sources of light opti 200 dr. mike nofziger professor college of optical sciences university of...
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“Sources of Light”OPTI 200
Dr. Mike Nofziger
Professor
College of Optical Sciences
University of Arizona
Dr. Mike Nofziger 2010
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 closed900 °C
…(5) blue flame, air open
1600 °CBunsen burner flames
Dr. Mike Nofziger 2010
“Sources of Light”
Flames from a charcoal fire750-1200 °C
Candle flame1100 °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 bulb2.Low pressure inert gas (argon, neon, nitrogen)3.Tungsten filament4.Contact wire (goes out of stem)5.Contact wire (goes into stem)6.Support wires7.Stem (glass mount)8.Contact wire (goes out of stem)9.Cap (sleeve)10.Insulation (vitrite)11.Electrical contact
Reference
Dr. Mike Nofziger 2010
“Sources of Light”
Tungsten (“Incandescent”) Light Bulbs
Incandescent Light Bulb1700-3000 °C
“A19” style, Edison base
Dr. Mike Nofziger 2010
“Sources of Light”
Automotive Incandescent Light Bulbs
H3 H4 P27R5WP21
Sealed Beam
Non-Sealed Beam
Dome Light
Dr. Mike Nofziger 2010
Tungsten-halogen Bulb2500-3100 °C filament400-1000 °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)– 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 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 ?
CFLLED
Dr. Mike Nofziger 2010
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
“Sources of Light”
Output spectrum of a typical “cool-white” lamp
Dr. Mike Nofziger 2010
“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
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 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
“Sources of Light”
LED – Light Emitting Diode
Dr. Mike Nofziger 2010
“Sources of Light”
White-Light LED’s: General Approaches
Reference
Dr. Mike Nofziger 2010
“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
“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
“Sources of Light”
White-Light LED’s: TRENDS
Reference
Reference
Dr. Mike Nofziger 2010
“Sources of Light”
White-Light LED’s: Applications
vs.
Dr. Mike Nofziger 2010
“Sources of Light”
White-Light LED’s: 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 usedin the IMAX projection system
Mercury arc lamp usedin a fluorescence microscope
Commercial lighting
Automotive headlights
Dr. Mike Nofziger 2010
“Sources of Light”Comparison of light output: “Luminous Efficacy”
Type of Lamp Lumens / Watt Lifetime (hours)
100W Tungsten 17.5 750-1000
100W Tungsten Halogen ≈16-24 ≈1500-3000
Fluorescent 33-100 ≈7500-20,000
Compact Fluorescent ≈46-75 ≈6000-15000
Low-Pressure Sodium ≈100-200 ≈16,000
High-Pressure Sodium ≈85-150 18,000-24,000
Metal Halide (HID) ≈65-115 6000-10,000
LED ≈55-82 ≈25,000-100,000
High-Power LED’s > 105 (year 2009) > 20,000
(current record…) 208 @ 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”