METHOD AND APPARATUS FOR ALIGNING ELONGATED MICROBEADS IN ORDER TO INTERROGATE THE SAME

A method and apparatus are provided for aligning optical elements or microbeads, wherein each microbead has an elongated body with a code embedde d therein along a longitudinal axis thereof to be read by a code reading devic e. The microbeads are aligned with a positioning device so the longitudinal axi s of the microbeads is positioned in a fixed orientation relative to the code reading device. The microbeads are typically cylindrically shaped glass bead s between 25 and 250 microns (~m) in diameter and between 100 and 500 ~m long, and have a holographic code embedded in the central region of the bead, whic h is used to identify it from the rest of the beads in a batch of beads with many different chemical probes. A cross reference is used to determine which probe is attached to which bead, thus allowing the researcher to correlate t he chemical content on each bead with the measured fluorescence signal. Because the code consists of a diffraction grating typically disposed along an axis, there is a particular alignment required between the incident readout laser beam and the readout detector in two of the three rotational axes. The third axis, rotation about the center axis of the cylinder, is azimuthally symmetr ic and therefore does not require alignment.