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5 R eferences

Non-thermal radiators, such as discharge lamps (which can be characterised by their non-continuous spectral energy distribution), and narrow-band emitters can only be measured with precision by means of the spectralprocedure.When compared to three-filter colorimeters, spectroradiometers do have their limitations, in terms of speed ofmeasurement, price and portability. B illmeyer, Fred W (1981). Principles of color technology—2nd Edition. Wiley & Sons, New York. H utson, Geoffrey, H. (1990). Colour Television — 2nd Edition. McGraw-Hill Book Company Europe, England. T he Photonics Dictionary — A Four-Book Set (1993). United States of America. J oseph B. Murdoch. Illumination Engineering — From Edison’s lamp to the laser.Macmillian Publishing Company, England.

3.5 S UMMAR Y

If precise measurement of light is required, the spectroradiometric method is the most ideal and comprehensive method as it records the spectral characteristics of light and further processes themmathematically to obtain radiometric, spectroradiometric, photometric, and colorimetric data.When portability, speed of measurement, and cost of investment, is of priority, filter photometers arestill preferred. However, one should have a good understanding of the f1’ value of the photometer andits calibration method. This information is important to ascertain whether the photometer is appropriateto measure the light source under test, considering its spectral energy distribution.Finally, one should choose an instrument which make direct measurements of light characteristics, suchas luminance, illuminance, luminous intensity, luminous flux and should not attempt any form of conversionsacross measurement geometries. A good understanding of the measurable characteristics of light, and exactly which of those characteristicsof light need to be quantified for a particular situation, will ensure that the radiometric and/or photometriccharacteristics of an application are described correctly.This publication makes no claim to completeness but simply describes what the user needs to knowabout measurement of light. The pointers described are based on problems which are frequentlymentioned in discussion between suppliers and customers. D . Allan Roberts. Radiometry/Photometry Terms. The Photonics Design and Applications Handbook 1993,United States of America. D aniel C. McCarthy. Integrating Sphere Aids Absolute Calibration of Lamps.Photonics Spectra—December 1998, United States of America. R ichard Distl. Measure What You See. Photonics Spectra—May 2000, United States of America. I an K. Edwards. Counting Coup — Photometry: Origin of the science to applying handheld equipment.LD&A — December 1993. C larence E. Rash and Everette McGowin III. Measuring Light. Information Display 9/96. SID 1996. K enneth A. Miller. Colorimetry: Methods and Tools. The Photonics Design and Applications Handbook 1993,United States of America.

4 C onclusion

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