Patent Application
20120044675
The present invention relates to elongated LED lamps that may replace elongated fluorescent lamps.
Elongated and typically linear lighting is used in various ways, ranging from lighting products in a vending machine or a refrigerated showcase in a supermarket, to lighting surfaces of a desk or under a cupboard. Traditionally, linear illumination devices include cold cathode tubes, neon tubes and fluorescent tubes. Fluorescent lighting devices have been generally desired by most businesses because of their electrical efficiency and their ability to provide uniform lighting. However, fluorescent tubes require high voltages and power, resulting in power usage of several tens of watts per meter. Such high voltages require additional electrical insulation of the fluorescent tube and extra care while handling the tubes. Repairs of fluorescent lighting devices can be costly for both parts and labor. Moreover, the lifetime of a fluorescent lamp is not very long, resulting in need to frequently change them. Sometimes, in a large supermarket, an employee is dedicated only to replacing burned-out fluorescent lamps in the display cases.
Recently, light emitting diodes (hereinafter “LEDs”), are being used as alternative forms of lighting. LEDs provide many advantages in lighting. They require less energy than a fluorescent lamp. They also do not produce any significant amount of infrared light in their light beam as a byproduct of their operation. However, many available LED lamps suffer from various drawbacks. For instance, when the number of LEDs required to achieve adequate illumination is reached in many available elongated LED lamps, the illumination creates a pixilated look and multi-shadowing on an illuminated surface. Also, the heat that is generated by the LEDs must be conducted away from the LEDs to ensure proper functioning of the LEDs.
Another problem with some prior art LED lighting fixtures is that the fixtures often overheat. It is necessary to provide for the LED lighting fixtures to dissipate its waste heat into the surrounding structure of the lamp. If such provisions are inadequate, the LED will overheat and undergo irreversible damage, which shortens the LED's useful life. In many prior art arrangements, all the heat is concentrated at the site of the LED. It is therefore desirable to reduce the local heat load of each LED to increase its useful life and/or reduce the size of the associated cooling structures.
There is a need for an elongated LED lamp that can replace fluorescent tubes, while avoiding the pixelated look and multi-shadowing on an illuminated surface present in some LED lamps.
In one preferred example, an elongated LED lamp, comprises: an elongated side-light distribution arrangement comprising at least three sequentially arranged side-light distribution portions, a plurality of LED light sources respectively associated with said portions by having one LED light source primarily illuminating a respective portion, via a light coupling means, when the central axes of light emission from each of the LED light sources are not aligned with each other and by having one or a spaced pair of LED light sources, each located at an end of the portion, primarily illuminating a respective portion, via a light coupling means, when the associated LED light sources have central axes of light transmission aligned with each other; and each respective light coupling means transforms at least 15% of received light into an appropriate angular distribution needed for total internal reflection within an associated side-light distribution portion.
Beneficially, the foregoing elongated LED lamp can replace fluorescent tubes, while avoiding the pixelated look and multi-shadowing on an illuminated surface present in some LED lamps.
Other advantages and features of the invention will become apparent from reading the detailed description of the invention below in conjunction with the drawing figures, in which:
The examples and drawings provided in the detailed description are merely examples, which should not be used to limit the scope of the claims in any claim construction or interpretation.
In the figures, various dimensions have been enlarged for clarity of explanation, such as a typical diameter of an LED lamp compared to its length.
A LED light source is defined herein as one or more LEDs provided with a single pair of power leads and, typically also, a single lens for conditioning light output, and includes a printed-circuit board on which an LED or LEDs are mounted, which may have a metal core to assist in heat removal.
Prior art
In
In one example, the central axis of light emission from a respective light coupling means that receives light from a respective LED light source, is oriented transverse to a central path of total internal reflection (TIR) light propagation through an associated side-light distribution portion, such as in
In one example, a respective light-extraction means is positioned in a direction opposite to an associated LED light source, as shown in
The central path of light propagation of a respective side-light distribution portion is not shown in the respective FIGS. but would be readily apparent to a person of ordinary skill.
Compared to an LED lamp having only one LED at one end or LEDs at both ends, the LED lamps 300 and 400 have LED light sources 318 whose area is reduced proportionately. Based on the law of Etendue, as the area of the light source is reduced, the diameter of the light coupling means and the side-light distribution arrangement becomes proportionately reduced to maintain the angular distribution of light propagating through the system.
In the LED lamp of
The LED lamp 300 of
The elongated LED lamp 400 of
Advantageously, the amount of materials and the weight of the LED lamps 300 and 400 of
In between each side-light distribution portion 314 of the embodiments of
A respective light coupling means 602 couples received light from each LED light source 601, which is supported on a heat sink 603. Each side-light distribution portion 609 of the side-light distribution arrangement 610 is primary illuminated by a respective pair of LED light source 601 and light coupling means 602 connected thereto via a respective connecting portion 604. Each side-light distribution portion 609 can receive light from an associated LED light source 601 directly or by TIR light propagation within a light coupling means 602 and associated connecting portion 604. The connecting portions 604 may not maintain the angular distribution of light received from the light coupling means 602.
Light is extracted from each of the side-light distribution portions 609 by respective light-extraction means 605. Residual light that is not extracted from the side-light distribution arrangement 610 on a first pass through the arrangement can be reflected back into the arrangement by mirrors 607, which are supported by support structures 608.
Each LED light source 601 is connected by wires to a power-regulating circuit 606, with such wires shown diagrammatically in
The connecting portion 604 is constructed to keep the light internal to itself through the use of TIR. The connecting portions 604 are in optical contact with the side-light distribution portions 609 so no light is lost as light moves from the connecting portion 604 to the side-light distribution portion 609. “Optical contact” occurs when two surfaces are in optical contact, and light traveling from one surface to the next surface does not experience a reflection as it leaves one surface and enters the next surface. Either the medium through which the light passes is the same or has substantially the same refractive index. Ideally, the connecting portion 604 is constructed from the same material as the light coupling means 602 and the side-light distribution portion 609.
In the embodiment of
In yet another embodiment of the claimed invention, distributing the total LED light sources along the length of a side-light distribution arrangement can provide thermal benefits since there are separate sites over which to distribute the fixed thermal load.
In
As best shown in
Each LED light source 703 may be mounted to a heat sink 704 for dissipating heat from the light source. The LED light source 703, in another instance, can be optionally connected to a different mounting structure.
The light from the LED light sources 703 is guided towards the light-extraction means 702 by the inherent light coupling means mentioned above. In this example shown in
The light-extraction means 702 distributes the illumination from the LED light sources 703 so as to be able to create an evenly distributed illumination. An exemplary spacing of the light-extraction means 702 can be best seen in
Optionally, a non-specular reflector 707 may be placed over the LED lamp 700 of
The elongated LED lamp 700 of
In LED light source 800 of
In this embodiment, the reflective surfaces 802 causes a large amount of the light emitted by the LED light sources 801 to be sent sideways in the side-light distribution arrangement 811 below the angle required for TIR propagation along the length of the arrangement 811. Similar to LED lamp 700 of
The protrusions 907 could be, but are not necessarily made to closely replicate non-imaging optical coupling means such as non-imaging light-coupling means described in detail below. The protrusions 907 also provide a level of collecting and directing of the light reflected or scattered from the light-extraction means 902 in a directed manner, as indicated by arrows 905. The protrusions 907 may run continuously along the length of the side-light distribution portion. Alternatively, the protrusions 907 may, as indicated by phantom-line areas 910 that would be absent and cause the protrusions to constitute a plurality of discrete protrusions along the length of the side-light distribution arrangement 901.
In one example, the protrusions 902 extend continuously along a majority of the length of the side-light distribution arrangement 901. In a more preferred example, the protrusions extend continuously along at least 80 percent of the length of the side-light distribution arrangement 901. Alternatively, the protrusions can extend along the length of the side-distribution arrangement in discrete portions.
As shown in
In
The elongated LED lamp 900 of
In LED lamps 1000 and 1100, the light from light source 1003, at least partially received within a cavity as in prior embodiments, is directed by the light-extraction means 1002 (
In
In
The elongated LED lamp includes mirrors 1005, end plates 1010, a power-regulating circuit 1007 and electrode pins 1012.
A “non-imaging” light coupling means, as used herein, tolerates minor manufacturing imperfections while retaining substantially the full functionality of an ideally formed non-imaging coupling means.
Normally, the light coupling means only transforms light from the light source into the proper angular distribution required by the side-light distribution arrangement. The side-light distribution arrangement normally only transports light down its length (via total internal reflection), delivering the light to the end opposite the light source. Also, the light-extraction means only extracts light transverse to the length of the side-light distribution arrangement; it does not collect light from a light source or perform any angular transformation of the light.
Regarding the light coupling means, its interiorly-directed reflective surface is normally the primary device for receiving light from a light source. It then transmits that light toward a light-receiving portion of a side-light distribution arrangement, which is discussed in later paragraphs. This reflective surface is typically specular if the light coupling means is hollow, or of the TIR-type if the light coupling means is solid, where TIR means total internal reflection.
The rules of non-imaging optics govern the configuration of the light coupling means at least approximately. As known in the art, the rules of non-imaging optics are concerned with the optimal transfer of light radiation between a source and a target. In contrast to traditional imaging optics, non-imaging techniques do not attempt to form an image of the source; instead, an optimized optical system for radiative transfer from a source to a target is desired.
The two design problems that non-imaging optics solves better than imaging optics are as follows, First, (1) concentration—maximizing the amount of energy applied to the target (as in solar power, for instance, “collecting radiation emitted by high-energy particle collisions using the fewest number of photomultiplier tubes”). Second, (2) illumination—controlling the distribution of light, typically so it is “evenly” spread over some areas and completely blocked from other areas (as in automotive headlamps, LCD backlights, etc.).
Typical variables to be optimized at the target include the total radiant flux, the angular distribution of optical radiation, and the spatial distribution of optical radiation. These variables on the target side of the optical system often must be optimized while simultaneously considering the collection efficiency of the optical system at the source.
Typically, a light coupling means at least approximately governed by the rules of non-imaging optics has a profile that changes from the inlet end toward the outlet end to condition the angular distribution of light provided to a rod-shaped side-light distribution arrangement. That is, as light propagates through the light coupling means, its angular distribution changes. In addition, the interior surface of a solid light coupling means may be configured to aid in the conditioning of light provided to a rod-shaped light pipe.
This change in the angular distribution of light conditions the light for distribution by the side-light distribution arrangement. Three examples are as follows. First, (1) the light may be conditioned to reduce the angular distribution of light to be significantly below the numerical aperture or acceptance angle of a side-light distribution arrangement so that it propagates along the entire length of the side-light distribution arrangement and is distributed out the opposite end.
In a second example (2), the angular distribution of light leaving the light coupling means can be higher but closer, or even beyond, the numerical aperture (NA) of the side-light distribution arrangement. In this case, the light leaving the light coupling means with a higher angular distribution will see a greater number of interactions with the sides of the side-light distribution arrangement, thereby increasing the opportunity for distribution out the side of the side-light distribution arrangement over a shorter distance.
In a third example (3), the profile of the light coupling means changes so that the light leaving the light coupling means is not only conditioned to cause the angular distribution to be within an intended NA, but also is conditioned to cause the light to be uniformly distributed among a greater number of angles. In this case, at least approximately governed by the rules of non-imaging optics, the profile of the light coupling means will typically grow in size and then decrease as it approaches and reaches the side-light distribution arrangement. Because the resulting light is conditioned so that light is present at a multitude of angles, light with higher angles will have more interactions with the side of the side-light distribution arrangement and will be distributed over shorter distances, and light with lower angles will see fewer interactions so will be distributed over longer distances. The result may be a more uniform distribution out of the side-light distribution arrangement along its entirety.
With respect to the light coupling means, the coupling means can have an increasing cross-sectional area from a light coupling inlet end and a light coupling outlet end. The change in area for the light coupling means can be of a non-monotonic function, for example, a compound parabolic curve. The increase in cross-sectional area of the light coupler may follow the pattern disclosed in U.S. Pat. No. 6,219,480, the disclosure of which is incorporated herein by reference. More specifically, the cross-sectional area of the light coupling means increases in a continuous manner, where “continuous” means that the cross section at a point along an axial length transitions to a next point without any substantial discontinuities.
Alternatively, the cross-sectional area of the light coupling means can increase and decrease in a continuous manner, where “continuous” means that the cross section at a point along an axial length transitions to a next point without any substantial discontinuities.
In another example, the cross-sectional area of the light coupling means increases or decreases in a continuous manner, where “continuous” means that the cross section at a point along an axial length transitions to a next point without any substantial discontinuities. For example, a central path of light propagation occurs from an inlet end to an outlet end, where a cross-section increases from a first cross-sectional area to a maximum cross-sectional area and then decreases in cross-section to a final cross-sectional area larger than the first cross-sectional area.
A side-light distribution arrangement as used herein preferably comprises an elongated rod. By “elongated” it is meant being long in relation to width or diameter, for instance, where the “long” dimension can be both along a straight path or a curved path.
One end of the side-light distribution arrangement receives light from an associated light coupling means. The elongated rod has an elongated sidewall and light-extraction means along at least part of the elongated sidewall for extracting light through the sidewall and distributing said light to a target area. At least, the part of the side-light distribution arrangement having light-extraction means is preferably solid, although there may exist in the arrangement small voids caused by manufacturing processes, for instance, voids that have insubstantial impact on the side-light light-extraction and distribution properties of the side-light distribution arrangement.
A side-light distribution arrangement as used herein has a cross section along a main axis of light propagation through the pipe that is more round than flat. For example, the minimum cross-sectional dimension is preferably more than 50% of the maximum cross-sectional dimension. In a preferred embodiment, the cross-section of the side-light distribution arrangement is substantially circular.
Preferably, a side-light distribution arrangement is rigid, by which is meant that at 20 degrees Celsius the arrangement has a self-supporting shape such that the light pipe returns to its original or approximately original (e.g., linear or curved) shape after being bent along a main path of light propagation through the light pipe. However, if the side-light distribution arrangement is flexible, it is meant that the side-light distribution arrangement has a shape that will be bent to a shape that has a curvature when being bent along its longitudinal axis.
The preferred embodiment of the side-light distribution arrangement is one that includes a constant cross-sectional area, within manufacturing tolerances known to a person of ordinary skill. Such constant cross-sectional area is within a + or −5% deviation. In one example, a useful embodiment of the system may include a monotonically increasing cross-sectional area of the side-light distribution arrangement. The increasing cross-sectional area reduces the angular distribution of light passing through the light coupling means, so as to enable the light rays to propagate at higher angles while maintaining total internal reflection.
The decreasing cross-sectional area aids in extraction of light from the sides of the side-light distribution arrangement, because the angles of light effectively become steeper with respect to the covering surface of the side-light distribution arrangement.
The side-light distribution arrangement may have a nearly constant cross-sectional area. The term “nearly constant” cross-sectional area indicates a generally constant cross-sectional area with + or −5% deviation. The cross-sectional area of the side-light distribution arrangement may become “gradually larger” starting from the inlet end and moving towards the second end of the side-light distribution arrangement. Alternatively, the cross-sectional area of the side-light distribution arrangement may become “gradually smaller” starting from the inlet end and moving towards the second end of the side-light distribution arrangement. When defining “gradually larger” or “gradually smaller,” the cross-sectional area increases or decreases in a continuous manner, where “continuous” means that the cross section at a point along an axial length transitions to a next point without any substantial discontinuities, as disclosed in the foregoing '480 patent. The change in cross-sectional area is of a monotonic function.
Now specific examples of the light-extraction means will be discussed. Light-extraction means may be of various types whose selection will be routine to those of ordinary skill in the art. For instance, three types of light-scattering means are disclosed in U.S. Pat. No. 7,163,326, entitled “Efficient Side-light Luminaire with Directional Side-Light-Extraction,” assigned to Energy Focus, Inc. of Solon, Ohio. In brief, these three types are (1) discontinuities on the surface of a side-light distribution arrangement, (2) a layer of paint on the surface of a side-light distribution arrangement, and (3) a vinyl sticker applied to the surface of a side-light distribution arrangement.
In more detail, (1) discontinuities on the surface of a side-light distribution arrangement may be formed, for instance, by creating a textured pattern on the side-light distribution arrangement surface by molding, by roughening the side-light distribution arrangement surface with chemical etchant, or by making one or more notches in the side of a side-light distribution arrangement.
In another example, the light-extraction means may comprise a layer of paint exhibiting Lambertian-scattering and having a binder with a refractive index about the same as, or greater than that of, the core. Suitable light-extraction particles are added to the paint, such as titanium dioxide or many other materials as will be apparent to those of ordinary skill in the art. Preferably, the paint is an organic solvent-based paint.
In yet another example, the light-extraction means may comprise vinyl sticker material in a desired shape applied to the surface of the side-light distribution arrangement. Appropriate vinyl stickers have been supplied by Avery Graphics, a division of Avery Dennison of Pasadena, Calif. The film is an adhesive white vinyl film of 0.146 mm, typically used for backlit signs.
In another example, the light-extraction means may be continuous, intermittent, or both, along the length of a side-light distribution arrangement, for instance. An intermittent pattern is shown in the above-mentioned U.S. Pat. No. 7,163,326 in
Additionally, the foregoing light-extraction patterns may be of the specular type, scattering type, or a combination of both. Generally, a scattering extractor pattern for light on an elongated side-light distribution arrangement tends to provide light onto a target area, along the length of the side-light distribution arrangement, with a moderate degree of directional control over the light in the length direction. In the direction orthogonal to the length, the scattering extractor pattern density and the cross sectional shape of the elongated side-light distribution arrangement provide a smooth target distribution that is free of localized spatial structure but still provides good directional control. Scattering extractor patterns are relatively insensitive to fabrication errors.
In contrast, as used herein, a specular extraction pattern can provide light along the length of a side-light distribution arrangement with more localized control than can a scattering extraction pattern.
The following is a list of reference numerals and associated parts as used in this specification and drawings:
While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims.
This application claims priority to U.S. Provisional Patent Application No. 61/375,937 filed on Aug. 23, 2010, the disclosure of which is fully incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61375937 | Aug 2010 | US |
