When the incident angle θ θ i of the light onto the slit is non-zero (which causes a change in the path length), the intensity profile in the Fraunhofer regime (i.e. far field) becomes: I ( θ θ ) = I 0 sinc 2 ⁡ ⁡ [ d π π λ λ ( sin ⁡ ⁡ θ θ ± ± sin ⁡ ⁡ θ θ i ) ]