Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
1999-03-02
2002-02-12
Ham, Seungsook (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250SDIG001, C340S567000
Reexamination Certificate
active
06346705
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to passive infrared motion detectors of the type used in residential outdoor lighting fixtures, for example, to illuminate a walkway or driveway when a person or automobile approaches. The invention is more particularly directed to arrangements for making the motion detector an inconspicuous element of the lighting fixture and to a mirror arrangement suitable for use in such motion detectors.
Lighting devices that automatically turn on a light when a person or a motor vehicle approach have been known for some time. A popular form of such device is responsive to infra-red radiation emitted by a person or motor vehicle as the person or vehicle moves within the field of view of the device. These devices are generally referred to as passive infra-red, or “PIR,” motion detectors and light fixtures.
The first PIR motion detectors were not used with light fixtures at all, but were used in surveillance and alarm systems to monitor for intruders. They were stand-alone devices and tended to be large and bulky in appearance. They employed assemblies of germanium lenses or multi-faceted mirrors or combinations of mirrors and lenses to direct infra-red radiation from an object moving in the field of view to a PIR sensor. The first commercial PIR motion detectors for activating lights were used with utilitarian lighting such as flood lights or other area lighting. Although the motion detectors were bulky and quite conspicuous, that was not seen as a significant drawback in view of their utility in activating the lights in response to intruders. Examples of early PIR motion detectors employing lenses, mirrors and various combinations may be seen in U.S. Pat. Nos. 3,631,434 and 3,958,118 to Schwarz; 3,703,718 to Berman; 3,928,843 to Sprout et al.; 3,988,726 to Reiss et el.; and 4,268,752 to Herwig et al.; and various patents cited therein.
Later, utilitarian PIR light fixtures appeared in which the mirrored optics and germanium lens optics were replaced with plastic Fresnel lens optics. A Fresnel lens of the sort used in connection with motion detectors comprises a thin sheet of flexible plastic material that permits infra-red radiation to pass through it and on which are formed a number of individual Fresnel lens segments or lenslets. See for example U.S. Pat. No. 3,203,306 to Lefferts for an individual Fresnel lens segment formed on such a plastic sheet and U.S. Pat. Nos. 4,321,594 to Galvin or 4,703,171 to Kahl et al. for a segmented Fresnel lens having a plurality of lens segments side-by-side on a plastic sheet. The segmented Fresnel lens was considerably simpler and less expensive to manufacture than the previously employed mirror or germanium lens arrangements and permitted the motion detector units to be made considerably more compact. The flexible plastic sheet on which the lens segments were formed occupied little volume and could be supported with a simple bracket structure at the edges of the sheet with no need for additional brackets to support the individual lens segments. Moreover, the plastic sheet could be bent into a semi-cylindrical or similar curved shape to position the individual lens segments more or less uniformly about the PIR sensor. With the introduction of the flexible plastic segmented Fresnel lens, the earlier lens and mirror arrangements were eschewed in favor of new Fresnel lens arrangements, which were more compact, inexpensive, lightweight, and generally easier to work with.
With the sheetlike segmented Fresnel lens PIR motion detectors could be made considerably less obtrusive, and they were soon added to decorative light fixtures as well as utilitarian ones. At first the motion detector was located in a small housing mounted on an intermediate backplate, which was mounted on a wall over an electrical junction box, and to which the decorative lighting fixture, in turn, was mounted. Such a backplate-mounted motion detector is illustrated in
FIG. 1
of U.S. Pat. No. 5,590,953 Haslam et al. This arrangement became commercially feasible because of the segmented Fresnel lens, which permitted the motion detector housing to be sufficiently compact that it lessened the distraction from the decorative nature of the lighting fixture.
In recent years the trend has been to incorporate the motion detector within the decorative light fixture itself to make it less obtrusive either by concealing it altogether or at least by giving it a decorative appearance so that it does not detract appreciably from the ornamental style of the light fixture. Examples of PIR lighting fixtures that endeavor either to conceal the motion-detecting unit or to embellish it so as to enhance its decorative appearance may be seen in U.S. Pat. Nos. 5,282,118 and 5,434,764 to Lee et al.; 5,575,557 and Des. 382,082 to Huang et al.; 5,590,953 to Haslam et al.; and 5,626,417 to McCavit.
When the motion-detecting unit is incorporated into the body of a decorative light fixture, the flexible plastic lens is generally formed to be a part of a wall of some portion of the fixture and may be tinted to blend in with the fixture body. Thus, in
FIG. 2
of U.S. Pat. No. 5,590,953 the segmented Fresnel lens forms part of a cylindrical wall and in
FIG. 3
of the same patent it is shaped to form a portion of a conical wall. This construction imposes a limitation on the lens optics. In decorative fixtures the nature of the fixture body—its curvature, slope, profile and overall shape—is chosen primarily by aesthetic considerations to give the fixture its decorative appearance and to some extent by manufacturability considerations to maintain a lower cost. The resulting fixture body design, however, then constrains the optics of the segmented Fresnel lens, which will generally follow the contour of a wall of the fixture body. That is, the Fresnel lens may be disposed in a fixture wall at an angle or as part of a curved surface so as to impair the ability of the lens to focus radiation from a desired direction on the sensor. Alternatively, the aesthetic design of the light fixture may be compromised so as to provide a more favorable optical environment for the segmented Fresnel lens. In one attempt to circumvent this problem, U.S. Pat. No. 5,626,417 provides a window in the fixture wall with a plastic cover and places the segmented Fresnel lens in a cylindrical optical disposition inside the fixture behind window.
Meanwhile another trend has been to provide decorative fixtures with longer range and wider fields of view to cover the many arrangements in which the fixture may be mounted by a front door or driveway. This makes greater demand on the optics of the segmented Fresnel lens at the same time that the ornamental requirements on the lighting fixture constrain the feasible optical arrangements of the lens.
SUMMARY OF THE INVENTION
The present invention provides a motion detector assembly for a decorative lighting fixture that conceals or disguises the presence of the motion detector in a decorative element that may be integrated in a natural and graceful manner into the design of the lighting fixture without the limitations on design imposed by the use of the segmented Fresnel lens.
Briefly, a lighting fixture according to the invention includes a motion detector housing that is shaped to have a decorative external appearance harmonious with the style of the lighting fixture and forming an integral part of the lighting fixture. The decorative housing is formed with an aperture for admitting infra-red radiation into the housing from the monitored field of view. An aperture cover extends over the aperture to protect the interior and to conceal the presence of the aperture. The aperture cover is transmissive to infra-red radiation and generally conforms to the shape of the housing in the vicinity of the aperture so as to conceal the presence of the aperture. Mounted within the decorative housing are a passive infra-red (PIR) sensor and a mirror assembly that directs infra-red radiation from the field of view to the sensor. The mirror assembly comprises a p
Lee Wade
Sandell Donald R.
Cordelia Lighting Inc.
Feng Paul Y.
Fulwider Patton Lee & Utecht LLP
Ham Seungsook
Lee Shun
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