KIRKLAND, Wash., May 20, 2008 -- Orb Optronix now offers complete optical, thermal and electrical characterization of LEDs through its expanded test-and-measurement laboratory.

To determine the true operational performance of LEDs, it can measure spectral output under thermal conditions over a range of forward-drive currents with high-precision forward voltage (Vf) monitoring.

David Jenkins, Orb president, said, “For many applications today, this level of characterization is absolutely necessary, particularly in LED display technology, medical devices and LED lighting applications. We employ two types of temperature control for different purposes: Ambient air temperature control is used primarily for characterizing product or subsystem level performance, while thermoelectric cooler (TEC) temperature control is used primarily for component level characterization of discrete LEDs and LED arrays.”

The spectral radiant flux of an LED is a function of variables including temperature, current and forward voltage, each as a function of time. These lead to additional variables when frequency and duty cycle for pulse width modulated current (PWM) control are included.

"High-power LED manufacturers are currently specifying optical output of their LEDs under short single-current pulse conditions," the company said in a statement. "Today’s high-power LED specification sheets generally assume that the junction temperature is equal to the ambient air temperature of 25° C. Although these tests are easily repeatable, they are not particularly useful to engineers designing LEDs into illumination and display products."

The decrease of luminous flux and shift in wavelength at increasing temperatures is highly variable and depends on the properties of LEDs, Orb said.  "NIST’s Optical Technology Div. is conducting research to address this important issue and recommends LED characterization be performed under TEC control. This information is necessary when designing robust LED-based products with specific desired light output and lifetime characteristics."

For more information, e-mail: sales@orboptronix.com

Orb Optronix Inc.
1003 7th Ave., Suite B
Kirkland, WA 98033
Phone: (425) 605-8500

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