Light-field Systems Research Articles

Robust single-shot 3D fluorescence imaging in scattering media with a simulator-trained neural network.

Imaging through scattering is a pervasive and difficult problem in many biological applications. The high background and the exponentially attenuated target signals due to scattering fundamentally limits the imaging depth of fluorescence microscopy. Light-field systems are favorable for high-speed volumetric imaging, but the 2D-to-3D reconstruction is fundamentally ill-posed, and scattering exacerbates the condition of the inverse problem. Here, we develop a scattering simulator that models low-contrast target signals buried in heterogeneous strong background. We then train a deep neural network solely on synthetic data to descatter and reconstruct a 3D volume from a single-shot light-field measurement with low signal-to-background ratio (SBR). We apply this network to our previously developed computational miniature mesoscope and demonstrate the robustness of our deep learning algorithm on scattering phantoms with different scattering conditions. The network can robustly reconstruct emitters in 3D with a 2D measurement of SBR as low as 1.05 and as deep as a scattering length. We analyze fundamental tradeoffs based on network design factors and out-of-distribution data that affect the deep learning model's generalizability to real experimental data. Broadly, we believe that our simulator-based deep learning approach can be applied to a wide range of imaging through scattering techniques where experimental paired training data is lacking.

Three-dimensional gradient index microlens arrays for light-field and holographic imaging and displays.

The geometric, intensity, and chromatic distortions that are a result of the limitations of the material and processes used to fabricate micro-optical lens arrays (MLAs) degrade the performance of light-field systems. To address these limitations, inkjet print additive manufacturing is used to fabricate planar gradient index (GRIN) lenslet arrays, in which volumetric refractive index profiles are used to embed optical functions that would otherwise require multiple homogeneous index MLA surfaces. By tailoring the optical ink feedstock refractive index spectra, independent control over dispersion is achieved, and achromatic performance is made possible. Digital manufacturing is shown to be beneficial for optimizing individual micro-optical channels in arrays wherein the shape, size, aspect ratio, focal length, and optical axis orientation of the lenslets vary as a function of the position within the optical field. Print fabrication also allows opaque inter-lens baffling and aperture stops that reduce inter-channel cross talk, improve resolution, and enhance contrast. These benefits are demonstrated in a light-field display testbed.

F-number and focal length of light field systems: a comparative study of field of view, light efficiency, signal to noise ratio, and depth of field

The paper discusses the light efficiency and signal-to-noise ratio (SNR) of light field imaging systems in comparison to classical 2D imaging, which necessitates the definition of focal length and f-number. A comparison framework between 2D imaging and arbitrary light field imaging systems is developed and exemplified for the kaleidoscopic and the afocal light field imaging architectures. Since the f-number, in addition to the light efficiency of the system, is conceptually linked to the depth-of-field, an appropriate depth-of-field interpretation for light field systems is discussed as well.

Beyond Perceptual Thresholds and Personal Preference: Towards Novel Research Questions and Methodologies of Quality of Experience Studies on Light Field Visualization

With the upcoming emergence of the IEEE P3333.1.4 standard, the first ever standardization document on the subjective quality assessment of light field visualization, we are approaching a major milestone of light field Quality of Experience (QoE). The research efforts leading up to this point have answered the fundamental questions regarding perceptual thresholds and personal preference, and best practices regarding research methodologies have been formed. However, in order to introduce successful and efficient light field systems and services, research questions beyond perceptual thresholds and personal preference must be addressed, along with the associated methodologies. In this paper, we propose a comprehensive set of novel research questions and methodologies regarding light field QoE. Our work also provides a detailed discussion of related factors, particularly those that extend to test participants and thus may affect the results of subjective studies.

High-resolution 3D light-field imaging.

.Significance: High-speed 3D imaging methods have been playing crucial roles in many biological discoveries.Aim: We present a hybrid light-field imaging system and image processing algorithm that can visualize high-speed biological events.Approach: The hybrid light-field imaging system uses the selective plane optical illumination, which simultaneously records a high-resolution 2D image and a low-resolution 4D light-field image. The high-resolution 4D light-field image is obtained by applying the hybrid algorithm derived from the deconvolution and phase retrieval methods.Results: High-resolution 3D imaging at a speed of 100-s volumes per second over an imaging field of in the , , and axis, respectively, is achieved with a 2.5 times enhancement in lateral resolution over the entire imaging field compared with standard light-field systems. In comparison to the deconvolution algorithm, the hybrid algorithm addresses the artifact issue at the focal plane and reduces the computation time by a factor of 4.Conclusions: The new hybrid light-field imaging method realizes high-resolution and ultrafast 3D imaging with a compact setup and simple algorithm, which may help discover important applications in biophotonics to visualize high-speed biological events.

Fundamentals of 3D imaging and displays: a tutorial on integral imaging, light-field, and plenoptic systems

There has been great interest in researching and implementing effective technologies for the capture, processing, and display of 3D images. This broad interest is evidenced by widespread international research and activities on 3D technologies. There is a large number of journal and conference papers on 3D systems, as well as research and development efforts in government, industry, and academia on this topic for broad applications including entertainment, manufacturing, security and defense, and biomedical applications. Among these technologies, integral imaging is a promising approach for its ability to work with polychromatic scenes and under incoherent or ambient light for scenarios from macroscales to microscales. Integral imaging systems and their variations, also known as plenoptics or light-field systems, are applicable in many fields, and they have been reported in many applications, such as entertainment (TV, video, movies), industrial inspection, security and defense, and biomedical imaging and displays. This tutorial is addressed to the students and researchers in different disciplines who are interested to learn about integral imaging and light-field systems and who may or may not have a strong background in optics. Our aim is to provide the readers with a tutorial that teaches fundamental principles as well as more advanced concepts to understand, analyze, and implement integral imaging and light-field-type capture and display systems. The tutorial is organized to begin with reviewing the fundamentals of imaging, and then it progresses to more advanced topics in 3D imaging and displays. More specifically, this tutorial begins by covering the fundamentals of geometrical optics and wave optics tools for understanding and analyzing optical imaging systems. Then, we proceed to use these tools to describe integral imaging, light-field, or plenoptics systems, the methods for implementing the 3D capture procedures and monitors, their properties, resolution, field of view, performance, and metrics to assess them. We have illustrated with simple laboratory setups and experiments the principles of integral imaging capture and display systems. Also, we have discussed 3D biomedical applications, such as integral microscopy.

Coherent control of whispering-gallery-mode optomechanical microresonators and perfect transparency

Cavity-optomechanics has emerged as a new interdisciplinary research field,which studies the interaction between light field and mechanical systems of micro-and nanoscale.It is a promising avenue to solid-state quantum optics and has potential applications in high sensitivity measurement of weak force,tiny displacement and mass,and quantum information science.As a solid-state system of quantum optics,it has many interesting coherent phenomena,such as optomechanically induced transparency (OMIT),which is the optomechanical analog of the well-known phenomenon of electromagnetically induced transparency (EIT).However,due to diversity in structure,OMIT systems must have many new phenomena which do not exist in ordinary EIT systems.On the other hand,whispering-gallery-mode (WGM) microresonators have been investigated extensively.WGM microresonators have a wide range of applications due to their high quality factors and microscale mode volumes.WGM microresonators can also be used for OMIT systems,which have been investigated extensively.In this paper,we study the coherent control of an double-cavity optomechanical system which is composed of two WGM microresonators.We assume that the two WGM microcavties are driven by two strong control fields and two weak probe fields,and,one of the two cavities can create a macroscopic mechanical breathing mode under the action of a radiation pressure force.We also assume that the two WGM microcavties are directly coupled by an evanescent field.We theoretically study the quantum coherent control of electromagnetically induced transparency in this system,and find that in contrast with ordinary EIT systems,there are many new properties in this OMIT system, for example if two control fields with appropriate amplitudes and detunings are used to drive the system,the probe field, which is input to one of the two cavities,will be completely output from the other cavity,i.e.,the perfect transparency of the quantum coherence phenomenon can occur in this system.We also find that the electromagnetically induced transparency can be realized and controlled in this optomechanical system by adjusting the relative intensity and the relative phase between the two input probe fields,and the width and depth of the EIT window are sensitive to the relative intensity of the two control fields,which may be used for switching between fast and slow light.These results indicate important progress toward signal amplification,light storage,fast light,and slow light in quantum information processes.Considering the fact that WGM microresonators are the frontier research subjects ranging from biosensing, nonlinear optics,and laser physics,to fundamental physics such as cavity quantum electrodynamics,we believe that the results in this paper have a wide range of applications.

24.1: Invited Paper: Design Principles for Light Field Image Capture and Display

Light field capture and display technologies have been rapidly emerging in the past decade. The high dimensional design space of light field systems, however, imposes new challenges for end to end system design and evaluation. We discuss design principles for task specific light field camera systems and outline how such principles can be applied to or need to be modified for the design of personal light field displays.

The Propagation of Periodic Waves in a Two-level System

Abstract In this article the possibility for the propagation of periodic waves in a two-level system is discussed. It turns out, that in the absence of processes leading to loss and gain of energy, respectively, periodic waves only are possible. Their frequencies are always greater than the transition frequency of the two-level system. The frequency difference and the deviation of the wave profile from a sinusoidal form increases with the strength of interaction of light field and two-level systems. After the introduction of loss and source terms it turns out that only isolated periodic waves exist. The asymptotically stable ones among them act as asymptotic solutions to all other wave solutions. The frequencies and wave forms are affected in a similar way as without loss and source terms.