Application of knife-edge technique to measurement of spatial structure of focusing spot

An investigation and analysis of two methods, the multi-angle knife-edge method and the right-angle double-knife-edge method, was demonstrated for the light distribution measurement. The basic principles of the two methods were introduced. Their ability of image reconstruction and anti-noise was analyzed by numerical simulation. The experimental result of the spot measurement with the right-angle double-knife-edge method was showed. As a conclusion, compared with the multi-angle scanning knife-edge method, the double-knife-edge method was more practical for focal spot measurement, especially for the tightly focusing spot.