High-Speed System Offers Optical Measurement for LEDs

Brent D. Johnson

With any new product, it is critical to establish a sense of trust and reliability with the consumer. A few minor glitches in the initial rollout could doom an emerging technology, no matter how promising its prospects, which is why test and measurement has been one of the consistent performers in the photonics industry. Manufacturers realize that new technologies require an assurance of longevity and consistent performance above the mean.

LED manufacturer Microsemi Corp. uses the OmniLED LMS system to test its products at a rate of up to 200 units per minute.

Microsemi Corp. of Watertown, Mass., a recent entrant into the high-performance LED sector, needed to verify the quality of its products but had limited experience with test-and- measurement methods for LEDs. It measured and sorted its line of Optomite blue, red and green and its UPWLEDxx white LEDs using Ismeca high-speed material handlers. The challenge was to add the OmniLED LMS measurement system from Labsphere Inc. of North Sutton, N.H., to this process so that the LEDs could be tested at speeds of up to 200 units per minute.

The OmniLED LMS consists of a high-speed CCD-based spectrograph, a radiometer, a Spectralon optical head and software. In high-speed mode, the handling device presents the LED to the optical head. A signal initiated by the handler prompts the system to power the LED, measure the optical radiation and collect a variety of measurements.

OmniLED LMS has an optical head that can be used with an integrating sphere to measure either flux or intensity at the same time that the system collects spectral data. Because Microsemi produces LEDs for illumination and signaling, it must perform both flux and chromaticity measurements, so the company has opted for a spectrometer attachment rather than a correcting filter. This enables the rapid measurement of X,Y chromaticity coordinates, dominant wavelength, correlated color temperature and color-rendering index.