Secondary Optical Design Research Articles

Small-divergent-angle uniform illumination with enhanced luminance of transmissive phosphor-converted white laser diode by secondary optics design

With the advantage of low etendue and no efficiency droop, phosphor-converted white laser diode (pc-WLD) has been a very promising candidate in future high-luminance solid-state lighting. To obtain high brightness, the blue laser beam is usually collimated or focused onto a yellow phosphor layer, which may result in poor angular color uniformity (ACU). In this study, we observed the blue spot and yellow ring phenomenon of the transmissive pc-WLD, which is attributed to the mismatch between the focused intensity distribution of the blue light and the divergent intensity distribution of the yellow light. Then, we proposed a secondary optics consisting of a parabolic reflector coupled with a freeform lens to enhance the ACU by collimating all the rays emitting from the phosphor, which is located at the focus of the reflector. Through this design, we achieved the match of the intensity distribution of the blue and yellow lights, resulting in a high ACU of 0.85 with a view angle of ±10° by simulation. Moreover, the luminance of the pc-WLD can be enhanced by about four times using this method. Finally, we fabricated a prototype of the designed secondary optics and validated the effectiveness of the proposed method in achieving small-divergent-angle uniform illumination with enhanced luminance of the transmissive pc-WLD.

基于折射率预补偿方法的扩展光源匀光照明二次光学设计

基于折射率预补偿方法的扩展光源匀光照明二次光学设计

Design optimization of ultra-high concentrator photovoltaic system using two-stage non-imaging solar concentrator

This paper presents a systematic approach for optimizing the design of ultra-high concentrator photovoltaic (UHCPV) system comprised of non-imaging dish concentrator (primary optical element) and crossed compound parabolic concentrator (secondary optical element). The optimization process includes the design of primary and secondary optics by considering the focal distance, spillage losses and rim angle of the dish concentrator. The imperfection factors, i.e. mirror reflectivity of 93%, lens’ optical efficiency of 85%, circumsolar ratio of 0.2 and mirror surface slope error of 2 mrad, were considered in the simulation to avoid the overestimation of output power. The proposed UHCPV system is capable of attaining effective ultra-high solar concentration ratio of 1475 suns and DC system efficiency of 31.8%.

The design of LED rectangular uniform illumination lens system

Freeform lenses are playing a more and more important role in LED secondary optics design. In this paper, based on the lighting-energy conservation law, edge-ray principle and Snell's law, we present a freeform lens optical system design method for LED lighting. This system can achieve rectangular lighting area, and it is easier to precisely control the angle of light emitting and processing, with the advantages of uniform illumination. The software Matlab and Rhino were used to get the model of lens, and the PMMA was used as the material to design lens model. Finally, the numerical simulation results showed that the spot shape was close to the expected results.

Design and experimental test of refractive secondary optics on the electrical performance of a 3-junction cell used in CPV systems

This work analyzes and compares the effects of the secondary optics on the performance of a triple junction solar cell used in a compact HCPV prototype unit.The HCPV system is composed of triple junction III-V (Ga0.5In0.5P, Ga0.99In0.01As and Ge) solar cells that have a circular shape with an active area of 4.15mm2. The optics consists of a primary PMMA square Fresnel lens (75mm – side) with constant pitch and a refractive secondary optic (RTP) made of dielectric material. The overall geometrical concentration ratio is 1300×. The tracking system is a tip-tilt type two-axis mechanism driven by stepper motors. The HCPV secondary optics were firstly designed at Polo Tecnologico Andrea Galvani and then tested on the prototype unit at the Engineering Faculty of Università Politecnica delle Marche in Ancona, Central Italy.The aim of the paper is to present the numerical and experimental performance results of two different secondary optics and to assess the effects of the main construction parameters (i.e.: the geometry of the secondary optics and the distance between the two optics) on the concentration efficiency. Moreover, two different 3J cell receiver types were tested, the Insulated Metal Substrate technology (IMS) and the Direct Bonded Copper (DBC) technologies. The experimental tests were performed under real outdoor operating conditions, therefore also the Direct Normal Irradiance (DNI) was measured. In general, the free-form optics showed significant improvements in terms of overall irradiance and homogeneity.In the best configuration the electric efficiency achieved 39.55%, neglecting the primary optics losses, thus confirming that the presented system setup is able to reach the highest standards of CPV technology performance.

Secondary Optical Design for LED Backlight Luminance Improvement of Helmet-Mounted Display

Secondary optics based on nonimaging optical theory has been widely used in street lighting to form a uniform rectangular illumination. When used in LCD backlight, the purpose of the secondary optics is to control LED emitting light to make them illuminate on the display area as much as possible, which can effectively increase the luminance. The paper first designs a double-freeform-surface lens to collimate light emitted from a LED. The lens is then cut to be rectangular. The simulation results show that the thickness has to be reduced to improve the uniformity. Four optimized lenses are then combined to form a 2 $\times$ 2 lens array. A dark strip along the minor axis appears and the detailed analysis is performed. A lens with the edge light slightly divergent can improve the uniformity. The backlight prototype with and without such lens array is measured. The practical measurement results show that with the same optical films, the luminance with the lens array increases by 96.4%, compared to the one without the lens array. The uniformity is almost same. However, the viewing angle with the lens array decreases to 23 $^{\circ}$ from 39 $^{\circ}$ of without the lens array.

The Secondary Optical Design and Fabrication for the Uniform Illuminating LED Spotlight Using TIR Lens

Different with the fact that the traditional imaging optics emphasizes its ability to get clear image on the image plane, the purpose of LED illumination design is to meet the requirement of high availability of optical energy and homogeneity of illumination. As the study object, the LED track lighting has been designed with secondary optical design by the Lighttools design software. After using TIR lens which has two ways of concentrating: reflectors and lenses, the exit light of the spotlight will be adjusted and the illuminated surface will be with high homogeneity. Therefore, it will reduce the harm of the light to human’s eyes. In this study, the LED spotlights have been produced and tested with the corresponding test results: Lighting power is 7W, luminous efficiency is 82.57lm/W, color rendering index is 83.7, the main wavelength is 488.2nm, the ratio of red, green, blue is 13.1: 83.0: 3.9.

전방향으로 발광하는 LED Bulb를 위한 2차 광학계 설계

Secondary optical system designed for LED bulb which emits light in all directions was simulated with Energy Star standards. Components of the optical system were LED light source, the cover of the LED bulb and reflector which is to confirm the diffuser plate and LightTools software was used to design the illumination optics. The main points of the secondary optical system design are the location of the LED light source, the shape of the LED bulb cover, the location of the reflection plate, and the scattering properties of the diffusing plate. Mechanism of the LED bulb is that the light emitted from the light source move on to the backward after reflected by the coated light cover from the inside and then the reflected light is scattered by the diffuser plate. The LED bulb was designed to satisfy the standard light distribution and color specifications of the Energy Star(IES LM-79-08).

Color Shift Investigations for LED Secondary Optical Designs: Comparison between BPA-PC and PMMA

Recently, color shift of LED-based lighting products has attracted much attention due to its increasing impact on the field application. However, significant research investigations on the color shift mechanisms are not publically available especially for important transmission materials used for secondary optical design. In this paper, broadly used such commercial materials (BPA-PC and PMMA) are experimentally investigated on the color shift effects during aging. Besides this, color shift mechanisms of degradation of transmittance are also studied. Results revealed: (1) Inconsistent degradation of wavelength–dependent transmittance induces the decrease of the blue/yellow light intensity ratio and thus gives rise to the color shift toward the yellow field, which is the color shift mechanism of BPA-PC; (2) Even for the non-aged BPA-PC, the transmittance varies with wavelength in the visible light field due to the chemistry of the material, which caused the change of intensify ratio of blue light to yellow light in the SPD, leading to color change in perception; (3) Oxidation plays a key role in the degradation of transmittance at around the peak wavelength of the blue light field, which is in correlation with the discoloration of thermally-aged BPA-PC materials. By contrast, for the PMMA specimen aged up to 3000h, oxidation was neither occurred at 85°C, nor with additional exposure to blue light, nor even with additional humidity of 85%RH.

聚光模组二次光学元件优化设计与研究

聚光模组二次光学元件优化设计与研究

Investigation on optical property of diffuser with 3D microstructures

The light diffuser with 3D microstructure is one of the high efficient light diffusers used in LED lighting to realize secondary optical design. The aspect ratio (AR), filling coefficient (FC) and arrangement (A) of microstructure plays an important role in the optical property of light diffuser. The experiment results and simulation results obtained from Light Tools software of light diffuser with microsphere structure used in LED light shows that the optical property of diffuser with microsphere structure whose diameter is from 0.1mm to 1.0mm, arranged in hexagon is best with AR of 0.22 and the filling coefficient of 100%.

Design of Quasi Free Surface Secondary Optical Lens for LED Auto Taillights

Owing to its high energy efficiency, high color rendering and long life, LED lamps are promising in the field of Lighting. However, it is much more important to design a secondary optical lens for the LED lamps to obtain good output efficiency and a good light distribution pattern than to light the lamps. In the field of auto lamps, LED has more advantages than the traditional lamps. In this paper, we proposed and developed a secondary optical lens design blueprint for LED auto taillights. A quasi free surface based on the cone lens for auto taillights was designed and the desired illumination was achieved. We present the design procedure of the lens. The simulation of the auto tail-lights is carried out in Tracepro 7.0. The results show that the lens can rearrange the luminous flux accurately and reasonably. An auto taillight with a uniform and rectangular luminous flux distribution is obtained

Secondary optical element design for intracorporeal LED illumination system

In this Letter, we propose an intracorporeal illumination system for providing uniform and wide-field illumination during minimally invasive surgery. The illumination system is comprised of an Alexis wound retractor, a set of LEDs, and secondary optical elements (SOEs). The SOE was composed of a Fresnel lens and a total internal reflection lens, which was designed to improve the optical performance of the LED. The results of simulation demonstrate that the optical efficiency of each LED with an SOE could be increased from 33.6% to 82.9%. To avoid damage to human tissue by thermal effect, the number of LEDs with SOEs was optimized. The results indicate that our design to be applicable for practical surgery.

Secondary Optical Design of LED Stage Lamps

High brightness and high power light emitting diode (LED) based lamps have been identified as one of the solutions for energy saving light sources in illumination. Owing to its high energy efficiency, high color rendering and long life, LED lamps are promising. However, it is important to design a secondary optical lens for the LED lamps to obtain good output efficiency and a good light distribution pattern. In this paper, we proposed and developed a secondary optical lens design blueprint for LED stage lamps. A cone lens for stage lamps was designed and the desired illumination was achieved. The design procedure of the cone lens is presented. The simulation of the stage lamps is carried out in Tracepro 7.0. The results show that the cone lens can rearrange the luminous flux accurately and reasonably. A stage lamp with a uniform and circular luminous flux distribution is obtained.

Design of Polygon Prism Optical Lens for LED Street Lamps

High-power light emitting diode (LED) develops greatly owing to its high energy efficiency, high color rendering and long life. However, it is important to design a secondary optical lens for the LED lamps to obtain a good output efficiency and light distribution pattern. The purpose of the secondary optical design for light emitting diode (LED) illumination is to rearrange the luminous flux output of LED and then achieve the desired luminous intensity distribution. In this paper, a polygon prism lens for street lamps was designed and the desired illumination was achieved. The design procedure of the polygon prism lens is presented. The simulation of the street lamps is implemented using Tracepro 7.0. The results show that the polygon prism lens can distribute the luminous flux accurately and reasonably. The luminous flux can be saved as much as possible and a rectangular distribution of luminous flux is attained.

Study and Design of LED Lighting Systems

In this study, the optical characteristics, thermal characteristics, electrical characteristics of the LED device are studied. After analysis of the significance of the optical model, we establish the model of the LED light source using optical simulation software to analyze the impact of modeling four factors and law, based on ray tracing model intensity distribution with the manufacturers. On this basis, we expand the LED secondary optical design, namely, increasing of LDE method to the light level. After comparing different forms of non-imaging optical components, combined with the actual situation, the final choice is the system composed of rotating parabolic reflector with LDE. Besides, the reflected changing the relative position of the body and LDE space lead to the normal light intensity of the entire system appearing two peaks, but their causes are different. In addition, the method of combining theoretical analysis and computer simulations to study the distribution of LDE array illumination is utilized. Formula on the illumination distribution in the LDB array to a plane parallel thereto is deduced, which is verified by computer simulation and agrees well with it. A quantitative study of the factors affecting the road surface illuminance distribution is made on the basis of previous study, combined with the actual road lighting works. These factors are: LDE array form, the number of LED, spacing between LDE, LDE interval between the street lamps. The derived entire road illumination distribution formula and the corresponding curve gives a basic method for the analysis of such practical problems related outcomes for the LDE illumination optical system design and research basis.

Design of secondary optics for IRED in active night vision systems

An effective optical design method is proposed to solve the problem of adjustable view angle for infrared illuminator in active night vision systems. A novel total internal reflection (TIR) lens with three segments of the side surface is designed as the secondary optics of infrared emitting diode (IRED). It can provide three modes with different view angles to achieve a complete coverage of the monitored area. As an example, a novel TIR lens is designed for SONY FCB-EX 480CP camera. Optical performance of the novel TIR lens is investigated by both numerical simulation and experiments. The results demonstrate that it can meet the requirements of different irradiation distances quit well with view angles of 7.5°, 22° and 50°. The mean optical efficiency is improved from 62% to 75% and the mean irradiance uniformity is improved from 65% to 85% compared with the traditional structure.

The First High Solar Concentrator System Performance Test in Korea

The worldwide CPV(Concentrated Photo Voltaic) market has been increased rapidly due to the increase in large-scale PV(Photo Voltaic) plants which are situated in sun-rich areas with either a Mediterranean or equatorial-type climate. CPV systems are arguably some of the most important devices in the production of electricity within regions with a sun-rich climate, particularly those which benefit from abundant direct solar irradiation. We have developed a 500X CPV module with rated power of 170Wp. The CPV module must satisfy the constraint of having a sensitive tracking accuracy due to the limited tolerance of the acceptance angle in intrinsic optical design. In this study, the acceptance angle used was designed with a tolerance angle of ±1° in the secondary optics design. In general, non-concentrated module type 2-axis trackers have a tolerance angle larger than ±1° due to standard silicon-type modules which are insensitive to the tracking accuracy of the sun. They have a tolerance angle of ±2~4°, which fails to exert a significant influence on the performance of the module. This paper provides a study of an experimental variation of the efficiency of the CPV module in terms of its tracking accuracy. Also, the performance of the module is studied from the perspective of temperature and direct irradiation.

The Research of LED Arrays for Uniform Illumination

Nowadays, light emitting diodes (LEDs) are becoming a natural source choice for display illumination due to their small size, lower power consumption as well as lower heat generation. To be useful in practical display applications and to further improve the performance of LED-based illumination system, a secondary optical design for LED illumination is required to rearrange the direct output of LEDs so as to achieve a desired illumination. In this paper, a numerical modeling based on the direct datasheet fit is used to optimize and analyze the uniform illumination system designs, and close attention is paid to the LED source model. The uniformity of typical square and circular array distributions are analyzed for a commercial non-perfect Lambertian LED model.

Optical Design of LED Street Lights

High-power light emitting diode (LED) develops greatly owing to its energy efficiency, light mono-direction and long operating life. But it is critical to have a secondary optics design for the LED street light, for obtaining good output efficiency and light distribution pattern. This article introduces many advantages of LED as street lightings source, and also analyzes the status and features of LED lamps’ application as street lightings. This article mainly designs a secondary optical light distribution implement using Lighttools 7.1. This paper also gives an example of one kind of freeform surfaces lens which can realize rectangular light shape.