ATMOSPHERIC EFFECTS ON ELECTRO-OPTICAL SENSORS AND SYSTEMS By Flt Lt Kaniz Fatema

WHAT IS ELECTRO OPTICAL SENSORs Electro-optical sensors are electronic detectors that convert light or a change in light , into a electronic signal It measures the physical quantity of light and then translates it into a form that is readable by an instrument

ELECTRO OPTICAL SENSORs

Meteorological support for ELECTRO OPTICAL Systems Obtain as much information as possible concerning any target or search object, Become as familiar as possible with the target / search area. Understand how meteorological elements, backgrounds, aerosols, and other factors affect TV/NVG, IR/FLIR, and Laser-based sensors. A thorough understanding of the met elements that pertain to an accurate forecast for the area (cloud cover, precipitation, etc.) is important.

Meteorological support for ELECTRO OPTICAL Systems

Detection of targets by ELECTRO OPTICAL Sensors Visual Imaging: The contrast between target and background reflectivity. Near-infrared imaging: Energy reflected off targets designated by lasers. Far-Infrared Imaging: Temperature contrast between the target and background.

Contrast There are mainly three types of contrast. The actual contrast between the target and background as if viewed from the target itself is called inherent contrast. Resulting contrast as viewed from the sensor is known as apparent contrast. The smallest contrast that a sensor or the human eye can detect is called the threshold contrast.

Contrast

extinction Apparent contrast is always less than inherent contrast. As EMR travels from the target scene to the sensor, some of the photons coming from the target are scattered and others are absorbed by the constituents of the air. Both of these processes remove target image photons from their path to the sensor and so degrade the image that the sensor sees. For visible wavelengths, scattering is the predominant cause of extinction, while for IR wavelengths, absorption predominates.

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