1、IES TM-25-13Ray File Format for theDescription of theEmission Property ofLight SourcesIES TM-25-13Ray File Format for the Description of the Emission Property of Light Sources Publication of this reporthas been approved by IES.Suggestions for revisionsshould be directed to IES.Prepared by:The Subcom
2、mittee on Ray File Format for LED Packages and Other Light SourcesIES TM-25-13Copyright 2013 by the Illuminating Engineering Society of North America.Approved by the IES Board of Directors, September 25, 2013, as a Transaction of the Illuminating Engineering Society of North America.All rights reser
3、ved. No part of this publication may be reproduced in any form, in any electronic retrieval system or otherwise, without prior written permission of the IES.Published by the Illuminating Engineering Society of North America, 120 Wall Street, New York, New York 10005.IES Standards and Guides are deve
4、loped through committee consensus and produced by the IES Office in New York. Careful attention is given to style and accuracy. If any errors are noted in this document, please forward them to Rita Harrold, Director of Technology, at the above address for verification and correction. The IES welcome
5、s and urges feedback and comments. ISBN # 978-0-87995-282-2Printed in the United States of America.DISCLAIMERIES publications are developed through the consensus standards development process approved by the American National Standards Institute. This process brings together volunteers representing
6、varied viewpoints and interests to achieve consensus on lighting recommendations. While the IES administers the process and establishes policies and procedures to promote fairness in the development of consensus, it makes no guaranty or warranty as to the accuracy or completeness of any information
7、published herein. The IES disclaims liability for any injury to persons or property or other damages of any nature whatsoever, whether special, indirect, consequential or compensatory, directly or indirectly resulting from the publication, use of, or reliance on this documentIn issuing and making th
8、is document available, the IES is not undertaking to render professional or other services for or on behalf of any person or entity. Nor is the IES undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on his or her own independent judgm
9、ent or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances.The IES has no power, nor does it undertake, to police or enforce compliance with the contents of this document. Nor does the IES list, certify, test or inspe
10、ct products, designs, or installations for compliance with this document. Any certification or statement of compliance with the requirements of this document shall not be attributable to the IES and is solely the responsibility of the certifier or maker of the statement.IES TM-25-13Prepared by the S
11、ubcommittee on Ray File Format for LED Packages and Other Light Sources of the IES Computer CommitteeTM-25 Working Group Jianzhong Jiao, Technical Coordinator IES Computer CommitteePaul Ericson, ChairI. AshdownW. BrandenburgD. ChabaudO. DrossS. GangadharaK. GarciaM. GauvinG. GregoryD. HansenK. Harag
12、uchiG. HasnaR. KelleyJ. KoshelJ. MuschaweckI.AshdownW. DauD. DiLaura*M. GauvinG. HauserR. Heinisch*R. KelleyR. KingL. LivingstonJ. McHugh*A. MorD. RandolphK. Reifers*T. SaemischD. SmithJ. Zhang* Advisory Member* Honorary MemberIES TM-25-13IES TM-25-13ContentsIntroduction .11.0 Scope .12.0 Normative
13、References 13.0 Definitions13.1 ASCII13.2 Binary.23.3 binary32 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.4 Byte 23.5 Denormalized real .23.6 Direction cosine.23.7 Fatal error23.8 Light source23.9 Littl
14、e-Endian23.10 Lumen 23.11 Luminous flux, v.23.12 NaN.23.13 Normalized real .23.14 Parser .23.15 Radiant flux 23.16 Ray .23.17 Ray direction .23.18 Ray start position .23.19 Ray-file 23.20 Signaling NaN 33.21 Stokes parameters.33.22 Tristimulus X,Y,Z 34.0 Ray-File Format34.1 File Type and Extension 3
15、4.2 Overall File Structure.34.3 Ray Ordering and Sampling .34.4 Units in File 34.5 Data Types in File34.5.1 ASCII 34.5.2 Int.34.5.3 Float.44.5.4 String 44.5.5 Unsigned Long Int 44.6 Section and Block Breakdown .44.7 Header Section .44.7.1 File Header Block.44.7.1.1 File Type.44.7.1.2 File Version 44
16、.7.1.3 Creation Method 44.7.1.4 Total Luminous Flux 74.7.1.5 Total Radiant Flux .74.7.1.6 Number of Rays .74.7.1.7 File Creation Date and Time74.7.1.8 Ray Start Position .84.7.1.9 Spectral Data Identifier84.7.1.10 Single Wavelength .8IES TM-25-134.7.1.11 Minimum Wavelength .94.7.1.12 Maximum Wavelen
17、gth 94.7.1.13 Number of Spectral Tables .94.7.1.14 Number of Additional Ray Data Items Per Ray.104.7.1.15 Size of Additional Text Block.104.7.1.16 Reserved for Future Use .104.7.2 Known Data Flags Block 104.7.2.1 Position Flag 104.7.2.2 Direction Flag104.7.2.3 Radiant Flux Flag / Stokes S0 Vector Fl
18、ag 114.7.2.4 Wavelength Flag .114.7.2.5 Luminous Flux / Y Tristimulus Flag 114.7.2.6 Stokes Flag .114.7.2.7 Tristimulus Flag 124.7.2.8 Spectrum Index Flag 124.7.3 Description Header Block124.7.3.1 Name of Light Source .124.7.3.2 Manufacturer of Light Source 124.7.3.3 Creator of Optical Light Source
19、Mode .124.7.3.4 Creator of the Ray File .134.7.3.5 Measurement Equipment / S imulation Software . . . . . . . . . . . . . . . . . . . . . . . . . . 134.7.3.6 Camera Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.7.3.7 Light Source Operat
20、ion Information .134.7.3.8 Additional Information134.7.3.9 Data Reference to Light Source Geometry134.7.4 Spectral Tables Block .134.7.4.1 Data Types144.7.4.2 Error Conditions 144.7.5 Additional Ray Data Column Labels Block .154.7.6 Additional Text Block154.8 Ray Data Section .154.8.1 Ray Data Lines
21、 Block.154.8.1.1 X Position.154.8.1.2 Y Position.154.8.1.3 Z Position.154.8.1.4 X Direction Cosine 164.8.1.5 Y Direction Cosine 164.8.1.6 Z Direction Cosine 164.8.1.7 Radiant Flux / S tokes S0 .164.8.1.8 Wavelength .174.8.1.9 Luminous Flux / Y Tristimulus 174.8.1.10 Stokes S1 174.8.1.11 Stokes S2 17
22、4.8.1.12 Stokes S3 174.8.1.13 X Tristimulus.184.8.1.14 Z Tristimulus.184.8.1.15 Spectrum Index 184.8.1.16 Additional User Defined Data 185.0 Branding Logo and Name.18Annex A File Format Selection .19Annex B Spectral Data Commentary.19Annex C Future Revisions and Compatibility 201IES TM-25-13INTRODUC
23、TIONIn the past few decades, the optical design of illumi-nation systems (non-imaging optics) has benefited greatly from the advances in computer hardware and software. Many commercially available ray-tracing optical design and simulation software programs have been developed to support a wide varie
24、ty of optical design tasks. All of these software packages can use ray files as source models. Ray files are typically generated by light source manufacturers using either an optical simulation or physical measurements using near field goniometers. These ray files are then put in a specific format f
25、or each optical design program, which allows optical engineers to integrate the light source characteristics into their optical system design simulations. Ray files describe light sources by a large number of rays with individual start location, direction, flux, and optional spectral and/or polariza
26、tion data. Ray files are mainly intended for optical engineers, who are designing optical systems using light sourc-es. Ray files are a characterization of the near field characteristics of a light source. Users may also be familiar with ANSI/IES LM-63-02 (R2008) IES Standard File Format for the Ele
27、ctronic Transfer of Photometric Data and Related Information formatted files, typically called “IES files”, which are far field characterizations of a lamp or luminaire. IES files are used by lighting application engineers to layout the lighting in a space and predict light levels. Although the far
28、field files are useful for lighting application lay-outs, they are not adequate when designing optics that are placed in close proximity to the light source.One complication in providing ray files for light source characterization is that each ray file can be very large, containing millions of rays
29、and using 250MB of data per file. Currently a manufacturer must provide ray files for all of its light sources, in up to 16 unique file formats since none of the commer-cially available ray tracing software uses the same file format. This situation leads to a large amount of data that must be create
30、d, managed, stored, and distributed to ray file users.Because all ray files store essentially the same data, the industry has come together to create a single standard ray file format that all light source manufac-turers can distribute and all optical design software can use for simulations. The for
31、mat has been created by a group that includes LED manufacturers, optical simulation software vendors, near field goniometer vendors, and academia. The new format is meant to allow simple conversion of all existing ray files into the new format, and it will be generally backward compatible in future
32、revisions.This document defines the IES standardized ray file format to describe the emission properties of light sources that can be used in all commercially avail-able design, analysis, and metrology software. 1.0 SCOPEThis document provides recommendations for a standard ray file format to descri
33、be the emission properties of light sources. The ray file format con-tains information necessary to interface between ray tracing or other optical design, simulation, analysis and metrology software used in lighting applications. 2.0 NORMATIVE REFERENCES2.1 ANSI / IES RP-16-10, Nomenclature and Defi
34、nitions for Illuminating Engineering. New York: Illuminating Engineering Society of North America, 2010. 2.2 ISO 8601, Data elements and interchange formats Information interchange Representation of dates and times. Geneva: International Organization for Standardization, 2004.2.3 IEEE 754-2008, Stan
35、dard for Binary Floating-Point Arithmetic. New Jersey: Institute of Electrical and Electronics Engineers.2.4 The Unicode Standard. California: The Unicode Consortium.2.5 The International System of Units (SI), 8th Edition, Bureau International des Poids et Mesures, 2006.2.6 ISO/IEC 8859-1:1998, Info
36、rmation technol-ogy 8-bit single-byte coded graphic character sets Part 1: Latin alphabet No. 1.3.0 DEFINITIONS3.1 ASCIIAn encoding scheme for Latin characters, according to ISO/IEC 8859-1. For the purpose of this standard, only the character 0 and characters from 32 up to and including 126, in deci
37、mal form, shall be used.2IES TM-25-133.2 BinaryAn encoding of information into certain data types in files creating a sequence of items which can be used imme-diately as data by computer processors without further conversion; the sequence of binary items is, in general, not a sequence of encoded hum
38、an readable characters.3.3 Binary 32A certain binary floating point encoding format defined in IEEE 754, using four bytes of memory per floating point number. The binary32 format is com-monly used by C and C+ compilers to implement the “float” data type.3.4 ByteA unit of digital information, consist
39、ing of 8 bits.3.4 Denormalized RealAs defined in IEEE 754, a denormalized real is a number whose absolute value is nonzero, but smaller than 1.18 1038, and thus too small to be encoded within the IEEE 754 binary32 floating point format at full mantissa resolution.3.5 Direction CosineRay directions w
40、ithin the scope of this standard shall be given as unit vectors in a three dimensional Cartesian coordinate system (a unit vector is normal-ized to have a 2-norm, or Euclidean length, of 1). Each coordinate value of a unit vector is mathematically equal to the cosine of the angle between the vector
41、and the corresponding axis. Therefore, the ray direc-tion coordinates are often called direction cosines.3.6 Fatal ErrorWhen any data in an IES TM-25 ray file shows a con-dition denoted “fatal error” within this standard, then the ray file shall be considered invalid.3.7 Light SourceAs defined in AN
42、SI/IES RP-16-10, a light source is any object producing optical radiation (electromag-netic radiation with wavelengths between approxi-mately 100 nm and 1 mm), whether man-made (and then called a lamp) or not (e.g., the sun).3.9 Little-EndianLittle-Endian refers to the ordering of individual bytes w
43、ithin larger data items, e.g., binary32 floating point numbers; the least significant byte is stored first.3.10 LumenThe SI Unit of luminous flux.3.11 Luminous Flux, vAs defined in ANSI/IES RP 16-10, luminous flux is obtained from spectral radiant flux , the spectral luminous efficiency V() and the
44、maximum spectral luminous efficacy Km = 683 lm/W by integration:v = KmV() d3.12 NaN (Quiet NaN, Signaling NaN)In computing, NaN, standing for not a number, is a numeric data type value representing an undefined or unrepresentable value, especially in floating-point calculations, per IEEE 754. If a =
45、 1, it is a quiet NaN; if a is zero and the payload is nonzero, then it is a signaling NaN.3.13 Normalized RealAs defined in IEEE 754, a normalized real is a num-ber whose absolute value is in the range between 1.18 1038and 3.4 1038, and therefore encodable within the four byte binary32 format at fu
46、ll mantissa resolution.3.14 ParserA computer program capable of syntactic analysis of a structured data file such as a ray file.3.15 Radiant FluxAs defined in ANSI/IES RP-16-10, the time rate of flow of radiant energy, expressed in Watts.3.16 RayAn idealized narrow beam of light, with negligible spa
47、tial and angular extent. Mathematically, a ray is described as a straight half-line, unambiguously given by its ray start position and its ray direction.3.17 Ray DirectionA unit vector in three-dimensional Euclidean space.3.18 Ray Start PositionA point in three-dimensional Euclidean space3.19 Ray-Fi
48、leA block of information about light sources, stored in and available from durable storage (e.g., a hard disk).3IES TM-25-133.20 Signaling NaNA set of certain binary32 values representing an undefined value, with the intent of raising an invalid exception during further processing. NaN stands for “n
49、ot a number”.3.21 Stokes ParametersFour certain numbers S0, S1, S2, and S3 are used to describe the polarization state of electromagnetic radiation along a ray, as defined in standard text books on electromagnetic radiation. They form a four-dimensional vector (S0,S1,S2,S3), called the Stokes vector. S0 is defined as the total radiant flux, S1 and S2 describe the amount and orientation of linear polarization, while S3 describes the amount and orientation of circular polarization. For unpolar-ized light, S1=S2=S3=0, and for fully polarized light S12+ S22+ S32= S0
