Optical transmission spectrometer

• US 5,155,628 A
• Filed: 07/20/1989
• Issued: 10/13/1992
• Est. Priority Date: 11/04/1988
• Status: Expired due to Term

• Current Assignee: Miles, Inc. (Bayer AG)
• Original Assignee: Miles, Inc. (Bayer AG)
• Inventors: Dosmann, Andrew J.
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): Kachmarik, Ronald M.
• Application Number:
  US07/382,296
• Time in Patent Office: 1,181 Days
• Field of Search: 350/286, 350/170, 350/171, 350/169, 350/133, 359/618, 359/639, 359/640, 359/837
• US Class Current: 359/640
• CPC Class Codes: G01N 2021/1742 either absorption or reflection
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems
• CPC Class Codes: G01N 2201/0813 Arrangement of collimator tubes, glass or empty
• CPC Class Codes: G02B 27/1006 for splitting or combining different wavelengths G02B27/1086, G02B27/141 take precedence
• CPC Class Codes: G02B 27/108 for sampling a portion of a beam or combining a small beam in a larger one, e.g. wherein the area ratio or power ratio of the divided beams significantly differs from unity, without spectral selectivity
• CPC Class Codes: G02B 27/143 using macroscopically faceted or segmented reflective surfaces
• CPC Class Codes: G02B 27/144 using partially transparent surfaces without spectral selectivity G02B27/147 takes precedence

Abstract

An optical transmission spectrometer for transmission measurements of absorbing and scattering samples includes light sources mounted parallel to each other in a holder. The beams of light emanating from the light sources are directed through a beam-combiner. The beam-combiner includes a first refractive surface at an angle of incidence of 45°. The first refractive surface refracts light toward a common axis. The beam-combiner includes a second refractive surface parallel to the first refractive surface for refracting the beam of light along a common axis parallel to the original direction of the beam of light. The beam-combiner can include additional refractive surfaces for other beams of light to combine the beams of light into a primary beam. The spectrometer includes a collimating tube extending along the common axis for baffling stray light and directing the primary beam through a sample. A second collimating tube is provided on the side of the sample opposite the first collimating tube for baffling stray light passing through the sample. The second collimating tube directs the primary beam to a detector package mounted in a holder, where the detector viewing area of the sample is limited to that of the primary beam. As an alternative, an optic which is capable of directing multiple light beams onto a common intersection point may be used in place of the previously mentioned beam-combiner. Unlike the beam-combiner which closely aligns multiple parallel light beams and transmits them as substantially a single beam along the common axis, the alternate optical directs multiple light beams at an angle onto a common intersection point. The optic is fabricated from translucent material with first and second refractive surfaces for receiving light beams from a source and refracting the light beams toward the common intersection point.

Claims

1. An optical transmission spectrometer for absorbing and scattering sample readings, comprising:

a plurality of light sources for producing light, the absorption of which in a sample is to be measured by the spectrometer;

a holder for said plurality of light sources;

a light beam-combiner for directing beams of light from said light sources by refraction to a common sample area;

said light beam combiner including first and second non-parallel refractive surfaces for refracting light from said light sources toward said common sample area;

said light beam-combiner being symmetrical about central axis;

a first collimating device adjacent said light beam-combiner for baffling stray light passing from the said light beam-combiner and the light source;

a mounting assembly for mounting a sample in said sample area in the optical transmission spectrometer adjacent said first collimating device; and

a detection assembly for detecting absorption of light passing through a sample in said mounting assembly.

2. The optical transmission spectrometer set forth in claim 1 further comprising a second collimating device mounted between said detection assembly and said mounting assembly for baffling stray light passing from a sample, and defining the detector viewing area to a beam passing through the sample area.

3. The optical transmission spectrometer set forth in claim 1 wherein the amount a beam of light is displaced upon passing through said beam-combiner can be calculated using the formula ##EQU2## where d is the amount of displacement, t is the thickness of the beam-combiner, N is the index of refraction of the beam-combiner and θ

is the angle of incidence.

4. The optical transmission spectrometer set forth in claim 1 wherein said plurality of light sources includes two light emitting diodes of different wavelengths.

5. The optical transmission spectrometer set forth in claim 1 wherein said first collimating device is an internally threaded tube wherein threads on the interior of the tube baffle stray light.

6. An optic for directing light from a plurality of sources to intersect at a common sample area spaced a predetermined distance from said optic, comprising:

a body of optically clear material, said body having a longitudinal axis and including an initial refractive surface and a secondary refractive surface;

said initial refractive surface being disposed at a first preselected angle with respect to said longitudinal axis and refracting incident light from said plurality of sources toward said secondary refractive surface;

said secondary refractive surface being disposed at a second preselected angle with respect to said longitudinal axis and refracting said incident light toward said common sample area, said second preselected angle being different from said first preselected angle; and

wherein said plurality of sources include light emitting diodes.

7. The optic, as set forth in claim 6, wherein said body is symmetrical about said longitudinal axis.

8. The optic, as set forth in claim 6, wherein said optically clear material is acrylic.

9. The optic, as set forth in claim 6, wherein said optically clear material is polycarbonate.

10. The optic, as set forth in claim 6, wherein selected light emitting diodes emit light having a selected wavelength and other light emitting diodes emit light having a wavelength different from said selected wavelength.

11. An optic for directing light from a plurality of sources to intersect at a common sample area spaced a predetermined distance from said optic, comprising:

a body of optically clear material, said body having a longitudinal axis and including an initial refractive surface and a secondary refractive surface;

said initial refractive surface being diposed at a first preselected angle with repect to said longitudinal axis and refracting incident light from said plurality of sources toward said secondary refractive surface;

said secondary refractive surface being disposed at a second preselected angle with respect to said longitudinal axis and refracting said incident light toward said common sample area, said second preselected angle being different from said first preselected angle; and

wherein said first preselected angle is 45°

.

12. The optic, as set forth in claim 11, wherein said second preselected angle is greater than 45°

.

13. The optic, as set forth in claim 12, wherein multiple light beams which are parallel to said longitudinal axis are refracted by said initial and secondary refractive surface to a common intersection point located a predetermined distance from said optic.

14. The optic, as set forth in claim 13, wherein said refracted light beams are not parallel to said longitudinal axis.

15. An optic for directing light from a plurality of sources to a common intersection point spaced a predetermined distance from said optic, comprising:

a body of optically clear material, said body having a longitudinal axis and including a first refractive surface and a second refractive surface;

said first refractive surface being disposed at a first preselected angle with respect to said longitudinal axis and refracting incident light from said plurality of sources toward said second refractive surface;

said second refractive surface being disposed at a second preselected angle with respect to said longitudinal axis, said second preselected angle being different from said first preselected angle, and refracting said incident light toward said common intersection point; and

wherein said plurality of sources include light emitting diodes.

16. The optic, as set forth in claim 15, wherein said body is symmetrical about said longitudinal axis.

17. The optic, as set forth in claim 15, wherein said optically clear material is acrylic.

18. The optic, as set forth in claim 15, wherein said optically clear material is polycarbonate.

19. The optic, as set forth in claim 15, wherein selected light emitting diodes emit light having a selected wavelength and other light emitting diodes emit light having a wavelength different from said selected wavelength.

20. An optic for directing light from a plurality of sources to a common intersection point spaced a predetermined distance from said optic, comprising:

a body of optically clear material, said body having a longitudinal axis and including a first refractive surface and a second refractive surface;

said first refractive surface being disposed at a first preselected angle with respect to said longitudinal axis and refracting incident light from said plurality of sources toward said second refractive from said plurality of sources toward said second refractive surface;

said second refractive surface being disposed at a second preselected angle with respect to said longitudinal axis, said second preselected angle being different from said first preselected angle, and refracting said incident light toward said common intersection point; and

wherein said first preselected angle is 45°

.

21. An optic for directing light from a plurality of sources to a common intersection point spaced a predetermined distance from said optic, comprising:

a body of optically clear material, said body including a first refractive surface and a second refractive surface;

said first refractive surface being disposed at a first preselected angle with respect to incident light from one of said plurality of sources and refracting said incident light toward said second refractive surface;

said second refractive surface being disposed at a second preselected angle with respect to said incident light and refracting said incident light toward said common intersection point, said second preselected angle being different from said first preselected angle wherein said first refractive surface and said second refractive surface are other than parallel; and

wherein said plurality of sources include light emitting diodes.

22. The optic, as set forth in claim 21, wherein said common intersection point is located in a common sample area.

23. The optic, as set forth in claim 21, wherein said optically clear material is acrylic.

24. The optic, as set forth in claim 21, wherein said optically clear material is polycarbonate.

25. The optic, as set forth in claim 21, wherein selected light emitting diodes emit light having a selected wavelength and other light emitting diodes emit light having a wavelength different from said selected wavelength.

26. The optic, as set forth in claim 21, wherein said first preselected angle is 45°

.

27. The optic, as set forth in claim 21, wherein multiple parallel incident light beams are refracted by said first and second refractive surfaces to said common intersection point.