Aerosol transmissometer with an in-process transfer standard

Patent metadata

Field	Value
Publication number	US-11204320-B2
Application number	US-202016856370-A
Country	US
Kind code	B2
Filing date	Apr 23, 2020
Priority date	Apr 23, 2020
Publication date	Dec 21, 2021
Grant date	Dec 21, 2021

Abstract

A transmissometer and method for determining a transmissivity of an atmosphere within a chamber. A chamber contains the atmosphere. A light source generates a test beam and a light detector detects the test beam. A periscope is movable between a first position which allows the test beam to pass through the atmosphere in the chamber and into the light detector and a second position in which the test beam is deflected to pass into the light detector without passing through the atmosphere in the chamber. A processor determines the transmissivity of the atmosphere from a transmissivity measurement for the test beam obtained by the light detector when the periscope is in the first position and a transfer standard obtained at the light detector when the periscope is in the second position.

First claim

What is claimed is:

1. A method for determining a transmissivity of an atmosphere within a chamber, comprising:
obtaining, at a light detector, a transmissivity measurement for a test beam that passes through the atmosphere in the chamber and into the light detector during a clear air condition in the chamber;
obtaining a clear air transfer standard at the light detector by deflecting the test beam to be received at the light detector without passing through the atmosphere in the chamber;
introducing a fog into the chamber;
obtaining an in-test transfer standard at the light detector by deflecting the test beam to be received at the light detector without passing through the atmosphere in the chamber; and
determining the transmissivity of the atmosphere in the chamber in having the fog from the transmissivity measurement, clear air transfer standard and in-test transfer standard.

2. The method of claim 1 , further comprising deflecting the test beam by disposing a periscope between a light source of the test beam and the chamber, wherein the periscope redirects the test beam from the light source to the light detector without the test beam entering the chamber.

3. The method of claim 2 , wherein the periscope includes a rail translatable along a track, the rail supporting a first periscope mirror, a second periscope mirror and a neutral density filter between the first periscope mirror and the second periscope mirror.

4. The method of claim 3 , further comprising moving the periscope from a first position out of a path of the test beam to a second position along the track to redirect the test beam.

5. The method of claim 1 , further comprising obtaining the in-test transfer standard measurement while a device under test is in optical communication with the atmosphere of the chamber and determining an operation of the device under test based on the transmissivity.

6. The method of claim 1 , wherein the clear air transfer standard represents a high visibility atmosphere.

7. A transmissometer for determining a transmissivity of an atmosphere, comprising:
a chamber for containing the atmosphere;
a light source for generating a test beam;
a light detector for detecting the test beam;
a periscope movable between a first position which allows the test beam to pass through the atmosphere in the chamber and into the light detector and a second position in which the test beam is deflected to pass into the light detector without passing through the atmosphere in the chamber; and
a processor configured to determine the transmissivity of the atmosphere in the chamber during a fogged condition during a test, the transmissivity being determined from a transmissivity measurement for the test beam obtained by the light detector during a clear air condition in the chamber when the periscope is in the first position, a clear air transfer standard obtained at the light detector when the periscope is in the second position during the clear air condition and an in-test transfer standard obtained at the light detector by deflecting the test beam to be received at the light detector without passing through the atmosphere in the chamber during the fogged condition.

8. The transmissometer of claim 7 , wherein, in the second position, the periscope is between the light source and the chamber.

9. The transmissometer of claim 7 , wherein the periscope further comprises a rail translatable along a track, the rail supporting a first periscope mirror, a second periscope mirror and a neutral density filter between the first periscope mirror and the second periscope mirror.

10. The transmissometer of claim 7 , further comprising a track for moving the periscope from the first position to the second position.

11. The transmissometer of claim 7 wherein the processor is further configured to evaluate a device under test being tested using the in-test transfer standard obtained during the testing of the device under test and determining an operation of the device under test based on the transmissivity, wherein the device under test is in optical communication with the atmosphere in the chamber.

12. The transmissometer of claim 7 , wherein the clear air transfer standard represents a high visibility atmosphere.

13. The transmissometer of claim 7 , further comprising a calibration detector for obtaining a calibration measurement of the test beam, wherein the processor determines a transmissivity of the atmosphere from the calibration measurement and the transmissivity measurement.

Assignees

• Raytheon Co

Inventors

• Millard John A
• Crawford John O

Classifications

• G01N2201/12769

  and adjusting controls, e.g. zero and 100 % · CPC title

• G01N21/534

  by measuring transmission alone, i.e. determining opacity · CPC title

• G01N21/4785

  Standardising light scatter apparatus; Standards therefor · CPC title

• G01N2015/0026

  in gas, e.g. fog · CPC title

• G01N21/59 Primary

  Transmissivity (G01N21/25 takes precedence) · CPC title