Introduction to Radiometry | Home | Current Projects | Products | Tools | Tutorials | About | Contact Us | Employment |
The tutorials on this website discuss the current approach to the acquisition of infrared (IR), visible (Vis), and ultraviolet (UV) radiometric plume radiation information during the testing of propulsion systems. The intent is to provide a brief summary of the fundamentals of quantitative radiometry, and to show the current infrared (IR), visible (Vis), and ultraviolet (UV) measurement and data handling capabilities, primarily by summarizing and listing typical instrumentation used for measurements.

For a thorough review of the fundamentals of radiometry see the Tactical Missile Signatures Measurement Standards Handbook, The Infrared Handbook and papers such as "Infrared Target and Background Radiometric Measurements--Concepts, Units, and Techniques" by Gilbert Kelton, George Zissis, Ely Bell, et. al. (Applied Physics, 1963, Vol. 3, Pergamon Press Ltd., Printed in Great Britain). A brief overview of radiometric instrumentation, data handling and calibration techniques is included herein. A number of summary type charts, tables, and figures are included. The first is a table with a summary of radiometric quantities of interest, followed by Figure 1, a sketch with the essentials of a radiometric measurement.

RADIOMETRIC UNITS
Name Symbol Dimensions Units Description Illustration
(Spectral) Radiant Energy Qλ Power x time
(per wavelength, wavenumber, etc.)		 (Watt sec) / (micron) Q = number of photons(/dλ)
(Spectral) Radiant Power or Flux Φλ Power
(per wavelength, wavenumber, etc.)		 Watts / (micron) Φλ = d(2)Q / dt (dλ)
(Spectral) Radiant Intensity Iλ Power per solid angle
(per wavelength, wavenumber, etc.)		 Watts /
[sr (micron)]		 Iλ = d(2)Φ / dΩ (dλ)
(Spectral) Radiance Lλ Power per area
of active region solid angle
(exiting)
a source quantity		 Watts /
[m2 sr (micron)]		 Lλ = d2(3)Φ /
[cosθ dA dΩ (dλ)]
(Spectral) Irradiance Eλ Power per area
(incident)
a sensor quantity		 Watts /
[m2 (micron)]		 Eλ = d(2)<Φ / dA (dλ)
(Spectral) Exitance Mλ Power per area
of active region
(exiting)
a source quantity		 Watts /
[m2 (micron)]		 Mλ = d(2)Φ / dA (dλ)



Figure 1. Measurement Essentials

Figure 1 shows the essentials of a radiometric measurement. As can be seen, a number of measurements can be considered. The radiant output of the source is often the quantity sought; however, the source may produce a known output and one of the other quantities mentioned in the figure might be in question. The measurement may be required to determine the emissivity, transmittance, or reflectance of the element identified as the source. The background may include a reference source and the transmission of the atmosphere might be the unknown. In any case all of the shown terms must be considered during the measurement process to produce a valid result.

Copyright © 2003 - Pender Technology
All Rights Reserved