Approved Method: Intensity Distribution Measurement of Luminaires and Lamps Using Digital Screen Imaging Photometry

Intensity Distribution Measurement of Luminaires and Lamps Using Digital Screen Imaging Photometry

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ANSI/IES LM-77-20
Document Type: Lighting Measurement and Testing (LM)

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SKU: ANSI/IES LM-77-20 Category: Tag:

Product Description

Approved American National StandardThe intent of this IES document is to describe measurement procedures for the determination of the luminous intensity distribution of certain lamps and luminaires, using a digital camera to capture the projected light distribution from a luminaire onto a screen. Many factors need to be taken into account to achieve accurate digital photometry; this report addresses the most significant of these factors. Because this is a relatively new technique, considerable detail is provided to assist the reader in understanding the principles, requirements, and limitations involved. This document addresses the use of digital cameras incorporating a CCD array. Requirements for accuracy and the special conditions for this form of light measurement are covered. The numerous factors to be taken into account for hardware selection and software development are described. Calibration requirements are specified, as are data reduction techniques.

Page count: 34 pages
Publisher: Illuminating Engineering Society (2020)
SKU: ANSI/IES LM-77-20
ISBN-13: 978-0-87995-045-3

Chapters:

  • 1.0 Introduction and Scope
    2.0 Background and Basic Principles
    3.0 Test System Geometry
    4.0 Angular Resolution
    5.0 Stray Light
    6.0 Specification of the Digital Camera
    7.0 Linearity Verification and Useable Range
    8.0 Calibration
    9.0 Test Procedure
    10.0 Data Reduction and Test Report

Citation Format:
Illuminating Engineering Society. ANSI/IES LM-77-20, Approved Method: Intensity Distribution Measurement of Luminaires and Lamps Using Digital Screen Imaging Photometry. New York: IES; 2020.

CONTENTS

  • 1.0 Introduction and Scope
  • 1.1 Introduction
  • 1.2 Scope
  • 2.0 Background and Basic Principles
  • 2.1 Noise in CCD Measurements
  • 3.0 Test System Geometry
  • 4.0 Angular Resolution
  • 5.0 Stray Light
  • 6.0 Specification of the Digital Camera
  • 6.1 Still vs. Video Cameras
  • 6.2 CCD Chip Types
  • 6.3 Shutters
  • 6.4 Data Access
  • 6.5 Dynamic Range
  • 6.6 CCD Grade
  • 6.7 Camera Controls
  • 6.8 Camera Cooling
  • 6.9 Lens Selection
  • 6.10 Spectral Correction
  • 6.11 Neutral Density Filters
  • 7.0 Linearity Verification and Useable Range
  • 7.1 Dark Field Correction
  • 7.2 Response vs. Luminance
  • 7.3 Response vs. Exposure Time
  • 7.4 Defective Pixels
  • 8.0 Calibration
  • 8.1 Lens Distortion Correction
  • 8.2 Geometric Calibration
  • 8.3 Absolute Intensity Calibration
  • 8.4 Calibration Correction for Exposure Time
  • 8.5 Relative Intensity Calibration
  • 9.0 Test Procedure
  • 10.0 Data Reduction and Test Report
  • Glossary
  • Annex A – Geometrical Relationships
  • Annex B – Lens Distortion Correction
  • Annex C – Noise Estimation
  • Annex D – Linearity Calculation Details
  • References