Equivalent sphere illumination may be used to evaluate lighting systems. The equivalent sphere illumination of a visual test object at a specific location in a room illuminated with a specific lighting system is defined as that level of perfectly diffuse (spherical) illuminance that makes the test object as visible in the equivalent sphere as it is in the real lighting environment.
Radiometers
Radiometers are used to measure radiant power over a wide range of wavelengths, including the ultraviolet, visible or infrared spectral regions.
The overall response of such detectors can be modified by using appropriate filters to approximate some desired function.
Spectrophotometers
1-3 Spectrophotometers21andspectroradiometers include two main components.
1. A monochromator separates or disperses the wavelengths of the spectrum using a prism (diffraction grating) to disperse the luminous flux into a spectrum for analysis. Any given wavelength of light is isolated by an exit slit. Monochromators often use optical glass for the visible spectrum. Measurement in the ultraviolet or infrared spectrum requires specialized quartz optical components.
2. A receptor measures the power
contained within a certain wavelength range of the dispersed light.
When a spectroradiometer measures the spectral power distribution of a radiant energy source, the radiation enters the entrance window (entrance slit) and is diffracted by the diffraction grating. The exit and focusing lens are positioned to isolate the desired wavelength. This wavelength passes through the exit slit and is measured by a photosensitive device.
Spectrophotometers measure the light reflected from the test surface. The concept and operation is very similar to that of a spectroradiometer. The
spectrophotometer compares the reflected or transmitted light to the incident light. Many spectrophotometers have a built-in light source. The values measured by any photometer depend on the quality of the incident light.
Goniophotometer
A goniometer is an instrument designed to measure an angle precisely — for example, the angle of a cutting blade, the surface tension on a drop of liquid or the range of motion of an artificial limb. Goniometers are used to triangulate the sources of radar or radio signals. If the goniometer is also a photometric instrument, it is called a goniophotometer and measures precisely the direction of light — that is, its angles of propagation and incidence.22
57
Light
TABLE4. Light measuring instruments calibrated by
National Institute of Standards and Technology (NIST). This list is subject to agency revision. Restrictions may apply.
Devices Issued by NIST
1000 W tungsten quartz halogen lamp in two-post base 30 W deuterium arc lamp in two-post base
Color temperature standard lamps Luminous intensity standard lamps Opal glass luminance coefficient standards
Spectral radiance standard, integrating sphere source Spectral radiance standard, tungsten strip lamp Standard reference photometer
Devices accepted for test or calibration
Color measuring instruments for displays Flashing light photometers
Illuminance meters
Incandescent and florescent lamps, for total luminous flux, luminous Intensity or color temperature
Lamps, for color temperature
Light emitting diodes, for luminous intensity and luminous flux Luminance meters
Luminance sources and transmitting diffusers Material, for spectral reflectance
Material, for spectral transmittance Material, for specular gloss
Material, for surface color (illuminated at normal and measured at 45 degrees to surface)
Photodetectors, for spatial uniformity of responsivity Photometers
Spectral transmittance filters (carbon yellow glass) Spectral transmittance filters (cobalt blue glass) Spectral transmittance filters (copper green glass) Spectral transmittance filters (selenium orange glass)
1. Section 2, “The Physics of Light.” Nondestructive Testing Handbook, second edition: Vol. 8, Visual and Optical Testing. Columbus, OH: American Society for Nondestructive Testing (1993): p 29-50.
2. IES Lighting Handbook: Reference Volume. New York, NY: Illuminating Engineering Society of North America (1981). Superseded by IESNA Lighting Handbook: Reference and Application, ninth edition. New York, NY: Illuminating Engineering Society of North America (2000).
3. Sayler, G.[C.] ASNT Level III Study Guide: Visual and Optical Testing Method. Columbus, OH: American Society for Nondestructive Testing (1998, revised 2006).
4. Born, M. and E. Wolf. Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light, seventh edition. Cambridge, United Kingdom: Cambridge University (1999).
5. Maxwell, J.C. A Treatise on Electricity and Magnetism, third edition (1891). New York, NY: Dover (1960). 6. Walsh, J.W.T. Photometry, third
edition. London, England: Constable (1958).
7. “General Guide to Photometry.” Illuminating Engineering. Vol. 50. New York, NY: Illuminating
Engineering Society of North America (March 1955): p 147.
8. Ohno, Y. NIST SP 250-37, Photometric Calibrations. Gaithersburg, MD: National Institute of Standards and Technology (1997).
9. Forsythe, W.E. Measurement of Radiant Energy. New York, NY: McGraw-Hill (1937).
10. CIE 81, Mesopic Photometry: History, Special Problems, and Practical Solutions (1989). Vienna, Austria: Commission Internationale de l’éclairage
[International Commission on Illumination] (CIE) (1989). 11. IESNA TM-12, Spectral Effects of
Lighting on Visual Performance at Mesopic Light Levels. New York, NY: Illuminating Engineering Society of North America (2006).
12. Wright, W.D. Photometry and the Eye. London, United Kingdom: Hatton Press (1949): p 31, 80, 123, 124.
13. CIE 18.2, The Basis of Physical Photometry, second edition. Vienna, Austria: Commission Internationale de l’éclairage [International
Commission on Illumination] (CIE) (1983).
14. ISO 31, Quantities and Units. Geneva, Switzerland: International
Organization for Standardization (2005).
15. Appendix. IES Lighting Handbook, eighth edition. Washington, DC: Illuminating Engineering Society of North America (1993): p 946-949. 16. NIST Special Publication 250, NIST
Calibration Program: Calibration Services Users Guide. Gaithersburg, MD: National Institute of Standards and Technology (2009).
17. Rosa, E.B. and A.H. Taylor. Paper 447, “Theory Construction and Use of the Photometric Integrating Sphere.” Bulletin of the NBS. Washington, DC: National Bureau of Standards [National Institute of Standards and Technology] (September 1921). 18. Buckley, H. “The Effect of Non-
Uniform Reflectance of the Interior Surface of Spherical Photometric Integrators.” Transactions of the IES. Vol. 41. London, United Kingdom: Illuminating Engineering Society (July 1946): p 167.
19. Hardy, A.C. and O.W. Pineo. “The Errors Due to the Finite Size of Holes and Sample in Integrating Spheres.” Journal of the Optical Society of America. Vol. 21. Washington, DC: Optical Society of America (August 1931): p 502.
20. IESNA LM-78, Approved Method for Total Luminous Flux Measurement of Lamps Using an Integrating Sphere Photometer. New York, NY:
Illuminating Engineering Society of North America (2007).
21. Larason, T.C. and J.M. Houston. NIST SP 250-41, Spectroradiometric Detector Measurements: Ultraviolet, Visible, and Near-Infrared Detectors for Spectral Power. Gaithersburg, MD: National Institute of Standards and Technology (2008).
22. IESNA LM-75, Goniophotometer Types and Photometric Coordinates. New York, NY: Illuminating Engineering Society of North America (2001).
58
References
Bibliography
Bureau of Naval Personnel. Basic Optics and Optical Instruments. New York, NY: Dover (1969).
CIE 17.4, International Lighting Vocabulary. Vienna, Austria: Commission
Internationale de l’éclairage [International Commission on Illumination] (CIE) (1987).
CIE 81, Mesopic Photometry: History, Special Problems and Practical Solutions. Vienna, Austria: Commission Internationale de l’Éclairage [International Commission on Illumination] (CIE) (1989).
Fowles, G.R. Introduction to Modern Optics, second edition. New York, NY: Dover (1989).
Hecht, E. Optics, second edition. Reading, MA: Addison Wesley (2001).
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Johnson, B.K. Optics and Optical Instruments: An Introduction, third edition. New York, NY: Dover (1960). Smith, W.J. Modern Optical Engineering,
fourth edition. New York, NY: McGraw-Hill (2007).
Calibration
IESNA LM-45, Electrical and Photometric Measurements of General Service
Incandescent Filament Lamps. New York, NY: Illuminating Engineering Society of North America (2000).
IESNA LM-46, Photometric Testing of Indoor Luminaires Using High Intensity
Discharge or Incandescent Filament Lamps. New York, NY: Illuminating Engineering Society of North America (2004).
IESNA LM-51, Electrical and Photometric Measurements of HID Lamps. New York, NY: Illuminating Engineering Society of North America (2000).
IESNA LM-59, Electrical and Photometric Measurement of Low Pressure Sodium Lamps. New York, NY: Illuminating Engineering Society of North America (2000).
IESNA LM-115, Guide for Reporting General Lighting Equipment Engineering Data for Indoor Luminaires. New York, NY: Illuminating Engineering Society of North America (2003).
Ohno, Y. and Yuqin Zong. “Detector- Based Integrating Sphere Photometry.” Proceedings, 24th Session of the CIE [Warsaw, Poland, 1999]. Vol. 1-1. Wien, Österreich [Vienna, Austria]: Commission Internationale de l’Éclairage [International Commission on Illumination] (CIE) (1999); p 155-160.
Color
CIE Report 15-2004, Colorimetry, third edition. Wien, Österreich [Vienna, Austria]: Commission Internationale de l’Éclairage [International
Commission on Illumination] (CIE) (2004).
CIE S 014-2; ISO 1164-2, CIE Standard llluminants for Colorimetry. Wien, Österreich [Vienna, Austria]: Commission Internationale de l’Éclairage [International Commission on Illumination (CIE)] (2006). Schanda, J. Colorimetry: Understanding the
CIE System. New York, NY: Wiley (2007).