Light ray field capture using focal plane sweeping and its optical reconstruction using 3D displays

Single-shot three-dimensional imaging with a scattering layer [Invited]

In this paper, we propose a single-shot three-dimensional imaging technique. This is achieved by simply placing a normal thin scattering layer in front of a two-dimensional image sensor, making it a light-field-like camera. The working principle of the proposed technique is based on the statistical independence and spatial ergodicity of the speckle produced by the scattering layer. Thus, the local point responses of the scattering layer should be measured in advance and are used for image reconstruction. We demonstrate the proposed method with proof-of-concept experiments and analyze the factors that affect its performance.

Light field reconstruction with randomly shot photographs

Light field imaging is a promising technique for recording and displaying three-dimensional (3D) scenes. Light field reconstruction using a conventional camera, instead of a lens-array-based plenoptic camera, is expected to have a higher resolution. However, in existing conventional-camera-based methods, the camera placement is restricted. In this paper, we propose a new flexible light field reconstruction method involving shooting using a conventional camera from random 3D positions and angles. The proposed method has the advantage of flexibility because it uses a conventional camera, and the shooting position and angle can be selected randomly. Such flexibility is expected to give it a wide range of applications.

Non-hogel-based computer generated hologram from light field using complex field recovery technique from Wigner distribution function

We propose a novel method that synthesizes computer-generated holograms from light field data. Light field, or ray space, is the spatio-angular distribution of light rays coming from three-dimensional scene, and it can also be represented using a large number of views from different observation directions. The proposed method synthesizes a hologram by applying the complex field recovery technique from its Wigner distribution function to the light field data. Unlike conventional approaches, the proposed method synthesizes holograms without hogel configuration, generating a converging parabolic wave for each object point with continuous wavefront. The proposed method does not trade the spatial resolution with angular resolution like conventional hogel-based approaches. Moreover, the proposed method works not only for random phase light field like conventional approaches, but also for arbitrary phase distribution with corresponding carrier waves. Therefore, the proposed method is useful in synthesizing holographic contents for a wide range of applications. The proposed method is verified by simulations and optical experiments, showing successful reconstruction of three-dimensional objects.

3D Imaging Based on Depth Measurement Technologies

Three-dimensional (3D) imaging has attracted more and more interest because of its widespread applications, especially in information and life science. These techniques can be broadly divided into two types: ray-based and wavefront-based 3D imaging. Issues such as imaging quality and system complexity of these techniques limit the applications significantly, and therefore many investigations have focused on 3D imaging from depth measurements. This paper presents an overview of 3D imaging from depth measurements, and provides a summary of the connection between the ray-based and wavefront-based 3D imaging techniques.

Fast and high-resolution light field acquisition using defocus modulation

In the conventional microlens-array-based light field imaging system, there is a trade-off between the angular and spatial resolutions. Light field reconstruction from images captured by focal plane sweeping, such as light field moment imaging (LFMI) and light field reconstruction with back projection (LFBP), can achieve high transverse resolution comparable to the modern camera sensor. However, the acquisition of a series of focal plane sweeping images along the optical axis is time consuming and requires fine alignment. Furthermore, different focal-plane-based light field reconstruction techniques require images with different characteristics. To solve these problems, we present an efficient approach for fast light field acquisition with precise focal plane sweeping capture by defocus modulation, rather than mechanical movement. Also, we verify the validity and the improvement of our system. With the controllable point spread function, we can capture images for light field reconstruction with both LFMI and LFBP. Otherwise, we quantitatively compare the two methods using images captured with the proposed systems.

Analysis of the noise in backprojection light field acquisition and its optimization

Light field reconstruction from images captured by focal plane sweeping can achieve high lateral resolution comparable to the modern camera sensor. This is impossible for the conventional micro-lenslet-based light field capture systems. However, the severe defocus noise and the low depth resolution limit its applications. In this paper, we analyze the defocus noise in the focal-plane-sweeping-based light field reconstruction technique, and propose a method to reduce the defocus noise. Both numerical and experimental results verify the proposed method.

F-number matching method in light field microscopy using an elastic micro lens array

In light field microscopy (LFM), the F-number of the micro lens array (MLA) should be matched with the image-side F-number of the objective lens to utilize full resolution of an image sensor. We propose a new F-number matching method that can be applied to multiple objective lenses by using an elastic MLA. We fabricate an elastic MLA with polydimethylsiloxane (PDMS) using a micro contact printing method and address the strain for the F-number variation. The strain response is analyzed, and the LFM system with the elastic MLA is demonstrated. Our proposed system can increase the F-number up to 27.3% and can be applied to multiple objective lenses.

High-resolution Fourier hologram synthesis from photographic images through computing the light field

We present a technique for synthesizing the Fourier hologram of a three-dimensional scene from its light field. The light field captures the volumetric information of an object, and an important advantage is that it does not require coherent illumination, as in conventional holography. In this work, we show how to obtain a high-resolution digital hologram with the light field obtained from a series of photographic images captured along the optical axis. The method is verified both by simulations and experimentally captured light field.

Real-time depth controllable integral imaging pickup and reconstruction method with a light field camera

In this paper, we develop a real-time depth controllable integral imaging system. With a high-frame-rate camera and a focus controllable lens, light fields from various depth ranges can be captured. According to the image plane of the light field camera, the objects in virtual and real space are recorded simultaneously. The captured light field information is converted to the elemental image in real time without pseudoscopic problems. In addition, we derive characteristics and limitations of the light field camera as a 3D broadcasting capturing device with precise geometry optics. With further analysis, the implemented system provides more accurate light fields than existing devices without depth distortion. We adapt an f-number matching method at the capture and display stage to record a more exact light field and solve depth distortion, respectively. The algorithm allows the users to adjust the pixel mapping structure of the reconstructed 3D image in real time. The proposed method presents a possibility of a handheld real-time 3D broadcasting system in a cheaper and more applicable way as compared to the previous methods.