Radiometry:

1
????? 3 ????????????
2
?????????
Radiometry ????????????????????????????????????
?????????????? joules (energy) ??? watts
(power) Photometry ????????????????????????????
???????????????????????????????????
?????????????? lumen (energy) ??? candela
(power)
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???????????Radiometry ??? photometry
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1 Steradian
??????( solid angle) ?????????????????????? r
??????????????????????????????? r2
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spectral luminous efficiency function (human eye
response-curve )
gt Adopted by CIE (the International Commission
on Illumination ) gt conversion formula
photometric unit K(l) x radiometric unit gt
luminous Efficacy K(l) lumen/watt gtluminous
efficiency V(l) or luminous coefficient V(555
)100 --gt K 683 lm/watt
Table of V(l)
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Exercise 1

• A light bulb emitting 100 W of radiant power is
  positioned 2 m from a surface. The surface
  is oriented perpendicular to a line from the
  bulb to the surface. Calculate the irradiance
  at the surface. If all 100 W is emitted from a
  red bulb at l 650 nm. Calculate also the
  illuminance at the surface

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Lighting efficiency
1 lumen ltgt radiant energy of 1/683 watt at a
frequency of 540x1012 Hz, (standard air
wavelength of 555.016 nm )
1 candela ltgt a source that emits monochromatic
radiation of frequency 540x1012 Hz and with a
radiant intensity of 1/683 watt per steradian
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???????????????????????????????????
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???????????????????

• Thermal detectors
• Thermocouples and Thermopiles
• Bolometer and Thermistors
• Pyroelectric
• Golay cell
• Quantum detectors
• photoemissive (phototube photomultiplier tube)
• Photoconductive
• Photo voltaic
• photographic emulsion

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Bolometer

• ????????????? far-IR ??? mm wavelength region
• ?????????????????????????????????? C
  ??????????????????????????? T0 ?????????????????
  G
• ????????????? Psignal ???????????????
  ???????????????????????
• TT0 (PsignalPbias)/GgtT0.
• G - ??? Thermalink W/K
• ?????????????????????????????????????

http//bolo.berkeley.edu/bolometers/introduction.h
tml
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????????????????????????
Photo tube
Ammeter
Photo current
Anode
3I0
2I0
Photo cathode
I0
Voltmeter
V
V
V0
As a detector 1. V gt Vo 2. f gt fo ???? l lt lo
( Photo current ? photon rate )
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Photo multiplier tube
???? Photo tube ????? dynode ???????????????????
??????????
Last dynode
Vacuum
terminal
Anode
Electron multiplier (dynoes)
Photo cathode
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??????????? 1. linearity , Stability ????? 2.
??????????????????????????????????????????
photocathode 3. ???????????????????? single
photon 3. ????????????????????????? 4.
????????????????????????????? ???????????????????
??????????? 4. ????????? ???????
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??????????????? (LDR, Photocell)
gt ???????? CdS ?????????????????????????????????
?????? gt ????????????? photoconductive
(???????????????????????)
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Light response curve
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??????????? 1. ????????????? ??????? 2. ???
?????????????????????? ????????????????? 3.
????????????????????????? ????????????????????
??????????? ??????????????????????
???????????????? 4. ?????????????????????? ??????
??????? 5. Nonlinear 6. Stability ?????
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?????? P-N
i
diode
i0 ? 10-9 A
V
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??????????????????V0
V0
N
P
idrift ,e
Efn
Efp
idrift ,h
?????????
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?????? P-N ???????????
Reverse biasV-Vr
Forward bias VVf
????? V0
Vr
V0
eV0
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?????? P-N ?????????
p
n
i
W
R
e
V
I0 (???????)
I1
I2
I3
I3gt I2gt I1
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????????????????
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??????????????? P-N ???? Photodetector
i

• 1. Photovoltaic mode
• ?????????????????????????(????????)
• ???????????????????????????(??????????????)
• ???????????????????????? (log)
• ???????????????????????????

V
I0 (???)
I1
2I1
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• 2. Photoconductive mode
• ?????????????????? ????????????????????????????
• ?????????????????? ??????????????????
• ??????????????????????????
• ????????????????????????

???????????????? ??????????????
i
V
I0 (???)
I1
2I1
???????????? ?????????????????
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??????????? 1. ????????????? ???????
???????????????? Photodiode, ????????????????
,????????? 2. ????????????????????????????????
???????????????????? ?????????? 4.
?????????????????????????????? 5. Stability
?????