Channelized plate
Preferred embodiments utilize a plurality of optical channels to effectively aim the light emitted by a liquid crystal display (LCD). Embodiments may also change the nominal and range of viewing angles of light in two or three dimensions in order to confine the emitted light towards the intended observer.
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This is a non-provisional patent application and claims priority to co-pending application No. 61/076,127.
TECHNICAL FIELDExemplary embodiments generally relate to an optical plate containing a plurality of optical channels or fibers. It is noted that the terms ‘channel’ and ‘fiber’ may be used interchangeable throughout this disclosure—embodiments simply require an optical path that can transmit light in selected directions. Exemplary embodiments effectively aim the light emission and/or limit the emission angle of light from a display device, including but not limited to a liquid crystal display (LCD). The invention is particularly applicable in situations where stray light emission from the LCD is problematic, either from the perspective of the primary observer or for any other reasons.
BACKGROUND OF THE ARTMost LCDs used to display a dense amount of information employ a backlight assembly to generate light that passes through a stack of components consisting of a variety of glass and plastic layers, including the liquid crystal (LC) layer and its controller that is typically a thin-film transistor. A typical LCD contains millions of pixels each consisting of red, green, and blue sub-pixels that are individually controlled to determine the instantaneous color for each pixel of the display. The specific makeup of the overall LCD stack of components determines the visual properties of the displayed image including brightness, color range, resolution, and viewing range.
The light that exits an LCD must compete with any surrounding ambient light in order for the LCD to be readable by the observer. In addition, light typically exits the LCD in a large range of angles and ultimately reflects off any surrounding surfaces, thus adding even more to the ambient light environment that the directly-observable light from the LCD must compete with. These problems may increase as the LCD becomes brighter and/or the surrounding reflective surfaces become closer to the LCD and/or the observer.
In some environments the reflection of stray LCD light off of surrounding surfaces creates a situation that is highly problematic for the observer. This phenomenon is particularly critical, for example, in the relatively tight confines of an aircraft cockpit. To make matters worse, an aircraft cockpit typically contains many metallic and glass surfaces which easily reflect both the ambient light and the non-direct LCD light, herein lumped into the single term stray light, and the pilot also needs to have excellent visibility through the windows or canopy of the cockpit. However, such stray light can be problematic in many other environments including but not limited to, automobiles, watercraft, and heavy equipment.
Summary of Exemplary EmbodimentsExemplary embodiments preferably aim the light emission from an LCD directly towards the observer. Further embodiments reduce the emission angles from the LCD thereby reducing the amount of stray light available for problematic reflections. Advanced embodiments can perform these functions in two and three dimensions and at angles that are not normal (i.e., perpendicular) to the surface of the display. In a preferred embodiment, small optical channels combined in plurality into a multi-channel plate are used to select both the nominal and range of viewing angles. The optical axis of the channels has a minimal amount of light absorption so that the brightness of the LCD is not significantly sacrificed from the perspective of the viewer. Depending on the specific manufacturing techniques and/or application requirements the channels may have a variety of cross-sectional shapes, including but not limited to circles, ovals, squares, and hexagons. A coherent multi-channel plate is created by aligning a plurality of the channels into a matrix. The multi-channel matrix may contain an additional feature called extra-mural absorption (EMA) material that can absorb stray light that is not passed or otherwise rejected by the individual optical channels.
In previous art, light controlling films have been utilized for similar applications. Among other shortcomings of this approach, the overall brightness of the display is often sacrificed, and it is also difficult to reduce stray light by tightly limiting the range of emission angles. By contrast, exemplary embodiments offer higher optical efficiency and can effectively direct light at desired angles with a tightly controlled range of emission angles. This simultaneously results in a brighter display and less stray light that can cause problematic reflections.
The foregoing and other features and advantages of the exemplary embodiments will be apparent from the following more detailed description of the particular embodiments of the invention, as illustrated in the accompanying drawings.
A better understanding of exemplary embodiments of the invention will be obtained from a reading of the following detailed description and the accompanying drawings wherein identical reference characters refer to identical parts and in which:
In exemplary embodiments, an extra-mural absorption (EMA) material may be placed between the fibers 30 to absorb light that is not adequately passed by the fibers 30. EMA can be inserted into an array of fiberoptic channels in a number of different configurations. A statistical configuration may be used, where small rods of light absorbing glass are inserted into the matrix as replacements for individual light-conducting fibers. Alternatively, an interstitial configuration may be used, where EMA is injected into the interstitial spaces between fibers. Further, a circumferential EMA may be used, where the EMA is added as a complete jacket around each individual fiber. Different EMA configurations can be used, alone or in combination, depending on the particular manufacturing techniques and end-item application.
The embodiments shown in
Although the light emission from the displays may be properly aimed at the observer in the XY plane per
It should be noted, that the optimal angle of the fibers within the channelized panel depends upon the relative angle of the face of the LCD to the observer's line-of-sight. When selecting the angle of the fibers and range of emission angles one should also consider the range of motion of the observer in the XZ plane. One should also consider the range of motion in the XY plane, or the total variations in line-of-sight that can be found among the observer or observers. For example, observers of all possible heights and orientations should be considered in order to ensure that all possible observers/positions can properly read the LCDs.
The optical channels in the invention may simply constrain the emission angle and aim the light in a direction that is normal to the LCD front face as shown in
In an exemplary embodiment the channelized plates disclosed herein could be formed in fiberoptic blocks (sometimes called boules) that contain a matrix of fibers fused together under heat and pressure. The fibers may initially be stacked as illustrated in
Additionally, the term ‘plate’ has been used throughout this disclosure to describe some embodiments. It should be noted that the use of the term ‘plate’ does not require that the opposing surfaces of the plate to be parallel. For example, the front surface of the plate may be at a different angle within the XY and XZ planes than that of the rear surface of the plate. These surfaces may be angled and/or oriented in order to accommodate the instrument panel location constraints, manufacturing concerns, and/or provide for special optical emission properties.
Although embodiments have been shown and described in relation to aircraft cockpits, it should be noted that embodiments can be utilized in any environment where the viewing of an LCD and/or the surrounding environment is hindered by ambient light or the reflection of LCD light off surrounding surfaces or both. Those skilled in the art can easily apply the exemplary embodiments to many other applications including but not limited to watercraft, automobiles, motorcycles, snowmobiles, ATVs, construction equipment, heavy machinery, and any form of instrument panel or display assembly.
The light passing through exemplary embodiments has been shown with straight arrows, or light rays, having a dashed body for convenience as is traditionally done in similar subject matter. However, in reality light travels as a wave, which is well-known to those skilled in the art. Light rays have simply been used for explanatory purposes and to simplify the figures and descriptions. As such, stray light that is not adequately contained or controlled by the optical channels may exit the plate at random angles. The EMA techniques taught above can help to reduce or eliminate this stray light. However, even without the EMA techniques a substantial majority of the light emission consists of light that is properly directed by the channels.
A[deg]≦180/pi*a sin {n1/n0*[pi/2−a sin(n2/n1)]} Eq. 1
Again, the exemplary embodiments have been described herein with simplified diagrams and figures for explanatory purposes. The following variations for exemplary embodiments should be noted.
The different fibers within the plate are not required to have the same tilt angle 110 as shown in
Additionally, the fibers are not required to have a constant core diameter from the input side of the plate 101 to the output side of the plate 102. This could allow many special features such as improving the effective fill factor of the channelized plate, effectively changing the size of the display, and/or altering the light emission angle.
Furthermore, it is not required that the input face of the plate 101 be parallel to the output face 102. For example, a relative angle between the input and output faces can allow for additional control of the nominal steering angle of the light emission. Further, neither the input face 101 or output face 102 are required to be flat, but instead may have curved profiles that can serve to further customize the emission of light from the plate. Further, a plate that has been initially fabricated with flat and parallel input and output faces may be post-processed to be mechanically curved in order to further customize the emission of light from the plate. It is noted that this curvature may be spherical, cylindrical, or any desired curvature. It will be observed by those skilled in the art that combinations of the above features, and many other shaping approaches, are easily included in the spirit of the invention for enhancing the control of light emission from the display.
Finally, other layers may be added to the input and output faces of the channelized plate in order to alter the optical properties of the plate, which may include anti-reflection coatings, polarization-dependent coatings, lensing layers (for example, cylindrical or spherical Fresnel lenses for altering the emission aiming properties), index-matching layers to liquid crystal glass, and others that are commonly known to those skilled in the art.
The makeup of a full LCD containing a channelized plate is illustrated in
An LCD which contains a fiberoptic plate may be comprised of the following components: 1) light sources 130 that are represented here as light-emitting diodes or LEDs, 2) a bulk diffuser layer 135 that serves to uniformly distribute or homogenize the light from the light sources 130, 3) an optional light-turning element 140 that serves to align the strongest components of light leaving the diffuser 135 to the optical axis of the channels in the plate 145 in order to increase the overall optical transmission efficiency of the channelized plate (this may be relatively simple image directing films, or IDF, such as produced by vendors like 3M Vikuiti), 4) the subject channelized plate invention 145 that in general may effectively steer the light in two orthogonal planes, 5) an optional lensing element 150, such as a Fresnel lens, that further alter the angular distribution of light emission from the LCD, 6) a relatively mild optional post-diffuser 155 that can serve to eliminate so-called Moire-patterns that can result from the spatial sampling differences between the light-turning element 140, the channelized plate 145, and the lensing element 150, and can also serve to blur or disguise any blemishes or defects in the same components, 7) a linear polarizer 160 that passes light that is polarized along a preferred direction for proper operation of the liquid crystal glass 165, 8) the liquid crystal layer 165 (that is actually composed of several layers including a thin-film transistor, circuitry, the liquid crystal material, and additional layers of plastic or glass), 9) another linear polarizer 170 that has its axis rotated 90 degrees with respect to the first polarizer 160, and, 10) any other optical layers 175 on the surface of the LCD that serve a particular application, including but not limited to anti-reflection and polarization-dependent coatings.
The optical emission from the LCD 180 possesses the desired aiming direction to the observer(s) and the desired viewing range for the intended positions of the observer(s). It is noted that components 130 and 135 comprise what is commonly called the backlight of the LCD. Although a diffuser 135 may not be required, in preferred embodiments a diffuser is included. Backlights can be comprised of one of many technologies including but not limited to LEDs, cold-cathode fluorescent lamps (CCFL), organic LEDs, and light-emitting polymers. It is also noted that the backlight may be ‘edge-lit’ using any of the approaches commonly used in the industry.
Having shown and described exemplary embodiments of the invention, those skilled in the art will realize that many variations and modifications may be made to affect the described invention and still be within the scope of the claimed invention. Additionally, many of the elements indicated above may be altered or replaced by different elements which will provide the same result and fall within the spirit of the claimed invention.
Claims
1. An LCD comprising:
- a backlight producing light in a plurality of angles;
- a fiberoptic plate in front of said backlight adapted to permit only light within a selected range of angles to pass through the plate;
- a light-turning element between said backlight and said fiberoptic plate which directs light only towards the selected range of angles;
- a first linear polarizer in front of said fiberoptic plate;
- a liquid crystal layer in front of said first linear polarizer;
- a lens element placed between the fiberoptic plate and the liquid crystal layer; and
- a second linear polarizer in front of said liquid crystal layer.
2. An LCD comprising:
- a backlight producing light in a plurality of angles;
- a channelized plate in front of said backlight adapted to permit only light within a selected range of angles pass through the plate;
- a first linear polarizer in front of said channelized plate;
- a lensing element between said channelized plate and said first linear polarizer;
- a liquid crystal layer in front of said first linear polarizer; and
- a second linear polarizer in front of said liquid crystal layer.
3. The LCD from claim 2 further comprising a diffuser element between said lensing element and said first linear polarizer.
4. The LCD from claim 3 further comprising an anti-reflective element in front of said second linear polarizer.
5. A method for filtering light from a LCD towards an intended observer, the LCD comprising a backlight placed behind a liquid crystal layer, the method comprising the steps of:
- placing a channelized optical plate between the backlight and the liquid crystal layer, the channelized plate comprising a plurality of optical fibers oriented in the X-Y plane towards an intended observer of the LCD, where a desired range of angles of light within the X-Y plane has been selected;
- accepting light from the backlight where the light rays travel at a plurality of angles in the X-Y plane relative to the axis of the fibers;
- allowing light rays within the selected range of angles in the X-Y plane to pass through the fibers; and
- absorbing light rays which are outside of the selected range of angles in the X-Y plane.
6. The method of filtering light from an LCD from claim 5 wherein
- said channelized plate comprises optical fibers which are further oriented in the X-Z plane towards an intended observer of the LCD and where a desired range of angles of light within the X-Z plane has been selected;
- and further comprising the steps of:
- accepting light from the backlight where the light rays travel at a plurality of angles in the X-Z plane relative to the axis of the fibers;
- allowing light rays within the selected range of angles in the X-Z plane to pass through the fibers; and
- absorbing light rays which are outside of the selected range of angles in the X-Z plane.
7. A liquid crystal display assembly comprising:
- a liquid crystal layer;
- a backlight placed behind the liquid crystal layer; and
- a channelized optical plate between the backlight and the liquid crystal layer, the plate having a plurality of axially parallel optical fibers which terminate at one end in an entrance surface and at the other end in an exit surface, wherein said fibers are adapted to accept light through the entrance surface in a plurality of x-y angles which are defined as the angle between the axis of the fiber and the light ray within the x-y plane, and where a critical x-y angle is defined as the largest x-y angle where the corresponding light ray can substantially pass through said fiber without being absorbed; emit light through the exit surface if the x-y angle is less than the critical x-y angle; and substantially absorb light if the x-y angle is greater than the critical x-y angle.
8. The liquid crystal display assembly of claim 7 wherein:
- the axis of the fibers are generally non-normal to the entrance surface within the x-y plane.
9. The liquid crystal display assembly of claim 7 further comprising:
- light absorbing material disposed between said fibers.
10. The liquid crystal display assembly of claim 7 wherein:
- said critical x-y angle is 15 degrees or less.
11. The liquid crystal display assembly of claim 7 wherein:
- the distance between the entrance and exit surfaces causes light rays which enter at x-y angles greater than the critical x-y angle to reflect at least once off the fiber.
12. The liquid crystal display assembly of claim 8 wherein:
- said entrance surface and exit surface are substantially flat and substantially parallel.
13. The liquid crystal display assembly of claim 8 wherein:
- said exit surface has a curved profile.
14. The liquid crystal display assembly of claim 8 wherein:
- said exit and entrance surfaces have curved profiles.
15. The liquid crystal display assembly of claim 8 wherein:
- the axis of said fibers are directed towards an intended observer.
16. The liquid crystal display assembly of claim 7 wherein:
- the axis of said fibers are generally non-normal to the entrance surface within the x-z plane; and
- said fibers are further adapted to: accept light through the entrance surface in a plurality of x-z angles which are defined as the angle between the axis of the fiber and the light ray within the x-z plane, and where a critical x-z angle is defined as the largest x-z angle where the corresponding light ray can substantially pass through said fiber without being absorbed; emit light through the exit surface if the x-z angle is less than the critical x-z angle; and substantially absorb light if the x-z angle is greater than the critical x-z angle.
17. The liquid crystal display assembly of claim 16 further comprising:
- light absorbing material disposed between said fibers.
18. The liquid crystal display assembly of claim 16 wherein:
- said critical x-z angle is 15 degrees or less.
19. An LCD comprising:
- a backlight producing light in a plurality of angles;
- a channelized plate in front of said backlight and containing optical fibers which permit light within a selected range of angles to pass through the plate while substantially absorbing light which is outside the selected range of angles;
- a light diffusing layer placed between the backlight and the channelized plate;
- a liquid crystal layer in front of the channelized plate; and
- a lens element placed between the channelized plate and the liquid crystal layer.
20. The LCD of claim 19 further comprising:
- a light turning element placed between the light diffusing layer and the channelized plate.
21. The LCD of claim 19 wherein:
- the lens element is a Fresnel lens.
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Type: Grant
Filed: Aug 15, 2008
Date of Patent: Oct 8, 2013
Patent Publication Number: 20090322987
Assignee: American Panel Corporation (Alpharetta, GA)
Inventors: William Dunn (Alpharetta, OH), Michael LeCave (Alpharetta, GA), Harry Presley (Alpharetta, GA)
Primary Examiner: Wen-Ying P Chen
Application Number: 12/192,285
International Classification: G02F 1/1335 (20060101);