IESNA LM-75-2001 Goniophotometer Types and Photometric Coordinates.pdf

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1、I LM=75101 I I Goniophotometer I l A Types and 4I Photometric Coordinates The LIGHTING Prepared by: Prepared by the Subcommittee on Photometry of Outdoor Luminaires of the IESNA Testing Procedures Committee AUTHORITY I IESNA LM17501 Goniophotometer Types and Photometric Coordinates Publication of th

2、is Committee Report has been approved by the IESNA. Suggestions for revisions should be directed to the IESNA. Prepared by: Prepared by the Subcommittee on Photometry of Outdoor Luminaires of the IESNA Testing Procedures Committee IESNA LM-75-01 Copyright 200 7 by the Illuminating Engineering Societ

3、y of North America. Approved by the IESNA Board of Directors, August 4 , 2007, as a Transaction of the Illuminating Engineering Society of North America. All rights reserved. No part of this publication may be reproduced in any form, in any electronic retrieval system or otherwise, without prior wri

4、tten permission of the IESNA. Published by the Illuminating Engineering Society of North America, 120 Wall Street, New York, New York 10005. IESNA Standards and Guides are developed through committee consensus and produced by the IESNA Office in New York. Careful attention is given to style and accu

5、racy. If any errors are noted in this document, please for- ward them to Rita Harrold, Director Educational and Technical Development, at the above address for verification and correction. The IESNA welcomes and urges feedback and comments. ISBN # 0-87995-1 80-X Printed in the United States of Ameri

6、ca. IESNA LM-75-01 Prepared by the Subcommittee on Photometry of Outdoor Luminaires of the IESNA Testing Procedures Committee Subcommittee on Photometry of Outdoor Luminaires Carla Ooyen, Chair J. B. Arens R. C. Dahl* M. L. Grather D. E. Husby* C. P. Latsis* C. H. Loch P. G. McCarthy S. W. McKnight*

7、 R. C. Speck* IESNA Testing Procedures Committee James Walker, Chair J. Arens L. Ayers* W. Beakes R. Berger* R. Bergin R. Bergman R. Blanchette J. Clegg* K. Coke R. Dahl* R. Daubach D. Ellis J. Evans R. Gibbons* M. Grather R. Horan D. Husby* R. Kimm* C. Latsis* R. Levin* I. Lewin* C. Loch R. Low* L.

8、 Lin P. McCarthy G. McKee S. McKnight* D. Merk* Y. Ohno C. Ooyen D. Rector J. Sard* D. Smith* R. Speck* L. Stafford* E. Steeb* N. Stuffer* S. Treado* T. Yahraus J. Zhang *Advisory *Honorary IESNA LM-75-01 CONTENTS Introduction . 1 Background . 1 1.0 Spherical Coordinates . 1 2.0 Coordinate Systems 2

9、 2.1 Type A Coordinates 2 2.2Type B Coordinates 3 2.3 Type C Coordinates 3 3.0 Goniophotometers . 3 3.1 Horizontal Axis (Type A) 3 3.2Vertical Axis (Type B) . 4 3.3 Moving Detector or Mirror Goniophotometer (Type C) . 4 3.3.1 Moving Detector Goniophotometer . 4 3.3.2 Moving Mirror Goniophotometer .

10、4 References 5 Annex A . 6 IESNA LM-75-01 IESNA LM-75 1.0 SPHERICAL COORDINATES , Il Goniophotometer Types and Photometric Coordinates INTRODUCTION A goniophotometer is a device used to measure the directional light distribution characteristics of sources, luminaires, media, and surface. A goniophot

11、ometer measures data at a series of spherical photometric mr- dinates in order to define a web of photometric data sur- rounding the light source. Goniophotometer and mrdi- nate types are normally divided into three categories: Types A, B, and C. Originally, the different goniopho- tometer types wer

12、e designed to match the type of source being measured. Data were measured and reported in corresponding photometric coordinates. With the advent of position sensitive lamps, certain sources could no longer be tested on the traditional goniophotometer type; however, data still needed to be reported i

13、n the tradition- al photometric coordinate iype. Fortunately, though a goniophotometer type is often thought of as generating a specific coordinate iype, in actuality, any goniophotome ter can be used to generate any coordinate system, with varying degrees of difficulty. This document will define th

14、e three photometric coor- dinate systems and explain when each is used. The operating principles behind each of the three types of goniophotometers will also be addressed. The information presented here grew out of a need to further describe the types of goniophotometers avail- able for photometric

15、testing, as well as the coordinate systems used to describe photometric data. These terms are fundamental to the study of photometry, but their explanation has often been left to oral tradition. For example, it is convenient and traditional to describe coordinate systems in the vernacular of hor- iz

16、ontal and vertical because this is the common mode of use. Coordinate systems fundamentally do not relate to the horizontal and vertical. Rather, they relate to a plane and a normal to that plane. Many current IESNA documents mention goniophotometers and coordinate systems, but none of them, includi

17、ng the IESNA Lighting Handbook, Ninth Edition and LM-35- 7989,1,2 offer a complete explanation or provide har- monious definitions. This document provides a solu- tion and is in agreement with CIE 102 and 121 ?,4 The three coordinate systems used in photometry are variations on the standard spherica

18、l coordinate sys- tem used in mathematics. A point in space is described by the following coordinates: (P, 094) The first coordinate p (rho) denotes a points distance from the origin. When describing points on a sphere, as in photometry, p is constant; therefore, this coordi- nate will not be consid

19、ered further. The two remaining coordinates are defined as they pertain to common photometric terminology: Half plane of data - The data points described by rotating from pole to pole within a half plane (180 degrees of rotation). The half plane does not extend beyond the polar axis. (See Figure 1 .

20、) The coordinate 8 (theta) is the angle between the polar axis and the data point. n /A- _/- Figure 1. Half Plane of Data Angle to plane -The angular rotation about the polar axis required to locate each plane of data. (See Figure 2.) This is the coordinate 4 (phi) in mathemat- ical notation. Refere

21、nce plane - The half plane that identifies the starting point for measuring the angle to the plane. (See Figure 2.) For the reference plane, the coordi- nate 4) (phi) is equal to zero. The location of the refer- ence plane is dependent upon the application and should always be clearly defined. 1 IES

22、NA LM-75-01 , - /- A . / /. / Polar Axis Figure 2. Angle to Plane Polar axis - The line about which rotation occurs to locate the half planes. Spherical coordinates may seem like an unfamiliar concept, but in reality they may be more familiar than one realizes. Latitude and longitude, another form o

23、f spherical coordinates, are used to identify the location of a point on Earth. The angles measured in the verti- cal half planes are the angles of latitude and range from 90“s to O“ to 90“n. The horizontal angles to the plane are the angles of longitude and progress from 180“w to O“ to 180“e. To cl

24、arify the explanation of the three photometric coordinate systems, examples in the following text relate back to the coordinates of places on Earth. The map of the earth, shown in Figure 3, marks several locations, which will be refer- enced again in the discussion of photometric coordi- nates. In g

25、eographic terminology, Greenwich, England is located at (51 On, O“e).The South American city of Quito, Ecuador has a geographic location of (Os, 78“w). On the remote Pacific Isle of Fiji, the town of Suva is situated at (16“s, 180“e). The geographic origin (On, Ooe) lies off the African coast deep i

26、n the waters of the Gulf of Guinea. On the frozen continent of Antarctica, the geographic South Pole is designat- ed as (goos, Ooe). 2.0 COORDINATE SYSTEMS 2.1 Type A Coordinates In the Type A coordinate system the polar axis is ver- tical, as shown in Figure 4. The angles measured in the vertical h

27、alf planes are labeled Y angles, while the horizontal angles to the half planes are called X angles. Locations on the sphere are denoted by their (Y, X) coordinate pair. Point (0,O) is located on the equator of the sphere. In photometry, the luminaire is generally aimed at (OV, OX), such that the 0“

28、X plane is perpendicular to the light opening of the luminaire. The vertical Y angles range from -90“ (nadir) to 90“ (zenith). The horizontal X angles range in value from - 180“ to 180“, as shown in Figure 4. Automotive light- ing and optical systems testing are presented in Type A coordinates. , Fi

29、ji South Pole Figure 3. Geographic Coordinates 2 Figure 4.Type A Coordinates. Arrows indicate photometric angles. Using the Type A coordinate sys- tem to describe locations on Earth, Greenwich, England is located at (51Y, OX), Quito, Ecuador is at (OY,78X), and Suva, Fijis coordinates would be (-1 6

30、V, 180X). That point in the Gulf of Guinea would have Type A coor- dinates of (OY, OX), while the loca- tion of the geographic South Pole is (-goy, OX). IESNA LM-75-01 I, 2.2 Type B Coordinates The Type B coordinate system is illustrated in Figure 5. The polar axis is horizontally oriented. This coo

31、rdi- nate system looks much like a Type A coordinate sys- tem that has been turned on its side. The angles mea- sured in the horizontal half planes of data are called Horizontal angles, and the vertical angles to the half planes are Vertical angles. Locations on the sphere are denoted by their (H, V

32、) coordinate pair. O“H is on the equator of the sphere. Point (0,O) is normally the aiming point of a luminaire, and the 0“V plane is per- pendicular to the luminaire light opening. The H angles range from -90“ to go“, as shown in Figure 5. The vertical V angles range in value from -180“ to 1 80, wh

33、ere -90“ would be at nadir and 90“ at zenith. Floodlight photometric data is traditionally presented in Type B coordinates. 1wIv 4 Figure 5. Type B Coordinates. Arrows indicate photo- metric angles. Were the locations on the Earth to be described in Type B coordinates, Greenwich would be at (OH, 51V

34、), Quito at (78H, OV), and Suva, Fiji at (OH, - 164V). Point (OH, OV) would still be located in the Gulf of Guinea, while the South Pole would be designated 2.3 Type C Coordinates by (OH, -90V). With the Type C coordinate system, the polar axis is vertical, as shown in Figure 6. The Type C coordinat

35、e system varies little from the Type A system. The angles measured in the vertical half planes of data are called Vertical angles, and the angles to the hori- zontal half planes are called Lateral angles. The Type C coordinate pair (OV, OL), where the luminaire is nor- mally aimed, is located at nad

36、ir. The vertical V angles range in value from O“ (nadir) to 180“ (zenith).The lat- eral L planes range in value from O“ to 360“, as shown in Figure 6. In photometry, the 0“L reference plane is normally positioned parallel to the primary axis of the luminaire. Type C photometric data is the most popu

37、- lar and widely recognized. The majority of photomet- ric data, including data for indoor and roadway lumi- naires, is presented in Type C format. ry,9oL) Figure 6. Type C Coordinates. Arrows indicate photo- metric angles. Were the locations on the Earth to be described in Type C coordinates, Green

38、wich would be at (141V, OL), Quito at (9OV, 282L), and Suva, Fiji at (74V, 18OL). That point in the Gulf of Guinea would be at (9OV, OL). The South Pole would have coordinates of (OV, OL). 3.0 GONIOPHOTOMETERS 3.1 Horizontal Axis (Type A) With this goniophotometer system, the photodetector is fixed

39、while the luminaire is rotated about the X and Y-axes, as shown in Figure 7. When this type of goniophotometer is used to create a Type A web of data (Figure 4), the luminaire is normally aimed at the equator (OY, OX). To create data in Type A coordinates with a Type A goniophotometer, the luminaire

40、 is first rotated about the x-axis to the desired X coordinate. The luminaire is then rotated about the y-axis, through the full range of Y coordinates, until a full plane of data has been gathered. This process is repeated until the luminaire has been positioned at all X coordinates. Because the Ty

41、pe A goniophotometer relies on tilting the luminaire in order to take measurements, its use has become more restricted with the advent of posi- tion sensitive lamps. 3 IESNA LM-75-01 Figure 7. Type A Goniophotometer. Arrows indicate direction of luminaire rotation. 3.2 Vertical Axis (Type B) The pho

42、todetector is also fixed with the Type B gonio- photometer (Figure 8). The luminaire is rotated about the V and H axes. When this type of goniophotometer is used to create a Type B web of data (Figure 5), the luminaire is normally aimed at the equator. When using aType B goniophotometer to gather da

43、ta in Type B coordinates, the luminaire is first rotated about the V axis to the target V coordinate. The luminaire is then rotated about the H axis, through the full range of H coordinates, until a full plane of data has been mea- sured. This process is repeated until the luminaire has been positio

44、ned at each V coordinate. Like the Type A goniophotometer, the Type B goniophotometer tilts the luminaire in order to take measurements; therefore, its use with position sensitive lamps is restricted. PHOTODETECTOR & H+ I Figure 8. Type B Goniophotometer. Arrows indicate direction of luminaire rotat

45、ion. 3.3 Moving Detector or Mirror Goniophotometer (Type C) A Type C goniophotometer is shown in Figure 9. It is characterized by having the luminaire suspended in a fixed orientation in space, movable only around a ver- tical L-axis. Either the photodetector or a mirror is rotated around the lumina

46、ire (around the V-axis) in a vertical plane. The elimination of the tilting of the lumi- naire makes the Type C goniophotometer ideal for measuring the light output of position sensitive lamps. 4 PHOTODETECTOR or MIRROR I Figure 9. Type C Goniophotometer. Arrows indicate direction of luminaire rotat

47、ion. When this type of goniophotometer is used to create the Type C web of data (Figure 6), the luminaire is normally aimed at nadir. The luminaire is rotated about the L axis to the desired Lateral angle, then the mirror or photodetector is rotated about the horizontal V-axis to obtain a plane of V

48、ertical data. This process is repeated until all data have been gathered at all desired Lateral planes. When this type of goniopho- tometer is used to create the Type A web of data (Figure 4), the procedure is the same except that the luminaire is normally aimed at the equator. 3.3.1 Moving Detector

49、 Goniophotometer. This device consists of a photodetector that moves verii- cally on a rotating boom or arc shaped track, where the light source is positioned at the center of the arc traced by the detector. Readings are collected with the detector positioned at the desired angular set- tings. Sometimes multiple detectors on an arc replace the rotating boom. (See Figure 10.) PIVOT BOOM OR TRACK PHOTODETECTOR SIDE ELEVATION Figure 10. Schematic side elevation of a moving detector photometer 3.3.2 Moving Mirror Goniophotometer. In this iype of goniophot