Freeform road lighting lens design

Free-form lens design for wide-angle imaging with an equidistance projection scheme

Computation of double freeform optical surfaces using a Monge–Ampère solver: Application to beam shaping

This paper presents a three dimensional lens shaping method for dual-LED packaging module using silicon micromachined substrate. The technology utilizes flower-typed structure and silicone dispensing process to fabricate a 3-D freeform encapsulation lens for achieving uniform illumination and specific light pattern. Based on the experimental results, with the size of 2×4 mm2 of the flower-typed island, the freeform lens is formed with a sag height of 2.7 mm when the dispensing volume is 15 mm3. On the measurement, the projected light pattern is obvious that the light distribution is similar to a rectangular shape, with a good uniformity.

Light flux from LED must be redistributed to meet the needs of lighting in most cases, a new method is proposed for its secondary optic design. Based on refractive equation and energy conservation, a set of first-order partial differential equations which represent the characters of LED source and desired illumination were presented. The freeform lens was constructed by solving these equations numerically. The numerical results showed that we can get a freeform lens for the illumination of uniformity near to 90%, with considerable high computation speed. This method can shorten the designing time of the freeform lens with high accepted tolerance.

Road luminaries are required to provide the luminance specified in the standards according to the road characteristics. For this reason, the light from the light source should be directed according to the desired conditions. While the range of minimum average road surface luminance recommended for different classes of road are provided; at the same time, it is desirable to be economical. In this study, a freeform lens and LED luminaire design with high luminous efficacy, low glare and uniform luminance distribution with a height of 1.5 m and a distance of 7 m between poles were designed for M3 road standards. First of all, lens design was made by using optical and illumination design software. Also, lens manufacturing and luminaire production were made as a result of the success of the design simulation test. The success of the LED luminaire in providing CIE standards has been measured on the designed road. In addition, the advantages and disadvantages have been determined by comparing with High Pressure Sodium Vapor (HPS) lamps.

Glare and visual discomfort are important factors that should be taken into account in illumination design. Conventional freeform lenses offer perfect control over the outgoing intensity distribution, thereby allowing optical radiation patterns with sharp cut-offs in order to optimize the unified glare rating index. However, these freeform lenses do not offer control over the near-field luminance distribution. Observing the emitted light distribution from a high-brightness LED through a freeform lens gives a high peak luminance that can result in glare. To reduce this peak luminance, freeform lenses should be used in conjunction with light diffusing structures. However, this diminishes the control over the outgoing intensity distribution what is the main benefit of a freeform lens. Another approach to reduce the observed peak luminance, is by spreading the emitted light over multiple optical channels via freeform lens arrays. This paper proposes a novel method to design luminance spreading freeform lens arrays that offer perfect control over the resulting intensity pattern. The method is based on a non-invertible mapping of a 2D parameter space. This results in a source-target mapping in which multiple ingoing ray directions are mapped onto every position of the target distribution. The case of continuous and discontinuous mappings are both discussed in this paper. Finally, the example of a discontinuous freeform lens array with 7×7 individual lenses is designed and experimentally demonstrated.

Recent energy efficient illumination advancements have capitalized on using light-emitting diodes (LEDs) in combination with freeform lenses. However, the available freeform lens design methods are application specific. In addition, manufacturing of this class of optics is challenging. In this work, considering manufacturing constraints, we apply a customized algorithm to design freeform lenses for (1) transforming LED radiation into a uniform rectangular illumination pattern and (2) shaping collimated LED light beams into complex image target irradiance distributions. The algorithm is based on a numerical solution of the elliptic Monge–Ampere equation. Then, we proposed manufacturing these lenses using a modified ink-jet 3D printing technology called Printoptical technology. The demonstrated optical performance of printed lenses, exhibiting surface roughness of $\textrm {RMS} = 10\pm 2$RMS=10±2 nm, is in good agreement with the simulation. We also explored an industrial application of the 3D-printed lens matrix for low-cost illumination of a paper milling machine.

An optimization method is proposed for designing an LED freeform lens which produces a uniform circular pattern with high energy efficiency. This method is composed of three main aspects: design of the initial guess, parameterization of the freeform surface, and construction of the merit function. The initial guess is created by solving an ordinary differential equation numerically. An approach of selecting optimization points is introduced for parameterization of the freeform surface. The merit function is constructed by use of the irradiance uniformity and the efficiency of the lens. Design examples are given, and the results show that the irradiance distribution is well controlled with a maximum uniformity (the relative standard deviation of irradiance, RSD) of 0.0122 and a maximum efficiency of 93.88%. This optimization method can be generalized to design freeform lenses with different lighting patterns or without rotational symmetry.

A novel LED fishing/working light is proposed to enhance the lighting efficiency of a fishing boat. The study is focused on the freeform secondary lens design so as to create a lamp that attracts fish and sheds light on the deck for the crew's work. The experimental results show that the proposed multisegmented freeform lens can deliver the proposed aim, giving 3 times as much illuminating power as the traditional high-intensity discharge fishing lamp does with the same input of electrical power.

Freeform lenses play a critical role in LED packaging due to their beam-shaping capabilities. However, existing packaging designs commonly neglect the Fresnel loss effect at multi-interface boundaries. Addressing this gap, this study establishes a synergistic freeform lens design methodology based on a multi-objective optimization framework, achieving breakthroughs in both high light extraction efficiency and optical quality control. Leveraging the Fresnel equations, a multi-interface energy transmission model is constructed to quantitatively characterize the coupled mechanism of total internal reflection and refraction losses. A triobjective optimization scheme was implemented, targeting flux loss minimization, surface curvature regularization, and illuminance uniformity enhancement. Pareto-optimal solutions were generated via the NSGA-II algorithm, balancing Snell's law compliance, differential geometry constraints, and ray-mapping optimization. Experimental validation demonstrated reduced total flux loss from 8.98 to 4.41 lm, suppressed peak surface curvature from 25.4 to 2.42, and improved illuminance uniformity from 0.84 to 0.91. The proposed methodology provides a systematic approach for designing high-efficiency freeform optics with balanced photometric performance.

We propose a design method of asymmetric double freeform surface lens for an integrated LED automobile headlamp and develop an integrated LED automobile optical system. A single asymmetric double freeform surface lens is designed to redistribute rays emitting from the light source for realizing both low and high beams. Moreover, a freeform surface reflector is used to improve the energy efficiency of high beams. The prism placed in the optical path can suppress chromatic dispersion on the edge of the target plane. Simulation and experimental results show that the illumination values and color temperature of the key points can fully meet the requirements of United Nations Economic Commission for Europe vehicle regulations (ECE) R112, 48, and 128. The volume of the whole optical system comprised of freeform surface elements is smaller than that of the low beam system of a traditional headlamp, resulting in saved space, in which other electronic devices can be installed for the safety of the driver, which indicates that the proposed method is practical in the field of automobile lighting.

Most LED luminaires face the problem of color nonuniformity in illumination fields, which seriously degrades their lighting quality. To address this issue, we proposed a freeform TIR lens, which could be applied to the most widely adopted phosphor-converted LEDs and multicolor LED arrays. Based on light pattern overlap and energy mapping, the novel TIR lens comprised the freeform panel and the collimator. Analysis of angular color uniformity (ACU), based on a phosphor-converted white LED model, proved that the normalized standard deviation (NSD) of the LED integrated with the freeform TIR lens significantly decreased from 0.792 to 0.232, compared with the NSD of the traditional TIR lens. Moreover, the proposed TIR lens was also applied to a multiple LED array for color mixing. Both the theoretical analysis and simulation results demonstrated their capability to enhance the ACU. These results demonstrated the effectiveness of the proposed method to improve the uniformity of the LED sources regardless of single or multiple LEDs. The improved lighting quality guarantees good employment of LEDs, especially in the fields of entertainment and architectural lighting.

提出了一种单个透镜目标面照度分布的设计方法，根据背光中Mini-LED光源数量及阵列排布间距、混光距离、目标面光斑半径等信息，建立了背光目标面上照度值与单颗透镜目标面照度分布之间的映射矩阵，通过LSQLIN迭代优化算法得到单颗透镜目标面照度分布，最后采用光源-目标面能量映射法设计双自由曲面透镜。以Mini-LED阵列排布间距为39 mm×30 mm、混光距离为6 mm且目标面光斑半径为40 mm为例进行设计。仿真结果表明，所设计的透镜阵列应用于光源数为5×5的Mini-LED背光时，目标面照度均匀性达到87.45%，对比常用的均匀分布及高斯分布分别提升6.24%和3.34%。本方法在确保背光照度均匀性的前提下降低了透镜设计的计算复杂度，无需大量的后续优化工作，为Mini-LED背光中双自由曲面透镜的设计提供了一种实用有效的方法。

We propose a method for the design of an optical element generating the required irradiance distribution in a rectangular area with a large aspect ratio. Application fields include streetlights, the illumination of halls or corridors, and so forth. The design assumes that the optical element has a complex form and contains two refractive surfaces. The first one converts a spherical beam from the light source to a cylindrical beam. The second one transforms an incident cylindrical beam and generates the required irradiance distribution in the target plane. Two optical elements producing a uniform irradiance distribution from a Cree® XLamp® source in rectangular regions of 17 m × 4 m and 17 m × 2 m are designed. The light efficiency of the designed optical element is larger than 83%, whereas the irradiance nonuniformity is less than 9%.

Freeform lenses can be designed for diverse illumination profiles with good uniformity. However, most of the previous studies formulated for a single point source and the lens to design has a spherical bottom. In this study, the formulation is extended for multiple point sources and for lenses with a flat bottom in favor of prototyping and manufacturing. The extended formulation requires only a freeform surface to design. However, it could be over determined if the light rays emitted from the multiple point sources overlap at the near field. The weighted least-square method is introduced to solve the over-determined problem. A weighting function correlated with the emitting intensities of the sources is proposed to design for illumination profile fit and uniformity in trade-off. The adequacy of the extended formulation is demonstrated by simulation. Circular and rectangular illuminations of multiple point sources in different layouts are illustrated. The simulation results show that profile fit and uniformity could be significantly affected by a source offset. With the offset taken into account in the extended formulation, the effects can be properly collimated.