This paper deducted the principle of Talbot effect and the conditions of self-imaging byusing several optical theories and analyzed at different angles its physical idems

It also discussed the method of measuring the collimation of large beams based on Talbot effect andmoire techmology

made further research on the accuracy of the above methods and intro-duced the other applications of that method.In addition

the above mentioned principle hasbeen applied to make testing of collimation for the two large-scal collimators. The accuracy offocus-adjustment can exceed half of focus-depth and the accuracy of collimation can exceed 10

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rad.The result of the experiment absolutey complied to the theoretical calculation anddesignation. This method has not only a high degree of accuracy but also a simple structureand can achieve easy instrumentation that can be adopted to test the multiple optical andphysical parameters. It has extensive practical values.