Abstract:
A display system for a computer includes an image projector located in the computer and oriented to project a computer-generated image from the computer. Alternatively, the display system includes a screen and an image projector attached to the screen, where the screen is capable of receiving a computer-generated image projected by the image projector. Alternatively, the display system includes an image projector and a screen that is attached to the computer and that is capable of displaying an image projected by the image projector.

Description:
BACKGROUND 
     The invention relates to a projection display for computers. 
     Portable computers, such as laptops, generally use liquid crystal diode (LCD) panels to display computer generated images to a user. LCD panels are thin, lightweight devices that require relatively little power and therefore are particularly well-suited for portable applications. 
     Referring to FIG. 1, a laptop computer  10  includes a base  12  housing, which houses most of the computer&#39;s electronics and input/output (I/O) devices, such as keyboard  17 . The computer  10  also includes a hinged lid  14  that includes an LCD panel  16 . Because the LCD panel  16  is an active electronic device, it is driven by electronic drivers  20   a - 20   d  that, along with the LCD panel  16  and several circuit boards (e.g., flex circuits  19 ), are mounted on a frame  18  to form a display subsystem  24 . Images displayed on the LCD panel  16  cover only a portion of the total area of the lid  14  (e.g., typically between 50% and 60%). The laptop  10  also includes cables  26   a,    26   b  that run between the base  12  and the lid  14  to connect the display subsystem  24  to the video controller (not shown in FIG.  1 ). 
     Referring to FIG. 2, most computers include a central processor  30  that generates data and transmits the data to a video subsystem  35  over a bus  32 . The video subsystem  35  includes a video controller  34 , which is connected to the bus  32 , that converts the data into image data and stores the image data to a memory device  36 . At appropriate times, the video controller  34  retrieves the image data from memory  36  and uses it to control the display subsystem  24 . When the display subsystem  24  includes an LCD panel, the video controller  34  must be an LCD controller. 
     SUMMARY 
     In one aspect, the invention features a computer having a base housing containing at least one electronic component of the computer and an image projector in the base housing capable of projecting a computer-generated image. The computer may include a screen, which may be attached to the base housing, that is capable of displaying the projected image. 
     In another aspect, the invention features a computer having a base housing containing at least one electronic component of the computer, a screen, and an image projector attached to the screen (which may be attached to the base housing), where the screen is capable of displaying a computer-generated image projected by the image projector. 
     In another aspect, the invention features a computer having a base housing containing at least one electronic component of the computer, an image projector capable of projecting a computer-generated image, and a screen attached to the base housing that is capable of displaying the image. 
     Embodiments of the invention may include one or more of the following features. The electronic component may be the computer&#39;s central processor or a keyboard. The image projector may be an LCD projector. The screen may be detachable from the base housing, and it may form a hinged lid for the computer. The screen may not be connected to any portion of the base by wires. The projected image may fill essentially the entire screen. The image may be projected onto a front surface or a rear surface of the screen. The screen may be a rear-projection screen, an angle transforming screen, or a front projection screen. The image projector may be oriented to project an image beam, away from the screen, and the computer may include a reflective surface positioned to reflect the image beam toward the screen. The reflective surface may be attached to the screen and may be detachable. A locking hinge may attach the reflective surface to the screen. The reflective surface may be a mirror, such as a magnifying mirror positioned to cause the projected image to fill essentially the entire screen. The mirror may extend from the base and may be retractable into the base. 
     In another aspect, the invention features a computer having a central processing unit, an image projector, and a screen all in a self-contained unit. 
     In another aspect, the invention features a computer having a base housing containing at least one electronic component of the computer and a screen, mechanically attached to the base housing, that displays a computer generated image. No electronic component in the base housing is connected to the screen by wires carrying image data. 
     In another aspect, the invention features a display system for a computer having an image projector located in the computer and oriented to project a computer-generated image from the computer. 
     In another aspect, the invention features a display system for a computer having a screen and an image projector attached to the screen, where the screen is capable of receiving a computer-generated image projected by the image projector. 
     In another aspect, the invention features a display system for a computer having an image projector and having a screen that is attached to the computer and is capable of displaying a computer-generated image projected by the image projector. 
     In another aspect, the invention relates to a method of displaying a computer-generated image by generating the image in the computer and projecting the image from the computer to display the image. 
     In another aspect, the invention features a method of displaying a computer-generated image by projecting the image from an image projector attached to a screen and displaying the image on a surface of the screen. 
     In another aspect, the invention features a method of displaying a computer-generated image by projecting the image from an image projector and displaying the image on a screen attached to the computer. 
     Advantages of the invention may include one or more of the following. Computer displays may be thinner and more lightweight than conventional LCD panels. All or nearly all of the surface area of a laptop computer&#39;s lid may be used to display images generated by the computer, which may allow larger images or smaller lids, or both. The images also may be displayed on a wall or on another surface not attached to the computer. Because all of the video electronics may be placed in the computer&#39;s base, no cables must run between the base and the screen. 
     Other features and advantages will become apparent from the following description and from the claims. 
    
    
     DESCRIPTION 
     FIG. 1 is a perspective view of a laptop computer. 
     FIG. 2 is a block diagram of a conventional computer video subsystem. 
     FIGS. 3A and 3B are perspective and side views, respectively, of a laptop computer with a rear projection display. 
     FIG. 4 is a schematic view of a standard three cell image projector. 
     FIGS. 5A and 5B are perspective and side views, respectively, of a laptop computer with a rear projection display. 
     FIGS. 6A,  6 B, and  7  are side views of laptop computers with projection displays. 
     FIGS. 8A and 8B are perspective views of self contained computers each with a single housing and a projection display. 
    
    
     Referring to FIGS. 3A and 3B, image projection is used to improve the display qualities of a computer  40 , including but not limited to a portable (e.g., laptop) computer or any other self-contained computer (i.e., a computer in which the central processor and the display reside in a common housing or in attached housings). Instead of an LCD panel and the accompanying electronics, the computer  40  includes a base housing  44  containing an image projection engine  42  (as well as a microprocessor  43  and an alphanumeric input device, such as a keyboard  47 ) and a lid  45  comprising a rear projection screen  46  and a reflective flap  48 . The projection engine  42  projects an image beam  49  containing an image  50  onto the reflective flap  48 , which in turn reflects the beam  49  toward the screen  46 . When the beam  49  impinges upon the screen  46 , the screen  46  transmits the image  50  toward the user. To insure that the image  50  is directed toward the user  52  regardless of the angle at which the beam  49  hits the screen  46 , the screen  46  must be an angle transforming screen, such as the Microsharp™ screen made by Nashua Corporation, which is used to produce wide angle viewing screens. 
     The reflective flap  48  includes a body  54 , which is made of a relatively rigid material such as hard plastic to protect the screen when the lid  45  is closed, and a reflective layer  56 , such as a mirror or other optically reflective material, that covers the front surface  55  of the body  54 . The reflective layer  56  may be attached to the body  54  by any suitable means, such as an adhesive glue. 
     The flap  48  is mounted to the screen  46  by a hinge  58  that spans most of the width W of the screen  46  or, alternatively, by multiple hinges (not shown) distributed across the width W of the screen  46 . Preferably, the flap  48  is detachable from the lid  45  so that the image  50  may be displayed on a wall  64  (FIG. 3B) or any other surface that is not attached to and/or is distant from the computer  40 . Likewise, the lid  45  is mounted to the base  44  by hinges  62   a,    62   b.    
     When the lid  45  is fully opened, the screen  46  and the reflective flap  48  must mechanically articulate such that the optical path from the projection engine  42  to the screen  46  keeps the image  50  on the screen  46 , in focus, and properly sized. This may be accomplished, e.g., by using hinges with mechanical stops that lock the hinges  58 ,  62   a,    62   b  when the lid  45  is fully opened. For the reflective flap  48 , a releasable latch  60  may be used in lieu of or in addition to the locking hinge  58  to control the position of the flap  48 . When the screen  46  and the flap  48  are positioned properly, the image  50  fills essentially all of the screen&#39;s surface (e.g., between 90% and 100% of the surface). 
     Referring to FIG. 4, the projection engine  42  is a standard three cell, color, LCD projector reduced to a scale small enough for portable applications. For a laptop computer, the dimensions of the projection engine should be approximately 1.0″×1.0″×2.5″ but may differ depending upon the application. 
     Light in the projection engine is generated by a light source  66  that emits a light beam  67  having wavelengths in at least the red, green, and blue ranges. A light source that produces light ranging from infrared to ultraviolet wavelengths also may be used. When light is emitted from the source  66 , the light passes through a polarizer  68 , which polarizes the light at each wavelength to the angle required by the LCD cells (discussed below) in the projection engine  42 . The required polarization angle depends upon the types of LCD cells (light valves) used. 
     The polarized light then encounters a series of dielectric coated optical devices  70   a - 70   c  that act as reflective bandpass filters (i.e., each device reflects substantially all light in a given frequency band and transmits substantially all other light). The first filter  70   a,  which reflects red light and transmits substantially all other wavelengths, is positioned to direct red light toward a first light valve  72   a,  described below. Likewise, the second filter  70   b  reflects substantially all green light toward a second light valve  72   b  and transmits substantially all other light. The third filter  70   c  in turn reflects substantially all remaining blue light toward a third light valve  72   c.    
     After the red, green, and blue wavelengths are separated, the light in each range is filtered by the corresponding light valve  72   a - 72   c.  Each light valve  72   a - 72   c  is a standard transmissive LCD cell scaled to a size small enough for portable applications (e.g., typically having approximately a 1.3″ diagonal). Each LCD cell  72   a - 72   c  comprises an array of pixels (e.g., 800×600 pixels, 1024×768 pixels, etc.) controlled by a video subsystem that includes a standard color LCD controller  74 . As light of each color passes through the corresponding light valve  72   a    72   c,  the LCD controller  74  alters the properties of the liquid crystal elements at each pixel to appropriately attenuate the magnitude of the corresponding color at the pixel. The light emerging from the light valves  72   a - 72   c  then encounters a second set of reflective bandpass filters  76   a - 76   c  that recombine the filtered light into a single image beam  78 . The color and brightness of the image  78  at each pixel is determined by the combined output of the light valves  72   a - 72   c  at the pixel. 
     Before the image leaves the projection engine  42 , it typically passes through magnifying optics  80 . The required magnification value of the optics  80  is determined by three factors: 1) the size of the LCD cells in the projection engine, 2) the surface area of the screen, and 3) the optical path length between the projection engine and the screen (i.e., the distance from the engine to the flap plus the distance from the flap to the screen). As described above, the lens must magnify the image at a rate that allows the image to fill all or nearly all of the screen (see FIGS.  3 A and  3 B). In addition, the projection engine  42  must project the image so that it is properly aligned with the screen. Distortion correction optics (e.g., Keystone optics) may be used correct distortions in the image. 
     Projection engines other than a standard three cell engine also may be used. For example, the image projector may be a standard reflective polymer dispersed liquid crystal (PDLC) engine, a single filter sub-pixelated LCD engine, a single filter sub-pixelated engine with a color separator, or a color stack engine (i.e., a subtractive color system), all of which are known in the art. 
     Referring to FIGS. 5A and 5B, a mirror  82  may be used instead of a reflective flap to reflect images onto the screen  84  of a portable computer  81 . A projection engine  86  in the base  88  of the computer  81  projects an image  90  toward the mirror  82 . The mirror  82  in turn reflects the image  90  toward the screen  84 . If the mirror  82  has optical power (i.e., is a rounded or magnifying mirror), it may magnify the image  90  to fill essentially all of the screen. The required magnification and thus the mirror&#39;s shape are determined by four factors: 1) the size of the LCD cells in the projection engine, 2) the surface area of the screen, 3) the optical path length from the mirror to the screen, and 4) the magnification rate of other power elements that may be in the optical path. 
     The magnifying mirror  82  mounts to a retractable tray  92  that slides through a slot  93  in the base  88  of the computer  81 . The slot  93  is wider than the tray so that teeth  94   a,    94   b  may protrude from the tray  92 . When the tray  92  is fully extended, the teeth  94   a,    94   b  abut the rear wall  96  of the computer  81  to prevent the tray  92  from exiting the base  88  entirely. 
     The projection engine  86 , which is housed in the base  88  of the computer  81 , projects light through an opening  98  in the rear wall  96  toward the mirror  82  when the tray  92  is extended. When the tray  92  retracts into the base  88 , the mirror  82  enters the opening  98  and occupies the space between the projection engine  86  and the rear wall  96 . A back panel  100  of the tray  92  closes the opening  98  and protects the mirror  82  when the tray  92  is in this position. 
     Referring to FIGS. 6A and 6B, front projection may be used instead of rear projection to display computer-generated images. In FIG. 6A, a projection engine  112  located in the base  114  of a laptop computer  110  projects an image beam  116  through an opening  117  in the base  114  and directly onto the front surface  118  of the screen  120 . The screen  120 , which consists of any suitable reflection-type, refracting material, reflects the image toward the user  122 . The projection engine  112  must magnify the image  116  rapidly enough to fill essentially all of the front surface  118  of the screen  120 , as discussed above. In addition, the screen  120  should be mounted to the base  114  by a locking hinge  124  to ensure that while the computer is in use, the screen  120  remains at a proper angle to allow the image  116  to fill essentially all of the screen  120  and to prevent any of the image  116  from missing the screen  120  entirely. Distortion correcting optics (e.g., Keystone optics) may be used to correct distortions that may occur in the image  116 . 
     In FIG. 6B, the projection engine  112  initially projects the image beam  116  away from the screen  120  and toward a reflective surface  126 , such as a mirror. The mirror  126  in turn reflects the image beam  116  through the opening  117  in the base and onto the front surface  118  of the screen  120 . Again, a locking hinge  124  should mount the screen  120  to the base  114  and the magnification rate of the projection engine  112  should be sufficiently large to allow the image to fill essentially all of the front surface  118  of the screen  120 . If the mirror  126  is an optical power element (e.g., a magnifying mirror), the mirror itself may magnify the image to fill essentially all of the screen&#39;s surface  118 . 
     Referring to FIG. 7, a self-contained display assembly  130  mounted by a locking hinge  131  to a laptop computer  132  serves as a lid to the computer  132 . The display assembly  130  includes a screen  134  and a projection engine  136  mounted against an edge of the screen. The projection engine  136  receives image data from the computer  132  through a cable  138  that runs along one side of the screen  134  and terminates at a connector  140  that attaches to the computer  132 . A retractable tray  142  that extends from the computer  132  holds a magnifying mirror  144 . 
     When the locking hinge  131  holds the display assembly  130  in the fully-opened position, the projection engine  136  projects an image beam  146  toward the magnifying mirror  144 . The magnifying mirror  144  in turn reflects the image  146  onto the rear surface  148  of the screen  134 , magnifying the image  146  to fill essentially all of the screen  134 . When the computer  132  is not in use, the tray  142  may be pushed into the computer  132  to protect the magnifying mirror  144 . If the hinge  131  is a detachable hinge, the display assembly  130  may be removed from the computer  132  and used with another computer system. 
     Referring to FIGS. 8A and 8B, image projection may be used in-a self-contained computer  150  having a microprocessor  152 , a keyboard  154 , an image projector  156 , and a screen  158  all in a common housing. Preferably, the projector has a resolution of at least 800×600 pixels and is approximately 1.5″ high, 4″ wide, and 5″ long. In FIG. 8A, the image projector  156  projects an image beam  160  toward a reflective surface  162 , which in turns reflects the image beam  160  onto a rear projection screen. In FIG. 8B, the image projector  156  projects the image beam  160  directly onto the front surface of a front projection screen. 
     Other embodiments are within the scope of the following claims. For example, the light source in the projection engine of FIG. 4 may use color lasers.