Apparatus for near-infrared spectrophotometric analysis

• US 5,206,701 A
• Filed: 09/20/1991
• Issued: 04/27/1993
• Est. Priority Date: 09/20/1991
• Status: Expired due to Term

• Current Assignee: Amoco Corporation (BP PLC)
• Original Assignee: Amoco Corporation (BP PLC)
• Inventors: Cutshall, Ronald L., Taylor, James L., Baughman, Ernest H.
• Primary Examiner(s): McGraw, Vincent P.
• Application Number:
  US07/764,146
• Time in Patent Office: 585 Days
• Field of Search: 356/319, 356/323, 356/325, 356/328, 250/339, 250/343, 250/353
• US Class Current: 356/325
• CPC Class Codes: G01J 3/08 Beam switching arrangements
• CPC Class Codes: G01N 2021/1751 Constructive features therefore, e.g. using two measurement cells
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems
• CPC Class Codes: G01N 21/276 with alternation of sample and standard in optical path
• CPC Class Codes: G01N 21/359 using near infrared light
• CPC Class Codes: G01N 2201/084 Fibres for remote transmission

Abstract

An apparatus is provided for obtaining spectral information and quantifying the physical properties of a sample. The apparatus comprises a light source and a high-efficiency fiber optic switch means communicating with the light source for directing the light alternatively along at least two channels, the two channels comprising at least one reference channel and at least one sample channel. A sample means communicates with the sample channel for providing an interface between the light and the sample. A fiber optic means comprising a high-efficiency fiber optic switch and/or an optical coupler communicates with the sample channels and the reference channels and directs the light alternatively from the reference and sample channels to a mode scrambler. A wavelength discrimination device separates the light from the mode scrambler into component wavelengths and provides spectral information for the determination of the physical properties of the sample. The apparatus of the present invention provides superior chemometric prediction accuracy, is reliable, durable, and stable over time, and provides outstanding performance in a manufacturing or field environment.

Claims

1. An apparatus for obtaining spectral information and quantifying the physical properties of a sample comprising:

a light source for providing light;

a high-efficiency fiber optic switch means, in communication with said light source through a single fiber optic strand, said high-efficiency fiber optic switch means directing said light alternatively along at least two channels, said channels comprising at least one reference channel and at least one sample channel;

a sampling means in communication with said sample channel for providing an interface between said light and said sample;

a mode scrambler;

a fiber optic means selected from the group consisting of a high-efficiency fiber optic switch and an optical coupler, in communication with said sample channels and said reference channels for directing said light alternatively from said reference and sample channels to said mode scrambler;

a wavelength discrimination device for separating said light into component wavelengths and providing spectral information for the determination of the physical properties of said sample.

2. The apparatus of claim 1 wherein said light source is a polychromatic light source.

3. The apparatus of claim 2 wherein said polychromatic light source is a tungsten-halogen lamp.

4. The apparatus of claim 1 wherein said fiber optic means is a high-efficiency fiber optic switch and said high-efficiency fiber optic switch means and said fiber optic means consisting of a high-efficiency fiber optic switch have mechanical motion mechanisms.

5. The apparatus of claim 4 wherein said mechanical motion mechanisms are latching type mechanical motion switches.

6. The apparatus of claim 1 wherein said high-efficiency fiber optic switch directs said light to and from one reference channel and at least one sample channel.

7. The apparatus of claim 1 wherein said mode scrambler comprises a long run of fiber optic cable ranging in length from about 100 feet to about 5000 feet.

8. The apparatus of claim 1 wherein said spectral information is limited to wavelengths in the range of from about 800 nanometers to about 1100 nanometers.

9. The apparatus of claim 1 wherein said wavelength discrimination device comprises a spectrograph, said spectrograph comprises a diffraction grating and a photodiode array detector, and said photodiode array detector has a spatial resolution of at least 1 pixel per nanometer.

10. The apparatus of claim 1 wherein said wavelength discrimination device comprises a spectrograph, said spectrograph comprises a diffraction grating and a photodiode array detector, and said photodiode array detector has a wavelength resolution of better than 4 nanometers.

11. An apparatus for obtaining spectral information and quantifying the physical properties of materials comprising:

a polychromatic light source for providing light;

a first high-efficiency fiber optic switch means, in communication with said polychromatic light source through a single fiber optic strand, said high-efficiency fiber optic switch means directing said polychromatic light alternatively along at least two channels, said channels comprising at least one reference channel and at least one sample channel;

a sampling means in communication with said sample channel for providing an interface between said polychromatic light and said sample;

an attenuation means along said reference channel for balancing the polychromatic light transmission between the sample and reference channels;

a mode scrambler;

a second high-efficiency fiber optic switch means, in communication with said sample channels and said reference channels for directing said polychromatic light alternatively from said reference and sample channels to said mode scrambler;

a spectrograph for diffracting said polychromatic light into component wavelengths and providing spectral information for the determination of the physical properties of said sample.

12. The apparatus of claim 11 wherein said polychromatic light source is a tungsten-halogen lamp.

13. The apparatus of claim 11 wherein said first and second high-efficiency fiber optic switches are mechanical motion switches and direct said polychromatic light to and from one reference channel and at least one sample channel.

14. The apparatus of claim 11 wherein the fiber optics used in said high-efficiency fiber optic switches are externally cladded and said external cladding material comprises fluorocarbon.

15. The apparatus of claim 11 wherein said mode scrambler comprises a long run of fiber optic cable ranging in length from about 100 feet to about 5000 feet.

16. The apparatus of claim 11 wherein said spectrograph comprises a diffraction grating and a photodiode array detector and said photodiode array detector has a spatial resolution of at least 2 pixels per nanometer.

17. The apparatus of claim 11 wherein said spectrograph comprises a diffraction grating and a photodiode array detector and said photodiode array detector has a wavelength resolution of better than 4 nanometers.

18. The apparatus of claim 11 wherein said attenuation means comprises at least one member selected from the group consisting of one or more lenses, fiber optic cable, and fiber optic cable connecting devices.

19. The apparatus of claim 18 wherein said attenuation means comprises two plano convex lenses in series.

20. The apparatus of claim 11 wherein the optical elements of said spectrograph are mounted on temperature expansion resistance materials, said materials comprising at least one member selected from the group consisting of carbon fibers in an epoxy matrix and graphite fibers in an epoxy matrix.

21. The apparatus of claim 11 wherein the optical elements of said spectrograph are mounted on temperature expansion resistance materials, said materials comprising at least one carbon fiber in an epoxy matrix.

22. An apparatus for obtaining spectral information and quantifying the physical properties of materials comprising:

a polychromatic light source for providing polychromatic light;

a first high-efficiency fiber optic switch means, in communication with said polychromatic light source, said high-efficiency fiber optic switch means directing said polychromatic light alternatively along at least two channels, said channels comprising one reference channel and at least one sample channel;

a sample cell, in communication with said sample channel for providing an interface between said polychromatic light and said sample, said sample cell comprising a reflection device for passing said polychromatic light through said sample at least once;

an attenuation means along said reference path for balancing the polychromatic light transmission between the sample and reference channels;

a mode scrambler;

a second high-efficiency fiber optic switch means, in communication with said sample channels and said reference channel for directing said polychromatic light alternatively from said reference and sample channels to said mode scrambler;

a spectrograph comprising a fixed diffraction grating, a photodiode array detector, and optical elements for imaging polychromatic light from said mode scrambler onto said diffraction grating and onto said photodiode array detector, for diffracting said polychromatic light into component wavelengths and providing spectral information for the determination of the physical properties of said sample.

23. The apparatus of claim 22 wherein said polychromatic light source is a tungsten-halogen lamp.

24. The apparatus of claim 22 wherein said first and second high-efficiency fiber optic switches are latching type mechanical motion switches.

25. The apparatus of claim 22 wherein said high-efficiency fiber optic switches comprise a manifold and a multi-plexer device for directing light to and from one reference channel and at least two sample channels.

26. The apparatus of claim 22 wherein spectral information is limited to wavelengths in the range of from about 850 nanometers to about 1000 nanometers.

27. The apparatus of claim 22 wherein said mode scrambler comprises a long run of fiber optic cable ranging in length from about 200 feet to about 2000 feet.

28. The apparatus of claim 22 wherein said photodiode array detector has a spatial resolution of at least 2 pixels per nanometer.

29. The apparatus of claim 22 wherein said photodiode array detector has a wavelength resolution of better than 2 nanometers.

30. The apparatus of claim 22 wherein said attenuation means comprises two plano convex lenses in series.

31. The apparatus of claim 22 wherein said sample cell reflection device reflects said polychromatic light at least 3 times and passes said polychromatic light through said sample stream at least twice.

32. The apparatus of claim 22 wherein said sample cell is inserted into the sample source, said sample source comprising at least one member selected from the group consisting of a pipeline and a vessel.

33. The apparatus of claim 22 wherein said sample cell is positioned at a location away from the sample source and said sample is directed to said sample cell through a slip-stream.

34. The apparatus of claim 22 wherein the optical elements of said spectrograph are mounted on temperature expansion resistance materials, said materials comprising at least one member selected from the group consisting of carbon fibers in an epoxy matrix and graphite fibers in an epoxy matrix.

35. The apparatus of claim 22 wherein the optical elements of said spectrograph are mounted on materials comprising at least one carbon fiber in an epoxy matrix.