Studying the imaging process and image quality evaluation of optical systems is an important aspect in the field of modern optical information processing. For an optical system, due to the constraints imposed by the system on the light beam, the image formed of a point object is a diffraction spot determined by the system's aperture. The image of an extended object formed by the optical system is the superposition of diffraction spots corresponding to all points constituting the object. It is precisely due to the diffraction effect of the optical system that the image formed by an ideal optical system cannot perfectly resemble the object itself. The optical transfer function can quantitatively describe the propagation of each frequency component in the object's spectrum through the optical system, thereby fundamentally reflecting the changes between the object and the image, and providing a more scientific evaluation of imaging quality. Today, this theory is widely applied in evaluating optical design results, testing the quality of optical lenses, overall optical system design, and optical information processing, among other areas.