Sources of Light OPTI 200 Dr. Mike Nofziger Professor College of Optical Sciences University of Arizona Dr. Mike Nofziger 2010

Sources of Light Fire– rapid oxidation of a combustible material – heat and light are emitted in the process Flame– visible light-emitting part of a fire – complete combustion blue color – incomplete combustion yellow color Bunsen burner (1)yellow flame, air closed 900 °C … (5) blue flame, air open 1600 °C Bunsen burner flames

Dr. Mike Nofziger 2010 Sources of Light Flames from a charcoal fire °C Candle flame 1100 °C Incandescence is the emission of visible light from a hot body due to its temperature. – means to glow white – heat and light are emitted in the process – incomplete combustion yellow color

Dr. Mike Nofziger 2010 Sources of Light Incandescence produces a blackbody spectrum of energy: – described by the Planck function – light output is only a function of temperature, T – the higher T, the more light out – the higher T, the peak shifts to the blue – our SUN (T=6000K) and stars are perfect blackbody radiators

Dr. Mike Nofziger 2010 Sources of Light Tungsten (Incandescent) Light Bulbs – tungsten filament – resistive to the flow of electrical current – electrical energy converted to thermal energy – filament heats up, incandesces (emits light) 1.Outline of Glass bulb 2.Low pressure inert gas (argon, neon, nitrogen) 3.Tungsten filament 4.Contact wire (goes out of stem) 5.Contact wire (goes into stem) 6.Support wires 7.Stem (glass mount) 8.Contact wire (goes out of stem) 9.Cap (sleeve) 10.Insulation (vitrite)vitrite 11.Electrical contact Reference

Dr. Mike Nofziger 2010 Sources of Light Tungsten (Incandescent) Light Bulbs Incandescent Light Bulb °C A19 style, Edison base

Dr. Mike Nofziger 2010 Sources of Light Automotive Incandescent Light Bulbs H3 H4P27R5WP21 Sealed Beam Non-Sealed Beam Dome Light

Dr. Mike Nofziger 2010 Tungsten-halogen Bulb °C filament °C bulb wall Sources of Light Tungsten-halogen Light Bulbs – tungsten filament – trace amount of halogen vapor, iodine or bromine – bulb made of fused quartz, >1atm pressure – tungsten deposited back onto the filament (halogen cycle)halogen cycle – longer lifetime of the filament

Dr. Mike Nofziger 2010 Sources of Light Tungsten bulbs: Light output – watts or lumens? – we see lumens, not watts – maximum of 683 lm/W at 555 nm New labeling by 2011 Brightness

Dr. Mike Nofziger 2010 Sources of Light Tungsten bulbs: Light output – a 100W light tungsten bulb converts only 10W into visible light – 90 watts are wasted as heat – 50-70% of the worlds total sales of lighting are incandescent bulbs Reference Reference – need more efficient sources of light – the sale of tungsten light bulbs will (?) be banned in the US by the year 2014 or ? CFL LED

Dr. Mike Nofziger 2010 Fluorescent Lampold style - tube is typically straight, ft. long - tube filled with low-pressure Hg vapor - pressure 0.3% atmospheric - inner surface coated with phosphor coatings - use large, heavy magnetic ballasts Sources of Light Output spectrum of a typical cool-white lamp

Dr. Mike Nofziger 2010 Sources of Light Compact Fluorescent Lamp CFLnew style - tube is a shaped in a spiral - inner surface coated with a phosphor coating - use lightweight, electronic ballast - standard Edison screw base (replaces light bulbs) - long-term cost savings compared to tungsten light bulbs - very little heat produced compared to tungsten light bulbs - lifetime depends on how you use it…. ?

Dr. Mike Nofziger 2010 LED – Light Emitting Diode – solid-state, semiconductor p-n junction – GaAs, AlGaAs, GaP, AlGaInP, GaN, InGaN,etc. – 3mm, 5mm, or 8mm dia. plastic packages Sources of Light Low-Power LEDs 1-20mA of electrical current on/off indicators High-power LEDs 500mA to >1A Lumileds, Osram, Cree Lighting!! Replace incandescent bulbs

Dr. Mike Nofziger 2010 Sources of Light LED – Light Emitting Diode

Dr. Mike Nofziger 2010 Sources of Light White-Light LEDs: General Approaches Reference

Dr. Mike Nofziger 2010 Sources of Light White-Light LEDs (3 phosphors, tri-phosphor) – AlGaInN LED is the source of light – emits light in the near-UV spectral region – nm – 3 phosphor coatings on top – Europium-based red and blue phosphors – Copper and aluminum doped zinc sulfide green phosphor – Color-mixing more easily controlled to produce a pure white light. – Example: CREECREE Reference

Dr. Mike Nofziger 2010 Sources of Light White-Light LEDs (1 phosphor) – GaN semiconductor LED is the source of light – emits blue light 450 – 470 nm – Yellow phosphor coating on top – Cerium-doped YAG: Y 3 Al 5 O 12 :Ce 3+ – light is emitted by scintillation (no afterglow) Example: CREECREE

Dr. Mike Nofziger 2010 Sources of Light White-Light LEDs: TRENDS Reference

Dr. Mike Nofziger 2010 Sources of Light White-Light LEDs: Applications vs.

Dr. Mike Nofziger 2010 Sources of Light White-Light LEDs: Applications Uses a CREE XM-L 1000 lumen LED

Dr. Mike Nofziger 2010 Sources of Light Arc Lights - 2 electrodes separated by a small gap containing a gas - flow of electricity between the electrodes ionizes the gas - light produced from the ionized gas Carbon-rod electrodes, air gap, no glass housing: Carbon Arc Lamp (no longer used, historical) arch arc Tungsten electrodes, quartz envelope, gas: neon, argon, xenon, krypton, mercury, metal halide High Intensity Discharge (HID) Lamps

Dr. Mike Nofziger 2010 Sources of Light Type of HID Lamps 15 kW xenon arc lamp used in the IMAX projection system Mercury arc lamp used in a fluorescence microscope Commercial lighting Automotive headlights

Dr. Mike Nofziger 2010 Sources of Light Comparison of light output: Luminous Efficacy Type of LampLumens / WattLifetime (hours) 100W Tungsten W Tungsten Halogen Fluorescent ,000 Compact Fluorescent Low-Pressure Sodium ,000 High-Pressure Sodium ,000-24,000 Metal Halide (HID) ,000 LED , ,000 High-Power LEDs> 105 (year 2009)> 20,000 (current 350mA (2/2010)> 20,000

Dr. Mike Nofziger 2010 Sources of Light Comparison of light output:

Dr. Mike Nofziger 2010 Sources of Light Automotive LED Headlamp Design

Dr. Mike Nofziger 2010 Automotive LED Headlamps !!!!! Sources of Light Ichikoh Industries (AFS) system Toyota Prius Lexus LS 600h

Dr. Mike Nofziger 2010 Questions (1) What color is a flame with complete combustion? (2) What is incandescence? (3) How does a tungsten light bulb produce light? (4) What does the halogen cycle do in a light bulb? (5) Does the human eye respond to lumens or watts? (6) What kind of device is an LED? (7) How does a fluorescent lamp produce light? (8) How efficient is a tungsten light bulb in turning electrical energy into light?

Dr. Mike Nofziger 2010 The End