Method and apparatus for selecting a filter for a remote sensing device
AssigneeEnvirotest Systems Corp.
InventorsJohn D. Didomenico, Craig S. Rendahl
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Abstract
The present invention relates to a system and method for selecting a detection bandwidth centered about a characteristic wavelength of the species to be detected and such that the detection of contaminants is greatly reduced. Contaminants such as pollutants, dust and water are some of the examples of undesirable substances which may be detected by RSD. By selecting the appropriate bandwidth in accordance with this invention, the detection of a desired substance can be separated from the undesirable detection of contaminants.
Claims9
A method for selecting a detection bandwidth centered about a center wavelength for at least one constituent of a vehicle emission, said method comprising the steps of:
- (a) determining a constituent characteristic wavelength of at least one constituent of the vehicle's emission to be detected;
- (b) determining a bandwidth about the constituent characteristic wavelength within which said at least one constituent absorbs radiation;
- (c) determining one or more contaminants which may be encountered by radiation employed to detect said at least one constituent in a vehicle emission plume;
- (d) determining a contaminant characteristic wavelength of said at least one contaminant;
- (e) determining a bandwidth about the contaminant characteristic wavelength of said at least one contaminant within which said at least one contaminant absorbs radiation;
- (f ) comparing the constituent characteristic wavelength and the contaminant characteristic wavelength and the bandwidth about the constituent characteristic wavelength of said at least one constituent and the bandwidth about the contaminant characteristic wavelength of said at least one contaminant;
- and
- (g) selecting a detection bandwidth based on said comparison in step (f) by shifting the center wavelength of the detection bandwidth away from the constituent characteristic wavelength and adjusting the size of the detection bandwidth.
A method for selecting a radiation filter for detection of at least one constituent of a vehicle emission, said method comprising the steps of:
- (a) determining a constituent characteristic wavelength of at least one constituent of the vehicle's emission to be detected;
- (b) determining a bandwidth about the constituent characteristic wavelength within which said at least one constituent absorbs radiation;
- (c) determining one or more contaminants which may be encountered by radiation employed to detect said at least one constituent in a vehicle emission plume;
- (d) determining a contaminant characteristic wavelength of said at least one contaminant;
- (e) determining a bandwidth about the contaminant characteristic wavelength of said at least one contaminant within which said at least one contaminant absorbs radiation;
- (f ) comparing the constituent characteristic wavelength and the contaminant characteristic wavelength and the bandwidth about the constituent characteristic wavelength of said at least one constituent and the bandwidth about the contaminant characteristic wavelength of said at least one contaminant;
- (g) selecting a detection bandwidth based on said comparison in step (f) by shifting the center wavelength of the detection bandwidth away from the constituent characteristic wavelength and adjusting the size of the detection bandwidth;
- and
- (h) selecting a radiation filter which permits passage of radiation within the detection bandwidth and filters out substantially all other radiation.
A method for detecting one or more constituents of a vehicle exhaust emission, said method comprising the steps of:
- (a) emitting radiation from a radiation source;
- (b) passing said radiation through a vehicle exhaust emission;
- (c) filtering said radiation which passed through said vehicle's exhaust emission with a radiation filter which is selected to permit a bandwidth centered about a center wavelength of 3.45 μm to pass through to a detector, said bandwidth being selected such that the center wavelength is a characteristic wavelength of a hydrocarbon to be detected and there is substantially no absorption of radiation within said selected bandwidth by one or more contaminants which may be encountered by said radiation;
- (d) detecting said filtered radiation;
- (e) determining the concentration of the the hydrocarbon within the vehicle's exhaust emission.
Dependencies are inferred from the claim text.