GB2219853A - A spectral filter - Google Patents
A spectral filter Download PDFInfo
- Publication number
- GB2219853A GB2219853A GB8814066A GB8814066A GB2219853A GB 2219853 A GB2219853 A GB 2219853A GB 8814066 A GB8814066 A GB 8814066A GB 8814066 A GB8814066 A GB 8814066A GB 2219853 A GB2219853 A GB 2219853A
- Authority
- GB
- United Kingdom
- Prior art keywords
- light
- spectral filter
- line
- line spectral
- filter
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 230000003595 spectral effect Effects 0.000 title claims abstract description 26
- 230000003287 optical effect Effects 0.000 claims abstract description 17
- 238000010521 absorption reaction Methods 0.000 claims abstract description 14
- 239000013307 optical fiber Substances 0.000 claims abstract description 10
- 238000001514 detection method Methods 0.000 claims description 10
- 239000000126 substance Substances 0.000 claims description 7
- 230000001419 dependent effect Effects 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 19
- 238000000862 absorption spectrum Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000003909 pattern recognition Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/28—Investigating the spectrum
- G01J3/457—Correlation spectrometry, e.g. of the intensity
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/02—Details
- G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
- G01J3/0229—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using masks, aperture plates, spatial light modulators or spatial filters, e.g. reflective filters
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/02—Details
- G01J3/06—Scanning arrangements arrangements for order-selection
- G01J2003/064—Use of other elements for scan, e.g. mirror, fixed grating
- G01J2003/065—Use of fibre scan for spectral scan
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/02—Details
- G01J3/06—Scanning arrangements arrangements for order-selection
- G01J2003/068—Scanning arrangements arrangements for order-selection tuned to preselected wavelengths
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/28—Investigating the spectrum
- G01J2003/2866—Markers; Calibrating of scan
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/02—Details
- G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
- G01J3/0218—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using optical fibers
- G01J3/0221—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows using optical fibers the fibers defining an entry slit
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/12—Generating the spectrum; Monochromators
- G01J3/18—Generating the spectrum; Monochromators using diffraction elements, e.g. grating
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
- G01J3/28—Investigating the spectrum
- G01J3/2803—Investigating the spectrum using photoelectric array detector
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N2021/3129—Determining multicomponents by multiwavelength light
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- General Physics & Mathematics (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
A multi-line spectral filter arrangement for detecting a wide variety of gasses comprises a light transmitter such as an optical fibre 4 for transmitting light via a lens 8 to a dispersive element such as a reflective diffraction grating 12, and light from the dispersive element is focussed onto a light detector 6. In a preferred embodiment a spatial filter 14 is disposed in the optical path between the lens and the light detector and a piezo-electric bender 16 moves the optical fibre in a plane perpendicular to the lines of the grating 12 for scanning the spectral filter response to detect selectively different absorption line patterns corresponding to the expected position of absorption lines of a gas to be monitored. Alternatively a detector array with weighted outputs may replace the single detector 6 and spatial filter 14, and other parts of the system may be moved to effect the wavelength scanning. <IMAGE>
Description
A SPECTRAL FILTER
The present invention relates to a spectral filter and more particularly to a multi-line spectral filter for a chemical detection system.
It is known to use a scanned optical source of monochromatic light (or of multi-line type such as from a Fabry-Perot laser) to monitor absorption of light in a gas. It is also well known to use a scannable Fabry-Perot filter as a scannable regularly-spaced comb filter for the detection of gases with a known set of regularly or nearly-regularly spaced absorption lines.
However, a problem with single line scannable systems is that only one absorption line of the gas may be monitored at one time, whereas a problem with scannable sources or scannable comb filters with a regularly-spaced multi-line output is that they are only suitable for a limited gaseous species with similar regularly spaced absorption lines.
An object of the present invention is to provide a multi-line spectral filter arrangement, which is adapted to monitor a specific gas to be monitored, but which does not rely on the lines being equally spaced, and hence is adapted to detect a wider variety of gases.
According to the present invention there is provided a multiline spectral filter for a chemical detection system comprising a light transmitter for transmitting light along an optical path to a light detector, a dispersive arrangement for causing wavelengthdependent angular deflections and a focussing means arranged relative to one another along the optical path whereby light received from the light transmitter is focussed by the focussing means onto the dispersive arrangement and light therefrom focussed onto the light detector, scanning means being provided for scanning the spectral filter response to detect selectively different absorption line patterns corresponding to the expected position of the absorption lines of the chemical to be monitored.
The dispersive arrangement may comprise a diffraction grating or a prism. In a preferred embodiment a spatial filter is disposed in the optical path between the focussing means and the light detector.
The scanning means may comprise means for moving the light transmitter in a plane perpendicular to ruled lines of the diffraction grating. Alternatively means may be provided for moving the light detector, the spatial filter or the focussing means or by changing the angle of the dispersive arrangement.
In one embodiment the light transmitter is an optical fibre supported on a piezo-electric stack which forms part of a piezoelectric transducer.
An array of optical fibres may be provided for transmitting light along the optical path to an array of light detectors.
Conveniently the array of optical fibres and the array of light detectors are located along a line parallel for example to the lines of the diffraction grating.
In another embodiment a light detector array is placed in the position of the coded mask or graticule and the outputs of the various light detectors processed by weighting the signals received according to the desired filter response.
Conveniently the chemical detection system for which the filter is employed is a gas detection system.
The invention will be described further, by way of examples, with reference to the accompanying drawings in which:
Figure 1 illustrates schematically a spectral filter arrangement according to an embodiment of the present invention,
Figure 2 is a plan view of the spectral filter arrangement illustrated in Figure 1,
Figure 3a is a graph showing a typical absorption spectrum for a gas and
Figure 3b is a graph showing a mask transmission pattern matching the absorption spectrum of Figure 3a.
Referring to Figures 1 and 2 a multi-line filter arrangement 2 comprises a light transmitter, in the form of an optical fibre 4, for transmitting light along an optical path to a light detector 6. Light from the optical fibre 4 is focussed by a lens 8 onto a diffraction grating 12. A region 10 between the lens 8 and the diffraction grating 12 defines a volume in which a gas to be monitored may be located. Light is reflected back from the diffraction grating 12 through the region 10 and is focussed by the lens 8 via a multiparallel-line spatial filter 14 onto the light detector 6.
The spatial filter 14 filters out a number of lines corresponding to a plurality of the absorption lines of the gas. The spatial filter may either consist of an electro-formed metal mask with parallel open slits or may consist of a photographic plate or film with similar parallel lines. The spatial filter is preferably arranged to have a series of transmits or pass-bands corresponding to the gas absorption lines to be monitored. Alternatively, a "negative" mask, blocking light at the gas absorption lines to be monitored may be used.Such a mask may either be produced by known photo-lithographic or similar processes from an artwork produced using illumination by light which has been passed through a high concentration of the gas to be measured and hence through a diffraction grating dispenser similar to the diffraction grating 12 of Figure 1 to expose the plate prior to photographic development.
In the embodiment of Figures 1 and 2 the optical fibre 4 is supported on a piezo-electric stack 16 which forms part of a piezoelectric "bender" type transducer. The transducer stack 16 moves the optical fibre 4 in a plane perpendicular to the ruled lines of the diffraction grating 12 and the detector 6 masks all the focussed light in plane view. In this way the optical fibre 4 is mechanically displaced to effectively cause a scanning of the filter response, such that the filter may be arranged to either correspond to, or not correspond to, the position of the absorption lines of the gas, as desired. This scanning may then be used to produce a changing or alternating signal to be used for detection for the gas.
An example of a suitable mask transmission pattern (Figure 3b) to match a known gas absorption spectrum (Figure 3a) is shown in order to illustrate how both may vary in transmission and absorption respectively, to form a suitable combination for gas detection. It will be understood that for a multi-line gas absorption spectrum the method allows a strong degree of pattern recognition or "fingerprinting" of the gas lines to make it particularly selective to the gas it is desired to monitor.
It will be understood that the wavelength scanning of the filter may be affected by moving other parts of the system (eg. by moving the detector 6, the spatial filter mask 14 or the focussing lens 8 nearest the grating 12 or by changing the angle of the grating) without departing from the spirit of the invention.
Other embodiments of the invention would be understood by the person skilled in the art. For example, the diffraction grating arrangement 12 could be a transmissive one employing a transmissive diffraction grating dispersive element.
In another embodiment the system may be multiplexed using an array of input optical fibres and an array of separate detectors.
The input optical fibres and the array of detectors are conveniently located along a line parallel to the rulings of the diffraction grating 12.
In more sophisticated embodiments moving parts of the filter arrangement may be eliminated without departing from the spirit of the invention For example a detector array may be arranged in the position of the coded mask or graticule 4 and the outputs of the various detectors processed by weighting the signals according to the desired filter response. Alternatively a number of small detectors may be arranged in an array in position according to the desired optical fibre response.
It will also be understood that whereas in the above embodiments reference has been made to the use of a diffraction grating as a dispersive element, other embodiments may include alternative dispersive arrangements as for example a prism.
Claims (15)
1. A multi-line spectral filter for a chemical detection system comprising a light transmitter for transmitting light along an optical path to a light detector, a dispersive arrangement for causing wavelength-dependent angular deflections and a focussing means arranged relative to one another along the optical path whereby light received from the light transmitter is focussed by the focussing means onto the dispersive arrangement and light therefrom focussed onto the light detector, scanning means being provided for scanning the spectral filter response to detect selectively different absorption line patterns corresponding to the expected position of the absorption lines of the chemical to be monitored.
2. A multi-line spatial filter as claimed in claim 1 wherein a spatial filter is disposed in the optical path between the focussing means and the light detector.
3. A multi-line spatial spectral filter as claimed in claim 1 or claim 2 wherein the scanning means comprises means for moving the light transmitter in a plane perpendicular to lines of a diffraction grating which serves as the dispersive arrangement.
4. A multi-line spectral filter as claimed in any one of claims 1 to 3 wherein the light transmitter is an optical fibre.
5. A multi-line spectral filter as claimed in any one of claims 1 to 4 wherein the light transmitter is supported on a piezo-electric stack which forms part of piezo-electric transducer.
6. A multi-line spectral filter as claimed in claims 1 or 2 wherein the scanning means comprises means for moving the light detector in a plane perpendicular to lines of a diffraction grating which serves as the dispersive arrangement.
7. A multi-line spectral filter as claimed in claim 2 wherein the scanning means comprises means for moving the spatial filter in a plane perpendicular to lines of a diffraction grating which serves as the dispersive arrangement.
8. A multi-line spectral filter as claimed in claim 1 or claim 2 wherein the scanning means comprises means for moving the focussing means relative to the dispersive arrangement.
9. A multi-line spectral filter as claimed in claim 1 or claim 2 wherein the scanning means comprises means for changing the angle of the dispersive arrangement relative to the light transmitter.
10. A multi-line spectral filter as claimed in any one of claims 1 to 9 wherein the light transmitter comprises an array of optical fibres for transmitting light along the optical path to an array of light detectors.
11. A multi-line spectral filter as claimed in claim 10 wherein the array of optical fibres and the array of light detectors are located along a line parallel to the lines of the diffraction grating.
12. A multi-line spectral filter as claimed in claim 1 wherein a light detector array is provided for receiving the light from the focussing means, and processing means is provided for weighting the signals received from each of the detectors in the array according to the desired filter response.
13. A multi-line spectral filter substantially as hereinbefore described with reference to Figures l and 2 of the accompanying drawings.
14. A chemical detection system incorporating a multi-line spectral filter as claimed in any one of claims 1 to 13.
15. A gas detection system incorporating a multi-line spectral filter as claimed in any one of claims 1 to 13.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8814066A GB2219853A (en) | 1988-06-14 | 1988-06-14 | A spectral filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8814066A GB2219853A (en) | 1988-06-14 | 1988-06-14 | A spectral filter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8814066D0 GB8814066D0 (en) | 1988-07-20 |
| GB2219853A true GB2219853A (en) | 1989-12-20 |
Family
ID=10638622
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8814066A Withdrawn GB2219853A (en) | 1988-06-14 | 1988-06-14 | A spectral filter |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2219853A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0452095A1 (en) * | 1990-04-13 | 1991-10-16 | Hughes Aircraft Company | Dispersive holographic spectrometer |
| FR2847668A1 (en) * | 2002-11-25 | 2004-05-28 | Jobin Yvon Sas | High resolution spectrometer for application to variable spectral domains, comprises point source sending beam through first optical element, a grism, a second optical element and means of detection |
| US7196791B2 (en) | 2000-11-30 | 2007-03-27 | Tomra Systems Asa | Optical detection device |
| CN104729710A (en) * | 2015-04-08 | 2015-06-24 | 武汉邮电科学研究院 | Spectrum analyzer based on liquid crystal on silicon and realization method thereof |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB732058A (en) * | 1951-08-10 | 1955-06-15 | Leeds & Northrup Co | Improvements in multiple slit spectrograph for direct reading spectrographic analysis |
| GB1150531A (en) * | 1966-06-23 | 1969-04-30 | Barringer Research Ltd | Spectrophotometer |
| GB1195840A (en) * | 1967-01-10 | 1970-06-24 | Barringer Research Ltd | Scanning Interferometer Using Wedge for Producing Fringes |
-
1988
- 1988-06-14 GB GB8814066A patent/GB2219853A/en not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB732058A (en) * | 1951-08-10 | 1955-06-15 | Leeds & Northrup Co | Improvements in multiple slit spectrograph for direct reading spectrographic analysis |
| GB1150531A (en) * | 1966-06-23 | 1969-04-30 | Barringer Research Ltd | Spectrophotometer |
| GB1195840A (en) * | 1967-01-10 | 1970-06-24 | Barringer Research Ltd | Scanning Interferometer Using Wedge for Producing Fringes |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0452095A1 (en) * | 1990-04-13 | 1991-10-16 | Hughes Aircraft Company | Dispersive holographic spectrometer |
| US7196791B2 (en) | 2000-11-30 | 2007-03-27 | Tomra Systems Asa | Optical detection device |
| US7701574B2 (en) | 2000-11-30 | 2010-04-20 | Tomra Systems Asa | Optically controlled detection device |
| FR2847668A1 (en) * | 2002-11-25 | 2004-05-28 | Jobin Yvon Sas | High resolution spectrometer for application to variable spectral domains, comprises point source sending beam through first optical element, a grism, a second optical element and means of detection |
| WO2004051204A1 (en) * | 2002-11-25 | 2004-06-17 | Horiba Jobin Yvon S.A.S. | Axial spectrometer with high spatial and spectral resolution and variable spectral observation domain |
| CN104729710A (en) * | 2015-04-08 | 2015-06-24 | 武汉邮电科学研究院 | Spectrum analyzer based on liquid crystal on silicon and realization method thereof |
| CN104729710B (en) * | 2015-04-08 | 2017-10-10 | 武汉邮电科学研究院 | A kind of spectroanalysis instrument and its implementation based on liquid crystal on silicon |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8814066D0 (en) | 1988-07-20 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4060327A (en) | Wide band grating spectrometer | |
| US4585349A (en) | Method of and apparatus for determining the position of a device relative to a reference | |
| US6791086B2 (en) | Microspectrometer gas analyzer | |
| US5424826A (en) | Wideband optical micro-spectrometer system | |
| GB2033079A (en) | Infrared interference type film thickness measuring method and instrument | |
| KR940016660A (en) | Thin Film Thickness Measurement Apparatus and Method | |
| EP0341882A2 (en) | Optical sensors | |
| US5880845A (en) | Apparatus for measuring the photometric and colorimetrics characteristics of an object | |
| EP0190310B1 (en) | Spectral analyzer and direction indicator | |
| EP0520463A1 (en) | A high-resolution spectroscopy system | |
| GB2158317A (en) | Automatic focusing | |
| US4944594A (en) | Apparatus and method for measuring dark and bright reflectances of sheet material | |
| WO1988009488A1 (en) | Compact continuous wave wavefront sensor | |
| GB2219853A (en) | A spectral filter | |
| WO2009099409A1 (en) | Optical device | |
| US4577099A (en) | Apparatus for proximity detection of an opaque pattern on a translucent substrate | |
| US4345838A (en) | Apparatus for spectrometer alignment | |
| EP0725375B1 (en) | Apparatus for authenticating documents | |
| US5109251A (en) | Photographic color copying apparatus | |
| US5118926A (en) | Device for separating a beam of white light into a plurality of elementary beams of particular color | |
| WO1996000887A1 (en) | An improved optical sensor and method | |
| JPH0545130A (en) | Method for measuring position and diameter of fiber in fiber bundle | |
| GB2176284A (en) | Device for detecting displacement | |
| JPH04326026A (en) | Spectrophotometer | |
| EP0546869B1 (en) | Spectro-specific diffractive elements as sources of radiation |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |