高灵敏度分束干涉型 LCD 盒间隙厚度测量仪

High Sensitive Split beam Interferometric LCD Cell Gap Meter

本文报道一种高灵敏度分束干涉型ＬＣＤ盒间隙厚度测量仪（以下简称测厚仪），并重点介绍其两项关键技术：干涉条纹级次的彩色识别法和光楔干涉定标法。要精确测量液晶盒间隙厚度，必须准确测定基准和测量这两组干涉条纹间的距离，因而必须准确识别干涉条纹的级次。强度识别法的测量精度易受随机噪声的影响。本文提出条纹级次的彩色识别法，利用这种方法，测量精度可以大幅度提高。定标是测厚仪的另一关键技术。本文提出独特的光楔干涉定标法。文中给出了光楔干涉法定标精度的理论估算。

A high sensitive split beam interferometric LCD cell gap meter is presented,especially,its two key technologies,color method of determination of the fring order and the optical wedge interferometric method of calibration,are described. Basically,there are two interferometric methods to measure the cell gap of the liquid crystal display(LCD),and one of them is the split beam interferometric method.Each beam reflected from the substrate to LC(or LC to substarate)interface is split into two beams(propagating in two different directions)by a Wollaston prism.The beams generate two groups,stantionary and test,of interference fringes,and the separation between the two groups of interference frings is correlated with the cell gap.To measure the liquid crystal display cell gap accurately by using the split beam interferometric method,correct determination of the inteference fringe order is necessary.One well known method is so called intensity method in which the brightest fringe is determined as the zero order of the interference patern.Using this method,the measurement accuracy may be affected by random noise.A precise method,i.e.color method in which the fringe order is determined according to its color is presented.It is easy to get much better measurement accuracy by using the new method. Calibration is another key technology of the LCD cell gap meter.Unique optical wedge interferometric method of calibration is presented.The calibration uncertainty by optical wedege interferometric method is theoretically estimated,and a optical wedge has been fabricated and used in practical calibration of the high accuracy liquid cyrstal display cell gap meter.The results demonstrate that the optical wedge interferometric method of calibration is sufficiently accurate,quick,cheep,simple,and so,it is effective and useful for production monitoring of thickness and uniformity of liquid crystal displays.