Design and implementation of real-time LED spatial radiance measurement systems

Gao Wei Chang*, Zong Mu Yeh, Chia Cheng Liao

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Light-emitting diodes (LEDs) have been recognized as a generation of new light sources because they possess the properties of energy-saving, environmental protection, long lifetime, and those lacking in conventional lighting. To satisfy the requirements for different applications (e.g., for large-scale displays), determining the spatial radiances of LEDs is important to identifying their viewing angle and utilizing their lighting efficiency. The objective of this paper is to build up a real-time spatial radiance measurement system for LEDs, on the basis of digital signal processing (DSP) techniques. In this paper, the system analysis is given to show the feasibility of this work. Two primary subsystems are devised to perform the real-time measurements. First, in the optoelectronic sensing and signal processing subsystem, a wide-bandwidth photodiode sensing circuit is employed to acquire optical signals at a high speed, and an automatic gain control (AGC) circuit is designed to increase the measurement range. To support high-speed data processing, a DSP-based platform is developed in the subsystem. Second, a light-source rotation scheme is used in the optomechanical subsystem. For performance evaluations, we adopt a standard calibrating light source to test and verify our system. Experimental results indicate that the proposed system gives satisfactory results.

Original languageEnglish
Title of host publicationLight-Emitting Diodes
Subtitle of host publicationResearch, Manufacturing, and Applications XI
ISBN (Print)0819465992, 9780819465993
Publication statusPublished - 2007
EventLight-Emitting Diodes: Research, Manufacturing, and Applications XI - San Jose, CA, United States
Duration: 2007 Jan 242007 Jan 25

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherLight-Emitting Diodes: Research, Manufacturing, and Applications XI
Country/TerritoryUnited States
CitySan Jose, CA


  • LED
  • Real-time measurement
  • Spatial radiance

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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