An Analysis of LED Light Distribution Based on Visual Spectral Characteristics Procedia Engineering 15 (2011) 5111 – 5115 1877-7058 © 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.08.948 Available online at www.sciencedirect.com Available online at www.sciencedirect.com Procedia Engineering Procedia Engineering 00 (2011) 000–000 www.elsevier.com/locate/procedia Advanced in Control Engineering and Information Science An Analysis of LED Light Distribution Based on Visual Spectral Characteristics XU Xiaobing,XU Huamei,WANG Jianping,ZHU chenghui,XIE Yunlin a* School of Electrical Engineering and Automation, Hefei University of Technology,230009,Hefei,China Abstract On the analysis of the human visual structure characteristics and LED optical design principle, human visual color image model with background light was constructed in this paper, and the image sharpness function is defined. With high pressure sodium lamps, white light and green light LED as backlight, the model simulation of image sharpness is fulfilled. The results show that the green LED has better clarity and sensitivity with the same condition of radiation energy background light. . © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of [CEIS 2011] Keywords: human visual characteristics; green LED; visual model of color images 1. Introduction Since the seventies there has been the world's energy crisis, countries have to take corresponding measures and actively develop new energy sources, do everything possible to conserve existing energy [1]. Reflects the green light is the core of energy efficient lighting, reasonable to select the correct power source is the key to achieving the green light [2].LED (Light Emitting Diode, LED) is a new and efficient solid light source. Its emergence is recognized as the most promising in the 21st century one of the areas of high technology [3]. LED lighting in a variety of more and more people's attention, especially in the development of high-power high-brightness LED lighting has become the development trend of new * Corresponding author .Tel.: +13956948800. E-mail address:weahhf@126.com Open access under CC BY-NC-ND license. Open access under CC BY-NC-ND license. http://creativecommons.org/licenses/by-nc-nd/3.0/ http://creativecommons.org/licenses/by-nc-nd/3.0/ 5112 XU Xiaobing et al. / Procedia Engineering 15 (2011) 5111 – 51152 XU Xiaobing et al./ Procedia Engineering 00 (2011) 000–000 generation of civil [4]. In China, the road currently used mainly high pressure sodium light sources, but the light blue-green light color shade component composition containing less sensitive areas outside of the human eye at night in front of the driver is not easy Panduan cars, pedestrians, obstacles, etc. distance, high incidence of traffic accidents [5]. Many researchers state in the mesopic vision of high pressure sodium, metal halide light, as the efficiency of the study, achieved many result [6]. But in research new LED optical characteristics is inadequate, in this paper analyzes the structural characteristics of human visual design of a consistent feature of human vision LED lighting, the green LED lighting, so that the lamp with the light color components the proportion of green light more, and the distribution of sensitive areas in the human eye, to make up for the lack of yellow high-pressure sodium lamp, the light and colors of light through this model, experimental simulation, obtained better results. 2. The visual structure of the human eye The structure of the human eye, including: cornea, iris, lens, ofitreous, retina and adtic nerve. The retina is the visual optical and electrical physiological processes during the interface. It divided into cone cells and rod cells. the former well under the conditions specified in the visual detail and color resolution, while the latter has higher sensitivity can feel a very faint light, but can not distinguish the details and colors, the main In the case of dark play. Pyramidal cells in the human eye work, the brightness level of 10cd / ㎡ above vision is called photopic vision. Rodshaped cells work in the human eye, the brightness level 0.003cd / ㎡. Between photopic and scotopic vision are called mesopic vision. 3. Green LED's light color design principles Green LED light color design in the mesopic vision range, the human eye cone cells and rod cells are simultaneously and the spectral wavelengths of light in different colors depending on the efficiency of different sensitivities. Scotopic vision and photopic vision of the spectrum of light are as the efficiency curve v '(λ) and v (λ) are determined the in CIE 1951 and 1924, respectively as shown in Fig.1 (a): Fig.1. (a) two visual spectral efficiency of light as light as the performance; (b) cones in the human eye's sensitivity to a variety of different color curves. As shown in fig.1(a), in the photopic visual conditions, the human eye is most sensitive to 555nm wavelength green light and lumineous efficiency of 683lm / W; but with the lower level of the human eye adapt to light and shade, color, space and response features as the feelings have to change, the human eye fovea and the edge detection becomes as easy as some of the perceived, and color perception gradually weakened, while the human eye will make the most sensitive optical wavelength from the Min 555nm of the green vision when the maximum efficiency, and gradually change to scotopic vision of the 507nm the 5113XU Xiaobing et al. / Procedia Engineering 15 (2011) 5111 – 5115XU Xiaobing et al./ Procedia Engineering 00 (2011) 000–000 3 most efficient. So according to this characteristic, if the light source of the radiation spectrum of content and blue-green shade, you can make much more eye pupil contraction, it will have a better visual effect. 3.1. Model of human visual analysis of color images Pyramidal cells in the human eye to various different colors of light relative sensitivity curve shown in Fig.1 (b): It reflects the energy equivalent to the human eye to different wavelengths of light relative visual sensitivity. Reference [10] Table 4 provides the data for intermediate vision research, the use of least squares data fitting, you can get the middle of the visual spectrum of light as the performance curve shown in Fig. 2: Fig.2. spectrum of luminous efficiency It reflects a certain brightness level and the wavelength of light depending on the relationship between performance. Eye on the overall strength of the feelings of colored light can be sensitive to each color intensity of the visual cells integrated into a synthesis of the impulse to pass into the brain, and then produced a color image. The visual model of color image shown in Fig.3: Fig.3. visual model of color image The function of this model to simulate the human eye for color images to achieve the process of perception, according to the input of different R, G, B values, the human eye can see different colors and brightness of the color image, R, G, B expression is as follows: ( ) ( ) λλλ drSR m∫ Κ= 780 380 G (1) ( ) ( ) λλλ dgSm∫ Κ= 780 380 ( ) ( ) λλλ dbSB m∫ Κ= 780 380 ( ) According to the literature [9] as the performance of the mescopic vision, combined with visual selection between the scope of this article, values for the 1190 lm / W; mΚ λS is the mesopic vision spectrum of light as the effectiveness of distribution; ( )λr , ( )λg ( )λb, represent the red, green, and blue sensitivity of cells to different wavelengths. Perception of color images is as follows: 1) chromatic adaptation transform 2） non-linear compression 3） color separation 5114 XU Xiaobing et al. / Procedia Engineering 15 (2011) 5111 – 51154 XU Xiaobing et al./ Procedia Engineering 00 (2011) 000–000 ( ) iik Ek 4） spatial filter processing Filter selected the following equation: ∑=Η ωξξ 2,1 (2) Where ( )[ ]22221 /exp iii kE σξξ +−= , κ is the coefficient of factor accumulation and to make the filter1,the coefficient factor is accumulation to 1. ParametersiE iσ and iω are used to change the size of the filter. 5） color image output. 3.2. The definition of image resolution In recent years, researchers through the ambiguity and noise on the clarity of the definition [9], this image based on this model output resolution is defined as follows: 23121 BXBXYXD ++= 3x (3) D: image clarity, the greater the value is the clearer of image. Y: the image brightness, the range of 0.1 ~ 3cd / ㎡ . B1, B2: represent the red-green and yellow-blue contrast, in the range between 0-1. , , : respectively coefficient and . 1x 2x 1321 =++ xxx 4. Simulation examples 4.1. Simulation model selection 1） the background radiation in the same energy , model A and B parameters are chosen as follows: ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ −= 117.1066.0000.0 175.0724.0127.0 114.0587.0299.0 A ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ − −= 27.60.027.6 00.00.410.41 00.00.05.21 B 2） spatial filter parameters are as the following table: Table1 spatial filter parameter channel iω iσ Black and White 0.049 10.60 0.025 2.356 - 0.805 0.076 Red and Green 0.039 7.738 0.29 0.642 Yellow and Blue 0.048 5.761 0.255 0.8216 5115XU Xiaobing et al. / Procedia Engineering 15 (2011) 5111 – 5115XU Xiaobing et al./ Procedia Engineering 00 (2011) 000–000 5 4.2. Analysis of simulation results Table2 experimental results channel HPS LED White light LED Green light Y 0.95 2.64 2.98 B1 0.32 0.75 0.89 B2 0.81 0.56 0.55 D（Definition） 0.621 1.487 1.692 We carried it through the software Matlab7.1simulated results are as follows: Fig.4. (a) original image; (b) LED green light; (c) HPS; (d) LED White light. 5. Conclusion Based on the analysis of the structure in human vision and sensitivity, the different wavelength is different from the design of a green LED lighting. Through modeling is simulation of the high-pressure sodium lamp, yellow and white LED, green LED. Then carried out by Matlab7.1 simulation of light and color, from the comparative analysis of the results obtained the green LED at the same level of brightness, the clarity is better than high pressure sodium lamp and white LED, it is more suitable for road lighting can achieve the best results. References [1] Bing Treekui, Jie Gao. LED lighting engineering [J]. 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