Low aberration diffraction grating system

• US 5,371,586 A
• Filed: 10/09/1992
• Issued: 12/06/1994
• Est. Priority Date: 10/09/1992
• Status: Expired due to Term

• Current Assignee: Horiba Instruments Incorporated (Horiba Limited)
• Original Assignee: Texas Instruments, Inc.
• Inventors: Chau, Chiu
• Primary Examiner(s): Evans, F. L.
• Application Number:
  US07/960,091
• Time in Patent Office: 788 Days
• Field of Search: 356/300, 356/301, 356/318, 356/326, 356/328, 356/331, 356/332, 356/334, 250/458.1, 250/459.1, 250/461.1, 250/461.2
• US Class Current: 356/301
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0227 using notch filters
• CPC Class Codes: G01J 3/18 using diffraction elements, e.g. grating gratings per se G02B
• CPC Class Codes: G01N 2021/6471 Special filters, filter wheel
• CPC Class Codes: G01N 2021/6473 In-line geometry
• CPC Class Codes: G01N 21/65 Raman scattering

Abstract

A light analysis system is disclosed and comprises a source of substantially collimated light to be analyzed. The source comprises a sample excited by a collimated laser light source, and further comprises a holographic notch filter having the characteristic of reflecting light at the excitation wavelenghth at which the source is excited. An aberration corrected concave focusing diffraction grating receives the collimated light and focuses it at a point corresponding to its wavelength. A detector detects light at a desired wavelength focused by the diffraction grating. The holographic notch filter is positioned to filter the source of substantially collimated light to be filtered and the holographic notch filter is oriented substantially at an angle with respect to the collimated laser light source to result in a path length for the collimated laser light source which constrains a path length through the notch filter which causes the collimated laser light to be reflected by the filter away from the grating. The grating is an aberration corrected concave focusing diffraction grating. The collimated light is in the form of a bundle having a width on the order of ten millimeters.

Claims

1. A light analysis system, comprising:

(a) a source of substantially collimated light to be analyzed, said collimated light being in the form of a bundle having a width with a magnitude on the order of ten millimeters;

(b) an aberration corrected concave focusing diffraction grating for receiving said collimated light and focusing it at a point corresponding to its wavelength; and

(c) a detector for detecting light at a desired wavelength focused by said diffraction grating.

2. A system as in claim 1, wherein said collimated light is filtered by a holographic notch filter.

3. A system as in claim 1, wherein said detector is a photomultiplier tube.

4. A system as in claim 1, wherein said detector is an array detector.

5. A system as in claim 1, wherein said detector is an area detector.

6. A system as in claim 1, wherein said grating is rotated to select a desired wavelength.

7. A system as in claim 1, wherein said source comprises a collimated laser light source generating collimated laser light and a sample excited by said collimated laser light source to generate said light to be analyzed, and said system further comprising a holographic notch filter receiving said light to be analyzed and having the characteristic of reflecting light at the excitation wavelength at which said sample is excited, said holographic notch filter being positioned to filter said source of substantially collimated light to be analyzed and said holographic notch filter being oriented substantially at an angle with respect to said collimated laser light source which results in a path for said collimated laser light source which constrains a path length through said notch filter which causes that portion of said collimated laser light which passes through said sample to be reflected by said filter away from said grating.

8. A system as in claim 1, wherein said source comprises a light source positioned to excite a sample to emit emitted light and collimating optics to collimate said emitted light.

9. A light analysis system, comprising:

(a) a source of substantially collimated light to be analyzed, said source comprising a collimated laser light source generating collimated laser light and a sample excited by said collimated laser light source to emit said light to be analyzed;

(b) a holographic notch filter positioned with respect to said sample to filter light emitted by said sample and to have the characteristic of reflecting light at the excitation wavelength at which said sample is excited;

(c) an aberration corrected concave focusing diffraction grating for receiving said filtered collimated light and focusing it at a point corresponding to its wavelength; and

(d) a detector positioned at said point for detecting light at a desired wavelength focused by said diffraction grating.

10. A system as in claim 9, wherein said holographic notch filter is positioned to filter said source of substantially collimated light to be analyzed and said holographic notch filter is oriented substantially at an angle with respect to said collimated laser light source which results in a path for said collimated laser light source which constrains a path length through said notch filter which causes that portion of said collimated laser light which passes through said sample to be reflected by said filter away from said grating.

11. A light analysis system, comprising:

(a) a source of substantially collimated light to be analyzed, said source comprising a laser light source generating laser light and a sample excited by said laser light source to emit said light to be analyzed;

(b) an optical element for collimating said light to be analyzed;

(c) a holographic notch filter receiving said light to be analyzed and having the characteristic of reflecting light at the excitation wavelength at which said sample is excited;

(d) an aberration corrected concave focusing diffraction grating for receiving said collimated light and focusing it at a point corresponding to its wavelength, said grating being mounted for rotation to select the focussing of a desired wavelength at said point; and

(e) a detector for detecting light at a desired wavelength focused by said diffraction grating, wherein said holographic notch filter is positioned to filter said source of substantially collimated light to be analyzed and said holographic notch filter is oriented substantially at an angle with respect to said collimated laser light source which results in a path for said collimated laser light source which constrains a path length through said notch filter which causes that portion of said collimated laser light which passes through said sample to be reflected by said filter away from said grating, and said collimated light is in the form of a bundle having a width with a magnitude on the order ten millimeters.