The diagram of our simple imaging system.

<p>A LeCroy WaveRunner 64xi oscilloscope acts as both the scan controller and the data acquisition system. Radio-frequency signals generated by the AD9959 Direct Digital Synthesis chip, which is controlled by the oscilloscope via USB, are amplified and injected into a compact two-axis acousto-optic deflector. Long laser pulses have narrow spectral bandwidth and so obviate the need for dispersion compensation. The use of mirrors M1 and M2 instead of lenses allows for a very compact microscope. Mirror M3 steers fluorescence collected by the condenser to the photomultiplier (PMT). A fast photodiode (PD) collects transmitted excitation light that was deflected to large angles to provide oblique contrast for observing cells in non-fluorescent tissue. A very fast photodiode (FastPD) reports laser pulse timing for fluorescence lifetime measurements.