1. Field of the Invention
This invention relates to electromagnetic irradiation of surfaces and, in particular, this invention relates to LED-emitted electromagnetic irradiation of surfaces from reflectors and to LED-emitted electromagnetic irradiation of surfaces from irregularly or non-linearly patterned emitting surfaces.
2. Background
Typically, parabolic or elliptical reflectors are used for directing radiation using reflective optics to achieve uniform or focused irradiance, respectively. Obviously, other irradiance patterns can be generated using more complex reflector geometries. However, the quality of focus or collimating irradiance is largely dependent on how well irradiance is concentrated at the focal point of the optic. The foregoing problem is illustrated in
Where the radiation source is linear, such as a fluorescent lamp, the reflector may be an elliptical trough or a portion of an ellipse. The optical center of the linear lamp is placed along a focal line of the trough reflector. For example, if the arc source 102 of
Additionally, previous LED designs have focused on linear arrangements of chips, whereby the chips are arranged as close together to eliminate “emitting gaps.”
An assembly is provided by this invention, the assembly having a reflector and a
UV array. The UV array may have a plurality of UV emitting LEDs arranged spatially in a pattern such that a linear fill factor characterizing such a pattern is at least 80% along a focusing direction and/or at least 20% along a direction normal, or otherwise transverse, to the focusing direction. The reflector may be a trough reflector and may collimate or focus the UV radiation.
There is also provided a method of manufacturing the foregoing UV array.
There is further provided a method of irradiating a surface with the foregoing array.
Due to the advent of high-power LED sources, various configurations can be used to achieve efficient curing profiles while enhancing manufacturing ease and improving reliability of performance. An assembly is accordingly provided by this invention having a reflector and a UV array. The UV array may have a plurality of UV-emitting LEDs arranged spatially non-linearly or irregularly.
There is also provided a method of manufacturing the foregoing UV array.
There is yet further provided a method of irradiating a surface with the foregoing array.
The embodiments of this invention maximize the ease of being manufactured, while maintaining a substantially uniform curing profile along the length of the profile.
This arrangement can be repeated in any length as necessary for application.
It is understood that the above-described figures are only illustrative of the present invention and are not contemplated to limit the scope thereof.
Each of the additional features and methods disclosed herein may be utilized separately or in conjunction with other features and methods to provide improved devices of this invention and methods for making and using the same. Representative examples of the teachings of the present invention, which examples utilize many of these additional features and methods in conjunction, will now be described in detail with reference to the drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Therefore, specific combinations of features and methods disclosed in the following detailed description may not be necessary to practice the invention in the broadest sense and are instead taught merely to particularly describe representative and embodiments of the invention.
In the case of a trough reflector with light emitting diodes (LEDs) as shown in
One remedy to the problem illustrated above (deteriorating focus or collimation when a plurality of LEDs is used) is to maximize the fill factor (packing density) of the LED chips or lamps along the primary axis of the ellipse f1 as will more fully be explained herein. The best case scenario would be a fill factor of 100% or a large, single LED chip.
Optimal use of elliptical trough reflectors for imaging a primary (source) focal line at a secondary (image) focal line is best accomplished by concentrating the emission along the primary focal line. This is illustrated in
A single LED chip can produce only so much emission from a given amount of electrical energy. Therefore, if a given application requires higher irradiance than can be obtained from a single LED chip and optimized optics, one typically increases the number of LED chips, arranging the LEDs in an array. One example of an LED array is depicted in
Regarding the LED 120 of
Referring to
Focus of a reflective trough 160 is not affected by the linear fill factor along the focal line L1 of
Clearly, LEDs can be used with reflective optics to create various irradiance profiles at a distance. Plus, the linear fill factor (packing density) of LEDs along a focal direction, such as h, has a significant influence on the focusing ability (and irradiance in W/mm2) of elliptical trough reflectors. However, the linear fill factor along the focal line of the reflector primarily affects the uniformity of the irradiance along L2. As stated previously, analogous rationale can be made for collimating capability of parabolic trough reflectors or the imaging capability of curved trough reflectors of other geometries.
It is usually desirable to control both the irradiance magnitude and irradiance profile (distribution) at the image plane of the trough reflecting optic. For applications where the emission source is an array of packaged LED chips, one desires the following:
1. In the focusing direction of a curved reflector, an LED array with a linear fill factor exceeding 80%, 90%, or any range subsumed therein, may be considered a characteristic of one embodiment of this invention. The linear fill factor may, accordingly, have a value between 80% and 100%, 100% possible only with a single
LED chip. Linear fill factors greater than 80% are practical only for a single LED chip or for no more than two LED chips separated by a small gap such that the linear fill factor is greater than 80%. Accordingly, the linear fill factor is critical to achieving maximum irradiance around a focal line of a trough reflector.
2. Along a focal line of a curved reflector, in order to provide uniformity at the image plane, one desires a linear fill factor greater than 20%, 30%, 40%, 50%, or any range subsumed therein. Linear fill factors along the focal line of the curved reflector may be increased to increase either the total irradiance at the image plane or increase the irradiance uniformity at the image plane, or both. Some examples of chip packing possibilities are shown in, but are not limited to, the exemplary arrays depicted in
In
Regarding the array shown in
Deviation from the guidelines described in 1 and 2, above, will reduce the uniformity and irradiance intensity at the image produced by emissions from LED chips as directed by a trough reflector of this invention. By chip, is meant a packaged semiconductor element, the LED array of one embodiment including a plurality of LED chips, a receptacle to fix the LED chips in place and dissipate heat, electrical connections to the LED chips, and optionally a lens or window overlaying the LED chips. A focal line of a reflective trough of this invention may be positioned approximately at the surface of such semiconductor chip.
The concepts described herein may be applied to any LED source, such as an LED-emitting UV, visible, or IR wavelengths. In fact, an emission wavelength (or emission peak wavelength) can be different for each LED of a linear array of this invention if so desired so long as the LFL for any one wavelength is more than 20%, thereby limiting the number of wavelengths or peak wavelengths in a given array (depending on the chip configuration) to six or less typically. For example, using the chip arrangements of
Many UV-curing applications have been optimized for high power mercury discharge lamps, where a linear lamp is positioned along the focal line of a trough reflector, which may be elliptical, parabolic, or another compound shape. The use of LEDs with high linear fill factors as described herein may enable LEDs to concentrate light in much the same way as linear mercury lamps presently accomplish. Less dense arrays of smaller LED chips cannot be as concentrated and, thus, are much less effective for curing applications where high irradiance and/or uniform flood curing is required. In the case of flood curing, large areas of small chip arrays can be used. However, these large areas of small chip arrays are effective only if the source is sufficiently close to the surface to be cured. Otherwise, there is a loss of intensity due to the inverse square law. Concentrated large linear arrays can be employed with parabolic collimating troughs to provide high irradiance at higher separations of the source and the surface to be cured. As described herein, UV LEDs emitting differing wavelengths could be combined as needed for complex formulation curing.
Combinations of focusing optics with visible LEDs with packing densities, such as those described herein, may be used to create a variety of useful irradiance patterns. By carefully controlling the linear fill factor in the focusing direction and along the focal line of a suitably designed trough reflector, irradiance patterns useful for walkway lighting, street lighting, and other applications, can be realized. Moreover, there are advantages to using this type of optical design as compared to large arrays of smaller LEDs. For some embodiments of this invention, these advantages include 1) reduced light pollution by achieving better control of how light is imaged by the reflective optic; and 2) improved optical efficiency with a single simple fixture optic with low glare because LEDs are aimed at the reflector, not at the image plane.
One aspect of this invention is that the use of a very high LED packing density, as measured by a high linear fill factor in the focal direction of a curved trough reflector leads to significant advantages for illumination or irradiation system design. This design can be improved upon even more if the LED source possesses an asymmetric irradiation pattern as shown in
Thus far, trough reflectors depicted and discussed were simple, having smooth surfaces and without features which would produce additional optical effects other than specular reflection. However, additional performance improvements can be achieved by incorporating certain diffractive surface structures into the reflective surface. These structures may include, but not be limited to, 1) diffraction gratings, 2) corrugation, or 3) either of the above, where the period and amplitude of the grating or corrugation vary along the focal line of the trough reflector. The foregoing surface features may be oriented with a long axis perpendicular to the focal line of the trough reflector. If so, the focusing or collimating effect of the reflector would be largely unaffected. However, the emission incident on the reflector would be spread more widely along the focal line. The image shown in
Thus far, the overall design of the optical system has been essentially linear in nature, wherein the focal line is a straight line. It is also possible to preserve key aspects of the invention when the focal line (or non-linear focus) is not straight, but is curved or bent in a direction so as to create a required or desired lighting or irradiation pattern. A curved focal line might be employed to create a spot in irradiance pattern (the focal line curves in on itself to form a circle and the curvature is in a plane coplanar to the image plane). The curvature may also be in a plane perpendicular to the image plane, which is potentially useful when two trough reflectors of finite lengths are used for an illumination application, for example, along a sidewalk. Along sidewalks, it is desirable to avoid dark spaces between illuminated areas provided by each fixture. In such a case, the focal line of each fixture might be curved in a plane perpendicular to the sidewalk to increase the light intensity in the gap between fixtures.
More complex shapes are possible when the elliptical or parabolic shape of a trough reflector is varied along a constant focal line. As an example, one might consider the need to irradiate a non-planar surface with a fixed irradiance. In such case, it would be possible to gradually vary the eccentricity of an elliptical trough reflector along a focal line (curved or otherwise) to attain such a goal.
By way of further explanation and referring to
Because numerous modifications of this invention may be made without departing from the spirit thereof, the scope of the invention is not to be limited to the embodiments illustrated and described. Rather, the scope of the invention is to be determined by the appended claims and their equivalents.
This application claims priority under 35 U.S.C. §119 (e) to, and hereby incorporates by reference, U.S. Provisional Application No. 62/027,705, filed Jul. 22, 2014, and is a continuation-in-part of, and hereby incorporates by reference, U.S. Patent Application No. 12/660,405, filed Feb. 25, 2010, which claims priority under 35 U.S.C. §119 (e) to, and hereby incorporates by reference, U.S. Provisional Application No. 61/208,485, filed Feb. 25, 2009; and which is also a continuation-in-part of U.S. patent application Ser. No. 12/704,104, filed Feb. 11, 2010, hereby incorporated by reference, which, in turn, claims priority under 35 U.S.C. §119 (e) to, and hereby incorporates by reference, U.S. Provisional Application No. 61/152,416, filed Feb. 13, 2009.
Number | Date | Country | |
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62027705 | Jul 2014 | US | |
61208485 | Feb 2009 | US | |
61152416 | Feb 2009 | US |
Number | Date | Country | |
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Parent | 12660405 | Feb 2010 | US |
Child | 14478166 | US | |
Parent | 12704104 | Feb 2010 | US |
Child | 12660405 | US |