Further discussion of Huygens-Fresnel principle

Abstract

ABSTRACT Huygens-Fresnel principle is well used in analyzing wavefront propagation in vacuum. However, we should clear if this principle is available in the space including absorptive objection, such as a grating. In this paper we analyze if a grating can diffract a beam when the grating set on the focus point and the grating pitch is larger than the Airy disc, especially the phenomenon in a special interferometer [1] . The special interferometer shown in reference [1] has an extended incoherent light source modulated by a binary grating. The light source is imaged onto a sinusoidal transmission grating by the tested lens. The pitch of the binary grating is half of the period of the sinusoidal grating. Light coming from an arbitrary point of the light source is focused onto the sinusoidal grating. Two kinds of analysis method are considered. One is using Huygens-Fresnel principle as described in reference [1]: the concave beam can be resolved to a pair of waves. Each wave is diffracted by the sinusoidal grating. By using the modulated extended light source, only one color interferogram interfered by -1