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An active (laser-illuminated) imaging system is described that is suitable for use in backscatter absorption gas imaging (BAGI). A BAGI imager operates by imaging a scene as it is illuminated with radiation that is absorbed by the gas to be detected. Gases become "visible" in the image when they att

An active (laser-illuminated) imaging system is described that is suitable for use in backscatter absorption gas imaging (BAGI). A BAGI imager operates by imaging a scene as it is illuminated with radiation that is absorbed by the gas to be detected. Gases become "visible" in the image when they attenuate the illumination creating a shadow in the image. This disclosure describes a BAGI imager that operates in a linescanned manner using a high repetition rate pulsed laser as its illumination source. The format of this system allows differential imaging, in which the scene is illuminated with light at least 2 wavelengths--one or more absorbed by the gas and one or more not absorbed. The system is designed to accomplish imaging in a manner that is insensitive to motion of the camera, so that it can be held in the hand of an operator or operated from a moving vehicle.

대표청구항 ▼

An active (laser-illuminated) imaging system is described that is suitable for use in backscatter absorption gas imaging (BAGI). A BAGI imager operates by imaging a scene as it is illuminated with radiation that is absorbed by the gas to be detected. Gases become "visible" in the image when they att

An active (laser-illuminated) imaging system is described that is suitable for use in backscatter absorption gas imaging (BAGI). A BAGI imager operates by imaging a scene as it is illuminated with radiation that is absorbed by the gas to be detected. Gases become "visible" in the image when they attenuate the illumination creating a shadow in the image. This disclosure describes a BAGI imager that operates in a linescanned manner using a high repetition rate pulsed laser as its illumination source. The format of this system allows differential imaging, in which the scene is illuminated with light at least 2 wavelengths--one or more absorbed by the gas and one or more not absorbed. The system is designed to accomplish imaging in a manner that is insensitive to motion of the camera, so that it can be held in the hand of an operator or operated from a moving vehicle. ived via said n light-transit sections, by each and every one of said s optical sensors, and obtaining a natural number n×s of total responses for the received light; and (c) calculating a natural number m of spectral irradiances for m kinds of wavelengths as a spectral irradiance distribution of the light, based on one or more linear formulae established between said optical characteristic coefficients, said spectral sensitivities, said n×s responses for the light, and said spectral irradiance distribution of the light. 2. A method of measuring a spectral irradiance distribution of light according to claim 1, wherein: said optical sensors and said light-transit sections are arranged in such a manner that the number n×s of said responses for the light detected by said optical sensors is equal to or larger than the number m of said spectral irradiances to be calculated based on said linear formulae; and said m spectral irradiances are calculated by directly solving said linear formulae. 3. A method of measuring a spectral irradiance distribution of light according to claim 1, wherein: said optical sensors and said light-transit sections are arranged in such a manner that the number n×s of said responses for the light detected by said optical sensors is smaller than the number m of said spectral irradiances to be calculated based on said linear formulae; and said m spectral irradiances are calculated by solving said linear formulae under a predetermined constraint. 4. A method of measuring a spectral irradiance distribution according to claim 3, wherein said predetermined constraint is such that said spectral irradiance distribution of the light is a positive value. 5. A method of measuring a spectral irradiance distribution according to claim 3, wherein said predetermined constraint is such that said spectral irradiance distribution of the light is expressed by a linear combination of predetermined spectral irradiance distributions. 6. A method of measuring a spectral irradiance distribution according to claim 4, wherein said predetermined constraint is such that said spectral irradiance distribution of the light is expressed by a linear combination of predetermined spectral irradiance distributions. 7. A method of measuring a spectral irradiance distribution according to claim 5, wherein another constraint is added to said predetermined constraint, said another constraint being such that: said spectral irradiance distribution of the light is a positive value; and said spectral irradiance distribution of the light is expressed by linearly combining said predetermined spectral irradiance distribution with a non-negative coefficient. 8. A method of measuring a spectral irradiance distribution according to claim 6, wherein another constraint is added to said predetermined constraint, said another constraint being such that: said spectral irradiance distribution of the light is a positive value; and said spectral irradiance distribution of the light is expressed by linearly combining said predetermined spectral irradiance distribution with a non-negative coefficient. 9. A method of measuring a spectral irradiance distribution according to claim 5, wherein said predetermined spectral irradiance distribution is a principal component of estimated spectral irradiance distributions of one or more light sources. 10. A method of measuring a spectral irradiance distribution according to claim 6, wherein said predetermined spectral irradiance distribution is a principal component of estimated spectral irradiance distributions of one or more light sources. 11. A method of measuring a spectral irradiance distribution according to claim 7, wherein said predetermined spectral irradiance distribution is a principal component of estimated spectral irradiance distributions of one or more light sources. 12. A method of measuring a spectral irradiance distribution according to claim 8, wherein said predetermined spectr al irradiance distribution is a principal component of estimated spectral irradiance distributions of one or more light sources. 13. A method of measuring a spectral irradiance distribution according to claim 5, wherein said predetermined spectral irradiance distribution is a linear combination with principal components of estimated spectral irradiance distributions of one or more light sources. 14. A method of measuring a spectral irradiance distribution according to claim 6, wherein said predetermined spectral irradiance distribution is a linear combination with principal components of estimated spectral irradiance distributions of one or more light sources. 15. A method of measuring a spectral irradiance distribution according to claim 7, wherein said predetermined spectral irradiance distribution is a linear combination with principal components of estimated spectral irradiance distributions of one or more light sources. 16. A method of measuring a spectral irradiance distribution according to claim 8, wherein said predetermined spectral irradiance distribution is a linear combination with principal components of estimated spectral irradiance distributions of one or more light sources. 17. A method of measuring a spectral irradiance distribution according to claim 5, wherein said predetermined spectral irradiance distribution an estimated spectral irradiance of a light source. 18. A method of measuring a spectral irradiance distribution according to claim 6, wherein said predetermined spectral irradiance distribution is an estimated spectral irradiance of a light source. 19. A method of measuring a spectral irradiance distribution according to claim 7, wherein said predetermined spectral irradiance distribution is an estimated spectral irradiance of a light source. 20. A method of measuring a spectral irradiance distribution according to claim 8, wherein said predetermined spectral irradiance distribution is an estimated spectral irradiance of a light source. 21. A method of measuring a spectral irradiance distribution according to claim 5, further comprising: preparing a plurality of sets of said predetermined spectral irradiance distributions; calculating said spectral irradiance distributions of the light respectively using the prepared plural sets of spectral irradiance distributions; and selecting, among a plurality of the calculated spectral irradiance distributions of light, one spectral irradiance distribution whose error in said linear formulae is minimal. 22. A method of measuring a spectral irradiance distribution according to claim 6, further comprising: preparing a plurality of sets of said predetermined spectral irradiance distributions; calculating said spectral irradiance distributions of the light respectively using the prepared plural sets of spectral irradiance distributions; and selecting, among a plurality of the calculated spectral irradiance distributions of light, one spectral irradiance distribution whose error in said linear formulae is minimal. 23. A method of measuring a spectral irradiance distribution according to claim 7, further comprising: preparing a plurality of sets of said predetermined spectral irradiance distributions; calculating said spectral irradiance distributions of the light respectively using the prepared plural sets of spectral irradiance distributions; and selecting, among a plurality of the calculated spectral irradiance distributions of light, one spectral irradiance distribution whose error in said linear formulae is minimal. 24. A method of measuring a spectral irradiance distribution according to claim 8, further comprising: preparing a plurality of sets of said predetermined spectral irradiance distributions; calculating said spectral irradiance distributions of the light respectively using the prepared plural sets of spectral irradiance distributions; and selecting, among a plurality of the calculated spectral irradiance distributions of ligh