Home About Us Laboratory Services Forensic Science Communications Back Issues January 2009 research Figure 6: Average correlation, pavg, as a...

Figure 6: Average correlation, pavg, as a function of the number of images, Np, used for calculating the reference pattern

Figure 6: Average correlation, ρavg, as a function of the number of images, Nρ, used for calculating the reference pattern

Average correlation, ρavg, as a function of the number of images, Nρ, used for calculating the reference pattern

This figure shows the average correlation, rho average (on the y-axis), as a function of the number of images, N rho, (on the x-axis) used for calculating the reference pattern. These curves are shown for five cameras. For c1, a line of red plus signs curves from a rho average of .01 and an N rho of 1, to a rho average of a little more than .08 and an N rho of 220; for c2, a line of green “x” symbols curves from a rho average of 0.005 and an N rho of 1, to a rho average of .05 and an N rho of 220; for c5, a line of blue diamonds curves from a rho average of .01 and an N rho of 1, to a rho average of .06 and an N rho of 220; for c9, a line of black triangles curves from a rho average of 0.005 and an N rho of 1, to a rho average of a little more than .04 and an N rho of 220; for c10, a line of magenta squares curves from a rho average of a little more than .02 and an N rho of 1, to a rho average of approximately .10 and an N rho of 220. The lines corresponding to different cameras saturate at different values of average correlation, indicating that the sensor noise varies from one imaging sensor to another. Some cameras are more affected by random noises than others.