MTF testing based on a pinhole target

In order to effectively evaluate the modulation transfer function of an objective or optical system, the pinhole image is scanned automatically by CCD, with consideration for the effects of the system and the environment on the pinhole image. The image processing for the system is performed by continuously collecting several pinhole images, averaging them and then subtracting their backgrounds from them. The proper integration area containing all target information is chosen, and the reliable MTF is achieved by deriving the onedimensional line spread function from the integration in the meridian and sagittal directions and then performing the discrete Fourier Transform with the processed data. The resulting data indicate that the MTFs of objectives under test can be measured quickly and accurately in this way.