Patent Publication Number: US-6337946-B1

Title: Optical light pipes with laser light appearance

Description:
This application is a divisional of application Ser. No. 09/457,911, U.S. Pat. No. 6,160,948 filed Dec. 8, 1999 which is a divisional of application Ser. No. 09/197,014, U.S. Pat. No. 6,031,958 filed Nov. 20, 1998, which is a continuation in part of and claims priority to PCT US98/09897 filed May 19, 1998, which claims priority of U.S. Provisional Patent Application No. 60/047,238 filed May 21, 1997. 
    
    
     FIELD OF THE INVENTION 
     The field of the invention relates to optical light pipes and more specifically to optical light pipes that give the appearance of a laser beam being emitted axially within the light pipe. These light pipes also provide highly efficient radial and axial distribution of light. 
     BACKGROUND OF THE INVENTION 
     There have been several different types of optical light pipes developed in the past. In general, these prior art light pipes either emit light out of the end of the light pipe or emit light across the entire surface of the light pipe. 
     Orcutt, U.S. Pat. No. 4,422,719, discloses a light pipe with a translucent coating over a core material which allows the light which is transmitted axially to be dispersed radially around the light pipe. This translucent layer causes multiple random reflections which causes the entire width of the light pipe to be illuminated. 
     In U.S. Pat. No. 4,466,697, by Daniel, another type of construction of light pipe is disclosed. This light pipe consists of an extruded material and deposited within that material are co-extruded reflective particles. These particles randomly reflect the light and again as in Orcutt, there is no pattern to the light distribution. The light emitted from this prior art light pipe is also totally random and consequently the entire light pipe is illuminated. 
     In U.S. Pat. No. 4,195,907, Zamja, et al., there is disclosed an extruded optical fiber which contains dispersed air bubbles co-extruded within the fiber. These air bubbles inherently have a different index of refraction than that of the surrounding material thus they provide reflective surfaces similar to what is attained in Daniel with his reflective particles. Zamja&#39;s light pipe, as in Daniel, utilizes reflective surfaces that are randomly aligned and are not oriented in any manner. Because of the random orientation of the reflective surfaces, the reflection of the light transmitted axially down the fiber is also random and consequently the entire fiber is illuminated. 
     In U.S. Pat. No. 3,535,018, Vasilatos, there is disclosed an optical fiber which has notches cut into the fiber in order to provide reflective surfaces. These notches are positioned in a random manner and consequently there is no orientation of the emitted light coming from the fiber. Again, as in Daniel and Zamja, this causes the entire fiber to be illuminated across its entire width. 
     U.S. Pat. No. 5,671,306 describes a lighting structure for intensely illuminating a narrow linear region through a longitudinal slit in a lightguide. The lightguide has a reflective internal surface and a lens mounted in a slit shaped aperture. The lens includes a plurality of parallel planar prisms for directing light out of the lightguide, however, light is emitted only from the longitudinal slit in this device. Due to the planar construction of the parallel prisms the emitted light is in a single radial direction. 
     Considerable prior art may be seen in several U.S. patents to Whitehead, starting with U.S. Pat. No. 4,260,220. There are several design features which repeat in the Whitehead prior art. In Whitehead&#39;s light pipes, the light pipes are primarily designed to efficiently transmit light down the light pipe with minimal losses. This is achieved by constructing a light pipe from a sheet of material containing prismatic surfaces which are aligned parallel to the axis of the light pipe. These features reflect and redirect the axially transmitted light by explotation of the principal of total internal reflection. Whitehead describes these prismatic surfaces as being in octature due to their construction consisting of a series of 90 degree prism faces which face each other. The light pipes in Whitehead go to great lengths to achieve near 100% efficient transmission of the axially transmitted light. In order to achieve this the prismatic elements are designed to reflect as much light as possible and not to redirect axially directed light from the light source to be redirected out to the sides. Because of the controlled orientation of the prisms and the controlled manner in which the light is axially directed down the light pipe, there is a plane of light that is visible to an observer. This plane of light appears as a very narrow line of light much smaller than the width of the prismatic surfaces of the light pipe. Because this narrow, very intense plane of emitted light is visible to the observer, this light appears as if it is a highly collimated axially transmitted beam of light from the light source. Due to the curvature of the prismatic surfaces, only this plane of light which appears to be at the center of the light pipe is apparent to the observer. This gives the observer the impression that the light from the light pipe is emitted axially within the light pipe, not radially from the surface, as is actually the case. It is this phenomenon that gives the invention the appearance of a laser beam transmitted through a medium inside the light pipe. The uniform intensity and width of this line of light is an indicator of the optical efficiency of the light pipe in distributing light radially along its length. 
     SUMMARY OF THE INVENTION 
     A simulated laser light system according to the invention consists of an optical light pipe which emits light rays in a substantially radial direction. These light rays are emitted perpendicular to a tangent of the curved prismatic surface of the light pipe. In addition, these emitted light rays lie in a plane formed by the incident light ray and the normal to the prismatic surface of the light pipe. The emitted light from the light pipe appears to an observer to be a beam of highly collimated light emitted axially down the light pipe. This apparent co-axial beam of light located within the light pipe is created by a combination of physical optical effects and an optical illusion. The optical effects consist of the reflection and refraction of light rays originating from an axially located light source which emits substantially parallel light rays axially down the light pipe. These light rays are redirected by prismatic surfaces radially outward in a plane which is defined by the incident light ray and the normal to the prismatic surface of the light pipe. The prismatic surfaces redirect the light rays by a combination of reflection and refraction of the light rays within the specially constructed light pipe. The emitted light rays are uniform in all radial directions although they may vary in intensity and direction along the length of the light pipe. Due to the radially and transmit it, as in my invention. In U.S. Pat. No. 5,481,637, Whitehead discloses a light source reflector for a diffuse light source located within another light pipe. This reflector is constructed with prismatic surfaces aligned perpendicular to both the axis of the light pipe and the axis of the light source, but as in his other designs, the prismatic surfaces are utilized for efficient reflection within the light pipe not transmission of the light radially out of the light pipe. In addition, in U.S. Pat. No. 5,481,637 the prismatic reflector surrounds a diffuse light source which is a fluorescent type light source. The purpose of the prismatic reflector is to reflect the diffuse light rays from the light source light down the axis of the light pipe and prevent any radial emission of light. As before, the prismatic surfaces are in octature in order to efficiently reflect the light and prevent any light from passing radially through the prismatic surfaces of the light pipe. 
     In all of the Whitehead prior art no reference is made to the appearance of the light emitted from the light pipe. Whitehead is primarily concerned just with the efficient axial transportation of light not it&#39;s distribution or appearance to a observer. 
     Another prior art device described in U.S. Pat. No. 4,906,070 to Cobb, Jr. incorporates prismatic features utilizing prismatic films. These devices utilize prismatic films contained in a box, tube, or other housing in order to support and orient the film. 
     The prior art devices whether they are described as optical fibers, light pipes, lighting structures, or luminaries are generally designed to emit diffuse light across the entire width of the emitting area of the device. This diffuse, non-oriented emitted light results in the entire width of the emitting area being illuminated when viewed by an observer. Other prior art devices are designed to transmit light down a tube without emitting light from the sides of the tube. 
     Prior art manufacturing methods such as machining or sandblasting features in optical elements, results in surfaces that create diffuse emitted light and do not achieve highly efficient, specular, radial emission of light. 
     The present invention, on the other hand, consists of an optical light pipe with oriented prism surfaces which provide specular emission of light. These prism surfaces are oriented generally perpendicular to the axis of the light pipe. These prism surfaces act in conjunction with another media, with a different index of refraction such as air, to cause the emitted light always appearing to be centered in the light pipe regardless of the observers location, the observer interprets this as the visible light originating from the center of the light pipe. This is an optical illusion due to the observer having binocular vision and incorrectly interpreting what he sees. In actuality the visible light is emitted from the surface of the light pipe. 
     The simulated laser light system light pipe, hereinafter referred to as SLLS, relies on an optical characteristic where the incident ray, the reflected ray, the refracted ray and the normal to the surface all lie in the same plane. In my SLLS, the light rays emitted from a light source are transmitted in a generally axial direction along the optical center line of a prismatic element. When these light rays strike the prismatic surfaces which posses a different index of refraction than the adjacent material, the light rays are both reflected and refracted. In all cases, either refraction or reflection, the light rays remain in the same plane as the incident light rays and the normal to the surface of the prismatic element. When the light rays finally emerge from the prismatic element, they emerge in a direction which is perpendicular to the tangent of the surface of the prismatic element. Despite being reflected and refracted the light rays still lie in the same plane as the incident ray, reflected rays and the refracted rays. It is this property that gives the SLLS its unique characteristic appearance of a laser beam traveling inside a rod or tube. For proper operation, the reflection and refraction inside the prismatic element should be specular, i.e., nondiffuse, otherwise, the emitted light rays will not have the characteristic appearance of a laser beam. If specular reflection and refraction is not maintained, multiple uncontrolled reflections and refractions will occur and the emitted light rays will not lie in the same plane as the incident rays. When this occurs, the emergent light rays will not have the appearance of a laser beam, i.e., a coherent highly collimated line of very intense light. Random orientation of the emitted light from the prismatic element will illuminate its entire width and thus it will not have the appearance of light emitted axially down the light pipe, rather, it will have the appearance of a neon or flourescent light. In addition, the radial and axial light distribution efficiency will be diminished over the specular case. 
     The term “SLLS” as used herein refers to an optical light pipe with integral prismatic surfaces oriented substantially perpendicular to a longitudinal axis of the optical light pipe and having a light source with an optical centerline which is generally parallel to the longitudinal axis of the optical light pipe. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in greater detail with reference to the preferred embodiments illustrated in the accompanying drawings, in which like elements bear like reference numerals, and wherein: 
     FIG. 1 is a side view partially in cross section of a hollow tube simulated laser light system (SLLS); 
     FIG. 2 is side view of a solid rod SLLS; 
     FIG. 3 is a side view of a light source illustrating a cone of emitted light rays emanating from the light source; 
     FIG. 4 is a cross sectional side view of a hollow tube SLLS illustrating the nomenclature used for defining the prismatic surfaces; 
     FIG. 5 is a side view of a solid rod SLLS rod illustrating the nomenclature used for defining the prismatic surfaces; 
     FIG. 6 is an optical system with the light source located in an optically dense medium, illustrating a light ray undergoing reflection and refraction; 
     FIG. 7 is an optical system with the light source located in an optically less dense medium, illustrating a light ray undergoing reflection and refraction; 
     FIG. 8 is a cross sectional side view of a solid rod SLLS illustrating the light rays originating from the light source and their subsequent reflection, refraction and emission from the SLLS; 
     FIG. 9A is a cross sectional side view of an SLLS tubular assembly; 
     FIG. 9B is a schematic cross sectional side view of an SLLS tubular assembly illustrating how the figures will be drawn in this patent application in order to clarify the illustrations; 
     FIG. 10A is a cross sectional side view of an SLLS illustrating several different light ray paths, with light originating from a light source at one end of a prismatic element and a reflective end portion; 
     FIG. 10B is a cross sectional side view of the SLLS of FIG.  1 OA without the optional reflective end portion; 
     FIGS. 11A,  11 B, and  11 C are cross sectional side views of a portion of an SLLS prismatic element and the different light path scenarios corresponding to three different incident angles of light directed down the axis of the prismatic element; 
     FIG. 12 is a perspective view partially in cross section of a tubular SLLS prismatic element illustrating the light rays emerging from the surface of the prismatic element and a plane that is defined by the incident light rays and a line tangent to the surface of the prismatic element; 
     FIG. 13 is a perspective view of a planar prism array and the light emitted from the planar prism array; 
     FIG. 14A is a perspective view of a prior art light pipe and its corresponding appearance to outside observers; 
     FIG. 14B is a perspective view of the SLLS and its corresponding appearance to outside observers; 
     FIGS. 15A,  15 B, and  15 C are graphs illustrating three different characteristic curves of spatial light distribution versus relative intensity for three different light sources; 
     FIGS. 16A,  16 B,  16 C, and  16 D illustrate four different SLLS assemblies which utilize three different light source types and one different end configuration of the prismatic element; 
     FIGS. 17A,  17 B, and  17 C are side views of three different light source configurations for an SLLS assembly, FIG. 17A has a single light source located at one end, FIG. 17B has a single light source located at one end and has a retroreflective element located at the opposite end, and FIG. 17C has two light sources, one located at each end; 
     FIG. 18A is a side view of an SLLS assembly consisting of a prismatic tubular element, a light source at one end, and an optional reflecting element at the opposite end from the light source; 
     FIG. 18B is a side view of an SLLS assembly consisting of a prismatic tubular element, a single light source located at one end, and a retroreflective element located at the opposite end from the light source; 
     FIG. 18C is a side view of a tapered prismatic tube SLLS having a single light source located at the opposite end from the narrowest portion of the taper; 
     FIG. 18D is a side view of a prismatic tube SLLS with a light source located at each end; 
     FIG. 19A is a side view of a SLLS prismatic element array; 
     FIG. 19B is a partial cross sectional view of the SLLS prismatic element array shown in FIG. 19A, illustrating a single light source emitting light rays into two of the four prismatic assemblies; 
     FIG. 20A is a top view of an SLLS prismatic element array forming an alphanumeric display; 
     FIG. 20B is a top view of an SLLS prismatic element array which forms an alpha-numeric display manufactured from sheets of planar material; 
     FIGS. 21A,  21 B, and  21 C are side cross sectional views of alternate embodiments of an SLLS prismatic element; 
     FIG. 22 is a side cross sectional view of the SLLS of FIG. 21C illustrating the optical light path of an SLLS assembly with a tapered inner core and a light source located at one end; 
     FIGS. 23A and 23B illustrate a manufacturing method which can be utilized to manufacture an SLLS prismatic element; 
     FIG. 24A illustrates another manufacturing method that can be used to manufacture a prismatic element by forming the prismatic element in a female mold; 
     FIG. 24B illustrates an optional covering for the prismatic element manufactured in FIG. 24A; 
     FIGS. 25A,  25 B, and  25 C illustrate manufacturing steps for manufacturing an elastomeric prismatic element with internal prismatic surfaces; 
     FIGS. 26A,  26 B, and  26 C illustrate another manufacturing process for creating an elastomeric prismatic element with internal prismatic surfaces; 
     FIG. 27A illustrates another manufacturing method for manufacturing a prismatic element with internal prismatic surfaces; 
     FIG. 27B illustrates an assembly of three of the prismatic elements shown in FIG. 27A, telescoped together to form a larger prismatic element; 
     FIGS. 28A and 28B are cross sectional side views of two solid rod SLLSs illustrating discontinuous prismatic features separated by optical conduit sections. 
     FIG. 29 is a cross sectional side view of a hollow rod SLLS illustrating discontinuous prismatic features separated by optical conduit sections; 
     FIG. 30 is a perspective view of a flexible solid rod SLLS with discontinuous prismatic features as in FIG. 28A; 
     FIG. 31 is a cross-sectional side view of an encapsulated semiconductor light source; 
     FIGS. 32A and 32B are cross-sectional side views of two encapsulated semiconductor light sources with integral prismatic SLLS light pipes; 
     FIG. 33 is a perspective view of an alternate embodiment SLLS prismatic light pipe with non-circular cross-section and prismatic surfaces which are oriented 90 degrees to each other; 
     FIG. 34A,  34 B,  34 C,  34 D and  34 E are cross sectional side views of five different embodiments of a SLLS light pipe with both visible light and infrared light sources; 
     FIG. 35 is a side view of a flashlight with an attached SLLS light pipe; 
     FIG. 36 is a side view of a miniature toy sword with a rod-like SLLS light pipe; 
     FIG. 37 is a side view of a writing instrument, such as a ball point pen, with an integral hollow SLLS light pipe; 
     FIG. 38 is a side view of a vehicle wheel such as a bicycle wheel with several SLLS attached; and 
     FIG. 39 is a top view of a toy application of a SLLS. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates in partial cross section, a first embodiment of a simulated laser light system (SLLS) according to the present invention. An SLLS assembly  9  includes a light source  1  and a prismatic element in the form of a tube. The prismatic element includes a wall  7  with an outer surface  3  and an inner prism surface  12 . The visible emitted light appears to be emitted from a center  5  of the prismatic element. A partial cross sectional portion of FIG. I illustrates the wall  7  and an inner optical material  4 . Also shown in FIG. 1 is the nomenclature that will be used to identify the important features of an SLLS. The outer diameter of the prismatic rod is identified with the letter D and the inner diameter of the prismatic rod is identified with the letter I. The width of the emitted visible light is identified with the letter E and the length of the prismatic tube is identified with the letter L. 
     FIG. 2 illustrates the components of an alternative embodiment of the SLLS utilizing a rod like prismatic element  29  and a light source  21 . The prismatic surfaces  27  are formed on the outside surface of the prismatic element. The light appears to be emitted from a center  25  of the prismatic element  29 . As in FIG. 1, also shown is the nomenclature that will be used to identify the features of an SLLS. The outer diameter of the prismatic rod is identified with the letter D, the width of the emitted visible light is identified with the letter E, and the length of the prismatic rod is identified with the letter L. 
     FIG. 3 illustrates a light source and its corresponding cone of emitted light, this is generally shown at  39 . The light source  31  emits light in a cone of emitted light at angle  37 . The half angle  33  of the cone of emitted light is measured from an optical centerline  35  of the light source. The light angle  37  is preferably an acute angle. Larger light angles may also be used, however, efficiently will suffer. 
     Various light sources can be successfully utilized in the invention such as an incandescent light, arc light, or solid state light sources such as light emitting diodes also known as a LEDS. Preferably, the light source  31  for use in the present invention emits a colored light, such as, red, green, or the like. The colored light source creates the appearance of a laser light with a diameter E which is less than an outer diameter D of the prismatic element. Preferably, the diameter E of the viewed light is less than one half of the diameter D of the prismatic element. Alternatively, the prismatic element may be tinted or colored and the light source may emit white light or another colored light. 
     FIG. 4 illustrates the nomenclature that will be utilized to describe additional features of a tube like SLLS. FIG. 4 shows an SLLS assembly  49  including a light source  41  and a prismatic element  42  having a series of prismatic surfaces  43 . The helix angle “a” of the prismatic surfaces is measured from the perpendicular to the optical center line. The helix angle “a” shown is approximately zero degrees. The pitch or spacing between the prismatic surfaces is identified as “P”. The height of the prismatic surfaces are identified as H. A retroreflective feature  45  is located at the end of the prismatic element  49 . 
     FIG. 5 illustrates the nomenclature that will be utilized to describe additional features of a rod like SLLS including a light source  51  and a prismatic element  52  having a series of prismatic surfaces  54 . The helix angle “a” of the prismatic surfaces  54  is measured from a line perpendicular to the optical center line  56 . This angle “a” is shown greater than zero degrees in the embodiment of FIG.  5 . The pitch or spacing between the prismatic surfaces is identified as “P”. The height of the prismatic surfaces are identified as H. A retroreflective feature  55  is located at the end of the prismatic element  52 . 
     The retroreflective elements  45 ,  55  illustrated in FIGS. 4 and 5 reflect the light rays back into the prismatic elements. The retroreflective elements may also be omitted to produce a SLLS which emits a column of light out an end of the prismatic element increasing the simulated laser appearance of the device. 
     FIG. 6 shows a reflective and refractive optical system including a light source  61  located in an optically dense medium  62 . The normal to the surface of the optically dense medium  62  is shown at  63 . An emitting surface is shown at  64 . The incident ray is shown at  65 . The emergent refracted ray is shown at  66 . The internally reflected ray is shown at  67 . An additional prismatic surface is shown at  68 . As can be seen in FIG. 6, incident light ray  65 , is both refracted and reflected when it passes from optically dense medium into a less optically dense medium  69  having a lower index of refraction than the optically dense material  62 . The angle of the incident light ray  65  with respect to the normal line  65  is identified with the letter E 1 . The angle of the emergent ray  66  is identified with the letter E 2 . As is well understood, the angle E 2  may be calculated by applying the standard formulas for geometrical optics. These formulas may be found in “Basic Optics and Optical Instruments, Revised Edition” 1997, Published by Dover Publications, Inc. Mineola, N.Y. which is incorporated herein by reference. As can be seen in FIG. 6, the emergent light ray  66  is refracted away from the normal to the surface  63 . FIGS. 6 and 7 illustrate an optical principal used in the present invention, this principal is that the incident light ray  65 , the reflected ray  67 , and the normal  63  all lie in the same plane, i.e., the plane of the drawing. This phenomenon is utilized in the present invention. 
     FIG. 7 illustrates another optical system in which a light source  71  is located in an optically less dense medium  79 . The optically dense medium  72  abuts the optically less dense medium and the normal to the surface of the optically dense material is shown at  73 . The emergent surface is identified at  74  and the incident light ray is shown at  75 . The refracted light ray is shown at  76  and the corresponding reflected ray is shown at  77 . An additional prismatic surface is identified at  18 . As in FIG. 6, the incident angle of the light ray is labeled E 1  and the angle of the refracted ray is labeled as E 2 . In contrast to the refracted light ray shown in FIG. 6, the refracted light ray of FIG. 7 identified at  76  is refracted towards the normal  73  rather than away from the normal as in FIG.  6 . In accordance with the law of reflection, the incident ray  75 , the reflected ray  77 , and the normal  73 , all lie in the same plane, i.e., the plane of the drawing. 
     FIG. 8 illustrates a cross sectional view of a rod type SLLS assembly  80 . The light source  81  is shown emitting light rays which undergo reflection and refraction and are eventually emitted from the SLLS. There are many different possible light paths shown, all of which will result in emitted light rays from the SLLS. This light emission can be the result of a single reflection and refraction event as shown with forward emitted light rays  82 ,  83 ,  84 , and  85 . The emitted light rays may have also undergone multiple reflections, such as that shown by light ray  90 , which finally emerges as light rays  86  and  88 . Additionally shown is light ray  87 , which is a reflected portion of light ray  90 . Another possible multiple reflection path is illustrated with light ray  91  which originates from light source  81  and is eventually emitted as light ray  92  after it is retroreflected due to surfaces  94  and  95 . As can be appreciated the included angle  98  between the prismatic surfaces  96  and  97  influences how many times the light rays of an SLLS are reflected prior to being emitted from the prismatic element. For a prismatic element having an index of refraction of 1.60 with a surrounding medium  89  of air with an index of refraction of 1.0, if the angle between the prism faces  98  is large, for example 140 degrees, the emitted light will consist of light rays that have only undergone a single reflection such as rays  82 ,  83 ,  84  and  85 . This will result in a highly directional viewing angle and the majority of the emitted light will be in a direction away from the light source. With the addition of a retroreflective feature such as that consisting of surfaces  94  and  95 , the light rays reflecting off the retroreflective surfaces can be reversed in direction relative to the optical centerline  100 , and reflected, refracted and finally emitted as shown at light ray  92 . This utilization of a light ray in combination with a retroreflective feature in this manner will have the effect of increasing the viewing angle of the SLLS. 
     FIG. 9A illustrates a hollow tube SLLS  102  with a light source  101 , a prismatic element  104  and a retroreflective end portion  103 . In order to clarify the drawings, some of the lines illustrating the features of the prismatic element will be omitted. Thus, the SLLS shown in FIG. 9A will be drawn as shown in FIG. 9B in order to facilitate illustrating the light ray paths within the prismatic element. 
     FIG. 9B illustrates the prismatic tube SLLS  106  of FIG. 9A including the prismatic tube  107 , the light source  111 , and the retro-reflective end portion  107 . 
     FIG. 10A illustrates some of the possible reflection and refraction events that will result in light being emitted from a hollow tube prismatic element SLLS  113 . The SLLS assembly  113  includes the light source  112 , a prismatic element  120 , and a reflective end portion  132 . Light ray  114  is a light ray originating from light source  112  which is reflected off a prismatic surface resulting in light rays  115  and  117 . After passing through the prismatic element, light ray  115  is emitted as shown as light ray  116 . The reflected ray  117 , originating from ray  114  is also refracted as shown as light ray  118 . Finally, this refracted ray  118  emerges from the surface of the prismatic element and is shown as ray  119 . Ray  124  is shown refracting through the prismatic element and emerging as ray  125 . Also shown is ray  127  originating from light source  112 . Ray  127  is refracted through reflective end portion  132 , reflects off surface  131 , is then additionally reflected off surface  130  and finally emerges from the surface of the prismatic element as emitted ray  135 . The optical axis of the SLLS is shown at  133 . 
     As discussed with reference to FIG. 8, if the SLLS is designed to utilize redirecting the light rays with a single refraction and/or a single reflection event, the emitted light will be highly directional. In other words, the emitted light will be highly oriented relative to the central optical axis of the SLLS. The emitted light will still lie in a plane defined by the incident light ray and the normal to the prismatic surface of the SLLS, but the emitted light rays will all be directed in the same direction relative to the central optical axis of the light pipe. This situation is acceptable when the observer&#39;s line of sight is always located at the same angle relative to the axis of the light pipe. But in situations where the observer is in varying locations relative to the axis of the light pipe, it is desirable to increase the viewing angling of the emitted light. It is possible to increase the viewing angle by several methods. 
     One method of increasing the viewing angle is to utilize the emitted light from two light sources located at opposite ends of the SLLS. See FIG. 18D which will be discussed later in detail. By utilizing light traveling in opposite directions in the SLLS and by designing the angle of the emergent light from the light pipe to be at an angle other than 90 degrees to the light pipe axis, it is possible to increase the viewing angle. The combination of the emitted light from two light sources interacting with the prismatic surfaces which emit light in a direction other than 90 degrees relative to the axis of the light pipe combine to give a wider viewing angle. The resultant viewing angle will be the combination of the two viewing angles created by the two light sources. The two light sources may either be two individual light sources or may be a single light source in combination with a reflective feature located at the opposite end of the light pipe. This reflective feature would be utilized to reflect light back down the light pipe in a direction opposite to the original direction. This is shown in FIGS. 8 and 10. This reflection and redirection back towards the original light source is defined as retroreflection. The reflective feature utilized for retroreflection may be a simple mirror, a reflective coating, or a retroreflective element which utilizes the principal of total internal reflection of light with appropriately angled transparent surfaces (see FIGS.  10 A and  18 A). A retroreflective element which utilizes the principal of total internal reflection is easily incorporated in the prismatic element itself as shown in FIGS. 4 and 5. It may be desirable to retroreflect the light rays slightly off axis of the incident light ray to achieve greater or lesser light output in a specific area of the light pipe. 
     FIG. 10B illustrates a hollow pipe SLLS without a retroreflective element on the end opposite the light source  112 . As shown in FIG. 10B, the some of the light rays are reflected, refracted, and emitted from the sides of the prismatic element  120  as light rays  116 ,  119 ,  121 , and  125  while light rays  127  and  128  which are substantially parallel to the center axes  133  of the prismatic element are emitted in a beam from the end of the prismatic element. In this manner the prismatic element acts as a filter to extract non-parallel light rays. The remaining substantially parallel light rays form a highly collimated beam emitted from the end of the prismatic element. 
     Another method of increasing the viewing angle is to cause multiple reflections within the prismatic element in order to increase the variation in the incident angles of the light rays striking the prismatic surfaces. The effect of varying the light ray incident angles on the direction of the emitted light rays is shown in FIGS. 11A,  11 B, and  11 C. FIG. 11A illustrates a portion of a prismatic element with optical center line  148 , incident ray  141 . Incident ray  141  is shown having multiple optical paths. The wall of the prismatic element is also a reflective surface at  146 . As is shown in the FIG. 11A, a portion of ray  141  is reflected and is shown as ray  147 . Ray  147  is farther refracted and reflected, finally emerging as rays  144  and  145 . Shown in FIG. 11A is an incident light ray  141  with an angle relative to the optical centerline  148  of approximately 45 degrees. From this single incident light ray, four different light rays with four different emergent angles are generated. These four differently directed light rays are shown at  142 ,  143 ,  144  and  145 . In addition to increasing the viewing angle with the large number of reflection and refraction ever its shown in FIG. 11A, the quality of the specular nature of emitted light maybe sacrificed. The reason for the degradation in the specular nature of the emitted light is due to slight imperfections in the construction of the prismatic surfaces and the degree of transparency of the materials used in the construction of the prismatic element  149 . The result of these multiple reflections and refractions is not only to broaden the viewing angle but it may also act to broaden the apparent width of the emitted light from the prismatic element. 
     Shown in FIG. 11B is the resulting reflections, refractions and ultimate emergence of light rays which originate from a incident light ray  151 . Incident ray  151  is at an incident angle of approximately 20 degrees relative to the optical center line  158  of the prismatic element  150 . Incident ray  151  is reflected and emerges as ray  153 . Light ray  151  is also refracted and reflected and emerges as ray  152 . Light ray  151  is additionally refracted and then finally emerges as ray  154 . As can be seen in FIG. 11B, the number of reflection and refraction events which occur prior to the emergence of light rays  152 ,  153  and  154  is dramatically reduced from that shown in FIG.  11 A. The corresponding appearance of an SLLS utilizing light rays with this incident angle would be similar to that shown in FIG. 16B at  236 . 
     Shown in FIG. 11C is incident light ray  161  which is at an angle relative to the optical axis  168  of approximately 7 degrees. As can be seen in FIG. 11C, this incident ray results in two emitted rays  162  and  163 . As previously mentioned, the greater the number of reflection and refraction events that occur within the prismatic elements, the more diffuse, i.e. less specular is the emitted light and the less well defined is the apparent laser beam effect. Thus, the light ray in FIG. 11C would provide the most well defined apparent laser beam effect. FIGS. 11A,  11 B, and  11 C illustrate the multiple reflections and refractions that can occur in a prismatic element. What is important is that all of these multiple reflections and refraction all occur in the same plane. In FIGS. 11A,  11 B, and  11 C, despite multiple reflections and refractions, all of these light rays lie in the same plane. 
     As can be appreciated, the angle of any emitted light rays are not only determined by the incident angle of the incident light rays, but also are determined by the angle of the prismatic surfaces and the angle of the emergent surface relative to the optical axis. In addition to these factors, the angle of the emitted light ray is also influenced by the index of refraction of the materials used in the prismatic element and the index of refraction of the surrounding medium. The intensity of any given emergent light ray will be governed by how many times it is reflected, refracted and essentially divided into two or more light rays. Thus, the intensity of the emergent light rays  162  and  163  shown in FIG. 11C would be greater than either of those shown in FIG.  11 A. The intensity of a light ray will decrease due to absorption losses in the material making up the prismatic element. The intensity of the emitted light rays will also decrease with the increasing number of reflections occurring within the light pipe. prior to being emitted. Because of these factors, the brightest most well defined simulated laser light appearance is obtained with light ray angles which are small relative to the optical axis of the light source, similar to those shown in FIG.  11 C. 
     FIG. 12 illustrates how the incident light rays and the emitted light rays of an SLLS can all lie in the same plane. Shown in FIG. 12 is a partial cross section of a circular prismatic element  171 , with an optical center line  185 . A group of incident light rays is shown generally at  170  and a group of emitted light rays is shown generally at  186 . The incident light rays  170 , enter the circular prismatic element and strike the internal prismatic surfaces  180  and are reflected and refracted and finally emitted as shown at  186 . These incident rays, the reflected and refracted rays (not shown) and finally the emitted light rays all lie in the same plane which includes the centerline  185 . This plane is shown with dashed lines at  173 . To an outside observer, the light rays in this plane appear as a single line of light, shown at  183 . Emergent light rays  186  are from the surface of the prismatic element  179  perpendicular to a tangent to the surface of the tube. This tangent to the surface of the prismatic element is shown at  175 . It is not apparent to an observer that the light rays are actually coming from the surface of the prismatic element, to the contrary, to the observer, they appear to be coming from the center of the prismatic element itself. The cross section of the circular prismatic element is shown at  180 . A point on the visible line of light apparent to an observer is shown at  181 . Plane  173  passes through the optical center line  185  and a point on the visible line  181 . As previously stated the incident light rays  170 , the refracted light rays (not shown) and the emitted light rays  186  all lie in the same plane shown at  173 . The optical centerline  185  also lies in this same plane  173 ; 
     The curvature of the prismatic element of the SLLS is partially responsible for its unique appearance. As the radius of curvature of the prismatic element is increased the width of the beam of visible light is also increased. Conversely, when the radius of curvature is decreased the width of the beam of visible light is also decreased. FIG. 13 illustrates what occurs when light rays strike a prismatic element which is flat or planar rather than curved. In FIG. 13, the planar prismatic element  195  is shown in partial cross section at  193 . Incident light rays shown generally at  190  strike the prismatic surfaces on the planar prismatic element and are reflected and refracted and finally emitted as light rays shown generally at  196 . As can be seen in the FIG., the emitted light rays are emitted across the entire width of the prismatic planar element. Thus to an outside observer, the entire width of the plane would be illuminated and there would not be a well defined area of intense light as with an SLLS. 
     FIG. 14A illustrates a prior art light pipe  200  and its appearance to a pair of outside observers. The outside observers are shown at  201  and  203 . The emitted light rays are generally shown at  202  and  204 . Observers  201  and  203  both observe that the entire width or diameter of the light pipe  200  is illuminated. The appearance of this prior art light pipe is similar to a neon or flourescent light with diffuse light being emitted from the entire diameter of the light. 
     FIG. 14B illustrates an SLLS  205  according to the present invention. As in FIG. 14A, there are two observers  206 ,  208 . The emitted light rays from the SLLS are shown at  207  and  209  and the corresponding visible lines of light are shown at  211  and  210 . As shown in FIG. 14B, observer  206  would only see illuminated line of light  211  which is directed perpendicular to the tangent in his direction. Observer  208  would see a different illuminated line of light shown as  210  and he would not be able to see the line of light  211  that observer  206  sees. Observer  206  would only see light rays shown generally at  207  forming illuminated line of light  211 . Observer  208  would only be able to see light rays  209  and the corresponding formed line of light  210 . Thus, in summary, an observer of an SLLS will only be able to see the light rays that are directed towards them along a plane that is perpendicular to the tangent to the surface of the SLLS which is nearest to them. The light visible to each observer is similar to a laser light projected into a partially reflective medium, such as smoke. 
     FIGS. 15A,  15 B, and  15 C show three different relative luminous intensity versus spatial radiation patterns for three different light sources. As previously mentioned, the light distribution pattern of a light source has a pronounced effect on the appearance of an SLLS. 
     In practice, the cone of light emitted from a light source can be described in many different ways but the most useful method to characterize the light source and its corresponding light cone angle is by measuring its light output versus angular displacement. This information is usually available for LED type light sources directly from the manufacturer. This information is typically presented in a graphical format of relative luminous intensity versus spatial distribution (angular displacement). Three of these types of curves are shown in FIGS. 15A,  15 B, and  15 C. The curves in FIG. 15A,  15 B, and  15 C are for LED&#39;s (light emitting diodes) but could also be for any type of light source, combined reflector or lens focusing system. The curves in FIGS. 15A,  15 B, and  15 C illustrate the variety of spatial distribution curves possible. In order to construct an SLLS with a very sharply defined laser beam appearance, a light source with a spatial distribution curve as shown in FIG. 15A could be utilized. When this light source is combined with the appropriately sized cylindrical prismatic element, a very sharply defined laser beam appearance will be obtained. Extremely small SLLS may be constructed with a light source which acts as a point source such as an LED or laser diode. For uniform appearance and light output from the SLLS, the light source and its corresponding optical centerline should be located on the prismatic elements optical centerline. 
     According to an alternative embodiment of the invention, the light source may be located off of the optical centerline of the prismatic element, however, uniform intensity around the SLLS will suffer. The light source may also be located outside of the prismatic element. For uniform intensity an external light source located outside of the prismatic element should be a ring of light positioned around the prismatic element. When a light source with the spatial light distribution curve shown in FIG. 15A is utilized with a prismatic element with a 70 degree included angle between its faces, an outer diameter of 0.200 inches, and a length of 6 inches, it would emit light with the appearance of that shown in FIG. 16D at  238 . The width of the beam of the emitted light, is approximately 0.030 inches. Prismatic element  228  shown in FIG. 16D also incorporates a retroreflective end portion  232  which adds to the intensity of the emitted light rays at the end of the prismatic element opposite the light source. 
     FIG. 15A illustrates a light source which has a very narrow and well defined cone angle. A light source with this type of light distribution profile is especially useful in the present invention. Line  215  on the graph of FIG. 15A characterizes the spatial light emission of the light source. This particular graph depicts a light source with 50 percent of its intensity at a 7 degree cone half angle. In other words, the point where the light output diminishes to 50 percent of its relative intensity, corresponds to a cone half angle of 7 degrees. Thus, the light cone angle as shown in FIG. 3 at  37 , is two times this or 15 degrees. This light cone half angle is defined as the angle from the optical centerline where the relative light intensity drops to 50% of its highest value. 
     FIG. 15B also illustrates another relative luminous intensity versus cone angle for another light source. In this particular graph, there is seen a characteristic dip in the curve, centered about the optical axis centerline. This dip in the curve is shown at  218 . A light source with a light output curve such as this can be obtained with an LED or the combination of a light source and reflector. For example, if a light source is located at a point other than the focal point of a parabolic or elliptical reflector, a light distribution curve such as the one in FIG. 15B can be obtained. Using a light source such as this, with diminished light output along the centerline of the optical axis of the prismatic tube, will diminish the amount of light that is able to be transmitted towards the end of the prismatic element. As can be appreciated, if this reduction in light output along the axis of the tube is taken to an extreme, then any type of retroreflective feature at the end of the prismatic tube would not be useful. FIG. 15B illustrates a light source with a relative luminous intensity that decreases to 50 percent at a light cone angle of 2 times 20 or 40 degrees. Thus, for example, if a light source with an angular displacement curve such as that shown in FIG. 15B is utilized for an SLLS, the appearance of the light emitted from the prismatic element would be similar to that illustrated in FIG. 16A, the light pipe shown generally at  225 . The light emitted from prismatic element  225  is shown in the shaded area at  235  and can be seen to be very broad at the base which corresponds to the location of the light source, (not shown). 
     In FIG. 15C a light source is shown with a 50 percent relative luminous output over a cone angle of 125 degrees. A light source such as this in combination with a prismatic element of the present invention would result in a very broad beam of visible light located at the end of the SLLS adjacent to the light source. This would also be a very short visible beam. As explained earlier, a very sharply defined intense simulated laser beam appearance is best obtained with a light source with a narrow light cone angle. Thus, a light source with a light distribution curve such as the one illustrated in FIG. 15C would not give good results. In order to achieve the SLLS effect, a light source with the light output characteristics similar to that of FIG. 15A should be utilized. 
     Shown in FIG. 16 are four different configurations of SLLS. The first three configurations FIGS. 16A,  16 B, and  16 C utilize the same type of prismatic element but utilize light sources with different light cone angles. The prismatic elements for all three of these configurations are identified at  225 . The visible light produced from the three different SLLS assemblies is identified at  235 ,  236 , and  237 . The length of the visible light is identified with the letter “T” and the diameter of the prismatic element is identified with the letter “D”. The SLLS shown in FIG. 16A utilizes a light source with the largest light cone angle. This large light cone angle results in a wide area of visible light that is short in length. The visible emitted light shown at  236 , in FIG. 16B, is longer because the transmitted light of this particular SLLS has a more narrow light cone angle for a given light output, thus, it has a longer visible length. Shown in FIG. 16C, at  237  is yet again a longer visible light area with a narrower base. Shown in FIG. 16D is an SLLS which consists of a prismatic element  228  similar to the ones utilized in the SLLS assemblies of FIGS. 16A,  16 B and  16 C but it is longer in length and also contains a retroreflective element  232 . As can be seen in FIG. 16D, the visible light area  238  is the longest of all of the SLLS shown in FIGS. This long length of visible emitted light is achieved by utilizing the light source used in FIG.  16 C and incorporating retroreflective element  232 . Thus, the entire length L of the prismatic element is illuminated to width E. 
     There are endless possible configurations of SLLS incorporating one or more light sources or a single light source with one or more prismatic elements with or without reflective end features. FIGS. 17,  18 ,  19 , and  20  illustrate several of the many different configurations that are possible. As can be appreciated these are only a few of the possible configurations and do not limit the possible configurations. 
     Shown in FIG. 17A is an SLLS  240  consisting of a single light source  241  and a prismatic element  242 . Prismatic element  242  is shown as a rod like structure with external helical prismatic surfaces. Shown in FIG. 17B is an SLLS  245  similar to that shown in  17 A, with a light source  243 , prismatic element  246  and retroreflective end portion  244 . 
     Shown in FIG. 17C is an SLLS  247  consisting of two light sources  248 ,  249  and a prismatic element  250 . The light sources  248 ,  249  in this particular embodiment can emit the same wavelength of light, in other words, the same color, or the two light sources  248  and  249  can emit light of differing colors. When the light sources are of differing colors, then the colors will actually blend along the length of the SLLS. This will result in two different colors of emitted light at each end of the SLLS and a blend of these two colors along the length of the SLLS. However, the light of a particular color would be most intense at the end adjacent to the light source. For example, the colored light emitted from  249  and redirected by prismatic element  250  would be most intense adjacent to light source  249 . An example of the mixing of the colored light is, if light source  248  is red and light source  249  is blue, the mixed color in the middle of the prismatic element would be purple. 
     In. FIG. 18A, an SLLS  260  includes a light source  261 , tubular prismatic element  264 , and optional reflective surface  262 . Reflective surface  262  can consist of a material such as plastic covered with a reflective metallic coating to act as a mirror. Thus reflective surface  262  acts as a retroreflective surface which redirects light rays back towards the light source  261 . 
     Shown in FIG. 18B is another embodiment of an SLLS  265 . As in FIG. 18A, the prismatic element  268  is a tubular type element with a hollow core. The light source  266  is located at one end of the prismatic element with a retroreflective end feature  267  located at the opposite end. Retroreflective end feature  267  consists of a conical end surface which utilizes the principal of total internal reflection in order to reflect light rays back towards the light source. Using this principal it is possible to obtain a more uniform emitted light from the end of the SLLS opposite the light source. 
     Shown in FIG. 18C is yet again another embodiment of an SLLS  270  including a light source  271  and a tapered prismatic tubular element  274 . The purpose of this tapered prismatic element is to obtain a more uniform light along the SLLS length. By utilizing a tapered prismatic element  274  it is possible to capture a higher concentration of light at the end of the SLLS, opposite the light source  271 . 
     Shown in FIG. 18D is another alternate embodiment of SLLS  275  including light sources  276 ,  277 . As previously discussed with respect to FIG. 17C, these light sources  276 ,  277  can be of either the same wavelength and color or differing wavelength and differing color. 
     Shown in FIG. 19A is a top view of an SLLS  280  including a prismatic element array illuminated by a single light source. This light source is not shown in FIG.  19 A. The individual prismatic elements are shown at  281 ,  282 ,  283  and  284 . A reflector assembly with reflective faces is shown generally at  285 . This reflector assembly directs the light from a single light source to all of the prismatic element in the array. Two of the reflective surfaces are shown at  288  and  289 . Surfaces  288  and  289  utilize the principal of total internal reflection to create their reflective behavior. 
     Shown in FIG. 19B is a partial cross section of the SLLS array shown in FIG.  19 A. The light source  286  emits light rays  278  and  279  and reflective faces  288  and  289  direct light rays  278  and  279  so that they strike prismatic elements  282  and  284 . Light ray  279  reflects off reflective surface  288  into prismatic element  284 . Additionally, light ray  278 , emitted from light source  286 , reflects off surface  289  and is directed into prismatic element  282 . As shown in this FIG. the light source itself need not be on the optical centerline of the prismatic element. 
     A unique characteristic of an SLLS is the ability of the visible light to be viewed with equal intensity from all angles. In other words the appearance of the intense line of light is visible at all positions around the SLLS. This unique property can be exploited in any type of lighted display. One such type of display which can utilize this property is shown in FIG.  20 A. FIG. 20A shows an array of SLLS elements arranged as an alphanumeric display. The array is generally shown in FIG. 20A at  290 . A typical SLLS used in the construction of the array is shown at  295 . A display such as this would not suffer from poor visibility at off axis viewing angles, as is the case with liquid crystal displays and discrete LED displays. 
     Shown in FIG. 20B is another embodiment of an alphanumeric display  297  composed of several SLLS. This alpha-numeric display array is constructed using prismatic elements fabricated in a different manner than that of FIG.  20 A. Instead of the individual prismatic elements as shown in FIG. 20A the prismatic element array of FIG. 20B utilizes prismatic elements molded in a planar sheet of material. One of these prismatic elements of top sheet  299  is shown at  301 . An integral light source for prismatic area  301  is shown at  302 . The top surface sheet is shown at  299  with the bottom surface sheet shown at  300 . Light source  302  may be sandwiched between the two prismatic sheets of material  299  and  300  thus completing the SLLS array. These sheets may be injection or blow molded with the prismatic surfaces integral to the sheet. As can be appreciated, these sheets can be injection molded with the prismatic surfaces on the inside or outside surface but the prismatic surfaces are more easily protected from dirt and abrasion if they are on the inside surface of the sheet. The light sources and associated wiring can be incorporated between the sheets with cavities created therein for the light sources. Top sheet  299  and bottom sheet  300  may be joined together using conventional methods and the alphanumeric display completed. As previously mentioned the viewing angle is very large, almost 180 degrees. 
     Utilizing a LED for a light source is especially desirable for the invention due to a LED&#39;s small size, high luminous efficacy and availability in various emitted colors and spatial light distribution patterns. LEDs may be constructed with an integral SLLS light pipe at time of manufacture. This is accomplished by molding the SLLS prismatic features into the plastic encapsulate used to protect the semiconductor die. LED prior art utilizes lenses, reflectors, and optical fibers to orient light emitted from the semiconductor die. These prior art devices focus light emitted from the semiconductor die in a direction generally perpendicular to the planar surface of the semiconductor die. Examples of the prior art can be seen in U.S. Pat. Nos. 4,753,520; 5,289,082; 5,742,120; 4,703,219; 5,592,578; and 4,433,898. These prior art devices do not radially distribute the light emitted from the semi conductor die. Instead these devices focus or reflect the light about the central axis of the die in a cone-like pattern. 
     Individual LEDs may be clustered or oriented in groups in order to act as a sign or display. Examples of this may be seen in U.S. Pat. Nos.: 4,914,731; 3,954,534; 4,467,193; 5,660,461; and 5,119,174. These prior art LED displays use LEDs oriented so that the optical axis of the LED is perpendicular to the surface which is viewed by an observer. In addition, a plurality of LEDs are utilized to illuminate one segment of the display. The invention utilizes LEDs with their optical axis parallel with the viewed surface. Because of the high optical efficiency of the invention a single LED may be used to illuminate an entire segment a sign or alpha numeric display. 
     FIG. 21A illustrates a cross section of a prismatic element  310  having prismatic faces located on the outside of the element and is a rod like structure. Shown in FIG. 21B is the prismatic element  310  of FIG. 21A with an optional covering shown at  316 . This optional covering has a different index of refraction from that of the underlying prismatic element of FIG. 21A for the purposes maintaining the prismatic characteristics. The index of refraction of  316  need only be different than that of the prismatic element shown in FIG.  21 A. It can be of an index of refraction that is greater or less than that used in element  310 . In the preferred embodiment the index of refraction or  316  is less than that of prismatic element  310 , as this will reduce the number of reflection and refraction events required to finally exit covering  316 . As previously mentioned an excess number of reflection and refraction events will cause a decrease in definition of the laser light effect and the light distribution efficiency of the SLLS. The purpose of this optional covering  316  is to protect the prismatic element  310  from dirt, debris and foreign objects. Because of the small nature of the prismatic surfaces, they are easily damaged when they are located on the outside surface of the prismatic element as shown in FIG.  21 A. When a prismatic element is covered with optional optical covering, this presents a smooth surface to the outside environment which is easily cleaned and protects the small delicate features of the prismatic element. 
     FIG. 21C is yet again another embodiment of a prismatic element  325 . The prismatic element  325  shown in FIG. 21C contains a tapered inner core shown at  328 . Prismatic element  325  is shown with outer prismatic surfaces similar to that shown in FIGS.  21 A and is covered with an optional covering  316 , such as that as shown in FIG.  21 B. This particular construction is unique in that a tapered inner core  328  is able to assist in transmitting light down to the far end of the prismatic element, opposite the light source (not shown). This effect is illustrated in FIG.  22 . 
     FIG. 22 shows a cross section of a prismatic element  330  with a tapered inner core  340 . The tapered inner core  340  has a different index of refraction than that of the outer prismatic portion  330 . The tapered inner core can either have a higher or a lower index of refraction depending on the optical characteristic desired. If the index of refraction of the outer portion  316  is of a lower value than prismatic element  325  then total internal reflection can occur at the various interfaces between the two materials. Total internal reflection is a highly efficient method of transporting light axially along the length of the element until the incident angle is less than the critical angle. As shown in FIG. 22 total internal reflection of light ray  332  is maintained until the emission of light ray  338 . If the index of refraction of element  330  is higher than that of the tapered inner core  340  then light rays will be emitted adjacent to the light source  331  as shown with light ray  335 . 
     Also shown in FIG. 22 is light source  331  shown emitting a single light ray  332 . Light ray  332  is split into a reflected ray  333  and a refracted ray  334 . Refracted ray  334  is emitted as ray  335 . Reflected ray  333  continues down the length of the tapered core  340  and with each successive reflection, its angle with respect to the normal of the inner surface of the inner core becomes closer to the normal. With each successive reflection the amount of reflected light versus refracted light decreases. In other words, as light ray  332  reflects down the tapered core of the prismatic element, the incident angle with respect to the normal becomes more normal and a greater portion of this reflective light is transmitted out the sides of the prismatic element. For example, light ray  332  is split into refractive ray  334  and reflective ray  333 . Reflected ray  333  continues down the tapered core and at each point a portion of it reflects and a portion of it refracts off the tapered inner core. A typical refracted ray is shown at  337  with corresponding emitted ray  338 . As seen in FIG. 22, with each successive reflection, the light rays traveling down the tapered core become closer to the normal of the surface of the tapered prismatic core. The light rays shown in area  341 , are essentially perpendicular to the surface of the tapered core and have little if any luminous intensity, due to the majority of the light from the light ray having already been emitted. 
     Shown in FIGS. 23A and 23B is a manufacturing method for making a prismatic element with internal prismatic surfaces. A hollow tubular prismatic element is actually a prismatic inner core composed of air surrounded by a outer layer of another material with differing index of refraction. For example, air has an index of refraction of 1.00 and a transparent plastic such as polymethylmethacrylate has an index of refraction of 1.49. Thus, the inner core has an index of refraction which is much less than the index of refraction of the outer layer. A basically equivalent prismatic element may be constructed using an inner core material with an index of refraction which is less than the outer layer as in the previously mentioned air core prismatic element. An example of this would be, an inner core composed of polytetrafluoroethylene with an index of refraction of 1.30 and an outer layer of polyurethane with an index of refraction of 1.66. This type of composite prismatic element is shown in FIG. 23B. A prismatic tubular element can be made by having a inner core material that has an index of refraction that is lower than the surrounding tube. For example, as shown in FIG. 23A is a transparent prismatic core  35  having the angled prismatic surfaces of the desired prismatic element. This core is inserted into an injection molding machine and then additional material  351  is injection molded around the core, resulting in a composite assembly as shown in FIG.  23 B. Injection molding core  350  becomes part of the prismatic element assembly. The composite tube assembly is shown generally at  352 . As mentioned previously, a hollow prismatic tube acts as a solid prismatic core with an outer covering with a greater index of refraction. The index of refraction of the outer covering  351  can be either greater or lesser than that of the inner core material  350 , depending on the included angle of prismatic surfaces and the optical effect desired. 
     FIGS. 24A and 24B illustrate another manufacturing method for fabricating a prismatic element with internal prismatic surfaces. FIG. 24A is a cross section of a mold  360  with inner prismatic molding surfaces for molding the prismatic elements on an outer surface of the tube  361 . Shown at  361  is an extruded tube or rod which enters the mold. The mold has a mold top half  362  and a mold bottom half  363 . This mold is heated and the extruded tube  361  or rod made of transparent plastic material is inserted into the mold. When mold halves  362  and  363  are closed on rod or tube  361 , prismatic surfaces are created in the rod or tube and this is shown generally at  365 . In the case of a tube, the molding process would be blow molding. In the case of a rod, it would be simple compression molding. This can be done on a continuous basis by heating the tube or rod, clamping the mold shut on the tube or rod, opening the mold, and transferring the material out of the mold and continuing. 
     Shown in FIG. 24B is a convoluted tube shown at  371  manufactured using the process shown in FIG.  24 A and covered with optional covering  372 . As previously mentioned, with external prismatic surfaces it may be desirable to have a outer covering or jacket covering the prismatic surfaces in order to protect them. Also as previously mentioned, the index refraction of this covering can be greater or lesser than the material of the inner prismatic surfaces. The convoluted tube  371  has air shown at  366  as the material on the inside of the tube. The convoluted tube  371  has internal and external prismatic surfaces. 
     FIGS. 25A,  25 B and  25 C illustrate a manufacturing method for forming an elastomeric prismatic element. Shown in FIG. 25A is an elastomeric transparent optical element  380  which has been molded inside out. The prismatic surfaces are initially on the outside of the tubular prismatic element  380 . FIG. 25B shows this element being to be turned inside out. FIG. 25C shows completion of the inversion of the elastomeric prismatic element  380  to form a tubular prismatic element  382  having prismatic surfaces which were originally manufactured on the outside of the prismatic element and are now inside of the element. Thus, high volume manufacturing methods which are utilized for injection molding prismatic surfaces on the outside of an element, may actually be used to create a prismatic element which has the prismatic surfaces ultimately on the inside. 
     In FIGS. 26A,  26 B, and  26 C another manufacturing method for an elastomeric prismatic element is shown. FIG. 26A shows an inner core pin  391  and an elastomeric element  390  injection molded around the core pin. In order to remove the elastomeric prismatic element  390  from the core pin air pressure is inserted into the hollow core pin a first end  394 . The air is able to exit the core pin at a second end  395 . By increasing the air pressure within the core pin  391  the prismatic element  390  is actually inflated, enlarging its inside diameter, thus it is able to be slipped off core pin  391  as shown in FIG.  26 C. 
     Another method for manufacturing a prismatic element with internal prismatic surfaces is shown in FIG.  27 A. FIG. 27A shows a partial cross section of a prismatic element which is constructed using injection molding with a tapered core pin. The core pin for injection molding is specially designed using a multistart helical type thread form which defines the prismatic surfaces. By utilizing a multistart helical thread, it is possible to injection mold the prismatic element around this threaded core pin and by unscrewing the core pin a few number of revolutions, remove the core pin. Prismatic surfaces due to their very fine spacing would normally require up to a hundred or more successive revolutions of a core pin to remove it from the prismatic element. By utilizing a multistart tapered helical core pin, it is possible to injection mold a prismatic element on this type of core pin and rotate the core pin, one, two or three turns and remove the core pin entirely. This is only possible by utilizing a multistart thread and the tapered prismatic surface. Despite the fact the actual helix angle of the prismatic surfaces is great, the pitch is very small because of the multistart aspect of the prismatic surface. Using this injection molding method can be very useful when constructing a fairly large prismatic hollow element. These large elements can then be telescoped together into successive sections to make a large prismatic element as shown in FIG.  27 B. 
     FIGS. 28A and 28B illustrate cross sectional views of rod type SLLS  500 A and  500 B having planar and curved prismatic surfaces. The SLLS  500 A and  500 B are similar to those shown in FIG.  8 . The SLLS  500 A and  500 B shown in FIGS. 28A and 28B incorporate non-prismatic portions  503  in order to reflect light rays emitted from light source,  501  further down the length of the SLLS. Features  503  act as totally internally reflecting (TIR) reflectors and allow longer length SLLS prismatic elements to be illuminated. These reflective portions  503  will not be intensely illuminated like the prismatic portions  504 . Total internal reflection will be achieved in sections  503  if the index of refraction of the prismatic material  509  is greater than the surrounding material  510  and the incident angle at the interface of the two materials is greater than the critical angle. Light ray  506  originating from light source  501  reflects off surface  507  in the non-prismatic section  503 , and is emitted as light ray  508 . Emitted light ray  505  is unaffected by reflective portions  503 . 
     FIG. 29 illustrates a cross section of a hollow type SLLS  530  with non-prismatic (reflective) portions  516  similar to those shown in FIG.  28 . As shown in FIG. 28, the purpose of the reflective portions  516  is to reflect a portion of the light emitted from light source  514  further down the length of the SLLS  530 . Light ray  520  is divided into light rays  521  and  523 . Light rays  521  and  523  eventually emerge from the SLLS as light rays  524 ,  525 , and  526 . As discussed above total internal reflection may occur at the various optical interfaces. Light ray  521  is shown undergoing total internal reflection at surface  519 , and then emerging as light ray  524 . 
     FIG. 30 illustrates a flexible embodiment of the SLLS shown in FIG.  28 . Shown in FIG. 30 is a portion of a SLLS manufactured as disclosed above with reference to FIGS. 24A and 24B. As shown in FIG. 30 the SLLS  550  includes prismatic portions  555  and reflective conduit portions  557 . FIG. 30 also illustrates the entire surface of portions  555  and  557  to be covered with an optional protective coating  553 . If the coating  553  is selected to have an index of refraction to be less than that of the rod material  552  then total internal reflection may be achieved at the reflective section  557 . Preferably, the prismatic features  555  are compression molded into the outer surface of the flexible SLLS  550  after the coating  553  is applied. Coating  553  may be co-extruded over flexible rod  552  and then the prismatic features generated in both materials simultaneously. 
     FIG. 31 is a cross sectional side view of a semiconductor light emitting diode encapsulated in an epoxy package. Devices  575  such as that shown in FIG. 31 are commonly known as LEDs. The light emitting semiconductor die or chip as it is also called is located in reflector  577  and is shown at  579 . Leads  571  and  570  supply electrical energy to the semiconductor die  579  which emits light which is focused by reflector  577  and lens  576  which is part of the LED protective epoxy enclosure or package. The optical axis of the light which is emitted from the LED is shown at  573 . 
     FIGS. 32A and 32B are cross sectional side views of two embodiments of the invention which consists of a SLLS prismatic element  610  which encapsulates the semiconductor die  601 , the reflector,  608  and leads. The prismatic surfaces, as shown in FIGS. 32A and 32B, may be planar or curved. As can be seen in FIGS. 32A and 32B, the light rays  611 ,  605 , and  613  are emitted from the die/reflector in a conventional manner but upon striking the outer prismatic surface  610  the light rays are directed radially away from the LED&#39;s optical axis. The SLLS prismatic elements shown include an optional conical reflective portion  620  with reflective surfaces  617  and  618 . The conical portion  620  should have a lower index of refraction than the element  610  if efficient reflection off the conical surface, shown at  617  and  618 , is desired. It is understood that the material used in conical section  620  can be air. If air is utilized in the conical section  620 , total internal reflection can occur at the surfaces shown at  617  and  618 . Maximum radial distribution of light over a short axial length will be obtained with the conic section acting as a total internal reflecting surface. As shown in FIGS. 32A and 32B, the light ray  605  is totally reflected off the surface  617  and is emitted as emergent light ray  606 . Also shown in FIGS. 32A and 32B is a portion of the light ray  613  emitted as the light ray  614  while another portion is reflected of the surface  617  and is emitted as the light ray  615 . As previously stated, utilizing a conic section made from a material with a lower index of refraction than prismatic element  610  combined with the proper acute angle will generate a surface which can provide total internal reflection at the surface. Total internal reflection generates near perfect reflection with almost 100% efficiency. 
     FIG. 33 illustrates in perspective view an alternate embodiment of the SLLS prismatic element shown in FIG. 32. A solid rod SLLS prismatic element having a non-circular cross section is shown generally at  630 . Element  630  utilizes prismatic features  634  which are perpendicular to the longitudinal axis  642  of the element  630  which is parallel to the light source optical axis (not shown). In addition, prismatic features  636  on an opposite side of the element  630  are oriented parallel to the light source optical axis, thus, perpendicular to the prismatic features  634 . The purpose of the prismatic features  636  is to prevent light from being emitted out surface  636  instead reflecting it onto surface  634 . This type of construction will result in additional light being emitted from surface  634  in the manner described with respect to the previous embodiments while little or no light is emitted from surface  636 . Prismatic surface  636  can be replaced with a smooth non-prismatic surface if desired. As can be appreciated other non-circular cross sections of a SLLS prismatic element are possible. As shown in FIG. 33 the prismatic element is elliptical in cross section. By using an elliptical cross section or other non-circular cross section the apparent diameter of the line of visible light  643  generated by the SLLS can be adjusted. The non-circular cross section of the SLLS prismatic element does reduce the 360 degree viewing capability to a lesser value. 
     FIGS. 34A through 34E are cross sectional side views of yet another use of a SLLS. FIGS. 34A through 34E utilize a combination of a visible light, light source shown in the figures at  710  and an infrared, non-visible light source shown at  701 . Visible light source  710  provides light for the simulated laser light effect while the infrared light source  701  is utilized to interact with an electronic device such as an infrared photo sensor. Infrared light sources also known as infrared emitters are used in television remote controls, video remote controls, and in toys such as laser tag. Since the human eye is not sensitive to infrared light it is difficult to determine where an infrared beam is pointed. By utilizing a SLLS in combination with an infrared light source the direction of the infrared beam can easily be determined by viewing the laser like line of light generated by the SLLS. 
     FIGS. 34A,  34 B and  34 D illustrate SLLS  703  with infrared light source  701  at a first end of the SLLS emitting infrared rays shown at  705 . 
     FIGS. 34C and 34E illustrate the infrared light source  701  emitting light ray  706  from a second end of the SLLS through the prismatic element and out the first end of the SLLS. 
     In FIG. 34A visible emitted light rays are shown at  711  and  712 . Visible light ray  713  is emitted through the transparent end cap  702  and assists in determining the direction of the infrared light rays shown at  705 . Electrical wires  708  and  709  for light source  701  pass through the hollow prismatic element of the SLLS shown in FIG.  34 A. Wires  708  and  709  are not visible from the outside of SLLS  703  due to the reflective characteristics of the prismatic surfaces. 
     FIG. 34B illustrates another embodiment combining a reflector  725  to reflect the light rays originating from light source  710  resulting in emitted light rays  714 ,  715  and  716 . 
     FIG. 34C illustrates a SLLS embodiment that provides a laser like line of light generated from light rays such as  717  and  718  but also filters out all nonparallel light rays including infrared light ray emitted as light ray  707 . This results in a well defined beam of both infrared and visible light. Visible light ray  719  aids in determining the direction of infrared light rays such as  706 . 
     FIG. 34D illustrates another SLLS embodiment which includes retroflective elements at both ends. Retroflective elements  726  reflect light rays such as  720  in order to allow them to emerge as shown with ray  721 . Light rays such as  721  and  722  generate the simulated laser light effect. No visible light rays are emitted from the ends of the SLLS in this embodiment. The retroreflective elements  726  each include an outer conical surface and an inner conical surface inverted within the outer conical surface. 
     FIG. 34E illustrates the utilization of back to back light sources  701  and  710 . Visible light source  710  reflects light off reflector  727  to cause light to be emitted from SLLS  703  such as light ray  723 . The reflectors utilized in FIGS. 34B,  34 D, and  34 E provide compensation for the short length of the SLLS, and the relatively small cone angle of light from the light source. The reflectors in  34 B,  34 D, and  34 E provide additional length for the light source cone of light to diverge inside the SLLS prismatic element. 
     As shown in FIG. 34A a hollow SLLS can accommodate electrical wiring or other objects inside the prismatic structure without severely degrading the optical performance. Since the light emitted from a SLLS emerges from the surface, the optical performance is only slightly compromised with the addition of small internal components. FIG. 34A illustrates electrical wiring for the infrared LED  701  passing through the hollow SLLS prismatic element. As discussed below, FIG. 37 shows an additional object inside a prismatic element. FIG. 37 shows a ball point pen cartridge mounted inside the hollow SLLS prismatic element  771 . 
     FIG. 35 is a partial cross section of a flashlight shown at  750  which incorporates a hollow molded prismatic element  751  with internal prismatic features shown at  752 . This element is similar to the one shown in FIG. 27A. A line of simulated laser like light is shown  753 . 
     FIG. 36 illustrates at  760 , a miniature toy sword with a blade constructed of a rod like SLLS prismatic element  761 . The simulated laser light generated by the SLLS is shown at  763 . 
     FIG. 37 is a partial cross section of a ball point pen shown at  770  which utilizes a hollow SLLS prismatic element  771  in conjunction with a light source  775 , to generate simulated laser light shown at  773 . The ball point pen ink cartridge  774  cannot be seen inside the SLLS prismatic element due to the prismatic surfaces. As previously stated the introduction of small objects inside a SLLS prismatic element only slightly compromises the optical performance and simulated line of laser light. 
     FIG. 38 illustrates a vehicle wheel shown generally at  780  which incorporates four radial SLLS  781 ,  782 ,  783 , and  784  and one circumferential SLLS  785 . 
     FIG. 39 shows an application for the present invention in which a toy spacecraft  450  utilizes SLLS elements  451  and  452  to simulate laser firing weapons. As shown in FIG. 39, both the radially emitted light  456  and axially emitted light  454  are utilized to enhance the realism and play value of this toy. 
     The SLLS is designed to provide a radially emitted light that is emitted perpendicular to a tangent to the surface of a prismatic element. Both reflection and refraction is utilized in order to efficiently achieve this orientation of transmitted light. In addition the two opposing prismatic surfaces of the SLLS act in unison with each other to each transmit light in a common plane. Because the prismatic surfaces of the SLLS are positioned opposite each other, around a common longitudinal axis, they are able to simultaneously reflect and refract light in a common plane. By utilizing this feature, the light reflected off the opposite inside surface of the prismatic element can be efficiently transmitted through the opposing surface of the prismatic element. By utilizing the reflected light in this manner the entire surface of the prismatic element may be utilized for light reflection, refraction and transmission. By utilizing all of the available surface area of the prismatic element in this manner a very wide viewing angle can be obtained. 
     In addition, due the emitted light originating from several different surfaces, the appearance of the line of radially emitted visible light is continuous and without any dark areas where no light is visible. In order to achieve the most laser like appearance of the emitted light, the prismatic surfaces should be very small and located very close together. In other words (referring to FIGS. 4 and 5) the pitch, P should be very small. For ease of manufacture the prismatic surfaces may be manufactured with a helix angle similar to a threaded fastener. In this case the helix angle should be small or otherwise the orientation of the visible light beam will be off axis. This off axis effect can be utilized to increase the width of the visible light beam if a retroreflective end feature or second light source is positioned at the opposite end of the prismatic element. In this case, because the light from the two light sources is in opposite directions to the helically inclined prismatic surfaces, the emitted light due to each light source is offset on opposite sides of the central axis of the prismatic element. These two offset visible beams of light appear as a single wider beam if the helix angle is not too severe. 
     
       
         
           
               
             
               
                   
               
               
                 The typical size of the prismatic surfaces are 
               
               
                 (again referring to FIGS. 4 and 5); 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Pitch, P 
                 .015 inches, 
                 (.36 mm) 
               
               
                   
                 Height, H 
                 .010 inches, 
                 (.26 mm) 
               
               
                   
                 Angle, A 
                 70 degrees 
               
               
                   
                   
               
            
           
         
       
     
     As can be appreciated the small size of the prismatic surfaces makes them very delicate and easily damaged. If a rugged or dirty operating environment is anticipated the prismatic element should be constructed with the prismatic surfaces on the inside rather than the outside surface of the element. The prismatic surfaces may be initially be formed on the outside surface and then subsequently covered with a protective layer of differing index of refraction material with equal results. With a smooth outer surface the prismatic element is more rugged and easily cleaned. Small prismatic elements may be readily injection molded by any the previously mentioned methods. Large prismatic elements lend themselves manufacturing methods which produce thin hollow tubular prismatic elements. 
     Although the invention has been illustrated as employing triangular or V-shaped prismatic surfaces and U-shaped prismatic surfaces, it should be understood that other prismatic surface shapes may also be used without departing from the invention. 
     Prismatic surfaces are surfaces which are capable of reflecting, refracting, and transmitting light in a generally radial direction wherein the incident ray, reflected ray, refracted ray, and emitted ray all lie in a common place passing through the central longitudinal axis of the prismatic element. In the special case of total internal reflection no refracted ray may exist for that particular, incident ray only a reflected ray. Depending on the angle of incidence of the light ray the prismatic surface may or may not act as an emitter for a particular light ray. Because of the large variability of the incident angles a SLLS prismatic surface is exposed to due to reflection from the opposite prismatic surface and the back reflections created at the two material interfaces the prismatic surfaces in an SLLS act as reflecting surfaces, refracting surfaces, and emitting surfaces. The shape of the prismatic surface may be either a planar surface, as shown in FIGS. 28A and 32A, or a complex curved surface, as shown in FIGS. 28B and 32B. In order to achieve light transmission efficiency and the SLLS effect the prismatic surfaces must be arranged symmetrically around a common longitudinal axis. As previously stated these surfaces may be planar surfaces or complex curved surfaces. As shown in the prismatic element-cross sectional view of FIG. 32A the included angle between the prismatic surfaces may by about 40 to about 100 degrees, preferably on the order of 70 degrees or as shown in the prismatic cross section of FIG. 32B the included angle between the prismatic surfaces may not be definable due to the curved shape of the surfaces. 
     The invention does not utilize sheets or segments of prismatic films; instead the prismatic features are integral with the light pipe itself. The light pipe is preferably monolithic or formed as a single piece without seams. However, the light pipe may include protective or other coatings. The design of the present invention allows easy manufacture by injection molding, casting, blow molding, thermoforming and other various high volume manufacturing methods. 
     The well defined, uniform appearance of the apparent laser light effect of the invention is in fact an indicator of its efficient axial and radial distribution of light. If the prismatic features of the invention are not properly fabricated, not only will the line of laser light effect be lost, but the light transmission efficiency will also suffer. The invention relies on specular, non-diffuse reflection and refraction in order to generate the apparent line of laser light and achieve high light distribution efficiency. Manufacturing processes such as molding can achieve the necessary surface finishes required on the prismatic surfaces. Mechanical fabrication methods such as conventional machining cannot achieve the necessary surface finishes required to fabricate an efficient SLLS. 
     The prior art devices neglect the reflection that occurs when a light ray enters a material with a different index of refraction from that which it was traveling. When light travels from one material to another a portion of that light ray is refracted into the second material and a portion is reflected back into the first material. The portion that is reflected back is dependent on several optical characteristics, such as the angle of incidence and the difference in index of refraction of the two materials. For example, if a light source is located in a material with an index of refraction of 1.3 and enters another material with an index of infraction of 1.0 considerable back reflection can occur. If the light ray is at an incident angle of 30 degrees, 10 percent of the incident light will be reflected back into the first material. If the incident angle is increased to approximately 45 degrees the amount of light reflected back into the first material is almost 50 percent. Prior art devices which utilize prismatic features all experience substantial back reflection, yet none of the prior art address what happens to this internally back reflected light. Incident angles of 45 degrees are common in prismatic structures, thus back reflection effects are common. By orienting the prismatic surfaces symmetrically around a common axis the invention is able to utilize this back reflection to increase the intensity of the emitted light out of the prismatic element. These back reflections provide additional variation in the angles of incident light acting on the prismatic surfaces. This variation in the incident ray angles results in a larger variation of light ray emergent angles, thus increasing the viewing angle of the emitted light. The prismatic surfaces in the invention function as reflective, refractive and transmissive surfaces. 
     The SLLS of the present invention may be used in many different toy and novelty applications. In addition, the SLLS may be used in light displays, Christmas tree lights, Christmas house light, signs, vehicle brake, signal, and dashboard lights, and laser pointers. 
     Modifications and variations of the present invention will be apparent to those having ordinary skill in the art having read the above teachings, and the present invention is thus limited only by the spirit and scope of the following claims.