PIR motion detector for a decorative lantern
A small-sized hidden motion detector that can be incorporated in a decorative manner into a decorative lantern. The motion detector can be incorporated into lighting fixture designs not previously amenable to a hidden motion detector in the body of the lighting fixture. A small decorative motion detector housing is provided defining a compact interior region with a PIR sensor mounted inside and providing a sufficient optical pathway for a practical motion detector of wide angular field of view that can nevertheless fit inside commonly found small-sized decorative lantern elements. In one embodiment the motion detector is hidden in a small generally cylindrical decorative element of the sort that is found in a number of traditional decorative lantern designs and that has not previously been amenable to a hidden motion detector. Another embodiment includes a mechanism for mechanically adjusting the range and responsiveness of the motion detector notwithstanding the small size of the space available for housing the detector.
1. A decorative lighting fixture activated by an infra-red motion detector for monitoring motion in a monitored region, wherein the motion detector includes a motion detector housing having a decorative external appearance and disposed to form an integral part of the lighting fixture, an infra-red sensor disposed within the housing, and a segmented Fresnel lens member for directing infra-red radiation from the monitored region to the infra-red sensor, wherein the lighting fixture is characterized in that:
said motion detector housing and said segmented Fresnel lens member define a compact interior region having a characteristic transverse dimension of at most 28 mm;
said infra-red sensor is mounted in said compact interior region; and
said lens member is structured and disposed in said motion detector housing to direct infra-red radiation to said sensor from a plurality of zones in said monitored region, said plurality of zones having a horizontal angular field of view of at least 150 degrees.
2. The apparatus of claim 1 wherein said motion detector housing and said segmented Fresnel lens member define a generally cylindrical portion and said characteristic transverse dimension is an inside diameter of said generally cylindrical portion.
3. The apparatus of claim 2 wherein said sensor has an entrance window for infra-red radiation and said sensor is disposed such that said entrance window is positioned at the transverse center of said generally cylindrical portion.
4. The apparatus of claim 3 wherein said lens member is structured and disposed to define at least two vertical levels of vision.
5. The apparatus of claim 4 wherein said lens member is structured and disposed to define at least three vertical levels of vision.
6. The apparatus of claim 3 wherein said lens member is structured and disposed to define a plurality of zones having an effective horizontal angular field of view of at least 160 degrees.
7. The apparatus of claim 6 wherein said lens member is structured and disposed to define at least three vertical levels of vision.
8. The apparatus of claim 1 wherein said lens member is structured and disposed to define at least two vertical levels of vision.
9. The apparatus of claim 8 wherein said lens member is structured and disposed to define at least three vertical levels of vision.
10. The apparatus of claim 8 wherein said characteristic transverse dimension is at most about 26 mm.
11. The apparatus of claim 1 wherein said lens member is structured and disposed to define a plurality of zones having an effective horizontal angular field of view of 160 degrees.
12. The apparatus of claim 1 , wherein said sensor has an entrance window for infra-red radiation and said sensor is disposed in said compact interior region proximal to a rear wall of said housing and distal to said lens member, whereby said entrance window is spaced from said lens member by greater than one-half of said characteristic transverse dimension.
13. The apparatus of claim 1 , wherein a filter circuit for said sensor is mounted in said compact interior region along with said sensor.
14. A decorative lighting fixture activated by an infra-red motion detector for monitoring motion in a monitored region, wherein the motion detector includes a motion detector housing having a decorative external appearance and disposed to form an integral part of the lighting fixture, an infra-red sensor disposed within the housing, and a segmented Fresnel lens member for directing infra-red radiation from the monitored region to the infra-red sensor, wherein the lighting fixture is characterized in that:
said motion detector housing and said segmented Fresnel lens member define a generally cylindrical portion with an interior region having a characteristic transverse dimension of at most about 28 mm;
said infra-red sensor is mounted in said interior region;
said lens member is structured and disposed in said motion detector housing to direct infra-red radiation to said sensor from a plurality of zones in said monitored region, said plurality of zones having a horizontal angular field of view of at least 160 degrees;
wherein said lens member is structured and disposed to define at least three vertical levels of vision.