Natural light illumination system

In recent years, green energy has undergone a lot of development and has been the subject of many applications. Many research studies have focused on illumination with sunlight as a means of saving energy and creating healthy lighting. Natural light illumination systems have collecting, transmitting, and lighting elements. Today, most daylight collectors use dynamic concentrators; these include Sun tracking systems. However, this design is too expensive to be cost effective. To create a low-cost collector that can be easily installed on a large building, we have designed a static concentrator, which is prismatic and cascadable, to collect sunlight for indoor illumination. The transmission component uses a large number of optical fibers. Because optical fibers are expensive, this means that most of the cost for the system will be related to transmission. In this paper, we also use a prismatic structure to design an optical coupler for coupling n to 1. With the n-to-1 coupler, the number of optical fibers necessary can be greatly reduced. Although this new natural light illumination system can effectively guide collected sunlight and send it to the basement or to other indoor places for healthy lighting, previously there has been no way to manage the collected sunlight when lighting was not desired. To solve this problem, we have designed an optical switch and a beam splitter to control and separate the transmitted light. When replacing traditional sources, the lighting should have similar characteristics, such as intensity distribution and geometric parameters, to those of traditional artificial sources. We have designed, simulated, and optimized an illumination lightpipe with a dot pattern to redistribute the collected sunlight from the natural light illumination system such that it equals the qualities of a traditional lighting system. We also provide an active lighting module that provides lighting from the natural light illumination system or LED auxiliary sources, depending on circumstances. The system is controlled by a light detector. We used optical simulation tools to design and simulate the efficiency of the active module. Finally, we used the natural light illumination system to provide natural illumination for a traffic tunnel. This system will provide a great number of benefits for the people who use it.     

LED背景光源反射棱镜的设计

全站仪反射棱镜在暗环境中测量会影响照准精度,为了实现全站仪反射棱镜能够在暗环境中正常使用,对全站仪反射棱镜进行了改进．在反射棱镜中引入LED发光二极管作为背景光源的装置,并通过实验验证了这种装置的可行性．首先,介绍了反射棱镜的结构构造以及工作原理;然后说明了LED发光二极管的优势及改进装置电路的设计;最后,通过实验验证了这种改进装置应用的可行性,实验选择从温度、距离两方面检验该装置对测量工作是否产生影响．2次不同室温温度测试结果证明了该装置产生的温度不会对测量产生影响;距离测试结果证明该装置不会对距离测量产生影响．由以上实验结论证明了这种改进装置的可行性．     

Thin liquid-crystal display backlight system with highly scattering optical transmission polymers

We describe an advanced highly scattering optical transmission (HSOT) polymer backlight system that has shown twice the brightness of a conventional transparent system in spite of its having a thinner backlight. The HSOT polymer that contains optimized heterogeneous structures produced homogeneous scattered light with forward directivity and sufficient color uniformity. Although it was thought that polymers for light-guide plates (LGPs) must be transparent to minimize scattering, we have come to the conclusion that the HSOT polymer, which is not an absorping medium but a scattering medium, is a more suitable medium for LGPs.     

One‐Dimensional Dielectric/Metallic Hybrid Materials for Photonic Applications

Explorations of 1D nanostructures have led to great progress in the area of nanophotonics in the past decades. Based on either dielectric or metallic materials, a variety of 1D photonic devices have been developed, such as nanolasers, waveguides, optical switches, and routers. What's interesting is that these dielectric systems enjoy low propagation losses and usually possess active optical performance, but they have a diffraction‐limited field confinement. Alternatively, metallic systems can guide light on deep subwavelength scales, but they suffer from high metallic absorption and can work as passive devices only. Thus, the idea to construct a hybrid system that combines the merits of both dielectric and metallic materials was proposed. To date, unprecedented optical properties have been achieved in various 1D hybrid systems, which manifest great potential for functional nanophotonic devices. Here, the focus is on recent advances in 1D dielectric/metallic hybrid systems, with a special emphasis on novel structure design, rational fabrication techniques, unique performance, as well as their wide application in photonic components. Gaining a better understanding of hybrid systems would benefit the design of nanophotonic components aimed at optical information processing.     

Temperature Measurement Technique for Stabilizing the Light Output of RGB LED Lamps

The efficiency of light-emitting-diode (LED) lights approaches that of fluorescent lamps. LED light sources find more applications than conventional light bulbs due to their compactness, lower heat dissipation, and real-time color-changing capability. Stabilizing the colors of red–green–blue (RGB) LED lights is a challenging task, which includes color light intensity control using switching-mode power converters, color point maintenance against LED junction temperature change, and limiting LED device temperature to prolong the LED lifetime. In this paper, we present a LED junction temperature measurement technique for a pulsewidth modulation diode forward current controlled RGB LED lighting system. The technique has been automated and can effectively stabilize the color without the need for using expensive feedback systems that involve light sensors. Performance in terms of chromaticity and luminance stability for a temperature-compensated RGB LED system will be presented.      

一种新型全光纤弹速测量系统的研制

研制了一种新型的利用激光光束反射原理的全光纤弹速测量系统。该系统采用了全光纤结构和光纤耦合器等无源器件,以输出光功率1mW, 工作波长1300nm的半导体激光器作为测试系统的光源,用光纤耦合器进行分光,实现了在一根光纤中同时传输光源和接受目标反射的信号光,避免了复杂的调节和准直过程。该系统结构简单、可靠性高,利用它,成功地测量了霍普金森杆发射的子弹速度,结果表明其速度测量相对不确定度小于1%。     

Q-point estimation for an LED arrangement in a large-scale lighting display using the mean value approach

A generalized light-emitting diode (LED) arrangement using the mean point (also known as the Q-point) approach from the well-known mean value theorem is proposed to simplify the estimation of LED combinations in large-scale lighting displays. A power dissipation (PD) curve built by N LEDs in series is explored to guide the estimation in a definite route, in which the estimation for the LED arrangement and power requirement can be quickly acquired, even in multiple estimations. With the Q-point, the estimation process can be easily achieved by simply taking the square root of a total of N LEDs. This is much faster than the usual step-by-step bisection estimation. Accordingly, further estimation can continue along the PD curve until the resultant combination is suitable for practical use. A non-integer adjustment reconciling to reach the feasible application is only tailored to the decimal part of the estimation number after integer estimation. The luminance distribution in the direct backlight panel is measured using a nine-hole window frame, which shows an average luminance between each pair of holes of about 1.15 kcd/m². This is quite similar to a surface light source before using a light filter.     

Refraction and diffraction by a metal-dielectric multilayered structure

An optical refraction prism consisting of metal and dielectric, subwavelength, periodic multilayered thin films has been proposed. The multilayered structure of metal and dielectric thin films has a cylindrical dispersion surface for TM polarized light. The light behaviors are very different from those of conventional glass prisms and photonic crystal superprisms. Refraction and diffraction of the light wave for the metal-dielectric multilayered prism has been investigated by numerical simulations and graphical representation based on the dispersion surface. A prism with 0.2 microm period had an angular dispersion of 0.20 degrees /nm for approximately 0.8 microm wavelength light. The finite thick metal-dielectric multilayered structure acted as a slab waveguide.     

Electro-optical logic application of multimode interference coupler by multivalued controlling

Electro-optical hybrid logic is a potential solution to implement both electrical and optical signal processing, which receives analog or digital, electrical or optical signals and produces logic signals in a desired manner. In light of the transfer matrix theory, we found that one can steer light into different output ports of a multimode interference coupler by controlling the phases in a multivalued manner on the image-extended arms. This implementation acts as an analog-to-digital convertor from electric domain to optical domain. Also, an electrical-to-optical 2-to-2(2) binary-coded decoder is described and examined by the 3D beam propagation method.     

Low-Frequency Electrical Signal Measurement by Electrooptical Methods

An analog system for the optical telemetry of voltage or current information using light-emitting diodes (LED) is described. Errors resulting from variations in the optical coupling efficiency are minimized because the light emitted by the LED contains the signal to be measured superimposed on a fixed intensity beam controlled by a reference zener diode. The nonlinearity of the LED is overcome by using part of its emitted light to control the feedback current to an operational amplifier that supplies the signal to the LED. The prototype system developed has a total error of approximately 0.2 percent of the input signal.     

A hybrid humidity sensor using optical waveguides on a quartz crystal microbalance

In this study, slab and ridge optical waveguides (OWGs) made of fluorinated polyimides were deposited on a quartz crystal microbalance (QCM), and hybrid sensors using OWG spectroscopy and the QCM technique were prepared. Polyvinyl alcohol (PVA) film with CoCl₂ was deposited on the OWGs, and the characteristics of humidity sensing were investigated. A prism coupler was used to enter a He–Ne laser beam (λ = 632.8 nm) to the slab OWG. The output light intensity markedly changed due to chromism of the CoCl₂ as a result of humidity sorption, and this change was dependent on the incident angle of the laser beam to the slab OWG. During the measurement of output light, the QCM frequency was simultaneously monitored. The humidity dependence of the sensor with the slab OWG was also investigated in the range from 15 to 85%. For the sensor with the ridge OWG, white light was entered by butt-coupling, and the characteristics of humidity sensing were investigated by observing the output light spectrum and the QCM frequency.     

Comparison between two detection systems for fiber-optic chemical sensor applications

Two optical detection system designs are compared for fiber-optic chemical sensor applications. A single grating spectrograph with fiber-optic input and photodiodes at three different wavelengths is compared to 1x3 fiber-optic splitters and photodiode detectors with integrated interference filters. The splitters are used to direct the optical power to the filter photodiodes. Three types of 1x3 commercially available splitters were tested: a 400 microm fused glass fiber-optic coupler, a 1000 microm fused plastic fiber-optic coupler, and a 1000 microm glass fiber-optic bundle. This study finds that the fiber-splitter-based detection systems have similar stray light, signal-to-noise ratio, and long-term absorbance stability compared to the spectrograph detection system with a modest improvement in spectral resolution (from approximately 12 nm to approximately 6 nm). It is also much smaller in size and lower in cost. Applications of the two systems in a colorimetric CO2 partial pressure sensor are compared and similar accuracy and precision are achieved.     

Random-dot pattern design of a light guide in an edge-lit backlight: integration of optical design and dot generation scheme by the molecular-dynamics method

We present the methodology of an integration of a dot generation scheme by a molecular-dynamics (MD) method and the subsequent software optical design phase by software. The MD dot generation scheme proposed has great advantages when integrated into the optical design phase. These advantages include the variable r-cut and reflective boundary condition techniques, both of which could achieve a high-density variation of dot distribution. In addition, we use a cell technique where the domain is divided into a number of smaller cells, allowing for flexibility in adjusting the dot density within each cell, as well as for using the add-on or remove-from technique of the dots in one cell to achieve an equal-luminance condition. In addition, a simple proportional rule of luminance to dot density is also proposed to perform dot optimization. Finally, an illustration is shown for the optimal dot distribution of a LED backlight. The result that a two-dimensional dot density distribution near the light source changes gradually to a one-dimensional dot density distribution with increasing distance from the light source shows the validity of the present integration of the MD dot generation scheme into the optical design phase.     

Novel real-time joint-transform correlation by use of acousto-optic heterodyning

To replace the film recording aspect of performing optical correlation, conventional real-time joint-transform correlation (JTC) optical systems make use of a spatial light modulator (SLM) located in the Fourier plane to record the joint-transform power spectrum (JPS) to achieve real-time processing. The use of an SLM in the Fourier plane, however, is a major drawback in these systems because SLMs are limited in resolution, phase uniformity, and contrast ratio, which are, therefore, not desirable for robust applications. We propose a hybrid (optical/electronic) processing technique to achieve real-time joint-transform correlation. The technique employs acousto-optic heterodyning scanning. The proposed real-time JTC system does not require an SLM at the Fourier plane as in other real-time JTC systems. This departure from the conventional scheme is extremely important as the proposed approach does not depend on SLM issues. We develop the theory of the technique and substantiate it with experimental results.     

Novel system for coupling to surface-plasmon polaritons

A novel system for coupling to surface-plasmon polaritons has been designed, fabricated, and assembled. Microcomputer controlled electronics provide for accurate and repeatable angular positioning of the waveguide coupler with respect to the incident beam and for precise angular registration of detector output signals. The optical components, combined with a retroreflecting spherical-surface coupling prism, give apertured control of the beam profile at the coupling interface.     

Spatial fourier spectroscopy of guided modes in low-dimensional structures

A new methodology for the study of low-dimensional thin-film structures and a new technique to determine nanolayer thickness are considered. These are based on recording and processing the changes in an angular Fourier spectrum of a light beam reflected from a prism coupler to excite the guided mode in a thin-film structure when the incident light beam intensity is increased.     

Nanohot embossing using curved stage to replicate antireflection nanostructures onto light guide

A nanohot embossing using a curved stage is proposed to improve the replication ratio of nanostructures at near the edge of a thick (sub-mm-order thickness) polymer substrate. The lower replication ratio at near the edge resulting from a conventional hot embossing is due to lower compressive stress, which is simulated by the finite-element method (FEM). The height of the proposed curved stage is gradually increased from the center to the edge to bring the levels of compressive stress at the center and at the edge closer. Here, we demonstrate replications of antireflection nanostructures, which have both pitch and height of 200 nm, onto the 0.75-mm-thick light guide for the light emitting diode (LED) frontlight systems used in mobile phones. It was found that a cutting depth of 14 μm on the curved stage is necessary to achieve a high uniformity of the replication ratio at near the edge. The replication ratio at near the edge is improved from 65% to 94%. The reflectance of the antireflection structures is 0.6%, which is a high enough quality for use in LED frontlight systems.     

High efficiency pocket-size projector with a compact projection lens and a light emitting diode-based light source system

We present a light emitting diode (LED)-based ultramini digital micromirror device projector with a size of 75 mm x 67 mm x 42 mm and a weight of 338 g. The LED illuminator inside this projector makes it possible to achieve a volume of 18 cm(3) by using a dichroic filter and a collimating lens. The illumination system consists of high uniformity of 93% through a microlens array as a homogenizer. A total internal reflection prism is also used to reduce the size of both the illumination system and the telecentric projection lens. A projection lens system with an ultrasmall track of 42 mm, including a high modulation transfer function value of 0.4 at 46.2 line pairs/mm, an optical distortion of only 0.25 %, and a television distortion of 0.01%, is designed. Through the above superior specification, we can produce a 20 in. (51 cm) color display comparable in brightness to a laptop with a contrast of 3700:1. The device is compact and suitable for personal use.     

Evaluation of diffraction loss in prism light guides by finite-difference time-domain field modeling

Prism light guides are hollow dielectric tubes that use prismatic facets to guide light by means of total internal reflection. An unresolved problem has been to determine the magnitude of loss caused by diffraction in prism light guides. Neither experimental measurement nor an analytical solution has yet been achieved, so we attacked the problem numerically, in two steps. First, we found a way to represent such a transitionally invariant three-dimensional system as an equivalent two-dimensional problem. Second, we employed the finite-difference time-domain algorithm, with periodic boundary conditions, to yield a computation problem of manageable size. We found that the diffraction-induced transmissivity of a prism light guide wall is of the order of the wavelength divided by the prism size-a result that has encouraging practical implications.     

Enhanced light output of angled sidewall light-emitting diodes with reflective silver films

A proof-of-concept of applying laser micro-machining to fabricate high performance GaN light-emitting diode (LED) was presented in this study. Laser micro-machining was applied to fabricate GaN LED chip with angled sidewalls (ALED). The inclined sapphire sidewalls were coated with highly reflective silver film which functions as an efficient light out-coupling medium for photons within the LED structure. Thus, more laterally-propagating photons can be redirected to the upward direction of the ALED with silver coating (Ag-ALED). Performances of the Ag-ALED, ALED and conventional planar GaN LED were evaluated. At an injection current of 30 mA, the light output intensity of Ag-ALED was significantly improved by 97% and 195% as compared to ALED and conventional planar LED, respectively. The corresponding wall-plug efficiency of Ag-ALED was remarkably increased by 95% and 193% as compared to ALED and conventional planar LED, respectively. The results of this study demonstrated that the Ag-ALED showed a pronounced increase in light output intensity compared to conventional planar LED, which may have many potential applications in the field of display engineering.