WO2005114265A1

WO2005114265A1 - Light flux transformer

Info

Publication number: WO2005114265A1
Application number: PCT/US2005/016562
Authority: WO
Inventors: Bernard J. Eastlund; Michael W. Ingram; Reginald W. Clark
Original assignee: Novatron Inc
Current assignee: Novatron Inc
Priority date: 2004-05-13
Filing date: 2005-05-11
Publication date: 2005-12-01
Anticipated expiration: 2006-11-13

Abstract

An apparatus for exposing surfaces on objects to UV radiation includes a light source (36) and a chamber (32) having an interior surface covered with a reflective material, which may be a Lambertian reflector. Light generated by the light source (36) is reflected, usually many times, within the chamber (32), significantly increasing the light flux through an aperture (40) in the chamber (32). A method of increasing light flux is also described, wherein light generated by a light source (36) is reflected multiple times within a chamber (32), and then permitted to exit the chamber (32) through an aperture (40).

Description

LIGHT FLUX TRANSFORMER

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Serial No. 60/571,552, filed on May 13, 2004, which is hereby incorporated by reference. BACKGROUND OF THE INVENTION Field of the Invention This application relates to methods and systems for focusing light emitted from a light source. In particular, certain embodiments relate to focusing ultraviolet light. Description of the Related Art In many applications requiring illumination by light, a reflector guides the light rays from a light source to illuminate an object or surface. Figure 1 depicts an exemplary elliptical reflector 10, as is widely used to shape light for a variety of purposes. The elliptical reflector 10 has a specularly reflective interior surface 12, which may be used to reflect light 14 from a light source 16 towards a point 18 at which the intensity of the light is very high. However, while elliptical reflectors such as the reflector 10 of Figure 1 are able to shape light so as to increase the light flux along a given line 18, it would be desirable to provide a more efficient method or system for increasing light flux and directing the light to a particular area. Conventional optical systems typically do not uniformly illuminate an object or surface region without considerable design and expensive focusing elements, because of the finite size of the light-emitting region of a lamp. Accordingly, improved methods and systems for focusing a light source are desired. SUMMARY OF CERTAIN INVENTIVE ASPECTS The system, method, and devices of the invention each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this invention, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled "Detailed Description of Certain Embodiments," one will understand how the features of this invention provide advantages over other illumination devices. In one embodiment, an apparatus for exposing surfaces on objects to UV radiation, is provided, the apparatus including an outer housing having an inner surface area, where at least some of said inner surface area is diffusely reflective to UV radiation, a UV light source located within the housing, and at least one aperture in the housing, where the aperture permits UV radiation to exit the chamber. In another embodiment, an apparatus for exposing surfaces on objects to UV radiation is provided, including a housing having an inner surface area, where at least some of said inner surface area is diffusely reflective to UV radiation, a spectrally selective surface within the housing where the spectrally selective surface includes a material with wavelength dependent absorbing, transmitting, and/or reflecting characteristics, a UV light source located within the housing, and an aperture in the housing, where the aperture permits light to exit the housing. In yet another embodiment, a method for focusing light is provided, including generating light within a chamber, reflecting the light off of at least one substantially Lambertian reflective surface on an inner surface of the chamber, and selectively permitting light to leave the chamber based on the direction in which said light is traveling. In yet another embodiment, an apparatus for exposing surfaces on objects to UV radiation is provided, including a UV light source, a housing including means for increasing the flux density of the generated light, and an aperture. In another embodiment, the invention comprises an apparatus for exposing surfaces on one or more objects to UV radiation comprising an outer housing having an inner surface area, wherein at least some of the inner surface area is diffusely reflective to UV radiation, a UV light source located within or outside the housing, and providing UV radiation to the interior of the housing. The one or more objects are positioned within the housing and receive a substantially uniform exposure to UV radiation. h another embodiment, the invention comprises a method of curing a material with UV radiation comprising reflecting UV light from a diffusely reflective surface and illuminating a curable material with the reflected light. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of an elliptical reflector. Figure 2A is a diagram illustrating light reflected from a specular reflector. Figure 2B is a diagram illustrating light reflected from a diffuse reflector. Figure 3 A is a cross-sectional view of one embodiment of a light transformer box, which is located over a roller system. Figure 3B is a view of the underside of the light transformer box of Figure 1 A. Figure 4A is a cross-sectional view of another embodiment of a light transformer box, which has light focusing structures located at edges of an aperture. Figure 4B is a schematic view of the underside of the light transformer box of Figure 2A. Figure 5 is a schematic view of the underside of another embodiment of a light transformer box which has multiple apertures. Figure 6 is a cross-sectional view of another embodiment of a light transformer box which has multiple light sources. Figure 7 is a cross-sectional view of another embodiment of a light transformer box having features which reduce the amount of infrared light transmitted through the exposure slot. Figure 8 is a cross-sectional view of another embodiment of a light transformer box in which light is transmitted out of the transformer box via optical fibers coupled to apertures. DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS The following detailed description is directed to certain specific embodiments of the invention. However, the invention can be embodied in a multitude of different ways. In this description, reference is made to the drawings wherein like parts are designated with like numerals throughout. Disclosed herein are new systems and methods for applying flux multiplier methods and apparatus, such as those described in U. S. Patent Application, 10/724,017 dated November 26, 2003, which is hereby incorporated by reference in its entirety, hi an advantageous embodiment, light from a light source is collected in an enclosure lined on an inner surface or made with a diffuse reflective material. In this embodiment, the light may then be emitted onto a substrate outside of the enclosure by allowing the light to pass through an aperture in the enclosure. Accordingly, due to the low light loss collecting nature of the enclosure, the light emitted through the aperture may have a higher peak intensity than would otherwise be available from the light source alone or in combination with a conventional reflector. Transforming non-uniform light radiation from an arbitrarily shaped light source (i.e. linear, spherical, cylindrical etc.) to provide desired patterns of radiation may be usable in various applications. For example, the emission from a 6-inch long cylindrical UV lamp could be collected and transformed by the light transformer to produce a uniform flux density pattern over a circular, square or triangular area with a characteristic dimension of, for example, 10 inches or more. In other applications, the emission from a short cylindrical lamp could be shaped to produce uniform flux density over a rectangular pattern that is much longer than the axial length of the lamp. Shaping of light may be used in applications, such as, for example, UV curing of inks and coatings. Alternate applications which could utilize the shaping of light include, but are not limited to, high efficiency light beams, infrared drying or cooking, medical light applications, and decorative light applications. The light transformer can also be used to produce highly uniform illumination patterns over the surfaces of 3-dimensional objects with complicated surface shapes. Such objects can, for example, be introduced into the light transformer cavity where they will be exposed to highly uniform flux density from all directions. This approach can, for example, provide uniform curing of all the surfaces of 3-dimensional objects without the need to translate or move the object or lamp relative to one another. Elliptical reflectors of the type discussed with respect to Figure 1 generally utilize a specularly reflective surface. Figure 2A is a diagram illustrating light 20 reflected from a specular reflector 22 and and Figure 2B is a diagram illustrating light reflected from a diffuse reflector 24. In Figures 2A and 2B, the incident light is represented as solid lines, and the reflected light is represented as dashed lines. As shown in Figure 2 A, the specular reflector 22 reflects an incident light 20 predominately in one direction, which is determined by the angle of incidence. One example of a specular reflector is a mirror in which the angle of incidence and the angle of reflection are substantially identical. Conversely, the diffuse reflector 24 reflects the incident light 20 in all directions regardless of the angle at which it is incident on the diffuse reflector 24. A diffuse reflecting surface is typically referred to as Lambertian. A Lambertian surface is defined as a surface from which the energy emitted in any direction is proportional to the cosine of the angle which that direction makes with the normal to the surface. For example, if diffuse reflector 24 represents a portion of a panel in a light transformer, incident light 20 will be scattered from the panel in all directions regardless of the shape of the diffuse reflector 24 and the relationship of other panels in the light transformer. By making the surfaces of the interior of the light transformer highly diffusely reflective, the fluence within the transformer may be substantially uniform regardless of the chamber geometry, light source geometry, and light source location within the light transformer. Thus, a substantially uniform illumination inside the light transformer is possible regardless of the geometric shape of the chamber and the location of the light source within the chamber. Figure 3 A is a cross-sectional end-view of an embodiment of a light transformer 30. In the present embodiment, the light transformer 30 comprises a chamber 32. The walls 34 of the chamber 32 are lined on the inside with a material which is a highly diffuse reflective surface, such as a Lambertian reflector having high reflectivity, hi one embodiment, the highly diffuse reflective surface may comprise one or more of: Spectralon™ which has a reflectivity of about 94%, ODM, manufactured by Gigahertz- optik, which has a reflectivity of 95%, and DRP which has a reflectivity of 99.4 to 99.9%. Spectralon™, which is a highly Lambertian, thermoplastic material that can be machined into a wide variety of shapes to suit various reflectance component requirements, may be purchased from Labsphere, Inc. DRP can be purchased in sheet form, with a peel and stick backing from W.L. Gore and Associates. In another embodiment, the walls may be lined with a highly reflective material that comprises an Alzak oxidized aluminum, which has a reflectivity of about 86%. The light transformer 30 comprises a light source 36 located within a light housing reflector 38. In one embodiment, the light source 36 may be any source of UV, such as a microwave-excited UV source such of the type manufactured by Fusion UV Systems, fric; a flashlamp or a pulsed lamp, which provides broad spectrum pulsed light and can be purchased through vendors such as Fenix, of Yuma, Ariz.; medium pressure mercury arc lamps, available from Hanovia Corp.; or germicidal lamps. The housing reflector 38 is also lined on the inside with material which is a Lambertian reflector with high reflectivity. Light emitted from the light source 36 is reflected many times from the reflective surfaces of light housing reflector 38 and walls 34, building up a high value of light flux that effectively multiplies the flux of the lamp by factors of 30 or more. The factor by which the flux is increased is dependent on the reflectivity of the Lambertian material lining the interior of the light transformer 30. A higher reflectivity will result in a larger increase in the effective flux of the lamp. The radiance of the surfaces inside the chamber 32 is given by

where Φ .„ (λ) is the spectral power (Watts/nm) input to a chamber of surface area

A_s , R(λ) is the reflectivity of the chamber walls and internal surfaces as a function of wavelength, and f(λ) is the ratio of absorbing surface area to reflecting surface area, where the spectral dependence in f(λ) arises from the spectral properties of the absorbing and reflecting surfaces. Typically, such systems are designed with spectrally flat material properties, so the wavelength dependence is negligible. By choosing materials with a value of R(λ) close to 1 (for example, 0.998, which is typical of DRP expanded Teflon material from W. L. Gore company) and keeping f(λ) as low as practicable, large surface radiances are possible inside the chamber with relatively small input power. In certain embodiments, the value of f(λ) may advantageously be 0.05 or less, h addition, the irradiance on an object within the chamber will be substantially uniform throughout the chamber as long as there is no direct line-of-sight between the object and the input source. The object irradiance is about 6 times the wall radiance for a rectangular-shaped chamber. An exposure slot 40 for useful light rays allows some of this trapped and flux- multiplied light to escape. This light may then strike a surface that benefits from exposure to the light, such as a surface having, for example, a coating that requires UV curing, h Figure 3A, a surface 42 is shown suspended by rollers 44, and positioned underneath the exposure slot 40, such that a portion of the surface 42 is exposed to light which passes through the exposure slot 40. The rollers 44 can advance the surface 42, so as to expose a strip of the surface 42 to light over time. In certain embodiments, the rollers 44 and the surface 42 may comprise a portion of a conveyor system, on which material to be exposed to light may be placed. In other embodiments, the rollers and surface may comprise a system for passing a sheet or film of material to be exposed to light underneath the exposure slot. In the embodiment of Figure 3 A, a light baffle 46 may be used to prevent most or all of the light rays from the light source 36 from entering the main portion of the chamber 32 without first reflecting off the housing reflector 38. The surfaces of the light baffle 46 are advantageously also coated with a highly reflective Lambertian material. The use of such a baffle may be particularly advantageous in alternate embodiments of a light transformer in which an item to be cured via UV or cooked via infrared is placed within the chamber itself, hi these embodiments, of course, an aperture or exposure slot for UV light exit from the housing is not necessary. In such a situation, it may be desirable to have a substantially uniform irradiance over the surface of the object which, as discussed above, can be achieved by keeping the object out of direct line-of-sight between the object and the light source. In alternate embodiments, a light battle such as baffle 46 may be placed closer to the exposure slot 40, so as to simply prevent direct rays from the light source 36 from exiting the exposure slot 40 without first reflecting off the enclosure walls 34. hi the embodiment of Figures 3 A and 3B, it can be seen that the main portion of the light transformer 30 is rectangular in cross-section, forming a box shape. However, in alternate embodiments, other shapes may be utilized. For instance, the main portion of the light transformer 30 may be a cylinder or a frustum. In addition, although the light housing reflector 38 is depicted in Figure 3 A as being substantially hemispherical, the housing reflector 38 may be part of an ellipsoid, or may be any other extension of the cavity 32 within the light transformer 30. In yet other embodiments, there may be no distinct light housing reflector 38, such that the light source 36 is simply placed within a cavity. Also, the position of the light source 36, while depicted near the upper portion of the light housing reflector 38 in Figure 3 A, may be placed elsewhere as appropriate. The exemplary materials discussed previously are examples of "substantially Lambertian" materials. While in a preferred embodiment, the interior surfaces 34 of the light transformer 30 are covered with a Lambertian or substantially Lambertian reflector, in alternate embodiments the interior surfaces may be covered with a reflective layer which is not a substantially Lambertian reflector. Although the use of an alternate material, such as a diffuser layer, may decrease the efficacy of the device and the evenness of the light flux distribution, such tradeoffs may be desirable in certain situations. h another embodiment, additional structures are added to the light transformer 30 to help concentrate the light exiting through the exposure slot 40. Figure 4A is a cross- sectional view of an exemplary light transformer 56. As shown in Figure 4A, the light transformer 56 includes light focusing structures 58 near the exposure slot 40 that are configured to increase concentration of the light leaving the slot exposure slot 40. In the embodiment of Figure 4 A, these light focusing structures 58 are inverted triangular shapes. The light focusing structures 58 help select light rays approaching the exit slot 40 that are more normal to the surface 42 to be exposed so that the rays will strike the surface to be exposed in a desired limited exposure region, h one embodiment, the light focusing structures 58 also reflect some rays exiting the slot at a shallower angle to the treated surface back into a narrower area on the treated surface. In an advantageous embodiment, the light focusing structures 58 shown in Figure 4 A are also covered with a material that is a substantially Lambertian reflector with high reflectivity. Many other shapes of light focusing structures are possible and could be similarly used to optimize the intensity profile on the treated surface and / or achieve a desired intensity profile for a particular application. The light focusing structures are not necessarily limited to being located inside the enclosure, nor to having substantially Lambertian reflective properties. Figure 4B is a cross-sectional bottom view of the light transformer 56, including the slot for useful light rays 40 and the light focusing structures 58. As illustrated in Figure 4B, the light focusing structures 58 are configured to focus the light exiting the slot 40 to a narrower area than is possible without them. Although not depicted, light focusing structures having other configurations are contemplated. For example, light focusing structures similar to 58 could alternately be placed along the upper and lower edges of the exposure slot 40, in addition to or in place of the light focusing structures 58 depicted along the side edges of the slot, so as to give additional control over the shape of the area exposed to light from the exposure slot 40. The power exiting the box, P_mt , through the exposure slot 40 is related to the box geometry and the box light multiplying factor, M, by the expression:

P ¹ out = J f slot M^lvlP¹ in

^aiamp ^{+ a} other Λ loss f — ^aslot J slot ^As where P_in, P_gut = Optical power into the enclosure or out of the slot ^ai_amP ⁼ Lamp absorbing area ^a _other ⁼ Surface area of other absorbing features or openings ^a _si_ot ⁼ Area of exposure slot A_s = Total internal surface area p = Enclosure surface reflectivity Example 1: If the light transformer box 1000 has dimensions of 6" x 6" x 6", and the exposure slot has dimensions of 1.14" x 6 ", and if the total loss area other than the slot is 2 in², then f_slot = 0.032, f_loss = 0.0093 and M = 16.2 for a reflectivity of 0.98. So,

51.8% of the total light from the lamp exits the slot 1004. A UV microwave energized lamp, such as model F300 sold by Fusion Systems UV, produces about 200 watts of UV between 200 and 300 nm. Using this lamp as a source in the flux multiplying box described above is estimated to result in a flux in the opening of about 2.35 W/cm . h comparison, the peak flux of the same Fusion Systems UV F300 at the focus of its elliptical reflector 1.1 W/cm². The focal width of the F300 in the plane of the exposed surface is about 0.55 inches. Thus, through the use of the light transformer 1000, the peak flux provided by an F300 may be more than doubled. In addition, the area irradiated by that peak flux may be more than doubled at the same time. Thus, the flux from an elliptical reflector such as the Fusion Systems UV elliptical reflector will have a substantially different profile perpendicular to the lamp axis in the plane of lamp focus than would the flux exiting through the exposure slot of a transformer box 30 or 56. In particular, it will be understood that the flux from the transformer box will have a higher peak and a more even profile across the disclosure slot. Outside of this peak area, the profile of the flux from the transformer box will likely be lower than that of the elliptical reflector, as light from a transformer box such as 56 can be directed to a much narrower region, by selectively permitting only light traveling in certain directions to leave the transformer box, both through the use of the exposure slot and through the use of light focusing structures as discussed above. In one embodiment, a medium pressure mercury arc could also be used as the light source, with comparable improvements. Use of such a light source may provide many advantages for the curing industry. h an advantageous embodiment, the light flux transformer 30 can transform the light from a source to a desired exposure pattern using slots of various shapes. For example, Figure 5 schematically depicts the underside of an embodiment of a transformer box having a pattern of exposure slots 40 that would allow multiple spots to be exposed on a target surface, h an embodiment in which the target surface is moving relative to exposure slots 40, this pattern of exposure slots can be used to expose individual lines on a target surface. As described above, in advantageous embodiments, flux intensities much greater than possible with single lamps and focusing reflectors are possible using the light transformer system. Figure 6 is a cross-sectional view of another embodiment of a light transformer 60, including two light sources 36 mounted in light housing reflectors 38. Advantageously, the light transformer 60 increases the peak intensity coming through the exposure slot 40, up to about double that of a light transformer having a single light source 36, such as that depicted in Figures 3A and 3B. Thus, a peak intensity of about 4 times a conventional lamp with an elliptical reflector is possible, hi addition, more than two lamps 36 could be used, leading to higher and possibly more useful intensities. As seen in Figure 6, the light transformer 60 also includes baffles 46. As discussed above, depending on the placement of these baffles 46 relative to the light sources 36, these baffles may serve to prevent light from entering the main portion of the chamber 32 without first reflecting off of the light housing reflectors 38, or may prevent light from exiting the disclosure slot without reflecting off of an interior surface of the light transformer 60. In one embodiment, relatively small spectra modifying wafers 62 are placed in the light transformer in order to control the spectrum of light coming through the exposure slot. For example, a wafer 62 that reflects UV light, but absorbs infrared light, could significantly reduce the amount of infrared light from the light striking the surface to be exposed. Because the light is advantageously reflected multiple times within the light transformer 60, such a wafer may be placed anywhere in the chamber, and a significant effect on the composition of the outgoing light may be obtained. In an advantageous embodiment, a spectrally selective absorbing material is placed inside the chamber in order to introduce a spectral dependence in L as described in the equation above, since /will not be flat across the spectrum. For example, a schott glass filter with a cutoff wavelength of 230 nm could be placed inside the chamber. Such a filter could be designed to transmit >90% of the incident radiation that is above 230 nm, and absorb ~ 99% of the incident radiation that is below -230 nm. The result of this is that the absorbing fraction would be ~10 to 100 times larger for wavelengths >230 nm than for those less than 230 nm. So, the surface radiance in the chamber and the irradiance incident on an object inside the chamber or at the chamber wall would be an order of magnitude larger above 230 nm. This technique could obviously be applied at any wavelength or wavelength band where an appropriate absorber can be fabricated. Many materials will transmit or reflect all wavelengths except for a certain band (e.g., notch filters). These may be used as well. Infrared radiation may be reduced using a similar technique. However, many infrared discriminating materials commonly available will either reflect or transmit incident radiation, rather than absorbing the incident radiation. These are commonly referred to as hot (infrared reflecting) or cold (infrared transmitting) mirrors. If a cold mirror were placed in the chamber, such as on the chamber floor, it would have little or no effect on the spectral content of the chamber since the offending wavelengths are not absorbed. The IR radiation would be transmitted thru the mirror, reflected off the chamber floor, and transmitted back thru the mirror into the chamber with minimal losses; other wavelengths would be reflected back into the chamber on the first surface of the mirror rather than from the chamber wall. However, if one wanted to remove infrared radiation from a chamber, as seen in Figure 7, a cold mirror 64 could be used by placing the mirror 64 over an absorber 66 in the chamber 32. In this case, the visible and UV wavelengths are reflected by the cold mirror 64 with high efficiency (typically >90%) while the IR is transmitted with somewhat lower efficiency (typically >80%). This way, mainly IR radiation would be incident on the absorber 66, since most of the UV and visible wavelengths are reflected by the mirror 64 back into the chamber 32. As previously discussed, because baffles 46 can be used to ensure that light from light source 36 is reflected off of the interior walls at least once, and usually many times, even a small absorber 66 can have a significant effect on the spectral composition of the light exiting through aperture 40. In an alternate embodiment, as seen in Figure 7, a cold mirror 64 can be placed over a hole or opening 68 in the chamber 32. In such an embodiment, the transmitted IR can pass out of the chamber 32, never to return. Thus, / (λ) may be quite high in the IR but remains low in the UV-VIS, so the cavity will multiply the UV-VIS well, but not the IR. The use of a cold mirror 64 method has several advantages over simply using an IR absorber, such as the wafer 62 of Figure 6. First, the mirror does not get hot, as it is non-absorbing. Second, the absorbing material may be chosen independent of its reflecting properties, whereas the wafer 62 of Figure 6 may have a detrimental effect on the increase in light flux density produced by the light transformer box at desired wavelengths if it is not reflective at those wavelengths. Third, the absorbing material may be more easily cooled, as it can be located on the wall or outside of the chamber. Forth, when the mirror is placed over an opening in the wall, no absorber is needed, further simplifying the design and decreasing the amount of heat buildup which may occur due to light absorption in the light transformer 60. Figure 8 is a cross-sectional end view of a light transformer 74, where optical fibers 76 are coupled to slots or holes 78 in the light transformer 74. Thus, the increased flux density of light is efficiently transferred into or out of the light transformer 74. The optical fibers 76 can be used to guide light to precise locations, and can be used to expose multiple parts of an object to light from different angles at the same time. For instance, two light-guiding optical fibers 76 could be used to simultaneously cure opposite surfaces of a material. In addition, because light can propagate through the optical fibers 76 by means of total internal reflection, the light exiting the end of the optical fiber may be roughly collimated, enabling precision illumination or exposure of certain areas to light. In these embodiments, baffles could still be provided to block any direct line of sight between the lamp and the entrances to the optical fibers. The foregoing description details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears, the invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiment is to be considered in all respects only as illustrative and not restrictive and the scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

WHAT IS CLAIMED IS: 1. An apparatus for exposing surfaces on objects to UV radiation, comprising: an outer housing having an inner surface area, wherein at least some of said inner surface area is diffusely reflective to UV radiation; a UV light source located within or outside said housing, and providing UV radiation to the interior of the housing; and at least one aperture in the housing, wherein said aperture permits UV radiation to exit the chamber.

2. The apparatus of claim 1, wherein the housing comprises: a chamber containing said aperture, said chamber comprising a substantially Lambertian reflective interior surface; and a second chamber containing said light source from which UV light radiates into said chamber.

3. The apparatus of claim 2, additionally comprising a third chamber containing a second light source.

4. The apparatus of claim 1, additionally comprising baffle located within the housing, wherein said baffle is located between the light source and the aperture.

5. The apparatus of claim 4, additionally comprising: a second light source; a second baffle, wherein said second baffle is located between the second light source and the aperture.

6. The apparatus of claim 1, additionally comprising an optical fiber coupled to the aperture.

7. The apparatus of claim 1, additionally comprising at least a second aperture in the housing.

8. The apparatus of claim 1, wherein the reflectivity to UV light of the diffusely reflective interior surface is approximately 94% or greater.

9. The apparatus of claim 1, wherein the reflectivity to UV light of the diffusely reflective interior surface is approximately 99.4% or greater.

10. The apparatus of claim 1, wherein the light source comprises a microwave energized UV lamp.

11. The apparatus of claim 1, wherein the light source comprises a medium pressure mercury arc lamp.

12. An apparatus for exposing surfaces of objects to UV radiation, comprising: a housing having an inner surface area, wherein at least some of said inner surface area is diffusely reflective to UV radiation a spectrally selective surface within the housing wherein said spectrally selective surface comprises a material with wavelength dependent absorbing, transmitting, and/or reflecting characteristics; a UV light source located within or outside the housing, and providing light to the interior of the housing; and an aperture in the housing, wherein said aperture permits light to exit the housing.

13. The apparatus of Claim 12, wherein the housing comprises : a chamber containing said aperture, said chamber comprising a substantially Lambertian reflective interior surface; and a second chamber containing said light source from which UV light radiates into said chamber.

14. The apparatus of Claim 12, wherein the material is more absorptive to incident infrared light than to incident ultraviolet light.

15. The apparatus of Claim 12, wherein the spectrally selective surface is a schott glass filter.

16. The apparatus of Claim 15, wherein the schott glass filter has a cutoff wavelength of 230 nm.

17. The apparatus of Claim 12, wherein the spectrally selective surface is a notch filter.

18. The apparatus of claim 12, wherein the spectrally selective surface reflects a larger amount of certain wavelengths of light than other wavelengths.

19. The apparatus of claim 18, additionally comprising a second aperture in the housing, wherein the spectrally selective surface overlies said second aperture.

20. The apparatus of claim 18, additionally comprising an absorptive surface, wherein the spectrally selective surface overlies said absorptive surface.

21. A method for focusing light, comprising: generating light within a chamber; reflecting said light off of at least one substantially Lambertian reflective surface on an inner surface of said chamber; selectively permitting light to leave the chamber based on the direction in which said light is traveling.

22. The method of claim 21, additionally comprising selectively removing at least a portion of light energy at certain wavelengths from the reflected light.

23. The method of claim 22, wherein selectively removing at least a portion of light energy at certain wavelengths from the generated light comprises reflecting said light off of a spectrally selective surface comprising a material with wavelength dependent absorbing, transmitting, and/or reflecting characteristics.

24. The method of claim 21, wherein selectively permitting light to leave the chamber based on the direction in which said light is traveling comprises using light focusing structures to prevent light traveling in certain directions from leaving the chamber.

25. An apparatus for exposing surfaces on objects to UV radiation, comprising: a UV light source; a housing comprising means for increasing the flux of the generated light; and an aperture.

26. The apparatus of Claim 25, additionally comprising means for selectively removing a portion of certain wavelengths from the generated light.

27. The apparatus of Claim 25, additionally comprising means for directing said light in a particular direction.

28. An apparatus for exposing surfaces on one or more objects to UV radiation, said apparatus comprising: an outer housing having an inner surface area, wherein at least some of said inner surface area is diffusely reflective to UV radiation; a UV light source located within or outside said housing, and providing UV radiation to the interior of the housing; wherein said one or more objects are positioned within said housing and receiving a substantially uniform exposure to UV radiation.

29. The apparatus of Claim 28, wherein said object comprises a UV curable material.

30. The apparatus of claim 28, additionally comprising baffle located within the housing, wherein said baffle is located between the light source and said one or more objects.

31. The apparatus of claim 30, additionally comprising: a second light source; a second baffle, wherein said second baffle is located between the second light source and said one or more objects.

32. The apparatus of Claim 28, additionally comprising a spectrally selective surface within the housing wherein said spectrally selective surface comprises a material with wavelength dependent absorbing, transmitting, and/or reflecting characteristics; 33. A method of curing a material with UV radiation comprising reflecting UV light from a diffusely reflective surface and illuminating a curable material with said reflected light. 34. The method of Claim 33 wherein said diffusely reflective surface is provided on the inside surface of a housing. 35. The method of Claim 34, wherein said illuminating is performed outside said housing. 36. The method of Claim 34, wherein said illuminating is performed inside said housing.