Synchronization

In order to perform imaging, the spatial origin of the photons must be recovered, which requires a synchronization information from the LSM controller. Typically an implementation with synchronization signals at the beginning of each line and frame is used. The TTTR mode of the PicoHarp 300 allows to record such synchronization signals with a nanosecond resolution. These signal markers will appear as special bits in the TTTR data stream generated during the measurement. This makes it possible to reconstruct the 2D image from the stream of TTTR records, since the relevant XY position of the laser scanner can be determined during the data analysis. The collection time and time channel number are virtually unlimited and each individual frame remains available for analysis. Restrictions arise only from hard disk and/or computer memory size, which is not a practical limitation with modern computers.

The general setup is shown below: The excitation light is coupled to an appropriate excitation port of the microscope using single mode fibers, whereas a multimode fiber is used to guide the emission light from the microscope to the detector. The overall data acquistion is done with the PicoHarp 300 running in the TTTR mode, which incorporates all necessary synchronization signals from the LSM controller, the detector as well as from the laser driver. A special Laser Combining Unit (LCU) permits to combine pulsed lasers and (if necessary) also the cw-lasers of the LSM into one single mode fiber, which facilitates switching between different operational modes.