| Anti-vibration interferometer solves the problem of the environment influence to phase-shifting interferometry effectively. The low-coherent light source is usually needed in the interferometer. A practical method is studied to exam the coherence of the light source for the anti-vibration interferometer.Some algorithm simulations are researched before the experiments in order to acquire the precise parameters during the experiment, for example sample interval, sample length and so on. The spectrums of LED are measured by the Michelson interferometer and grating monochromator. The experiment results are compared and the accuracies are analysed, the method of measuring the homogeneity of optical glass with parallel surfaces using LED is introduced. The spectrum of sodium lamp is measured on Twyman interferometer, then the precise structure is calculated.The relationship between operation mode of LD and coherence is discussed. The coherent change of semiconductor laser is observed basing on the experiment system of Michelson interferometer during the process of altering the temperature, electrical current or modulation frequency, then the changes of spectrum mode spacing, relative intensity and width are calculated. It is proved that high frequency modulating the input electrical current is used to change the coherence of the laser availably. The coherence data of light source can be acquired by dint of the methods mentioned in the paper.The modulated LD is applied into the anti-vibration interferometer, then four 4-bucket phase-shifting interferograms, the wrapped phase map and retrieved wavefront are acquired, in order to realize the simultaneous phase-shifting anti-vibration interferometry. |
