Fig. 3.

Schematic of various possibilities cross-cumulants can be used for. The squares represent pixels of the CCD-camera. (A) Second-order cross-correlation. By cross-correlating (indicated by arrows) two directly neighboring pixels (light blue squares) virtual, “cross-correlation” (red squares) pixels can be obtained. These pixels lie in between the physical camera pixels. (B). The same holds true for higher-order cross-cumulants. As shown on the example of the fourth order cross-cumulant. Using different combinations of the light blue pixels 16-times more virtual pixels can be generated. (C) Second-order correlation. The value for the red target pixel can be obtained by correlating various different pairs of pixels (as indicated by black and gray arrows). This way auto-correlations can be omitted completely.