Light. Topics. Page 1. Visible electromagnetic radiation Power spectrum. Polarization Photon (quantum effects) Wave (interference, diffraction)

Transcription

1 Light Visible electmagnetic adiatin Pwe spectum Pwe Heat Radi Ulta- X-Rays Gamma Csmic Infa- Red Vilet Rays Rays Wavelength (NM) IR R G B UV Plaizatin Phtn (quantum effects) Wave (intefeence, diffactin) Fm Lndn and Uptn Tpics Radimety and phtmety Measuing spatial ppeties f light Radiant pwe Radiant intensity Iadiance Invese squae law and csine law Radiance Radiant exitance (adisity) Page 1

2 Radimety and Phtmety Radiant Enegy and Pwe Pwe: Watts (adimety) Φ vs. Lumens (phtmety) Enegy efficiency Spectal efficacy Enegy: Jules vs. Talbt Expsue Film espnse Luminance Skin - sunbun Y V( λ) L( λ) dλ Page

3 Radiant Intensity Radiant Intensity Definitin: The adiant (luminus) intensity is the pwe pe unit slid angle emanating fm a pint suce. I( ω) dφ W lm cd candela s s Page 3

4 Angles and Slid Angles Angle l cicle has π adians A Slid angle Ω R sphee has 4π steadians Diffeential Slid Angles sin dφ φ d ( d )( sin dφ ) sin d dφ sin d dφ Page 4

5 Diffeential Slid Angles sin dφ φ d sinddφ Ω S π π π 1 0 4π sin d dφ dcs dφ Sphee S Istpic Pint Suce Φ S 4π I I I Φ 4π Page 5

6 Wan s Sptlight ω ÂA s I ( ω) cs ( ω Aˆ ) s π 1 Φ I ( ω ) dcs dϕ 0 0 Wan s Sptlight ω ÂA s I ( ω) cs ( ω Aˆ ) s π 1 1 s π Φ I ( ω ) dcs dϕ π cs dcs s Page 6

7 Wan s Sptlight ω ÂA s I ( ω) cs ( ω Aˆ ) s π 1 1 s π Φ I ( ω ) dcs dϕ π cs dcs s s + 1 s I( ω) Φ cs π Light Suce Gnimetic Diagams Page 7

8 PIXAR Pint Light Suce Shadws Shadw Matte Pjected Slide Textue UbeLight( ) { Clip t nea/fa planes Clip t shape bunday feach supeelliptical blcke atten * feach ckie textue atten * feach slide textue cl * feach nise textue atten, cl * feach shadw map atten, cl * Calculate intensity fall-ff Calculate beam distibutin } Iadiance Page 8

9 Iadiance Definitin: The iadiance (illuminance) is the pwe pe unit aea incident n a suface. dφi Ex () W lm lux m m Smetimes efeed t as the adiant (luminus) incidence. Lambet s Csine Law ΦEA A E A Φ Page 9

10 Lambet s Csine Law A A /cs Φ Φ Φ E cs A /cs A Iadiance: Istpic Pint Suce h I Φ 4π Page 10

11 Iadiance: Istpic Pint Suce h I Φ 4π dφ I Iadiance: Istpic Pint Suce h I Φ 4π cs Page 11

12 Iadiance: Istpic Pint Suce h I Φ 4π I Φ cs 4π Iadiance: Istpic Pint Suce h I Φ 4π Φ cs I E 4π Φ cs E 4π Page 1

13 Iadiance: Istpic Pint Suce Φ I 4π h cs E Φ cs Φ cs 4π 4π h 3 The Inventin f Phtmety Bugue s classic expeiment Cmpae a light suce and a candle Mve until they bth appea equally bight Intensity is pptinal t ati f distances squaed Definitin f a candela Oiginally a standad candle Cuently 550 nm lase w/ 1/683 W/s 1 f 6 fundamental SI units Page 13

14 Typical Values f Illuminance [lm/m ] Sunlight plus skylight 100,000 lux Sunlight plus skylight (vecast) 10,000 Intei nea windw (daylight) 1,000 Atificial light (minimum) 100 Mnlight (full) 0.0 Stalight Radiance Page 14

15 Aea Lights Suface Radiance Definitin: The suface adiance (luminance) is the intensity pe unit aea leaving a suface Lxω (, ) di( x, ω) Lx (, ω) d Φ( x, ω) W cd lm nit s m m s m Pwe Leaving a Suface Lxω (, ) d Φ ( x, ω) L( x, ω) Page 15

16 Typical Values f Luminance [cd/m ] Suface f the sun,000,000,000 nit Sunlight cluds 30,000 Clea day 3,000 Ovecast day 300 Mn 0.03 Radiant Exitance (Radisity) Page 16

17 Radiant Exitance Definitin: The adiant (luminus) exitance is the enegy pe unit aea leaving a suface. dφ Mx ( ) W lm lux m m In cmpute gaphics, this quantity is ften efeed t as the adisity (B) Pwe Leaving a Suface Lxω (, ) d Φ ( x, ω) L( x, ω) Page 17

18 Diectinal Pwe Leaving a Suface L (, x ω ) d Φ ( x, ω) L ( x, ω)cs d Φ (, x ω ) Nte csine Aea Light Suce d Φ ( x, ω) L ( x, ω)cs L (, x ω ) Same f all diectins Page 18

19 Aea Light Suce d Φ( x, ω) dm ( x, ω) L ( x, ω)cs L (, x ω ) Same f all diectins Aea Light Suce dm ( x, ω) L ( x, ω)cs L (, x ω ) Same f all diectins Page 19

20 Aea Light Suce M dm ( x, ω) L ( x, ω)cs H H L (, x ω ) H Hemisphee Unifm Diffuse Emitte M L cs H L H cs L ( x, ω ) L Page 0

21 Pjected Slid Angle Ω cs Ω cs Pjected Slid Angle Ω cs Ω cs Ω cs π CS348B Lectue 4 H Pat Hanahan, 008 Page 1

22 Unifm Diffuse Emitte M L cs H L πl cs H M L L M π Radimety and Phtmety Summay Page

23 Radimetic and Phtmetic Tems Physics Radimety Phtmety Enegy Radiant Enegy Luminus Enegy Flux (Pwe) Radiant Pwe Luminus Pwe Flux Density Iadiance Radisity Illuminance Luminsity Angula Flux Density Radiance Luminance Intensity Radiant Intensity Luminus Intensity Phtmetic Units Phtmety Units Luminus Enegy Talbt MKS CGS Bitish Luminus Pwe Illuminance Luminsity Lumen Lux Pht Ftcandle Luminance Nit Stilb Apstilb, Blndel Lambet Ftlambet Luminus Intensity Candela (Candle, Candlepwe, Cacel, Hefne) Thus ne nit is ne lux pe steadian is ne candela pe squae mete is ne lumen pe squae mete pe steadian. Gt it?, James Kajiya Page 3