This article [J. Biomed. Opt. 15(6), 066005 (2010)] was originally published online on Nov. 19, 2010 with an error in Eqs. (12) and (20). These equations contain errors in the factor of the second term. The error was due to the reason that electron multiplication process to background noise was not being fully included into the equation. The corrected form of these identical equations is
The correction has a negligible effect on Fig. 6, but has no effect on the remainder of the manuscript.