Presentation Transcript

1. “Sources of Light”OPTI 200

   Dr. Mike Nofziger Professor College of Optical Sciences University of Arizona Dr. Mike Nofziger 2010
2. “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 yellow flame, air closed 900 °C … (5) blue flame, air open 1600 °C Bunsen burner Bunsen burner flames Dr. Mike Nofziger 2010
3. “Sources of Light” Flames from a charcoal fire 750-1200 °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
4. “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
5. “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) Dr. Mike Nofziger 2010
6. “Sources of Light” Tungsten (“Incandescent”) Light Bulbs Incandescent Light Bulb 1700-3000 °C “A19” style, Edison base Dr. Mike Nofziger 2010
7. “Sources of Light” Automotive Incandescent Light Bulbs Dome Light H3 H4 P21 R5W P27 Sealed Beam Non-Sealed Beam Dr. Mike Nofziger 2010
8. “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) – longer lifetime of the filament Tungsten-halogen Bulb 2500-3100 °C filament 400-1000 °C bulb wall Dr. Mike Nofziger 2010
9. “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
10. “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 world’s total sales of lighting are incandescent bulbs Reference – need more efficient sources of light – the sale of tungsten light bulbs will (?) be banned in the US by the year 2014 ?  or LED Dr. Mike Nofziger 2010 CFL
11. “Sources of Light” Fluorescent Lamp—old style - tube is typically straight, 1.5-8 ft. long tube filled with low-pressure Hg vapor pressure ≈ 0.3% atmospheric inner surface coated with phosphor coatings use large, heavy magnetic ballasts Output spectrum of a typical “cool-white” lamp Dr. Mike Nofziger 2010
12. “Sources of Light” Compact Fluorescent Lamp “CFL”—new 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
13. “Sources of Light” LED – Light Emitting Diode – solid-state, semiconductor p-n junction – GaAs, AlGaAs, GaP, AlGaInP, GaN, InGaN,etc. – 3mm, 5mm, or 8mm dia. plastic packages Low-Power LED’s 1-20mA of electrical current “on/off indicators” High-power LED’s  500mA to >1A Lumileds, Osram, Cree Lighting!! Replace incandescent bulbs Dr. Mike Nofziger 2010
14. “Sources of Light” LED – Light Emitting Diode Dr. Mike Nofziger 2010
15. “Sources of Light” White-Light LED’s: General Approaches Reference Dr. Mike Nofziger 2010
16. “Sources of Light” White-Light LED’s (3 phosphors, “tri-phosphor”) – AlGaInN LED is the source of light – emits light in the near-UV spectral region – 380-430 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: CREE Reference Dr. Mike Nofziger 2010
17. “Sources of Light” White-Light LED’s (1 phosphor) – GaN semiconductor LED is the source of light – emits blue light 450 – 470 nm – Yellow phosphor coating on top – Cerium-doped YAG: Y3Al5O12:Ce3+ – light is emitted by scintillation (no afterglow) Example: CREE Dr. Mike Nofziger 2010
18. “Sources of Light” White-Light LED’s: TRENDS Reference Reference Dr. Mike Nofziger 2010
19. “Sources of Light” White-Light LED’s: Applications vs. Dr. Mike Nofziger 2010
20. “Sources of Light” White-Light LED’s: Applications Uses a CREE XM-L 1000 lumen LED Dr. Mike Nofziger 2010
21. “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
22. “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 Automotive headlights Commercial lighting Dr. Mike Nofziger 2010
23. “Sources of Light” Comparison of light output: “Luminous Efficacy” Dr. Mike Nofziger 2010
24. “Sources of Light” Comparison of light output: Dr. Mike Nofziger 2010
25. “Sources of Light” Automotive LED Headlamp Design Dr. Mike Nofziger 2010
26. “Sources of Light” Automotive LED Headlamps !!!!! Toyota Prius Ichikoh Industries (AFS) system Lexus LS 600h Dr. Mike Nofziger 2010
27. “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
28. “The End” Dr. Mike Nofziger 2010