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Approved American National StandardThis document is an update of LM-75-2001, which was reaffirmed in 2012. The document has been updated to reflect current use of goniophotometers in industry, including calibration methods and methodologies for correction of stray light. Updated in this document are definitions of goniophotometer types and coordinate systems for photometric measurement of light sources. This document supersedes any angular conventions presented in LM-72-1997. This document does not cover near-field goniometers.

A goniophotometer is a photometer for measuring the directional light distribution characteristics of sources, luminaires, media and surfaces. A goniophotometer records photometric readings at a series of spherical coordinates to define a web of photometric data surrounding the item under test. Goniophotometric data are presented using various angular coordinate systems, and acquired using instruments of various constructions. In addition to goniophotometers, goniocolorimeters exist, which use three- or four-channel colorimeters to measure color properties at a series of spherical coordinates, and goniospectroradiometers exist, which use array spectrometers to measure spectral properties at a series of spherical coordinates. Historically, each type of goniophotometer was developed to measure a light source used in a specific application. Conventionally, measurement results for each type of light source were presented using a coordinate system that matched the specific application. Many current IES documents mention goniophotometers and coordinate systems. This document offers a complete explanation and provides harmonious definitions.

Secure PDF: 28 pages
Publisher: Illuminating Engineering Society (2019)
ISBN-13: 978-0-87995-010-1
Dimensions: 8½” x 11″