scope:

Description

Light emitted from the device under test is allowed to fall onto an optical detector. The range of optical wavelengths falling on the detector is restricted ·by an optical filter of specified optical range placed between the detector and the LED. The quantum efficiency of the detector across the range of wavelengths defined by the optical filter must be known. The ratio of the diameter of the collection aperture to the distance between the device under test and the centre of the collection aperture is set at the specified value. The device under test, aperture, filter and detector are all positioned co-axially. The collection aperture is. defined by the detector or by an external aperture between the LED and detector. If an external aperture is used all the light passing through it must fall on to the detector.