Fresnel diffraction with rectangular aperture based on MATLAB

One 、 principle

In optics , Fresnel diffraction ( Fresnel diffraction) It refers to the diffraction of light waves in the near-field region . The Fresnel diffraction integral can be used to calculate the propagation of light wave in the near field , Because French physicist Augustine ・ fresnel ( Augustin- Jean Fresnel) And name , Is an approximation of Kirchhoff diffraction formula . The characteristic Fresnel number of each optical system , It is possible to distinguish whether the region of light wave propagation is near field or far field . Imagine that light waves are incident on an arbitrary aperture , For this optical system , Fresnel number is defined as ：

$$F=\frac{a^2}{L\lambda }$$

In style ,a Is the size of the aperture ;L Is the distance between the aperture and the viewing screen ;λ Is the wavelength of the incident wave .

If F≥1, The diffracted wave is in the near field , Fresnel diffraction integral formula can be used to calculate its physical properties . If F≤1, The diffracted wave is in the far field , The Fraunhofer diffraction integral can be used to calculate its physical properties . Suppose the irradiating light wave irradiates on an opaque baffle with an aperture , The diffraction pattern will appear on the observation screen . According to Huygens - Fresnel principle , From an arbitrary point within the aperture Q The spherical surface secondary wave emitted , At the observation screen P The amplitude of this is

Two 、 Simulation results

Suppose you have the following rectangular aperture ; The figure below shows the amplitude and phase of the rectangular aperture .

The amplitude and phase after Fresnel diffraction are shown in the figure below ：

The amplitude profile of Fresnel diffraction pattern is given , As shown in the figure below ：

3、 ... and 、 Program acquisition

The simulation program can be obtained from the following link ：

https://download.csdn.net/download/qq_36584460/80836789