GB2429538A - Proctor arrangement for portable electronic device - Google Patents

Abstract

A projection arrangement 102 for use with a portable electronic device 100 having a transmissive or transflective display 110, 144 comprises an aperture 136 arranged to receive the display 110, 144 of said portable electronic device 100, a light source 104, 130 for illuminating the display 110, 144 and projection optics 108, 138, 140 for projecting an image of the display onto a screen 112.

Description

Projection Arrangements for Portable Electronic Devices The invention

relates to projection arrangements for use with portable electronic devices, and to portable projection systems.

The prior art in this technical field can be broken down into four types of design: 1. Portable devices having near-to-eye displays providing a virtual picture in wide field of view for the user. Examples are US5,629,806 (Fergason, James L., US, 1994), US5,970,418 (Budd, Russell Alan, US, 1996).

2. Projectors built into the display device including one display panel for direct viewing and another for projection: for example US6,489,934 (Judah Klausner, US, 2000).

3. Distinct front projector design that is actually a complete portable projector which may be used with a portable device: for example US2, 002/0063855 (John W. Williams, US, 2000).

4. Projectors that share a display panel with a direct-view device, as in the present invention. This alternative has clear advantages of cost and simplicity. Prior art in this area is described in detail below.

A disadvantage of a near-to-eye display is that it can be viewed only by a single user and he or she has to hold the device close to the eye.

The disadvantage of the second type of design is the additional power consumption as well as the extra physical size and cost. Another disadvantage that it shares with the third type of design is that a separate microdisplay panel is required to project the enlarged picture which increases the system cost.

The last type of design is more like the present invention. There are some published patents which disclose projection attachments that share the same display panel with a direct-view device to reduce the cost.

US 5,801,793 (Sadeg M. Fans, US 1994) discloses a backlighting construction for use in a computer-based display system. The display system uses a hinge-connected lighting panel element 21 to allow a display monitor of a laptop PC 2 to be used as a part of the projection system (as shown in Figure 1 of the present specification).

Element 21 is like a conventional backlight unit. As shown in the enlarged cross-section in the circle, the element 21 consists of a light guide panel 92 with two diffuser films 94 and 96 on top and bottom. A light source 91 provides backlight illumination for direct viewing of the LCD panel 10. On the top of the LCD panel 10, there is a thin light focusing optics, i.e. Fresnel lens. When the device (say laptop) is used for direct view, the element 21 will be completely closed together with the LCD panel inside frame 3.

When the display panel is used in a projector, the backlight panel together with the reflector need to open up at 45 degrees working as a mirror to reflect the light from light source 61, 68 (powered by lead 71). The reflected and diffused light will then be focused to the projection optics 81, 82 (supported by supporting members 62, 83, 84), through the LCD panel to generate the picture on a screen 89 viewed in a direction indicated by glasses 111. A disadvantage of this system is the light efficiency because the illumination light is reflected by reflector 90 and passes through the light guide panel 92 and the two diffusers 94 and 96 twice in the projection mode. Also, the whole system is bulky for portable use, and its use is limited to computers, including laptops, and when the display panel is used for projection, the user has to be careful with the exposed LCD panel.

WO 99/63395 (G J Woodgate, Sharp Corp, 1998) discloses a projection display comprising a transmissive spatial light modulator, an illuminator for illuminating the modulator from the front, and a hologram at the rear of the modulator for imaging and reflecting back through the modulator light from the illuminator received through the modulator. The hologram also allows the modulator to be used for direct viewing.

Because the light passes through the modulator twice, the system efficiency will be much lower than in systems where the light passes through the modulator once. Also, the hologram beneath the modulator has to be aligned carefully to the optical system, as well as to the modulator which causes manufacturing difficulties.

WO 90/06537 (B. Gerhard, Kodak, US, 1989) discloses an overhead projector working together with a LCD panel and a traditional transparent slide. In this case it is the projector rather than the LCD which has a dual function, being capable of projecting

I

images from transparencies or from an LCD panel. The LCD panel in this case is not used for direct viewing.

A first aspect of the invention provides a projection arrangement for use with a portable electronic device, and a portable projection system as set out in accompanying claims 1 to 46.

The invention may provide the following advantages: Cost is reduced because only one panel and driving circuit is required for both direct view and projection mode.

No electronic interfacing is required between the information device and the projector.

The projection system works in the transmission mode. So the light only passes through the transparent or transfiective panel once, leading to smaller losses. (A transfiective panel is a panel which can operate in both transmissive and reflective modes. This may be achieved, for example, by dividing each pixel into two parts, with one part working in transparent mode and the other working in reflective mode.) Also, compared to a system using a reflective mode, efficiency is higher because of diffuse scattering from reflective direct-view panels.

The same attachment may be adapted for use with a number of different devices.

The projected image of the display can be seen by many users in projection mode.

Some devices which are suitable for the invention are: Communication devices, including mobile telephones and videophones Personal digital assistants (PDAs) DVD players

Portable televisions

Medical and scientific instruments Game consoles

Portable computers

Other devices with display panel such as a GPS navigator, etc. An advantage of the projection system over portable LED-powered projectors using small (for example, <1") LCD or micromirror panels is that because the display panel is larger, more space is available to pass light through the system. In other words, the system etendue is larger. A full discussion of the concept of etendue and its implications for projector design can be found in Projection displays, by Stupp and Brennesholtz (Wiley 1999). The advantage of large system etendue is particularly important for LED-illuminated projectors because the light concentration (measured, for example, in lm Sf1 mm2) for LED sources is much smaller than for discharge lamps.

This means that a large system etendue is needed for an LED-illuminated projector of high brightness.

A second aspect of the invention provides a projection arrangement as set out in accompanying claims 47 to 52.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows an arrangement described in patent US 5,801,793 (Sadeg M. Fans, US 1994) which describes a hinge-connected lighting panel working in a projection system as described above; Figure 2a is a cross-sectional diagram illustrating a configuration of an embodiment of the invention including an LED light source; Figure 2b shows the arrangement of the LED array of Figure 2a plus its plastic hexagon lens; Figure 3 shows a way of sliding the cover of the LCD panel of Figure 2a; Figure 4a is a crosssection of a double-faced LCD panel structure; Figure 4b shows the circled area of Figure 4a in greater detail; Figure 5 shows a projection system with an optic y converging curved mirror as part of the projection optics; Figure 6 is a diagram illustrating a projection attachment with a telescopic structure, shown in both extended and contracted configurations; Figure 7 is a cross-sectional diagram illustrating a projection attachment using a discharge lamp as the light source; Figure 8 illustrates the idea of exposing the liquid crystal panel for projections; Figure 9a shows the display of a portable electronic device, with rotating polarisers; Figure 9b shows the display of a portable electronic device, with sliding polarisers; Figure 10 is an illustration of a projection attachment system using a reflective mode polariser; Figure 11 is an illustration of a projection attachment system using a separated backlight panel as the projector light source; Figure 12 is a diagram illustrating the use of a polarization conversion optical system (PCOS); Figure 13 is a diagram showing an LCD panel built with a hinged cover and its position when the panel is used for projection (in broken line); Figure 14 shows one possible configuration of a projection lens that can be swung into or out of position above a display device; Figure 15 shows a folding projection attachment; Figure 16 shows a possible aperture design which allows the beam shape of the illumination light to be changed; Figure 17 shows a hinged, telescopic structure to further minimize the dimension of the arrangement.

Figure 18 shows a projection arrangement which comprises a built-in display panel.

The optical layout of the first embodiment is shown in Figure 2a. Figure 2a also shows how a portable device 100 such as a mobile phone is inserted into a projector attachment 102 to form a complete projector.

The attachment as shown in Figure 2a comprises an LED array 104, Fresnel lens 106 (having focal length fF=65 mm) and projection lens 108 ( having focal length fp50mm, and aperture F/# = 1.4). The LEDs are LXHL-LW6C (from Lumileds) providing 120 im (lumens) white light per unit. Each LED is provided with a hexagon plastic collecting optics 109 plus its supporters (P/N 129/128 from Polymer Optics Ltd), which has about 80% collecting efficiency. The display panel 110 is located right behind the Fresnel lens 106, and the function of Fresnel lens 106 is to direct light into the projection lens 108 to increase the brightness on the screen 112.

The display panel 110 that we use here is a full colour standard QVGA (Quarter Video Graphics Array 320x240) LCD panel with a low haze (or diffusion) transparent backlight 114 and slideable cover 116. The cover 116 is slid out when the panel is used for projection, as shown in Figure 3. The LCD is transmissive mode with size of 2.4 inch diagonal and has two polarisers 115 and 117. We therefore created a LED array 104 shown in Figure 2b together with the collecting optics 109. For the LED collecting optics 109, the cone angle of the beam where the light intensity drops to half from the centre is about 6 degrees. So the LED array 104 is located about 50mm away from the display panel 110 to get about 80% of the light. Positions and orientations of the optics are adjusted to give uniform illumination of the LCD panel 110.

The type of element used for a transparent backlight 114 is well known, and commonly used in front-lights for reflective displays. Suitable elements are described in US 05860722 (P. K. Tai, Clio Technologies, US, 1999), US 06636283 B2 (T. Sasagawa, Mitsubishi Denki Kabushiki Kaisha, Japan, 2003), and US 2003/0160911 Al (M Kano, Japan, 2003), etc. A typical design is given in US 6,636,282 and shown in Figures 4a and 4b. Light from a source 118 is introduced from one edge of a waveguide 119 and total internal reflection causes it to propagate along the guide. Prism structures 120 on the top surface cause some light to be reflected out of the waveguide as shown. Surface 123 may be coated with metal or a multilayer coating to aid this process. There are four internal reflection surfaces, surfaces 121, 122, 123 and the bottom surface 124. The function of surface 122 is to reduce the divergent angle of the light wave being guided, while reflection from surface 121 will guide the light beam further along the optical guide 119.

An important benefit of transparent lightguides for the embodiment described herein is that they allow a separate illumination system to be used for projection without removing the transparent lightguide used for direct viewing.

The screen 112 is located at about 400-500 mm from the projection lens 108. By using lens imaging equation: 1/fe = 1/d2 + 1/d3, the distance d2 in Figure 2a is calculated as about 57mm. The picture on the QVGA panel is enlarged about 50 times in terms of area.

The optics used in the system are off-the-shelf products. The light output on screen 112 is more than 10 im. The system can give more light output with optimised elements.

As an alternative to using a slideable cover 116, the "Double-faced TFTLCD" panel developed by SHARP (T. Taguchi, K. Tsuda, et, ac., IDW (International Display Workshop) 04, page 75-78, 2004) may be used.

The display panel has a single LC (liquid crystal) panel and transparent lighting system.

It works not only as a transmissive type LCD from one side but also as a reflective type LCD from the other side. A simplified diagram of the double-faced LCD panel is shown in Figures 4a and 4b including the transparent backlight and a reflective polariser 126. The advantage of this display panel is that in a foldable phone, it removes the need for a sub-display panel plus its separate backlight as well as a driving circuit. Another advantage of this type of display is that it can be attached to a projection attachment immediately to give an enlarged picture without the need for either a slideable cover or slideable LCD panel. This is because the rear face of the LCD is already visible for use as a secondary display.

Figure 5 shows an alternative projection arrangement which comprises a light source 130, light collecting optics 132, a first Fresnel lens 134, a slot 136, a curved converging mirror 138 and a second Fresnel lens 140. These components are housed within a case 142. The slot 136 is sized to receive the LCD display panel 144 of a portable electronic device.

There are two advantages to the converging mirror 138. One is the potential low cost for mass production. The second is that it can, unlike the glass lens optical system, fold the optical path to save space. The converging mirror 138 may cooperate with extra simple optics, such as the second Fresnel lens 140, to act as the projection lens.

Figure 6 shows a projection arrangement having a telescopic case comprising first, second and third parts 144, 146 and 148 respectively. The first part 144 contains a light source 150 and light collecting optics 152. The second part 146 contains a Fresnel lens 154, and defines a slot 156 for receiving a display device. The third part 148 contains a projection lens 158. The projection arrangement is shown in the top part of Figure 6 in its extended configuration, and in the bottom part of Figure 6 in its contracted configuration.

In this embodiment the projection attachment is telescopic, so that when it is not in use it takes up very little space. When the attachment is not in use, the whole system can be folded to reduce its size by a factor of approximately 3, as shown in the lower part of Figure 6.

In Figure 7 a discharge lamp is used rather than LEDs. An advantage of a discharge lamp over LED and other light sources is that a discharge lamp provides a much more concentrated light source (smaller etendue), allowing higher optical efficiency. A discharge lamp with a parabolic reflector that provides a well collimated light beam output can be used in the above embodiments as the light source instead of the LEDs 104 plus the light collecting optics 109.

Figure 7 shows a projection attachment 162 using a discharge lamp 160 with an elliptical reflector 164 working together with an integration rod 166 incorporating a reflector. Because of the elliptical reflector 164, the light emitted from the arc 160 is focused into the entrance of the integration rod 166. As light passes through the rod 166, there are many internal reflections which results in better uniformity rather than an image of the arc 160 itself. The integrator rod 166 is a well-known component of projector systems and is described in detail in the book by Stupp and Brennesholtz mentioned above. Also, the shape of the exit aperture can have the same aspect ratio as the display 168 to increase the fill factor in order to achieve the maximum optical efficiency. The lens 170 could be a Fresnel lens. The mirror 172 could be a converging mirror. The projection attachment 162 also includes optics 174 between the exit of the integration rod 166 and the display 168, and includes a projection lens set 176 after the mirror 172 for projecting the final image of the display 168 onto a screen (not shown).

The projection attachment 162 is also provided with a slot 178 arranged to receive and support the display 168 so that it is illuminated by light from the integration rod 166.

The display 168 can be the LCD display of a portable electronic device such as a mobile phone, PDA or portable television.

Figures 8 and shows the embodiment of Figure 2a with some modifications. Reference numerals in Figures 8 and 10 which also appear in Figure 2a represent the same components.

Normally, a LCD panel consists of a LC panel and two polarizers closely attached on both sides. The output polarizer will absorb nearly 100% of the light when the panel (or certain pixels) is in its black state, while the input polarizer absorbs 50% of incident unpolarised light. In projector systems, where the light intensity is high, this may cause thermal damage to the LC panel between these two polarizers, or may lead to the liquid crystal being heated to its isotropic point, where it ceases to function.

This problem can be solved by placing polarisers some distance away from the LC panel. For example, the polarisers can be placed near the light source (polariser 180 in Figure 8), and near the projection lens (polariser 182 in Figure 8). Unfortunately this prevents the LCD panel from being used for direct viewing. There are a number of possible solutions to this problem: (a) The LCD may have an entrance polariser 117 attached to it in addition to a distant polariser 180, as shown in Figure 10. Because nearly all light of the appropriate polarisation is absorbed by the additional distant polariser 1 80 in the projection mode, little heating of the LCD 110 is caused by the entrance polariser 117 attached to the LCD. (Unfortunately this strategy of having two polarisers does not work for exit polarisers, since if there is an exit polariser attached to the LCD in addition to polariser 182 in Figure 8, then the attached polariser will absorb light.) (b) An exit polariser may be attached to the LCD panel when it is used in direct view, and removed for the projection mode, possibly in addition to other components such as backlights. Figures 9a and 9b illustrates this possibility. Figures 9a and 9b each show the display of a portable electronic device having the same components, represented by the same reference numerals, as the display of Figure 3. Each display comprises a cover 116, a transparent backlight 114, an entrance polariser 117, a liquid crystal panel 110, and an exit polariser 115. These components are arranged in a sandwich fashion as shown in Figures 9a and 9b. In Figure 9a the two polarisers 117 and 115 are hinged about a pivot 184 so that they can be rotated away from the LC panel 110 as indicated by the dotted lines in Figure 9a. When the polarisers 117 and 115 are in the projection position indicated by the dotted lines in Figure 9a light passes through the LC panel 110 without passing through the polarisers 117 and 115, thus avoiding heating of the LC panel 110 in projection mode. When it is required to use the LC panel 110 for direct viewing, the polarisers 117 and 115 are swung back into position so that they sandwich the LC panel 110. Figure 9b is the same as Figure 9a except that the two polarisers 117 and 115 are arranged to be slidably removable from the LC panel 110. In Figure 9b the polarisers 117 and 115 are shown after having been slidably removed so that they no longer cover the LC panel 110.

(c) The exit polariser may be reflective, so that it absorbs little light and causes little heating. Note that the double-faced LCD of Taguchi et a! has this type of polariser.

The so-called mirror displays' from Samsung and Sony also have this feature.

Figure 11 shows an embodiment which is a modification of the embodiment of Figure 2a. In Figure 11 components which are the same as those in Figure 2a are represented by the same reference numerals.

The embodiment of Figure 11 uses a backlight panel 186 that provides at least partially collimated light. One example of such a backlight panel design can be found in M. Shinohara's paper (M. Shinohara, et. a!, "Curved prism array for controlling directivity of LED backlight", Page 665, ID W' 03 Conference, 2003) in which a curved prism array guides the LED light out of the surface with well controlled angle range. Comparing to Figure 2a, the backlight panel 186 can be used to replace the LED source 104 and its collecting optics 109. Furthermore, the backlight panel 186 can be put very close to the Fresnel lens 106 to save space as shown in Figure 11. The compact dimensions provide a clear advantage. The collimated backlight 186 is used only in projection mode. Note that, the transparent backlight 114 of the LCD panel (used for direct viewing) and other elements like polarisers 117 and 115 (shown in Figure 3) remain unchanged.

Polarisation conversion optical systems (PCOS) are often used in LCD projectors to increase light efficiency by converting light from an unpolarised source (such as a discharge lamp or LED) to polarised light. The principle is described in the book by Stupp and Brennesholtz mentioned above.

Figure 12 shows how the embodiment of Figure 2a can be modified to use PCOS. A polarization beam splitter 188 splits the unpolarised light beam into two linear polarization light beams with their polarization directions perpendicular to each other.

The orientation direction of a half wave plate 190 is at 45 degrees to the polarization direction of the incoming light. Its effect is to rotate the plane of polarisation of the transmitted beam so that all light emerging from the system (on the right of Figure 12) has the same linear polarisation. A mirror 192 reflects light reflected by the beam splitter 188. Almost no light is therefore absorbed by the entrance polariser 117 of the LCD 110. There are several advantages of this arrangement. The efficiency of the system is increased. Since LEDs are more widely spaced than in designs with no PCOS, thermal management (heat sinking) is easier to arrange. Cost is reduced because fewer LEDs are needed for the same optical power. Finally, because little light is absorbed on the entrance polariser 117, heating of the LCD 110 is minimised.

Polarization conversion systems in the invention are not limited to the type described above. For example, the polarization conversion systems described in British Patent Application No. 0025252.8 and Japanese Patent Application No. 01-260882 (J.

Karasawa, 1989, Epson Corp), etc may be used.

A wide bandwidth half wave plate can be inserted between the PCOS and the LCD display panel 110. Then no matter what direction that the polariser 117 on the LCD panel 110 points, by rotating the half wave plate, one can always make the polarization direction of the incident polarization light parallel to the input polariser on LCD panel 110.

The Dual Brightness Enhancement Film (DBEF) made by 3M Company can also be used right after the light source to recycle the polarization light.

A direct view display requires light to emerge with a wide range of ray angles so that the display can be viewed from any angle. However, projection displays require light to emerge from the light modulator with a narrow range of ray angles so that the light can be directed into a projection lens. This makes it difficult to use a single light source for both applications. Also, even when separate light sources are used for projection and direct viewing, lack of scattering in the liquid crystal display may lead to unwanted concentration of light in certain directions. In displays used solely for direct viewing, this is often prevented by including diffusers into the display. This is not possible for the present invention because such a diffuser would interfere with the projection mode.

Any of the embodiments described herein may therefore incorporate a switchable diffuser. An example of such an element is a polymer-dispersed liquid crystal (PDLC) cell. Details can be found in "Optical Applications of Liquid Crystals", Chap. 4 (written by F Bloisi and L Vicari), ISDN 0-7503-0857-5, 2003. The PDLC film could be placed either immediately in front of or immediately behind the display panel 110. It can be electronically switched between a state where it diffuses light (for direct viewing) and a state where it does not (for projection).

The switchable diffuser may be switchable between a first state in which it diffuses light so as to make the display have a viewing angle of around 150 degrees, which is suitable for direct viewing, and a second state in which it basically does not diffuse light so that the viewing angle is as narrow as a few degrees and the display is therefore suitable for use in a projection mode.

It is difficult to make a projection attachment according to this invention very small because of the large size of panel needed for direct viewing. A solution to this problem is to use only a portion of the direct-view panel 110 for the projected image. In this case the portion of the display used for projection may have a higher resolution than the rest of the panel. The portion of the display panel used for projection may have an area less than 50% of the total area of the panel 110.

Figure 13 shows an alternative embodiment to that of Figure 3. Components which are the same in Figures 3 and 13 are represented by the same reference numerals. In Figure 13 the slidable cover 116 of Figure 3 is replaced by a hinged cover 194. When the LC panel 110 is used for projection, the hinged cover 194 is opened (as shown by dotted lines in Figure 13) to expose the LC panel 110. The internal surface of the hinged cover 194 can be diffused to help diffuse light when the LC panel 110 is used for direct viewing.

Figures 14a and 14b show a portable projection system in which a liquid crystal display 196 is hingedly connected to a projection lens 198, and also hingedly connected to a projection light source 200. In Figure 1 4a the projection system is shown in projection mode, in which the projection light source 200 is swung into position beneath the LCD 196, and the projection lens 198 is swung into position above the LCD 196. In Figure I 4b the projection system is shown in direct viewing mode, in which both the projection light source 200 and the projection lens 198 are swung away from the LCD 196. The LCD 196 may be provided with a transparent backlight for use in the direct viewing mode.

Figure 15 shows a projection attachment 202 which comprises a light source 204 comprising an LED array and associated optics, a Fresnel lens 206, a slot 208 for receiving a liquid crystal display panel of a portable electronic device, and projection optics 210. These components are housed and supported within a case 212 having two sides 214 and 216 which are parallel, and two ends 218 and 220 which are parallel. As shown in Figure 15 the two sides 214 and 216 are hingedly connected to the two ends 218 and 220, so that the case 212 can be folded down, while maintaining the sides 214 and 216 parallel to each other. The components within the case 212 may also be hingedly connected to the sides 214 and 216, so that when the case 212 is folded down the entire projection attachment 212 takes up considerably less space.

Ultra thin optics, such as a Fresnel lens and holographic optical element (HOE), can be used by the projection system, as well as LED lightcollecting optics to help to minimize the physical dimensions.

The projection attachments described in the various embodiments can be used with different display devices having display panels with different aspect ratios. Figure 16 shows an adjustable aperture 222 which can be used in any of the embodiments so that the beam shape of the illumination light matches the display panel being used. The adjustable aperture 222 is positioned between the light source and the liquid crystal display panel. The adjustable aperture 222 is formed from four adjustable members 224 which are movable as shown by the white arrows in Figure 16, so as to define a rectangular aperture 226. The adjustable members 224 have mirrored surfaces to reflect incident light, thus reducing heating of the adjustable members 224. The mirrored surfaces of the adjustable members 224 may have a concave shape so as to reflect light back to the light source, which helps to recycle the light to increase optical efficiency.

Figure 17 shows a projection attachment which comprises an illumination section 230 and a projection section 232, hingedly connected to the illumination section 230 by a hinge 234. In Figure 17 (a) the two sections 230 and 232 are shown in an open (folded flat) configuration, and in Figure 17 (b) the two sections 230 and 232 are shown in a closed (folded together) configuration. Each of the two sections 230 and 232 is telescopically extendable, so that when in the closed configuration of Figure 17 (b) the two sections may be pulled out into the extended configuration shown in Figure 17 (c) The projection section 232 comprises a slot receiving a transmissive or transfiective display of a portable electronic device, and projection optics including a projection lens for projecting an image of the display. The illumination section 230 comprises a light source, which may be of any of the types described herein. The projection attachment of Figure 17 may have any of the features of any of the other embodiments described herein.

The following paragraphs describe features and modifications which can apply to any of the embodiments described herein.

Any of the embodiments described herein may be provided with vibration means for causing the liquid crystal panel of the display device to vibrate. Because the pixels of the LC panel are magnified on the screen, any black mask of the LC panel may be visible because it is a still pattern. However, the human eye cannot observe a clear pattern when it is vibrating faster than 20 Hz. Therefore, the vibration means may improve the image quality by removing the enlarged black mask image. The vibration means can be a vibration clamp within any of the slots of the various embodiments, for holding the display device and causing it to vibrate. The vibration function on some mobile phones can also be used for the same purpose in projection mode.

The LC panel of any of the display devices can be supported horizontally or vertically, and in any embodiment the support or slot for the display device can be rotatable so as to allow the display device to be rotated. Also, any of the embodiments may have more than one slot, so as to allow the display device to be held in different positions.

In any embodiment, clamps may be provided for holding the display device in position.

A reflective colour filter on Red, Green and Blue sub-pixels is helpful to protect the LC panel from being over heated by the illumination light because it allows one colour light to pass through and reflects, rather than absorbs, the light in other colours. It can also increase the optical efficiency by light recycling.

In any embodiment, an entrance polariser may be located at least 5 mm away from the liquid crystal display.

Many display panels involve a Thin Film Transistor (TFT) structure. When A TFT is illuminated by light intensively, photoconduction may take place which will spoil the image quality in some degree. In order to avoid that, a masking of the TFTs can be fabricated on top of the TFTs to protect them from illumination.

For a light source such as a discharge lamp or LEDs, a cooling system may be required.

A fan and heatsink are normally considered in cooling systems. On the other hand, the display device can work only in a certain temperature range which means the display panel may need to be heated or cooled in some environments. As a solution, the forced air from a fan can be guided onto the display panel to give the effect of either heating or cooling.

Additional functions may be built in to the projection attachment. For example: 1) The power supply for the projection attachment (a battery or a mains electrical supply) may be used to power or to charge the portable device to which it is attached.

2) The projection attachment may incorporate additional data storage (for instance, to store movies or other visual content for projection).

3) The projection attachment may incorporate communication devices, such as a television receiver or a wireless broadband network connection.

4) The projection attachment may incorporate connections to, or sockets for connecting to, other devices, such as portable computers, video recording devices, or DVD players.

5) The projection attachment may incorporate a standard interface such as a USB connector, as well as wireless solutions, i.e. IR, Bluetooth, etc. 6) The projection attachment may incorporate integrated speaker or headphone sockets.

In any embodiment it is also possible for the backlight of the display to be movable so that it can be moved away from the display. This allows the embodiments to be used even when the backlight is not transparent or transfiective. Other components, such as diffusers, may also be movable, so that they can be moved away from the display when used in projection mode.

Figure 18 shows an embodiment in accordance with the second aspect of the invention.

Figure 1 8a shows a projection arrangement 240, which comprises an illumination part 242 which is connected to a projection part 244 by means of a hinge 246. The projection part 244 contains projection optics (not shown) which may have any of the features of the earlier embodiments. Likewise, the illumination part 242 may have any of the features of the illumination arrangements described in the earlier embodiments.

The projection arrangement 240 also comprises a microdisplay panel (i.e. modulator) 248. The microdisplay panel 248 comprises a light modulator array, such as an LCD panel, a LCOS panel (Liquid Crystal On Silicon), a DMD panel (Digital Mirror Device) or the like. Microdisplay panes are normally not bigger than a inch square but are very high resolution (eg. 640x480, 1024x768, 1280x1024, etc). In this embodiment the microdisplay panel 248 is shown housed within the projection part 244, but it could be provided in a different location, for example within the illumination part 242. A connector 250 is provided on the projection part 244 for connection to a mobile device, such as a mobile telephone. This is preferably suitable for connection with a flexible cable which also connects with the a mobile device, but any kind of connector is possible. Again, the connector 250 could be positioned anywhere on the projection arrangement 240.

The microdisplay panel 248 will take a signal from the mobile device through the connector 250. Therefore the panel 248 can be provided with a very simple driving circuit because a ready-to-use signal may be fed in from the mobile device via the connector 250. The panel 248 need not be provided with any complicated signal processing or modulation circuits, but can have simply something like data bus lines, so that the cost is minimised.

An advantage of this embodiment is that it is only necessary for the mobile device to be provided with a suitable connection socket, which can be connected to the connector 250 using a suitable lead. An image provided by the mobile device can then be projected onto a suitable screen in the same manner as in the earlier embodiments.

The built in display panel 248 is not designed for direct viewing, and indeed need not have any electronic driving circuit. That is, the panel 248 need have nothing except any circuit already built into the panel.

Figure 1 8b shows how the illumination part 242 can be folded against the projection part 244, and the illumination part 242 and projection part 244 can then each be telescopically extended as shown in Figure 1 8c, thus allowing an image to be projected onto a suitable screen. The projection part 244 is also provided with a projection lens 252.

Claims (52)

1. CLAIMS: 1. A projection arrangement for use with a portable electronic

   device having a transmissive or transfiective display, the projection arrangement comprising: an aperture arranged to receive the display of said portable electronic device; a light source for illuminating the display; and projection optics for projecting an image of the display onto a screen.
2. 2. A projection arrangement as claimed in claim 1, wherein said aperture, light source and projection optics are arranged in a single unit.
3. 3. A projection arrangement as claimed in claim I or 2, wherein the light source comprises one or more light emitting diodes (LEDs).
4. 4. A projection arrangement as claimed in claim 3, wherein said light source comprises an array of LEDs each provided with collecting optics.
5. 5. A projection arrangement as claimed in claim 3 or 4, which further comprises a polarisation conversion optical system which polarises light from said light source.
6. 6. A projection arrangement as claimed in claim 1 or 2, wherein said light source comprises a backlight that provides at least partially collimated light.
7. 7. A projection arrangement as claimed in claim 6, where said backlight comprises a curved prism array.
8. 8. A projection arrangement as claimed in any preceding claim, which further comprises a Fresnel lens positioned between said aperture and said light source.
9. 9. A projection arrangement as claimed in any preceding claim, wherein said projection optics comprises a converging mirror.
10. 10. A projection arrangement as claimed in any preceding claim, which further comprises a telescopic case containing at least some of the components of the projection arrangement.
11. 11. A projection arrangement as claimed in claim 10, wherein said telescopic case comprises a first section containing said light source, a second section defining said aperture, and a third section containing at least part of said projection optics, wherein said first, second and third parts are arranged to be telescopically moved together when the projection arrangement is not in use.
12. 12. A projection arrangement as claimed in any one of claims I to 9, which further comprises a foldable support structure, which supports at least the light source and the projection optics, and which is foldable between an in-use position, in which the light source and projection optics are supported in positions suitable for projecting an image of the display onto said screen, and a storage position, in which the light source and projection optics are arranged in a more compact configuration.
13. 13. A projection arrangement as claimed in claim 12, wherein said support structure also supports a Fresnel lens.
14. 14. A projection arrangement as claimed in claim 12 or 13, wherein said support structure comprises at least four support members which are hingeably connected to each other, and arranged so that opposite pairs of said support members remain substantially parallel with each other in both said in-use and said storage positions.
15. 15. A projection arrangement as claimed in any one of claims ito 9, which comprises a support structure which is both telescopic and foldable.
16. 16. A projection arrangement as claimed in claim 15, which comprises: an illumination section which supports at least said light source; and a projection section which supports at least part of said projection optics, wherein said illumination section and said projection section are both telescopically extendable, and wherein said illumination section and said projection section are hingedly connected to each other.
17. 17. A projection arrangement as claimed in any preceding claim, wherein said light source comprises a discharge lamp.
18. 18. A projection arrangement as claimed in any preceding claim, which further comprises an integration rod for directing light from said light source to said aperture.
19. 19. A projection arrangement as claimed in any preceding claim, which further comprises an entrance polariser located at least 5 mm away from said display when received in said aperture.
20. 20. A projection arrangement as claimed in any preceding, which further comprises an adjustable aperture arranged between the light source and the projection optics, which can be adjusted to correspond with the different aspect ratios of different displays.
21. 21. A projection arrangement as claimed in claim 20, wherein said adjustable aperture is formed by an adjustable frame having mirrored surfaces, which reflect, rather than absorb, light from said light source to increase the optical efficiency by recycling the light.
22. 22. A projection arrangement as claimed in any preceding, which further comprises vibration means arranged to cause vibration of said display.
23. 23. A projection arrangement as claimed in any preceding claim, wherein said aperture is formed by a slot adapted to receive said display.
24. 24. A projection arrangement as claimed in claim 23, wherein said slot is rotatable between two substantially orthogonal positions, thus allowing said display to be supported in two different substantially orthogonal positions.
25. 25. A projection arrangement as claimed in any one of claims I to 22, which comprises two slots each arranged to receive said display, said slots being arranged substantially orthogonally to each other, so that said display can be received in two substantially orthogonal positions.
26. 26. A projection arrangement as claimed in any preceding claim, which further comprises a power supply, and also further comprises power transfer means for transferring electrical power from the power supply to said portable electronic device.
27. 27. A projection arrangement as claimed in any preceding claim, which further comprises data storage means for storing data, and data transfer means for transferring data between said data storage means and said portable electronic device.
28. 28. A projection arrangement as claimed in any preceding claim, which further comprises communication means for receiving signals from an external source and/or transmitting signals to an external location.
29. 29. A projection arrangement as claimed in any preceding claim, which further comprises at least one plug or socket for connection with an external electronic device other than said portable electronic device.
30. 30. A projection arrangement as claimed in any preceding claim, which further comprises a speaker or headphone socket for providing audio output to a user.
31. 31. A portable projection system comprising a projection arrangement as claimed in any preceding claim, and a portable electronic device having a transmissive or transfiective display sized to fit within the aperture of the projection arrangement.
32. 32. A portable projection system as claimed in claim 31, wherein said display comprises a transparent backlight.
33. 33. A portable projection system as claimed in claim 31 or 32, wherein said display is provided with a cover which is movable between a first position in which it covers and protects said display, and a second position in which said display may be illuminated by said light source.
34. 34. A portable projection system as claimed in claim 33, wherein said cover is slidably movable between said first and second positions.
35. 35. A portable projection system as claimed in claim 33, wherein said cover is hingeably connected to said display, so as to be hingeably movable between said first and second positions.
36. 36. A portable projection system as claimed in claim 35, wherein said cover is hingeably connected to said display so as to be rotatable about an axis which is substantially parallel with the plane of said display, although not necessarily lying in that plane.
37. 37. A portable projection system as claimed in claim 35, wherein said cover is hingeably connected to said display so as to be rotatable about an axis which is substantially perpendicular to the plane of said display.
38. 38. A portable projection system as claimed in any one of claims 31 to 37, wherein said display is provided with an exit polariser which is removable thus avoiding overheating when the display is used in a projection mode.
39. 39. A portable projection system as claimed in any one of claims 31 to 37, wherein said display is provided with a reflective exit polariser.
40. 40. A portable projection system as claimed in any one of claims 31 to 39, wherein said display is attached (directly or indirectly) to the light source of the projection arrangement, and the light source is movable between a first position in which it is located behind the display so that it can illuminate the display, and a second position where it is not immediately behind the display.
41. 41. A portable projection system as claimed in any one of claims 31 to 40, wherein said display is attached (directly or indirectly) to the projection optics of the projection arrangement, and the projection optics are movable between a first position in which they are located in front of the display so that they can project an image of the display onto a screen, and a second position in which they are not immediately in front of the display.
42. 42. A portable projection system as claimed in any one of claims 31 to 41, wherein said display comprises a Thin Film Transistor (TFT) structure, and the TFTs within said structure are masked to protect them from illumination by said light source.
43. 43. A portable projection system as claimed in any one of claims 31 to 42, wherein said display comprises a switchable diffuser, which is switchable between a first state in which it diffuses light so as to make the display suitable for direct viewing, and a second state in which it does not diffuse light so as to make the display suitable for use in a projection mode.
44. 44. A portable projection system as claimed in any one of claims 31 to 43, which is arranged so that an image of only a portion of said display is projected onto said screen.
45. 45. A portable projection system as claimed in claim 44, wherein said portion of the display has a higher resolution than the rest of the display.
46. 46. A portable projection system as claimed in any one of claims 31 to 45, wherein said display is provided with a backlight which is movable between a first position in which it substantially covers said display, and a second position in which it does not cover said display so that the backlight does not lie in the path of light from the light source of the projection arrangement when illuminating said display.
47. 47. A projection arrangement for use with a portable electronic device, the projection arrangement comprising: a display panel; a light source for illuminating the display panel; projection optics for projecting an image of the display onto a screen; and connection means arranged to connect with said portable electronic device in order to deliver a signal from the portable electronic device to the display panel.
48. 48. A projection arrangement as claimed in claim 47, wherein said connection means is a plug and/or socket arranged to connect with a cable connected to said portable electronic device.
49. 49. A projection arrangement as claimed in claim 47 or 48, wherein said display panel is a microdisplay panel.
50. 50. A projection arrangement as claimed in any one of claims 47 to 49, wherein said light source is provided in an illumination part, and said projection optics is provided in a projection part.
51. 51. A projection arrangement as claimed in claim 50, wherein said illumination and projection parts are hingedly connected together.
52. 52. A projection arrangement as claimed in claim 50 or 51, wherein said illumination part and/or projection part are telescopically extendable.