Comparison between edge tracing and slit tracing in the measurement of the OTF

A study was performed to compare two methods of measuring the Optical Transfer Function (OTF), namely edge tracing and slit tracing, to evaluate the performances and limitations of each method. Edge tracing is a very common method of measuring the OTF of an optical system. It is simple to set up, but the sampling size is limited and derivation of the Edge Spread Function is required in order to obtain the Line Spread Function (LSF). This derivation induces considerable high frequency noise. A competing method, slit tracing, is more complex mainly because of physical limitations such as the actual slit width. It has the advantages of directly providing the Line Spread Function (LSF), and having constant noise over all frequencies. Both methods gave equally good results at low noise levels, but Edge tracing was found to be advantageous at higher noise levels