Imaging Using Wave Theory

In geometrical optics we used the thin lens equation to find the image point of an object point when using a thin lens of focal length f. Using wave theory we assume that Huygens’wavelets emerge from each point of the object and travel to the lens. The lens produces the diffraction pattern of the object in its focal plane, which may be seen as the Fourier transformation of the object pattern. The lens also produces the image of the object by refraction. A second Fourier transformation performed on the diffraction pattern results in a pattern having the shape of the object. Since the light travels forward, we associate it with the image. This is schematically shown in Figure 10.1.