Automated optical alignment system and method using raman scattering of

Abstract

A system and method are disclosed for optically aligning a capillary tube and an excitation laser beam for fluorescence detection applications by utilizing the Raman scatter signals of the capillary tube's contents. For example, Raman scatter by an electrophoretic separation matrix may be used for alignment in a capillary electrophoresis system. Fluorescent material may be present and may also be used for alignment purposes, but is not necessary. The invention employs a parabolic reflector, having apertures through which the capillary tube and the laser beam are guided so that they intersect, preferably at right angles and at the focal point of the reflector. The Raman scatter signals of the material within the capillary tube are collected via a series of filters and this information is used to reposition, if necessary, a focusing lens that directs the excitation beam into the reflector and the capillary tube, so that the Raman scatter signals are maximized. Maximal Raman scatter signals indicate proper alignment of the capillary tube and the excitation beam. Other signals, such as fluorescence emission from the sample, may then be gathered. Adjustment of the focusing lens may be automated so that alignment of the capillary tube and the beam is maintained throughout analysis of the tube's contents. Sequential alignment of an array of capillary tubes with an excitation beam is also disclosed.