PULSED AND CW CONFOCAL MICROSCOPY - A COMPARISON OF RESOLUTION AND CONTRAST

Scanning confocal microscopy using pulsed illumination is investigated theoretically and experimentally. The point-spread-function of a conf ocal microscope operating with pulsed illumination is derived and comp ared to its continuous wave counterpart. High aperture confocal images of scattering point-like objects are recorded with pulses of 220 fs, and with a continuous beam. The images are compared paying particular attention to differences in resolution and contrast. Whereas no signif icant change in resolution has been observed for pulsed mode, the cont rast of scanning reflection microscopy is enhanced when pulsed operati on is employed. For ultrashort transform-limited pulses ( < 50 fs) a s ignificant increase of resolution is predicted. This resolution increa se amounts to 20% at a pulse duration of 10 fs.