Remote sensor device for monitoring motor vehicle exhaust systems

• US 5,371,367 A
• Filed: 04/13/1993
• Issued: 12/06/1994
• Est. Priority Date: 04/13/1993
• Status: Expired due to Fees

• Current Assignee: Colorado Seminary, Envirotest Systems Corporation (Stone Rivet, Inc.)
• Original Assignee: Colorado Seminary, Envirotest Systems Corporation (Stone Rivet, Inc.)
• Inventors: DiDomenico, John, Smith, Dennis L., Johnson, James H., Michaels, Kenneth W., Stedman, Donald H.
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Glick, Edward J.
• Application Number:
  US08/045,211
• Time in Patent Office: 602 Days
• Field of Search: 250/339, 250/338.5, 250/252.1, 356/438, 356/437, 356/152
• US Class Current: 250/338.5
• CPC Class Codes: G01N 2021/1793 Remote sensing
• CPC Class Codes: G01N 2021/3513 Open path with an instrumental source
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis

Abstract

Apparatus for detecting and measuring relative concentrations of pollutants such as HC, CO and CO₂ in the exhaust emissions from passing vehicles includes an infrared (IR) beam source for directing an IR beam through a vehicle'"'"'s exhaust plume and a detector disposed on one side of a roadway and a lateral transfer mirror (LTM) disposed on the other side of the roadway for lateral reflecting of the IR beam back through the vehicle'"'"'s exhaust plume and onto the detector. The LTM allows for close spacing and precise alignment between the emitted and reflected beam paths and permits the IR beam source and detector to be disposed in a single module. Compensation for variation in a range of vehicle operating conditions is provided by adjustable, computer-controlled potentiometers, while audio and/or visible light feedback of the detected IR signal allows a single operator to precisely align the optical components of the apparatus. The IR detector module includes a rotating mirror arrangement for directing the reflected IR beam in a pulsed manner onto a plurality of spaced detector elements, each adapted for detecting a specific pollutant, with the detector elements calibrated with each detected IR pulse to reduce errors arising from circuit drift.

Claims

1. Apparatus for monitoring pollutant concentration in an exhaust plume of a vehicle traveling on a roadway by directing an infrared (IR) beam through said exhaust plume, said apparatus comprising:

IR beam source means disposed on a first side of the roadway for directing an emitted IR beam through the exhaust plume of a vehicle;

lateral transfer reflecting means including first and second spaced, generally planar, mirrors disposed on a second, opposed side of the roadway for receiving and redirecting said emitted IR beam as a reflected IR beam across the roadway in a second, opposed direction, wherein said reflected IR beam is displaced from said emitted IR beam, and wherein said first and second mirrors form an integral structure;

IR detection means disposed on said first side of the roadway adjacent said IR beam source means for receiving said reflected IR beam and determining the pollutant concentration in the vehicle'"'"'s exhaust plume; and

further including a laser beam source and detector disposed adjacent said IR beam source and said IR detection means for directing a laser beam across the roadway onto said lateral transfer reflecting means and for detecting alignment of said lateral transfer reflecting means with said IR beam source and said IR detection means, and wherein said lateral transfer reflecting means further includes a generally planar panel coupled to and disposed intermediate said first and second mirrors for use as a target for said laser beam.

2. The apparatus of claim 1 wherein said first and second mirrors are generally transverse.

3. The apparatus of claim 2 wherein said IR beam source means and said IR detection means are arranged in mutual proximity and are disposed in respective modules.

4. The apparatus of claim 3 wherein said reflected IR beam is horizontally spaced on the order of 8" from said emitted IR beam.

5. The apparatus of claim 1 wherein said IR beam source, said IR detection means and said lateral transfer reflecting means are disposed 10"-18" above the roadway.

6. The apparatus of claim 1 further comprising video recording means for recording a video image of a license plate of a vehicle passing between said IR beam source and IR detection means and said lateral transfer reflecting means on the roadway.

7. The apparatus of claim 6 wherein said video recording means includes a digitized still image camera and disc file for recording a digital image of a vehicle'"'"'s license plate.

9. The apparatus of claim 7 wherein said indicator means includes a light source.

8. Apparatus for detecting alignment of optical components in an infrared absorption spectroscopy system for use in measuring the concentration of pollutants in a moving motor vehicle exhaust plume, wherein an infrared (IR) beam is directed across a roadway through said exhaust plume and interacts with pollutants therein, said apparatus comprising:

a laser for producing an alignment beam and arranged on one side of the roadway;

a reflector for reflecting the IR beam and the alignment beam and being arranged on a side of the roadway opposite said one side;

detector means arranged on said one side of the roadway and proximate said laser for receiving the alignment beam after transit across the roadway and reflection back by said reflector for providing an analog signal representing the amplitude of the received alignment beam;

analog-to-digital (A/D) converting means for transforming said analog signal to a digital signal comprised of a series of pulses, wherein a pulse repetition frequency (PRF) of said digital signal represents the amplitude of the received alignment beam; and

indicator means coupled to said (A/D) converting means and responsive to said digital signal for turning on and off at said PRF and providing a pulsed output signal representing the amplitude of the received alignment beam, wherein the PRF of said pulsed output signal increases as the optical components including said reflector and detector means are more precisely aligned, and wherein said A/D converting means increases said PRF so as to provide a continuous digital signal when the amplitude of the received alignment beam exceeds a predetermined signal level resulting in a continuous output signal by said indicator means representing alignment of the optical components.

10. The apparatus of claim 8 wherein said indicator means includes an audio source.

11. The apparatus of claim 10 wherein said audio source is a beeper.