1. Field of the Invention
The invention relates to a LED lamp and color mixing optics to produce a uniform intensity distribution and a uniform color output throughout the beam pattern of the light beam produced by a multi-color LED light source for use in LED lamps.
2. Description of Relevant Art
Color LED lamps should have an even intensity and color distribution over a broad range of radiation angles. As there is no single point LED source available, the radiation of multiple LED sources must be combined to form a multi-color light source. These multiple LED sources are placed offset to each other, so there is no common focal point. To obtain an even color distribution, color mixing is required.
Conventional color mixing uses light guides which typically are large and inefficient. The rule of thumb for a light guide is that it should be about 10 times longer than the dimensions of the multi-color light source. A typical 90 Watt halogen lamp produces about 1200 lumens. An array of many large LEDs is necessary to produce such output light. Such 1200 lumen output arrays may be about 5-6 mm in diameter. If such a light source comprises multi-color LEDs, a 50-60 mm light guide would be needed to properly mix the colors. Considering that the beam needs to be shaped after color mixing, the dimensions needed for a light guide become too large to fit into conventional lamp housings.
U.S. Pat. No. 8,529,102 discloses a reflector system for a multi-color LED lamp providing color mixing. The system uses two reflective surfaces to redirect the light before it is emitted.
A lens the system with multiple curved surfaces for a multi-color LED lamp is disclosed in the U.S. Pat. No. 8,733,981. It is based on a total inner reflection (TIR) lens system which has some similarity to a Fresnel lens.
The embodiments are based on the object of making a color mixing optic for color LED lamps which produces uniform intensity and color throughout the entire light beam while the outer dimensions are such small that the optics fit into conventional lamp housings. Furthermore, the optic should be simple, robust as well as easy and cost-effective to manufacture. Another embodiment is based on the object of making a color LED lamp comprising the color mixing optic.
In an embodiment, an optic system comprises an outer reflector which preferably has a concave surface. This reflector preferably has a paraboloidal surface of revolution and is centered around a center axis. Preferably, it has a reflector focal point.
A total inner reflection (TIR) lens is provided, which has an outer contour with a paraboloidal surface of revolution and with a TIR lens focal point. Preferably, the reflector focal point is in close proximity to the TIR lens focal point most preferably at the TIR lens focal point.
Preferably, the color mixing optic is rotationally symmetrical about a center axis. Therefore it is preferred to align the outer reflector and the TIR lens with the center axis.
Furthermore, the TIR lens preferably has a concave light entrance surface by which it receives light from the at least one LED. Preferably, the light entrance surface has a spherical shape.
Preferably, the TIR lens is arranged within the outer reflector. Most preferably it is held within the outer reflector.
Preferably, the TIR lens is held by a cover, which preferably covers the outer reflector, preventing dust and debris from entering into the lamp. It is preferred, if the cover and the TIR lens are made of one piece and therefore, the TIR lens is part of the cover.
Preferably, the LED assembly or the center of the LED assembly is located close to and most preferably at the focal point.
In an embodiment, an LED lamp comprises LEDs and an optic system as mentioned before. The optic system comprises a housing enclosing the outer reflector or being part thereof, a total inner reflection (TIR) lens, and a cover.
A LED assembly holds at least one LED, preferably a plurality of LEDs. It may be based on a printed circuit board and it preferably has a heat sink. It may be part of the base. The LED assembly preferably is positioned at or close to the focal point of the paraboloidal outer reflector. Most preferably a LED surface plane is positioned at or close to the focal point of the paraboloidal outer reflector. The LED surface plane is a plane defined by the radiating surfaces of the individual LEDs of the LED assembly. The LED assembly may be covered by a protective cover, which preferably forms a LED lens. Preferably, the LED lens has a spherical shape. It is preferred to align the (optical) center of the LED assembly, the outer reflector and the TIR lens with the center axis. The LED assembly may be held by a base to the housing.
The optics still works with comparatively large LED arrays, where individual LEDs are spaced apart in the range of tenths of millimeters to millimeters. Furthermore, the optics works with a plurality of colors and is therefore usable for multicolor LEDs, as the color mixing properties are largely independent of the wavelength.
In this embodiment, for the first time an LED lamp can be built which provides accurate white light along the black body curve along with saturated colors. This lamp may be implemented in a PAR form factor, preferably a PAR that provides uniform color throughout the standard 10, 25, 40 degree beam angles.
It is essential for these embodiments, that almost all the light radiated by the LEDs is only reflected by either the outer reflector or by the TIR lens, thus avoiding any refraction which is wavelength dependent and therefore causes deviation in the color distribution.
Another embodiment relates to an LED lamp comprising a housing, a socket, a power supply, and/or driver, an LED assembly and the optics comprising an outer reflector, a TIR lens, and preferably a cover.
A further embodiment relates to a method for generating a mixed beam of light. First, light of multiple wavelengths is generated by a LED assembly comprising a plurality of LEDs. After generating the light, deflecting the light in two portions take place. A first portion of the light is deflected by an outer reflector having a paraboloidal surface of revolution centered around a center axis and defining a reflector focal point. A second portion of the light is deflected by a total inner reflection (TIR) lens having an outer contour with a paraboloidal surface of revolution centered around the center axis and defining a TIR lens focal point. The reflector focal point is in close proximity to the TIR lens focal point. This method may be combined with any of the embodiments disclosed herein.
In the following, the invention will be described by way of example, without limitation of the general inventive concept, on examples of embodiment and with reference to the drawings.
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.
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An LED assembly 60 is attached to the outer reflector and/or the housing, preferably by a base 22, although it may be held independently thereof. The LED assembly comprises a plurality of LEDs 61, 62. It preferably has a cover 50 which may be a protective cover and/or forming a LED lens. The LED assembly 60 may be mounted to a base which may be a printed circuit board and/or a heat sink. Preferably, the LED assembly is arranged on a common center axis 11 which preferably is the center axis of the outer reflector 21 and of the TIR lens 40. Furthermore, it is preferred that the LED assembly is arranged at a common focal point of the outer reflector 21 and the TIR lens 40, as will be shown later.
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To obtain a uniform color distribution, the rays originating by the individual LEDs 61, 62 should be projected to approximately the same point. In the embodiment of
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Finally, there are third set of rays 73 which propagate from LEDs 61, 62 via LED lens 50 through light entrance surface 43 and which are not reflected by the outer reflector 21 or the TIR lens 40. As these rays propagate through the planar light exit surface 42 and/or the cover 30 at some angle other than 90°, there is refraction, leading to a deviation of the light rays with respect to the center axis 11. However, this part of the light is only a small part of the total radiation of the LEDs. It is further distributed over a wide angle and mixes with the other light of the rays 71 and 72. Therefore, it has a negligible effect on color distribution.
The color mixing optic 10 shown in
Generally speaking, the depth (dTIR) of the TIR lens 40 and the radius (rTIR) of the upper aperture of the TIR lens 40 are dependent on the depth (d) of the outer reflector 21 and the radii (ru, rb) of the upper and lower apertures of the outer reflector 21. According to one embodiment, the radius (rTIR) of the upper aperture of the TIR lens 40 is made to be substantially equal to the radius (rb) of the lower aperture of the outer reflector 21. This allows the TIR lens 40 to capture and collimate as much of the emitted light as possible without interfering with the first set of rays 71 (see,
The depth (dTIR) of the TIR lens 40 is preferably designed so that no light rays can escape between the outer contour 41 of the TIR lens 40 and the outer reflector 21 without being collimated by the outer reflector 21. In other words, the depth (dTIR) of the TIR lens 40 should be configured to intercept all light rays, which are emitted by the LED assembly 60 above a line extending between source point (0,0) and an edge point (ru, h) of the outer reflector 21. In the exemplary embodiment shown in
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It will be appreciated to those skilled in the art having the benefit of this disclosure that this invention is believed to provide optics for LED lighting with color mixing properties. Specifically, color mixing optics are disclosed herein for producing a uniform intensity distribution and a uniform color distribution throughout the entire beam pattern produced by a multi-color LED light source. Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.