L5 - The University of Arizona College of Optical Sciences

Report
“Sources of Light”
OPTI 200
Dr. Mike Nofziger
Professor
College of Optical Sciences
University of Arizona
Dr. Mike Nofziger 2010
“Sources of Light”
– “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
Fire
Bunsen burner flames
(1) yellow flame, air closed
900 °C
…
(5) blue flame, air open
1600 °C
Bunsen burner
Dr. Mike Nofziger 2010
“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
“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)
11.Electrical contact
Reference
Dr. Mike Nofziger 2010
“Sources of Light”
Tungsten (“Incandescent”) Light Bulbs
Incandescent Light Bulb
1700-3000 °C
“A19” style, Edison base
Dr. Mike Nofziger 2010
“Sources of Light”
Automotive Incandescent Light Bulbs
H3
H4
P21
Dome Light
R5W
P27
Sealed Beam
Non-Sealed Beam
Dr. Mike Nofziger 2010
“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
“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
– need more efficient sources of light
– the sale of tungsten light bulbs will (?) be banned
in the US by the year 2014
Reference

?
or
LED
CFL
Dr. Mike Nofziger 2010
“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
“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
“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
“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
Reference
– Color-mixing more easily controlled to produce
a pure white light.
– Example: CREE
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 used
in the IMAX projection system
Mercury arc lamp used
in a fluorescence microscope
Automotive headlights
Commercial lighting
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
“Sources of Light”
Automotive LED Headlamps !!!!!
Toyota Prius
Ichikoh Industries (AFS) system
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”
Dr. Mike Nofziger 2010

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