GAS CONCENTRATION MEASUREMENT DEVICE USING STIMULATED RAMAN SCATTERING

• US 3,802,777 A
• Filed: 04/17/1973
• Issued: 04/09/1974
• Est. Priority Date: 04/19/1972
• Status: Expired due to Term

• Current Assignee: Jean-Pierre E. Taran, Pierre R. Regnier
• Original Assignee: Jean-Pierre E. Taran, Pierre R. Regnier
• Inventors: Regnier, Pierre R., Taran, Jean-Pierre E.
• Primary Examiner(s): Wilbert, Ronald L.
• Assistant Examiner(s): McGraw, V. P.
• Application Number:
  US05/351,969
• Time in Patent Office: 357 Days
• Field of Search: 356/75,85
• US Class Current: 356/301
• CPC Class Codes: G01J 3/44 Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
• CPC Class Codes: H01S 3/305 in a gas

Abstract

Device for detecting a given molecular gas, measuring its concentration and visualizing its concentration pattern in an aerodynamic flow, a flame, or in the atmosphere. A laser beam and a Stokes beam having frequencies differing by the vibrational frequency of the gas are sent parallel or focussed onto a sample of the gas by means of an optical system. An anti-Stokes beam is thus produced which depends on the concentration of the gas at the focus of the optical means and this beam is imaged on any convenient displaying means. The optical system has a varying focal length which allows the plotting point by point of the gas concentration within a sample volume.

Claims

1. Device for detecting a predetermined molecular gas and measuring and visualizing the concentration pattern thereof, said gas having a given vibrational frequency, said device using a stimulated Raman scattering process and comprising a pulse laser transmitting a first coherent laser beam having a first frequency, means for transmitting a second coherent light beam colinear with said first beam and having a second frequency equal to the difference of said first frequency and said vibrational frequency, optical means for projecting said colinear first and second beams onto a sample of said molecular gas and focussing the said beams onto a selected region of said sample, whereby an antiStokes beam colinear with said first and second beams is generated in said sample, means for collecting said antiStokes beam from said sample selected region and means controlled by said collecting means for visualizing the concentration pattern of said molecular gas in said region.

2. Device for detecting a predetermined molecular gas and measuring and visualizing the concentration pattern thereof, said gas having a given vibrational frequency, said device using a stimulated Raman scattering process and comprising a pulse ruby laser transmitting a first coherent laser beam having a first frequency, a dye laser triggered synchronously with said ruby laser, transmitting a second coherent light beam colinear with said first beam and having a second frequency equal to the difference of said first frequency and said vibrational frequency, optical means for superimposing said first and second beams and projecting them onto a sample of said molecular gas and focussing the same beams onto a selected region of said sample, whereby an antiStokes beam colinear with said first and second beam is generated in said sample, means for collecting said antiStokes beam from said sample selected region and means controlled by said collecting means for visualizing the concentration pattern of said molecular gas in said region.

3. Device for detecting a predetermined molecular gas and measuring and visualizing the concentration pattern thereof, said gas having a given vibrational frequency, said device using a stimulated Raman scattering process and comprising a pulse laser transmitting a first coherent laser beam having a first frequency, a tank containing said predetermined molecular gas, first optical means for projecting said first beam onto said tank whereby a second coherent light beam colinear with said first beam and having a second frequency equal to the difference of said first frequency and said vibrational frequency is produced, second optical means for projecting said colinear first and second beams onto a sample of said molecular gas and focussing the said beams onto a selected region of said sample whereby an antiStokes beam colinear with said first and second beam is generated in said sample, means for collecting said antiStokes beam from said sample selected region and means controlled by said collecting means for visualizing the concentratIon pattern of said molecular gas in said region.

4. System for measuring the concentration of a molecular atmospheric gas along a rectilinear path between a transmitter station and a receiver station, said gas having a given vibrational frequency, said system using a stimulated Raman scattering process and comprising in the transmitter station a pulse laser transmitting towards said receiver station a first coherent laser beam having a first frequency, means for transmitting a second coherent light beam colinear with said first beam and having a second frequency equal to the difference of said first frequency and said vibrational frequency, variable focal length optical means for successively focussing said colinear first and second beams onto selected points of said path, means for varying the focal length of said optical means, whereby an antiStokes beam colinear with said first and second beams is successively generated in said atmospheric gas located at said points and in the receiver station means for collecting said antiStokes beam from said selected point and means controlled by said focal length varying means for measuring the concentration of said molecular gas at the different points of said path.

5. Device for visualizing the concentration of a molecular gas in an aerodynamic flow, said gas having a given vibrational frequency, said device using a stimulated Raman scattering process and comprising a pulse laser transmitting a first coherent laser beam having a first frequency, means for transmitting a second coherent light beam colinear with said first beam and having a second frequency equal to the difference of said first frequency and said vibrational frequency, a flow containing said molecular gas, first optical means for sending parallel into said flow said first and second beams, whereby an antiStokes beam colinear with said first and second beams is generated from said gas in said flow, a photographic plate, second optical means for projecting a selected plane of said gas in said flow onto said photographic plate and filtering means associated with said projecting optical means for blocking said first and second frequencies and passing the frequency of said antiStokes beam.