Fig. 1. Superposition intensity distributions formed by two diffracted incoherent point sources vs their separated distance. The blue (I₁) and red (I₂) lines represent the intensity distribution profiles of the two-point sources on the image plane, while the green one (I_sum) represents total intensity distribution profile

Fig. 2. Superposition total intensity distribution profiles formed by two diffracted coherent point sources with different phase difference at the separated distance of Rayleigh criterion. (a) Total intensity distribution profiles of the superimposed two Airy disk against their phase difference and the distance; (b) Intensity distribution profiles at φ = 0, π/2 andπ, respectively

Fig. 3. Criterion of resolution limit for two point sources with the same phase (φ=0) under coherent illumination. (a)-(d) Superposition total intensity distributin profiles under different separated distances of the two point sources

Fig. 4. Criterion of resolution limit for two point sources with the opposite phase (φ = π) under coherent light illumination. (a)-(d) Superposition total intensity distribution profiles with the reducing separated distance dx of the two point sources; (e) Superposition intensity distributions profiles for different values of dx; (f) Respectively normalized intensity distributions profiles corresponding to (e)

Fig. 5. Diffraction intensity patterns of (a) a single point and (b) a single slit, and (c) their corresponding intensity distributiong profiles

Fig. 6. Focusing beyond the diffraction limit. (a) Airy disk distribution of single point diffraction focusing; (b) Diffraction focusing Airy pattern of three coherent point source when placing two points of P₋₁ and P₊₁ at dx=5.136 with the same intensity and π phase shift to the central point ofP₀; (c)-(d) Diffraction Airy disk patterns when increasing the ratio of intensities of the P₋₁ and P₊₁ points to the central point P₀, β = I_±1/I₀; (e) The intensity distribution profiles along the dashed lines in (a)-(d)

Fig. 7. Focusing beyond the diffraction limit. (a)-(d) The diffraction patterns when the ±1 points move approaching to the center point; (e) The intensity distribution profiles along the dashed lines in (a)-(d)