ABSTRACT
The typical confocal laser scanning microscope (CLSM) 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 most manufacturers now make traditional single-spot CLSMs operating at video speed (25 Hz) or faster. This is achieved by using a mirror vibrating at its resonant frequency for the fast scan (Tsien & Backsai, 1995). This enables it to scan much more rapidly but with the penalty that the scan speed cannot be changed. There is a further complication, since something vibrating resonantly moves like a pendulum in a sinusoidal motion rather than linearly. Therefore the speed varies over the width of the frame, being fastest in the middle and slowest at the edges. The manufacturer has to compensate for this or the image will be distorted.
