Diffuse reflectance probe

DETAILED DESCRIPTION The present invention is based upon the discovery that a diffuse reflectance probe may provide effective illumination of a sample viewing area at a relatively close working distance by means of a window element that has a beveled surface disposed at the operating end of the probe.
The window is effective to direct the illuminating light towards the viewing area at the center of the probe in order to minimize the distance between the illuminated spot and the collection fiber (light collection element) to maximize the collection of the diffusely scattered light.
The window is further designed to direct any specularly reflected light off the front face of the window away from the field of view of the collection fiber.
In a particular embodiment, the invention comprises a fiberoptic probe employing a transmitting fiber and a collecting fiber, each having an optical axis and an end-face.
The collecting fiber has a field of view.
A window element having first, second and third light coupling surfaces including a beveled face surrounding a flat face and a sample viewing face spaced apart therefrom.
The beveled surface is located adjacent the end-face of the transmitting fiber and the flat face is located adjacent the collecting fiber.
The beveled surface is disposed at a selected angle relative to the axis of the transmitting fiber and the window has a selected thickness.
The angle and the thickness are selected so that light is directed towards the field of view of the collecting fiber and achieves maximum illumination at a relatively close working distance to the sample viewing face.
Specular reflectance is minimized, and the majority of such specular reflectance is directed beyond the field of view of the collecting fiber.
In another embodiment, the invention comprises a probe having a field of view and including plurality of transmitting fibers surrounding at least one collecting fiber, the transmitting and collecting fibers each have an optical axis in parallel axial alignment and each have a corresponding end-face