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Application specific LED packaging (ASLP) is an emerging technology for high performance LED lighting. We introduced a practical design method of compact freeform lens for extended sources used in ASLP. A new ASLP for road lighting was successfully obtained by integrating a polycarbonate compact freeform lens of small form factor with traditional L...
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... diode (LED), with increasing luminous flux and lumen efficiency in recent years, has more and more applications in our daily life, such as road lighting, backlighting for LCD display, headlamps of automotives, interior and exterior lighting, etc [1–3]. Brighter, smaller, smarter and cheaper are development trends of both LED packaging modules and luminaires [3]. For example, smaller LED packaging using less material will decline the cost of LED modules. In LED applications, secondary optics are essential for most LED luminaires because radiation patterns of most LEDs are circular symmetry with non-uniform illuminance distribution, which cannot directly meet the requirements of specific applications (e. g. subrectangular radiation pattern required in road lighting). Freeform lens is an emerging optical technology with advantages of being high design freedom and being precise light irradiation control, which are useful for LED lighting design [4–8]. Traditional freeform lens, however, due to the category of secondary optics in nature, has disadvantages of large size in some space confined applications, possibly resulting in large volume and weight of both thermal management part and luminaires, relatively low system optical efficiency and inconvenience for customers to assembly. In addition, the optical performances of many LED luminaires existing in the market are quite poor, mainly due to a lack of technology of secondary optics for many new LED companies. On the other hand, thousands of traditional lighting companies, which have been main bodies of employment and marketing and sales, are suffering from even poor understanding of LEDs, facing significant technical and societal challenges of transferring from traditional lighting to new LED business, proposing a strong need for easy to use LED technology. Therefore, if we integrate secondary optics with traditional LED packaging achieving new application specific LED packaging (ASLP), as shown in Fig. 1, it will not only decrease the size of LED modules and systems, and increase the efficiencies of LED luminaires, but also provide a convincing solution to LED lighting for old and new LED application companies. In this study, we demonstrated a practical design method of compact freeform lenses, mainly focusing on eliminating deteriorations caused by extended sources. A polycarbonate (PC) compact freeform lens for a new ASLP used in road lighting was designed based on this method. Optical performance of the ASLP was also studied both numerically and experimentally. Results demonstrated that the ASLP had high system optical efficiency and good lighting performance with subrectangular radiation pattern, which meet requirements of road lighting. Extended source is a key issue challenging compact LED packaging freeform lens design. The size of high power LED chip is usually at a level of 1 mm × 1 mm while the distance between the chip and outside surface of the packaging lens is about 2.5 mm or even smaller. Since the distance between source and lens is less than 5 times the source diameter, the LED chip could not be regarded as a point source during packaging lens design according to the far field conditions of LED [9]. Thus the compact freeform lens should be designed based on an extended source. However, if we design a freeform lens according to the assumption of a point source while using the lens for an extended source, lighting performance will deteriorate significantly. Figure 2 (a) shows a freeform lens for LED tunnel lighting and its uniform rectangular radiation pattern when using a point source [8]. However, as shown in Fig. 2 (b), shape and uniformity of the radiation pattern deteriorate extremely when the source extending to an extended source with emitting area of 4 mm × 4 mm. Therefore, design method of freeform lens should be modified to improve lighting performance when using extended sources. Simultaneous multiple surfaces (SMS) method [4] is an effective way to deal with extended sources. The SMS method provides an optical system with two freeform surfaces that refract or reflect the rays of the input bundles into the rays of the corresponding output bundles and vice versa. The SMS method is mainly used in design of secondary optics so far. In this study we will present a practical design method of compact freeform lens for extended sources, which is quite suitable for designing freeform packaging lenses of new ASLPs. The design method includes three parts: establishing light energy mapping relationship between source and target, constructing lens and validating lens design by numerical simulation. Rectangular target plane is adopted as an example in the following design. Normally, refractive indexes of encapsulants and lens of LED packaging are usually different with each other. For example, refractive index is 1.586 for PC and is a range from 1.4 to 1.6 for silicone. It is hard to find an interface that will not deflect rays emitted from an extended source when rays transmit through the interface of two materials with different refractive indexes. In this method, optimization of overall lighting performance is to be achieved by adjusting optimization coefficients of target grids and reconstructing the outside surface of lens. Thus there is no strict restriction of the shape of lens’ inner surface and it is to be designed as inner concave spherical surface in this method. We will focus on the construction of the outside surface of lens in this study. Since the LED source and target plane both are of axial symmetry, only one quarter of them are to be considered in this discussion. First of all, the one quarter light energy distribution of source is divided into M × N grids with equal luminous flux. As shown in Fig. 3, the source’s intensity distribution Ω is specified by coordinates ( u, v ), where u is the angle between ray and X axis, and v is the angle between Z axis and the plane containing ray and X axis. The volume of Ω represents the total luminous flux Φ total of this one quarter source. Luminous flux of unit object d Ω could be expressed as Eq. ...
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The operation of light-emitting diode (LED) devices has identified a number of peculiar features of the angular distribution of light intensity. The use of several light-emitting diodes results in an unevenly bright light-emitting surface of a lighting device. When lighting devices operate under vibration conditions, certain circumstances may occur...
Citations
... Lens is an important part of optical system, widely used in optical imaging, information transmission, illumination detection and other fields [1][2][3][4][5][6][7] .Nowadays, the production of lenses mainly relies on single-point diamond cutting [8,9] , ultra-precision grinding [10] , injection molding [11,12] and other methods,however, these methods have high requirements for equipment and processes.In recent years, the rise of 3D printing technology has also made us see a new direction, using 3D printing technology, we can make almost any type of lens [13][14][15] .3D printing mainly includes digital light processing (DLP), stereophotolithography (SLA), two-photon polymerization (TPP), etc. DLP technology is the use of digital micro-mirror device DMD to reflect the light from the light source to the photopolymer material to achieve the effect of layer curing, but this processing method has obvious "ladder effect," often requires complex post-processing processes [16,17] .SLA technology uses a laser beam to illuminate the target range point by point, with the lifting platform in the vertical direction, to realize the processing of three-dimensional structures. ...
... The expression of the system free energy function E is as follows For the convenience of calculation, we define the function to be integrated in the free energy expression as the F function, that is When the system reaches stability, under the constraint of a fixed volume, the surface shape of the lens solution forms such that the free energy E of the system consists of two parts, the surface energy between the liquids and the effective gravitational potential energy, the last term represents the volume constraint, λ represents the Lagrange multiplier. When the whole system reaches a steady state, that is, when the energy of the whole system is the lowest, then the first derivative of the energy should be 0, that is (2)(3) We get the Euler-Lagrange equation (2)(3)(4) Where hr and hθ represent the first derivative of h with respect to r and θ, respectively. Dimensionless parameters are defined as follows ...
... The expression of the system free energy function E is as follows For the convenience of calculation, we define the function to be integrated in the free energy expression as the F function, that is When the system reaches stability, under the constraint of a fixed volume, the surface shape of the lens solution forms such that the free energy E of the system consists of two parts, the surface energy between the liquids and the effective gravitational potential energy, the last term represents the volume constraint, λ represents the Lagrange multiplier. When the whole system reaches a steady state, that is, when the energy of the whole system is the lowest, then the first derivative of the energy should be 0, that is (2)(3) We get the Euler-Lagrange equation (2)(3)(4) Where hr and hθ represent the first derivative of h with respect to r and θ, respectively. Dimensionless parameters are defined as follows ...
As an important optical component, lens is widely used in scientific inquiry and production. At present, lens manufacturing mainly relies on grinding, polishing and other methods. However, these methods often require expensive equipment and complex processes. This paper presents a method of injecting liquid material into the frame structure and curing it quickly. At the same time, based on the principle of energy minimization, we give a set of theory that can accurately predict the lens face shape, and give the simulation results by software. In this paper, 3D printing technology was used to produce different shapes of borders, which were used to produce free-form surface and spherical lens samples. By characterizing their surface contours and optical properties, the practicability of the method was verified. This method has the advantages of low cost, fast forming, high surface smoothness, and can theoretically prepare any size aperture lens, which has great potential for development.
... The light superposition of multiple LEDs makes part of the light irradiate outside the required area. Light in the outside area causes additional energy consumption and reduces illuminance [16][17]. During the curing process, the spill light can cause more skin on the back of the hand to darken. ...
For the problem of low light efficiency caused by divergent and uneven energy distribution of commercial port-able LED nail lamps, we propose an optical system composed of a Lambertian LED, a total internal reflection lens and a microlens array. According to the simulation results, the optical system can project a 130mm×70mm rectangular light pattern with a uniformity of 85.17% on a screen 70mm away. In addition, the optical utilized factor of the rectangular light pattern is 87.85%, and the optical efficiency of the entire optical system is 83.93%.
... In order to achieve the targeted lighting distribution with LEDs, the density distributions must be used with a secondary lens [13{17]. Wang et al. [18] mentioned the importance of using secondary optics in LED applications. The light distributions of the LED cannot directly meet the requirements of speci c applications; it has uneven light distribution curves. ...
Road luminaries are required to provide a certain quality of luminance that meets the standards and existing road characteristics. For this reason, the light from the light source should be directed in the desired conditions. Although a range of minimum average road surface luminance recommended for di erent classes of road is concurrently provided, the priority is to ensure that they are economical. In this study, a freeform lens and LED luminaire design with high luminous e cacy, 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, lens design was made by using optical and illumination design software. Furthermore, lens manufacturing and luminaire production were the result of the success of the design simulation test. The success of the Light Emitting Diod (LED) luminaire in meeting Commision Internationale de l' eclairage (CIE) standards in the designed road was evaluated. In addition, the advantages and disadvantages were determined in comparison to High Pressure Sodium (HPS) vapor lamps.
... However, it is not a simple task to redirect the light rays from an extended light source in a desired manner due to the fact that an infinite number of incoming rays should be controlled simultaneously at each point on the optical surface. There are three typical types of design methods for tailoring illumination lenses with extended light sources: the optimization-based methods [9][10][11][12][13], feedback design methods [14][15][16][17][18], and direct design methods [2,[19][20][21][22]. The purpose of illumination optimization is to generate the best possible illumination system by iteratively varying the variable values so as to minimize a merit function by which the optical performance of the illumination system is measured. ...
... Since the feedback design is similar to a local optimization, the result is also determined by the initial point. The direct design method [2,[19][20][21][22] has several advantages over the illumination optimization [9][10][11][12][13] and feedback design methods [14][15][16][17][18]. It only includes numerical computation without Monte Carlo ray tracing and cumbersome iterative irradiance/intensity compensation [1]. ...
A key challenge in tailoring compact and high-performance illumination lenses for extended non-Lambertian sources is to take both the étendue and the radiance distribution of an extended non-Lambertian source into account when redirecting the light rays from the source. We develop a direct method to tailor high-performance illumination lenses with prescribed irradiance properties for extended non-Lambertian sources. A relationship between the irradiance distribution on a given observation plane and the radiance distribution of the non-Lambertian source is established. Both edge rays and internal rays emanating from the extended light source are considered in the numerical calculation of lens profiles. Three examples are given to illustrate the effectiveness and characteristics of the proposed method. The results show that the proposed method can yield compact and high-performance illumination systems in both the near field and far field.
... used as commercial color converters [7][8][9][10] due to their high thermal and moisture stability. To date, great efforts have been made to improve the efficiency of phosphor-based converters. ...
... Jiexin Li, Zongtao Li, Jiayong Qiu, and Jiasheng Li* DOI: 10.1002/adom.202102201 used as commercial color converters [7][8][9][10] due to their high thermal and moisture stability. To date, great efforts have been made to improve the efficiency of phosphor-based converters. ...
Quantum dots (QDs) exhibit remarkable photoelectric performance. However, the conversion efficiency and thermal performance of QD converters so far is not satisfactory for high‐power solid‐state light (SSL) applications owing to the serious reabsorption loss of QDs and the poor thermal diffusion of polymer materials. Here, an efficient QD converter based on an anodic aluminum membrane (AAM), with high light enhancement and thermal diffusion, is introduced for high‐power SSL applications. Nanoporous AAMs are utilized as templates for confining the QD deposition into the nanowire (NW) shape by incorporating inkjet printing and vacuum‐deposition methods, forming vertical QD NW arrays. Compared with conventional converters, QD‐AAM yields nearly twofold photoluminescence intensity. Three‐dimensional finite‐difference (FDTD) simulations attribute the fluorescence‐enhancement mechanism to the enhancement of QD conversions and boosting of the waveguide effect in QD‐AAM. Furthermore, QD‐AAM exhibits excellent thermal diffusion performance under high‐power excitation, owing to the inner heat conduction path in the AAM framework. This study provides a practical and efficient strategy to comprehensively enhance the optical and thermal performance of QD converters for high‐power SSL applications.
... [1][2][3][4][5][6] With the rapid progress of technology, the highly efficient LEDs are becoming more affordable, which helps increasingly performance-and costcompetitive to other forms of traditional light sources. [7][8][9] Nonetheless, there are technological constraints to model LED illumination, in comparison with the conventional counterpart, owing to the inhomogeneous radiation distribution types of LEDs such as Lambertian, batwing and sideemitting patterns. [10][11][12] To that end, such LED sources are impractical for lighting in many contexts such as indoor lighting, automotive lighting, tunnel lighting and street lighting, where have most often required a uniform illumination. ...
... It is well known that the light distributor usually works on refraction or reflection principles, in several innovative fashions. 9,10,[13][14][15][16][17][18][19] Most design of the light distributor often has to implement for each individual element, thereby increasing the complexity in the manufacturing process. A mitigation of such complexity is to use the same identical optical element. ...
We introduce a compact lenslet array principle that takes advantage of freeform optics to deploy a light distributor, beneficial for highly efficient, inexpensive, low energy consumption light-emitting diode (LED) lighting system. We outline here a simple strategy for designing the freeform lens that makes use of an array of the identical plano-convex lenslet. The light is redistributed from such lenslet, hinging on the principle of optical path length conservation, and then delivered to the receiver plane. The superimposing of such illumination area from every lenslet occurs on the receiver plane, in which the non-uniform illumination area located in the boundary should have the same dimension as the size of the freeform lenslet array. Such an area, insofar, is negligible due to their small size, which is the crux of our design, representing a large departure from the former implementations. Based on simulations that assess light performance, the proposed design exhibited the compatibility for multiple radiation geometries and off-axis lighting without concern for the initial radiation pattern of the source. As simulated, the LED light source integrated with such proposed freeform lenslet array revealed high luminous efficiency and uniformity within the illumination area of interest were above 70% and 85%, respectively. Such novel design was then experimentally demonstrated to possess a uniformity of 75% at hand, which was close to the simulation results. Also, proposed indoor lighting was implemented in comparison with the commercial LED downlight and LED panel, whereby the energy consumption, number of luminaires and illumination performance were assessed to show the advantage of our simplified model.
... Much of the literature has further discussed the improvement of uniformity and efficiency of lighting [18][19][20][21][22]; the design method of freeform surfaces is also suitable for road lighting [23][24][25], and provides various calculation methods when designing rectangular beam patterns. Besides using freeform lens analysis for secondary optics design, it can also be applied on LED packaging [26], chromaticity space uniformity [27] and offer concrete improvement guidelines. ...
This study aims to develop a human-centric, intelligent lighting control system using adaptive LED lights in roadway lighting, integrated with an imaging luminance meter that uses an IoT sensor driver to detect the brightness of road surfaces. AI image data are collected for luminance and vehicle conditions analyses to adjust the output of the photometric curve. Type-A lenses are designed for R3 dry roads, while Type-B lenses are designed for W1 wet roads, to solve hazards caused by slippery roads, for optimizing safety and for visual clarity for road users. Data are collected for establishing formulae to optimize road lighting. First, the research uses zonal flux analysis to design secondary optical components of LED roadway lighting. Based on the distribution of LED lights and the target photometric curve, the freeform surface calculation model and formula are established, and control points of each curved surface are calculated using an iterative method. The reflection coefficient of a roadway is used to design optical lenses that take into account the illuminance and luminance uniformity to produce photometric curves accordingly. This system monitors roadway luminance in real time, which simulates drivers’ visual experiences and uses the ZigBee protocol to transmit control commands. This optimizes the output of light according to weather and produces quality roadway lighting, providing a safer driving environment.
... As reported by Brinksmeier et al. [4], MOS refers to an optical surface that has at least two layers of intentionally overlapped features. Due to their special surface features, the MOS can obtain higher optical efficiency while using fewer optical elements [5][6][7]. Therefore, the MOS can obtain the advantages of simplifying system structure, improving optical performance, expanding vision, and improving resolution [8]. ...
Multiscale optical surface (MOS) that contains non-rotational symmetry micro-features and large sag height macro-features is promising in optics, due to their special optical advantages. Diamond turning with the slow tool servo (STS) or fast tool servo (FTS) is widely used for fabricating optical surfaces. However, due to the limited dynamic performance of STS and the small stroke of FTS, applying STS or FTS alone cannot efficiently fabricate MOS. Therefore, in this paper, a hybrid tool servo (HTS) diamond turning technique was presented to efficiently produce MOS. By integrating characters of the high dynamic performance of FTS and long stroke of STS, the new technique fulfills the strict requirements of manufacturing MOS. Methods for generating tool path in CAD software and separating the tool path into STS path and FTS path based on its spectral features were proposed. Besides, tool path evaluations were conducted to predict the profile errors with considering the dynamic performance of STS and FTS, based on the suitable machining parameters selected. A machining experiment of a typical MOS was carried out using the proposed technique. Results showed that the MOS was efficiently fabricated with no tool interference mark on the fabricated surface and a maximum profile error of about 2.8 μm.
... Replacement of traditional incandescent lamps by light-emitting diodes (LEDs) has been progressing owing to the many advantages of LEDs such as high efficiency, eco-friendliness, and long lifetime [1][2][3][4][5][6][7][8]. For example, LED spotlights have been widely used in the residential, commercial, and industrial inspection fields [9][10][11][12][13][14][15][16]. Narrow-angle light distributions of the LED spotlights are suitable for accenting target areas with high light intensity or from a considerable distance. ...
Collimated illumination with a light-emitting diode (LED) is widely used in the residential, commercial, and industrial inspection fields. A slim LED illuminator composed of multi-parabolic surfaces to combine perpendicular collimated illuminations is proposed here. The multi-parabolic illuminator can produce a collimated rectangular illumination where light angle distributions for perpendicular axes can independently be controlled by different parabolic surfaces. This independence of the control makes the design of the illuminator simple. A prototype of the multi-parabolic illuminator is fabricated with an LED chip size of 3×3 mm and an opening aperture size of 20×60 mm. A maximum width of the prototype is 20 mm. The prototype demonstrates a production of a highly collimated rectangular illumination with half-intensity angles of about 7 degrees and 34 degrees for respective perpendicular axes.
... In recent years, freeform lenses are more likely to provide a new way to obtain the required LIDC through which a uniform illumination is achieved. [11][12][13][14][15][16] In this study, a computer simulation system is developed as an innovative design method for obtaining uniform irradiance with an array of LEDs. This method analyses the radiant intensity distribution of each LED and introduces the possibility of considering the inclination angles of the LEDs in the array related to the normal vector of the irradiated surface and the aperture angle of the radiant intensity pattern of the LED itself. ...
... Considering equation (14) in equation (11), we can obtain the function that describes the irradiance over the (x,y) plane, depicted in dark grey in Figure 2, caused by an LED centred in the (x 00 , y 00 , z 00 ) coordinates, but rotated by an angle with the (x, y, z) coordinates ...
Many applications in various fields require uniform illumination from light sources, for example, in medical imaging in the biophotonics area. In this work, the design and application of an annular light-emitting diode array capable of producing a homogeneous irradiance pattern is presented. As part of the design process, software that allows the simulation of the irradiance pattern as a function of the LED’s radiant intensity distribution, and the position and inclination angle of the LEDs, was developed and validated. Based on the simulation results, a source that produces homogeneous illumination over an area of 20 mm in diameter, where the lowest irradiance is more than 94% of the maximum irradiance, was constructed and tested in real conditions. The simulation method and theoretical calculations on which the array is based can be applied to the design of sources for other applications where a homogeneous irradiance is required.
