Calculation
	Fluctuations carry the Information		How does FCS work? Measurement Calculation Evaluation Result
	The measured signal can be described as constant mean intensity < I > and a fluctuating contribution δI (t). These fluctuations δI (t) carry the information we are interested in.
	Calculating Correlation Function
	Calculating the autocorrelation function reveals similar features over time of the fluctuating signal. Similarities derive from common features of the detected molecules like number of molecules, diffusion times and triplet fraction.
	Auto Correlation Function
	Definition of auto correlation function alternative spelling
	Using intensity I written as mean intensity < I > plus fluctuations δI (t) Results in alternative form of auto correlation function
	Normalizing auto correlation function Results in form used normally. The information about the system is contained in δI (t).