A silicon-based dual-LED packaging module with a three-dimension freeform lens for square illumination

Road lighting can benefit strongly from LEDs and freeform lenses. However, freeform lenses design for road lighting applications is complicated and difficult when balancing energy efficiency and lighting quality. In addition, the asymmetric properties of the required light distributions and non-neglectable sizes of LEDs make the design more challenging. Currently, we prefer an efficient design strategy with two steps: light distribution optimization and freeform lens construction. In the first step, we employ a modified polynomial representation of the illuminance distribution and perform constrained optimization. In the second step, we construct the freeform lens with double freeform surfaces to realize the optimized light distribution using the ray mapping method associated with over compensation.

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.

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.

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.

Spectacle lenses performance is simulated based on the eye model system. The modulation transfer function (MTF) curve of spherical lens, aspheric lens and optimized lens is analyzed, and the results are compared and analyzed non-curved lenses were found to be more effective in improving image quality. For free-form lenses, we measured the far-field, progressive corridor and near-field in the simulated optical system, and studied the relationship between the face matching angle and the tilt of the endoscope and the MTF of the conventional spectacle lens and the free-form lens. The experimental results show that when the face fitting angle and the inclination of the endoscope inclination increase, the MTF decreases and the imaging quality deteriorates. The tilt of the endoscope has the greatest influence on the MTF value, followed by the face fitting angle, where the influence of the spatial frequency is negligible, but as the spatial frequency increases, the MTF also decreases. Therefore, for the free-form surface, when the face fitting angle and the inclination of the endoscope are different, the image quality is easily affected, so these two factors must be fully considered in the design.

Structured light vision fails to detect the high-temperature objects up to 1700 °C because the projected light patterns are drowned by the strong self-emitted radiation of the high-temperature objects. For this problem, signal enhancement and extraction of the projected laser light patterns are carried out in this paper. Signal enhancement consists of two steps. The first step involves physical enhancement of the laser light signal by spectrum selective of the laser light source and filtering of the radiation by the optical filter. Theoretical analysis finds that, the working wavelength of the laser light source should be short, and the pass-band width and the transmittance in the stop band of the optical filter should be small. The second step involves modulation of the projected light patterns. A novel modulation method is derived mathematically with optimal solutions. Based on the modulation method, strong radiations of the high-temperature objects are transformed into radiation noise with zero mean while half of the intensities of the structured light patterns are preserved. Interfered with the radiation noise, signal distribution of the structured light patterns is uncoupled from that of the radiation noise to extract the structured light patterns with desired confidence. The signal enhancement and extraction methods are applied and validated for slag level measurement in the converter in the steelmaking industry.

A free-form lens (FFL) is a special surface that is difficult to be fabricated. FFL are usually fabricated by computer-controlled optical surfacing (CCOS) technique. During CCOS, the material removal amount is determined by the unit removal function (URF) convoluting with the input data――the dwell time. When the removal amount and the URF are known, how to solve the input data involves the special algorithm――deconvolution. Usually, the input data are solved by virtue of low pass filter or iterative methods. However, an approximation solution would destroy the machining stability necessary to perform pre-cisely CCOS. In this paper, to solve the input data, a new method that is based on the finite Fourier coefficient is put forward. It can give a continuous and accurate solution for fabricating choice. Several parameters are simulated, which influence the process of CCOS, and evaluating on the effect of the method is also carried out. Experimental results verify that this method is suitable for guiding the manufacturing of high precision FFL.

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.

Design of double freeform-surface lens for LED uniform illumination with minimum Fresnel losses

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.

This study details a one-time ray-tracing optimization method for the optimization of LED illumination systems [S.-C. Chu and H.-L. Yang, "One-time ray-tracing method for the optimization of illumination system," in Proceedings of International Conference on Optics in Precision Engineering and Nanotechnology (icOPEN, 2013), 87692M]. This method optimizes the performance of illumination systems by modifying the light source's radiant intensity distribution with a freeform lens, instead of modifying the illumination system structure. Because illumination system structures are unchanged in the design process, a designer can avoid the common problems faced when designing illumination systems, i.e., the repeated and time-consuming ray-tracing process when optimizing the illumination system parameters. The easy approaches of the proposed optimization method to sample the target illumination areas and to divide the light source radiant intensity distribution make the proposed method can be applied to both direct-lit and non-direct-lit illumination systems. To demonstrate the proposed method, this study designs an illuminator for a tube photo-bioreactor using the proposed one-time ray-tracing method. A comparison shows that in the designing of the photo-bioreactor, tracing all rays one time requires about 13 hours, while optimizing the light source's radiant intensity distribution requires only about twenty minutes. The considerable reduction in the ray-tracing time shows that the proposed method is a fast and effective way to design illumination systems.

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.

The algorithms presented in this paper are focused on the analysis of 3D scene using structured light technique. The light pattern which was projected on the scene consisted of horizontal stripes of different colors. These colors corresponded to the symbols creating the de Bruijn sequence. The first plane objects of analysed 3D scene were human hands. In this paper the discussion concerning important features of the structured light pattern is made. The focus is made on the analysis of the pattern corresponding to the de Bruijn sequence. The algorithm for computing the depth map of 3D scene using triangulation method is proposed. The most important part of the algorithm for the depth map evaluation is related with the extraction of colors from the stripes of the projected light pattern. The discussion concerning proposed algorithms for color detection is made and the results of the tests on HD images are described. The implementation of proposed methods using parallel programming with openCL architecture enabled crating real-time application.

Compared with traditional optical surfaces, freeform surfaces provide much more degrees of freedom to tailor the irradiance distributions of light sources, forming previously unimaginable illumination optical systems. However, the complexity of freeform surfaces presents a huge challenge to the design process, especially when the light source size is assignable. We achieved fast irradiance evaluation of freeform illumination lens based on deep learning methods, preparing for a rapid optimization for the lens design. These learned simulation results are similar to those of LightTools, while the computation time is greatly reduced. The representation of freeform surfaces, the generation of datasets, and the selection of neural network structures are introduced in this paper. In the future, we will further improve the neural network performance and use the back-propagation of the neural network to realize a rapid optimization of the freeform lens.