汽车贴膜上出现彩色条纹的机理研究  

STUDY ON THE MECHANISM OF COLOR STRIPES ON AUTOMOBILE FILM

作　　者：刘子健 高新红[1] 王福合[1] LIU Zijian;GAO Xinhong;WANG Fuhe(Center of Physics Experiment Teaching, Department of Physics, Capital Normal University, Beijing 100048)

机构地区：[1]首都师范大学物理系物理实验教学中心,北京100048

出　　处：《物理与工程》2020年第3期103-108,共6页Physics and Engineering

摘　　要：当戴上偏光眼镜看贴有车膜的汽车前挡风玻璃时会看到一系列彩色条纹,通过理论分析和实验验证,发现汽车贴膜能够产生彩色条纹的原因类似于正交偏振光路中各向异性晶体所产生的消光干涉。在车内观察时,自然光以近似布儒斯特角入射到前挡风玻璃后透射出的光为部分偏振光,此时前挡风玻璃相当于起偏器;车膜就是具有双折射特性的各向异性晶体,部分偏振光通过车膜后形成振动方向相互垂直的o光和e光;偏光眼镜相当于检偏器,o光和e光在检偏器透振方向上的分量相互干涉,当光程差为半个波长的奇数倍时形成与该波长相对应颜色的干涉亮条纹。由于太阳光为复色光,所以随着入射角的变化会产生一系列的彩色等倾干涉圆环。在车外观察时,与在车内观察时类似,主要区别是在贴膜与空气的界面处o光和e光发生反射后再先后通过贴膜和前挡风玻璃返回到车前方,这时用偏光眼镜观察时即可看到彩色干涉条纹。有时如果观察角度和位置合适时,即使不佩戴偏光眼镜也能看到较浅的彩色条纹,这主要是因为光2次通过前挡风玻璃,此时的前挡风玻璃既是起偏镜,又是检偏镜。When wearing polarized glasses and looking at the front windshield of the car with a film,you will see a series of color stripes.Through theoretical analysis and experimental verification,it is found that the reason of color fringes produced by automobile film is similar to the extinction interference produced by anisotropic crystals in orthogonal polarized light path.When viewed in the car,the natural light is partially polarized when it is incident on the front windshield at Brewster angle approximately.At this time,the front windshield is equivalent to a polarizer.The film is the anisotropic crystal with birefringence.The partially polarized light is decomposed into ordinary(o)and extraordinary(e)light with mutually perpendicular vibration directions when it passes through the film.The polarized glasses are equivalent to analyzers.The components of o and e lights in the direction of vibration of the analyzer interfere with each other.When the optical path difference is an odd multiple of half a wavelength,a bright interference fringe of a color corresponding to the wavelength is formed.Since the sunlight is a complex color light,a series of color isoclinic interference rings are generated as the incident angle changes.When viewed outside the car,it is similar to that observed in the car.The main difference is that the o and e lights are reflected at the interface between the film and the air,and then returned to the front of the car through the film and the front windshield.At this time,color interference fringes can be seen when observing with polarized glasses.Sometimes,you can see lighter color stripes even if you don't wear polarized glasses,if the angle and position are appropriate.This is mainly because the light passes through the front windshield twice.The front windshield at this time is both a polarizer and an analyzer.

关 键 词：彩色干涉条纹 偏振 双折射 布儒斯特角 

分 类 号：O43[机械工程—光学工程]