White Paper: Test & Measurement

Continuous Versus Discrete Calibration Sources: Considerations for Use

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Radiometric and photometric calibrations have relied on lamp-based sources of radiant flux for decades. Lamps that produce a broad continuum of radiation serve as spectral calibration sources for systems measuring a myriad of radiometric or photometric quantities, while lamps that have very well characterized and sharp spectral features can be used as a wavelength calibration source. Since the mid-20th century, lamp-based calibration standards have proven themselves as dependable tools for calibrating light sensors, imaging cameras, solar cell or detector characterization, and more.

Recently, rapid advancements in the field of solid-state lighting have presented opportunities for the use of LED-based systems for calibrations typically performed with lamp-based sources. Their highly efficient and long-lived performance, rapid power up, and compact size have made LED-based sources an attractive alternative for lamp-based calibration systems. However, replicating the precision performance of lamp-based system, particularly in terms of the output intensity and stability, pose several challenges for LED-based calibration systems.

The purpose of this information sheet is to explore the feasibility of using LED-based sources of radiant flux for calibrations that have been ubiquitously performed by lamp-based standards. A comparison of the two methods will be discussed, as well as the recent offerings by Optronic Laboratories, LLC utilizing LEDs in lieu of lamp-based systems.

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