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汽车上的车灯是光学原理的一种常见应用,每辆汽车上至少有两只大灯(又称头灯)、两只小灯、一只后灯和制动信号灯。大灯用来照明道路,它由灯泡、反光镜和散光玻璃三部分组成,灯光做成双灯丝,一根为远光灯丝,功率较大位于反射镜的焦点上,通过反射镜形成平行光束,当汽车在郊行外驶对面无来光时,接入远光灯丝,使大灯照射远方。另一根为近光灯丝功率较小,位于反射镜焦点的上方或前方,当两车相遇时,通过变光开关接入近光灯丝可使光束倾向地面,从而避免迎面开车的驾驶员眩目,保证行车安全。灯光的光度不大,一般只有50～60烛光,在这种光度下如没有反射镜只能照明车前6米的距离,反射镜呈旋转抛物面内表面镀银或铬,它可将灯光发出的光线聚合成平行光束并使光度增大到几百倍,但反射镜射出的光束太窄,照明范围不大,为了增大散光程度还需采用散光玻璃,散光玻璃其上有皱纹和棱,从光学角度来看它是许多透镜和棱镜的组合体,光线通过这些棱镜和透镜时,使一部分光线折射而发散到车前的两侧和路面上去。由于反光镜和散光玻璃的作用,可使大灯均匀照亮车前100米之内的任何障碍物。
Car lights on the car is a common application of optical principles, each car has at least two headlights (also known as headlights), two small lights, a rear light and brake lights. Headlamps used to illuminate the road, which consists of light bulbs, mirrors and astigmatism glass three parts, the lights made of double filaments, one for the high beam filament, the power is larger in the focus of the mirror, through the mirror to form a parallel beam, When the car outside the suburbs outside without light, access to high-beam filament, so that the headlights shine afar. The other is a low-power filament light power, located above or in front of the mirror focus, when the two cars meet, access to low-beam filament through the dimmer switch beam can be inclined to the ground, so as to avoid driving dazzling head driver , To ensure traffic safety. Light luminosity is not, usually only 50 to 60 candle light, in this luminosity, if there is no reflector can only illuminate the distance of 6 meters, the mirror is rotating paraboloid inner surface of silver or chrome, it can be issued by the light Light rays converge into a parallel light beam and increase the light intensity to hundreds of times, but the light beam emitted by the reflector is too narrow and the illumination range is not large. In order to increase the degree of astigmatism, astigmatism glass needs to be used, and astigmatism glass has wrinkles and ribs thereon Optical point of view it is a combination of many lenses and prisms, light through these prisms and lenses, part of the light refraction and divergence to the car on both sides of the road and up. Due to the effect of the reflector and astigmatism glass, the headlights can be illuminated evenly to any obstacle within 100 meters of the vehicle.