Optical: systems and elements – Having significant infrared or ultraviolet property – Multilayer filter or multilayer reflector
Reexamination Certificate
1999-10-01
2001-04-03
Henry, Jon (Department: 2872)
Optical: systems and elements
Having significant infrared or ultraviolet property
Multilayer filter or multilayer reflector
C359S585000, C359S589000, C362S293000, C313S113000
Reexamination Certificate
active
06212004
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention broadly relates to light reflectors having thin film coatings applied thereto for selective reflectance and transmission of different portions of the electromagnetic spectrum radiating from a source. The present invention more particularly relates to such reflectors having plural coatings with different reflectance/transmittance properties across the electromagnetic spectrum, the different coatings being applied to different, pre-selected portions of the reflector, respectively.
Light reflectors come in a variety of types and configurations. A common reflector configuration comprises a generally dome-shaped reflecting portion with a rearwardly extending neck portion wherein a lamp (typically of the incandescent or halogen type) is secured for radiating light forwardly of the reflector body. The reflector body may be made totally reflecting, wherein substantially all of the electromagnetic spectrum emitted by the lamp is reflected forwardly, or it can be of the “cold-mirror” type wherein an optical interference coating is applied to a transparent reflector body (typically glass) with the interference coating acting as a light filter to reflect most of the visible light of the spectrum while transmitting most of the infra-red component thereof (hereinafter “IR”) through the transparent reflector body. Since the IR component is the source of heat in the electromagnetic spectrum, the visible light reflected forward is considered “cold” light which is desirable in many reflector applications.
Certain drawbacks have been identified with cold mirror reflectors, the most prominent of which is the uncontrolled transmission of IR radiation through the reflector body which may cause damage by over-heating of components positioned rearwardly of the reflector body (e.g., transformers and plugs). Another feature of the cold mirror reflector which many find objectionable is the escape of visible light through the end portion of the neck, the internal cavity of which is a difficult area to coat with typical techniques used for applying thin films to reflector bodies (e.g., evaporation and sputtering in a vacuum). The visual attractiveness of the reflector itself and the illumination pattern it creates in the surrounding area are also concerns, as well as being able to coat the reflectors in an efficient, in-line process.
SUMMARY OF THE INVENTION
The present invention addresses the above concerns by providing a cold-mirror reflector with directional control of the IR portion of the electromagnetic spectrum emanating from a lamp positioned inside the reflector body. A significant benefit of the invention is protection from over-heating of components placed rearwardly of the reflector which would otherwise occur due to IR radiation passing through the reflector. Another benefit of the invention is the ability to eliminate the escape of visible light through the neck portion of a reflector body. Additional benefits provided by the present invention include the ability to code different reflector types, as well as improve aesthetics of the reflector including the area which it illuminates.
Directional control of IR radiation of a lamp held in a reflector body is accomplished by the present invention by applying plural coatings having different IR reflectance/transmittance ratios to different, pre-selected areas of the reflector body. More particularly, a first optical interference coating is applied to the inside surface of the main body portion of the reflector. At this stage, the reflector is acting as a prior art cold-mirror reflector which reflects visible light while transmitting IR radiation therethrough. A second coating which is not IR transmissive i.e., it is IR reflecting and/or IR absorbing) is then applied to selected areas of the reflector body. It is noted that IR-reflective materials are preferred over IR-absorbing materials due to concerns of overheating of the reflector substrate which may occur with IR-absorbing materials. The areas coated with the second coating may be on the interior and/or exterior surfaces of the reflector body.
All or part of the neck portion may be coated with the second coating to prevent visible light (as well as most IR light) from escaping therethrough. This may be done with or without applying the second coating to other parts of the reflector body. The application techniques discussed in the Detailed Description section below allow easy application of this second coating to preselected areas of the interior and/or exterior surfaces of the neck portion and/or main body portion of the reflector in an efficient and aesthetically pleasing manner.
Since only the second coating is not IR transmissive, the percentage, direction and area of IR radiation transmitted rearwardly of the reflector body is defined by the dimensional area of the reflector body coated with the second coating. The ratio of IR radiation being transmitted to that being absorbed and/or reflected may therefore be varied by changing the dimensional area covered with the second coating, thereby allowing the specific “heat-management” provided by the reflector to be defined and precisely controlled by the manufacturer as desired. That is to say, the amount of IR radiation transmitted to that being reflected and/or absorbed by the reflector may vary according to need, and a certain amount of IR radiation reflected forward is tolerable in most applications where cold mirrors are used. The present invention addresses this by allowing a wide variety of IR transmittance/reflectance ratios, in addition to allowing control of the area and direction over which the IR radiation is not transmitted (“blocked”) by the reflector.
As mentioned above, the invention also provides means by which different types of reflectors can be coded so as to be readily visually distinguishable by the manufacturer and/or consumer. For example, the second coating of non-IR transmissive material may itself be colored by using a metal nitride, colored metal, metal alloy or other colored material as the second coating, or by applying a colored coating (e.g., metal nitride) as a separate (third) layer in a manner ensuring that the colored coating is readily visually noticeable. As will be explained more particularly below, this third separate layer may be applied on the external or internal surface of the reflector body independently of where the second coating is applied. Hence, this color-coding of the reflector may be used to visually identify and distinguish predetermined reflector characteristics (e.g., brand, beam angle, wattage, etc.) with either a color-identifying machine in a manufacturing line, or the human eye.
The second coating may also be applied in specific patterns on the reflector, e.g., in concentric rings adjacent the neck portion of the reflector, which not only serve to prevent a certain percentage of IR radiation from being transmitted through and behind the reflector body, but also provide a visually pleasing pattern on a surface located rearwardly of the reflector (e.g., a ceiling) by the residual visible radiation which passes through those areas of the reflector body which do not have the second coating applied thereto. The residual light of a cold mirror is typically colored which even further enhances the visual effect on the illuminated surface.
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Naum Robert G.
Stachowiak Grzegorz
Applied Coatings, Inc.
Eugene Stephens & Associates
Henry Jon
LandOfFree
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