Assay methods and apparatus

Abstract

An optical assay apparatus is described which includes a light source module and an optical sensing element coupled by an interrogation module. The light source module produces light having propagation angles ranging from a lower, non-zero limit. This is accomplished by including an obscuration which blocks low propagation angle light. The sensing element includes a reflector portion and an sensing fiber portion. The reflector portion receives, as incident light, the light produced by the light source module and produces, as reflected light, light having an approximately constant propagation angle, preferably just less than the critical angle of the sensing fiber. The sensing element also includes a lens position which collimates signal recovery light collected by the sensing fiber. The interrogation module includes a window containing a light source optical fiber that transmits light from the light source module to the sensing element. The light source fiber has an angled end with a reflective surface to form a right-angle reflector and is embedded within the window in a slot containing an opaque material for absorbing back-scattered light. The sensing fiber may be appropriately adapted for evanescent-wave or surface plasmon resonance sensing operations.