Angular Response Measurements of a Bentham DMc150...
Transcript of Angular Response Measurements of a Bentham DMc150...
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Angular Response Measurements of a Bentham DMc150 Spectroradiometer
Ewan Eadie1, Hannah Oliver1, Julie Smyth2, Harry Moseley1
1Photobiology Unit, Ninewells Hospital and Medical School, Dundee2 Medical Physics, Ninewells Hospital and Medical School, Dundee
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Spectroradiometers & Radiometers
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Calibration
Correct for errors Human: Poor calibration procedures, improper maintenance, stray light from poor technique, inaccurate lamp orientationEquipment: Non-linearity, aging, directional response, temperature
Evaluate remaining uncertainty
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Spectroradiometer Response
Depends on:Direction of incident radiationTemperature of Photomultiplier TubeUniformity of irradiation
Spectroradiometer used for a range of different source geometriesIdeal Cosine response
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Angular Responsef2 error: quantifies the quality of the spectroradiometers directional evaluation of the incident radiation
Pye, S.D. and Martin, C.J.: A study of the directional response of ultraviolet radiometers.
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f2
*2f
( ) ( )( )
( ) εεε
εεϕε
ϕε
ε
dff
RR
freading
reading
∫=
=
−=
=
309.1
0
22
2
2sin(%)
1cos0
,,
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Background
Yearly calibration of our Bentham DMc150 spectroradiometerTwo calibrated lamps
Bentham CL3 30W deuterium lampBentham CL2 100W quartz halogen lamp
Two diffusersPTFE diffuserQuartz diffuser
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UV Radiometer Calibration
Deuterium Lamp
Quartz Halogen Lamp
Lamp
Diffuser
PTFE Quartz
200 < λ
< 325
325 < λ
< 600 600 < λ
< 800
-
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Angular Response of PTFE and Quartz Diffusers
0
0.2
0.4
0.6
0.8
1
1.2
0 10 20 30 40 50 60 70 80Angle (degrees)
Rela
tive
Inte
nsity
Cosine
PTFE 500nm
PTFE 600nm
PTFE 700nm
PTFE 800nm
Quartz 500nm
Quartz 600nm
Quartz 700nm
Quartz 800nm
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Angular Response Measurements
Bentham DMc150 SpectroradiometerPTFE/Quartz diffuserQuartz Halogen LampAngular “Jig”
Distance = 50cmVertical AlignmentHorizontal
±0° - 75°
Vertical ±0° - 70°
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Angular Response Measurements
Bentham DMc150 SpectroradiometerPTFE/Quartz diffuserQuartz Halogen LampAngular “Jig”
Distance = 50cmVertical AlignmentHorizontal
±0° - 75°
Vertical ±0° - 70°
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Horizontal Measurements
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Vertical Measurements
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Results
4 readings for each angleHorizontal ±εVertical ±ε
Average R(ε)Relative Response: ( )
( )0=εε
RR
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Angular Response of PTFE and Quartz Diffusers
0.000
0.200
0.400
0.600
0.800
1.000
1.200
0 10 20 30 40 50 60 70 80
Angle (degrees)
Rel
ativ
e R
espo
nse
CosinePTFE 500nmPTFE 600nmPTFE 700nmPTFE 750nmPTFE 800nmQuartz 500nmQuartz 600nmQuartz 700nmQuartz 750nmQuartz 800nm
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UV Radiometer Calibration
Deuterium Lamp
Quartz Halogen Lamp
Lamp
Diffuser
PTFE Quartz
200 < λ
< 325
325 < λ
< 600 600 < λ
< 800
-
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Angular Response of PTFE and Quartz Diffusers
0.000
0.200
0.400
0.600
0.800
1.000
1.200
0 10 20 30 40 50 60 70 80
Angle (degrees)
Rel
ativ
e R
espo
nse
CosinePTFE 500nmPTFE 600nmPTFE 700nmPTFE 750nmPTFE 800nmQuartz 500nmQuartz 600nmQuartz 700nmQuartz 750nmQuartz 800nm
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PTFE f2f2 error
0
5
10
15
20
25
30
35
(%)
250nm300nm350nm400nm450nm500nm550nm600nm650nm700nm750nm800nm
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Quartz f2f2 error
0
5
10
15
20
25
30
35
(%)
250nm300nm350nm400nm450nm500nm550nm600nm650nm700nm750nm800nm
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Angular Correction Factor CF(ε)
True irradiance underestimatedApply a correction factorDepends on
Wavelength (PTFE)Average between 250nm and 500nm
Range of anglesSource geometry
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Angular Correction Factor CF(ε)
Source Range of Angles
Bank of 6 x 180cm lamps ±
0°
to 70°
Single 180cm lamp ±
0°
to 70°
Ninewells UVA1 Bank 8 x 60cm ±
0°
to 35°
Dr Honle Column ±
0°
to 60°
Single 60cm lamp ±
0°
to 35°
Dr Honle Dermalight Ultra 1 ±
0°
to 20°
Deuterium Lamp n/a
QHT lamp n/a
Dr Honle lamp n/a
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Angular Correction Factor CF(ε)
Source CF(θ)
Bank of 6 x 180cm lamps 1.07
Single 180cm lamp 1.04
Ninewells UVA1 Bank 8 x 60cm
1.03
Dr Honle Column 1.03
Single 60cm lamp 1.02
Dr Honle Dermalight Ultra 1 1.01
Deuterium Lamp n/a
QHT lamp n/a
Dr Honle lamp n/a
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Conclusions
250nm to 750nm: PTFE diffuser better represents a cosine responseResponse with PTFE is wavelength dependentAngular correction factor, CF(ε), included in UV radiometer calibrationsUncertainty in CF(ε) = 0.4%
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Conclusions
250nm to 750nm: PTFE diffuser better represents a cosine responseResponse with PTFE is wavelength dependentAngular correction factor, CF(ε), included in UV radiometer calibrationsUncertainty in CF(ε) = 0.4%
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Conclusions
250nm to 750nm: PTFE diffuser better represents a cosine responseResponse with PTFE is wavelength dependentAngular correction factor, CF(ε), included in UV radiometer calibrationsUncertainty in CF(ε) = 0.4%
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Conclusions
250nm to 750nm: PTFE diffuser better represents a cosine responseResponse with PTFE is wavelength dependentAngular correction factor, CF(ε), included in UV radiometer calibrationsUncertainty in CF(ε) = 0.4%
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References
1. Methods of characterizing the performance of radiometers and photometers. CIE No 53. 1982
2. Methods of characterizing illuminance meters and luminance meters. Performance, characteristics and specifications. CIE No 69. 1987
3. Pye, S. D. and Martin, C. J. A study of the directional response of ultraviolet radiometers: I. Practical evaluation and implications for ultraviolet measurement standards. Phys. Med. Biol. 2000
4. Martin, C. J. and Pye, S. D. A study of the directional response of ultraviolet radiometers: II. Implications for ultraviolet phototherapy derived from computer simulations. Phys. Med. Biol. 2000
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Acknowledgements
Dr Harry MoseleyProfessor James FergusonPhotobiology Unit, Ninewells Hospital and
Medical School, DundeeChristine Wall, Teresa Goodman, Laura
Crane and Paul Miller