Depth reconstruction with Fresnel diffraction

Optical diffraction happens in any optical imaging system, causing blurring degree of a defocused image to be higher than expected in geometric optics. In this paper, a novel Depth from Defocus (DFD) method based on optical diffraction is given. Firstly, the basic principle of Fresnel diffraction in an optical system is analyzed, and the relationship between Fresnel diffraction and defocused imaging is constructed. Secondly, an imaging model for defocus with optical diffraction is supposed through curve fitting, and based on relative blurring and heat diffusion, a new DFD method with optical diffraction and two defocused images is proposed. Finally, a standard nano grid is used to validate the proposed DFD method on nana scale. The results show that the new algorithm, compared with traditional DFD algorithms, is a more effective method to reconstruct depth information on nano scale.