WO2010098785A1

WO2010098785A1 - System and method for decreasing the thickness of a liquid crystal display

Info

Publication number: WO2010098785A1
Application number: PCT/US2009/051018
Authority: WO
Inventors: Estill Thone. Hall Jr.
Original assignee: Shenzhen Tcl New Technology Ltd
Priority date: 2009-02-26
Filing date: 2009-07-17
Publication date: 2010-09-02
Also published as: CN101504498B; CN101504498A

Abstract

Embodiments of the present techniques provide a backlight illumination system (76). The backlight illumination system comprises a light source, e.g., fluorescent tubes (26), configured to emit light in all directions for illuminating an LCD system. The backlight illumination system (76) further comprises a mirror (22) disposed behind the fluorescent tubes (26), wherein the mirror (22) includes beveled reflectors (28) and vertical reflectors (30), wherein the vertical reflectors (30) are located between each two beveled reflectors (28). In embodiments, this configuration may increase the amount of light reflected along the display axis 78 towards the front of the unit, which may allow the thickness of the LCD display to be decreased.

Description

SYSTEM AND METHOD FOR DECREASING THE THICKNESS OF

A LIQUID CRYSTAL DISPLAY

TECHNICAL FIELD

The present techniques relate generally to video display systems. More specifically, the present techniques relate to backlight illumination of video display systems, such as liquid crystal displays (LCDs).

BACKGROUND

This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present embodiments that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

Backlit displays, such as liquid crystal display (LCD) panels, are employed in a variety of display systems. Such systems may include, for example, flat screen computer monitors, portable computers, digital cameras, cellular telephones, hand-held devices, flat screen television sets (TVs), digital watches, and so forth. The LCD panel incorporated in such systems may include a matrix of transistors or other micro-devices acting as electrical switches that modulate light. In cooperation with other components, such as polarizing filters, the modulation of the light may be used to generate an image.

The light used to generate the image may be reflected light, transmitted through the front surface of the LCD and reflected from a mirror behind the LCD, e.g., in LCD watches. In other LCDs, the light may be provided by a light source from the back side of the panel, e.g., a backlight. Generally, color LCDs require a backlight, since reflected light may not adequately illuminate the display. For example, the light used for illuminating an LCD may be provided by a plurality of fluorescent tubes, which are disposed behind the LCD panel.

As the light generated by the fluorescent tubes is generally emitted uniformly, a reflector may be placed behind the fluorescent tubes to direct more of the light towards the front of the LCD. Further, for a proper image (e.g., one of uniform brightness), to be formed, it is desirable that the light from the fluorescent tubes be evenly distributed across the surface of the LCD, and aligned substantially perpendicular to the LCD. However, these requirements may cause the display to be thicker than desirable. Indeed, among other things, the light must have sufficient distance to be scattered and reflected. BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the techniques may become apparent upon reading the following detailed description and upon reference to the drawings in which:

FIG. 1 is a block diagram of a display system in accordance with an embodiment;

FIG. 2 is a schematic diagram of another display system in accordance with an embodiment;

FIG. 3 is a perspective view of a mirror and adjacent fluorescent tubes in accordance with an embodiment;

FIG. 4 is a perspective view of a mirror and adjacent fluorescent tubes in accordance with another embodiment; and

FIG. 5 is a process flow diagram showing a method for providing backlight to a display system in accordance with an embodiment.

DETAILED DESCRIPTION

One or more specific embodiments of the present techniques will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

Embodiments of the present techniques provide a liquid crystal display (LCD) having an improved reflector for backlighting. The improved reflector may include beveled reflectors, e.g., triangular reflectors, with vertical reflectors, e.g., reflectors projecting outwards from the reflector surface in a generally vertical orientation relative to the reflector surface, located between each of the beveled reflectors (referred to as a "multiply reflecting mirror system" below). As used herein, terms describing geometric shapes, such as triangular, pyramidal, and point, should be understood to indicate that the shapes are not ideal shapes, but are substantially as described, e.g., substantially triangular, substantially pyramidal, and substantially small in area.

The multiply reflecting mirror system essentially folds the light path, which may increase the distance that light emitted away from the front of the LCD travels, in comparison to a flat reflector surface, before impinging on a diffuser, as discussed below. The increased length of the light path may allow more scattering to take place and, thus, may allow the thickness of an LCD to be decreased. Further, the configuration may improve the amount and alignment of light reaching other components in the display, creating a higher quality image.

An overview of an LCD system 10 in accordance with an embodiment is provided in the block diagram shown in FIG. 1. It should be noted that the LCD system is set forth herein as an example of a backlit display. However, present embodiments are not limited to LCD technology. Indeed, embodiments of the present techniques may be incorporated into or include various types of backlit displays.

In some embodiments, the LCD system 10 may comprise an LCD monitor such as those used in computers, TVs or the like. The LCD system 10 includes an illumination system 12. As discussed in detail below, the illumination system 12 may include fluorescent tubes or other light producing devices configured to generate white or colored light 13 for providing backlight illumination for the LCD system 10.

The illumination system 12 may include additional components, such as the multiply reflecting mirror system discussed with respect to FIGS. 2, 3 and 4, below, to increase the length of the path that light 13 generated by the fluorescent tubes travels before impinging on components in the LCD system 10. The increased path length may allow the fluorescent tubes to be positioned closer to the multiply reflecting mirror system and a diffuser plate to be positioned closer to the fluorescent tubes within the LCD display.

The LCD system 10 may include a diffusing and polarizing element 14. The diffusing and polarizing element 14 may include a diffusing component 14A and a polarizing component 14B. The diffusing and polarizing element 14 may be adapted to diffuse the light 13 emanating from the illumination source 12. For example, the diffusing component 14A of the diffusing and polarizing element 14 may act to smooth or smear the light 13 to create a uniform backlight distribution. Further the diffusing component 14A may scatter light 13 towards the polarizing component 14B. The polarizing component 14B may function to linearly polarize the light 13 generated by the illumination source 12. Thus, the diffusing and polarizing element 14 may produce diffused and polarized light 15.

During operation of the LCD system 10, the diffused and polarized light 15 from the diffusing and polarizing element 14 passes through an LCD panel 16. In other embodiments, the LCD panel 16 may be replaced by different types of backlit panels. In the LCD panel 16, active micro-devices may modulate the light 15, for example, by changing the polarization axis of the light 15 in response to applied current, as discussed in detail with respect to FIG. 2, below. Thus, the LCD panel 16 may produce modulated light 17. As the amount of modulation is proportional to the current applied to a micro-device, the luminance of any single point in an image, such as a pixel, that is controlled by a particular micro-device may be adjusted.

During operation of the LCD system 10, the modulated light 17 from the LCD panel 16 may be directed to a polarizing screen 18 to facilitate producing an image 19. The image 19 may be formed when the modulated light 17 at each pixel is either blocked to some degree or passed by the polarizing screen 18. The brightness of the image 19 may be determined by the degree of alignment of the polarization axis of the modulated light 17 with the polarization axis of the polarizing screen 18.

FIG. 2 is a more detailed representation of an LCD system 20 in accordance with an embodiment of the present techniques. The LCD system 20 shown in FIG. 2 depicts components that may be included within a display system in accordance with present embodiments, such as the LCD system 10. Further, FIG. 2 depicts the manner in which such components may function relative to one another for the generation of an image, in accordance with various embodiments. However, the present techniques are not limited to the method of forming an image discussed below. One of ordinary skill in the art will recognize that any number of other methods for forming an image may be used with an improved backlight containing a multiply reflecting mirror.

As illustrated in FIG. 2, a mirror 22 is disposed at one end of the LCD system 20. The mirror 22 is generally configured to reflect light generated by a light source 24 along the axis of an image 25 formed by the LCD system 20. The light source 24 may be disposed subsequent to the mirror 22 and closer to the front of the LCD system 20. Further, the light source 24 may include a plate containing light emitting devices. For example, the light source 24 may include a number of fluorescent tubes 26 configured to generate light for the LCD display 20. The number of fluorescent tubes 26 in the light source 24 may be varied to control factors such as the brightness, cost, or quality of a display. For example, a larger LCD system 20 may use more fluorescent tubes 26 to increase the brightness, such as 16, 18, 22, or even more tubes, while a smaller or portable unit may use fewer, such as 8, 10, or 14 tubes, to lower power demands. In other embodiments, the light source may be a panel having light emitting diode (LED) point sources placed across the front of the panel. In such embodiments, the mirror configuration would be modified appropriately, as discussed below.

As discussed in detail with respect to FIGS. 3 and 4, below, the mirror 22 may have beveled reflectors 28, either positioned in alignment or spaced between, each of the fluorescent tubes 26. The mirror 22 may also have vertical reflectors 30. Light emitted from the fluorescent tubes 26, as indicated by light beam 27, may be reflected multiple times between the vertical reflectors 30 and beveled reflectors 28 prior to being emitted in the general direction of the diffuser 32. Accordingly, the combination of the beveled reflectors 28 with the vertical reflectors 30 may provide a longer potential path length for the reflected light 34 from the fluorescent tubes 26 to travel, in comparison to a flat reflector having no projecting surfaces.

As shown in the embodiment illustrated in FIGS. 2 and 3, the beveled reflectors 28 may be aligned with each the fluorescent tubes 26 and the vertical reflectors 30 may be located between the beveled reflectors 28. However, in other embodiments the vertical reflectors 30 may be located under the fluorescent tubes 26, as discussed with respect to FIG. 4, below.

One of ordinary skill in the art will recognize that the lighting does not have to be provided by fluorescent tubes. Indeed, any source of lighting, e.g., light emitting diodes (LEDs), may be used. If the source of light chosen is a point source rather than the linear light source shown in FIG. 2, the mirror design may be adjusted accordingly. For example, the beveled mirrors 28 may be replaced with pyramidal mirrors, and the vertical reflectors 30 may be aligned across both directions creating box-like structures around the pyramidal mirrors. The pyramidal reflectors may be aligned with the LEDs or may be spaced between the LEDs. In an embodiment, the LCD system 20 may include the diffuser 32. In various embodiments, the diffuser 32 may be an opaque or translucent plastic film or glass sheet. The diffuser 32 may smooth or smear the light emitted by the fluorescent tubes 26 and reflected from the mirror 22 and, thus, more uniformly distribute the light. Further, proper image generation may depend on the extent to which the light from the light source 24 is polarized before reaching an LCD panel 38. The ability of the LCD system 20 to polarize the light may depend on the angular distribution of the light when it impinges on a polarizing filter 40. Accordingly, if the angular distribution of the light is too wide, this may result in backlight illumination that is only partially polarized. This may result in decreased image contrast, with the dark hues of an image being too light. The diffuser plate 32 may compensate for the wide angular distribution of light by scattering light that is emitted or reflected at a shallow angle towards the front of the unit, represented by light beam 42. In various embodiments, scattered light 36 from the diffuser 32 may impinge a fiber optic screen 44 which may be placed between the diffuser 32 and the polarizer 40, as illustrated in FIG. 2. In other embodiments, the fiber optic screen 44 may be eliminated. In such embodiments, the polarizer 40 may be combined with the diffuser 32 to form a single unit.

The fiber optic screen 44 may, for example, be made from a large number of fiber optic fibers joined in a vertical fashion (e.g., aligned with the axis of the image 25) to form a plate or screen. The fibers may be formed from any number of materials, including, for example, glass, plastic, or clear ceramics. The fiber optic screen 42 may substantially block scattered light, such as that represented by light beams 46, that is not adequately aligned with the component optical fibers. Further, the fiber optic screen 42 may pass light, such as that represented by light beams 46, that has an angular incidence on the fiber optic screen 44 that is within a few degrees (e.g., about 5^Q, 10^Q, or 15^Q) of perpendicular to the fiber optic screen 44. This may significantly improve the contrast of the image 25 produced by the LCD system 20 by lowering the amount of partially polarized light transmitted from the polarizer 40. The angularly aligned light 48 may then impinge on the polarizer 40.

The polarizer 40 may be formed of a polarizing material, such as a doped polymer, glass, or similar materials. Further, the polarizer 40 may be disposed within the LCD system 20 such that its polarization axis is oriented along a first direction relative to the LCD system 20, as indicated by arrows 50. In this manner, the polarizer 40 polarizes the angularly aligned light 48 from the fiber optic screen 44 along the first direction to produce polarized light 52. The polarized light 52 may then be modulated by an LCD panel 38 to create the image.

The LCD panel 38 may be made up of active or passive micro- devices that include liquid crystalline materials. For example, in one embodiment, the LCD panel 38 may comprise a matrix of active micro-devices that utilize thin film transistors (TFTs) disposed along pixel intersections of a grid comprising the display matrix. The luminance of the pixels of the LCD panel 38 may be controlled by the current applied by the TFTs. In another embodiment, the LCD panel 38 may comprise a passive matrix employing a grid of conductors, whereby the pixels are disposed along intersections of the display matrix. In such an embodiment, the pixels may be controlled by current driven across two conductors disposed along the grid comprising the matrix of pixels. As for the active matrix TFT the luminance of an individual pixel may be controlled by the current applied.

In an embodiment of the LCD system 20, twisted nematic liquid crystals may be controlled by the micro-devices in the LCD panel 38 to form the image. One of ordinary skill in the art will recognize that any number of other technologies used to generate an image, both existing and not yet developed, may benefit from the multiply reflecting mirror system of the present techniques.

Generally, in a twisted nematic liquid crystal display, the LCD panel 38 is located between two polarizing filters, for example the polarizer 40 and a polarizing screen 54. The polarization axes 52 of the polarizer 40 and a polarization axis 56 of the polarizing screen 54 may generally be perpendicularly aligned. For example, the polarization axis 56 of the polarizing screen 54 may be aligned along a second direction if the polarization axis 50 of the polarizer 40 is aligned in a first direction.

In the LCD panel 38, the liquid crystal molecules in a non- energized cell 58 may rotate the polarization of the light from the polarizer 40 by 90^Q, e.g. from the first direction to the second direction. If the polarizing screen 54 has a polarization axis 56 that is perpendicular to the polarizer 40, the rotated light 60 from the LCD panel 38 may pass through the polarizing screen 54 and form the image 25. In contrast, the liquid crystal molecules in an energized cell 68 may be aligned, thus allowing light 70 to pass without rotating the polarization. Since, in this embodiment, the polarization of the emitted light 52 from the polarizer 40 has not been rotated, it is essentially perpendicular to the polarizing screen 54 and substantially blocked. Thus, light 72, which passed through the polarizing screen 54 and forms the image 25 seen by a viewer, has generally passed through a non-energized cell 58.

One of ordinary skill in the art will recognize that this is not the only configuration that may be used in a twisted nematic LCD. Indeed, the polarization axis 50 of the polarizer 40 and the polarization axis 58 of the polarized screen 54 may be aligned. In this embodiment, rotated light from a non-energized cell 58 would be blocked by the polarizing screen 54. Each of the components discussed above will block a portion of the light 27 emitted by the light source 24, lowering the brightness of the image 25. To improve the brightness, the distance 74 between the light source 24 and the mirror 22 and the distance 76 between the light source 24 and the diffuser 32 may be increased, allowing more of the emitted light 27 to be scattered in the direction of the diffuser 32. However, increasing these distances 74 and 76 may also increase the thickness of the LCD panel, which may generally be undesirable. The multiply reflecting mirror system of the present techniques provides longer paths for reflected light 34 to travel, essentially folding the light path. This essentially allows the benefit of increasing the distances 74 and 76 to be obtained without making the LCD panel thicker.

A multiply reflecting mirror system 76, in accordance with an embodiment, is illustrated in more detail in FIG.3. As shown in FIG. 3, fluorescent tubes 26 generally emit light uniformly. The light emerging from the fluorescent tubes 26 propagates at varying angles relative to the display axis 78 of the LCD, which indicates the direction of the image 25 formed by the LCD panel. Light 80 emitted in the general direction of the display axis 78 may be used to form the image 25. However, light emitted away from the display axis 78 may be reflected to assist in forming the image 25. In the discussion below, only a few of the possible angular paths for the emitted and reflected light are shown as examples. As illustrated in FIG. 3, a portion of the light emitted away from the display axis 78, as indicated by light beam 82, may directly impinge on the flat surface of mirror 22 and be reflected back in the general direction of the display axis 78, as indicated by light beam 84. However, in various embodiments, the mirror 22 may have beveled reflectors 28 located below each of the fluorescent tubes 26. The beveled reflectors 28 may, for example, be triangular, with a top edge generally aligned with the fluorescent tubes 26. Vertical reflectors 30 may generally be placed between the beveled reflectors 28.

In another example, a portion of the emitted light, as indicated by light beam 86, may impinge on one of the beveled reflectors 28 and be reflected in the direction of the mirror 22, as indicated by light beam 88. The reflected light 88 may then be reflected from the flat surface of the mirror 22 towards one of the vertical reflectors 30, as indicated by light beam 90. The reflected light 90 may then be further reflected back towards the beveled reflector 28, as indicated by light beam 92. The reflected light 92 may then be reflected from the beveled reflector 28 in the general direction of the display axis 78, as indicated by light beam 94, where the reflected light 94 may assist is forming the image 25. The angle of the light reflected from the vertical reflector 30 may be too large to reflect off the beveled reflector 28 a second time, as indicated by light beam 96 and, in this circumstance, the reflected light 96 may continue in the direction of the display axis 78, contributing to the image 25. In another example, a portion of the light emitted by the fluorescent tubes 26, as indicated by light beam 98, may directly impinge on one of the vertical reflectors 30 and be reflected back towards one of the beveled reflectors 28, as indicated by light beam 100. The reflected light 100 may then be reflected in the general direction of the display axis 78, as indicated by light beam 102. One of ordinary skill in the art will recognize that the reflection paths discussed above are merely examples, and that any number of possible paths may exist for the light to be reflected in the general direction of the display axis 78.

The shapes of each of the beveled reflectors 28 may be controlled to adjust the angle of light reflected and, thus, control the path lengths for the reflections. For example, angles that the surface 104 of each of the beveled reflectors 28 intersect the horizontal surface of the mirror 22 may be adjusted to create more reflections between the beveled reflector 28 and the vertical reflector 30, for example, by decreasing the interior angle 106 at the top of each of the beveled reflectors 28. The adjustment of the interior angle 106 to create more reflections must be balanced against the direction of the reflected light. For example, a smaller interior angle 106 may provide a longer path length for the reflected light, but may also tend to reflect that light at a greater angle from the display axis 78, for example, closer to perpendicular to the display axis 78. As discussed with respect to FIG. 2, above, increasing the amount of light that is closer to perpendicular to the display axis 78 may contribute to a poor quality image 25, if no fiber optic screen 44 is present, or to a dimmer image 25, if a fiber optic screen 44 is present.

The shapes of the vertical reflectors 30 may also be adjusted to modify the length of the reflected light paths and the direction of the reflected light. For example, a vertical surface 107, having an intersection angle 108 of 90^Q with the surface of the mirror 22 may be replaced with an surface having a smaller intersection angle 108 with the surface of the mirror 22, creating a second set of beveled reflectors. In an embodiment, the angle 108 may be kept high, for example, about 75^Q to about 90^Q, although lower angles may be used. As for the adjustment of the interior angle 106 of the beveled reflectors 108, the adjustment of the intersection angle 108 may be optimized to direct more of the light in the direction of the display axis 78.

The heights of the beveled reflectors 28 and vertical reflectors 30 may be adjusted relative to the positions of the light source, such as the fluorescent tubes 26, above the mirror 22. For example, each of the beveled reflectors 28 and vertical reflectors 30 may project from the mirror 22 to about 10% to about 90% of the distance to the fluorescent tubes 26 or about 50% of the distance to the fluorescent tubes. In various embodiments, the distance between the mirror 22 and the fluorescent tubes may be between about 2 millimeters (mm) and about 10 mm. In an embodiment, the distance between the mirror 22 and the fluorescent tubes may be about 5 mm. The mirror 22, beveled reflectors 28, and vertical reflectors 30 may be formed from any number of materials including glass, metal, ceramic, or plastic. These materials do not need to be transparent as light will generally be reflected from them. The choice of materials may be made on the basis of functional properties, including, for example, stiffness, heat resistance, and weight, among others. Plastics that may used in embodiments include, for example, high impact polystyrene (HIPS), polycarbonate (PC), polyacrylate, polyphenylene sulfide, and polyvinylchloride (PVC), among others.

The beveled reflectors 28 may be formed on the surface of the mirror 22 using any number of techniques. Generally, the shapes will be formed prior to coating with a reflective surface, such as a mirror coating. For example, the beveled reflectors 28 may be formed as an integral part of the mirror 22 by molding, etching, photolithography, or any other suitable technique known in the art. Alternatively, the bevel reflectors 28 may be formed separately and joined to the surface of the mirror 22 by adhesive, ultrasonic welding, heat fusion, or any similar techniques used to join surfaces. After the mirror 22 with the beveled reflectors 28 has been formed, it may be coated. The vertical reflectors 30 may be formed using similar techniques and may be formed at the same time as the beveled reflectors. However, the beveled reflectors 28 and vertical reflectors 30 do not need to be formed using the same techniques or during the same process steps, but may be independently constructed and later assembled. For example, the vertical reflectors 30 may be joined to panels having previous formed beveled reflectors 28. After the mirror 22 with the beveled reflectors 28 and the vertical reflectors 30 has been formed, the reflective surfaces of the beveled reflectors 28, the vertical reflectors 30, and the mirror 22 will generally be coated (e.g., silvered) to increase the total amount of light reflected along the axis 74, toward the front of the LCD.

The beveled reflectors 28 do not have to be located directly underneath the fluorescent tubes 26. As illustrated in the perspective view of FIG. 4, the vertical reflectors 30 may be generally aligned with the fluorescent tubes 26 and the beveled reflectors 28 may be spaced between the fluorescent tubes 26. As in FIG. 3, the fluorescent tubes 26 generally emit light uniformly, with a portion of the light emitted in the general direction of the display axis 78, as indicated by light beam 80. Furthermore, a portion of the emitted light, indicated by light beam 82, may be reflected from the flat surface of the mirror 22 in the general direction of the display axis 78, as indicated by light beam 84, and this reflected light may then be used in forming the image 25.

Further, a portion of the emitted light, indicated by light beam 1 12, may impinge on one of the beveled reflectors 28 and be reflected in the direction of the one of the vertical reflectors 30, as indicated by light beam 1 14. In one example of the reflections that may occur, the angle of the reflected light 1 14 may lead to numerous reflections, indicated by light beams 1 16, between the beveled reflector 28 and the vertical reflector 30. A final reflection, indicated by light beam 1 18, from the vertical reflector 30 to the beveled reflector 28 may be reflected towards the display axis 78, as indicated by light beam 120.

The number of reflections and the final angle may be determined by the initial angle of the emitted light. For example, a portion of the emitted light, indicated by light beam 122, may impinge on one of the beveled reflectors 28 at an angle that leads to a reflection to one of the vertical reflectors 30, indicated by light beam 124. The light reflected from the vertical reflector 30, indicated by light beam 126, may then be reflected from the flat surface of the mirror 22, as indicated by light beam 128. The reflected light 128 may then be reflected from a beveled reflector 28 in the general direction of the display axis 78, as indicated by light beam 130.

In a final example, a portion of the light emitted by the fluorescent tubes 26, indicated by light beam 132, may impinge directly on the surface of the mirror 22, but at a sufficiently shallow angle to be reflected to one of the beveled mirrors 28, as indicated by light beam 134. The light reflected from the beveled reflector 28, as indicated by light beam 136, may then be directed along the display axis 78 to assist in forming the image 25. The same materials may be used to form the multiply reflecting mirror system 1 10 in this embodiment as discussed with respect to FIG. 3, above. Similarly, the same techniques may be used to form the beveled reflectors 28 and the vertical reflectors 30.

FIG. 5 is a process flow diagram showing a method for providing backlight to a display unit in accordance with an embodiment of the present techniques. The method is generally referred to by the reference number 200, and may be used with the display devices described above. The method 200 begins at block 202. In the method 200, light is emitted in all directions (block 204) by a light source, e.g., the plurality of fluorescent tubes 26 of the LCD display system. Thereafter, the method 200 proceeds to block 206, whereby a portion the emitted light is received by a multiply reflecting mirror system, as described above.

The beveled reflectors, vertical reflectors, and mirror surface described above may all reflect (block 208) the back-propagating portion of the light forward. As discussed above, the use of both beveled reflectors and vertical reflectors may provide a longer path length for light to reflect, which may allow the light to more efficiently be directed towards the front of the unit.

Thereafter, at block 210, the emitted light of block 204 and the reflected light of block 208 propagate forward toward the LCD panel where the light is modulated to form an image. The use of beveled reflectors and vertical reflectors may allow the mirror 22 and diffuser 32 to be placed in closer proximity to the fluorescent tubes 26, which may allow the thickness of the unit to be decreased.

While the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the present disclosure is not intended to be limited to the particular forms disclosed. Rather, the present disclosure is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present disclosure as defined by the following appended claims.

Claims

What is claimed is:

1. A backlight illumination system (76, 1 10), comprising: a light source (24) configured to emit light for illuminating a display unit (20), wherein the light source (24) comprises at least two light emitters (26); a mirror (22) disposed behind the light source (24), wherein the mirror (22) is configured to reflect a portion of the light multiple times from a multiply reflecting mirror system (76, 1 10) so as to increase the effective path length for the light.

2. The system of claim 1 , wherein the display unit (20) is a liquid crystal display (LCD).

3. The system of claim 1 , wherein the light source (24) is a plate comprising at least two fluorescent tubes (26).

4. The system of claim 1 , wherein the mirror (22) comprises beveled reflectors (28) and a vertical reflector (30) disposed between any two beveled reflectors (28).

5. The system of claim 4, wherein the beveled reflectors (28) are aligned with the light emitters (26).

6. The system of claim 4, wherein the vertical reflectors (30) are aligned with the light emitters (29).

7. The system of claim 1 , wherein the light source (24) comprises at least two light emitting diodes.

8. The system of claim 7, wherein the mirror (22) comprises pyramidal reflectors and a vertical reflector disposed between any two pyramidal reflectors.

9. The system of claim 8, wherein the pyramidal reflectors are aligned with the light emitting diodes.

10. The system of claim 8, wherein the vertical reflectors (30) are aligned with the light emitting diodes.

1 1. The system of claim 1 , comprising a light pipe panel (44) disposed between the light source (24) and an LCD panel (38).

12. A method for providing backlight illumination to a display unit, comprising: emitting light (27) by a light source (24) of a display unit (20); reflecting a portion of the light (27) multiple times from a multiply reflecting mirror system (76, 1 10) so as to increase the path length for the reflected portion of the light (34); and providing the light (27) from the light source (24) and the reflected portion of the light (34) as a combined light to the display unit (20) for forming an image (66).

13. The method of claim 12, wherein the light source (24) comprises a plurality of fluorescent tubes (26).

14. The method of claim 12, comprising polarizing the combined light prior to providing the polarized light (52) to an LCD panel (38).

15. The method of claim 12, comprising applying an electric current to cells (68) of the LCD panel (38) to modulate the polarized light (52).

16. The method of claim 13, comprising blocking light not substantially parallel to the axis of the display unit (20).

17. A video display, comprising: a light source (24) configured to emit light (27) for illuminating a display unit (20); a mirror (22) disposed behind the light source, wherein the mirror (22) is configured to provide a longer path length for a reflected portion of the light (34); an LCD panel (38) configured to form an image (25) based on the light; and a screen (54) configured to display the image produced by the LCD panel.

18. The video display of claim 18, wherein the light source (24) comprises at least two fluorescent tubes (26).

19. The video unit of claim of claim 18, wherein the mirror (22) comprises two or more triangular beveled reflectors (28) and a vertical reflecting surface (30) disposed between each two triangular beveled reflectors (28).

20. The video display of claim 18, wherein the light source (24) comprises at least two light emitting diodes.

21 . The video display of claim 18, wherein the mirror (22) comprises two or more pyramidal reflectors and a vertical reflecting surface disposed between each two pyramidal reflectors.