Systems put lamps to the optical test

Edited by the Electronicstalk editorial team Feb 9, 2005

New spectral lamp measurement systems provide a fast, accurate way to determine the optical properties of light emitting diodes, miniature lamps and laser diodes.

Pro-Lite has released the SLMS-0400 Series spectral lamp measurement systems from Labsphere, which provide a fast, accurate way to determine the optical properties of light emitting diodes (LEDs), miniature lamps and laser diodes.

The SLMS-0411 and SLMS-0421 are spectral lamp measurement systems built around a compact, 100mm diameter integrating sphere.

Each system consists of an integrating sphere, a diode array spectrometer instrument, a current-regulated power supply and Labsphere SLMS software.

The systems also include a calibrated spectral flux standard for system calibration and an auxiliary lamp, used as a control to correct for certain measurement errors.

Two different spectrometers are offered providing access to the 390-760nm (CIE colorimetric) range for visible wavelength devices (SLMS-0411), and 350-1050nm for extended coverage into the UV/blue and infra-red regions (SLMS-0421).

LEDs from 0.1 to 300 lumens (5mW to 15W approximately) can be accommodated in the 100mm sphere; a larger integrating sphere is available for testing higher powered devices.

SLMS-0400 series systems feature a Labsphere LMS-040 integrating sphere which uniformly collects the light emitted by the device under test regardless of the beam size or divergence.

The sphere is hinged to simplify internal access to the central device mount.

Directional test sources may also be measured from an external position, through a port in the sphere wall.

Some of the benefits arising from the use of an integrating sphere spectrometer in LED testing include the elimination of the characteristic photopic response matching errors with white, blue and red LEDs compared with filter based photometers, and a much-reduced sensitivity to light source alignment.

Light collected by the sphere is passed to the spectrograph, which analyses it in order to obtain a reading of the source spectral power distribution.

This spectral data is processed by the SLMS system software in order to accurately compute luminous flux and colour properties including CIE chromaticity, correlated colour temperature and colour rendering indices.

Properties particularly applicable to LEDs can also be calculated, such as peak, central, and centroid wavelength, spectral bandwidth, dominant wavelength and purity.