CHECKING A DEVICE HAVING A PLURALITY OF LIGHT EMISSION ELEMENTS

Apparatus including:- a light emission arrangement (4,13), with a plurality of elements (21), such as LEDs, each operable to provide for controlled light emission; a driver (20, 35) for driving each of the plurality of elements (21) to provide controlled light emission; a target object (1), towards which light emission is directed; and means for checking the functioning of the elements of the plurality in situ, comprising:- a test generator (30, 32), operable to generate pulses for causing all of the elements (21) of the plurality to provide light emissions, one by one, each element in turn, a detector (14, 22, 14; 22; 14, 23,14; 25; 26; 27, 28), operable to detect light emissions provided from any of the elements (21) of the plurality and to provide output signals dependent upon the intensities of the detected emissions, and a processor (30 min , 42, 43, 33), operable to process output signals from the detector to provide data representing functional characteristics of each of the elements (21). A method of checking light emission elements in situ is also provided.