Method and apparatus for far infrared detection
AssigneeThe United States of America as represented by the Secretary of the Army
InventorsEdward J. Efkeman, Elliott Lloyd, Howard K. Dickson, James R. Adamson, Jr.
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Abstract
A modified thermal viewer and method of operating same for detecting and tially analyzing a cloud for the presence of certain chemical compounds, whereby the cloud is viewed through two or more band-pass filters independently and consecutively with each filter responsive to a different band of spectral radiation characteristic of the particular chemical agent of concern.
Claims10
In combination with a thermal viewer with an objective lens and a far infrared detector sensitive to a broad band of infrared frequencies, a subsystem for distinguishing one cloud of a first gaseous compound from an alternative cloud formed from a second gaseous compound when backlighted by a substantially uniform spectral distribution of light in the far infrared, comprising:
- a filter wheel mounted in said viewer between said objective lens and said detector having at least three apertures therein;
- one of said apertures being arranged to pass all far infrared frequencies in said broad band;
- each remaining aperture containing a filter which transmits only one of a group of different narrow bands of frequencies;
- and
- a stepping motor means mounted on said viewer to move said filter wheel so that said apertures are sequentially centered on the optical axis of said lens, the stepping period of said motor means being less than one tenth of a second.
The method of distinguishing one cloud of gas having a first chmeical structure from a second cloud of gas having a different chemical structure, comprising the steps of:
- viewing a portion of said one cloud for at least one second against a background of substantially uniform spectral radiation in the range of 5.6 to 22 microns with a thermal viewer having a substantially uniform response over said range and a first filter rejecting all but a narrow band of radiation within said range;
- and
- substituting a second filter with a different pass band for said first filter in less than one tenth of a second.
Dependencies are inferred from the claim text.