Signal Processing for Modulation Transfer Function Test Bench

The signal processing flow for the MTF test bench that is based on Fourier analysis method is presented. The signal processing flow mainly consists of three parts that are Fourier analyzing, background correction and system attenuation elimination. The center of the pinhole area is recognized automatically and the line spread functions (LSF) of both sagittal and tangential directions are calculated. Second-order fast Fourier transform is executed so that a primary two-direction MTF result is gained. Either auto Fourier-domain background correction or manual time-domain background correction is executed. The attenuation of the tested MTF result due to the influence of the detector and pinhole is eliminated finally. A commercially available 50-mm plano-convex audit lens is tested as the sample to validate the accuracy of the signal processing flow of the MTF test bench. The test error is below 0.01 under 2001p/mm.