Abstract: An LED array and a method for controlling such an array is described. The array includes one or more LED-optical sensor pairs in which the optical sensor measures the light output of the associated LED. In some forms of the invention, the optical sensors are provided with filters to attenuate light at a wavelength different to that of the LED associated with that optical sensor. In some forms of the invention, the LED-optical sensor pairs are at least partially shielded from extraneous light. In one form of the invention a plurality of sets of LEDs is provided, each set outputting light having a different frequency and each set being controllable to provide a desired light output.

Abstract: An LED array and a method for controlling such an array is described. The array includes one or more LED-optical sensor pairs in which the optical sensor measures the light output of the associated LED. In some forms of the invention, the optical sensors are provided with filters to attenuate light at a wavelength different to that of the LED associated with that optical sensor. In some forms of the invention, the LED-optical sensor pairs are at least partially shielded from extraneous light. In one form of the invention a plurality of sets of LEDs is provided, each set outputting light having a different frequency and each set being controllable to provide a desired light output.

Abstract: A light emitting semiconductor device mounted on a heat sink and having a heat pipe located on its upper surface. The heat pipe comprises a sealed cylindrical member of transparent or translucent material having a wick disposed down the side and along the bottom thereof. The heat is partially filled with a liquid which is placed under a partial vacuum to reduce its boiling point. A bundle of optical fibres may be provided within the heat pipe, with the gaps created between the optical fibres providing an efficient capillary action within the heat pipe for transport of vapour to the cool end of the pipe and for transport of condensed coolant to the hot end of the pipe.

Abstract: A cooled light emitting apparatus 1 comprises a light source including a close packed array 2 of light emitting diode device (high intensity LEDs) and a cooling system for cooling the light source. The cooling system comprises a thermoelectric cooling device in the form of a Peltier device 4 connected via a heat spreader 3 to the light source and a heat exchange system 5, 6 for removing heat from the Peltier device 4. The heat exchange system 5,6 uses liquid coolant (or refrigerant) to cool the Peltier device 4. By extracting heat from the LED array 2 at a rate greater than 5 W cm?2 it is possible to maintain the LED array at a temperature of less than ?10 degrees Celsius, and thus emit light having an optical power density of greater than 1 Wcm?2.

Abstract: Method and device for treatment of skin conditions A method and apparatus for improving the cosmetic appearance of a region of skin 11 affected by Acne Vulgaris, Rosacea or similar skin condition by means of directing light radiation 12 from an illuminating device 1 on to the skin 11. The apparatus 10 comprises a control unit 9 that operates one or more LEDs 7 (light emitting diodes) of the illuminating device 1. Each dose of light radiation 12 lasts for at least 100 ms, during which time the skin 11 receives light energy from the LED(s) 7, which causes a photochemical reaction that stimulates the production of free radicals (singlet oxygen) that react with, and at least partially disable or destroy, bacteria that contribute to the symptoms of the skin condition. The light energy directed on to the skin 11 during any given period of 10 ?s is less than 0.5 Jcm?2, and during any given period of 100 ms is less than 5 Jcm?2. Substantially no beneficial photo-thermal reaction occurs within the skin 11.

Abstract: Two and three terminal semi-conductor barrier switching devices are disclosed in which a semi-conductor junction or a Schottky barrier is used to inject carriers towards a barrier formed by a narrow layer doped to have majority carriers of the type injected. In the non-conducting state the barrier prevents conduction but as an applied bias is increased the barrier begins to allow carriers of the opposite type to pass releasing the first mentioned carriers and causing the barrier height to be reduced. This action becomes regenerative with increasing bias and after passing through a negative resistance region, the device enters its conducting state. When the third terminal is present the device is made conducting by biasing its third terminal to cause carriers of the first mentioned type to be injected into the barrier region for example from a diffusion adjacent to the third terminal.