Optical probe for measuring light transmission of liquid

Claim 1

An optical probe useful for measurement of light transmission of liquid, comprising: a tubular housing with a cylindrical wall having one or more proximate openings therein; a solid cylindrical member formed of transparent material with a flat transparent end surface and an opposing curved surface having a selected curvature and being silvered so as to form an internally concave reflector, the cylindrical member being retained in the housing with the transparent end surface located adjacent to the openings; a transparent solid rod member with a flat first end surface and a flat second end surface parallel to the first end surface, the rod member being retained in the housing with the second end surface located adjacent to the openings and spaced from the transparent end surface parallel thereto so as to define a cavity therebetween such that, upon immersion of the probe, liquid passes through the openings into the cavity, the first end surface being spaced from the concave reflector cooperatively with the selected curvature, the cavity and indices of refraction of the reflector member, the rod member and the liquid so that selected first and second conjugate focal spots of the concave reflector are located in laterally spaced positions substantially at the first end surface; a first optical fiber with a planar end affixed transparently to the first end surface in alignment with the first focal spot; and a second optical fiber with a planar end affixed transparently to the first end surface in alignment with the second focal spot; whereby light entering the rod member from the first optical fiber passes twice through the liquid in the opening while being reflected by the concave reflector into the second optical fiber.