GB2173889A - A reflector including prisms and a reflective coating thereon - Google Patents

Abstract

A reflector employs novel combinations of prisms and reflective coating to achieve various light distributions. In addition, the reflective coating may be used to shield an observer from the brightness in looking directly at a light source. The reflective coating may be made translucent to allow controlled percentages of light to pass therethrough.

Description

SPECIFICATION Surface coating in combination with prisms for optical control of light Background of Invention Field of the Invention The invention relates to the field of optics.

Nore particularly, the invention relates to a reflector for use in a luminaire. In still greater particularity, the invention relates to light refraction and reflection. By way of further characterization, but not by way of limitation thereto, the invention relates to a reflector which includes a transparent medium and prisms thereon with an opaque reflective coating on the outside surface of the reflector.

Description of the Prior Art Two techniques used in the design of optical systems are reflection and refraction. Refraction takes place when light passes through a transparent medium where the incident surface and the exit surface are not parallel with each other. In other words, there is a prism that is molded integrally into the transparent medium. A "prism" is generally a surface which is at an angle to the basic surface as shown in Figs. 1 and 2 and which changes the light path to redirect the light. This is shown in Fig. 1. Reflection takes place at an opaque surface as in the case of metals. If the medium is transparent, such as glass or clear plastic, a binocular prism (a prism with a 90" apex) may be molded integrally on the outside of the glass to give it total internal reflection.

This effect is shown in Fig. 2. The deficiency with binocular prisms is that, when the peaks and valleys of the prism are rounded due to manufacturing imperfections or mold equipment wear, light leaks through the prisms and is not reflected. This is shown in Fig. 3. Light leakage also occurs when the light source is large enough that the incident angle is less than the critical angle of the particular medium being used. In that case the light will not be totally reflected but will leak through as shown in Fig. 4. Broadly, the refracting and reflecting prisms may be referred to as redirecting prisms.

One requirement in a transparent medium reflector is that, regardless of the shape of the medium, the reflecting prisms must be molded therein at such an angle that the incident light ray approaches the reflecting prism on the bisector of the 90" angle of the reflecting prism. This, in effect, means that in a horizontal plane the light ray always comes back on the axis of the reflector so that it is impossible to achieve anything but a symmetric distribution from a prismatic glass reflector even though the basic shape of the reflector might- be square, oblong, or some other shape. Examples of this are shown in Figs. 5 and 6 for a square reflector.

In addition to the above mentioned problem of light distribution, other problems with reflecting prisms occur with some light sources. In particular, a high pressure sodium light source, now very popular as a high efficiency light source, is known as an unstable amalgam lamp. That is, not all of the sodium is energized but rather only a carefully controlled percentage of the sodium is vaporized.

The remainder of the sodium remains in a reservoir at one end of the arc tube. If a reflector feeds back too much light into the reservoir, it will increase the temperature of the reservoir, thereby causing more sodium to vaporize and raising the operating voltage of the lamp.

Thus, early lamp failure could result.

Another problem with prior art reflectors is that where the light source is very intense, as is a high pressure sodium light source, the eyes of an observer looking directly at the luminaire may be irritated by the intensity of the light source.

Summary of the Invention The invention is a reflector for use in a luminaire. The reflector includes prisms and surface reflective areas in order to achieve particular distribution of the light rays from the light source. The reflector may be opaque as in a metal reflector or it may be transparent.

The transparent medium may be plastic or glass. A reflective coating such as aluminum is deposited on a portion of the surface of the transparent medium. The reflective coating on the reflector is deposited in a variety of patterns and may be used to shield the eyes of an observer from light source glare. The reflective coating may also be deposited on the reflector so as to be translucent rather than totally reflective.

Brief Description of the Drawings Fig. 1 is an illustration of a refracting prism; Fig. 2 is an illustration of a reflecting prism; Fig. 3 is an illustration of light rays leaking through imperfect reflective prisms Fig. 4 is an illustration of light leakage through reflective prisms due to a large light source; Fig. 5 is a top view of light reflection in a horizontal reflector; Fig. 6 is a side sectional view of light reflection in a substantially square reflector; Fig. 7 is a side sectional view of a parabolic reflector including prisms on the outside surface of the reflector; Fig. 8 is a side sectional view of a parabolic reflector including prisms on the inner surface of the reflector; Fig. 9 illustrates an asymmetric distribution of light rays from an asymmetric reflector; Fig. 10 illustrates an asymmetric light distribution from a symmetrically shaped reflector;; Fig. 11 illustrates light ray distribution from a symmetric reflector employing the present invention such that the light rays to not impinge on the light source; Fig. 12 is a top view of a reflector with a vertical reflecting coating band thereon; Fig. 13 is a side view of a parabolic reflector including a vertical reflective coating band thereon; Fig. 14 is a side view of a parabolic reflector with a horizontal reflective coating band thereon; Fig. 15 is a side view of a parabolic reflector including a reflective coating in an elliptical configuration; Fig. 16 is a side view of a parabolic reflector including a translucent coating on a portion thereof; and Fig. 17 illustrates the application of reflectors embodying the present invention in an aisle lighting situation.

Description of the Preferred Embodiment Referring to Fig. 1, a refracting prism 11 on a transparent medium 12 is shown bending a light ray 13. This illustrates the concept of a refracting prism.

Referring to Fig. 2, a reflecting prism 14 is shown on a transparent medium 12. A light ray 15 is shown being internally reflected by reflecting prism 14.

Referring to Fig. 3, an illustration of reflecting prisms in which, due to mold imperfections or other reasons, the reflecting prisms have been rounded as shown. That is, reflecting prisms 14 are shown on transparent medium 12 with light rays 16 being reflected in some cases and refracted in others due to the imperfections in reflecting prisms 14.

Referring to Fig. 4, reflecting prism 14 in transparent medium 12 is shown reflecting a light ray 17 while refracting a light ray 18 from a large light source 21.

Referring to Fig. 5, a top view of a reflector 20 including reflecting prisms 14 and transparent medium 12 is shown with light rays 19 being reflected back at light source 21.

Referring to Fig. 6, a side view of a reflector 20 is shown with reflective prisms 14 shown reflecting light rays 23 from light source 21.

Referring to Fig. 7, a side sectional view of a substantially parabolic reflector including transparent medium 12, prisms 14, and a reflective coating 22 on the outside of the parabolic reflector is shown. Light rays 24 from light source 21 are shown being reflected from the parabolic reflector.

Referring to Fig. 8, a side sectional view pf a parabolic reflector including a transparent medium 12 is shown with prisms 14 on the outside of the parabolic reflector. A reflective coating 22 is deposited on the upper and lower portions of the inside of the parabolic reflector. Light rays 25 from light source 21 are reflected by the parabolic reflector.

Fig. 9, illustrates an asymmetrically shaped reflector including prisms 14 on transparent medium 12. Reflective coating 22 is deposited on medium 12. Light rays 26 from light source 21 are reflected by reflector 20.

Fig. 10 illustrates a symmetrically shaped reflector 20 including transparent medium 12 with prisms 14 thereon. Light rays 27 from light source 21 are reflected therefrom.

Fig. 11 illustrates a symmetrical reflector including prisms 14 on transparent medium 12 and a reflective coating 22 deposited on the outside surface of the reflector. Light rays 28 are reflected so as not to impinge on light source 21.

Fig. 12 is a top view of a reflector including a transparent medium 12 and prisms 14 on the transparent medium 12. A reflective coating is deposited on the outside of the reflector in two vertical bands 29.

Referring to Fig. 13, a side view of the reflector of Fig. 12 is shown including prisms 14 on the transparent medium and a reflective coating in a substantially vertical band 29 on the outside surface of the reflector.

Referring to Fig. 14, horizontal bands of reflecting prisms 31 and refracting prisms 30 are located on a transparent medium comprising reflector 20. A band of reflective coating 22 is deposited on reflector 20.

Referring to Fig. 15, a closed geometric shape which may be an ellipse 32 or other geometric configuration of reflective coating is deposited on reflector 20.

Referring to Fig. 16, a substantially parabolic reflector including transparent medium 12 and prisms 14 is shown. A light source 21 is shown from which light rays 33 are reflected.

A band 34 of reflective coating material is shown deposited as a translucent coating on the outside of the parabolic reflector Light rays 33 may be partially transmitted through translucent band 34 and are then emitted as rays 35 of diminished intensity to provide an area of low brightness for an observer looking at the reflector.

Referring to Fig. 17, a schematic illustrating the application of luminaires incorporating the novel reflector herein disclosed is shown. That is, luminaires 38 are shown positioned in a warehouse aisleway. Light rays are directed to specific points 36 and 37 on the aisleway.

Mode of Operation Referring to Figs. 1-6, the problems with prior art use of refracting and reflecting prisms is shown. That is, due to manufacturing imperfections, or wear of the molds or even wear on the prisms themselves, the optical properties of the prisms may be altered. Also, as shown in Fig. 4, the size of the light source can affect the optical properties of the reflecting prisms. In addition, as shown in Figs. 5 and 6, even if the reflecting prisms function normally, light is reflected back through the light source 21 which can affect the performance of the light source.

Referring to Fig. 7 a reflective coating 22 on the outside of parabolic reflector 20 in combination with the prisms 14, allows the light rays 24 to be directed away from light source 21 and in a predetermined pattern. Prisms 14 are shown in Fig. 7 on the outside surface of reflector 20. In Fig. 8, prisms 14 are shown on the outer surface of the reflector. Reflective coating 22 is deposited in a band around the inner surface of the reflector. In both cases, the light rays are directed in predetermined patterns. In Fig. 7, prisms 14 are non parallel with the inner surface of reflector 20. This allows the light rays 24 to be directed away from light source 21.

Referring to Fig. 9, a reflector 20 is shown in an asymmetric shape with light rays 26 directed in a predetermined pattern. Prisms 14 on transparent medium 12 are on the outside of reflector 20. Reflective coating 22 is deposited on the outside of reflector 20 over prisms 14.

Referring to Fig. 10, a symmetric reflector 20 is shown with prisms 14 on transparent medium 12 directing light rays 27 in a predetermined pattern. Similarly, Fig. 11 illustrates the directing of the light rays 28 away from light source 21 by the combination of prisms 14 and reflective coating 22. To prevent the degradation of the light source 21, prisms 14 are made very shallow such that, in combination with reflective coating 22, and when viewed in a horizontal plane, light rays 28 always miss the light source 21 by a predetermined amount depending on the depth of the prisms. If coating 22 was on the inside of the reflector, then prisms 14 that redirect the light would also be on the inside of the reflector.

By combining prisms with a reflective coating predetermined distributions of light rays can be varied to form a square distribution, a rectangular distribution, or a long and narrow distribution. These predetermined distributions could be used for an area light where it is desirable from a lamp operating standpoint to have the luminaire vertically oriented. Prismatic structures on the outside of the transparent medium 12 could be angled so as to provide the required asymmetry of distribution.

Referring to Figs. 12 and 13 it is possible to achieve desirable modifications of light distributions. That is, it may be possible to direct light which otherwise goes toward the ceiling to provide contrast relief in varying percentages. The combination of prisms 14 on reflector 20 with reflective coating deposited as bands 29 could be used to direct light in these predetermined directions. Referring to Fig. 13, uplight is achieved by the use of refracting prisms 14 while the reflective coating 29 is used to eliminate light leakage into unwanted areas and to direct the light to the desired areas. In addition, the use of the reflective coating 22 in the form of bands 29 may be employed to eliminate a glare problem. That is, the reflector 20 may be oriented such that bands 29 shield light source 21 from the observer.

In addition to the vertical bands which are parallel with the axis of the parabolic reflector 20 in Figs. 12 and 13, the bands of reflective coating 22 may be deposited on the parabolic reflector 20 in other configurations. Specifically, referring to Fig. 14, a band of reflective coating 22 is deposited in a horizontal configuration which is perpendicular to the axis of the parabolic reflector. An area of refracting prisms 30 directs light rays upwardly providing uplight while an area of reflecting prisms 31 directs light downwardly to specific areas.

The area of reflective coating 22 may include redirecting prisms (not shown) which, when combined with reflective coating 22, direct light rays to specific areas. It should be expressly understood that reflective coating may be used without prisms underneath the reflective coating on the transparent medium. That is the reflective coating could be applied to the glass or other medium with parallel inner and outer surfaces. Prisms would, however, be used on at least a portion of the uncoated portion of the reflector. In addition to redirecting light rays, the band of reflective coating 22 functions to shield an observer from the relatively high brightness of the sidewalls of the reflector when viewed at higher angles above nadir.

While the embodiment shown in Fig. 14 is the most preferred, variations in the width of the bands of prisms and coating as wells p!acement and combinations of the various types of prisms along with the surface coating may be employed to achieve specific desired results. In the embodiment shown in Fig. 14 each area of reflective prism, refractive prism and reflective coating are approximately the same vertical width. These widths may be varied however depending upon engineering design considerations. Similarly, variations in the placement and combination of the various types of prisms along with the reflective coating may be employed to achieve specific desired results.

As shown in Fig. 8, the reflective area 22 may be on the outside and/or the inside of the reflector. In addition, it should be noted that the reflective area may consist of multiple regions, connected or non-connected regions, of varying shapes and sizes. The reflective areas can be specularly reflective as is shown in Fig. 8 as area 22 or diffusely reflective coatings such as is shown in Fig. 16 as area 34. Examples of specularly reflective coatings would be such things as aluminum, silver, chromium, platinum, nickel, etc. Examples of diffusely reflective coatings would be such things as magnesium oxide, titanium dioxide, aluminum oxide, silicon dioxide, or also alumi num, nickel, etc.

The process for depositing the reflective coating is conventional but must be suited to the medium being deposited. It can, for example, be chemical deposition, plating, vapor deposition, thermal spraying, or hot dipping. Specific examples of vapor deposition would be a vacuum evaporation, sputtering, or iron plating. Specific examples of thermal spraying would be flame spraying, plasma, electric arc, or D-Bonding.

One application of the novel principles disclosed in the present application would be to a luminaire used in a warehouse aisle. That is, referring to Fig. 17, luminaires 38 are positioned in a warehouse aisle. In such a situation it is necessary to redirect the light to the stacks from the top to the bottom of the aisle halfway between the lighting units. This area is designated as 36 in Fig. 17. Since the luminaires are very close to the face of the stack, illumination levels are high directly opposite the luminaires at 37 and much lower midway between the luminaires at 36. Luminaires 38 include prisms on the reflector in combination with the reflective coating to allow light to be directed to area 36 as described above.

In Fig. 15, the reflective coating is deposited in a closed geometric shape such as an ellipse 32. Other configurations either geometrically definable or not, may be desirable in applications where it is important to shield an observer from light source glare. Referring to Fig. 16, it is possible to use reflective coating 22 as a translucent coating. That is, the coating could be deposited on the reflector so as not to be totally opaque. Thus, the coating would have a certain light transmissivity.

While some light rays 33 are reflected and directed in predetermined directions, other light rays 35 may be transmitted through translucent coating band 34. Thus a controlled percentage of direct light leakage through the translucent coating could be used to provide lighting to specific locations.

While the invention has been disclosed with respect to a preferred embodiment thereof, it is not to be so limited as changes and modifications may be made which are in the full intended scope of the invention as defined by the appended claims. For example, while aluminum has been disclosed as a reflective coating medium, it should be expressly understood that any type of reflective coating substance may be used. In addition, while glass and plastic have been disclosed as the transparent medium for the reflector, it should be understood that any types of materials may be used. Similarly, while some geometric configurations of reflective coating deposited on the reflector have been disclosed it should be understood that any configuration of reflective coating on the reflector whether geometrically definable or not is within the full intended scope of the claims. In addition, while certain applications of the invention have been disclosed, it should be understood that this novel combination of reflective coating and prisms may be advantageously employed in any lighting situation. Similarly, while various shapes of reflectors such as parabolic reflectors have been disclosed in the application, it should be expressly understood that the invention may be advantageously employed with reflectors of any configuration such as square, elliptical, or even non geometrically describable reflectors.

The shape of the reflector is preferably determined by the lumen count procedure as is well known in the art. In addition, it should be noted that, as used in this application, the word "reflector" may also be interpreted to mean a lens or a refractor.

Claims (22)

1. A reflector for use in a luminaire comprising: a transparent medium configured in a predetermined shape including an inner surface directly receiving light rays from a light source, and an outer surface opposite to said inner surface; a plurality of prisms integral with said transparent medium; and a reflective coating on a portion of said inner and/or said outer surface, said portion being less than the entire inner or outer surface.

2. Reflector according to Claim 1 wherein said transparent medium includes plastic.

3. Reflector according to Claim 1 wherein said transparent medium includes glass.

4. Reflector according to Claim 1 wherein said predetermined shape is determined by the lumen count procedure.

5. Reflector according to Claim 1 wherein said outer surface includes said pnsms.

6. Reflector according to Claim 1 wherein said inner surface includes said prisms.

7. Reflector according to Claim 1 wherein said reflective coating is selected from a group consisting of aluminum, silver, chromium, platinum and/or nickel.

8. Reflector according to Claim 1 wherein said reflective coating includes a circular band perpendicular to the axis of said transparent medium.

9. Reflector according to Claim 1 wherein said reflective coating includes at least one band parallel with the axis of said transparent medium.

10. Reflector according to Claim 1 wherein said reflective coating includes a horizontal band on said transparent medium.

11. Reflector according to Claim 1 wherein said reflective coating includes a vertical band on said transparent medium.

12. Apparatus according to Claim 4 wherein said predetermined shape is substantially elliptical.

13. Reflector according to Claim 4 wherein said predetermined shape is substantially para bolic in vertical cross section.

14. Reflector according to Claim 4 wherein said predetermined shape is substantially square in vertical cross section.

15. Reflector according to Claim 4 wherein said predetermined shape is substantially non geometrically describable in vertical cross section.

16. Reflector according to Claim 4 wherein said predetermined shape is substantially semi-circular in vertical cross section.

17. A reflector for use in a luminaire comprising: a transparent medium configured in a predetermined shape having an inner surface adjacent a light source and an outer surface,; a plurality of refractive prisms integral with said transparent medium; a plurality of reflective prisms integral with said transparent medium; and a reflective coating on a portion of said inner and/or said outer surface, said portion being less than the entire area of said inner and outer surface.

18. A reflector according to Claim 17 wherein said predetermined shape is substantially parabolic.

19. A reflector according to Claim 18 wherein said reflective coating includes a circular band perpendicular to the axis of said substantially parabolic medium.

20. A reflector according to Claim 18 wherein said reflective coating includes at least one vertical band parallel with the axis of said substantially parabolic medium.

21. A reflector according to Claim 17 wherein said portion of said surface area which is coated is a closed geometric configuration.

22. A reflector for use in a luminaire comprising: a transparent medium configured in a predetermined shape having an inner surface adjacent a light source and an outer surface; a plurality of prisms integral with said transparent medium; and a translucent coating on at least a portion of said inner and/or said outer surface.