scholarly journals Effective Light Beam Modulation by Chirp IDT on a Suspended LiNbO3 Membrane for 3D Holographic Displays

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1218
Author(s):  
Yongbeom Lee ◽  
Keekeun Lee
Keyword(s):  
Light Beam ◽  
Focal Length ◽  
Incident Light ◽  
Coupling Efficiency ◽  
Input Power ◽  
Design Parameters ◽  
Holographic Display ◽  
Beam Modulation ◽  
Comsol Simulation ◽  
Holographic Displays

An acousto-optic (AO) holographic display unit based on a suspended waveguide membrane was developed. The AO unit consists of a wide bandwidth chirp interdigital transducer (IDT) on a 20 µm thick suspended crystalline 128° YX LiNbO3 membrane, a light blocker with a 20 µm hole near the entrance, and an active lens near the exit. The 20 µm thickness of the floating membrane significantly enhanced surface acoustic wave (SAW) confinement. The light blocker was installed in front of the AO unit to enhance the coupling efficiency of the incident light to the waveguide membrane and to remove perturbations to the photodetector during measurement at the exit region. The active lens was vertically attached to the waveguide sidewall to collect the diffracted beam without loss and to modulate the focal length in free space through the applied voltage. As SAWs were radiated from the IDT, a Bragg grating with periodic refractive indexes was formed along the waveguide membrane. The grating diffracted incident light. The deflection angle and phase, and the intensity of the light beam were controlled by the SAW frequency and input power, respectively. The maximum diffraction efficiency achieved was approximately 90% for a 400 MHz SAW. COMSOL simulation and coupling of mode modeling were performed to optimize design parameters and predict device performance.

DUAL LIGHT BEAM MODULATION OF PHOTOCARRIER LIFETIME IN INTRINSIC a-Si:H

1981 ◽  
Vol 42 (C4) ◽  
pp. C4-597-C4-600 ◽  
Author(s):  
P. D. Persans ◽  
H. Fritzsche
Keyword(s):  
Light Beam ◽  
Beam Modulation

scholarly journals Computer-Generated Hologram Based on Reference Light Multiplexing for Holographic Display

2021 ◽  
Vol 11 (16) ◽  
pp. 7199
Author(s):  
Dapu Pi ◽  
Juan Liu
Keyword(s):  
Image Quality ◽  
Numerical Simulations ◽  
Light Wave ◽  
Information Capacity ◽  
Improve Image Quality ◽  
Multiple Images ◽  
Holographic Display ◽  
Light Waves ◽  
Computer Generated Holograms ◽  
Holographic Displays

In this article, we propose a reference light wave multiplexing scheme to increase the information capacity of computer-generated holograms. The holograms were generated by different reference light waves and superimposed together as a multiplexed hologram. A modified Gerchberg–Saxton algorithm was used to improve image quality, and different images could be reconstructed when the multiplexed hologram was illuminated by corresponding reference light waves. We performed both numerical simulations and optical experiments to demonstrate the feasibility of the proposed scheme. Numerical simulations showed that the proposed method could reconstruct multiple images successfully by a single multiplexed hologram and optical experiments are consistently good with numerical simulations. It is expected that the proposed method has great potential to be widely applied in holographic displays in the future.

scholarly journals Electrically-Tunable Blue Phase Liquid Crystal Microlens Array Based on a Photoconductive Film

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 65 ◽  
Author(s):  
Bing-Yau Huang ◽  
Shuan-Yu Huang ◽  
Chia-Hsien Chuang ◽  
Chie-Tong Kuo
Keyword(s):  
Refractive Index ◽  
Liquid Crystal ◽  
Electric Field ◽  
Uv Light ◽  
Focal Length ◽  
Incident Light ◽  
Microlens Array ◽  
Gradient Distribution ◽  
Phase Liquid ◽  
Blue Phase

This paper proposes an effective approach to fabricate a blue phase liquid crystal (BPLC) microlens array based on a photoconductive film. Owing to the characteristics of photo-induced conducting polymer polyvinylcarbazole (PVK), in which conductivity depends on the irradiation of UV light, a progressive mask resulting in the variation of conductivity is adopted to produce the gradient distribution of the electric field. The reorientations of liquid crystals according to the gradient distribution of the electric field induce the variation of the refractive index. Thus, the incident light experiences the gradient distribution of the refractive index and results in the focusing phenomenon. The study investigates the dependence of lens performance on UV exposure time, the focal length of the lens, and focusing intensities with various incident polarizations. The BPLC microlens array exhibits advantages such as electrically tunability, polarization independence, and fast response time.

scholarly journals Study of Non-Periodic Pinhole Array Filter for Decreasing High-Order Noise for Compact Holographic Display

2020 ◽  
Vol 10 (23) ◽  
pp. 8671
Author(s):  
Yoo Kwang Kim ◽  
Won Jong Ryu ◽  
Jin Su Lee
Keyword(s):  
Spatial Light Modulator ◽  
Optical Path Length ◽  
Wearable Devices ◽  
Optical Path ◽  
High Order ◽  
Light Modulator ◽  
Noise Sources ◽  
Holographic Display ◽  
Custom Made ◽  
Holographic Displays

The non-periodic pinhole array filtering of a spatial light modulator (SLM) is proposed for filtering the high-order noise and DC noise of a holographic display. Conventionally, DC and high-order noise sources are filtered by a 4f filtering system. Because the 4f filtering system requires a long optical path length, noise filtering is a stumbling block when attempting to realize a compact holographic display. By contrast, the proposed method simply uses a thin filter fabricated by photolithography. In order to verify this concept, we confirmed the feasibility of the filter with a numerical simulation and with a custom-made non-periodic pinhole array filter used in a practical experiment. The proposed method was shown to have the potential to be used in applications ranging from compact wearable devices to table-top holographic displays.

Excitation of a ridge waveguide by a normally incident light beam

1995 ◽  
Vol 25 (6) ◽  
pp. 582-586 ◽  
Author(s):  
O Parriaux ◽  
V A Sychugov ◽  
A V Tishchenko
Keyword(s):  
Light Beam ◽  
Incident Light ◽  
Ridge Waveguide ◽  
Incident Light Beam

A New Design of a (3D) Fresnel Collector With Fixed Mirrors and Tracking Absorber

2000 ◽  
Vol 122 (2) ◽  
pp. 63-68 ◽  
Author(s):  
A. B. Larbi
Keyword(s):  
Concentration Ratio ◽  
Focal Length ◽  
Computer Code ◽  
Design Parameters ◽  
Medium Temperature ◽  
Maintenance Costs ◽  
Energy Delivery ◽  
Half Angle ◽  
Optical Behavior ◽  
Fixed Mirrors

In this paper we developed model of a (3D) Fresnel collector with fixed mirrors and tracking absorber which approximates the optical behavior of a fixed spherical collector (hemispherical bowl). The aim of the study is to investigate the possibility of using this type of installation for applications in medium temperature processes (200—300°C). Via a computer simulation which includes ray-tracing, we evaluate the sensitivity of the geometric concentration ratio to: concentrator design parameters and the option of using curved versus flat elementary mirrors. The developed computer code permits the optimization of the concentrator reflecting area, the focal length (or rim half-angle), and the dimensions and number of reflecting elementary mirrors. The (3D) Fresnel collectors can be a practical alternative to spherical collectors (hemispherical bowl). Capital and maintenance costs can be significantly lower than for spherical collectors, but with reduced energy delivery. [S0199-6231(00)00302-6]

scholarly journals How Do Operational and Design Parameters Effect Biomass Productivity in a Flat-Panel Photo-Bioreactor? A Computational Analysis

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1387
Author(s):  
Varun Loomba ◽  
Eric von Lieres ◽  
Gregor Huber
Keyword(s):  
Light Intensity ◽  
Light Exposure ◽  
Incident Light ◽  
Algal Growth ◽  
Biomass Productivity ◽  
Design Parameters ◽  
Operational Parameters ◽  
Incident Light Intensity ◽  
Flat Panel ◽  
Air Inlet

Optimal production of microalgae in photo-bioreactors (PBRs) largely depends on the amount of light intensity received by individual algal cells, which is affected by several operational and design factors. A key question is: which process parameters have the highest potential for the optimization of biomass productivity? This can be analyzed by simulating the complex interplay of PBR design, hydrodynamics, dynamic light exposure, and growth of algal cells. A workflow was established comprising the simulation of hydrodynamics in a flat-panel PBR using computational fluid dynamics, calculation of light irradiation inside the PBR, tracing the light exposure of individual cells over time, and calculation the algal growth and biomass productivity based on this light exposure. Different PBR designs leading to different flow profiles were compared, and operational parameters such as air inlet flowrate, microalgal concentration, and incident light intensity were varied to investigate their effect on PBR productivity. The design of internal structures and lighting had a significant effect on biomass productivity, whereas air inlet flowrate had a minimal effect. Microalgal concentration and incident light intensity controlled the amount of light intensity inside the PBR, thereby significantly affecting the overall productivity. For detailed quantitative insight into these dependencies, better parameterization of algal growth models is required.

scholarly journals The anatomy of the foveola reinvestigated

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4482 ◽  
Author(s):  
Alexander V. Tschulakow ◽  
Theo Oltrup ◽  
Thomas Bende ◽  
Sebastian Schmelzle ◽  
Ulrich Schraermeyer
Keyword(s):  
Light Beam ◽  
Focused Ion Beam ◽  
Light Transmission ◽  
Ion Beam ◽  
Incident Light ◽  
3D Structure ◽  
Müller Cells ◽  
Bright Spot ◽  
Muller Cells ◽  
Outer Segments

Objective In the foveola of the eye, photoreceptors and Müller cells with a unique morphology have been described, but little is known about their 3D structure and orientation. Considering that there is an angle-dependent change in the foveolar photoreceptor response for the same light beam, known as the Stiles Crawford Effect of the first kind (SCE I), which is still not fully understood, a detailed analysis of the anatomy of the foveolar cells might help to clarify this phenomenon. Methods Serial semithin and ultrathin sections, and focused ion beam (FIB) tomography were prepared from 32 foveolae from monkeys (Macaca fascicularis) and humans. Foveolae were also analyzed under the electron microscope. Serial sections and FIB analysis were then used to construct 3D models of central Müller and photoreceptor cells. In addition, we measured the transmission of collimated light under the light microscope at different angles after it had passed through human foveae from flat mounted isolated retinae. Results In monkeys, outer segments of central foveolar cones are twice as long as those from parafoveal cones and do not run completely parallel to the incident light. Unique Müller cells are present in the central foveolae (area of 200 µm in diameter) of humans and monkeys. Light entering the fovea center, which is composed only of cones and Müller cells, at an angle of 0° causes a very bright spot after passing through this area. However, when the angle of the light beam is changed to 10°, less light is measured after transpasssing through the retina, the foveolar center becomes darker and the SCE-like phenomenon is directly visible. Measurements of the intensities of light transmission through the central foveola for the incident angles 0 and 10° resemble the relative luminance efficiency for narrow light bundles as a function of the location where the beam enters the pupil as reported by Stiles and Crawford. The effect persisted after carefully brushing away the outer segments. Conclusion We show that unique cones and Müller cells with light fibre-like properties are present in the center of the fovea. These unique Müller cells cause an angle dependent, SCE-like drop in the intensity of light guided through the foveola. Outer segments from the foveolar cones of monkeys are not straight.

scholarly journals Electronic Tabletop Holographic Display: Design, Implementation, and Evaluation

2019 ◽  
Vol 9 (4) ◽  
pp. 705 ◽  
Author(s):  
Jinwoong Kim ◽  
Yongjun Lim ◽  
Keehoon Hong ◽  
Hayan Kim ◽  
Hyun-Eui Kim ◽  
...  
Keyword(s):  
Motion Parallax ◽  
Type Systems ◽  
Performance Measure ◽  
Display System ◽  
3 Dimensional ◽  
Color Version ◽  
Holographic Display ◽  
Panel Type ◽  
High Level ◽  
Holographic Displays

Most of the previously-tried prototype systems of digital holographic display are of front viewing flat panel-type systems having narrow viewing angle, which do not meet expectations towards holographic displays having more volumetric and realistic 3-dimensional image rendering capability. We have developed a tabletop holographic display system which is capable of 360° rendering of volumetric color hologram moving image, looking much like a real object. Multiple viewers around the display can see the image and perceive very natural binocular as well as motion parallax. We have previously published implementation details of a mono color version of the system, which was the first prototype. In this work, we present requirements, design methods, and the implementation result of a full parallax color tabletop holographic display system, with some recapitulation of motivation and a high-level design concept. We also address the important issue of performance measure and evaluation of a holographic display system and image, with initial results of experiments on our system.

scholarly journals Spatiotemporal multiplexing method for visual field of view extension in holographic displays with naked eye observation

2016 ◽  
Vol 24 (3) ◽  
Author(s):  
G. Finke ◽  
M. Kujawińska ◽  
T. Kozacki ◽  
W. Zaperty
Keyword(s):  
Visual Field ◽  
Optical System ◽  
Wigner Distribution ◽  
Field Of View ◽  
Distribution Analysis ◽  
Holographic Display ◽  
Holographic Imaging ◽  
Naked Eye ◽  
Holographic Displays ◽  
Functional Problems

AbstractIn this paper we propose a method which allows to overcome the basic functional problems in holographic displays with naked eye observation caused by delivering too small images visible in narrow viewing angles. The solution is based on combining the spatiotemporal multiplexing method with a 4f optical system. It enables to increase an aperture of a holographic display and extend the angular visual field of view. The applicability of the modified display is evidenced by Wigner distribution analysis of holographic imaging with spatiotemporal multiplexing method and by the experiments performed at the display demonstrator.

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