| Headlamps are the 'eyes' of the car when they are driven at night. With the rapid development of automotive technology, headlamps have undergone remarkable changes. The process can be presented by replacement of its light source and advancement of lighting function. That is to say, the light sources develop from original acetylene gas lamp to today's headlamps. Meanwhile lighting function also develops from traditional fixed lighting to adaptive lighting. At present, the existing laser headlight can only generate fixed light patterns of distance light. Adaptive headlamps which equipped with Xenon lamp or LED can also generate the limited light patterns. Therefore, with the development trend of light source and lighting function, adaptive headlamps which equipped with laser will lead the trend in automobile headlamps' area. In this paper, the realization of adaptive light patterns is set as our goal, and we design the optical system based on adaptive laser headlight. The design idea and the detailed design scheme of laser beam homogenized and combined integer as well as the output of adaptive light patterns are presented in this paper. And part of the design results are verified by simulation. Besides, laser beam homogenized and combined integer are the main content of this paper. The main work of this paper is as follows.Generation of the adaptive light patterns was the design goal of this headlamp system, the light patterns were partitioned according to AFS light standard and the features of 4 basic lighting mode, 4 kinds of light pattern were designed in this paper. To achieve the output goal of adaptive light pattern, the digital lighting process technology was chosen to realize the spatial light modulation, and the optical system was designed according to luminous flux, color light distribution index of the headlight application. The overall optical system consists of two parts: laser beam homogenized and combined as well as the output of adaptive light patterns. The former aims to transform the three-color laser beam to uniform rectangular light spot which has the same size as the display chip. Compared to the traditional laser beam combined and homogenized structure, double fly-eye lens beam combined and homogenized structure were proposed in this paper, discrete multi-beam laser beam was homogenized and combined, and the uniform rectangular white light spot was obtained at the focal plane or anywhere in the back of the focal plane. This structure also can be applied to generate high power white light beam based on laser, detailed theoretical analysis and simulation analysis were discussed in this paper. Then the rectangular beam was pixelated in the second part of the optical system, the image of adaptive light pattern was obtained by controlling the brightness of each pixel, and the image was projected to light screen by projection lens. Anamorphic lens were applied in this system, which can carry out longitudinal compression of the picture and achieve the conversion of the size ratio. Besides, the loss of light energy was reduced by anamorphic lens. The parameters of the overall optical system were designed according to principle of conservation of etendue, and the simulation model defined by theory of parameters was set up and ray-tracing was also conducted in this paper. The uniformity of rectangular lighting spot was 93.8%, and overall energy efficiency was 80.3%. Moreover, the optical path of laser beam homogenized and combined integer was set up, and the simulation of experimental parameters was done before experiment. The energy efficiency in the simulation and experiment was 52.3% and 45% respectively. Finally, the projection display chip was added on basis of the laser beam shaping optical path, and different outputs of adaptive light patterns were realized by the chip. The experimental results were consistent with the theoretical design. |
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