The capture and display of images of 3-D scenes under incoherent and polychromatic illumination is currently a hot topic of research, due to its broad applications in bioimaging, industrial procedures, military and surveillance, and even in the entertainment industry. In this context, Integral Imaging (InI) is a very competitive technology due to its capacity for recording with a single exposure the spatial-angular information of light-rays emitted by the 3-D scene. From this information, it is possible to calculate and display a collection of horizontal and vertical perspectives with high depth of field. It is also possible to calculate the irradiance of the original scene at different depths, even when these planes are partially occluded or even immersed in a scattering medium. In this paper, we describe the fundaments of InI and the main contributions to its development. We also focus our attention on the recent advances of the InI technique. Specifically, the application of InI concept to microscopy is analyzed and the achievements in resolution and depth of field are explained. In a different context, we also present the recent advances in the capture of large scenes. The progresses in the algorithms for the calculation of displayable 3-D images and in the implementation of setups for the 3-D displays are reviewed.

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Recent Advances in the Capture and Display of Macroscopic and Microscopic 3-D Scenes by Integral Imaging

We propose a cross-talk-free integral imaging 3D display based on a pyramid pinhole array. The pyramid pinhole array is used to provide a point light source array. Since the generated point light source array is behind a transmission-type display panel that displays an elemental image array, the pseudoscopic problem can be resolved. By setting the appropriate parameters for the pyramid pinhole array, the cross talk can be eliminated. We experimentally verify the reconstruction of the orthoscopic and cross-talk-free 3D images using the proposed 3D display.

Cross-talk-free integral imaging three-dimensional display based on a pyramid pinhole array

We propose a new multi-projection integral imaging scheme using a convex mirror array. In the proposed scheme, to overcome the resolution limitation of the conventional method due to observing the single aperture imaging point (AIP) from each convex mirror, we introduce the multi-projection to obtain multiple AIPs per convex mirror so that the viewer observes the resolution-improved 3D reconstructed images. We validate the theoretical analysis of the proposed scheme and confirm its feasibility through the optical experiments. To our best knowledge, this is the first report to generate multiple AIPs per convex mirror in a projection integral imaging system.

Multi-projection integral imaging by use of a convex mirror array

Unique concave microlens arrays (MLAs) made of calcite single crystals with tunable crystal orientations can be readily fabricated by template-assisted epitaxial growth in solution without additives under ambient conditions. While the non-birefringent calcite (001) MLA showed excellent imaging performance like brittlestar's microlens arrays, the birefringent calcite (104) MLA exhibited remarkable polarization-dependent optical properties.

Brittlestar‐Inspired Microlens Arrays Made of Calcite Single Crystals

Two-dimensional (2D)/three-dimensional (3D) convertible or mixed display is one of the most important factors for the fast penetration of 3D display into the display market. In this paper, we propose a 2D/3D mixed frontal projection system that mainly contains a liquid crystal micro-lens array (LCMLA) and a quarter-wave retarding film with pinholes (QWRF-P). The LCMLA exhibits the focusing effect or no optical effect depending on the polarization direction of the incident lights. The forward incident lights pass through the LCMLA without any bending. After passing through the QWRF-P twice, half of the backward lights change the polarization direction with 90°, and the other half remains. Using our designed system, different display modes, including 2D display, 3D display, and 2D/3D mixed display, can be realized. The unique feature of the proposed 2D/3D mixed frontal projection system is that it can switch the display modes by simply changing the image sources without the need of any active optical devices. Moreover, the proposed system is compact, simple and space-efficient, which is suitable for the application in glassless 3D cinema and home 3D theatre.

2D/3D mixed frontal projection system based on integral imaging.

We propose a method for enhancing depth-of-field, in which the spot size on a marginal depth plane is reduced. This method is implemented in a projection-type integral imaging system using a negative lens array without a diffuser. Numerical simulation results show that the spot size is merely 5.7% of that in a conventional system. Thus, the depth-of-field in the proposed system is enhanced by 17.5 times over that in a conventional system. Optical experiments confirm good agreement between the results and numerical predictions.

Enhancement of depth-of-field in a direct projection-type integral imaging system by a negative lens array

We report an integral imaging method with continuous imaging space. This method simultaneously reconstructs real and virtual images in the virtual mode, with a minimum gap that separates the entire imaging space into real and virtual space. Experimental results show that the gap is reduced to 45% of that in a conventional integral imaging system with the same parameters.

https://iopscience.iop.org/article/10.1088/1674-1056/22/5/054202/pdf

Lei Zhang

Papers

Enhancement of depth-of-field in a direct projection-type integral imaging system by a negative lens array

Continuous imaging space in three-dimensional integral imaging