One-plate Interferometer And Fitting Wavefront

With the science and technology development in our country, many and many accurate tests are finished by optical wave interference or wave diffraction. The basic principle of wave interference is to form the feature of interference fringe by adding two wavefront to regard as the foundation of measurement. There are two familiar techniques of interference, one is of standard reference surface, but the other is of the same route. The classical shearing interferogram method is to be used the standard wavefront. But the interferometer method is dislike most ordinary Ways. The basic principle of lateral shearing interferometer is self-interference between the tested wavefront and the sheared wavefront, and from the method to evaluate the defect of the test wavefront. Its virtue lies in not the standard wavefront ,but interferogram itself. And most important thing is dislike most ordinary interferogram, the shearing inerferogram can not directly determine the shape of the tested wavefront, and the handing of the lateral shearing interferogram is relatively complicated, because it couldn't respond the wavefront information directly. Its fringe expresses that the average slope wavefront phase in the shearing widen range. So fitting the wavefront of the interferogram is the most difficult and important thing to the optical measurement. But there is no a perfect fitting way to resolve the difficulty heretofore. The basic principle of the lateral shearing interference just like the fig right side.In the interference region the wave will generate the lateral shearing. It can be expressed in another way that the fundamental of lateral shearing interference is that the beam with unknown wavefront is splitted into two same beams by a special beam splitter, and the two beams interfere in the overlapped region. According as the corresponding interferogram the feature of the unknown wavefront can be judged. In the thesis most of the methods of fitting the interference wavefront were analysised and a new way to resolve the interfergram was extracted. First step is to build the rectangular coordinate system on the interfergram, and record the abscissa of the experimenal point.. Fig2 is a interfergram. In fig2 W (x)is the original wavefront, W ( x? s) is the shearing wavefront,"s"is the spacing,the shearing direction is on x axle.Between W (x)and W ( x? s),the experimental point were presentated by W1 W 2 W3 ……W k. ?W (x) is the optical path difference.So ?W ( x)=W(x)?W(x?s),at x = s, ?W ( s)=W(s)?W(0),if we made W ( 0)=0, W ( s)= ?W(s),the same as x = 2s that ?W ( 2s)=W(s)?W(s), ?W ( 2s)=W(2s)+W(s)=?W(2s)+?W(s)This shows that if we can confirm the ?W (ks) of the experimental point on the interfergram and integrate,we can get the W (ks) well and truly.At last , we can descript the wave-path-difference curve by computer. The thesis based on the elementary theory of one-plate lateral shearing interferemeter, developed a whole system to fitting the interfergram automatically and exactly. Firstly, we build the plane rectangular coordinates on the interfergram, and the spacing direction overlapped with the x axis ,we confirm the experimental points along the x axis and note the horizontal ordinate of the points. Secondly, we make sure the order of the interference "p". Usually we confirm the lowest order P=1. Thirdly, we grouping the data of "x"and "p"of the points. Among the data we pick 2 or 3 auxiliary point to get the difference between the original orders and the practical orders, consequently get the...