GeomOpt_Part51

GeomOpt_Part51 - Department of Electrical and Computer...

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Department of Electrical and Computer Engineering ECSE 527 Optical Engineering adiometry Radiometry References: Smith, Modern Optical Engineering , Chapter 8 .O’Shea lements of Modern Optical Design Chapter 3 D.O Shea, Elements of Modern Optical Design , Chapter 3 Andrew Kirk 2010 Radiometry 1
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Radiometry ©AGK 2010 Radiometry 2
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Radiometry ptical systems perform two operations: Optical systems perform two operations: –t ran s fe r of object structure (imaging) ansfer of object power (radiometry) transfer of object power (radiometry) • Power transfer determines visibility, detector performance etc. •S o m e t i m e we only need power transfer –e .g . searchlight, projector lamps •H o w do we calculate power emitted from object and ansferred through an optical system ? ©AGK 2010 Radiometry 3 transferred through an optical system ?
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Example: Surface inspection problem Diffuse (70% reflecting) rface Lens (80% transmission) Aperture: 4 cm 2 surface 200 cm Area: 1 cm 2 Detector 100 cm 60° 100 cm Lambertian source 15 cm diameter 115 cm diameter 10 W ster 1 cm 2 ©AGK 2010 Radiometry 4 Question: How much total power is received at the detector ?
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Learning outcomes After taking this section you will be able to: •D e f i n e radiant intensity and irradiance • Calculate the radiant intensity and irradiance of a point urce source • Explain what is meant by a Lambertian source • Determine when to treat emitters and surfaces as Lambertian surfaces • Calculate the emission of a Lambertian surface • Calculate power transfer through an optical system ©AGK 2010 Radiometry 5
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Contents Definition of radiometric units •P o i n t sources Lambertian emitters tf th h ti l t Power transfer through an optical system •C o n s t a n t brightness theorem ©AGK 2010 Radiometry 6
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Power and radiant intensity • Power P :R a t e of radiation of energy [W] Power from a point source fills a sphere of adiant tensity ower radiated into a solid 4 π steradians Radiant intensity J :Power radiated into a solid angle [W ster 1 ] J = P /4 π W ster -1 ©AGK 2010 Radiometry 7
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Irradiance • Irradiance Unit area Distance S Point source Intensity J W ster 1 Power P W Solid angle 1/ S 2 ster ©AGK 2010 Radiometry 8
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Irradiance • Irradiance H : Power/unit area falling on a surface [W cm 2 ] Unit area Distance S Point source Intensity J Power P Solid angle 1/ S 2 ster radiance ©AGK 2010 Radiometry 9 Irradiance
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Example •1 0 W source • Intensity: •R a d i a t i o n on surface 100 cm from source: ©AGK 2010 Radiometry 10
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Example •1 0 W source • Intensity J=10/4 π = 0.8 W/ster •R a d i a t i o n on surface 100 cm from source: J/S H = J/S 2 = 0.8/100 2 08 x 10 4 cm 2 = 0.8 x 10 W cm ©AGK 2010 Radiometry 11
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Irradiance off axis x cos S Point source Intensity J ower S / cos x / cos Power P x istance increased by / s Distance increased by 1/cos Effective area increased by 1/cos n xis irradiance: On axis irradiance: ©AGK 2010 Radiometry 12
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Irradiance off axis x S Point source
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This note was uploaded on 09/28/2010 for the course ECSE ECSE 527 taught by Professor Kirk during the Winter '10 term at McGill.

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GeomOpt_Part51 - Department of Electrical and Computer...

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