Abstract:
A device for soft irradiation comprising a reflector having a cross-section in the shape of a spiral and an electromagnetic radiation source positioned off-axis such that the source is shielded from direct view. A cooling vent and openings provide impingement cooling of the source to allow efficient use of a high intensity radiation source. Cooling of the source may be further improved with the addition of one or more fluid moving devices in flow communication with the reflector. Optical reflectance coatings on the surface of the reflector or transmission filters allow the device to provide radiation output in selective bandwidths. Multiple reflectors may be used in combination to evenly illuminate complex or large surfaces. There are specific utilities to this design with both pulsed and continuous light sources.

Description:
Applicant claims the benefit of the filing date of U.S. Provisional Patent Application No. 60/143,029 filed Jul. 9, 1999, entitled “Device for Soft Irradiation”. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a device to produce gradient soft irradiation through the use of off-axis placement of a radiation source within a spiral reflector which completely encloses the source. The present invention also relates to the use of optical coatings in conjunction with the device in order to enable the device to emit selective narrow bandwidths of radiation. 
     2. Description of the Prior Art 
     A. Currently Used Collimators 
     Currently used collimators, such as lensing and parabolic reflectors, emit collimated, spatially coherent electromagnetic energy. At the aperture of these collimators, all electromagnetic energy is spatially coherent. Spatially coherent light will produce sharp shadows. 
     B. Reflector Design 
     Spiral based curves have been used for the collection of energy. For example, U.S. Pat. No. 3,974,824, Solar Heating Device, discloses a solar heating device utilizing a cylindrical reflector with a spirally extending section and a parabolically section for concentrating solar energy on an axially disposed absorber carrying a fluid to be heated. In this device, the incoming energy is concentrated along the axis of the spiral. 
     Additionally, spiral reflectors have been used to illuminate walls, as per U.S. Pat. No. 4,564,888, Wall Wash Lighting Fixture. The reflector of this device, however, discloses only the use of a light bulb within a reflector which does not fully enclose the bulb. 
     C. Light Filter Design 
     Ordinary light filters often absorb 50-90% of the desired wavelengths to eliminate the unwanted portion of the spectrum. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide a device for soft irradiation having a spiral shaped reflector used with an electromagnetic radiation source positioned such that the source is shielded from direct view and is located off of any focal axis of the reflector, such that output from the source undergoes at least one reflection and has soft or multi-angled dispersion without spatial collimation. 
     It is a further object of the invention to provide impingement cooling of the radiation source to allow efficient use of a high intensity radiation source. 
     It is another object of the invention to allow output in selective bandwidths through the use of optical reflectance coatings on the surface of the reflector or transmission filters. 
     It is also an object of the invention to combine multiple reflectors in conjunction with one another to evenly illuminate complex or large surfaces. 
     More particularly, the present invention is directed to off-axis localization of linear and point sources of electromagnetic irradiation within spiral curve reflectors to produce gradient soft irradiation with approximately linear power degradation with respect to distance. The joining of multiple spirals can be adjusted to uniformly irradiate complex surfaces. In contrast to currently used collimators, such as lensing and parabolic reflectors, the radiation emanating from the source of this invention is dispersed spatially at the aperture without parallel rays, producing a soft pattern of irradiation. Additionally, the present invention is directed to the application of optical reflectance coatings to the inner surface of the spiral reflector to produce emission of selective narrow bandwidths of radiation from a broader bandwidth source. The invention apparatus will have application to the fields of phototherapy (both adjuvant and endogenous reactions), tanning, photography, lithography, electromagnetic activated chemical reactions, and heat transference. With both pulsed and continuous light sources there will be specific utilities to this design. 
     Examples of arrangements within the scope of the present invention are illustrated in the accompanying drawings and described hereinafter, but it will be understood that neither the drawings nor the descriptions thereof are presented by way of limitation and that other arrangements also within the scope of the present invention will occur to those skilled in the art upon reading the disclosure set forth herein. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a device of the present invention. 
     FIG. 2 is a side view of the device of FIG.  1 . 
     FIG. 3 is a top view of the device of FIG.  1 . 
     FIG. 4 is a sectional view taken along the line  4 — 4  of FIG.  3 . Airflow patterns are shown by the arrows. 
     FIG. 5 is a front view of a cabinet and reflector arrangement of the present invention. Airflow patterns are shown by the arrows. 
     FIG. 6 is a sectional view taken along line  6 — 6  of FIG.  5 . Airflow patterns with respect to the left reflector are shown by the arrows (omitted with respect to the right reflector). 
     FIG. 7 is a typical reflectance curve for a device of the present invention utilizing an optical reflectance coating. 
     FIG. 8 is a side sectional view similar to FIG. 4 showing a pair of transmission filters offset across the interior opening of the reflector. Airflow patterns are shown by the arrows. 
     FIG. 9 is also a side sectional view similar to FIG. 4 showing a single transmission filter across the interior opening of the reflector. 
     FIG. 10 is a perspective view of an alternative embodiment of a device of the present invention. Airflow patterns are shown by the arrows. 
     FIG. 11 is a perspective view of yet another embodiment of a device of the present invention. Airflow patterns are shown by the arrows. 
     FIG. 12 is a perspective view of a further embodiment of a device of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in FIG. 1, a preferred device of the present invention comprises a spiral reflector  10  and an electromagnetic radiation source  12 . The device produces gradient soft irradiation through the off-axis placement of the radiation source  12  completely enclosed within the spiral reflector  10  such that the device emanates only reflected radiation. In other words, the spiral reflector  10  completely encloses the radiation source  12  such that the radiation source  12  is not directly visible from the exterior of the reflector  10 . Thus, all radiation emitted from the device is reflected at least once, producing a more linear degradation of the intensity of the emitted radiation. 
     It should be understood that a light source, such as a light bulb or tube, is a type of electromagnetic radiation source emitting radiation with wavelengths in at least a portion of the visible spectrum. Because the device of the present invention is usable at wavelengths outside the visible spectrum, the source will be referred to herein as an electromagnetic radiation source. 
     A spiral is the locus in a plane of a point moving around a fixed center at a monotonically increasing or decreasing distance from the center. An Archimedes spiral, having a general polar equation of r=aθ and beginning at the origin of a coordinate axis system, is the basis for the spiral design of the preferred embodiment. 
     A focal axis of an optical system is the locus of points forming an axis of symmetry to which parallel incident rays converge or from which they appear to diverge. 
     An placement of the radiation source  12  off of the coordinate or any focal axis (“off-axis”) within the spiral reflector  10  described above will produce gradient soft illumination. FIG. 2 shows the typical off-axis placement of the radiation source for the preferred embodiment. 
     Additionally, use of nautilus spiral and involute of the circle spiral reflectors in conjunction with the off-axis placement of the radiation source  12  as described above will produce gradient soft irradiation output. 
     Also shown in FIGS. 1 and 4, venting of the spiral reflector near the radiation source  12 , typically a tubular bulb, in order to provide impingement air cooling of the source  12 , is provided in part through cooling vent  14 , and cooling openings  16  in side closure members  18 . The off-axis placement of the source  12  allows for this method of cooling to be used. 
     It should be understood that references herein to air cooling are equivalent to cooling by any fluid substance, and fluid cooling is interchangeable with air cooling. 
     As shown in FIGS. 5 and 6, impingement air cooling in the preferred embodiment is facilitated by cabinet  22  having intake holes  28 , outlet hole  30 , and being sealed with a substantially transparent window  26 , in conjunction with blower  24 . Blower  24  serves to pull out of the cabinet  22  through outlet hole  30 , creating an area of lower pressure between the radiation exit aperture of the reflectors  10  and the transparent window  26 . Thus, air is pulled into the cabinet through intake holes  28 , into the reflector through cooling vent  14  and cooling openings  16 , over and around radiation source  12 , and out through the radiation exit aperture of the reflector  10 . The spiral shape of the reflector  10  and off-axis placement of the radiation source  12  contribute to the cooling efficiency of the design as the airflow described above creates a turbulence around the radiation source  12 . This design permits the use of high intensity radiation sources to be used within the completely enclosing reflector  10 . 
     It should also be understood that the blower  24  shown in the Figures hereto is intended to be a generic representation of a mechanical device causing the movement of a fluid, such as air. Devices of this type are well known in the art and the exact type of device is not critical to scope of this invention. 
     FIG. 6 also shows the preferred placement of two spiral reflectors—utilizing the opposing gradient illumination patterns of each reflector to produce a uniform illumination of a surface. Additionally, the preferred embodiment allows for the stacking of multiple pairs of reflectors to provide illumination of surfaces of virtually any size or shape. 
     Also shown in FIG. 4, the inner surface of the spiral reflector  10  of the preferred embodiment has an optical reflectance coating  20  which efficiently reflects only select wavelengths. Since much of the radiation emitted from the device is reflected multiple times before exiting, the device will emit bands of radiation with sharp delineation. Optical reflectance coatings are often 95-99% reflective over the desired bandwidth and less than 10% reflective elsewhere. Thus, multiple reflections will effectively eliminate the undesired bandwidth while preserving the desired bandwidth. FIG. 7 shows a typical reflectance curve for the preferred embodiment. 
     Further aiding the selective wavelength emission from the device, substantially transparent window  26  may by design have filtering characteristics with respect to certain wavelength radiation. 
     Alternative embodiments of the invention utilizing select transmission filters  32  are shown in FIGS. 8 through 11. 
     FIG. 8 shows a pair of transmission filters staggered across the interior opening of the reflector  10  such that radiation from the source  12  will be filtered while cooling air may continue to flow around the source. 
     FIG. 9 shows an alternate version of the filter design of FIG. 8 wherein a single transmission filter  32  is utilized across the interior opening of the reflector  10 . This design allows use of a reduced size transmission filter  32 . 
     FIGS. 10 and 11 show yet another embodiment of the invention wherein transparent window  26  is placed directly across the radiation exit aperture of the reflector  10 . Again, substantially transparent window  26  may by design have filtering characteristics with respect to certain wavelength radiation. 
     The embodiment shown in FIG. 10 utilizes a blower  24  to push air into cooling openings  16  in side closure members  18 . Notably, cooling vent  14  is removed from this embodiment, forcing air through entering through cooling openings  16  to exit through aperture  34  cut along the outer edge of the reflector  10 . 
     FIG. 11 shows the embodiment of FIG. 10 with the addition of a second blower  25  located at aperture  34  to pull cooling air out of the reflector  10 . Thus, higher efficiency cooling is achieved by both pushing and pulling (push-pull) cooling air through the reflector  10 . 
     An additional efficiency of the device is that almost all light emitted by the radiation source  12  is collected from beneath, behind and around the source  12  and reflected in a forward direction rather than back into the source  12 . Thus, a lower initial amount of radiation is necessary to achieve desired output levels, reducing energy consumption and undesired heat. 
     The device may utilize both pulsed and continuous radiation sources. Pulsed electromagnetic irradiance from this device will have specific advantages over continuous light in the irradiation of biological tissues and in initiating photochemical reactions. These include the following: 
     Pulsed irradiance allows for the activation of endogenous and exogenous photochemical reactions important to the treatment of skin diseases such as psoriasis, generation of vitamin D, and other light driven reactions. 
     Pulsed irradiance allows for deeper penetration of high intensity electromagnetic energy. When there is a threshold dependent photochemical reaction this will permit the reaction to take place deeper within the surface. The energy is delivered in picosecond to millisecond intervals. 
     Pulsed irradiance may be regulated within fractions of a second. 
     Higher peak powers will allow for photochemical reactions heretofore unknown. 
     Pulsed energy which is translated to heat can be dissipated between the pulses. 
     In conditions where the targeted absorption of electromagnetic irradiation is greater than surrounding tissue, pulsing will enhance the relative heating of the region. For example, dark hair follicles will be selectively heated during pulsing, resulting in destruction of unwanted hair with less discomfort to the surrounding tissue. 
     The preferred embodiment of the device utilizes a pulsed Xenon flash tube as the radiation source  12 . Xenon tubes are rated to last for many years of continuous use, and provide stable output over the years. The pulsed Xenon embodiment of the device provides extremely reliable dosimetry. 
     An additional embodiment of the invention utilizing a plurality of radiation sources  36  is shown in FIG.  12 . This embodiment allows for different wavelength sources  36  to be utilized, ie. single color lights for mixing of hue and temperature of the light at the radiation exit aperture of the reflector  10 . 
     It will be understood that the forgoing examples are not by way of limitation of the present invention and that other arrangements also within the scope of the present invention will occur to those skilled in the art upon reading the disclosure set forth herein.