Source: https://patents.justia.com/patent/6927908
Timestamp: 2019-05-24 22:50:54
Document Index: 391203141

Matched Legal Cases: ['art 305', 'arts 310', 'arts 310', 'art 310', 'arts 340', 'art 350', 'arts 340', 'art 340', 'art 350', 'art 360', 'art 340', 'art 360', 'art 340', 'art 350', 'art 350', 'art 350']

US Patent for Visual display screen arrangement Patent (Patent # 6,927,908 issued August 9, 2005) - Justia Patents Search
Justia Patents With Reflector Or Additional ScreenUS Patent for Visual display screen arrangement Patent (Patent # 6,927,908)
Nov 7, 2001 - Seamless Display Limited
A visual display screen (100′) such as an LCD screen is provided with a display area (30) for displaying an image. The display area (30) extends as far as an optically inactive region (60), containing device drivers, at the edge of the screen. A cover plate assembly (40) overlays the display area (30). The cover plate assembly is laminar and an upper translucent plastics layer (520) thereof is planar over the display area (30) but is curved at the edge to provide a lens there. Thus, the image in the display area viewed through the cover plate assembly (40) appears to be shifted to the edge of the screen (100′) so that the optically inactive region (60) becomes invisible. Two screens can be abutted adjacent each other with no visible join using this technique. Compression of the image at the edge compensates for edge distortion by the lens. Repeating of the image either side of the join between two screens increases the viewing angle beyond which the join appears.
This Application is a Section 371 National Stage Application of International Application No. PCT/GB01/04926, filed Nov. 7, 2001 and published as WO 02/42838 on May 30, 2002.
This invention relates to a visual display screen arrangement.
Many modern electrical or electronic devices contain a visual display. For example, mobile telephones, porkable and particularly palm-held digital computers each contain a (typically) backlit liquid crystal display (LCD) screen. In each case, the desire to miniaturise and thus increase the portability of such devices is balanced by the need to ensure that the screen that imparts information to the user has an adequate viewing area. In the field of mobile telephones, the emergence of technologies to view Internet pages has provided a further need to increase screen size.
Finally, EP-A-0,559,070 shows an LCD panel where an attempt has been made to reduce the gap itself. The LCD panels are bent by 90° at the edges so as to bring the active area physically closer to the edge. Then, the edge seal and contacts extend downwards from the surface of the screen and do not contribute to the gap. Even then, the gap is only reduced (to perhaps 1-2 mm), and whilst this would potentially be adequate for large wall displays using adjoining screens, it would still be visible in smaller (e.g. hand holdable) screens. Moreover, the manufacture of the screens of EP-A-0,559,070 would be much more difficult than with ‘standard’ LCDs.
It is an object of the present invention to address these problems wish the prior art. Specifically, it is an object of the present invention to maximize the viewing area of a visual display particularly, but not exclusively, for use with a relatively small electronic device.
In preference, the cover member is formed as a laminar construction with, for example, a lower layer adjacent to the display area and formed of a first material, an upper layer formed of a second, different material, and a polarisation/compensation layer sandwiched between the upper and lower layers. In that case, the lower layer may be formed of glass and the upper layer of a plastics material. This allows a very simple construction for the arrangement. A ‘standard’ LCD can be made without any changes to the glass layer. A plastics layer can then be laminated on top, and its edge bevelled for example to provide the light bending at that edge. Then the glass layer (which may contain delicate structures) need not be machined.
Such an arrangement is particularly advantageous for small, hand-held devices such as mobile telephones, video cameras or so-called “palm top” computers. When not in use, the overall height and width of a device having the arrangement of the invention need be no larger than previously. By unfolding the screen arrangement, however, a composite screen which is much larger than the electronic device with which it communicates may be provided. The advantages of a mobile telephone with a composite screen which is, for example, 15-20 cm wide (rather than the standard width of 3-5 cm) are manifest, particularly for telephones with Internet access.
The invention may be put into practice in a number of ways, and some of these will now be described by way of example only and with reference to the following Figures in which:
FIG. 8a shows images formed in the display areas of each of the two LCDs of FIG. 2, without the lenses;
FIG. 8b shows suitable dimensions for a large scale model of the image of FIG. 8a but with repeated strips;
FIGS. 10a and 10b show ray diagrams for the panel arrangement of FIG. 2, when viewed perpendicular to the plane of the panel and at an angle thereto respectively;
FIGS. 11a, 11b and 11c show alternative embodiments of one aspect of the present invention;
FIGS. 14a, 14b, 14c and 4d show applications for the visual display screen arrangements of FIGS. 2 to 13.
Referring first to FIG. 1, a highly schematic sectional view through the edge of two prior art liquid crystal display panels 10, 10′ is shown, roughly to scale. Each LCD panel comprises a supporting substrate 20 (typically including a reflector, first glass plate, first polarizing element and backlight where appropriate) onto which is mounted a glass cover plate 40. Sandwiched between the supporting substrate 20 and the glass cover plate 40 is a volume which forms an active display region 30. The active display region 30 contains a plurality of electrodes, as will be familiar to those skilled in the art, together with liquid crystals.
Thus, when placing two LCD panels adjacent to one another, a visible gap is clearly discernable between the two active display regions. A significant “seam” is unacceptable and prior art arrangements are accordingly unsuitable for creating larger screens from an array of smaller screens placed together.
FIGS. 3 and 5 show the edge geometry in more detail. Again, features common to FIGS. 1, 2, 3 and 5 are labelled with like reference numerals. As seen in FIG. 3, the cover plate assembly 140 can be notionally divided into two separate regions, a generally planar region 142 and a refracting region 144 which is convex in the example of FIG. 3. The cover plate assembly 140 overlays a main display area 25 having a display region 30 which may be Liquid Crystal, Polymer, Bi-stable (I-ink™ or the like. Within the display region is a plurality of pixels 55a, 55b, 55c, whose arrangement will be described in more detail below. Light from the pixels 55a, arranged away from the optically inactive area 60, which includes the edge seal and edge protection, is substantially unaltered in direction by passage through the planar region 142 of the cover-plate assembly 140. This is shown in FIG. 3 by the rays 72. By contrast, light from pixels 55b, for example, which are closer to the optically inactive area 60, is bent by the refracting region 144 of the cover plate assembly 140, as seen in rays 74.
Region C is an image repetition zone. This is provided immediately adjacent to the inactive region area 60. The purpose of this will be described in connection with FIGS. 10a and 10b below. The remainder of the main display area, A, contains the relatively lower resolution pixels 55a. It is to be understood that, in the preferred embodiment, the pixel spacing of the pixels 55a may be the same as the spacing in a ‘normal’ LCD panel, with the pixels 55b, 55c being more closely packed. For ease of manufacture, however, it is instead possible to use a display area 25 in which each separate pixel is equally spaced, and either to electronically compress the image, or, for example, to address two adjacent pixels in the region A in tandem, whilst addressing each separate pixel in the regions B and C separately. In the latter arrangement, each pair of pixels in the region A acts as a single, larger pixel.
Using Snell's law, the geometry of the radiused edge 150 can be estimated. FIG. 5 shows the geometry in a “worst case” scenario, with glass, having a low refractive index, provided as part of the cover plate assembly 140. It is stressed here that the dimensions provided are by way of example only and that the dimensions are widely variable dependent upon the application and materials. It will be appreciated that the higher the refractive index, the thinner the cover plate assembly needs to be for a given width of optically inactive area 60. Using 0.7 mm thick glass (typical for LCDs), having a nominal refractive index of 1.5, and with the radiused edge 150 having a radius of 0.5 mm, the lateral distance over which the cover plate assembly 140 must be curved is 0.38 mm. The edge and seal width at the height of the liquid crystal is over 220 μm, as opposed to 80 μm without edge shaping. For a screen resolution of 75 dots per inch (30 dots per cm), only the pixels immediately adjacent to the optically inactive area 60 need to be of closer line spacing.
FIG. 6 shows a further sectional view of the arrangement of pixels within the active display region and it will again be noted that the pixel resolution increases with proximity to the optically inactive area 60. The arrangement of FIG. 6 also includes so-called repeat pixels whose purpose will be explained further in connection with FIGS. 10a and 10b. FIG. 7 shows, by contrast, a schematic plan view of the pixel arrangement in the arrangement embodying the invention, with horizontal lines representing the rows of pixels. In FIG. 7, the repeat pixels of FIG. 6 are not shown.
FIGS. 8a and 9 show an exemplary image formed in the active display regions of each of the two LCDs of FIG. 2, without and then with the lenses in place respectively. It will be noted from a comparison of FIG. 8a and 9 that the image in the active display region is compressed as it approaches the inactive region, and that the lens compensates for the visible gap and the compressed image such that the gap substantially disappears and the image as actually seen by a user is undistorted.
To verify the technique, an image such as is shown in FIG. 8a was generated and printed onto white paper. Two perspex blocks, each having a bevelled edge, were placed together so that the bevelled edges abutted. The printed paper was backlit through a light box and the visible gap shown in FIG. 8a reduced to the thin, almost invisible line of FIG. 9.
The dimensions used were as follows: thickness of perspex blocks=9.2 mm; radius of curvature of edge=4.6 mm, subtending an arc of 50°; refractive index of perspex=1.43. The image was formed with a 3.0 mm black gap surrounded by 0.9 mm repeat strips (as explained below in connection with FIGS. 10a and 10b) and 2.2 mm compressed strips. This schematic image structure is shown in FIG. 8b.
The foregoing description has discussed refraction of light rays incident generally perpendicular to the planar part of the cover plate assembly 140, that is, when the screen is viewed face on. When an observer moves out of perfect alignment to the screen, by contrast, the gap becomes more visible if certain precautions are not taken. This may be explained with reference to FIGS. 10a and 10b, which show a ray diagram for the cover plate assembly 140 of the panel arrangement of FIG. 2 when viewed perpendicular to the plane of the panel and, separately, at an angle thereto respectively. Consider first the virtual point A in FIG. 10a. When viewed directly from above, this virtual point is actually being displayed by a pixel at the location A′ within the active display region 30. When the observer moves to the right, however, as shown in FIG. 10b, the virtual point a then falls behind the join defined by the protective side walls 50 of each of the two LCD panels 100, 100′. In order to overcome this, part of the image displayed in the active display region 30 of the LCD panel 100 is repeated in the active display region 30′ of the other LCD panel 100′. The virtual point A in FIG. 10b is now displayed by the pixel at location A″ in the right-hand LCD panel 100′ instead. In other words, in the active display region 30′ of the right-hand LCD panel 100′, the edge is projecting a section of what is normally seen from the active display regain 30 of the left-hand LCD panel 100.
By repeating the image on either side of the join where the protective side walls 50 of the LCD panels 100, 100′ abut, the observer's eye does not register the join even when viewing the screen away from the perpendicular. Using such an arrangement, the angle of viewing of the screen before the join becomes visible can be increased from about 8° about an axis perpendicular to the display region 30, up to about 20° either side of that axis. The amount of repetition is variable. For example, the test arrangement of FIG. 8b employs a 40% repetition, that is, the upper 40% of the image in the lower compressed strip B is repeated in he upper repeat strip and vice versa. Increasing the percentage gives better viewing angles but results in a narrower gap.
Referring now to FIGS. 11a to 11c, different arrangements for refracting the light around the inactive region of the LCD are shown. In the arrangement of FIG. 11a, two materials are employed, with a low refractive index material 220 formed over the radiused edge 150. As previously explained, the higher the refractive index, the thinner the lens needs to be for a given width of inactive region.
To achieve a higher degree of refraction, two interfaces may be used as well or instead. For example, a region of low index of refraction material 230 may be employed adjacent to the supporting side wall, as shown in FIG. 11b. In FIG. 11c, an undercut edge may be provided to deflect the rays. The particular choice of shape will depend upon the maximum degree of reflection deemed permissible, amongst other considerations. The region defined by the undercut edge of the cover plate assembly 140 may, for example, be filled with material such as a resin. In yet an alternative arrangement, the material could be situated directly on the active display, in an analogous manner to that shown in FIG. 11b. In general, to minimize the thickness of the cover plate assembly 140, it is desirable that the translucent part be formed of a material such as a relatively heavy flint glass having a refractive index in excess of 1.6. Other materials such as perspex or a lightweight glass coated plastics material could be employed instead, to save costs, but, having a lower refractive index, would need to be relatively thicker.
The glass lower layer 500 and the polarisation/compensation material of the thin sandwich layer 510 are, as may be seen, of ‘standard’ shape without any means to cause light to bend. Instead, it is the plastic upper layer 520 which contains the curved edge that causes light refraction.
Turning finally to FIGS. 14a-14d, some exemplary applications for the arrangements of FIGS. 2-13 are shown. FIG. 14a shows a first mobile telephone 300 having a body part 305 with a keyboard, and a screen formed from two LCD screen parts 310 and 320, each of which is generally of similar dimensions to the keyboard. The screen parts are foldable relative to one another by means of a hinge (not shown) such that, in a first, closed, position, the cover plate assembly of one contacts that of the other. This protects the screen parts 310, 320 when not in use. In a second, open position as shown in FIG. 14a, the two screen parts are folded away from one another. By addressing each screen part 310, 320 differently (which technique will be familiar to those skilled in the art), a composite image as seen in the Figure can then be forced and this extends across the join 325 to fill the whole screen.
FIG. 14b shows a second mobile telephone 330 with a foldable screen containing three screen parts 340, 350, 360. The central screen part 350 is mounted in fixed relation to the body of the mobile telephone, and the left and right-hand parts 340, 360 are foldable relative thereto. Thus, in a first position, the left-hand screen part 340 folds against the central screen part 350 such that the cover plate assemblies thereof face one another. After that, the right-hand screen part 360 is folded over the back of the left-hand screen part 340 so that the cover plate assembly of the right-hand screen part 360 faces the supporting substrate 2C of the left-hand screen part 340. When opened, the composite screen has three parts with two joins 370, 380. The principle of a three-part screen arrangement is exactly the same as has been described with the one and two-part screen arrangements of FIGS. 2 to 13. Obviously, the central screen part 350 requires shaped edges on both sides. In that case, i. may be desirable to have the driver circuits to address the central screen part 350 underneath the supporting substrate, but this is not a problem since the central screen part 350 is mounted upon the body of the telephone.
FIG. 14c shows a foldable touch screen device 390 which has a touch screen keyboard 400. This device is capable of lying flat upon a table when unfolded and is thus less intrusive than a laptop computer. The device 390 can also be used as an electronic book and in that case the virtual keyboard may be switched off. A disk drive 410 might also be provided to allow information to be uploaded and downloaded.
Finally, FIG. 14d shows a typical laptop computer similar to the Psion® Organiser™. Again, the screen is in two parts and is foldable as with the mobile phone of FIG. 14a.
Although the foregoing description has focussed upon smaller scale screens, and in particular liquid crystal displays, it is to be understood that the invention is not so limited. For example, bistable or electroluminescent displays are equally susceptible to the use of a material, coating or structural formation that will allow bending of light to minimize panel gaps between adjoining displays. Furthermore, the use of multiple television or video screens placed next to one another to form a giant display for large public areas such as shopping malls, is known. Typically, each video or television screen has a diagonal screen dimension of around 600 mm. Because of the additional hardware necessary around the screen, there is usually a significant gap between adjacent screens. This can again be minimised using lenses to form a pseudo-continuous display. In this case, image compression might be achieved electronically without moving pixels. Such an arrangement also illustrates that the number of smaller screens that can be used to make up the single, composite larger screen is essentially unlimited.
image display means having a display area;
a translucent cover member arranged to cover the display area and having a first cover member edge, the display area having an edge extending towards but not as far as the said first cover member edge;
characterised in that the cover member: (a) has a generally planar portion covering at least a part of the display area and being arranged to pass rays of light substantially without bending such that the majority of the display area as viewed externally of the arrangement and through the said generally planar portion, appears substantially undistorted; (b) has a refracting portion which includes the said first cover member edge, the said refracting portion being arranged to bend only those rays of light emanating from at or adjacent to the edge of the display area, such that the said display area as viewed externally of the arrangement and through the said refracting portion, appears to extend substantially as far as the edge of the cover member; and (c) is formed as a laminar construction: and (d) comprises a lower layer adjacent the display area and formed of a first material, an upper layer formed of a second, different material, and a polarisation/compensation layer sandwiched between the upper and lower layers.
second image display means having a second display area;
a second cover member arranged to cover the second display area and having a second cover member edge located in use adjacent to the said first cover member edge, the second display area having an edge extending towards but not as far as the said second cover member edge, the second image display means being arranged to provide a second image within the second display area which is visible through at least a part of the said second cover member;
the second cover member having: (a) a second generally planar portion covering at least a part of the second display area and being arranged to pass rays of light substantially without bending such that the majority of the second display area, as viewed externally of the arrangement and through the said second generally planar portion, appears substantially undistorted; and (b) a second refracting portion which includes the said second cover member edge, the said second refracting portion being arranged to bend only those rays of light emanating from at or adjacent the edge of the second display area such that the said display area, as viewed externally of the arrangement and through the said second refracting portion, appears to extend substantially as far as the edge of the second cover member.
3. The arrangement of claim 2, further arranged to generate a part of an image both within the first display area and adjacent the first cover member edge, and also within the second display area and adjacent the second cover member edge.
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Patent number: 6927908
Patent Publication Number: 20040051944
Assignee: Seamless Display Limited (Southampton)
Inventor: Bernard Harry Stark (London)
Application Number: 10/432,663
Current U.S. Class: With Reflector Or Additional Screen (359/449); Unitary Sheet Comprising Plural Refracting Areas (359/454); Rear Projection Screen (359/460); Tiling Or Modular Adjacent Displays (345/1.3); Modular Image Display System (348/383)