LED ACADEMY by OMS Lighting, Ltd.

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2.4. LensLens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging ordiverging the beam.Figure 2.4.1:Two basic types of lenses – convergingand diverging.LIGHTdffLIGHTdPositive (converging) lensOPTICAL AXISFOCAL POINTOPTICAL AXISFOCAL POINTR2R2R1R1POSITIVE (CONVERGING) LENSNEGATIVE (DIVERGING) LENSdNegative (diverging) lensffdLIGHTXISFOCAL POINTOPTICAL AXISFOCAL POINTR2R2R1R1POSITIVE (CONVERGING) LENSNEGATIVE (DIVERGING) LENSA simple lens consists of a single optical element. A compound lens is an array of simple lenses (elements) with a commonaxis. The use of multiple elements allows for more optical aberrations to be corrected than it is possible with asingle element. Lenses are typically made from glass or transparent plastic.Figure 2.4.2:Different types of lenses used with LEDlight sources.2.5. Materials for optical partsVarious optical parts need various optical materials. Aluminium with various types of finish and powder-coated metalsheets are used for reflectors. Clear polycarbonate (PC), polystyrene, and Polymethylmethacrylate (PMMA) are used formicro-prismatic diffusers and lenses.Materials for reflective optics – with its various characteristics are available in order to achieve different typesof reflection. There are three basic types of reflection: mirror, diffuse and mixed reflection. Difference between types ofreflection is in the proportion of mirror and diffuse part of reflection.Figure 2.5.1:Different types of reflection frommaterial.Ideal mirror reflection Real mirror reflection Ideal diffuse reflection Mixed reflectionLambertian reflectionLambertian with mirror reflection10 LED ACADEMY/LED OPTIC
Aluminium – it is the most common material for high quality reflectors thanks to its excellent reflectance. Anodizedaluminium, glazed aluminium, and aluminium sheets covered with several layers of silver are also used to reach higherreflectivity and resistance against scratches.Surface-treated sheet steel – white powder coating in various shades and structures is applied to sheet steelto achieve required reflection. If highly efficient Lambertian reflection is needed, a special material (WhiteOptics97) isapplied to sheet steel.Materials for refractive opticsPC – is easily mouldable and thermo-formable. It has index of refraction equal to 1.584.PMMA – is transparent for infrared light within the range from 2.8 to 25 micrometre, and opaque for radiation shorterthan 300 nm (UV radiation). Index of refraction = 1.49.LED ACADEMY11
Page 1 and 2: C=42.Reflective cupEmitted lightMol
Page 3 and 4: Figure 1.2.1:Various light sources
Page 5 and 6: Figure 1.2.4:The black-body curve (
Page 7 and 8: 60º60º60º60º30ºC0 / C1800ºcd
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Page 13 and 14: ConductionWhen a temperature gradie
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Page 17 and 18: Figure 3.6.1:a) Passive coolingb) A
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Page 21 and 22: Figure 4.2.1:Relative luminous flux
Page 23 and 24: Figure 4.3.3:LEDs in serial/paralle
Page 25 and 26: 4.5. LED driver additional features
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Page 29 and 30: Figure 5.4.1:Unlike traditional lig
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Page 33 and 34: Figure 6.2.1:LotusLotusAccent light
Page 35 and 36: Figure 6.4.1:Gacrux - microprism li
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Page 41 and 42: Figure 7.1.5:Solid state lighting m
Page 43: Figure 7.4.3:OMCVD FAB development

LED ACADEMY by OMS Lighting, Ltd.

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