Lens-less LED light has variable beam width

A student from Brunel University has developed an LED spotlight that can vary its beam without the need for a lens or reflector.

The principle of the lamp, invented by Matthew Nourse, is to mount LEDs on a series of leaves. These can then be collectively tilted towards - or away - from the beam axis by turning a collar on a screw thread. Linkages connect the collar and the leaves.

The LEDs are controlled by pulse width modulation (PWM) so that it is possible to make the outer LEDs brighter than those on the inside, in order to maintain even illumination. The LEDs are rated at 27W, which in light equivalent terms is equal to about 100W for a tungsten lamp.

The design was undertaken using SolidWorks and Cosmos FloWorks. The software predicted a working temperature of 52°C and the sand cast prototype runs at 55°C at around 20°C ambient.

The intended application is as a variable spotlight for exhibitions but the design also shows potential for use in variable beam car headlamps.

Tom Shelley

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