Figure 8.

Graphical representation of phase contrast. (a) Complex plane representation of a wave vector ψ with phase θ. (b) Vector representation of the scattered wave ψ_s, unscattered wave ψ_u, and resultant wave ψ_sam = ψ_u + iψ_s. Amplitudes (vector lengths) of ψ_sam and ψ_u are very similar, resulting in low image contrast. (c) −π/2 phase shift of the scattered wave leads to a noticeable decrease in the resultant wave amplitude relative to the unscattered wave (negative phase contrast). (d) π/2 phase shift of the scattered wave increases the amplitude of the resultant wave relative to the unscattered wave (positive phase contrast).