Illumination – Light source and modifier – Including reflector
Reexamination Certificate
2000-02-24
2001-09-11
Sember, Thomas M. (Department: 2875)
Illumination
Light source and modifier
Including reflector
C362S298000, C362S301000, C362S302000, C362S303000, C362S304000, C362S305000, C362S346000
Reexamination Certificate
active
06286979
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to systems for illuminating a desired area with electromagnetic radiation, such as visible or infrared light, with a desired intensity distribution, for example using an integrating cavity, a port and a fan-shaped deflector structure. Preferably, the cavity takes the form a constructive occlusion type mask, cavity and shoulder providing a tailored intensity distribution of radiant energy over one region, while the port and deflector provide illumination of another region.
BACKGROUND
Radiant or electromagnetic energy emitters and distributors find a wide range of applications in modern society. Visible illumination systems, for example, illuminate areas and surfaces to enable use by personnel even though natural ambient lighting might be insufficient. Infrared illumination is a critical component of many night-vision technologies.
Different applications of radiant energy illumination systems require different performance characteristics. For example, a visible illumination application might require that the lighting system provides a desired minimum intensity over a flat surface of specified dimensions about an axis of the lighting system, at a known distance from the system along its axis. Simple radiation sources, such as light emitting diodes (LEDs) or light bulbs with reflectors and/or lenses typically provide a high intensity radiation in regions close to the axis, but the intensity drops off quickly at angles approaching the horizon. On an illuminated surface, the intensity is not uniform, as often desired.
To provide a desired illumination at edges of a design footprint, the source often will emit substantially higher amounts of radiation than necessary along the axis. Although such an approach may meet minimum requirements, it requires an excessive amount of power.
Prior attempts to provide desired intensity distributions have involved complex arrangements of sources, lenses and reflectors. These complex arrangements tend to be relatively expensive and sensitive to problems of misalignment, which limits ruggedness and durability.
As an example of a difficult lighting application, consider illumination of the vehicle filling area, under a canopy, in a modern self-serve type gas station or the like. Light fixtures are attached to the underside of the canopy. Such fixtures must distribute light downward toward the ground. The illumination system must also provide some illumination at an angle to illuminate vertical surfaces of the pumps. To achieve desired lighting, the requirements for such an application actually specify desired downward intensity and angular coverage and require some amount of up-lighting at an angle onto the underside of the canopy. A problem arises, however, where illumination systems meeting such requirements also distribute a substantial portion of the light outward at angles approaching the horizon. The light emitted in this later direction actually “trespasses” on adjacent properties, and in many instances, is disturbing to persons living on or using the adjacent properties.
U.S. Pat. No. 5,733,028 issued Mar. 31, 1998 to Ramer et al. discloses a number of embodiments of illumination systems that utilize constructive occlusion. With this technology, a mask occludes an active optical surface, typically a Lambertian surface formed by the aperture of a diffusely reflective cavity. In most embodiments, a reflective shoulder surrounds all or at least a portion of the aperture. The mask, cavity and shoulder distribute radiant energy from within the cavity out over an area, with a tailored intensity distribution. The disclosure there emphasizes uniformity of the intensity distribution, for example with respect to angles extending over a hemispherical radiation pattern. Adjustment of the parameters of the constructive occlusion system enables the system designer to tailor the system performance to a wide range of applications.
However, a need still exists for radiant energy or electromagnetic emission and distribution systems, which can satisfy certain specialized requirements as to a desired intensity distribution. Such systems must be relatively simple in structure, to minimize cost and maximize durability. Also, such systems should be able to achieve a desired intensity distribution including at least some area beyond the horizon of the aperture, and in some instances exhibiting a dead zone at or near the horizon. In the gas station example, such a dead zone at or near the horizon would help to minimize light trespass on adjacent properties.
DISCLOSURE OF THE INVENTION
The invention addresses the above stated needs and overcomes the stated problems by providing a port and deflector structure on an optical-integrating cavity, preferably the cavity in a mask and cavity type constructive occlusion illumination system.
One aspect of the invention relates to a lighting system, comprising a diffusely reflective optical-integrating cavity and a source coupled to emit light into the cavity. An elongated port extends along a portion of a perimeter of the cavity. This port provides passage for light from within the cavity. The system includes two reflectors mounted along opposite edges of the port. Each reflector has a reflective surface extending at an angle from one elongated edge of the port toward a region to be illuminated. These reflective surfaces form a deflector, coupled to the port. In a circular system embodiment, for example, the deflector would fan around all or a part of the periphery of the circular cavity. One or more deflectors may fan or extend along the side(s) of a rectangular system. The deflector expands outward along its length as the surfaces extend toward a region to be illuminated. The deflector directs the light from within the cavity over the region to be illuminated.
The deflector surfaces may be formed on a variety of structures. For example, the reflectors may be formed on facing surfaces of two angled plates or on a surface of a solid base and an opposing surface of a plate. Alternatively, the deflector may utilize total internal reflection, in which case, the surfaces correspond to the boundaries between a transparent solid and the surrounding environment.
The preferred embodiments combine the port and deflector structure with the elements of a constructive occlusion illumination system. The constructive occlusion provides illumination for one region, and the port and deflector illuminate another region.
Another inventive aspect therefore relates to a system for projecting electromagnetic radiation with predetermined intensity over two distinct regions. The system includes a base, which has a defined area substantially facing a first region to be illuminated. This area of the base exhibits a reflective characteristic with respect to the electromagnetic radiation. Preferably, a shoulder is adjacent to and extends along a portion of the defined area of the base, although the shoulder may be omitted. If included, the surface of the shoulder, which faces toward at least a portion of the first region, has a reflective surface. The system further includes a mask between the base and the first region, at a predetermined distance from the defined area of the base. On the mask, an area substantially facing the defined area of the base also is reflective. A source emits electromagnetic radiation for reflection between the defined areas of the base and mask, such that the base, mask and shoulder provide a tailored intensity distribution of electromagnetic radiation over the first region to be illuminated. The system also includes a port and a deflector. The port extends through the base or the mask, from the defined area thereof toward a second region to be illuminated. The deflector has a reflective inner surface extending and expanding from a narrow end coupled to the port toward the second region. The regions may overlap, or one region may include the other. In certain preferred embodiments, the second region includes at least a substantial area that is outside the first region. In se
Brown Matthew
Rains, Jr. Jack C.
Ramer David P.
Alavi Ali
McDermott & Will & Emery
Sember Thomas M.
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