May Chuck DiMarzio, Northeastern University ECE-1466 Modern Optics Course Notes Part 6 Prof. Charles A. DiMarzio Northeastern University Spring 2002
May Chuck DiMarzio, Northeastern University Lecture Overview Some Radiometry –Terminology –Equations Relating Radiometric Parameters –Photometric Parameters Some Numbers A Little Bit of Scattering Theory Some Applications in Microscopy
May Chuck DiMarzio, Northeastern University Radiometric Quantities
May Chuck DiMarzio, Northeastern University Radiometry and Photometry , Flux M, Flux/Proj. Area I, Flux/ L,Flux/A E, Flux/Area Rcd. Radiant Flux Watts Luminous Flux Lumens Radiant Exitance Watts/m 2 Luminous Exitance Lumens/m 2 =Lux Radiance Watts/m 2 /sr Luminance Lumens/m 2 /sr 1 Lambert= (1L/cm 2 /sr)/ 1 ftLambert= (1L/ft 2 /sr)/ 1mLambert= (1L/m 2 /sr)/ Radiant Intensity Watts/sr Luminous Intensity Lumens/sr 1 Candela=1cd=1L/sr Irradiance Watts/m 2 Illuminance Lumens/m 2 =Lux 1 Ft Candle=1L/ft 2 Notes: Spectral x=dx/d or dx/d : Add subscript or , divide units by Hz or m. 1 W is 683 L at 555 nm.
May Chuck DiMarzio, Northeastern University Luminance and Radiance Wavelength, nm Photopic Sensitivity y This curve shows the relative sensitivity of the eye. To convert to photometric units from radiometric, multiply by 683 Lumens Per Watt
May Chuck DiMarzio, Northeastern University Radiance in Images dA’ d1d1 d2d2 dA 1 dA 2 z
May Chuck DiMarzio, Northeastern University Typical Radiance Levels Our Example = / W/m 2 /sr ~ W/m 2 /sr at f/1 Half-Lux Camera = W/m 2 /sr
May Chuck DiMarzio, Northeastern University Black-Body Equation (1)
May Chuck DiMarzio, Northeastern University Black Body Equations (2) T=300k
May Chuck DiMarzio, Northeastern University Solar Irradiance on Earth Data from The Science of Color, Crowell, 1953, Wavelength, nm E, Spectral Irradiance, W/m 2 / m Exoatmospheric filename=m1695.m Sea Level 5000 K Black Body Normalized to 1000 W/m K Black Body Normalized to 1560 W/m 2
May Chuck DiMarzio, Northeastern University Tungsten Lamps: Hot is Good! 3000 K –20 Lumens per Watt – peak =1.22 m –x =.4357y =.4032 z = K note: (3400/3000) 4 =1.64) –34 Lumens per Watt note: 20X1.64=33 – peak =1.09 m –x =.4112y =.3935 z =.1953 x y
May Chuck DiMarzio, Northeastern University Quartz-Halogen Lights Tungsten Filament Higher Temperature = Brighter, Whiter –Requires Quartz Envelope –Tungsten Evaporates More Rapidly Halogen Catalyst –Prevents Tungsten Deposit on Hot Envelope –Tungsten Redeposits on the Filament Evaporation and Redeposition Requires Thicker Filament –Lower Resistance Requires Lower Voltage
Lighting Efficiency Power Input, Watts Light Output, Lumens Fluorescent Hi Pressure Na Metal Halide Lo Pressure Na Incandescent 94 Lumens/Watt at 7000K (Highest Efficiency Black Body) 20.7 Lumens/Watt at 3000K Thanks to John Hilliar (NU MS ECE 1999) for finding lighting data from Joseph F. Hetherington at com. 10 June 1998
May Chuck DiMarzio, Northeastern University Source Intensity Fraction of Light in Filter Passband –Given by Black-Body Equation –Numerical Calculation is Easiest Black Body Spectral and Integrated Flux Density Rev 2.17 by Chuck DiMarzio, Northeastern University 1992,1993,1995, to micrometers, T = K Maximum Spectral Radiant Exitance =.81762E+06 W/m^2/micron in band Radiant Exitance in Band Watts/m^2 Wide Band Radiant Exitance.45925E+07 Watts/m^2 Fraction of total in band.14244E-02 Spectrum on bbsre.dat **************************************************************************** Photocurrent per Area in Band Amps/m^ E+23 photons/sec/m^2 Average Responsivity Amps/Watt.39257E-18 Joules/photon (in band) W W
May Chuck DiMarzio, Northeastern University Incident Irradiance Mostly a Geometric Problem G describes non- uniformity –Like Antenna Gain Distance =R Power =P E = GP/(4 R 2 ) E = (1?)0.14 W/[4 0.3)m 2 ] ~ 0.12 W/m 2 Comparable to a dark cloud