Abstract: A method for quickly performing an auto-focus operation on a confocal microscope. As a coarse Z-stage moves a target toward an objective lens, a photodetector generates an analog electronic focus signal which exceeds a threshold level during a focused condition. When a focused condition exists, a latching comparator, which is coupled to the electronic focus signal and to a signal representative of the threshold level, trips and the target is stopped. The analog nature of the electronic focus signal assures that the focused condition will be detected. As a result, the target may be moved quickly without missing a focused condition. The target is moved several times at progressively slower velocities to position the target close to the focus position.