United States Patent [19]
`Farchmin et al.
`
`llllllllllllllllllllllllllllllll|I|||l|||llllllllllllllllllllllllllllllllll
`5,567,042
`Oct. 22, 1996
`
`US005567042A
`Patent Number:
`[11]
`[45] Date of Patent:
`
`[54] REFLECTOR FOR FLAT PANEL DISPLAY
`BACKLIGHT UNIT
`
`[75] Inventors: David W. Farchmin, Grafton; John S.
`Clark, Cudahy, both of Wis.
`
`[73] Assignee: Allen-Bradley Company, Inc.,
`Milwaukee, Wis.
`
`[21] Appl' NO‘: 250’131
`[22] Filed;
`May 27, 1994
`
`[51] Int. Cl.6 ...................................................... .. F21V 7/09
`[52] US. Cl. .......................... .. 362/241; 362/29; 362/224;
`_
`362/225; 362/297; 362/346
`Fleld Of Search ................................... ..
`362/237’ 241’ 245’ 247’ 260’ 297’ 346’
`347’ 348’ 217’ 29
`
`[56]
`
`.
`References cued
`U‘S‘ PATENT DOCUMENTS
`
`4,106,083
`4,425,604
`4,729,075
`
`8/1978 Wolff ..................................... _. 362/217
`1/1984 Imai et a1. .
`362/225
`3/1988 Brass ..................................... .. 362/217
`
`4,794,501 12/1988 Bartenbach ........................... .. 362/217
`4,947,305
`8/1990 Gunter, Jr.
`.. 362/297
`
`5,134,553
`
`7/1992 Hasegawa . . . . . . . .
`
`. . . . .. 362/225
`
`5,253,151 10/1993 Mepham et a1. ...................... .. 362/297
`
`FOREIGN PATENT DOCUMENTS
`
`442246A2 8/1991 European Pat. Off. ............. .. 362/297
`1011484 12/1965 United Kingdom ................. .. 362/217
`
`Primary Examiner—Denise L. Gromada
`Assistant Examiner—Alan B. Cariaso
`Attorney, Agent, or Firm—-Mark W. Pfeiffer; John D. Fran
`zini; John J. Horn
`
`ABSTRACT
`[57]
`Backlighting for an LCD display is provided by a direct
`backlightiunit
`is
`to the front panel in
`the
`display is mounted. When closed, the backlight unit lamps
`and re?ector transmit light directly against the back of the
`display. The re?ector surfaces are made by a combination of
`constant radius, hyperbolic, parabolic and ?at surfaces
`which maximize the emitted light transmitted to the display
`and help '?ll in for any failed or dimmed light sources.
`
`20 Claims, 3 Drawing Sheets
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`Sony Corp. Exhibit 1011
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`SONY_000743
`
`

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`US. Patent
`
`Oct. 22, 1996
`
`Sheet 1 of 3
`
`5,567,042
`
`FIG. I
`
`
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`m‘ whim/H7? 2
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`FIG. 2
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`SONY_000744
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`

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`U.S. Patent
`
`Oct. 22, 1996
`
`Sheet 2 of 3
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`5,567,042
`
`SONY_000745
`
`

`
`U.S. Patent
`
`Oct. 22, 1996
`
`Sheet 3 of 3
`
`5,567,042
`
`FIG. 5
`
`SONY_00O746
`
`SONY_000746
`
`

`
`1
`REFLECTOR FOR FLAT PANEL DISPLAY
`BACKLIGHT UNIT
`
`2
`FIG. 5 is a schematic ray tracing of the backlight unit
`illustrated in FIGS. 1-4.
`
`5,567,042
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT S‘
`
`FIELD OF THE INVENTION
`
`This invention relates to ?at panel display backlight units 5
`and in particular to re?ectors for direct backlighting units.
`Direct backlighting of liquid crystal displays is well
`known and re?ectors for such backlighting units have been
`developed. For example, US. Pat. No. 5,253,151 which
`issued Oct. 12, 1993 discloses such re?ectors.
`. It is desirable in backlighting units for ?at panel displays
`that the light produced by the backlight unit be uniform and
`capable of a high intensity over the entire viewing area of the
`display. In addition, especially for industrial computer dis
`plays where failure of the display can result in a costly loss
`of production, it is desirable that these'backlight displays be
`durable and reliable, and that they do not fail disastrously.
`
`15
`
`Referring to FIG. 1, a cabinet 10 incorporating the inven
`tion includes a front panel 12 and a cover 14. The cover 14
`is secured to the front panel 12 by a hinge 16 secured along
`corresponding vertical edges of the panel 12 and cover 14 so
`as to allow pivoting of the cover 14 relative to the panel 12
`between the open position shown in FIG. 1 and the closed
`position shown in FIG. 3.
`'
`As best shown in FIGS. 1 and 3, the front panel 12
`includes a ?at panel display 18 which may be, for example,
`a thin ?lm transistor (TFT) or metal insulator metal (MIM)
`type display. However, any ?at panel liquid crystal display
`which is backlit in operation may be used to practice the
`invention. Preferably, a diffuser plate 19, which may be for
`example a sheet of white opaque acrylic to diffuse light
`transmitted against the back of the display 18, directly
`overlies the back of the display so as to enhance the
`uniformity of the light transmitted by a backlight unit 22.
`The front panel 12 also includes a bezel 20 which frames
`the display 18 and to which the hinge plate 16A of the hinge
`16 is directly connected. Hinge plate 16B of hinge 16 is
`directly connected to a vertical panel of ?ange 21 of the
`cover 14. The cover 14 is made generally in the form of a
`box so as to house most of the electronic components of the
`enclosure 10, such as the computer which controls the
`"display 18.
`The backlight unit 22 is releasably secured with screws 24
`to the front of the cover 14 so that when the cover 14 is
`pivoted to the open position shown in FIG. 1, the front of the
`backlight unit 22 is exposed as are the heads of the screws
`24. The backlight unit 22 is shown by itself in FIG. 2. When
`the cover 14 is closed as shown in FIG. 3, the backlight unit
`22 is moved to within close proximity of the rear of the
`display 18 and to being parallel to the display 18 so as to
`transmit light against the rear of the display 18, through the
`diffuser plate 19. This provides backlighting to the display
`18 which is necessary for a user to view the indicia gener
`ated by the display 18. In order to ensure adequate cooling
`of the display 18, it is preferable to maintain an air gap of
`‘A to % inches between the closest surface of the backlight
`unit 22 and the rear of the diffuser panel 19 in the closed
`position.
`The backlight unit 22 includes a molded plastic re?ector
`26 which doubles as the structural foundation to which the
`other components of the backlight unit 22 are secured. These
`other components include 6 straight cylindrical cold cathode
`?uorescent lamps (CCFL’ s) 28A-F, metal strips 30 and 32
`along the respective left and right ends of the lamps 28A-F
`to hold the lamps in position, a left connector strip 34 for
`making contact with the left electrodes of the lamps 28A-F
`and a right connector strip 36 for making a electrical contact
`with the right electrodes of the lamps 28A—F. Elastomeric
`material 38 is preferably placed between the strips 30 and 32
`and the re?ector 26 so as to hold the lamps 28A-F securely
`in position.
`In addition, the right connector strip 36 preferably
`includes a plug half 40 to mate with a mating plug half 42
`which is wired to the electronics-in the cover 14 so that the
`backlight unit 22 may be releasably electrically connected to
`the enclosure 10. Screws 44 secure the strips 30 and 32 to
`the re?ector 26, and screws 46 secure the connector strips 34
`
`SUMMARY OF THE INVENTION
`
`The invention provides a re?ector for multiple parallel
`cylindrical light sources of the type having an arcuate
`re?ective surface section for each parallel source. Each
`surface section de?nes an apex ridge directly behind the
`corresponding source and the surface section extending from
`both sides of the apex ridge in arcuate surfaces. An improve
`ment of the invention is that the arcuate surfaces extending
`from the apex ridge are de?ned by constant radius surfaces.
`Thereby, light being transmitted directly rearward from the
`source is redirected by the constant radius surface to be
`re?ected by another re?ector surface back toward the dis
`play. The result is to increase the diffusion of the light
`re?ected from the sources, use more of the light to illuminate
`the display, and reduce the effect of an adjacent lamp
`dimming or failing completely, all of which contributes to
`the effectiveness of a re?ector of the invention.
`In one useful aspect, at least one of the constant radius
`surfaces is joined at its edge opposite from the apex ridge by
`a hyperbolic surface. This is desired in areas of the re?ector
`where dispersion and diffusion of the light from the corre
`sponding bulb is desired, such as for the interior surface
`sections of the re?ector. Thereby, when one lamp burns out,
`light from the adjacent lamps will be re?ected into the area
`of the burned out lamp to ?ll in for it and largely preserve
`the visibility of the display until the backlight unit can be
`replaced.
`For interior surface sections, hyperbolic surfaces are
`preferably provided on both sides of the apex ridge, whereas
`for the end'surface' sections, a parabolic surface is preferable
`provided on the outer side of the apex ridge. The parabolic
`surface in this location is useful to collimate the light
`re?ected from the corresponding lamp, so as to direct it
`toward the display and prevent it from escaping past the
`edge of the display. A further improvement is that a ?at
`re?ector surface may be provided outside from each para
`bolic surface, to direct redirect light toward the display.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a perspective view of a cabinet which incorpo
`rates the invention illustrated in an open position:
`FIG. 2 is a front plan view of a backlight unit of the
`invention;
`FIG. 3 is a vertical sectional view through the cabinet
`shown in FIG. 1 illustrated in a closed position;
`FIG. 4 is a detail view of a portion of FIG. 3; and
`
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`SONY_000747
`
`

`
`5,567,042
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`3
`and 36 to a peripheral ?ange 52 of the re?ector which
`extends all the way around the re?ector 26, and a wall 53
`may be molded at one or both ends of the re?ector 26 so as
`to shield wires routed to the connector strips 34 and 36 from
`a user. In addition, capacitors 48 may be provided on the
`right connector strip 36 as is well known so that a single
`power supply (housed in the cover 14, may be used to power
`all 6 lamps 28A-F, so as to run the minimum number of
`wires from the power supply in the cover 14 to the bacldight
`unit 22.
`The re?ective surface 50 of the re?ector 26 is preferably
`non-specular, for example white. This surface may be
`painted white using a very white paint. White is the preferred
`color of the surface 50 so that it re?ects light from the lamps
`26A-F diffusely, and does not provide any undesirable color
`shift to the light re?ected into the display.
`The re?ective surface 50 has a unique shape. The re?ec
`tive surface 50 is constant in cross-sectional shape in the
`horizontal direction for its length coincident with the hori
`zontal width of the illumination required for the diifuser and
`display, but vertically the shape of the surface 50 is de?ned
`by a complex surface.
`The re?ective surface 50 is de?ned by a series of surface
`sections 54A—F, each of said sections corresponding to one
`of the lamps 28A—F and being coterrninous with the next
`adjacent section(s), e.g., at its upper edge, surface 54B is
`coterrninous with surface 54A, and at its lower edge, section
`54B is coterrninous with section 54C. The interior sections
`54B-E are shaped identically to one another, and the end
`sections 54A and F are mirror images of one another.
`For clarity, only the interior section 54B will be described
`completely, it being understood that the interior sections
`54C-E are identical to the section 54B, and how the end
`sections 54A and F di?er will be described. Corresponding
`elements of each surface section are identi?ed with the
`alphabetic character which identi?es that section.
`The section 54B is divided in half by an apex ridge B1
`which runs laterally parallel to the lamp 28B. On each side
`of the apex ridge B1, the section 54B curves away from the
`apex B1 with surfaces B2 and B3 of a ?xed radius R (FIG.
`5) centered at points B8 and B9 for approximately 90°. In
`the preferred embodiment, this radius R is 2 millimeters and
`is equal to the radius of the lamp 28B. Of course, other
`dimensions could be used to practice the invention.
`The constant radius surfaces B2 and B3 fade into respec
`tive surfaces B4 and B5 at their edges opposite from the
`apex B1. The surfaces B4 and B5 are de?ned by a hyberbolic
`function of the form: x2/m—y2/n=k, where x and y are the
`dimensions as indicated in FIG. 5 as measured from point
`PB, and k, m and n are constants. In the preferred embodi
`ment, k=l millimeter and m and n are 93.3 millimeters and
`158.3 millimeters, respectively. In addition, the dimension B
`is approximately 7.39 millimeters and A is 9.635 millime
`ters.
`The outer sections 54A and F are the same as the interior
`sections 54B-E except that the surfaces A4 and F5 are
`parabolic rather than hyperbolic and are coterrninous at their
`outer ends with a ?at angled surface A6 and F6, respectively.
`A ?at angled surface similar to the surfaces A6 and F6 may
`also be used to join the surface 50 at its lateral ends to the
`?ange 52.
`The parabolic function de?ning the surfaces A4 and F5 is
`of the form y2=kx (millimeters) where x and y are as de?ned
`above and for values of y greater than R and, in the preferred
`embodiment, less than 9.39 millimeters.
`FIG. 5 illustrates section 54A and the surfaces B2 and B4
`of section 54B. Since the surfaces A3 and A5 of section 54A
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`are identical to the corresponding surfaces in the interior
`sections,-surfaces B2 and B4 are identical to the correspond
`ing surfaces in the interior sections and to F2 and F4, and the
`surfaces A2, A4 and A6 are mirror images of the surfaces F3,
`F5 and F6, respectively, FIG. 5 is used to give a complete
`description of the re?ection pattern of the entire re?ector 26.
`First, the function of the radiused surfaces A2, A3, B2 and
`B3 is to re?ect the light being transmitted rearwardly from
`the corresponding lamp (28A or B) toward the display 18.
`This can be explained by reference to ray 60. Light imping
`ing on Constant radius surface A3 is re?ected therefrom
`toward hyperbolic surface A5 and therefrom is re?ected
`toward the interior of the display 18, crossing over the next
`adjacent surface section 54B. Thus, if the lamp 28B were to
`become dim or burn out, light re?ected from lamp 28A
`would serve to ?ll in the space otherwise illuminated by light
`28B, and also light from the lamp 28C would serve to ?ll in
`the same space. The hyperbolic surfaces (AS-E5 and
`B4—F4) also serve to fan out the light rays impinging directly
`upon them, as illustrated by rays 61—64, to help ?ll in the
`next adjacent space should the lamp in that space become
`dim or fail completely.
`The parabolic surfaces A4 and F5 in contrast tend to
`collimate the light re?ected from them. Collimation rather
`than dispersion is desired here so as to direct the light toward
`the display 18, rather than outwardly past the edge of the
`display 18 where it would only serve to illuminate the
`ambient. Such collimation is represented by rays 65-68. The
`?at angled surfaces A6 and F6 also serve the function of
`re?ecting light back toward the display. This is represented
`by ray 69.
`Preferred embodiments of the invention have been
`described in considerable detail. Many modi?cations and
`variations to the preferred embodiments described will be
`apparent to those skilled in the art. For example, the inven
`tion is not strictly limited to being used with separate straight
`cylindrical parallel lamps, but could be used with a serpen
`tine cylindrical lamp having straight parallel light source
`sections. Therefore, the invention should not be limited to
`the embodiments described, but should be de?ned by the
`claims which follow.
`I claim:
`1. In a re?ector for multiple parallel cylindrical light
`sources of the type having an arcuate re?ective surface
`section for each parallel light source, each surface section
`de?ning an apex ridge directly behind the corresponding
`light source and said surface section extending from both
`sides of said apex ridge in arcuate surfaces, the improvement
`wherein said arcuate surfaces extending from said apex are
`de?ned by a constant radius surface, and wherein at least one
`of said constant radius surfaces is joined at its edge opposite
`from said apex ridge by a hyperbolic surface.
`2. The improvement as claimed in claim 1, wherein said
`constant radius surface extends from said apex for approxi
`mately 90°.
`3. The improvement as claimed in claim 1, wherein at
`least one of said constant radius surfaces is joined at its edge
`opposite from said apex ridge by a parabolic surface.
`4. The improvement as claimed in claim 2 in which the
`re?ector and light sources comprise a backlight unit
`arranged for backlighting of a display which is mounted in
`an enclosure, wherein said enclosure includes:
`a front panel in which said display is mounted so as to
`present a rear surface of said display facing toward the
`rear of said front panel;
`
`a cover;
`
`SONY_000748
`
`

`
`5,567,042
`
`5
`a hinge securing said cover to said front panel so as to
`pivot said cover relative to said display between and
`open and a closed position; and
`means for removably securing said backlight unit to said
`cover so that when said cover is in said closed position,
`said backlight unit overlies the rear of said display and
`is in position to transmit light to the rear of said display.
`5. The improvement as claimed in claim 4 wherein an air
`gap is formed between said backlight unit and said display
`when said cover is in the closed position.
`6. The improvement as claimed in claim 4 in which the
`backlight unit is accessible for removal when the cover is in
`the open position.
`7. The improvement as claimed in claim 1 in which the
`re?ector and light sources comprise a backlight unit
`arranged for backlighting of a display which is mounted in
`an enclosure, wherein said enclosure includes:
`a front panel in which said display is mounted so as to
`present a rear surface of said display facing toward the
`rear of said front panel;
`
`15
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`means for removably securing said backlight unit to said
`cover so that when said cover is in said closed position,
`said backlight unit overlies the rear of said display and
`is in position to transmit light to the rear of said display.
`12. The improvement as claimed in claim 11 wherein an
`air gap is formed between said backlight unit and said
`display when said cover is in the closed position.
`13. The improvement as claimed in claim 11 in which the
`backlight unit is accessible for removal when the cover is in
`the open position.
`14. The improvement as claimed in claim 10, wherein said
`constant radius surface extends from said apex for approxi
`mately 90°.
`15. In a re?ector for multiple parallel cylindrical light
`sources of the type having an arcuate re?ective surface
`section for each parallel light source, each surface section
`de?ning an apex ridge directly behind the corresponding
`light source and said surface section extending from both
`sides of said apex ridge in arcuate surfaces, the improvement
`wherein said arcuate surfaces extending from said apex are
`de?ned by a constant radius surface, and wherein on one
`side of said apex ridge said constant radius surface is joined
`by a hyperbolic surface and on the other side of said apex -
`ridge said constant radius surface is joined by a parabolic
`surface.
`16. The improvement as claimed in claim 15, wherein said
`parabolic surface is coterminous with a ?at surface.
`17. The improvement as claimed in claim 15 in which the
`re?ector and light sources comprise a backlight unit
`arranged for backlighting of a display which is mounted in
`an enclosure, wherein said enclosure includes:
`a front panel in which said display is mounted so as to
`present a rear surface of said display facing toward the
`rear of said front panel;
`
`a cover;
`a hinge securing said cover to said front panel so as to
`pivot said cover relative to said display between and
`open and a closed position; and
`means for removably securing said backlight unit to said
`cover so that when said cover is in said closed position,
`said backlight unit overlies the rear of said display and
`is in position to transmit light to the rear of said display.
`18. The improvement as claimed in claim 17 wherein an
`air gap is formed between said backlight unit and said
`display when said cover is in the closed position.
`19. The improvement as claimed in claim 17 in which the
`backlight unit is accessible for removal when the cover is in
`the open position.
`20. The improvement as claimed in claim 15, wherein said
`constant radius surface extends from said apex for approxi
`mately 90°.
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`a cover;
`a hinge securing said cover to said front panel so as to ‘
`pivot said cover relative to said display between and
`open and a closed position; and
`means for removably securing said backlight unit to said
`cover so that when said cover is in said closed position,
`said backlight unit overlies the rear of said display and
`is in position to transmit light to the rear of said display.
`8. The improvement as claimed in claim 7 wherein an air
`gap is formed between said backlight unit and said display
`when said cover is in the closed position.
`9. The improvement as claimed in claim 7 in which thee
`backlight unit is accessible for removal when the cover is in
`the open position.
`10. In a re?ector for multiple parallel cylindrical light
`sources of the type having an arcuate re?ective surface
`section for each parallel light source, each surface section
`de?ning an apex ridge directly behind the corresponding
`light source and said surface section extending from both
`sides of said apex ridge in arcuate surfaces, the improvement
`wherein said arcuate surfaces extending from said apex are
`de?ned by a constant radius surface, and wherein on both
`sides of said apex ridge said constant radius surfaces are
`joined by hyperbolic surfaces.
`11. The improvement as claimed in claim 10 in which the
`re?ector and light sources comprise a backlight unit
`arranged for backlighting of a display which is mounted in
`an enclosure, wherein said enclosure includes:
`a front panel in which said display is mounted so as to
`present a rear surface of said display facing toward the
`rear of said front panel;
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`45
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`a cover;
`a hinge securing said cover to said front panel so as to
`pivot said cover relative to said display between and
`open and a closed position; and
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`SONY_000749