The Dow Chemical Company

Richard D McLachlan

Ray W Chrisman

Mary Anne Leugers

Robert A Bredeweg

Richard S Harner

Gary L Jewett

John C Evans

Leslie D Rothman

A fiber optic probe apparatus useful for conducting Raman spectroscopy remotely over optical fibers with minimal interference from Raman scattering within said fibers which includes three elements. The first element is at least one transmitting optical fiber having a first end and a second end. The second element is at least one collecting optical fiber for collecting light from a sample positioned near the first end of the transmitting optical fiber, the collecting optical fiber having a first end and a second end, the first end of the collecting optical fiber being in closely spaced relationship with the first end of the transmitting optical fiber wherein the longitudinal axis of the first end of the collecting optical fiber converges with the longitudinal axis of the first end of the transmitting optical fiber at an angle of less than forty five degrees. The third element is at the heart of the invention. The third element is a rejection optical filter in optical communication with the second end of the collecting optical fiber.

Apparatus for conducting Raman spectroscopy using fiber optics

A probe for use in situ analysis of light absorbing fluids wherein light emitted from a source is collimated by a lens and transmitted through a fluid onto and substantially perpendicular to a reflector. Light is reflected by the reflector back through the fluid and focused by the lens onto a reflected light collector for transmission to analyzing apparatus. The length of the path traversed by the emitted and reflected light is adjustable.

Variable path length light transmission probe

The presence and concentration of a light absorbing constituent in a fluid medium is determined in-situ by immersing in such medium a probe having a prism at one end whose refractive index is greater than that of the medium and causing light including a wavelength absorbable by such constituent to traverse an optical path through the prism and undergo successive attenuated total reflections. At each reflection some of the light will be absorbed by the constituent. The intensity of light emerging from the prism is measured at one or more wavelengths, including one absorbable by such constituent. The concentration of the constituent is determined by comparison of the measured intensity with values obtained from like measurements performed on like mediums containing known concentrations of the constituent.

Methods and apparatus for measuring the light absorbance of a fluid

A method for determining the size of moving objects present in a transparent or translucent fluid medium comprises illuminating a zone of the suspension with monochromatic light, collecting scattered light having a wavelength characteristic of the objects or of the medium, and measuring the intensity and variations in intensity of the collected light. The data thus obtained may be compared with data obtained from corresponding measurements of corresponding mediums containing corresponding objects of known size.

Method for measuring the size of objects in a fluid medium

A fiber optic probe having a sealed, cylindrical housing closed at one end by a transparent window and at the opposite end by a wall through which a plurality of optical fibers extend toward the window. Adjacent the window the fibers are radially and circumferentially spaced about the axis of the housing and converge along lines which intersect one another at a common point on the housing axis that is adjacent or beyond the outer surface of the window. At least one of the fibers transmits light from a source through the window to illuminate a zone of a fluid sample, whereby particles present in such zone scatter light therefrom to the remaining fibers for transmission through the probe housing to light detecting and measuring apparatus.

Fiber optic probe

A method for determining the onset of nucleation wherein a zone of a translucent fluid in which crystals may be formed is illuminated by a beam of light. When crystallization commences the crystals in the illuminated zone reflect and scatter light. Some of the scattered light is collected and transmitted to a light sensitive detector operable to generate a signal indicative of nucleation. Upon detection of nucleation either manual or automatic procedures may be instituted to modify the crystallization process in an appropriate manner.

Method for determining the onset of crystallization

The concentration of larger particles in a suspension of relatively small and relatively large light scattering particles is determined by illuminating a zone of the suspension with light of such wavelength as to be scattered more efficiently by the larger particles than by the smaller particles. The scattered light is collected and its intensity measured. The value of the collected light intensity then is compared with the corresponding value of the same wavelength light scattered by corresponding suspensions containing known concentrations of particles.

Method for measuring the relative concentration of larger and smaller

A fiber-optic probe, useful for light scattering and luminescence measurements, which comprises at least one optical fiber for transmitting light into a sample and at least two optical fibers for collecting light from the sample. The probe may further comprise a shield surrounding the fibers and having an optical window at one end to protect the fibers from hostile environments. When used in conjunction with a laser as a light source, the probe is particularly suited for Raman spectroscopy.

Growing community of inventors

Midland, MI, United States of America

Richard D McLachlan