Figure 3
From: Super sub-wavelength patterns in photon coincidence detection

Second-order correlation function Eq. (6) recorded using two CCDs.
x1 and x2 are the horizontal ordinates on CCD1 and CCD2, respectively. The lines represent various scanning methods for the detectors: line (a) for x1 = x and x2 = 0; line (b) for x1 = x and x2 = −x; line (c) for x1 = x and x2 = −2x; line (d) for x1 = x and x2 = x/2.