaging and 3D imaging. (a) Imaging with conventional camera is 2D imaging, in which 3D information is lost during imaging and cannot be recovered from the image of single view; (b) 3D reconstruction can be achieved from images of two-view by using triangulation

Fig. 6. Light field acquisition with sequence imaging. (a) Spherical gantry, in which the inner arm typically holds a detector or camera, the outer arm holds a light source or video projector, and the object sits on the central platform^[9]; (b) 16×GoPro rotating array of action sports cameras, which can record the panoramic light field of the outward environment^[28]; (c) aperture scanning 4f system without mechanical movement, which employs a DMD in Fourier space to scan the aperture^[29-30]

Fig. 7. Light field capture with camera array. (a) A real-time light field recorder with 8×8 camera array^[31-32]; (b) a volumetric capture system for full-body light field capture, which comprises of 331 programmable light boards and 90 high-resolution cameras^[33]; (c) light field microscopy with 5×5 camera array^[34]; (d) PiCam, an ultra-thin high performance monolithic camera array, which consists of 4×4 micro-camera array with different color filters^[35]

Fig. 8. Catadioptric light field cameras, which capture light field by combining single camera and mirror array. (a) Mirror array with spherical mirrors of small curvature^[36]; (b) planar mirror array^[37]; (c) mirror array with spherical mirrors of large curvature^[38]

Fig. 9. Integral imaging, which captures light field by direct imaging using the microlens array. (a) Schematic diagram of integral imaging^[15]; (b) integral imaging lens consisting of lens-prism pairs^[39]

Fig. 10. Various lenslet images captured using plenoptic cameras with different MLA configurations^[40]

Fig. 11. Planar parallax for light field^[51]. A point P not on the reference plane has distinct images coordinates p₀, p_i in viewpoints C₀, C_i. The parallax between these two depends on the relative viewpoints displacement Δx_i and relative depth Δz_p/(Δz_p+Z₀)

Fig. 12. Angular coherence and refocusing^[58]. (a) Original light field image, in which the rays of different directions from the identical point are recorded in different macro pixels; (b) after refocusing, the rays from the identical point are recorded in one macro pixel. Different pixels within one macro pixel exhibit angular coherence, that is, the consistency of light intensity, depth and shadow

Fig. 13. Visualization of a cross-structure light-field and EPIs^[73]. Horizontal light-field EPIs are obtained by slicing horizontally through the image volume, while vertical light-field EPIs are obtained by slicing vertically through the image volume

Fig. 14. Light field 3D scanner framework for producing ultra high quality 3D reconstruction^[91]

Fig. 15. 3D reconstruction with phase-coded structured-light-field^[109]. (a) Basic system framework; (b) ray calibration

Table 1. Characteristics of different light field capture systems