| As the car evolves into a human-centric living space,the interaction between the car and the driver is no longer limited to simple driving status interaction,but has gradually expanded to such aspects as intelligent driving and infotainment.In this context,the Head-Up Display(HUD)has been developed to directly project information such as driving status,navigation and assisted driving in front of the driver’s eyes,so that the driver can intuitively feel the driving status and other information without having to switch their vision,which reduces the blind driving time to a large extent and improving driving safety.Today,there are two main types of HUD that exist on the market,namely,windscreen-type HUDs(WHUD)and augmented reality-type HUDs(AR-HUD).However,the current in-vehicle HUDs involved can only display a virtual image surface at a single projection distance.When the driver changes the speed of the vehicle for observation,he needs to adjust the visual focus to fit the projection distance of the HUD,But highly frequent adjustments for a long time will lead to eye fatigue.To address this situation,this paper carries out the design of an in-vehicle dual-optical path flat vision optical system,with the following research:Firstly,the research background and development history of HUD are introduced,and the research at home and abroad on HUD technology is summarised and four different projection display technologies are compared.The principle of in-vehicle HUD imaging and the main components of the optical system are studied,and the optimal initial architecture is selected for the imaging characteristics of the dual optical path flat vision optical system.The main optical parameters of the optical system are presented and the steps of the optical system design are explained.Secondly,the design specification of the dual optical path flat vision optical system is proposed.Based on the front windscreen of a car provided by a vehicle manufacturer in the market,the optical system architecture is built with the help of ZEMAX.And the off-axis reflective dual optical path flat vision optical system is designed and optimised by changing the object distance of the optical path,hence realising a dual focal plane projection display.The optimized optical system was evaluated in terms of point column diagram,grid distortion,MTF curve,dynamic parallax,image simulation,etc.The image quality of the optimised optical system was evaluated in terms of point column diagram,grid aberration,MTF curve,dynamic parallax and image simulation.Thirdly,the dust film was drawn in CATIA and the light damage simulation analysis was carried out by Trace Pro.The theoretical analysis of wedge angle elimination of ghosting was modelled in ZEMAX and the internal wedge angle of the car front windscreen in a dual optical path flat vision optical system was calculated to be 0.401 mrad.The simulation analysis was then carried out in Trace Pro for solar inversion and other stray light.Fourthly,the tolerance range of each optical component assembly parameter was set in ZEMAX for the optimised two-optical path flat-view optical system,and 1000 Monte Carlo samples were randomly selected for preliminary analysis.The statistics show that over 90% of MTF in this optical system is greater than 0.63 at a spatial cut-off frequency of 4.421p/ mm,verifying the tolerance range for the actual production and assembly process.Finally,a rough verification of the machined prototype was carried out by means of a test rig. |
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