Free-form lenses for high illumination quality light-emitting diode MR16 lamps
01 Dec 2009-Optical Engineering (International Society for Optics and Photonics)-Vol. 48, Iss: 12, pp 123002
TL;DR: Based on the Monte-Carlo ray-tracing method, numerical simulation results demonstrate that the light output efficiencies of these novel lenses reach as high as 98% and are 17% higher than that of traditional total internal reflection (TIR) MR16 lens as discussed by the authors.
Abstract: Light-emitting diode (LED) MR16 lamps, regarded as one typical general lighting product of LEDs, are being widely used in many applications. Light efficiency into a main beam and uniformity are two key issues for high quality illumination of LED MR16 lamps. In this study, a practical and precise nonimaging optical design method is presented, and two novel 90- and 120-deg free-form lenses for high illumination quality LED MR16 lamps are designed according to this method. Based on the Monte-Carlo ray-tracing method, numerical simulation results demonstrate that the light output efficiencies of these novel lenses reach as high as 98% and are 17% higher than that of traditional total internal reflection (TIR) MR16 lens. Moreover, more than 89% of light exiting from the surfaces of these novel lenses irradiate within the desired receive target, while only 60% irradiate for traditional TIR lens. The uniformities of illuminance distribution across the target of these novel MR16 lamps also are much higher. In addition, these novel lenses are both quite compact and no more than 1/5 of that of the TIR lens. Therefore, these LED MR16 lamps integrated by novel lenses provide an effective solution to high quality illumination.
Citations
More filters
TL;DR: A novel freeform lens was designed for simultaneous realization of LED uniform illumination and conformal phosphor coating, which can realize equivalent illumination uniformity, but the angular color uniformity can be enhanced by 282.3% when compared with the conventionalfreeform lens.
Abstract: A conformal phosphor coating can realize a phosphor layer with uniform thickness, which could enhance the angular color uniformity (ACU) of light-emitting diode (LED) packaging. In this study, a novel freeform lens was designed for simultaneous realization of LED uniform illumination and conformal phosphor coating. The detailed algorithm of the design method, which involves an extended light source and double refractions, was presented. The packaging configuration of the LED modules and the modeling of the light-conversion process were also presented. Monte Carlo ray-tracing simulations were conducted to validate the design method by comparisons with a conventional freeform lens. It is demonstrated that for the LED module with the present freeform lens, the illumination uniformity and ACU was 0.89 and 0.9283, respectively. The present freeform lens can realize equivalent illumination uniformity, but the angular color uniformity can be enhanced by 282.3% when compared with the conventional freeform lens.
99 citations
TL;DR: Analysis and simulation results showed that the method for uniform lighting generated by array of LEDs with large view angle is available for LED array lighting system design on the basis of largeView angle LED.
Abstract: In this research, the condition for uniform lighting generated by array of LEDs with large view angle was studied. The luminous intensity distribution of LED is not monotone decreasing with view angle. A LED with freeform lens was designed as an example for analysis. In a system based on LEDs designed in house with a thickness of 20mm and rectangular arrangement, the condition for uniform lighting was derived and the analytical results demonstrated that the uniformity was not decreasing monotonously with the increasing of LED-to-LED spacing. The illuminance uniformities were calculated with Monte Carlo ray tracing simulations and the uniformity was found to increase with the increasing of certain LED-to-LED spacings anomalously. Another type of large view angle LED and different arrangements were discussed in addition. Both analysis and simulation results showed that the method is available for LED array lighting system design on the basis of large view angle LED..
93 citations
TL;DR: A new reversing design method is proposed to solve the problem of how to optimize light intensity distribution curve (LIDC) and design corresponding optical component to achieve uniform illumination when distance-height ratio (DHR) is given.
Abstract: In light-emitting diode (LED) applications, it is becoming a big issue that how to optimize light intensity distribution curve (LIDC) and design corresponding optical component to achieve uniform illumination when distance-height ratio (DHR) is given. A new reversing design method is proposed to solve this problem, including design and optimization of LIDC to achieve high uniform illumination and a new algorithm of freeform lens to generate the required LIDC by LED light source. According to this method, two new LED modules integrated with freeform lenses are successfully designed for slim direct-lit LED backlighting with thickness of 10mm, and uniformities of illuminance increase from 0.446 to 0.915 and from 0.155 to 0.887 when DHRs are 2 and 3 respectively. Moreover, the number of new LED modules dramatically decreases to 1/9 of the traditional LED modules while achieving similar uniform illumination in backlighting. Therefore, this new method provides a practical and simple way for optical design of LED uniform illumination when DHR is much larger than 1.
83 citations
TL;DR: The freeform lens provided an effective way to achieve white LEDs with high ACU at low cost and was not only at a high level, but also stable when the shape of the phosphor layer changed.
Abstract: We demonstrate a freeform lens to enhance the angular color uniformity (ACU) of white light-emitting diodes (LEDs) whose phosphor layers were coated by freely dispersed coating processes. Monte Carlo ray tracing simulation results indicated that the ACU of the modified LED integrated with the freeform lens significantly increased from 0.334 to 0.957, compared with the traditional LED. Enhancement of ACU reached as high as 186.5%. Moreover, the ACU of the modified LED was not only at a high level, but also stable when the shape of the phosphor layer changed. The freeform lens provided an effective way to achieve white LEDs with high ACU at low cost.
81 citations
TL;DR: The study related in this paper is the design of a ship-mounted LED of high brightness and distant spot and a combination of a freeform lens-coupled parabolic reflector that improved light efficiency to 70%.
Abstract: The study related in this paper is the design of a ship-mounted LED of high brightness and distant spot. The freeform lens design obeying the edge ray principle and Snell’s law is presented first. Then, to fit the illumination requirement of the searchlight, we designed a freeform lens to collimate all the light rays coming from the LED. However, theoretical analysis proves that there is a critical angle for incident rays beyond which the rays cannot be collimated, and 55% is the light-efficiency limit for polymethyl methacrylate freeform lens. We then designed a combination of a freeform lens–coupled parabolic reflector that improved light efficiency to 70%. In this paper, the design of the freeform lens–coupled parabolic reflector is given in detail. In addition, tolerance analysis and the effect of manufacturing defect are presented.
35 citations
References
More filters
TL;DR: The simultaneous multiple surface (SMS) method in 3D geometry is presented in this paper, where two orthotomic input ray bundles and another two output ray bundles are used to provide an optical system with two free-form surfaces that deflects the rays of the input bundles into the corresponding output bundles.
Abstract: The simultaneous multiple surface (SMS) method in 3-D geometry is presented. Given two orthotomic input ray bundles and another two orthotomic output ray bundles, the method provides an optical system with two free-form surfaces that deflects the rays of the input bundles into the rays of the corresponding output bundles and vice versa. In nonimaging applications, the method enables controlling the light emitted by an extended light source much better than single free-form-surface designs, and also enables the optics contour to be shaped without efficiency losses. The method is also expected to find applications in imaging optics.
247 citations
18 Sep 1998
TL;DR: In this paper, an illumination system with a prescribed output pattern consisting of a light source and an optical lens redirecting the light of the source into an output beam is considered, and the shape generated by the following method is defined: the Gaussian sphere establishes a first grid (100) of equal-flux zones of solid angle; a second grid (130) with the same number of equalflux zone of solid angles as the first grid, with a coordinate system topology congruent with that of the first, such that the zones of the second grid are in
Abstract: An illumination system with a prescribed output pattern comprising a light source and an optical lens redirecting the light of the source into an output beam, the lens with multiple surfaces (100, 130, 120) at least one of which has shape that is not a surface of revolution, the shape generated by the following method: the Gaussian sphere establishes a first grid (100) of equal-flux zones of solid angle; a second grid (130) with the same number of equal-flux zones of solid angles as the first grid, with a coordinate-system topology congruent with that of the first grid, such that the zones of the second grid are in one-to-one correspondence with the zones of the first grid (100), according to the local transmittance of the lens, with either of both of the grids being rotationally non-symmetric; by this correspondence define a flux-redistributing directional mapping function from the first Gaussian sphere to the second Gaussian sphere, whereby any light ray from the source can be assigned a direction in the output beam, according to the zone of the second grid (130) into which the ray falls, so that the redirected ray falls in corresponding zone of the first grid.
175 citations
TL;DR: A novel LED modeling algorithm for precise three-dimensional light pattern simulation is proposed and demonstrated to obtain an average of 99% in normalized cross correlation between the simulation light pattern and experimental measurement for a truncated inverse pyramid LED.
Abstract: A novel LED modeling algorithm for precise three-dimensional light pattern simulation is proposed and demonstrated. We propose to use normalized cross correlation to verify the validity of the simulation in one-dimensional intensity patterns as well as two-dimensional irradiance patterns in various midfield distances and to provide feedback to achieve a successful model. The model is demonstrated to obtain an average of 99% in normalized cross correlation between the simulation light pattern and experimental measurement for a truncated inverse pyramid LED.
156 citations
TL;DR: For the problem of point source forming prescribed irradiance, a new method-variable separation mapping method is presented, which establishes separately the correspondence between variables on the light source and the target plane.
Abstract: For the problem of point source forming prescribed irradiance, a new, to the best of our knowledge, method-variable separation mapping method is presented, which establishes separately the correspondence between variables on the light source and the target plane. The role played by the optical surfaces is then to redirect the light rays to their corresponding target points. The surface of the lens is determined by first calculating the surface points and then their normal vectors. Considering that normal deviations are produced in the surface construction process, a normal deviation control method is also presented to restrict the deviation. With this normal deviation control method, discontinuities are introduced onto the lens surface. From these mapping and normal control methods, a fast and efficient algorithm has been developed for several prescribed irradiance problems with simple nonrotational shape of the illuminated region.
153 citations
01 Jan 2005
51 citations