GB2180639A - Determining atmospheric materials using lidar - Google Patents
Determining atmospheric materials using lidar Download PDFInfo
- Publication number
- GB2180639A GB2180639A GB08518554A GB8518554A GB2180639A GB 2180639 A GB2180639 A GB 2180639A GB 08518554 A GB08518554 A GB 08518554A GB 8518554 A GB8518554 A GB 8518554A GB 2180639 A GB2180639 A GB 2180639A
- Authority
- GB
- United Kingdom
- Prior art keywords
- constituent
- radiation
- atmosphere
- spectrum
- lidar
- 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.)
- Granted
Links
- 239000000463 material Substances 0.000 title claims description 5
- 230000005855 radiation Effects 0.000 claims abstract description 31
- 238000001228 spectrum Methods 0.000 claims abstract description 28
- 239000000470 constituent Substances 0.000 claims abstract description 24
- 239000011358 absorbing material Substances 0.000 claims abstract description 12
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 claims description 28
- 238000009826 distribution Methods 0.000 claims description 20
- 235000010269 sulphur dioxide Nutrition 0.000 claims description 14
- 239000004291 sulphur dioxide Substances 0.000 claims description 14
- 238000010521 absorption reaction Methods 0.000 claims description 8
- 239000000779 smoke Substances 0.000 claims description 8
- 230000005540 biological transmission Effects 0.000 claims description 2
- 230000001419 dependent effect Effects 0.000 claims description 2
- 238000001514 detection method Methods 0.000 claims description 2
- 230000003993 interaction Effects 0.000 claims description 2
- 238000000034 method Methods 0.000 claims description 2
- POFWRMVFWIJXHP-UHFFFAOYSA-N n-benzyl-9-(oxan-2-yl)purin-6-amine Chemical compound C=1C=CC=CC=1CNC(C=1N=C2)=NC=NC=1N2C1CCCCO1 POFWRMVFWIJXHP-UHFFFAOYSA-N 0.000 claims description 2
- HGCGQDMQKGRJNO-UHFFFAOYSA-N xenon monochloride Chemical compound [Xe]Cl HGCGQDMQKGRJNO-UHFFFAOYSA-N 0.000 claims description 2
Classifications
-
- 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
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
-
- 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
- G01N2021/3513—Open path with an instrumental source
-
- 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
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
- G01N2021/392—Measuring reradiation, e.g. fluorescence, backscatter
-
- 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
- G01N21/3518—Devices using gas filter correlation techniques; Devices using gas pressure modulation techniques
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Analytical Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Optics & Photonics (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Optical Radar Systems And Details Thereof (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
A lidar arrangement includes a laser 1 located between two mirrors 2 and 3, one of which 2 is partially transmissive to permit laser radiation to pass through it to form the transmitted beam of the lidar. A cell 4 contains an absorbing material is be moved into and out of the path of the laser radiation to produce two spectra. The absorbing material is a constituent which it is wished to monitor in the atmosphere. The transmitted lidar beam is scattered from the atmosphere and by observing the amplitude of the received scattered radiation for both spectra the amount of constituent in the atmosphere, and its location, may be ascertained. <IMAGE>
Description
SPECIFICATION
Lidars
This invention relates to lidars and more particularly to apparatus fortuning the spectrum in a differential lidarsystem. Lidarisan acronym for light detection and ranging. A lidaris a device for detecting and observing such things as cloud patterns or pollution in the atmosphere by directing a laser beam in the desired direction and observing the returned spectrum.
A differential lidar is one which transmitstwo signals at different distribution of wavelengths and by comparing the responses is able to detect a particular constituent of the atmosphere, for example, by using a differential lidar it is possible to detect whether or not sulphur dioxide is present in smoke.
Previously, the required distributions have been selected by means of a diffraction grating or a prism within the laser cavity. However, in wavelength selection by these methods, alignment is critical and the apparatus is difficult to maintain in the aligned state necessary for its successful operation.
This invention seeks to provide an improved lidar apparatus.
According to this invention there is provided lidar apparatus comprising meansformoving avolumeof absorbing material into and out ofthe path of laser radiation thereby producing a first spectrum which includes a certain wavelength distribution and a second spectrum in which the wavelength distribution has been modified by absorption bytheabsorb- ing material, the wavelength distribution being such as to interact with a constituent of an atmosphere, whereby the constituent can be monitored. Thus lidar apparatus in accordance with the invention may be made more robust and insensitive to misalignmentthan previously known apparatus. The interaction ofthe radiation at the chosen wavelength distribution with the constituent ofthe atmosphere is by absorption.Preferably,the absorbing material includes the constituent of the atmosphere to be monitored, thus enabling the desired first and second spectra to be easily and quickly produced, and advantageously the absorbing material is the constituent.
The invention is now further described by way of example with reference to the accompanying drawings in which:
Figure 1 schematically illustrates lidar apparatus in accordance with the invention; and
Figures2a, 2b, 3a and 3á illustrate the operation of the apparatus of Figure 1.
With reference to Figure 1, a lidar arrangement includes a xenon chloride laser 1 which is located between two mirrors 2 and 3, one of which 2 is partially transmissive to permit laser radiation to pass through itto form the transmitted beam of the lidar.
Acell 4 containing sulphurdioxide gas is also inclu- ded in the arrangement and is movable into and out ofthe path of the laser radiation as indicated by arrow5 to modify the wavelength distribution of the transmitted beam.
When the cell 4 is in the position shown in full lines the spectrum ofthe transmitted laser beam is that shown diagramatically in Figure 2a and includes radiation distributed about a peak at the wavelength X1.
When the cell 4 is in the position indicated by the broken lines such that it is interposed in the path of the laser radiation the spectrum of the radiation transmitted isthatshown in Figure2b.Thesulphur dioxide contained in the cell 4 absorbs radiation distributed about the wavelength X1.
To observe, say, whether sulphur dioxide is present in smoke emanating froma chimney, the output laser radiation is transmitted in the appropriate direction and scattering from the atmosphere is obse rved using a telescope (not shown) aligned along- sidethe laser 1. The amplitude ofthe signal received at the telescope when the spectrum of Figure 2a is transmitted is shown in Figure 3a, and thatforthe spectrum of Figure 2b is shown in Figure 3b. The cell 4is moved between its two positions a numberof times to obtain average responses for both ofthe output spectra, shown in Figures 2a and 2b.
The response shown in Figure 3b includes a peak6, received at a time t1 afterthe transmission of a pulse of laser radiation, which is dueto the presence of smoke in the atmosphere which returns a relatively large amount ofthe radiation. The received radiation is unaffected by the amount of sulphur dioxide present, since radiation at X1 has been removed by the cell4.
The response shown in Figure 3a includes a component 7 which is scattered from the smoke, as in
Figure 3b, but also includes an additional component which has an amplitude which is dependent on the amount of sulphur dioxide present. If a small amount is present the peak8 is largerthan if a larger amount exists, when the peak 9 is reduced because of absorption by the sulphur dioxide.
Thus by normalising the responses shown in Figures 3a and 3b and substracting one from the other the amount of sulphur dioxide present may be monitored, and also its location.
If it is desired to monitor another constituent of the atmosphere, the cell 4 is arranged to contain that constituent to alter the spectra of the transmitted laser beam as desired.
1. Lidarapparatuscomprising means for moving avolume ofabsorbing material into and outofthe path of laser radiation thereby producing a first spectrum which includes a certain wavelength distribution and a second spectrum in which the wave- length distribution has been modified by absorption by absorbing material, the wavelength distribution being such as to interact with a constituent of an atmosphere whereby the constituent can be monitored.
2. Lidarapparatus as claimed in claim 1,and wherein the absorbing material includes the constituent.
3. Lidar apparatus as claimed in claim 2 and wherein the absorbing matsrie! it, the cnstituent.
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (4)
1. Lidarapparatuscomprising means for moving avolume ofabsorbing material into and outofthe path of laser radiation thereby producing a first spectrum which includes a certain wavelength distribution and a second spectrum in which the wave- length distribution has been modified by absorption by absorbing material, the wavelength distribution being such as to interact with a constituent of an atmosphere whereby the constituent can be monitored.
2. Lidarapparatus as claimed in claim 1,and wherein the absorbing material includes the constituent.
3. Lidar apparatus as claimed in claim 2 and wherein the absorbing matsrie! it, the cnstituent.
4. Lidar apparatus substantially as illustrated in and described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8518554A GB2180639B (en) | 1985-07-23 | 1985-07-23 | Lidars |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8518554A GB2180639B (en) | 1985-07-23 | 1985-07-23 | Lidars |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8518554D0 GB8518554D0 (en) | 1985-08-29 |
| GB2180639A true GB2180639A (en) | 1987-04-01 |
| GB2180639B GB2180639B (en) | 1989-08-09 |
Family
ID=10582703
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8518554A Expired GB2180639B (en) | 1985-07-23 | 1985-07-23 | Lidars |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2180639B (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3788742A (en) * | 1971-06-24 | 1974-01-29 | Westinghouse Electric Corp | Gas monitoring system |
| US3998557A (en) * | 1974-06-03 | 1976-12-21 | Massachusetts Institute Of Technology | Gas detector |
| GB2060873A (en) * | 1979-10-01 | 1981-05-07 | Hartmann & Braun Ag | Photoelectric gas analysis device |
| US4425503A (en) * | 1980-08-05 | 1984-01-10 | The United States Of America As Represented By The Secretary Of The Army | Method for detecting the presence of a gas in an atmosphere |
-
1985
- 1985-07-23 GB GB8518554A patent/GB2180639B/en not_active Expired
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3788742A (en) * | 1971-06-24 | 1974-01-29 | Westinghouse Electric Corp | Gas monitoring system |
| US3998557A (en) * | 1974-06-03 | 1976-12-21 | Massachusetts Institute Of Technology | Gas detector |
| GB2060873A (en) * | 1979-10-01 | 1981-05-07 | Hartmann & Braun Ag | Photoelectric gas analysis device |
| US4425503A (en) * | 1980-08-05 | 1984-01-10 | The United States Of America As Represented By The Secretary Of The Army | Method for detecting the presence of a gas in an atmosphere |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8518554D0 (en) | 1985-08-29 |
| GB2180639B (en) | 1989-08-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |