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 reachin g 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 atten uation to an appropriate level. Using such a system we have constructe d an intensified charge-coupled device (ICCD) camera-based detector wi th a dynamic range of over six orders of magnitude which is never expo sed to damaging or saturating light levels.