| US7976204B2 | 2011-07-12 | |||
| US6869206B2 | 2005-03-22 | |||
| US7889430B2 | 2011-02-15 | |||
| US20110242836A1 | 2011-10-06 |
| CLAIMS 1 . A device for recycling light emitted from an LED light source comprising one or more LEDs mounted on a heatsink, a tapered light pipe having an input end and an output end said input end being smaller than said output end said output end that transforms light output from said input end having a small area, large angle to said output end having a large area, small angle, said tapered light pipe being rectangular or circular in shape, said output end being flat or convex, said one or more LEDs coupled to said input end, a hollow light tunnel having a reflective interior surface, one end coupled to said output end of said light pipe and a second end covered by a mirror directed toward the interior surface of said hollow light tunnel, said mirror having an output aperture about the middle of said mirror, wherein said reflective interior surface guiding light emitted from said one or more LEDs toward said output aperture, where said mirror reflects part of said light emitted from said one or more LEDs that does not exit said output aperture to said hollow light pipe, said tapered light pipe and said light source thereby recycling said light, said recycled light combined with said emitted light thereby increasing the brightness of light emitted through said output aperture. |
Inventor: Kenneth Li
Claims:
To increase brightness of LED, recycling of light back to the LED chip is used. Various methods have been used with different level of cost and difficulty. In this invention, a combination of solid and hollow light pipes is used producing a simple and cost effecti ve mean of recycling.
Figure 1 shows an embodiment of the invention. It includes a light source, which is one or more LEDs, mounted on a heats ink. The output of the light source is coupled to the input end of a tapered light pipe (TLP) having an output with larger area. The cross- section of the TLP can be square, rectangular, circular, or other shapes. The TLP transforms the light from small area, large angle at the input to large area, small angle at the output. The output face of the TLP can be flat, but for more effective transformation, the output surface of the TLP is made convex. The output of the TLP is then coupled to a hollow light pipe with reflective walls inside. The hollow light pipe guides the light toward the output end. At the output end, a mirror is used to reflect part of the light back to die hollow light pipe, TLP and the light source for recycling. The un-reflected light exits through the aperture, which is the output of the system. The output aperture can be square, rectangular, circular, etc. The light reflected back to the light source will be redirected towards the output together with the emitted light, increasing the brightness of the system.
Figure 2a shows an embodiment of the invention applied to a light combining system. The system includes two of more of the recycling light system module (RLSM) as shown in Figure 1. Each RLSM consists of LEDs with color different from the others, As shown in Figure 2a, it consists of 3 RLSMs, one is RED, one is GREEN, and one is BLUE. These are the 3 primary color, when combined, produces color displays. A 4- color system can also be made using 4 RLSMs. for example, with RED, GREEN, BLUE, and YELLOW. The outputs of the 3 RLSMs as shown in Figure 2a are combined using an X-Cube, which consists of two diagonal color filters transmitting and reflecting the appropriate colors such that all 3 colored outputs from the RLSMs are directed to the output with minimum loss. Figure 2b shows the X-Cube indicating the reflective surface and apertures used. The reflective surface and aperture can be made as part of the X- Cube, or can be part of the hollow light pipe with the RLSM.
Figure 3a shows an embodiment with two or more RLSMs assembled together producing combined output with recycling. As shown in Figure 3a, it is a 2 x 2 system consisting of 4- RLSMs with rectangular TLPs, and with, end view as shown in Figure 3b. Four independent hollow light pipes can be used. For practical implementation, a single hollow light pipe is used with a single aperture for the output. A smal l portion of light from one light pipe can be reflected to the neighboring light pipe in the recycling process, which is fine as the light will be recycled by the neighboring LED,
The TLP can be made with, glass or plastic. They can be polished or molded, A.R coatings can be added to the end surfaces. The hollow light pipes can be made with glass, plastic, or metal with reflective coating in the inside.
The output mirror with aperture can be made with glass, plastic, or metal.
The tapered light pipe transforms light from large angle to small angle desi gned to match the requirement of the application.
It can be used for flashlight, search light, or spot light applications where the output from the RLSM can be collimated or have divergence changed with lenses.
As shown inFigure 2a, the combined output from the X-Cube can be used for projectors, entertainment lighting systems, and spot lights.