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Introduction to Measurement Quantities 1Optronic Laboratories Dr. Richard Young Optronic Laboratories, Inc.

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Introduction to Measurement Quantities 2Optronic Laboratories Several types of light measurement are possible. These define WHAT you measure. For each type of measurement, there are several possible techniques. These define HOW you measure.

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Introduction to Measurement Quantities 3Optronic Laboratories Techniques=how Photometry & colorimetry Radiometry Spectroradiometry Types=what Total Flux Angular Intensity At a surface At the source

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Introduction to Measurement Quantities 4Optronic Laboratories Techniques Photometry & colorimetry Types Total Flux Angular Intensity At a surface At the source How does it look to humans? Quantities start with photopic or luminous

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Introduction to Measurement Quantities 5Optronic Laboratories Techniques Radiometry Types Total Flux Angular Intensity At a surface At the source How much energy is produced? Quantities start with radiometric or radiant

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Introduction to Measurement Quantities 6Optronic Laboratories Techniques Spectroradiometry Types Total Flux Angular Intensity At a surface At the source How is the energy distributed? Quantities start with spectral or spectroradiometric

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Introduction to Measurement Quantities 7Optronic Laboratories Techniques Photometry & colorimetry Radiometry Spectroradiometry Types Total Flux Light emitted in ALL directions Quantities end with flux

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Introduction to Measurement Quantities 8Optronic Laboratories Techniques Photometry & colorimetry Radiometry Spectroradiometry Types Angular Intensity Light emitted in SPECIFIED directions and angles Quantities end with intensity

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Introduction to Measurement Quantities 9Optronic Laboratories Techniques Photometry & colorimetry Radiometry Spectroradiometry Types At a surface Light falling onto areas of an object Quantities end with irradiance or illuminance

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Introduction to Measurement Quantities 10Optronic Laboratories Techniques Photometry & colorimetry Radiometry Spectroradiometry Types At the source Light emitted from areas within the source Quantities end with radiance or luminance

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Introduction to Measurement Quantities 11Optronic Laboratories Photometry + Total Flux = Total luminous flux unit: lumen Radiometry + Total Flux = Total radiant flux unit: Watt Spectroradiometry + Total Flux = Total spectral flux unit: Watt/nm

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Introduction to Measurement Quantities 12Optronic Laboratories Photometry + Angular Intensity = Luminous intensity unit: candela = lumen/sr Radiometry + Angular Intensity = Radiant intensity unit: Watt/sr Spectroradiometry + Angular Intensity = Spectroradiometric intensity unit: Watt/(sr nm)

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Introduction to Measurement Quantities 13Optronic Laboratories Photometry + At a surface = Illuminance unit: lux = lumen/m² Radiometry + At a surface = Irradiance unit: Watt/m² Spectroradiometry + At a surface = Spectral irradiance unit: Watt/(m² nm)

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Introduction to Measurement Quantities 14Optronic Laboratories Photometry + At a source = Luminance unit: candela/m² = lumen/(sr m²) Radiometry + At a source = Radiance unit: Watt/(sr m²) Spectroradiometry + At a source = Spectral radiance unit: Watt/(sr m² nm)

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Introduction to Measurement Quantities 15Optronic Laboratories The preceding units are SI units, currently the favored units by all National Standard Laboratories (NIST etc.) Sometimes older standards or conventions may require values to be reported in different units Quantities that are of the same technique and type can be converted by multiplying with a constant.

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Introduction to Measurement Quantities 16Optronic Laboratories Sometimes the conversion is because the quantities use different standard units –E.g. using inches instead of meters for measuring length Sometimes the conversion is because the quantities use sub-units –E.g. millimeters instead of meters

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Introduction to Measurement Quantities 17Optronic Laboratories Common sub-unit prefixes –femto (f), multiplied by 1E-15 –pico (p), multiplied by 1E-12 –nano (n), multiplied by 1E-9 –micro (µ), multiplied by 1E-6 –milli (m), multiplied by 1E-3 –centi (c), multiplied by 1E-2 –deci (d), multiplied by 1E-1 –kilo (k), multiplied by 1E3 –mega (M), multiplied by 1E6 –giga (G), multiplied by 1E9 –tera (T), multiplied by 1E12

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Introduction to Measurement Quantities 18Optronic Laboratories cd/m² lux (lm/m²) cd/in² footlambert ((cd/ft²)/ ) Lambert ((cd/cm²)/ ) stilb (cd/cm²) Footcandle (lm/ft²) phot (lm/cm²) E E E E E E-4 Convert fromtomultiply by Conversion to older units

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