John E Didomenico Deceased24117 Pear Tree Cir, Plainfield, IL 60585

5371367, Dec 6, 1994

Apr 13, 1993

8/045211

John DiDomenico - Algonquin IL
James H. Johnson - Woodstock IL
Kenneth W. Michaels - Spring Grove IL
Donald H. Stedman - Denver CO
Dennis L. Smith - Severna Park MD

Envirotest Systems Corp. - Tucson AZ
Colorado Seminary - Denver CO

G01N 2101
G01N 2135

2503385

Apparatus for detecting and measuring relative concentrations of pollutants such as HC, CO and CO. sub. 2 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.