Tandem-Scanning (Spinning Disk) Microscopes
The typical laser scanning confocal microscope has the major disadvantage of being relatively slow in image acquisition. The technological limitation is the need for the fast (X) scan mirror to scan 512 times (or more) per frame, which means that it must oscillate at 2000 Hz in a typical CLSM
with a maximum frame rate of 4 per second. Like pie crusts, technological limits are made to be broken, and several manufacturers have made traditional single-spot CLSMs operating at faster frame rates, even up to video speed (25 Hz). However, as we saw in Chapter 6, even at rather pedestrian frame rates the dwell time on each pixel is the major limitation to obtaining adequate signal-to-noise ratios, so eventually high-speed, single-spot scanners simply run out of signal. This limitation has led to the development of a varied range of microscopes that have, as their basic principle, the ability to scan more than one point at a time, while retaining the basic confocal geometry.