Radiometry and Photometry: LED Fundamentals

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In this presentation on Radiometry and Photometry we will look at Radiometry, the detection and measurement of radiation across the full electromagnetic spectrum, including ultraviolet, visible and infrared radiation. Photometry is concerned only with the visible portion of the spectrum, from about 380 to 780 nanometers.

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Radiometry and Photometry: LED Fundamentals

  1. 1. LED FundamentalsRadiometry &Photometry08-03-2011
  2. 2. Definitions, Units and Symbols  Radiometry – deals with the detection and measurement of electromagnetic radiation across the total spectrum  Photometry – subfield of radiometry; radiometric power scaled by the spectral response of the human eyeLED Fundamentals | Radiometry & Photometry | Page 2
  3. 3. Definitions, Units and Symbols  Radiometry – deals with the detection and measurement of electromagnetic radiation across the total spectrum  Photometry – subfield of radiometry; radiometric power scaled by the spectral response of the human eye Radiometric Photometric Quantity Symbol Units Quantity Symbol Units Radiant Power Φe W Luminous Flux Φv lumens (lm)Radiant Intensity Ie W/sr Luminous Intensity Iv lm/sr 2 2 Irradiance Ee W/m Illuminance Ev lm/m 2 2 Radiance Le W/m -sr Luminance Lv lm/m -sr “e” = “energetic” “v” = “visual” v visualLED Fundamentals | Radiometry & Photometry | Page 3
  4. 4. Converting to Photometric Units  Power (Watts) is converted to luminous flux (lumens) via the relation: Φv = flux (lumens) 780  v  K  Pe   V   d Pe = Power V = photopic response function 380 of the human eye 1 0.9 K = constant (683 lm/W for 0.8 photopic) 0.7 Relative Sensitivity 0.6 0.5 0.4 R 0.3 0.2 0.1 0 400 450 500 550 600 650 700 750 Wavelength (nm)LED Fundamentals | Radiometry & Photometry | Page 4
  5. 5. Convert Radiometric to Photometric Pe   V   Pv   1 1 1 0.8 0.8 0.8 0.6 ensity [a.u.] 0.6 0.6 0.4 0.4 04 0.4 inte 0.2 0.2 0.2 0 0 400 450 500 550 600 650 700 750 0 400 450 500 550 600 650 700 750 400 450 500 550 600 650 700 750 W avel eng t h ( nm) W aveleng t h ( nm) Wavelegth [nm] 780  v  K  Pe   V   d 380LED Fundamentals | Radiometry & Photometry | Page 5
  6. 6. Solid Angle Surface Area = A Sphere radius = R Solid Angle Ω = A/R2 Units: Steradians (sr)LED Fundamentals | Radiometry & Photometry | Page 6
  7. 7. Projected Solid Angle Solid angle area (d)  Solid Angle Area d  Area of projected solid angle (cos  d) Unit sphereLED Fundamentals | Radiometry & Photometry | Page 7
  8. 8. Projected Solid Angle d  sin  d d d proj  cos  d 2  α  proj    cos sin  d d 0 0  projj   sin  2LED Fundamentals | Radiometry & Photometry | Page 8
  9. 9. Photometric Units and Symbols Photometric Units Metric English Quantity Symbol Units Name Units Name Luminous Flux Φ lumens (lm) lumens candela (cd) Luminous I lm/sr or Intensity candlepower 2 2 Illuminance E lm/m lux (lx) lm/ft Ft-candle 2 2 Luminance L cd/m nits cd/π*ft Ft-Lambert I E LLED Fundamentals | Radiometry & Photometry | Page 9
  10. 10. Lambertian Source  Brightness (luminance) is independent of angle L   L0   Intensity falls off as cosθ I ( )  I 0 cos  Many LEDs are very nearly Lambertian sources I0 I 0 cos  LED Fundamentals | Radiometry & Photometry | Page 10
  11. 11. Lambertian Source Total flux in a 2θ cone:    2  I  sin  d 0    2  I 0 cos  sin  d 0   I 0 sin 2  The total flux of a Lambertian source of 1 cd is lumens.LED Fundamentals | Radiometry & Photometry | Page 11
  12. 12. Disclaimer All information contained in this document has been checked with the greatest care. OSRAM Opto Semiconductors GmbH can however, not be made liable for any damage that occurs in connection with the use of these contents contents. OSRAM Opto Semiconductor GmbH makes no representations and warranties as to a possible interference with third parties intellectual property rights in view of products originating from one of OSRAM Opto Semiconductor GmbHs partners, or in view of products being a combination of an OSRAM Opto Semiconductor GmbHs product and a product of one of OSRAM Opto Semiconductor GmbHs partners. Furthermore OSRAM GmbH s partners Furthermore, Opto Semiconductors GmbH cannot be made liable for any damage that occurs in connection with the use of a product of one of OSRAM Opto Semiconductor GmbHs partners, or with the use of a combination of an OSRAM Opto Semiconductor GmbHs product and a product of one of OSRAM Opto Semiconductor GmbHs partners. f f OS O S GLED Fundamentals | Radiometry & Photometry | Page 12
  13. 13. This document constitutes neither an offer to sell nor a solicitation to buy or subscribe for f securities. Any such offer will b made solely on th b i of th S iti A h ff ill be d l l the basis f the Securities iti Prospectus yet to be approved by the German Financial Supervisory Authority (BaFin) and published thereafter. The information legally required to be provided to investors will be contained only in the Securities Prospectus Prospectus. The information contained herein is not for distribution, directly or indirectly, in or Into the United States of America (including its territories and possessions of any State of the United States of America or the District of Columbia) and must not be distributed to U.S. persons (as defined in Regulation S under the U.S. Securities Act of 1933, as amended ("Securities Act")) or publications with a general circulation in the United States of America. This document is not an offer of securities for sale in the United States of America. The securities have not been and will not be registered under the Securities Act and may not be offered or sold in the United States of America absent registration or an exemption from registration under the Securities Act. The Issuer does not intend to register any portion of the offering in the United States of America or to conduct a public offering of the securities in the United States of America. This document is not an offer of securities for sale in the United Kingdom, Canada, Japan or A stralia Australia.LED Fundamentals | Radiometry & Photometry | Page 13
  14. 14. Thank you for your attention.

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