Based on the free surface and Fresnel lens LED cars fog lamp design - (AddTime ： 2013-01-23)

LED is a new generation of competitive new solid light source, with high efficiency, light color pure, low energy consumption, long service life, reliable and durable, no pollution, control agile, fast response, small size, impact resistant etc [1]. Due to the LED chip output light with lambert distribution, if not properly handled and the distribution of light to be applied directly in the automotive lighting system will be unable to reach the standard required. So need to the 200W led Flood light source for lighting system for secondary optical design, the design results directly affect the lighting system of luminous efficiency, energy consumption, and the safety performance of the car (2-4].

Now automotive lighting technology is developing very fast. With the rapid development of automobile industry and the keen competition of the market, the modern automotive lighting system for luminous efficiency, safety performance, as well as the requirements of the beautiful more and more is also high. Automotive lighting of the free surface mirror and 200W led floodlighting system design and processing is very important. Different from the traditional optical system design. Automotive lighting system of nonimaging optics design is a multidisciplinary and complicated process [5]. And the traditional parabolic mirror and with the combination of light lens, compared to the free surface and Fresnel principle combined with lens can also achieve convergence and light distribution function, so the fog lamp will save use space and reduce the cost of installation. Free surface after design makes the fog lamps become more agility and compact.

So far, the LED is mainly applied in such as brake lamp, in light, turn light, such as back-up light car signal system. At present, the LED headlamps are not large scale application is an important factor is cooling, and car LED front fog lamps for the energy needed to relative headlamps to less, the LED is less, and with the corresponding single LED efficiency continuously improve, the waste heat to reduce, the constraint car LED headlamps technical bottleneck in the car after LED fog lamps can be easily solved, so after car LED fog lamps research has great value in use.

After the design of the fog

200W led Flood light source choice

After the car foglight refers to in the fog, snow, rain or dust diffuse and nuisance visibility, in order to make the other road users easy to find, installed in the vehicle tail, photometric than a light after more strong red light [6], in car security plays an important role in. On the motor vehicle at home and abroad after all has the strict standard fog lamps, but haven't about semiconductor lighting standards (7-8]. This design based on the traditional tungsten lamp after LED fog lamps and halogen lamp general requirements as specified in the standard GB 11554 -, - after the light source of fog light red. In light with the biggest difficulty is: to ensure the diamond area light intensity in a certain interval requirements. In order to be able to get very good design effect, this design choose OSRAM (OSRAM) company's one small power red light LED, its high luminous efficiency and very small, light Angle for 120 °, in 700 mA work down the electric light, typical values for 10 lm, the light intensity distribution as shown in figure 1 [9].

Design principle
The Fresnel lens continuous surface part "slump" to a plane. Look from section, the surface by a series of zigzag grooves composition, the center part is elliptic curve. Each groove with adjacent groove Angle between different, but will be concentrated light one place, form the center focus, also is the focus of the lens. Each groove can be regard as an independent small lens, the light adjustment into parallel light or condenser. And this paper USES is a light will be LED into parallel light. As shown in figure 2 left and right, a 200W led Flood light source in the lens axis F point of light, which reach the Fresnel lens and surface. Here we select o, n two beam as the research object, they respectively by o, A after refraction through lens o 'and B in the form of parallel light injection [10].

According to the law of refraction:
(1) Type (1) N1 for air index approximately equal 1, N2 for lens material index, θ 1, θ 2 respectively is lens bevel Angle and the Angle of refraction. The figure 2 available: θ 1 = θ 2 +, θ 2 = α n (2)