WO2007093766A1 - Projection apparatus - Google Patents

Projection apparatus Download PDF

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Publication number
WO2007093766A1
WO2007093766A1 PCT/GB2007/000433 GB2007000433W WO2007093766A1 WO 2007093766 A1 WO2007093766 A1 WO 2007093766A1 GB 2007000433 W GB2007000433 W GB 2007000433W WO 2007093766 A1 WO2007093766 A1 WO 2007093766A1
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WO
WIPO (PCT)
Prior art keywords
projection
projection apparatus
monochrome
colour
light
Prior art date
Application number
PCT/GB2007/000433
Other languages
French (fr)
Inventor
Geoffrey Howard Blackham
Original Assignee
Seos Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Seos Limited filed Critical Seos Limited
Publication of WO2007093766A1 publication Critical patent/WO2007093766A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3179—Video signal processing therefor
    • H04N9/3185—Geometric adjustment, e.g. keystone or convergence
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3102—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] using two-dimensional electronic spatial light modulators
    • H04N9/3105—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] using two-dimensional electronic spatial light modulators for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3141—Constructional details thereof
    • H04N9/315—Modulator illumination systems

Definitions

  • This invention relates to projection apparatus and, more especially, this invention relates to projection apparatus in which different monochrome images are projected onto a projection screen to form a colour image.
  • Projection apparatus which projects video images onto a projection screen is well known.
  • the projection screen may be a front projection screen or a rear projection screen.
  • the known projection apparatus may include liquid crystal projectors, using either transmissive or reflective liquid crystal displays as spatial light modulators.
  • the known projection apparatus may include projectors which use micromirror devices as spatial light modulators.
  • Projection apparatus which uses liquid crystal displays or micromirror devices as the means to modulate illumination are lamp-based types of projection apparatus which typically use one lamp or a multiple of lamps emitting white light as the illumination source.
  • the white light illumination source is a polychromatic source which is managed by optical means within the projection apparatus either to illuminate the spatial light modulator sequentially by means of a colour wheel, or to split the white light into red, green and blue components such that these components are able to be modulated separately by colour-specific spatial light modulators.
  • These types of projection apparatus are known as fixed matrix projectors. Other types of projectors using fixed matrix devices are known, but these also tend to use a white light source.
  • Monochromatic light sources such as lasers and light emitting diodes are also used in known projection apparatus. Although each colour is modulated independently, optical means is used within the projection apparatus to recombine the light so that is can be projected via a single projection lens to a projection screen.
  • a single projection lens coupled to the optics within fixed matrix projection apparatus ensures that an image is easy to focus on the projection screen.
  • the optical means used within the projection apparatus to recombine or combine the light may affect the final image which is displayed. For example, the optical means may reduce brightness or it may reduce contrast.
  • the optical means may also require precision alignment of the spatial light modulators within the projection apparatus so that the various coloured portions of the images are correctly converged onto the projection screen.
  • cathode ray tube projection apparatus Another known type of projection apparatus is cathode ray tube projection apparatus.
  • three separate cathode ray tubes are assembled adjacent to one another in an enclosure.
  • One cathode ray tube has red phosphor
  • one cathode ray tube has green phosphor
  • one cathode ray tube has blue phosphor.
  • Each cathode ray tube has its own projection lens so that the cathode ray tube projection apparatus is able to project three separate images onto the projection screen.
  • the images are combined optically onto the projection screen in order to form a single coloured image.
  • the cathode ray tube projection apparatus has reduced brightness when compared to fixed matrix projection apparatus.
  • the cathode ray tube projection apparatus is also heavy as it contains three cathode ray tubes with associated electronics and lenses.
  • the cathode ray tube projection apparatus is also relatively large for the amount of light which is output.
  • the projection lenses also need to be large in order to image the surface of the phosphor onto the projection screen.
  • the cathode ray tube projection apparatus is also relatively expensive when compared to fixed matrix projection apparatus.
  • the cathode ray tube projection apparatus does however have high levels of contrast, which is important for some applications, especially within the simulation environment.
  • Projection apparatus is also known in which images from separate projectors are overlaid on a projection screen.
  • the separate projectors are typically placed adjacent to one another and optical means, normally lens shift optical means, is used to align the images which are to be overlaid.
  • optical means normally lens shift optical means
  • This technique is used in image display apparatus which displays stereo images, or in which increased brightness is desired in which case the imaged to be overlaid are identical images.
  • the lens shift technique of aligning images is only satisfactory on flat projection screens. Optical alignment does not provide satisfactory results if the projection screen is not flat, for example if the projection screen is curved, concave or convex.
  • projection apparatus comprising: (i) a first projection module and a first monochrome light source generating light at a first colour or wavelength;
  • video control means for controlling video signals to the first, second and third projection modules, the video control means comprising image remapping means for overlaying images from the first, second and third projection modules;
  • the projection apparatus of the present invention is able to have distinct advantages over known projection apparatus currently used for forming polychromatic images on a projection screen. More specifically, with the projection apparatus of the present invention, because each projection module is only required to modulate monochrome light, the optical arrangements within each one of these modules is able to be much simpler than that required for projection apparatus processing light from a white light source. Also, any chromatic aberrations within one of the projection modules can be reduced as the optical layout and component can be designed to function with the specific wavelength of light being supplied by the monochromatic light source.
  • the projection apparatus may be one in which each projection module comprises a first spatial light modulator and a projection lens.
  • the first spatial light modulator may be a transmissive spatial light modulator.
  • the transmissive spatial light modulator may be a transmisive liquid crystal spatial light modulator.
  • the first spatial light modulator may be a reflective spatial light modulator.
  • the reflective spatial light modulator may be a reflective liquid crystal spatial light modulator, or it may be a liquid crystal on silicon spatial light modulator.
  • the first spatial light modulator may be a digital micromirror device.
  • the projection apparatus may be one in which each projection module comprises a second spatial light modulator arranged in series with the first spatial light modulator in order to serially modulate light.
  • the first and second spatial light modulators may both be transmissive spatial light modulators.
  • the first and the second spatial light modulators may both be reflective spatial light modulators.
  • the second spatial light modulator may be a different type of spatial light modulator to the first spatial light modulator.
  • the monochrome light sources may be laser light sources, or light emitting diode light sources. Each monochrome light source may be located remotely from the projection module to which it supplies monochrome light.
  • the projection apparatus may be one in which each monochrome light source is located remotely from the projection module to which it supplies monochrome light, and is connected to a projection module by fibre optic means.
  • the projection apparatus may be one in which the first monochrome light source produces light at a first colour or wavelength, the second monochrome light source produced light at a second colour or wavelength different to the first monochrome light source, and the third monochrome light source produces light at a third colour or wavelength which is different to that produced by either of the first or the second monochrome light sources.
  • the projection apparatus may be one in which the monochrome light sources are all visible light sources at wavelengths in the visible part of the spectrum.
  • the monochrome light sources may be visible or non-visible monochrome light sources.
  • the first, second and third projection modules may be arranged adjacent to each other in a linear array.
  • the first, second and third projection modules may be arranged adjacent to each other in a triad array.
  • the first projection module may be arranged adjacent to at least one other projection module in order to form multi-channel display apparatus.
  • the first projection apparatus may comprise projection modules arranged adjacent to at least one other projection apparatus comprising another array of projection modules, in order to form a multi-channel display.
  • the projection apparatus may be one in which the first projection module, the second projection module and the third projection module all comprise spatial light modulators having the same resolution.
  • the projection apparatus may be one in which the first projection module, the second projection module and the third projection module all comprise spatial light modulators having different resolutions.
  • the projection apparatus may be one in which the projection screen is a front projection screen or a rear projection screen.
  • the projection screen may be a flat projection screen, a cylindrical projection screen, a compound curved projection screen, or a spherical projection screen.
  • the projection screen may be a projection screen as used in collimated display apparatus.
  • the projection apparatus may include a fourth projection module and a fourth monochrome light source generating light at a fourth colour or wavelength, the colour or wavelength of the fourth monochrome light source being different to the colour or wavelength of the first, second or third monochrome light sources.
  • the projection apparatus may include a fourth projection module and a fourth monochrome light source generating light at a fourth colour or wavelength, the colour or wavelength of the fourth monochrome light source being the same as the colour or wavelength of one of the first, second or third monochrome light sources.
  • the first, second, third and fourth projection modules may be arranged adjacent to each other in a linear array.
  • the first, second, third and fourth projection modules may be arranged adjacent to each other in a two-dimensional array.
  • the projection apparatus of the present invention may include a fifth projection module and a fifth monochrome light source generating light at a fifth colour or wavelength, the colour or wavelength of the fifth monochrome light source being different to the colour or wavelength of the first, second, third and fourth monochrome light sources.
  • the projection apparatus of the present invention includes the spatial light modulator
  • spatial light modulators can be adjusted to work much more efficiently than the known apparatus, producing better uniformity and contrast within the display. This is because the spatial light modulators are only modulating light at one wavelength.
  • the video information determining the images displayed by the projection modules is supplied by the video control means.
  • the video control means supplies information to each of the projection modules depending upon the wavelength of light being supplied to each projection module by the associated monochrome light sources.
  • the resultant image will appear to the user to be contiguous and properly converged in its colour components.
  • This is a result of the remapping applied to each of the images of separate colours or wavelengths by the video control means, which has the effect of ensuring that the content from all projection modules is spatially aligned.
  • the video data being shown represents a limited range of spatial frequencies of the display devices.
  • One example of this is from a computer image generator, the output of which has undergone a certain degree of filtering to avoid aliasing between computer generated scene content and the display pixel format.
  • any slight misalignment of overlaid images will not result in noticeable mis- convergence.
  • typical three panel projectors such for example as liquid crystal display projectors exhibit imperfect registration between the colour panels
  • the image quality from the projection apparatus of the present invention will be superior because essentially perfect image content registration can be achieved from the separate image remapping per colour or wavelength.
  • the projection apparatus of the present invention may also be advantageous in other aspects.
  • some displays especially those used in flight simulation, may need to supply the pilot or user of the simulator with information which will stimulate night vision goggles.
  • Several groups of projector modules can be arranged to make a larger display in order to cover a larger projection screen or larger field of view.
  • monochrome light sources which output light at a known wavelength enables displays which have multiple projection arrangements to have improved matching between adjacent displays, especially in terms of colour matching. This is difficult to achieve with known lamp-based projection apparatus when arranged in a multiple projector display because the characteristics of lamps and colour separation optics vary significantly from one projector to another.
  • Monochrome light sources may be used which have very large light flux output, and therefore one monochrome light source may be used to supply light to more than one projector module. This also means that colour is consistent across multiple projection display apparatus.
  • Any image remapping or distortion correction is able to be carried out electronically by the control means.
  • the image remapping or distortion correction is able to be specific to the extent of the overlaid image, and the location of the projection modules with respect to the projection screen.
  • the shape of the projection screen enables the projection apparatus to be used on both front projection and rear projection screens, in which the screens may be flat, cylindrical or have a compound curved shape such for example as a spherical shape.
  • Figure 1 shows projection apparatus of the present invention
  • Figure 2 shows projection apparatus of the present invention in which monochrome light sources are situated remotely from projection modules
  • Figure 3 shows in schematic block diagram form projection apparatus of the present invention
  • Figure 4 shows an arrangement of projection modules forming part of projection apparatus of the present invention
  • Figure 5 shows an alternative arrangement of projection modules
  • Figure 6 shows a further alternative arrangement of projection modules
  • Figure 7 shows a further alternative arrangement of projection modules
  • Figure 8 shows three projection modules projecting onto a flat screen
  • Figure 9 shows an alternative arrangement of three projection modules projecting onto a flat screen
  • Figure 10 shows three projection modules projecting onto a curved screen
  • Figure 11 shows an alternative arrangement of three projection modules projecting onto a curved screen
  • Figure 12 shows two groups of projection modules projecting onto a curved screen
  • Figure 13 shows a distorted single image
  • Figure 14 shows distorted images from adjacent projection modules overlaid
  • Figure 15 shows an image having a second different distortion
  • Figure 16 shows overlaid images having the distortion shown in Figure 15;
  • Figure 17 shows another type of image distortion
  • Figure 18 shows overlaid images having the distortion shown in Figure 17.
  • a first projection module 4 is located adjacent to a second projection module 12 and a third projection module 20.
  • Each of the projection modules 4, 12, 20 is a separate module.
  • a monochrome light source 6 provides monochrome light at a particular colour or wavelength to the projection module 4.
  • a monochrome light source 14 provides monochrome light at a particular colour or wavelength to the projection module 12.
  • a monochrome light source 22 provides monochrome light at a particular colour or wavelength to the third projection module 20.
  • the projection apparatus 2 includes video control means 28.
  • the video control means 28 is connected to the first projection module 4 by connection means 10.
  • the video control means 28 is connected to the second projection module 12 by connection means 18.
  • the video control means 28 is connected to the third projection module 20 by connection means 26.
  • the connection means 10, 18, 26 may be any suitable and appropriate connection means for transmitting video data to the projection modules, and this therefore determines the video input to each of these projection modules 4, 12, 20 controlling the images displayed by the projection modules.
  • the first monochrome light source 6 produces light at a first wavelength and therefore of a first colour.
  • the second monochrome light source 14 produces light at a second wavelength which is different to that of light produced by the first monochrome light source 6. Therefore the monochrome light source 14 produces light which is at a different colour from that produced by the first monochrome light source 6.
  • the third monochrome light source 22 produces light of a third wavelength different to that produced by the first and second monochrome light sources 6, 14.
  • the third monochrome light source 22 produces light at a colour different to that produced by the first monochrome light source 6 and the second monochrome light source 14.
  • each of the projection modules will display an image in the visible part of the spectrum.
  • the first monochrome light source 6 could be in the red portion of the visible spectrum, so that the first projection module 4 would display a red image.
  • the second monochrome light source 14 could be in the green part of the visible spectrum, and thus the second projection module 12 would display a green image.
  • the third monochrome light source 22 could be in the blue part of the visible spectrum, and thus the third projection module 20 would display a blue image.
  • the video control means is used to determine the video signal to each of the projection modules, then the user will see a colour image on the screen.
  • This colour image on the screen will be an image which is the combined image of those images displayed by the first projection means 4, the second projection means 12 and the third projection means 20.
  • the electronic image remapping function of the controls ensures that correct alignment of the overlaid images is obtained, so that no discontinuities are observed in the compound image.
  • the first projection module 34 is located adjacent to a second projection module 42 and a third projection module 50.
  • Each of the projection modules 34, 42, 50 is a separate module.
  • a first monochromatic light source 36 supplies monochromatic light of a specific colour to the first projection module 34 via optical means 38.
  • a second monochromatic light source 44 supplies monochromatic light via optical means 46 to the second projection module 42.
  • a third monochromatic light source 52 supplies monochrome light via optical means 54 to the third projection module 50.
  • Video control means 58 is connected to the first projection module 34 by connection means 40.
  • the video control means 58 is connected to the second projection module 42 by connection means 48.
  • the video control means 58 is connected to the third projection module 50 by connection means 56.
  • the connection means 40, 48, 56 may be any suitable and appropriate connection means for transmitting video data to the projection modules, and therefore this determines the video input to each of the projection modules 34, 42 and 50 controlling the images displayed by the projection modules.
  • the first monochrome light source 36 produces light at a first wavelength.
  • the second monochrome light source 44 produces light at a second wavelength which is different to that of the light produced by the first monochrome light source 36.
  • the third monochrome light source 52 produces light of a third wavelength which is different to that produced by the first and the second monochrome light sources 36, 54. If the first, second and third monochrome light sources 36, 44, 52 produce light in the visible part of the spectrum, each of the projection modules will display an image in the visible part of the spectrum.
  • the first monochrome light source 36 could be in the red portion of the visible spectrum, whereby the first projection module 34 will display a red image.
  • the second monochrome light source 44 would be in the green part of the visible spectrum, whereby the second projection module 42 would display a green image.
  • the third monochrome light source 52 could be in the blue part of the visible spectrum, whereby the third projection module 50 would display a blue image.
  • the image from the first, second and third projection modules 34, 42 and 50 are overlaid on the projection screen, and the video control means is used to determined the video signal to each of the projection modules, then the user will see a colour image on the projection screen, which colour image will be the combined image of those images displayed by the first projection means 34, the second projection means 46 and the third projection means 50.
  • a red light source Using a red light source, a green light source and a blue light source is a well known combination of colours to produce a coloured image. There are many other combinations which can be used and which will also produce coloured images. These alternative combinations may be, for example, cyan, yellow and magenta.
  • the monochrome light sources used in the apparatus of the present invention may be in the visible part of the spectrum, or they may be in the non-visible part of the spectrum, especially in displays which are to be viewed using night vision goggles which detect light in the infrared part of the spectrum.
  • the projection apparatus 62 comprises a first projection module 64 having a first monochrome light source 66.
  • a second projection module 68 has a monochrome light source 70.
  • a third projection module 72 has a monochrome light source 74.
  • Light from the first monochrome light source 66 is supplied to the first projection module 74, where the light is modulated.
  • the modulated light is projected onto a projection screen 78.
  • Light from the second monochrome light source 70 is supplied to the second projection module 68 where it is modulated.
  • This modulated light is projected onto the projection screen 78.
  • Light from the third monochrome light source 74 is supplied to the third projection module 72 where it is modulated.
  • This modulated light is projected onto the projection screen 78.
  • Control means 76 for controlling video is connected to the first projection module 64, the second projection module 68 and the third projection module 72. The control means 76 determined the image displayed by the projection modules on the projection screen 78.
  • Figure 4 shows an arrangement 82 of three projection modules 84, 86, 88.
  • the three projection modules 84, 86, 88 are located adjacent to one another in a linear format.
  • the colour of the images output by the projection modules 84, 86, 88 can be arranged to obtain the most beneficial results in terms of combined image.
  • the arrangement 82 may have a green projection module at the top of the array, the centre of the array, or at the bottom of the array.
  • the position of the other colour projection modules can also be varied.
  • Light sources and the projection screen are not shown in Figure 4 for clarity. 00433
  • Figure 5 shows an alternative arrangement 90 of three projection modules 92, 94, 96.
  • the projection modules 92, 94, 96 are arranged as a triangular array. Again positions within the array of different colour projection modules can be varied. Light sources and the projection screen have not been shown in Figure 5 for clarity.
  • Figure 6 shows an arrangement 100 of four projection modules 102, 104, 106, 108.
  • Some image display apparatus and image generators are able to produce images which are composed of more than three composite coloured images.
  • some image generators used in simulation provide image data for an infrared image as part of the scene displayed.
  • the four projection modules 102, 104, 106, 108 would display red, green, blue and infrared monochrome images.
  • Figure 6 shows that they can be arranged in a linear array. This linear array may be horizontal, vertical or at an angle, as may the array derived in other Figures. Light sources and the projection screen are not shown in Figure 6 for clarity.
  • Figure 7 shows an alternative arrangement 110 of four projection modules 112, 114, 116 and 118.
  • the four projection modules 112, 114, 116 and 118 are arranged as a square array.
  • the projection modules 112, 114, 116, 118 may produce images using light sources in the visible part of the spectrum, the non-visible part of the spectrum, or a combination of both of these parts of the spectrum. Light sources and the projection screen are not shown in Figure 7 for clarity.
  • Figure 8 shows an arrangement 120 of three projection modules projecting onto a flat projection screen 128.
  • Projection modules 122, 124, 126 each have their optical axis orthogonal to the projection screen 128.
  • the image from the first projection module 122, the second projection module 124 and the third projection module 126 can be overlaid on the projection screen 128 by using optical techniques such as lens shift to reposition each image so that the images are contiguous on the projection screen 128. This is possible as there is no distortion of the projected images on the projection screen 128 because it is a flat projection screen 128.
  • Light sources are not shown in Figure 8 for clarity.
  • projection apparatus 130 comprising three projection modules 132, 134, 136 which project onto a flat projection screen 138.
  • the projection modules 132, 134, 136 do not have their optical axes at an angle which is orthogonal to the flat projection screen 138. Therefore the image produced on the flat projection screen 138 by the projection module 132 will have a keystone distortion which is different to the keystone distortion of the image produced by the projection module 134.
  • the image produced by the projection module 136 will have a distortion which is again different to either of the other two images displayed on the flat projection screen 138.
  • optical techniques such for example as lens shift are not able to overcome the distortions present in the three images, enabling them to be overlapped.
  • Figure 10 shows projection apparatus 140 comprising three projection modules 142, 144, 146 which project onto a curved projection screen 148.
  • the projection screen 148 is convex.
  • the curved projection screen 148 could be concave, cylindrical, spherical or with a compound curve shape.
  • the projection apparatus shown in Figure 10 is similar to that shown in Figure 9 insofar as the images from the three projection modules 142, 144, 146 cannot be overlaid using optical techniques alone. Electronic techniques must also be used.
  • light sources have not been shown for clarity.
  • Figure 11 shows projection apparatus 150 comprising three projection modules 152, 154, 156 projecting onto a curved projection screen 158.
  • the curved projection screen 158 is shown as being concave, but the curved projection screen 158 could be of an alternative shape such for example as those mentioned in connection with Figure 10.
  • the projection apparatus 150 is similar to the projection apparatus 130 shown in Figure 9 insofar as the images from the three projection modules cannot be overlaid using optical techniques alone. Electronic techniques must also be used.
  • light sources have not been shown for clarity.
  • projection apparatus 160 comprising a first projection apparatus of three projection modules 162, 164, 166, and a second projection apparatus of three projection modules 168, 170, 172.
  • the first and second projection apparatus display images onto a curved projection screen 174 adjacent to one another.
  • electronic means is needed to enable images from the first projection apparatus of the three projection modules 162, 164, 166 to be overlaid.
  • electronic means is needed to enable images from the second projection apparatus of the projection modules 168, 170, 172 to be overlaid.
  • Figure 12 demonstrates that large images can be produced if more than one projection apparatus is used to display images on a projection screen, with the first projection apparatus displaying images adjacent to images from the second projection apparatus.
  • a third projection apparatus could be arranged adjacent to the first and the second projection apparatus. More projection apparatus could be arranged to further increase the display parameters.
  • light sources are not shown for clarity.
  • Figure 13 shows the keystone distortion apparent in an image 180 which is projected onto a projection screen, the optical axes of the projection module not being orthogonal to the screen as shown in Figure 9.
  • Figure 14 shows three images, each having a different degree of keystone distortion.
  • the boundaries of the three images produced by projection apparatus having three projection modules are shown.
  • Boundary 182 is the boundary of an image displayed by a first projection module.
  • Boundary 184 is the boundary of an image displayed by a second projection module.
  • Boundary 186 is the boundary of an image displayed by a third projection module. It can be seen that there is an area 188 indicated by the cross hatched markings which is common to the three images. The three independent images are thus able to be overlaid or converged electronically within this cross hatched area.
  • Figure 15 shows pincushion distortion which occurs when an image 190 is projected onto a convex projection screen as shown, for example, in Figure 10.
  • Figure 16 shows three images, with each image having a different degree of pincushion distortion.
  • the boundaries of the three images produced by projection apparatus having three projection modules are shown.
  • Boundary 192 is the boundary of an image displayed by a first projection module.
  • Boundary 194 is the boundary of an image displayed by a second projection module.
  • Boundary 196 is the boundary of an image display by a third projection module. It can be seen that there is an area 198 indicated by the cross hatched markings which is common to the three images. The three independent images are thus able to be overlaid or converged electronically within the cross hatched area.
  • Figure 17 shows an image 200 which is produced when a projection module projects an image onto a concave projection screen.
  • the distortion is known as barrel distortion.
  • Figure 18 shows three images, each having a different degree of barrel distortion.
  • the boundaries of the three images produced by projection apparatus having three projection modules are shown.
  • Boundary 202 is the boundary of an image displayed by a first projection module.
  • Boundary 204 is the boundary of an image displayed by a second projection module.
  • Boundary 206 is the boundary of an image displayed by a third projection module. It can be seen that there is an area 208 indicated by the cross hatched markings which is common to the three images. The three independent images are thus able to be overlaid or converged electronically within the cross hatched area.
  • the projection apparatus of the present invention has many advantages over known displays.
  • the independent modules, each modulating monochrome light enables more accurate management of the display in terms of colour. This is especially so if a display comprising two or more projection apparatus adjacent to one another is needed.
  • suitable monochrome sources such as lasers and light emitting diodes means that a precise wavelength of light generated by the light source is able to be known.
  • the optical means within the projection module used to manage the path of light through the projection module via the spatial light modulator to the projection lens and onto the projection screen can be much more efficient because all components can be designed for a single wavelength of light.
  • Monochrome light sources which do not require any management within the projection module in terms of separating and combining different coloured light are much more efficient because losses are inevitably incurred during such processes.
  • the projection apparatus of the present invention does not require light to be separated into constituent colours, modulated and recombined prior to being projected.
  • Monochrome light is projected by each of the projection modules, the separate images being combined optically on the projection screen.
  • Another advantage of the projection apparatus of the present invention is the ability to have the monochrome light sources for each projection module and the control means for controlling the projection modules located in a position which is remote from the projection modules. This enables the projection modules to be small compared to known projection modules, allowing flexibility of positioning of the groups of projection modules within a display. The configuration of the projection modules is also flexible, allowing for many different arrangements of the projection modules within a group.

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Abstract

Projection apparatus comprising: (i) a first projection module and a first monochrome light source generating light at a first colour or wavelength; (ii) a second projection module and a second monochrome light source generating light at a second colour or wavelength; (iii) a third projection module and a third monochrome light source generating light at a third colour or wavelength; (iv) video control means for controlling video signals to the first, second and third projection modules, the video control means comprising image remapping means for overlaying images from the first, second and third projection modules; and (v) a projection screen for displaying images projected from the first, second and third projection modules.

Description

PROJECTION APPARATUS
This invention relates to projection apparatus and, more especially, this invention relates to projection apparatus in which different monochrome images are projected onto a projection screen to form a colour image.
Projection apparatus which projects video images onto a projection screen is well known. The projection screen may be a front projection screen or a rear projection screen. The known projection apparatus may include liquid crystal projectors, using either transmissive or reflective liquid crystal displays as spatial light modulators. Alternatively, the known projection apparatus may include projectors which use micromirror devices as spatial light modulators. Projection apparatus which uses liquid crystal displays or micromirror devices as the means to modulate illumination are lamp-based types of projection apparatus which typically use one lamp or a multiple of lamps emitting white light as the illumination source. The white light illumination source is a polychromatic source which is managed by optical means within the projection apparatus either to illuminate the spatial light modulator sequentially by means of a colour wheel, or to split the white light into red, green and blue components such that these components are able to be modulated separately by colour-specific spatial light modulators. These types of projection apparatus are known as fixed matrix projectors. Other types of projectors using fixed matrix devices are known, but these also tend to use a white light source. Monochromatic light sources such as lasers and light emitting diodes are also used in known projection apparatus. Although each colour is modulated independently, optical means is used within the projection apparatus to recombine the light so that is can be projected via a single projection lens to a projection screen. A single projection lens coupled to the optics within fixed matrix projection apparatus ensures that an image is easy to focus on the projection screen. The optical means used within the projection apparatus to recombine or combine the light may affect the final image which is displayed. For example, the optical means may reduce brightness or it may reduce contrast. The optical means may also require precision alignment of the spatial light modulators within the projection apparatus so that the various coloured portions of the images are correctly converged onto the projection screen.
Another known type of projection apparatus is cathode ray tube projection apparatus. In the known cathode ray tube projection apparatus, three separate cathode ray tubes are assembled adjacent to one another in an enclosure. One cathode ray tube has red phosphor, one cathode ray tube has green phosphor, and one cathode ray tube has blue phosphor. Each cathode ray tube has its own projection lens so that the cathode ray tube projection apparatus is able to project three separate images onto the projection screen. The images are combined optically onto the projection screen in order to form a single coloured image. The cathode ray tube projection apparatus has reduced brightness when compared to fixed matrix projection apparatus. The cathode ray tube projection apparatus is also heavy as it contains three cathode ray tubes with associated electronics and lenses. The cathode ray tube projection apparatus is also relatively large for the amount of light which is output. The projection lenses also need to be large in order to image the surface of the phosphor onto the projection screen. The cathode ray tube projection apparatus is also relatively expensive when compared to fixed matrix projection apparatus. The cathode ray tube projection apparatus does however have high levels of contrast, which is important for some applications, especially within the simulation environment.
Projection apparatus is also known in which images from separate projectors are overlaid on a projection screen. The separate projectors are typically placed adjacent to one another and optical means, normally lens shift optical means, is used to align the images which are to be overlaid. This technique is used in image display apparatus which displays stereo images, or in which increased brightness is desired in which case the imaged to be overlaid are identical images. The lens shift technique of aligning images is only satisfactory on flat projection screens. Optical alignment does not provide satisfactory results if the projection screen is not flat, for example if the projection screen is curved, concave or convex.
It is an aim of the present invention to obviate or reduce the above mentioned problems.
Accordingly, in one non-limiting embodiment of the present invention there is provided projection apparatus comprising: (i) a first projection module and a first monochrome light source generating light at a first colour or wavelength;
(ii) a second projection module and a second monochrome light source generating light at a second colour or wavelength;
(iii) a third projection module and a third monochrome light source generating light at a third colour or wavelength;
(iv) video control means for controlling video signals to the first, second and third projection modules, the video control means comprising image remapping means for overlaying images from the first, second and third projection modules; and
(v) a projection screen for displaying images projected from the first, second and third projection modules.
The projection apparatus of the present invention is able to have distinct advantages over known projection apparatus currently used for forming polychromatic images on a projection screen. More specifically, with the projection apparatus of the present invention, because each projection module is only required to modulate monochrome light, the optical arrangements within each one of these modules is able to be much simpler than that required for projection apparatus processing light from a white light source. Also, any chromatic aberrations within one of the projection modules can be reduced as the optical layout and component can be designed to function with the specific wavelength of light being supplied by the monochromatic light source.
The projection apparatus may be one in which each projection module comprises a first spatial light modulator and a projection lens.
The first spatial light modulator may be a transmissive spatial light modulator. The transmissive spatial light modulator may be a transmisive liquid crystal spatial light modulator.
Alternatively, the first spatial light modulator may be a reflective spatial light modulator. The reflective spatial light modulator may be a reflective liquid crystal spatial light modulator, or it may be a liquid crystal on silicon spatial light modulator.
Alternatively, the first spatial light modulator may be a digital micromirror device.
The projection apparatus may be one in which each projection module comprises a second spatial light modulator arranged in series with the first spatial light modulator in order to serially modulate light.
The first and second spatial light modulators may both be transmissive spatial light modulators. Alternatively, the first and the second spatial light modulators may both be reflective spatial light modulators.
The second spatial light modulator may be a different type of spatial light modulator to the first spatial light modulator.
The monochrome light sources may be laser light sources, or light emitting diode light sources. Each monochrome light source may be located remotely from the projection module to which it supplies monochrome light.
The projection apparatus may be one in which each monochrome light source is located remotely from the projection module to which it supplies monochrome light, and is connected to a projection module by fibre optic means.
The projection apparatus may be one in which the first monochrome light source produces light at a first colour or wavelength, the second monochrome light source produced light at a second colour or wavelength different to the first monochrome light source, and the third monochrome light source produces light at a third colour or wavelength which is different to that produced by either of the first or the second monochrome light sources.
The projection apparatus may be one in which the monochrome light sources are all visible light sources at wavelengths in the visible part of the spectrum. Alternatively, the monochrome light sources may be visible or non-visible monochrome light sources.
The first, second and third projection modules may be arranged adjacent to each other in a linear array. Alternatively, the first, second and third projection modules may be arranged adjacent to each other in a triad array.
Alternatively, the first projection module may be arranged adjacent to at least one other projection module in order to form multi-channel display apparatus. In this case, the first projection apparatus may comprise projection modules arranged adjacent to at least one other projection apparatus comprising another array of projection modules, in order to form a multi-channel display.
The projection apparatus may be one in which the first projection module, the second projection module and the third projection module all comprise spatial light modulators having the same resolution. Alternatively, the projection apparatus may be one in which the first projection module, the second projection module and the third projection module all comprise spatial light modulators having different resolutions.
The projection apparatus may be one in which the projection screen is a front projection screen or a rear projection screen. The projection screen may be a flat projection screen, a cylindrical projection screen, a compound curved projection screen, or a spherical projection screen. Alternatively, the projection screen may be a projection screen as used in collimated display apparatus.
The projection apparatus may include a fourth projection module and a fourth monochrome light source generating light at a fourth colour or wavelength, the colour or wavelength of the fourth monochrome light source being different to the colour or wavelength of the first, second or third monochrome light sources.
Alternatively, the projection apparatus may include a fourth projection module and a fourth monochrome light source generating light at a fourth colour or wavelength, the colour or wavelength of the fourth monochrome light source being the same as the colour or wavelength of one of the first, second or third monochrome light sources.
When the projection apparatus includes a fourth projection module and a fourth monochrome light source, then the first, second, third and fourth projection modules may be arranged adjacent to each other in a linear array. Alternatively, the first, second, third and fourth projection modules may be arranged adjacent to each other in a two-dimensional array.
The projection apparatus of the present invention may include a fifth projection module and a fifth monochrome light source generating light at a fifth colour or wavelength, the colour or wavelength of the fifth monochrome light source being different to the colour or wavelength of the first, second, third and fourth monochrome light sources.
Where the projection apparatus of the present invention includes the spatial light modulator, then spatial light modulators can be adjusted to work much more efficiently than the known apparatus, producing better uniformity and contrast within the display. This is because the spatial light modulators are only modulating light at one wavelength.
The video information determining the images displayed by the projection modules is supplied by the video control means. The video control means supplies information to each of the projection modules depending upon the wavelength of light being supplied to each projection module by the associated monochrome light sources.
When images are projected from different locations towards a projection screen, differing degrees of image distortion will be obtained. When projecting onto a flat surface^ the location of projected images can be altered using optical techniques such as lens shift to overlay separate images. When projecting onto a flat screen from an angle or onto a curved screen, then the images become distorted. In this case, image correction or remapping is applied to each of the images projected by the projection module so that a contiguous image will be seen. The image remapping is applied by the video control means.
Even though the plurality of images produced by the projection apparatus of the present invention will not be overlaid on a pixel-by-pixel basis, the resultant image will appear to the user to be contiguous and properly converged in its colour components. This is a result of the remapping applied to each of the images of separate colours or wavelengths by the video control means, which has the effect of ensuring that the content from all projection modules is spatially aligned. It should be noted that, in many applications, the video data being shown represents a limited range of spatial frequencies of the display devices. One example of this is from a computer image generator, the output of which has undergone a certain degree of filtering to avoid aliasing between computer generated scene content and the display pixel format. In such applications, any slight misalignment of overlaid images will not result in noticeable mis- convergence. Indeed, given that typical three panel projectors such for example as liquid crystal display projectors exhibit imperfect registration between the colour panels, the image quality from the projection apparatus of the present invention will be superior because essentially perfect image content registration can be achieved from the separate image remapping per colour or wavelength.
The projection apparatus of the present invention may also be advantageous in other aspects. Thus, for example, some displays, especially those used in flight simulation, may need to supply the pilot or user of the simulator with information which will stimulate night vision goggles. Using a monochrome light source which is in the infrared range of the spectrum and displaying a light from this light source using the fourth projection module adjacent to the first, second, and third projection modules, is able to provide a display which will be compatible with night vision goggles.
Several groups of projector modules can be arranged to make a larger display in order to cover a larger projection screen or larger field of view.
Using monochrome light sources which output light at a known wavelength enables displays which have multiple projection arrangements to have improved matching between adjacent displays, especially in terms of colour matching. This is difficult to achieve with known lamp-based projection apparatus when arranged in a multiple projector display because the characteristics of lamps and colour separation optics vary significantly from one projector to another.
Monochrome light sources may be used which have very large light flux output, and therefore one monochrome light source may be used to supply light to more than one projector module. This also means that colour is consistent across multiple projection display apparatus.
Any image remapping or distortion correction is able to be carried out electronically by the control means. The image remapping or distortion correction is able to be specific to the extent of the overlaid image, and the location of the projection modules with respect to the projection screen. The shape of the projection screen enables the projection apparatus to be used on both front projection and rear projection screens, in which the screens may be flat, cylindrical or have a compound curved shape such for example as a spherical shape.
Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings in which:
Figure 1 shows projection apparatus of the present invention;
Figure 2 shows projection apparatus of the present invention in which monochrome light sources are situated remotely from projection modules;
Figure 3 shows in schematic block diagram form projection apparatus of the present invention;
Figure 4 shows an arrangement of projection modules forming part of projection apparatus of the present invention;
Figure 5 shows an alternative arrangement of projection modules;
Figure 6 shows a further alternative arrangement of projection modules;
Figure 7 shows a further alternative arrangement of projection modules; Figure 8 shows three projection modules projecting onto a flat screen;
Figure 9 shows an alternative arrangement of three projection modules projecting onto a flat screen;
Figure 10 shows three projection modules projecting onto a curved screen;
Figure 11 shows an alternative arrangement of three projection modules projecting onto a curved screen;
Figure 12 shows two groups of projection modules projecting onto a curved screen;
Figure 13 shows a distorted single image;
Figure 14 shows distorted images from adjacent projection modules overlaid;
Figure 15 shows an image having a second different distortion;
Figure 16 shows overlaid images having the distortion shown in Figure 15;
Figure 17 shows another type of image distortion; and
Figure 18 shows overlaid images having the distortion shown in Figure 17.
Referring to Figure 1 , there is shown projection apparatus 2. A first projection module 4 is located adjacent to a second projection module 12 and a third projection module 20. Each of the projection modules 4, 12, 20 is a separate module. A monochrome light source 6 provides monochrome light at a particular colour or wavelength to the projection module 4. A monochrome light source 14 provides monochrome light at a particular colour or wavelength to the projection module 12. A monochrome light source 22 provides monochrome light at a particular colour or wavelength to the third projection module 20.
The projection apparatus 2 includes video control means 28. The video control means 28 is connected to the first projection module 4 by connection means 10. The video control means 28 is connected to the second projection module 12 by connection means 18. The video control means 28 is connected to the third projection module 20 by connection means 26. The connection means 10, 18, 26 may be any suitable and appropriate connection means for transmitting video data to the projection modules, and this therefore determines the video input to each of these projection modules 4, 12, 20 controlling the images displayed by the projection modules.
The first monochrome light source 6 produces light at a first wavelength and therefore of a first colour. The second monochrome light source 14 produces light at a second wavelength which is different to that of light produced by the first monochrome light source 6. Therefore the monochrome light source 14 produces light which is at a different colour from that produced by the first monochrome light source 6. The third monochrome light source 22 produces light of a third wavelength different to that produced by the first and second monochrome light sources 6, 14. Thus the third monochrome light source 22 produces light at a colour different to that produced by the first monochrome light source 6 and the second monochrome light source 14. If the first, second and third monochrome light sources 6, 14, 22 produce light in the visible part of the spectrum, each of the projection modules will display an image in the visible part of the spectrum. For example, the first monochrome light source 6 could be in the red portion of the visible spectrum, so that the first projection module 4 would display a red image. The second monochrome light source 14 could be in the green part of the visible spectrum, and thus the second projection module 12 would display a green image. The third monochrome light source 22 could be in the blue part of the visible spectrum, and thus the third projection module 20 would display a blue image. If the images from the first projection module 4, the second projection module 12 and the third projection module 20 are overlaid on the projection screen 29, and the video control means is used to determine the video signal to each of the projection modules, then the user will see a colour image on the screen. This colour image on the screen will be an image which is the combined image of those images displayed by the first projection means 4, the second projection means 12 and the third projection means 20. The electronic image remapping function of the controls ensures that correct alignment of the overlaid images is obtained, so that no discontinuities are observed in the compound image.
Referring now to Figure 2, there is shown projection apparatus 32 in which the light sources are located remotely from the projection modules. The first projection module 34 is located adjacent to a second projection module 42 and a third projection module 50. Each of the projection modules 34, 42, 50 is a separate module. A first monochromatic light source 36 supplies monochromatic light of a specific colour to the first projection module 34 via optical means 38. A second monochromatic light source 44 supplies monochromatic light via optical means 46 to the second projection module 42. A third monochromatic light source 52 supplies monochrome light via optical means 54 to the third projection module 50.
Video control means 58 is connected to the first projection module 34 by connection means 40. The video control means 58 is connected to the second projection module 42 by connection means 48. The video control means 58 is connected to the third projection module 50 by connection means 56. The connection means 40, 48, 56 may be any suitable and appropriate connection means for transmitting video data to the projection modules, and therefore this determines the video input to each of the projection modules 34, 42 and 50 controlling the images displayed by the projection modules.
The first monochrome light source 36 produces light at a first wavelength. The second monochrome light source 44 produces light at a second wavelength which is different to that of the light produced by the first monochrome light source 36. The third monochrome light source 52 produces light of a third wavelength which is different to that produced by the first and the second monochrome light sources 36, 54. If the first, second and third monochrome light sources 36, 44, 52 produce light in the visible part of the spectrum, each of the projection modules will display an image in the visible part of the spectrum. For example, the first monochrome light source 36 could be in the red portion of the visible spectrum, whereby the first projection module 34 will display a red image. The second monochrome light source 44 would be in the green part of the visible spectrum, whereby the second projection module 42 would display a green image. The third monochrome light source 52 could be in the blue part of the visible spectrum, whereby the third projection module 50 would display a blue image. The image from the first, second and third projection modules 34, 42 and 50 are overlaid on the projection screen, and the video control means is used to determined the video signal to each of the projection modules, then the user will see a colour image on the projection screen, which colour image will be the combined image of those images displayed by the first projection means 34, the second projection means 46 and the third projection means 50.
Using a red light source, a green light source and a blue light source is a well known combination of colours to produce a coloured image. There are many other combinations which can be used and which will also produce coloured images. These alternative combinations may be, for example, cyan, yellow and magenta.
The monochrome light sources used in the apparatus of the present invention may be in the visible part of the spectrum, or they may be in the non-visible part of the spectrum, especially in displays which are to be viewed using night vision goggles which detect light in the infrared part of the spectrum.
Referring now to Figure 3, there is shown projection apparatus 62. The projection apparatus 62 comprises a first projection module 64 having a first monochrome light source 66. A second projection module 68 has a monochrome light source 70. A third projection module 72 has a monochrome light source 74. Light from the first monochrome light source 66 is supplied to the first projection module 74, where the light is modulated. The modulated light is projected onto a projection screen 78. Light from the second monochrome light source 70 is supplied to the second projection module 68 where it is modulated. This modulated light is projected onto the projection screen 78. Light from the third monochrome light source 74 is supplied to the third projection module 72 where it is modulated. This modulated light is projected onto the projection screen 78. Control means 76 for controlling video is connected to the first projection module 64, the second projection module 68 and the third projection module 72. The control means 76 determined the image displayed by the projection modules on the projection screen 78.
Figure 4 shows an arrangement 82 of three projection modules 84, 86, 88. The three projection modules 84, 86, 88 are located adjacent to one another in a linear format. The colour of the images output by the projection modules 84, 86, 88 can be arranged to obtain the most beneficial results in terms of combined image. For example, the arrangement 82 may have a green projection module at the top of the array, the centre of the array, or at the bottom of the array. The position of the other colour projection modules can also be varied. Light sources and the projection screen are not shown in Figure 4 for clarity. 00433
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Figure 5 shows an alternative arrangement 90 of three projection modules 92, 94, 96. The projection modules 92, 94, 96 are arranged as a triangular array. Again positions within the array of different colour projection modules can be varied. Light sources and the projection screen have not been shown in Figure 5 for clarity.
Figure 6 shows an arrangement 100 of four projection modules 102, 104, 106, 108. Some image display apparatus and image generators are able to produce images which are composed of more than three composite coloured images. For example, some image generators used in simulation provide image data for an infrared image as part of the scene displayed. In this case, the four projection modules 102, 104, 106, 108 would display red, green, blue and infrared monochrome images. Figure 6 shows that they can be arranged in a linear array. This linear array may be horizontal, vertical or at an angle, as may the array derived in other Figures. Light sources and the projection screen are not shown in Figure 6 for clarity.
Figure 7 shows an alternative arrangement 110 of four projection modules 112, 114, 116 and 118. The four projection modules 112, 114, 116 and 118 are arranged as a square array. The projection modules 112, 114, 116, 118 may produce images using light sources in the visible part of the spectrum, the non-visible part of the spectrum, or a combination of both of these parts of the spectrum. Light sources and the projection screen are not shown in Figure 7 for clarity.
Figure 8 shows an arrangement 120 of three projection modules projecting onto a flat projection screen 128. Projection modules 122, 124, 126 each have their optical axis orthogonal to the projection screen 128. The image from the first projection module 122, the second projection module 124 and the third projection module 126 can be overlaid on the projection screen 128 by using optical techniques such as lens shift to reposition each image so that the images are contiguous on the projection screen 128. This is possible as there is no distortion of the projected images on the projection screen 128 because it is a flat projection screen 128. Light sources are not shown in Figure 8 for clarity.
Referring now to Figure 9, there is shown projection apparatus 130 comprising three projection modules 132, 134, 136 which project onto a flat projection screen 138. The projection modules 132, 134, 136 do not have their optical axes at an angle which is orthogonal to the flat projection screen 138. Therefore the image produced on the flat projection screen 138 by the projection module 132 will have a keystone distortion which is different to the keystone distortion of the image produced by the projection module 134. The image produced by the projection module 136 will have a distortion which is again different to either of the other two images displayed on the flat projection screen 138. In this example, optical techniques such for example as lens shift are not able to overcome the distortions present in the three images, enabling them to be overlapped. Therefore other means such for example as image or distortion correction using electronic means must be used. The said other means must be applied to each of the images produced by each of the projection modules 132, 134, 136. The said means can be applied using the control means which supplies video data information to each of the projection modules 132, 134, 136. In Figure 9, light sources are not shown for clarity.
Figure 10 shows projection apparatus 140 comprising three projection modules 142, 144, 146 which project onto a curved projection screen 148. As shown in Figure 10, the projection screen 148 is convex. However, alternatively, the curved projection screen 148 could be concave, cylindrical, spherical or with a compound curve shape. The projection apparatus shown in Figure 10 is similar to that shown in Figure 9 insofar as the images from the three projection modules 142, 144, 146 cannot be overlaid using optical techniques alone. Electronic techniques must also be used. In Figure 10, light sources have not been shown for clarity.
Figure 11 shows projection apparatus 150 comprising three projection modules 152, 154, 156 projecting onto a curved projection screen 158. The curved projection screen 158 is shown as being concave, but the curved projection screen 158 could be of an alternative shape such for example as those mentioned in connection with Figure 10. The projection apparatus 150 is similar to the projection apparatus 130 shown in Figure 9 insofar as the images from the three projection modules cannot be overlaid using optical techniques alone. Electronic techniques must also be used. In Figure 11 , light sources have not been shown for clarity.
Referring now to Figure 12, there is shown projection apparatus 160 comprising a first projection apparatus of three projection modules 162, 164, 166, and a second projection apparatus of three projection modules 168, 170, 172. The first and second projection apparatus display images onto a curved projection screen 174 adjacent to one another. As shown in Figures 9, 10 and 11 electronic means is needed to enable images from the first projection apparatus of the three projection modules 162, 164, 166 to be overlaid. Likewise electronic means is needed to enable images from the second projection apparatus of the projection modules 168, 170, 172 to be overlaid. However, Figure 12 demonstrates that large images can be produced if more than one projection apparatus is used to display images on a projection screen, with the first projection apparatus displaying images adjacent to images from the second projection apparatus. Similarly, a third projection apparatus could be arranged adjacent to the first and the second projection apparatus. More projection apparatus could be arranged to further increase the display parameters. In Figure 12, light sources are not shown for clarity.
Figure 13 shows the keystone distortion apparent in an image 180 which is projected onto a projection screen, the optical axes of the projection module not being orthogonal to the screen as shown in Figure 9.
Figure 14 shows three images, each having a different degree of keystone distortion. The boundaries of the three images produced by projection apparatus having three projection modules are shown. Boundary 182 is the boundary of an image displayed by a first projection module. Boundary 184 is the boundary of an image displayed by a second projection module. Boundary 186 is the boundary of an image displayed by a third projection module. It can be seen that there is an area 188 indicated by the cross hatched markings which is common to the three images. The three independent images are thus able to be overlaid or converged electronically within this cross hatched area.
Figure 15 shows pincushion distortion which occurs when an image 190 is projected onto a convex projection screen as shown, for example, in Figure 10.
Figure 16 shows three images, with each image having a different degree of pincushion distortion. The boundaries of the three images produced by projection apparatus having three projection modules are shown. Boundary 192 is the boundary of an image displayed by a first projection module. Boundary 194 is the boundary of an image displayed by a second projection module. Boundary 196 is the boundary of an image display by a third projection module. It can be seen that there is an area 198 indicated by the cross hatched markings which is common to the three images. The three independent images are thus able to be overlaid or converged electronically within the cross hatched area.
Figure 17 shows an image 200 which is produced when a projection module projects an image onto a concave projection screen. The distortion is known as barrel distortion.
Figure 18 shows three images, each having a different degree of barrel distortion. The boundaries of the three images produced by projection apparatus having three projection modules are shown. Boundary 202 is the boundary of an image displayed by a first projection module. Boundary 204 is the boundary of an image displayed by a second projection module. Boundary 206 is the boundary of an image displayed by a third projection module. It can be seen that there is an area 208 indicated by the cross hatched markings which is common to the three images. The three independent images are thus able to be overlaid or converged electronically within the cross hatched area.
The above described embodiments of the invention referring to the drawings illustrate that the projection apparatus of the present invention has many advantages over known displays. With the projection apparatus of the present invention, the independent modules, each modulating monochrome light, enables more accurate management of the display in terms of colour. This is especially so if a display comprising two or more projection apparatus adjacent to one another is needed. Using suitable monochrome sources such as lasers and light emitting diodes means that a precise wavelength of light generated by the light source is able to be known. This also means that the optical means within the projection module used to manage the path of light through the projection module via the spatial light modulator to the projection lens and onto the projection screen, can be much more efficient because all components can be designed for a single wavelength of light. Known projectors using a white light source have to be designed for use with broadband light and therefore they can be expensive, or they can have trade-offs in performance as components within such known projectors behave differently with light of different wavelengths. This is not the case with the projection apparatus of the present invention.
Monochrome light sources which do not require any management within the projection module in terms of separating and combining different coloured light are much more efficient because losses are inevitably incurred during such processes. The projection apparatus of the present invention does not require light to be separated into constituent colours, modulated and recombined prior to being projected. Monochrome light is projected by each of the projection modules, the separate images being combined optically on the projection screen.
As shown in the drawings, it is known that, when projecting onto a flat projection screen from an angle or onto a curved projection screen distortion occurs in the displayed image. In many cases, when a known projector using a white light source projects a single coloured image onto a projection screen with distortion, some form of electronic distortion correction or image is needed to display the image correctly. In the projection apparatus of the present invention, the electronic distortion correction or re-mapping is performed on the image displayed by each of the projection modules on an individual basis. The corrected images from each of the projection modules are therefore overlaid optically on the projection screen to form a combined image.
Another advantage of the projection apparatus of the present invention is the ability to have the monochrome light sources for each projection module and the control means for controlling the projection modules located in a position which is remote from the projection modules. This enables the projection modules to be small compared to known projection modules, allowing flexibility of positioning of the groups of projection modules within a display. The configuration of the projection modules is also flexible, allowing for many different arrangements of the projection modules within a group.
It is to be appreciated that the embodiments of the invention described above with reference to the accompanying drawings have been given by way of example only and that modifications may be effected.

Claims

1. Projection apparatus comprising:
(i) a first projection module and a first monochrome light source generating light at a first colour or wavelength;
(ii) a second projection module and a second monochrome light source generating light at a second colour or wavelength;
(iii) a third projection module and a third monochrome light source generating light at a third colour or wavelength;
(iv) video control means for controlling video signals to the first, second and third projection modules, the video control means comprising image remapping means for overlaying images from the first, second and third projection modules; and
(v) a projection screen for displaying images projected from the first, second and third projection modules.
2. Projection apparatus according to claim 1 in which each projection module comprises a first spatial light modulator and a projection lens.
3. Projection apparatus according to claim 2 in which the first spatial light modulator is a transmissive spatial light modulator.
4. Projection apparatus according to claim 3 in which the transmissive spatial light modulator is a transmissive liquid crystal spatial light modulator.
5. Projection apparatus according to claim 2 in which the first spatial light modulator is a reflective spatial light modulator.
6. Projection apparatus according to claim 5 in which the reflective spatial light modulator is a reflective liquid crystal spatial light modulator.
7. Projection apparatus according to claim 5 in which the reflective spatial light modulator is a liquid crystal on silicon spatial light modulator.
8. Projection apparatus according to claim 2 in which the first spatial light modulator is a digital micromirror device.
9. Projection apparatus according to any one of claims 2 - 9 in which each projection module comprises a second spatial light modulator arranged in series with the first spatial light modulator in order to serially modulate light.
10. Projection apparatus according to any one of claims 2, 3 and 9 in which the first and the second spatial light modulators are both transmissive spatial light modulators.
11. Projection apparatus according to claims 2, 5 and 9 in which the first and the second spatial light modulators are both reflective spatial light modulators.
12. Projection apparatus according to claim 9 in which the second spatial light modulator is a different type of spatial light modulator to the first spatial light modulator.
13. Projection apparatus according to any one of the preceding claims in which the monochrome light sources are laser light sources.
14. Projection apparatus according to any one of claims 1 - 13 in which the monochrome light sources are light emitting diode light sources.
15. Projection apparatus according to any one of the preceding claims in which each monochrome light source is located remotely from the projection module to which it supplies monochrome light.
16. Projection apparatus according to any one of the preceding claims in which each monochrome light source is located remotely from the projection module to which it supplies monochrome light, and is connected to a projection module by fibre optic means.
17. Projection apparatus according to any one of the preceding claims in which the first monochrome light source produces light at a first colour or wavelength, the second monochrome light source produces light at a second colour or wavelength different to the first monochrome light source, and the third monochrome light source produces light at a third colour or wavelength which is different to that produced by either of the first or the second monochrome light sources.
18. Projection apparatus according to any one of claims 1 - 17 in which the monochrome light sources are all visible light sources at wavelengths in the visible part of the spectrum.
19. Projection apparatus according to any one of claims 1 - 17 in which the monochrome light sources are visible or non-visible monochrome light sources.
20. Projection apparatus according to any one of the preceding claims in which the first, second and third projection modules are arranged adjacent to each other in a linear array.
21. Projection apparatus according to any one of claims 1 - 20 in which the first, second and third projection modules are arranged adjacent to each other in a triad array.
22. Projection apparatus according to any one of claims 1 - 20 in which the first projection module is arranged to project an image adjacent to at least one from another projection module in order to form multi-channel display apparatus.
23. Projection apparatus according to any one of the preceding claims in which the first projection module, the second projection module, and the third projection module all comprise spatial light modulators having the same resolution.
24. Projection apparatus according to any one of claims 1 - 23 in which the first projection module, the second projection module and the third projection module all comprise spatial light modulators having different resolutions.
25. Projection apparatus according to any one of the preceding claims in which the projection screen is a front projection screen or a rear projection screen.
26. Projection apparatus according to claim 25 in which the projection screen is a flat projections screen, a cylindrical projection screen, a compound curved projection screen, or a spherical projection screen.
27. Projection apparatus according to claim 25 in which the projection screen is a screen as used in collimated display apparatus.
28. Projection apparatus according to any one of the preceding claims and including a fourth projection module and a fourth monochrome light source generating light at a fourth colour or wavelength, the colour or wavelength of the fourth monochrome light source being different to the colour or wavelength of the first, second or third monochrome light sources.
29. Projection apparatus according to any one of claims 1 - 27 and including a fourth projection module and a fourth monochrome light source generating light at a fourth colour or wavelength, the colour or wavelength of the fourth monochrome light source being the same as the colour or wavelength of one of the first, second or third monochrome light sources.
30. Projection apparatus according to claim 28 or claim 29 in which the first, second, third and fourth projection modules are arranged adjacent to each other in a linear array.
31. Projection apparatus according to claim 28 or claim 29 in which the first, second, third and fourth projection modules are arranged adjacent to each other in a two-dimensional array.
32. Projection apparatus according to any one of claims 28 - 31 and including a fifth projection module and a fifth monochrome light source generating light at a fifth colour or wavelength, the colour or wavelength of the fifth monochrome light source being different to the colour or wavelength of the first, second, third and fourth monochrome light sources.
33. Projection apparatus according to claim 1 and substantially as herein described with reference to the accompanying drawings.
PCT/GB2007/000433 2006-02-15 2007-02-07 Projection apparatus WO2007093766A1 (en)

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US9729767B2 (en) 2013-03-22 2017-08-08 Seiko Epson Corporation Infrared video display eyewear
US10218884B2 (en) 2013-03-22 2019-02-26 Seiko Epson Corporation Infrared video display eyewear

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