The term ‘fast FLIM’ is often misleading since it is used for different aspects of a time-resolved TCSPC measurement. The most important parameter in a TCSPC experiment is the time resolution on the picosecond to nanosecond time scale. In the context of TCSPC ‘fast’ suggests a high time resolution. That is the capability of the device to differentiate between fast fluorescence decays, i.e. short fluorescence lifetimes. This is how Becker & Hickl does understand and use the term ‘fast’ or ‘ultra fast’.
However, there are other suppliers who use the term ‘fast’ with the meaning of a fast measurement. For them ‘fast FLIM’ means a FLIM experiment with a short acquisition time. Often, such systems (physically) sacrifice the time resolution on the picosecond time scale and by that achieve the opposite of fast TCSPC. In order to clearly distinguish between these two meanings of ‘fast’, Becker & Hickl does call its own systems capable of extra short acquisition time ‘fast acquisition’ or short ‘FASTAC’ system. Interestingly, in contrast to all other existing ‘fast acquisition’-FLIM systems on market the new and patented Becker & Hickl ‘FASTAC’ system provides the highest available TCSPC time resolution at the same time.