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Optical Principles: LED Fundamentals

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When light encounters a surface, or travels from one media to another, several interactions are possible. For general lighting, we are typically interested in reflection, transmission, refraction, total internal reflection (which is really a special case of refraction), and absorption.

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Optical Principles: LED Fundamentals

  1. 1. LED FundamentalsOptical Principles08 04 201108-04-2011
  2. 2. Interaction of Light and Surfaces   Reflection Specular Semi-Specular Diffuse Transmission Direct Semi diffuse Diffuse Transparent Translucent Air Refraction Glass Water Convex (Convergent) Plano-Concave (Divergent) Total Internal Reflection R fl ti (TIR) AbsorptionLED Fundamentals | Optical Principles | Page 2
  3. 3. Reflection θi = θr θi θr θi Specular Semi-specular or semi-diffuse DiffuseLED Fundamentals | Optical Principles | Page 3
  4. 4. Refraction Light bends toward the normal g nisinθi = ntsinθt when going from low index to high index (low density to high density). Light bends away from the θi normal going from high index ni to low index. nt θtLED Fundamentals | Optical Principles | Page 4
  5. 5. Total Internal Reflection (TIR) and Critical Angle Critical Angle: sinθc = nt/ni 1 Acrylic: n = 1.493, θc = 42˚ 2 Polycarbonate: n = 1.586, θc = 39˚ 3 nt 4 ni 5 nt ni θi θrLED Fundamentals | Optical Principles | Page 5
  6. 6. Total Internal Reflection (TIR) and Critical Angle • Lightguides • TIR opticsLED Fundamentals | Optical Principles | Page 6
  7. 7. Fresnel Losses • When light strikes an interface between two different materials, some light is lost reflected (even at normal incidence) Reflected Air Plastic TransmittedLED Fundamentals | Optical Principles | Page 7
  8. 8. Fresnel Losses Fresnel Loss Through Flat Acrylic Plate 100.0% 90.0% 80.0% 70.0% 60.0% Transmitted 50.0% Reflected 40.0% 30.0% 20.0% 10.0% 0.0% 0 10 20 30 40 50 60 70 80 90 Incident Angle (deg)LED Fundamentals | Optical Principles | Page 8
  9. 9. 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. 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 f i i ti from one of OSRAM Opto Semiconductor GmbHs partners, or in view of f O t S i d t G bH t i i f products being a combination of an OSRAM Opto Semiconductor GmbHs product and a product of one of OSRAM Opto Semiconductor GmbHs partners. Furthermore, OSRAM Opto Semiconductors GmbH cannot be made liable for any damage that occurs in p y g 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.LED Fundamentals | Optical Principles | Page 9
  10. 10. Disclaimer This document constitutes neither an offer to sell nor a solicitation to buy or subscribe for securities. Any such offer will be made solely on the basis of the Securities Prospectus yet to be approved by the German Financial Supervisory Authority ( (BaFin) and p ) published thereafter. The information legally required to be p g y q provided to investors will be contained only in the Securities 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 f A th U it d St t of America. This d i Thi document i not an offer of securities f sale i th t is t ff f iti for l 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 Act. 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, g , , Japan or Australia.LED Fundamentals | Optical Principles | Page 10
  11. 11. Thank you for your attention.LED Fundamentals | Optical Principles | Page 11

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