A computer-controlled variable light attenuator for protection and autoranging of a laser-induced fluorescence detector for capillary zone electrophoresis

Photodetectors have a limited range over which they can measure light intensities for any particular setting. The intensity of light reaching the detector can be kept within this range by using a liquid crystal variable light attenuator controlled by a computer that continuously checks the amount of light reaching the detector and adjusts the attenuation to an appropriate level. Using such a system we have constructed an intensified charge-coupled device (ICCD) camera-based detector with a dynamic range of over six orders of magnitude which is never exposed to damaging or saturating light levels.