LED Light Measurement

The most common method for measuring the total luminous flux of any source included OLEDs and LEDs is using an integrating sphere spectrometer. The integrating sphere spectrometer is calibrated with a standard of total spectral flux employing the comparison method made simple with application based software, a calibrated standard lamp of known output, commonly referred to as the "comparison method". The results of this comparison determine the light output test lamp.

For directional applications, LED intensity and spatial distribution are the most important parameters. For intensity measurements a precision entrance port into a near cosine sphere detector is configured for Condition A or B measurements where the device is located 31.6 cm or 10 cm respectively away from the entrance port of the sphere intensity head. The head is coupled with a spectrometer with application based software calibrated for spectral intensity responsivity.

Spatial distribution is a measurement of intensity as a function of viewing angle. This measurement is traditional performed by holding the test lamp stationary and swinging a small-aperture detector in an arc about the DUT. A complete hemispherical characterization of the device can be assembled by rotating the plane of measurement with respect to the device, and repeating this test for a number of meridional angular scans.

Another common method is holding the detection system stationary and rotating the DUT in a goniometric stage. The data normalized to the normal reading and typically imported into ray tracing programs for device modeling.