Thin panel illuminator

Thin panel illuminator includes a solid transparent panel member having one or more deformed output regions which cause light entering the panel along an input edge thereof to be emitted along the length of the panel. Light may be transmitted to one or more panel input edges from one or more light sources utilizing transition devices which convert easily focused light generally to the shape of the panel input surfaces.

BACKGROUND OF THE INVENTION 
This invention relates generally, as indicated, to a thin panel illuminator 
including a solid transparent panel member for conducting light and 
extractor means for causing light conducted by the panel member to be 
emitted along the length thereof. 
Light panel illuminators are generally known. However, the present 
invention relates to several different panel illuminator configurations 
which are less expensive to make and/or provide for better control over 
the light output from the panel. Also, the present invention provides for 
more efficient transmission of light from a light source to the light 
emitting panel. 
SUMMARY OF THE INVENTION 
In one form of the invention disclosed herein, the panel illuminator 
includes a light emitting panel member made of a thin light conducting 
ribbon or film bent, cast or formed into a predetermined pattern to cause 
light conducted thereby to be emitted along the length thereof. The 
effective radius of the bends, the number of bends per unit length, the 
panel thickness, the index of refraction ratio, and the internal ray 
distribution may be controlled to control the panel light output and 
efficiency. 
In another form of the invention, the panel member comprises a solid 
transparent wave guide having a prismatic surface on one side to cause the 
light rays entering the wave guide through an input surface (end edge) to 
exceed the internal critical angle and be emitted. The size, shape and 
depth of the surface deformities may be varied along the length of the 
panel to produce a desired light output distribution. Also, a back 
reflector may be used to redirect emitted light back through the panel. 
Moreover, a second prismatic film may be placed in closely spaced relation 
to the panel prismatic surface to redirect the emitted light rays toward a 
particular application. 
In still another form of the invention, the panel member comprises a 
prismatic film having prism ridges running generally parallel to each 
other, with deformities along the tops of the prism ridges to cause light 
to be emitted. Also, diffuser surfaces, which may vary in depth and/or 
width, may be formed along the length of the prismatic surfaces. 
In each instance, the panels may be shaped to fit a particular application. 
Also, different light sources may be used to supply the panels with 
different types of radiation and reduce or eliminate others. 
Further in accordance with the invention, the panel input surfaces may be 
lens shaped or tapered to alter the input light ray distribution. Also, 
such panel input surfaces may be coated with an antireflective or other 
coating. 
In accordance with another aspect of the invention, a transition device is 
provided for converting easily focused light received from a light source 
to the shape of the panel input surface. In one form of the invention, the 
transition device includes an optical fiber transition member having a 
round or other shaped connector at one end to permit a source of light to 
be easily focused thereon, and a rectangular or other shaped connector at 
the other end corresponding in shape to the panel input surface. 
In another form of the invention, the transition device is made from a 
solid transparent material, and is provided with single or multiple input 
and output ends of a desired shape. Also, the input and/or output ends of 
the transition device may be lens shaped to spread the light evenly across 
such surfaces, and such surfaces may be coated to absorb or reflect 
certain frequencies of radiation. Moreover, more than one transition 
device may be used to transmit light from more than one light source to a 
single panel, and the panel may have one or more light output regions of 
various shapes to produce a desired light output distribution. 
To the accomplishment of the foregoing and related ends, the invention, 
then, comprises the features hereinafter fully described and particularly 
pointed out in the claims, the following description and the annexed 
drawings setting forth in detail certain illustrative embodiments of the 
invention, these being indicative, however, of but several of the various 
ways in which the principles of the invention may be employed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now in detail to the drawings, and initially to FIG. 1, there is 
schematically shown one form of thin panel illuminator in accordance with 
this invention including a solid transparent light emitting panel 2 and a 
light source 3 which generates and focuses light, in a predetermined 
pattern, either directly on a panel input edge 4 or on a transition device 
5 which is used to make the transition from the light source 3 target 
shape to the light emitting panel input edge 4 shape as shown. The light 
that is transmitted from the light source 3 to the light emitting panel 2 
may be emitted along the length of the panel as desired to produce a 
desired light output distribution to fit a particular application. 
A light source 3 of any suitable type may be used, including, for example, 
any of the types disclosed in copending application Ser. No. 125,323, 
filed Nov. 24, 1987, now U.S. Pat. No. 4,897,771, granted Jan. 30, 1990, 
and assigned to the same assignee as the present application, which is 
incorporated herein by reference. Light source 3 includes a radiation 
source 8 such as an arc lamp, an incandescent bulb, a lens end bulb, an 
LED or a fluorescent tube or the like, and may have a collector 9 which 
collects the light emitted by the radiation source 8 and uniformly focuses 
the light on the input end 10 of the transition device 5 with 
predetermined ray angles to fit a particular application. For the thin 
panel illuminator 1 of the present invention to operate efficiently, the 
light source 3, transition device 5 and light emitting panel 2 must be 
designed to fit each other as well as the particular application. However, 
it should be understood that the light source 3, transition device 5 and 
light emitting panel 2 may also be used separately if desired. 
Light emitting panel 2 comprises a solid transparent or translucent wave 
guide 15 made of glass, plastic or other suitable transparent or 
translucent material, with disruptions 16 on at least one side 17 formed 
as by cutting, molding, coating, forming or otherwise causing mechanical, 
chemical or other deformations in the exterior surface 18 thereof. When 
these disruptions 16 are struck by the light rays entering the panel input 
edge 4, they cause some of the light rays to exceed the internal critical 
angle and be emitted from the panel. The amount of light emitted from the 
panel will depend on the type, shape, depth and frequency of the 
disruptions 16. For example, if the exterior surface 18 is mechanically 
deformed at decreasingly spaced intervals as the distance from the light 
source 3 increases, there will be more uniform emission of light from the 
surface 18 when viewed from a distance. Also, such disruptions 16 may vary 
in depth and shape along the length of the panel 2 to produce a desired 
light output distribution. 
A back reflector 20 may be provided on the side 21 of the panel 2 opposite 
the side 17 with the disruptions 16 therein. In like manner, an end 
reflector 22 may be provided on the end edge 23 opposite the input edge 4 
to minimize the amount of light escaping from these surfaces. 
Another light emitting panel 24 in accordance with this invention is 
schematically shown in FIG. 2 and comprises a thin light conducting ribbon 
or film 25 bent into a wave form of predetermined pattern. Although the 
dimensions of the panel 24 may vary, as an example, the panel 24 may be 
approximately 0.020 inch thick and have an overall height of approximately 
0.040 inch, and be of any desired width or length depending on the 
particular application. Such a panel 24 may be made in any suitable 
manner, for example, by vacuum forming or injection molding. During the 
forming operation, the ribbon or film 25 is bent in a predetermined 
pattern, with the number of bends 26 per unit length, the effective bend 
radius, the panel thickness, the index of refraction ratio, and the 
internal ray distribution determining the light output and efficiency of 
the panel. 
When the wave guide 25 is bent, certain light rays that were previously 
internally reflected will be emitted if the bends are below a critical 
radius. The critical radius is the radius of curvature at which these 
light rays first start to be emitted. By making the bends 26 more or less 
pronouced, the percentage of light emitted can be controlled for a given 
input ray distribution. 
As schematically shown in FIG. 3, as certain light rays strike a bend 
surface 26 of panel 24, they exceed the internal critical angle and are 
emitted. If desired, one side of panel 24 may be provided with a back 
reflector 27 that reflects the light emitted from that side back through 
the panel towards an application as schematically shown in phantom lines 
in FIG. 3. Moreover, selected light emitting areas 28 of the panel 24 may 
be coated with a transparent coating 29 having a different refractive 
index than the light conducting ribbon or film 25 to cause changes in the 
attenuation of light being emitted from the panel 24 as further 
schematically shown in phantom lines in FIG. 3. 
FIG. 4 shows another form of light emitting panel 30 in accordance with 
this invention including a solid transparent wave guide 31 similar to the 
wave guide 15 of FIG. 1 but having a prismatic surface 32 on a side 33 
which is covered by a back reflector 34. Accordingly, when the prismatic 
surface 32 is struck by light rays entering an input end edge 35 of the 
wave guide 31, causing the light rays to exceed the internal critical 
angle and be emitted, the emitted light rays will be reflected back 
through the panel by the back reflector 34 and out the other side 36 of 
the panel as schematically shown in FIG. 4. The angles and/or depth of 
these prismatic surfaces 32 may be varied along the length of the panel 30 
to produce uniform or other desired light output from the other side 36 of 
the panel. 
In FIG. 4, the light rays are shown entering the panel 30 through an end 
edge 35 generally perpendicular to the prism edges 37. Also, an end 
reflector 38 is shown on the end edge 39 of the panel opposite the input 
end edge 35. However, if desired, light rays may be caused to enter the 
panel 30 from both end edges 35, 39, in which event the end reflector 38 
would be eliminated. 
FIG. 5 shows another form of light emitting panel 40 in accordance with 
this invention comprising a solid transparent prismatic film 41 having 
deformities 42 cut, molded or otherwise formed along the top of the prism 
edges 43. Although the deformities 42 are shown as being of a generally 
triangular shape, they may be of any desired shape that causes light to be 
emitted, and may vary in depth and shape along the length of the prism 
edges 43 to produce a desired light output distribution. In this 
embodiment, light rays are caused to enter the panel 40 from one or both 
side edges 44, 45 in a direction generally parallel to the prism edges 43. 
Alternatively, diffuser surfaces 46 may be formed along the top edges 47 of 
the prismatic surfaces 48 of a prismatic film light emitting panel 49 as 
schematically shown in FIG. 6. These diffuser surfaces 46 may vary in 
depth and/or width along the length of the panel 49, and may comprise a 
roughened surface, a lenticular surface, or a prismatic surface or the 
like that consists of multiple surface deformities. A roughened surface, 
for example, may be produced by grinding, sanding, laser cutting or 
milling. Also, both of the light emitting panels 40 and 49 shown in FIGS. 
5 and 6 may have prismatic surfaces on both the top and bottom surfaces 
rather than on just one surface as shown, and one or the other of the top 
or bottom surface may be provided with a back reflector similar to the 
back reflector 34 shown in FIG. 4 to redirect emitted light back through 
the panel toward a particular application. 
FIG. 7 schematically shows another form of light emitting panel 50 in 
accordance with this invention which also comprises a solid transparent 
prismatic film 51 having a prismatic surface 52 on one side and a back 
reflector 53 on the other side, similar to the light emitting panel 2 
shown in FIG. 1. Light rays may be caused to enter the panel 50 
perpendicular to the wave guide prism edges 54 from one or both end edges 
55, 56 of the panel, and are internally reflected until they strike a 
deformity (in this case an edge 54 of the panel prismatic surfaces 52) 
which causes the light rays to be emitted. The size, shape and depth of 
the wave guide deformities 52 may be varied along the length of the panel 
to produce a desired light output distribution. Also, a back reflector 53 
may be provided on the bottom side of the panel 50 to redirect light back 
through the panel. 
In addition, the panel 50 includes a second prismatic film 60 disposed in 
close proximity to the panel prismatic surface 52 to shift the angular 
emission of light toward a particular application. The second prismatic 
film 60 may be separated from the first prismatic film or wave guide 51 by 
air or an epoxy filled gap 61. If the wave guide 51 and second prismatic 
film 60 are epoxied together, the epoxy 61 must be transparent and have a 
suitable index of refraction. Also, multiple prismatic films may be used 
in place of the single prismatic film 60, or the prismatic film 60 may be 
replaced by a diffuser or lenticular lens or the like. 
Other examples of thin panel illuminators in accordance with this invention 
are schematically shown in FIGS. 8-10. The thin panel illuminator 61 shown 
in FIGS. 8 and 9 includes a light emitting panel 62 and transition device 
63 for transmitting light from a light source 64 focused on its input 
surface 65 to the panel input surface (end edge) 66. In this embodiment, 
the light emitting panel 62 comprises a laminated structure including a 
solid transparent wave guide 67 and extractor 68 joined together as by 
means of an adhesive layer 69 or the like. Light that enters the wave 
guide 67 from the transition device 63 is internally reflected until it 
strikes the wave guide-extractor interface 70 and is emitted from the 
extractor 68 toward a particular application. The index of refraction of 
the adhesive layer 69 may be varied relative to the indexes of refraction 
of the wave guide 67 and extractor 68 to produce a desired light output. 
If desired, the extractor 68 may be joined to the wave guide 67 by methods 
other than adhesive such as clamping, fastening, heat sealing and solvent 
gluing and the like. Also, the extractor 68 may consist of one or more 
coatings applied directly to selected areas of the top or bottom surfaces 
of the wave guide 67. These coatings may vary in frequency, index of 
refraction, color, and/or shape along the length of the panel 62. 
Reflectors 71 may also be provided at the end edge 72 of the wave guide 67 
opposite the input edge 66 as well as at the side edges to reflect light 
back into the wave guide. Also, a back reflector 73 may be provided on the 
bottom surface 74 of the wave guide to reflect light back through the wave 
guide. 
The thin panel illuminator 75 of FIG. 10 also includes a solid transparent 
light emitting panel 76, but which has multiple light output regions 77, 
78, 79 of various shapes, and multiple transition devices 80, 81 for 
transmitting light from multiple light sources 82, 83 to different panel 
input edges 84, 85. In the FIG. 10 embodiment, two such transition devices 
80, 81 are shown connected to two panel input edges 84, 85 which are 
substantially perpendicular to each other. The sides and back of the panel 
76 may have reflective coatings 86 thereon. 
Each output region 77-79 contains deformities 87 produced, for example, by 
molding, machining, stamping, etching, abrading, or laser cutting or the 
like to cause light to be emitted therefrom. The light output pattern or 
uniformity of light output from these output regions 77-79 may be 
controlled by varying the shape, depth and frequency of the deformities 87 
relative to the input light ray distribution. For example, the various 
light output regions 77-79 of the panel 76 may be etched, roughened or cut 
into different shapes and levels of deformities using a laser by varying 
the power, position and cutting speed of the laser. 
FIGS. 11-14 schematically illustrate solid transparent light emitting 
panels having differently shaped light output regions. FIG. 11 shows a 
panel 90 with light input at one end edge 91 only and typical light ray 
travel. In this embodiment, panel 90 has a back reflector 92 on the bottom 
surface 93, an end reflector 94 on the end edge 95 opposite the input end 
edge 91, and a deformed light output region 96 whose depth progressively 
decreases along the length of the panel from the input end edge 91 toward 
the opposite end edge 95. 
FIG. 12 shows a panel 100 with light input at opposite end edges 101 and 
102 and a deformed output region 103 that progressively decreases in depth 
from both input end edges 101, 102 toward the middle of the length of the 
panel. FIG. 13 shows a panel 104 with light input at one end edge 105 only 
and a deformed light output region 106 on the bottom surface 107 whose 
depth progressively decreases from the input end edge 105 toward the 
opposite end edge 108. Also, a back reflector 109 is shown mounted on the 
bottom surface 107 of the panel 108 to redirect the light that is emitted 
from the light output region 106 back through the panel and out the top 
surface 110. In this embodiment, either an air gap or a transparent fill 
material 111 having a suitable index of refraction may separate the back 
reflector 109 from the panel 104. 
Panel 115 shown in FIG. 14 is similar to panel 104 of FIG. 13 except that 
the back reflector 116 of FIG. 14 is deposited directly on the deformed 
light output region 117 and the depth of the panel is substantially 
uniform throughout its length. 
In each instance, the light input surfaces (end or side edges) of the light 
emitting panels may be lens shaped or tapered to alter the input light ray 
distribution. Also, such light input surfaces may be coated with an 
anti-reflective coating or a coating that changes the numerical aperture 
of the panel. The numerical aperture is the sine of the vertex angle of 
the largest cone of input rays that can enter an optical system or element 
multipled by the refractive index of the medium in which the vertex of the 
cone is located. Moreover, the light input surfaces, bottom surface and/or 
top surface of the panels may be coated to reflect or absorb certain 
frequencies of light. 
From the foregoing it will be apparent that the wave guide confines and 
directs light in a direction determined by its boundaries, whereas the 
extractor causes light to be emitted from the wave guide. Examples of wave 
guides that may be utilized in the thin panel illuminators of the present 
invention include glass sheets, plastic films, liquid filled transparent 
enclosures, and crystals and the like. Also, examples of extractors that 
may be utilized in the thin panel illuminators include prismatic films, 
diffusers, lenticular lenses, coatings and other systems or materials that 
cause the internal critical angle to be exceeded which in turn causes 
light to be emitted. 
Referring next to FIGS. 15-19, different forms of transition devices for 
use in transmitting light from a remote location to the light emitting 
panels of the present invention are shown. As previously indicated, the 
purpose of such transition devices is to transmit light focused on its 
input surface or surfaces to a light emitting panel by converting a 
relatively easily focused cross-sectional shape of light to the shape of 
the panel input surface. The transition device 120 shown in FIG. 15 
comprises a plurality of optical fibers 121 having a round or other shaped 
connector 122 at one end on which a source of light is easily focused and 
a rectangular or other shaped connector 123 at the other end substantially 
corresponding in shape to the panel input surface. The optic fibers 121 
may be made of glass or a suitable transparent plastic material, and may 
be formed into a ribbon-like cable 124 by loosely weaving cross (fill) 
threads 125 between the optical fibers 121 which act as a harness without 
causing the optical fibers to bend to the degree necessary to emit light 
from the transition device 120. Preferably, the optical fiber strands 121 
of both of the connectors 122, 123 are scrambled to produce a higher 
uniformity in the transition device output. Moreover, the ends of the 
connectors 122, 123 are desirably highly polished to minimize losses, and 
may be coated to reflect or absorb certain wavelengths of light. 
In lieu of using optical fibers in the transition device, the transition 
device may be made from a solid transparent material such as glass, 
plastic or the like having an input surface at one end of a 
cross-sectional shape on which a light source is easily focused such as 
round or square and having an output surface at the other end in the shape 
of the panel input surface. FIG. 16 shows one such solid transparent 
transition device 125 having a substantially square input surface 126 at 
one end and a substantially rectangular output surface 127 at the other 
end, whereas FIG. 17 shows another solid transparent transition device 130 
having a round input surface 131 at one end and a substantially 
rectangular output surface 132 at the other end. Also, FIG. 18 shows a 
solid transparent transition device 135 including multiple input (or 
output) surfaces 136 at one end and a single output (or input) surface 137 
at the other end. FIG. 19 shows another solid transparent transition 
device 140 with a lens 141 at the input surface 142 shaped to spread the 
light evenly across its output surface 143. In like manner, the output 
surface of the solid transition devices as well as the input surface of 
the light emitting panels may be lens shaped or tapered to alter the input 
light ray distribution. 
Although the respective input and output surfaces of the various transition 
devices are shown as square, round or rectangular, they may be elliptical 
or any other shape necessary to fit a particular application. Moreover, 
multiple light sources may be used with a single panel or multiple panels 
used with a single light source by providing the transition device with 
multiple input connectors leading to a single output connector or a single 
input connector leading to multiple output connectors as schematically 
shown in FIG. 18. Furthermore, filters may be placed between the light 
source and panel or transition device to reflect or absorb certain 
wavelengths of light. Also, a moving or rotating filter may be used to 
produce color effects. 
Although the various solid transparent transition devices are shown 
separate from the light emitting panels, it will be appreciated that such 
transition devices may be formed as an integral part of the panels. Also, 
in certain applications the transition devices may be eliminated and the 
light focused directly on the panel input surfaces to cut down on system 
losses. 
As will be apparent, the various thin panel illuminators disclosed herein 
may be used for a great many different applications, including for example 
general lighting, phototherapy treatment, and radiation curing of 
adhesives and epoxies and the like. Typical general lighting applications 
include back lighting of liquid crystal displays or transparencies or the 
like, task lighting, machine vision lighting, safety lighting for both 
commercial and industrial as well as automotive applications, 
explosion-proof lighting, underwater lighting, display lighting and 
infrared heating and the like. Phototherapy treatment includes such 
applications as tanning lights, phototherapy of neonatal 
hyperbilirubinemia, photochemotherapy, photosynthesis of plants, and so 
on. Also, radiation curing of adhesives and epoxies may be used in a wide 
variety of applications including aerospace, dental, circuit board, 
electronic component, and optical component manufacturing, to name a few. 
To facilitate use of such thin panel illuminators for phototherapy, the 
panels may be formed in the shape of a pad, belt, collar, blanket, strap 
or other suitable shape. FIG. 20 schematically illustrates a thin panel 
illuminator 145 in accordance with this invention being used for 
phototherapy treatment of infants including a solid transparent light 
emitting panel 146 in the shape of a pad and a light source 147 designed 
for example to emit sufficient radiation in spectral regions that lower 
plasma bilirubin levels. The light source 147 may also be designed to 
reduce output of infrared and ultraviolet radiation that may be harmful to 
the infant. In addition, such light source may be designed to provide 
sufficient illuminance and color rendering for inspection of an infant's 
skin color. A transition device 148 in accordance with this invention 
transmits the light from the light source 147 to the light emitting panel 
146 in the manner previously described. 
Although the light emitting panel 146 is shown in FIG. 20 as being flat, it 
will be appreciated that the panel may be curved or otherwise formed to 
emit light in a desired manner or on a particular location. FIG. 21 
schematically shows a light emitting panel 150 bent or formed to fit a 
particular application. Also, FIG. 22 shows another light emitting panel 
151 in accordance with this invention in the shape of a channel 152 having 
a bottom wall 153, spaced apart side walls 154 and an open top 155, with 
deformities 156 along the interior length of the bottom and side walls 
153, 154 to cause light to be emitted interiorly. The channel 152 may be 
curved or bent at 157 intermediate its length with the radius of curvature 
around which the light travels being sufficiently large that light is not 
emitted. Also, a reflective surface 158 may be applied to the exterior 
surfaces of the panel to redirect light interiorly back through the panel 
bottom and side walls 153, 154 toward a particular application. 
Although the invention has been shown and described with respect to certain 
preferred embodiments, it is obvious that equivalent alterations and 
modifications will occur to others skilled in the art upon the reading and 
understanding of the specification. The present invention includes all 
such equivalent alterations and modifications, and is limited only by the 
scope of the claims.