VWGoA - Ex. 1014
`Volkswagen Group of America, Inc., Petitioner
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`US. Patent
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`Nov. 24, 1992
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`Sheet 1 of 4
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`5,165,772
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`US. Patent
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`Nov. 24, 1992
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`7 Sheet20f4
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`5,165,772
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`US. Patent
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`Nov. 24, 1992
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`Sheet 3 of 4
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`5,165,772
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`US. Patent
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`Nov. 24, 1992
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`Sheet 4 of 4
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`5,165,772
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`VISUAL DISPLAY DEVICE
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`5,165,772
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`BACKGROUND OF THE INVENTION
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`1. Cross Reference to Related Application
`This application is related to copending US. patent
`application Ser. No. 07/725,216, filed Jun. 26, 1991,
`which is a continuation of US. patent application Ser.
`No. 07/357,512, filed May 25, 1989, by the present in-
`ventor. The related application is entitled “HIGH IN-
`TENSITY LIGHT DISPLAY DEVICE”.
`2. Field of the Invention
`The present invention generally relates to visual dis-
`plays, and more specifically to a visual display device
`which is especially suitable for automotive center-high-
`mounted stop-light (CHMSL) and brake light applica—
`tions.
`
`3. Description of the Related Art
`Red colored CHMSLs for automotive vehicles are
`becoming increasingly popular due to the greatly in-
`creased safety margin they provide. In addition to the
`conventional right and left mounted, red-colored rear
`brake lights, newer vehicles and retrofit packages for
`older vehicles are available which include the CHMSL
`in the form of a third brake light which is mounted near
`the top of the vehicle rear window. Depression of the
`vehicle brake pedal causes the CHMSL to be illumi-
`nated in combination with the two low mounted brake
`lights to form a triangle pattern with greatly enhanced
`visibility and ability to immediately attract the attention
`of the operator of a trailing vehicle. Statistics have
`already proven that CHMSLs have prevented numer-
`ous traffic accidents in situations requiring emergency
`braking under high speed, congested traffic conditions.
`A major problem which has persisted in providing a
`CHMSL on a conventional automotive vehicle is that
`existing devices generally include an opaque housing
`having a rear-facing translucent red panel with a white
`illuminating bulb inside the housing which is wired to
`the vehicle’s brake circuit. The opaque housing itself
`constitutes a safety hazard in that it blocks a portion of
`the view through the rear window which the vehicle
`operator must see via the rear-view mirror in order to
`monitor th:- proximity of other vehicles. The opaque
`housing or at least a light blocking member (which may
`be the reflector) behind the illuminating bulb and red
`panel is necessary to prevent the vehicle operator from
`confusing the CHMSL with a light from another vehi-
`cle.
`Conventional CHMSLs and brake lights including a
`white bulb, a large and bulky reflector and a red display
`panel which constitutes a red filter, are inefficient in
`that only the red component of light from the bulb is
`transmitted through the panel. All other colors or
`wavelengths of light are absorbed by the panel and
`thereby wasted. The result is that the intensity of the
`red light emitted by the device is considerably lower
`than the intensity of white light emitted by the bulb.
`The above referenced related application discloses a
`CHMSL including a linear red light source, and a dis-
`play panel having a first surface formed with optical
`quality, light reflecting grooves, which reflect and dis-
`perse light coupled from the light source into an edge of
`the display panel out a second surface of the panel
`which is opposite to the first surface. The display panel
`viewed from the first surface is transparent at all times.
`The display panel viewed from the second surface pro—
`duces a red light pattern reflected from the grooves
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`when the light source is turned on, and appears trans-
`parent when the light source is turned off.
`Although highly effective in many applications, the
`CHMSL of the related application is not suitable for
`mounting on an automobile rear window which is tilted
`downwardly from the horizontal by a small angle (less
`than approximately 20°), since the amount of light re-
`flected out through the second surface of the panel in
`the horizontal direction is unacceptably small.
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`SUMMARY OF THE INVENTION
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`A Visual display device embodying the present inven-
`tion is especially suitable for use as a central high
`mounted stoplight (CHMSL) for an automobile rear
`window which slants downwardly from the horizontal
`by a small angle. The device includes a linear light
`source which preferably emits red light.
`A display panel has a light receiving edge extending
`parallel and adjacent to the light source means and first
`and second opposing surfaces. The second surface
`slants toward the first surface in a direction away from
`the edge and is formed with steps having walls which
`are angled toward the edge such that the peak output
`light propagating through the display panel from the
`edge is refracted horizontally out of the display panel.
`Although in the basic form of the invention the first
`surface is flat, the first and/or second surfaces may be
`made concave to conform to the shape of a curved
`automobile rear window.
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`The walls of the steps are tilted or cut back toward
`the light receiving edge from the vertical by a small
`angle, which is on the same order as the angle by which
`the rear window is tilted or slanted downwardly from
`the horizontal. Thus, substantially all of the light which
`enters the edge of the display panel is usefully refracted
`horizontally out of the panel. Thus, the present display
`device is suitable for mounting as a CHMSL on the top
`of an automobile rear window with an arbitrarily small
`downward slant angle.
`The walls of the steps are formed with laterally
`spaced depressions for lateral dispersion of light. Where
`the linear light source is nearly collimated, the edge of
`the panel may be made concave to vertically diverge
`the light beam into the panel. Conversely, where the
`linear light source is a light emitting diode module or
`the like which produces a diverging light beam,
`the
`edge of the panel may be made convex to converge the
`light beam into the panel.
`The visual display device of the present invention is
`simple in structure, highly efficient, and inexpensive to
`manufacture on a commercial production basis. The
`display panel may conceivably be used individually as
`an element in other types of display devices. It has been
`determined experimentally that a display device of the
`present invention configured as a CHMSL including a
`suitable light source such as a light emitting diode mod-
`ule or high pressure neon discharge tube provides a red
`light display having an intensity substantially in excess
`of federal requirements.
`It will be understood that the present display device
`is not limited to use as a CHMSL, but can be advanta-
`geously employed in other applications in which a uni-
`form, linear light source is required.
`These and other features and advantages of the pres-
`ent invention will be apparent to those skilled in the art
`from the following detailed description, taken together
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`with the accompanying drawings, in which like refer-
`ence numerals refer to like parts.
`DESCRIPTION OF THE DRAWINGS
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`FIG. 1 is a perspective view of a visual display device
`embodying the present invention;
`FIG. 2 is a sectional view of the display device;
`FIG. 3 is a fragmentary sectional view, to enlarged
`scale, illustrating the operation of the display device;
`FIG. 4 is a diagram illustrating the geometry of the
`display device;
`FIG. 5 is a plan view illustrating lateral light dispers-
`ing depressions formed in walls of steps of a slanted
`surface of a display panel of the display device;
`FIG. 6 is a sectional view illustrating a modified
`display device embodying the present invention having
`a curved lower or upper mounting surface;
`FIG. 7 is a sectional view illustrating a modified
`display device embodying the present invention includ-
`ing a display panel having a light receiving edge with a
`convex cross-section; and
`FIG. 8 is a sectional view illustrating a modified
`display device embodying the present invention includ-
`ing a display panel having alight receiving edge with a
`concave cross-section.
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`DETAILED DESCRIPTION OF THE
`INVENTION
`
`FIGS. 1 and 2 illustrate a visual display device 10
`which may be advantageously employed as a CHMSL
`and includes a linear light source 12, and a display panel
`14 made of a light transmissive material such as glass or
`acrylic. Further illustrated are orthogonal X-, Y- and
`Z-axes or directions which are indicated by arrows and
`lines respectively.
`The light source 12 emits a linear light beam which is
`elongated in the Z-direction, and propagates from the
`light source 12 into the panel 14 in the X-direction. The
`light source 12 may include any suitable elements for
`emitting a linear light beam, such as a laser diode mod-
`ule, light emitting diode module, high pressure neon
`tubular discharge lamp,
`fiber optic array, etc. As
`shown, the light source 12 includes a linear light emit-
`ting element 12a, and an optional parabolic reflector 12b
`which reflects and forms light emitted by the element
`12a into a flat beam which enters a light receiving edge
`14a of the display panel 14. The reflector 12b is neces-
`sary only where the light emitting element 12a is tubu-
`lar. When the display device 10 is used as a CHMSL,
`the light source 12 emits red light.
`In the basic embodiment of the invention, the edge
`14a lies in the Y-Z plane and is perpendicular to a first
`surface 14b of the panel 14 which lies in the X-Z plane.
`The panel 14 further has a second surface 14c which
`opposes and slants or tapers toward the first surface 14b
`in a direction away from the edge 14a. More specifi-
`cally, the second surface 14c approaches the first sur-
`face 14b in the Y-direction as the distance from the edge
`14a in the X-direction increases. The second surface 14c
`is formed with a plurality of steps 14d having walls 14e
`which are elongated in the Z-direction. As illustrated
`more clearly in FIG. 3, the walls 14e are angled or cut
`back toward the edge 14a by an angle a].
`As viewed in FIGS. 2 and 3, the display device 10 is
`mounted on a surface 18 which is inclined (or equiva-
`lently slanted or tilted downwardly) by an angle 0 rela-
`tive to the horizontal as indicated by a line 20. The
`surface 18 is typically the rear window of an automo—
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`bile, with the first surface 14b of the display panel 14
`being flush therewith.
`The present display device is not limited to use as a
`CHMSL, but can be advantageously employed in other
`applications in which a uniform, linear light source is
`required. For example, the device 10 can be mounted
`vertically to illuminate a floor or desk from above. A
`desk lamp incorporating the device 10 is unique in that
`the display panel 14 is transparent and will not block the
`forward view of the user. The device 10 can also be
`used to illuminate signs at business and other establish-
`ments from below. As yet another application, the de-
`vice. 10 can be used as a movable linear spotlight for
`creating special effects in theatrical and film produc-
`trons.
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`illustrated as being
`Although the device 10 is
`mounted on top of the surface 18, it is also possible to
`mount the device 10 on the bottom of the surface 18
`using suitable hardware (not shown) with the first sur-
`face 14b of the panel 14 parallel to the surface 18. Al-
`though not specifically illustrated, a transparent cover
`or housing made of plastic or the like may be provided
`over the display device 10 for protection against accu-
`mulated dust, scratches, etc.
`The light source 12 emits the light beam into the edge
`14a of the panel 14 in the X-direction, parallel to the
`X-Z plane. The beam propagates through the panel 14
`and is contained therein by total internal reflection be-
`tween the surfaces 14b and 14c until it reaches the walls
`14e of the steps 14d. In accordance with the invention,
`the angle (11 of the walls 142 is selected as a predeter-
`mined function of 0 and the index of refraction m of the
`panel 14 such that the peak output light parallel to the
`X-direction is refracted out of the panel 14 through the
`walls 14a horizontally as indicated by arrows 22. This is
`accomplished by selecting the angle a1 such that the
`light is refracted out through the walls Me at the angle
`0 away from the first surface 14b.
`The light is refracted upwardly by the walls Me by
`the same angle 0 by which the first surface 14b is slanted
`downwardly from the horizontal 20. Thus, substantially
`all of the light which enters the edge 14a of the display
`panel 14 parallel to the X-direction is usefully refracted
`horizontally out of the panel 14. Thus, the present dis-
`play device 10 is suitable for mounting as a CHMSL on
`an automobile rear window with an arbitrarily small
`downward slant angle.
`When the light source 12 is not turned on, the panel
`14 is transparent when viewed through both surfaces.
`The panel 14 is transparent when viewed from the first
`surface 14b under all conditions. When the light source
`12 is turned on, the display panel 14 viewed from the
`second surface 14c produces red light, since the walls
`14e appear red due to the light refracted therethrough.
`The geometry of the display 12 is shown in FIG. 4.
`The plane of the illustrated wall 14e illustrated in the
`drawing is indicated by a line 24, whereas the normal to
`the wall 14e is indicated by a line 26. The angle between
`the line 24 and the Y-direction is (11, whereas the angle
`between the line 24 and the X-direction is designated as
`B, where B=(90°—a1). Since the lines 24 and 26 are
`perpendicular, the angles on and B relative to the line 26
`are complementary to their respective relationships to
`the line 24. More specifically, the angle between the line
`26 and the X-direction is (11 whereas the angle between
`the line 26 and the Y-direction is B.
`The angle al’between the line 26 and the X-direction
`is also the angle of incidence of the light beam on the
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`wall l4e. The angle of refraction of the light beam out
`through the wall l4e is designated as a2. For the light to
`be refracted out of the display panel 14 through the
`walls l4e in the horizontal direction 20 as indicated at
`22, a2=a1+0. By Snell’s law,
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`mein (a1)=nz><sin (a2)=n2><sin (a1+0)
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`where m is the index of refraction of air, with 112:1.
`Thus, the angle (11 is given as a function of 0 and m as
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`sin (a1+0)/ sin (a1)=m
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`(Equ. 1)
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`(Equ. 1) may be easily solved by iteration using a
`conventional digital computer. More specifically, the
`value of a1 is varied until the left side of (Equ. 1) equals
`the right side thereof.
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`The display panel 14 described thus far retracts light
`from a collimated light source out through the walls l4e
`horizontally, with essentially no lateral dispersion (in
`the Z-direction). Such a panel would produce a high
`intensity light display for an observer directly behind
`the panel, but a display with sharply decreasing inten-
`sity as the viewing angle increases. It is therefore desir-
`able to provide means for creating dispersion of re-
`flected light in the lateral direction.
`As illustrated in FIG. 5, the wall l4e of each step 14d
`is formed with a series of laterally spaced curved de-
`pressions 14}? which provide continuous variation in the
`lateral angle of the wall l4e and thereby the desired
`lateral dispersion of light refracted out of the display
`panel 14 through the walls l4e.
`The depressions 14f preferably have a cylindrical
`cross-section or profile as illustrated, although other
`shapes such as spherical or elliptical are within the
`scope of the invention. As viewed in FIG. 5, each de-
`pression 14f is defined by a partial cylindrical surface
`14g having an axis 14h which extends upwardly from
`the surface 14c parallel to the plane of the respective
`wall
`l4e. In order to provide further dispersion and
`better appearance, the depressions 14f formed in the
`walls l4e of alternating adjacent steps 14d are laterally
`displaced from each other by a distance W/2, where W
`is the width of each depression 14f
`Whereas the surface 14b of the display panel 14 of the
`display device 10 is flat, it is within the scope of the
`invention to form the display panel into a curved shape
`to conform to a surface on which it is mounted. As
`illustrated in FIG. 6, a display device 30 includes a
`linear light source 32 and a display panel 34 which is
`mounted on top of a downwardly curved surface 36
`such as an automobile rear window. The display panel
`34 has light receiving edge 34a and a curved first sur-
`face 34b which is concave about the Z-direction so as to
`conform to the surface 36. The panel 34 has a second
`surface 34c formed with steps 34d having walls 34a in an
`manner similar to the device 10.
`Due to the curvature of the panel 34, the angles al of
`the individual walls 34e may differ from each other.
`However, (Equ. l) is applicable to calculation of the
`angle a1 (and the complementary angle [3) for each wall
`34e. Although the panel 34 is illustrated as being con-
`cave about the Z-axis, it may also or alternatively be
`curved about the X-axis although not shown in the
`drawing. It is also within the scope of the invention to
`mount the display device on the bottom, rather than on
`top of a downwardly curved surface of an automobile
`rear window as indicated at 36’.
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`FIG. 7 illustrates another display device 40 embody—
`ing the invention, in which like elements are designated
`by the same reference numerals used in FIGS. 1 to 4,
`and similar but modified elements are designated by the
`same reference numerals primed. The device 40 in-
`cludes a linear light source 42 having a divergent light
`emitting element 420 such as a tubular discharge lamp,
`and a reflector 42b. Most of the light beam from the
`element 420 does not propagate straight from the light
`source 42 into a display panel 14', but diverges in the
`vertical direction.
`In order to channel the light into the panel 14' at a
`smaller aperture, a light receiving edge 140’ is made
`convex. The edge 14a’ thereby functions as a cylindrical
`converging lens which converges the light
`into the
`panel 14'.
`FIG. 8 illustrates another display device 50 embody-
`ing the invention, in which like elements are designated
`by the same reference numerals used in FIGS. 1 to 4,
`and similar but modified elements are designated by the
`same reference numerals double primed. The device 50
`includes a linear light source 52 having a collimated
`light emitting element 52a such as a laser diode module,
`and a housing 52b. The light beam from the element 52a
`propagates straight from the light source 52 into a dis-
`play panel 14”, but is collimated.
`In order to diverge the light into the panel 14", a light
`receiving edge 14a" is made concave. The edge 14a"
`thereby functions as a cylindrical diverging lens which
`diverges the light into the panel 14” to a desired extent.
`The principles of the embodiments of FIGS. 7 and 8
`may be applied to provide a specified amount of vertical
`dispersion or distribution of the light emitted from the
`display panel 14’ or 14” such as required by Federal
`standards. The vertical dispersion may be increased by
`making the light receiving edge of the panel concave
`(or less convex), and vice-versa.
`EXAMPLE
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`A CHMSL 10 was constructed as illustrated in FIGS.
`1 to 5. The display panel 14 was formed of acrylic plas-
`tic resin having an index of refraction 111:1.49, whereas
`the light source 12 was a red light emitting diode array.
`The dimensions of the panel 14 were 25 cm in the Z-
`direction and 6.5 cm in the X-direction. The height of
`the light receiving edge 14a (in the Y-direction) was 1
`cm. The panel 14 had ten steps 14d, with the height of
`the walls l4e each being 1 mm.
`The panel 14 was slanted from the horizontal by an
`angle 6 =13“. The angle (11 by which the walls 14e were
`cut back toward the edge 140 (also the angle of inci-
`dence of the light beam) was 26°, whereas the comple-
`mentary angle [3 was 66.4°. The angle of refraction a2
`was (a1+0)=33.6". The depressions 14f of the edges
`l4e had a radius of 2 cm and a width of 1 cm.
`The CHMSL 10 emitted light with the peak direction
`being horizontal, and horizontal and vertical dispersion
`in excess of Federal standards.
`While several illustrative embodiments of the inven-
`tion have been shown and described, numerous varia-
`tions and alternate embodiments will occur to those
`skilled in the art, without departing from the spirit and
`scope of the invention. Accordingly, it is intended that
`the present invention not be limited solely to the specifi-
`cally described illustrative embodiments. Various modi—
`fications are contemplated and can be made without
`departing from the spirit and scope of the invention as
`defined by the appended claims.
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`9. A display device as in claim 2, in which the first
`surface is substantially flat.
`10. A display device as in claim 2, in which the first
`surface is concave.
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`11. A display panel comprising:
`a light receiving edge; and
`first and second opposing surfaces;
`the second surface being formed with steps having
`walls which are angled toward said edge such that
`light propagating through the display panel from
`said edge is refracted out of the display panel
`through said walls in a direction at least partially
`away from the first surface.
`12. A display panel as in claim 11, in which the sec-
`ond surface slants toward the first surface in a direction
`away from said edge.
`13. A display panel as in claim 12, in which:
`the display panel is designed to be mounted with the
`second surface disposed above the first surface and
`said edge at an uppermost position such that the
`first surface is inclined relative to the horizontal by
`a predetermined angle; and
`said walls are angled toward said edge such that said
`light is refracted out of the display panel through
`said walls at substantially said predetermined angle
`relative to the first surface.
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`14. A display panel as in claim 12, in which said edge
`has a convex cross-section.
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`15. A display panel as in claim 12, in which said edge
`has a concave cross-section.
`16. A display panel as in claim 12, in which said walls
`are formed with a plurality of laterally spaced, curved
`light dispersing depressions.
`17. A display panel as in claim 16, in which:
`said depressions have a predetermined width; and
`said depressions of each wall are laterally offset from
`said depressions of adjacent walls by approxi-
`mately half the width of said depressions.
`18. A display panel as in claim 16, in which said de-
`pressions have substantially cylindrical shapes.
`19. A display panel as in claim 12, in which the first
`surface is substantially flat.
`20. A display panel as in claim 12, in which the first
`surface is concave.
`it
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`1. A visual display device comprising:
`light source means; and
`a display panel having a light receiving edge and first
`and second opposing surfaces extending away from
`said edge, said edge being positioned to be illumi-
`nated by said light‘source means;
`the second surface being formed with steps having
`walls which are angled toward said edge such that
`light propagating through the display panel from
`said edge is refracted out of the display panel
`through said walls in a direction at least partially
`away from the first surface.
`2. A display device as in claim 1, in which the second
`surface slants toward the first surface in'a direction
`away from said edge.
`3. A display device as in claim 2, in which:
`the display panel is designed to be mounted with the
`second surface disposed above the first surface and
`said edge at an uppermost position such that the
`first surface is inclined relative to the horizontal by
`a predetermined angle; and
`said walls are angled toward said edge such that said
`light is refracted out of the display panel through
`said walls at substantially said predetermined angle
`relative to the first surface.
`4. A display device as in claim 2, in which:
`said light source means comprises a divergent linear
`light source; and
`said edge has a convex cross-section.
`5. A display device as in claim 2, in which:
`said light source means comprises a non-divergent
`linear light source; and
`said edge has a concave cross-section.
`6. A display device as in claim 2, in which said walls
`are formed with a plurality of laterally spaced, curved
`light dispersing depressions.
`7. A display device as in claim 6, in which:
`said depressions have a predetermined width; and
`said depressions of each wall are laterally offset from
`said depressions of adjacent walls by approxi-
`mately half the width of said depressions.
`8. A display device as in claim 6, in which said de-
`pressions have substantially cylindrical shapes.
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