New algorithm of knife-edge method measuring the size of hat spot and Gaussian spot

In order to measure the radius of hat spots and Gaussian spots,knife-edge method was adopted for the theoretical analysis and experimental verification.A new iterative algorithm was proposed.The distance of knife-edge is in direct proportion to the radius of spot.The corresponding scale factors were calculated.It is convenient to obtain the radius of spots by multiplying a corresponding scale factor to the distance of knife-edge.The result shows this iterative algorithm is also valid for any spot whose distribution of intensity is already known.