Encoder spectrograph with optimized diffraction grating

• US 7,430,044 B2
• Filed: 08/03/2007
• Issued: 09/30/2008
• Est. Priority Date: 06/28/2004
• Status: Expired due to Fees

• Current Assignee: Mudlogging Systems Inc. (ALS Oil & Gas)
• Original Assignee: Aspectrics
• Inventors: Hagler, Thomas W.
• Primary Examiner(s): EVANS, FANNIE L
• Application Number:
  US11/833,893
• Publication Number:
  US 20070268486A1
• Time in Patent Office: 424 Days
• Field of Search: 356/305, 356/310, 356/330
• US Class Current: 356/310
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0202 Mechanical elements; Supports for optical elements
• CPC Class Codes: G01J 3/0208 using focussing or collimating elements, e.g. lenses or mirrors; performing aberration correction
• CPC Class Codes: G01J 3/0229 using masks, aperture plates, spatial light modulators or spatial filters, e.g. reflective filters
• CPC Class Codes: G01J 3/0291 Housings; Spectrometer accessories; Spatial arrangement of elements, e.g. folded path arrangements
• CPC Class Codes: G01J 3/0294 Multi-channel spectroscopy
• CPC Class Codes: G01J 3/18 using diffraction elements, e.g. grating gratings per se G02B
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G01N 2021/317 Special constructive features
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/31 Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry G01N21/72 takes precedence
• CPC Class Codes: G01N 21/552 Attenuated total reflection
• CPC Class Codes: G01N 2201/129 Using chemometrical methods

Abstract

An encoder spectrograph is used to analyze radiation from one or more samples in various configurations. The radiation is analyzed by spatially modulating the radiation after it has been dispersed by wavelength or imaged along a line. Dual encoder spectrographs may be used to encode radiation using a single modulator. An encoder spectrograph may be used wherein the first optics comprises a diffraction grating that is optimized for an annular-shaped intercept between the dispersed image and the radiation filters on a modulator.

Claims

1. An encoder spectrograph for detecting one or more spectral components from a source, the spectrograph comprising:

first optics adapted to collect and focus radiation from a source to form a dispersed image along an encoding axis, the dispersed image characteristic of the spectral components of the source, wherein the first optics comprise a diffraction grating that disperses the radiation into at least two spectral components each having an annular-shaped intercept with a respective radiation filter on a modulator;

a spatial radiation modulator having at least two radiation filters located at different positions along the encoding axis, the radiation filters configured to modulate the spectral components with different modulation functions to provide an encoded beam comprising at least two encoded spectral components;

a detector;

second optics adapted to collect and direct the encoded beam onto the detector, causing the detector to provide an output corresponding to the encoded beam; and

a processor for analyzing the output from the detector to determine the spectral components modulated in the encoded beam.

2. The encoder spectrograph of claim 1, wherein in the first optics comprises a concave diffraction grating.

3. The encoder spectrograph of claim 1, wherein the second optics consists solely of a single reflective element and a single lens element.

4. The encoder spectrograph of claim 1, wherein the second optics comprises a fast collection optic.

5. The encoder spectrograph of claim 1, wherein the diffraction grating and detector are interchangeable with a different diffraction grating and a different detector.

6. The encoder spectrograph of claim 1, wherein the diffraction grating disperses the radiation into a plurality of concentric annuli at the intercept with the modulator.

7. An encoder spectrograph for detecting one or more spectral components from a source, the spectrograph comprising:

first optics adapted to collect and focus radiation from a source to form a dispersed image along an encoding axis, the dispersed image characteristic of the spectral components of the source, wherein the first optics comprise a diffraction grating that disperses the radiation into at least two spectral components each having an annular-shaped intercept with a respective radiation filter on a modulator;

a spatial radiation modulator having at least two radiation filters located at different positions along the encoding axis, the radiation filters configured to modulate the spectral components with different modulation functions to provide an encoded beam comprising at least two encoded spectral components, the radiation filters comprising at least three substantially distinct levels of contrast;

a detector;

second optics adapted to collect and direct the encoded beam onto the detector, causing the detector to provide an output corresponding to the encoded beam; and

a processor for analyzing the output from the detector to determine the spectral components modulated in the encoded beam.

8. The encoder spectrograph of claim 7, wherein in the first optics comprises a concave diffraction grating.

9. The encoder spectrograph of claim 7, wherein the second optics consists solely of a single reflective element and a single lens element.

10. The encoder spectrograph of claim 7, wherein the second optics comprises a fast collection optic.

11. The encoder spectrograph of claim 7, wherein the diffraction grating and detector are interchangeable with a different diffraction grating and a different detector.

12. The encoder spectrograph of claim 7, wherein the diffraction grating disperses the radiation into a plurality of concentric annuli at the intercept with the modulator.