Patent Publication Number: US-2005116968-A1

Title: Multi-capability display

Description:
FIELD OF THE INVENTION  
      The present invention relates generally to display systems, and more specifically to multi-projector display techniques for combining displayed images having different levels of resolution and/or other characteristics.  
     BACKGROUND OF THE INVENTION  
      Large, high-resolution displays allow a user to do detail work in a larger context than is generally available with standard-sized displays. For instance, maps are typically large, and also contain a great amount of detail. A large high-resolution display provides both focus and context, by showing street-level details clearly while also revealing the location of the neighborhood within the city.  
      However, the cost of creating large, high-resolution displays is prohibitive. Most large displays are somewhat low-resolution (about 20 pixels per inch); they are suitable for presenting information to a large group, but less useful for detailed work.  
      In addition, in some situations it is desirable to provide advanced functionality or features for a portion of an image that currently has focus, without necessarily providing such functionality for the entire image. For example, it may be desirable to provide a full-motion video in a portion of the image, without necessarily enabling such capability for the entirety of the image, due to the cost-prohibitiveness or unwieldiness of doing so.  
      What is needed is a display system and method that provides, at reasonable cost, a large display, and further provides high resolution to facilitate detail work. What is further needed is a display system and method that provides a large display containing a region in which advanced functionality or features are enabled, without necessarily enabling such advanced features in the remainder of the large display. What is further needed is a display system and method that provides these advantages without requiring the user to perform additional actions or commands beyond normal window manipulation that is done in the context of user interface interaction.  
     SUMMARY OF THE INVENTION  
      The present invention combines a main image, which may be of relatively low resolution, with one or more windows which are presented in relatively high resolution and/or which have one or more advanced features not found in the main image. In one embodiment, the final image is generated using two or more projectors, at least one of which displays the main display image and at least one of which is pointed and zoomed to display one or more windows in a region within the main display image area.  
      In one embodiment, the main display image is of relatively low resolution. One or more windows are provided, which are smaller, movable, zoomable areas within the main display image area. One or more of these windows are displayed at a higher resolution than the main display image. Alternatively (or in combination with the high-resolution capability), one or more windows may have additional display capability beyond that of the main display image. For example, a window may have the capability to display full-motion video whereas the main display image may not. A window may have color capability whereas the main display image may be monochrome (black-and-white). Other examples and variants will be apparent to one skilled in the art.  
      In one embodiment, the invention is implemented by providing a main projector, or “workspace projector”, that displays the main display image on a large screen. In one or more regions, the workspace projector leaves holes or blank areas where no light is projected on the screen. One or more window projectors display the high-resolution work areas within the blank areas. The window projectors are moveable and zoomable so that they can be directed toward specific locations on the screen.  
      In one embodiment, window regions follow an on-screen window that is currently accepting input or is currently the top-most window. For purposes of the description herein, such a window is referred to as having focus, or being the focus window. Thus, in a multi-window operating system, the window currently having focus is displayed at high resolution, while the remainder of the screen is displayed at lower resolution. If the window having focus is moved or resized, the window projector adjusts the position and/or size of the displayed high-resolution area accordingly, and the workspace projector moves and/or resizes its blank area accordingly. If a different on-screen window is given focus, the window projector starts displaying that window instead of the window that previously had focus; the workspace projector adjusts its image accordingly as well. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings illustrate several embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
       FIG. 1  depicts an example of an arrangement of projectors to generate a composite image according to one embodiment of the present invention.  
       FIG. 2  depicts an example of a composite image containing a main image and two windows.  
       FIG. 3  depicts an example of a pan/tilt mechanism, coupled to a high-resolution projector for generating a high-resolution component of the composite image according to one embodiment of the present invention.  
       FIG. 4  depicts an example of a composite image having two levels of resolution.  
       FIG. 5  depicts a detail of an area of the composite image of  FIG. 4 .  
       FIG. 6  depicts an example of output from a lower-resolution projector for generating a workspace component of the composite image.  
       FIG. 7  depicts an example of a transition from one focus window to another, according to one embodiment.  
       FIG. 8  depicts an example of an embodiment using multiple lower-resolution projectors and multiple high-resolution projectors.  
       FIG. 9  depicts an embodiment wherein a flat-panel display is used instead of a workspace projector. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
      The present invention is now described more fully with reference to the accompanying Figures, in which several embodiments of the invention are shown. The present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather these embodiments are provided so that this disclosure will be complete and will fully convey the invention to those skilled in the art.  
      In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form in order to avoid obscuring the invention.  
      Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.  
      Some portions of the detailed description that follows are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.  
      It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.  
      The present invention also relates to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions, and each coupled to a computer system bus.  
      The algorithms and modules presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatuses to perform the required method steps. The required structure for a variety of these systems will appear from the description below. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. Furthermore, as will be apparent to one of ordinary skill in the relevant art, the modules, features, attributes, methodologies, and other aspects of the invention can be implemented as software, hardware, firmware or any combination of the three. Of course, wherever a component of the present invention is implemented as software, the component can be implemented as a standalone program, as part of a larger program, as a plurality of separate programs, as a statically or dynamically linked library, as a kernel loadable module, as a device driver, and/or in every and any other way known now or in the future to those of skill in the art of computer programming. Additionally, the present invention is in no way limited to implementation in any specific operating system or environment.  
      In one embodiment, the present invention generates a composite image including at least one low-resolution component and at least one high-resolution component. The following description sets forth the invention in terms of such an embodiment. However, one skilled in the art will recognize that other variants of the invention are possible, including those in which the composite image includes components having differing characteristics other than resolution levels; for example, the composite image may include at least one monochrome component and at least one color component. Accordingly, the following description, which refers to differing resolution levels, is intended to be illustrative of merely one example of an embodiment, and should not be considered to limit the invention to generation of composite images having differing resolution levels.  
      Referring now to  FIG. 1 , there is shown an arrangement of projectors  101 A-C according to one embodiment of the present invention, to generate composite image  104 . A desktop version of the invention would comprise a desk-like projection surface with projectors  101 A-C embedded in the desk (not shown). Projectors  101 A-C are connected to image source  105 , which may be a frame buffer, computer, video source, or the like. Image source  105  provides the image that is to be displayed by projectors  101 A-C. Although one image source  105  is shown in  FIG. 1 , one skilled in the art will recognize that any number of image sources  105  can be provided in connection with the present invention. For example, one projector  101 A may obtain its image from one image source  105 , whereas another projector  101 B may obtain its image from a different image source  105 . In another embodiment, image source  105  uses a common image and divides it into component parts, each of which is to be displayed by one of projectors  101 A-C; image source  105  then transmits the appropriate component part of the image to each of projectors  101 A-C. Projectors  101 A-C are also connected to a control computer  106  for controlling the position and zoom of each projector  101 A-C.  
      One projector  101 C (also referred to herein as a “workspace projector”) projects the workspace display image  102 , for example a display area having dimensions of five feet by three feet and having resolution of 1280 pixels by 768 pixels (approximately 21 pixels per inch resolution). In the example shown, two additional projectors  101 A and  101 B project windows  103 A and  103 B at higher resolution (for example, 1280 pixels by 1024 pixels). Depending on the size of windows  103 A and  103 B, the resolution in pixels per inch for these areas can be significantly higher than the resolution of workspace display image  102 . For example, for a window size of 14 inches by 12 inches, the resolution within the window would be approximately 85 pixels per inch. In general, each window  103 A,  103 B is smaller in size than overall image  104 .  
      As described in more detail below, windows  103 A and  103 B are movable and resizable, either by moving and/or adjusting projectors  101 A and  101 B or by moving and/or adjusting optical apparatuses, such as mirrors and zoom lenses.  
      In one embodiment, workspace projector  101 C does not display anything in the area occupied by windows  103 A and  103 B, leaving blank areas or “holes” so as to avoid overlapping with the images generated by window cameras  101 A and  101 B. The particular characteristics of such blank areas depend on the display technology being used, so as to ensure that there is no interference with displayed windows  103 A,  103 B. For instance, when using projectors and a screen, workspace projector  101 C shines no light in areas corresponding to windows  103 A,  103 B, since such light could interfere with the image projected by high-resolution projectors  101 A,  101 B. In embodiments where a display device other than a projector is used to display workspace display image  102 , such as for example a liquid crystal display (LCD) screen or organic light-emitting diode (OLED) display screen, the LCD or OLED elements in areas corresponding to windows  103 A,  103 B are turned off, again so as not to interfere with the image of workspace display image  102 . Throughout this specification, the area where no image is projected, or where a neutral color is projected so as not to interfere with another projector, is referred to as a “blank” area. Workspace projector  101 C moves and resizes these blank areas in conjunction with the movement and resizing of windows  103 A and  103 B.  
      Referring now to  FIG. 2 , there is shown an example of a composite image  104  containing a workspace display image  102  and two windows  103 A and  103 B, as might be generated by the projector arrangement shown in  FIG. 1 .  
      The examples of  FIGS. 1 and 2  depict an arrangement wherein two windows  103 A and  103 B are displayed as part of overall image  104 . However, one skilled in the art will recognize that the present invention can be used in connection with one window, or with any number of windows. In one embodiment, one projector  101  is provided for each window, and one projector  101  (the “workspace projector”) is used to generate workspace display image  102 . In another embodiment, one projector  101  is provided for generating two or more windows  103 A,  103 B, and one projector  101  (the “workspace projector”) is used to generate workspace display image  102 . In yet another embodiment, two or more projectors  101  can be used for windows, and two or more projectors  101  can be used to generate the workspace display image  102 , according to known techniques for employing multiple projectors to construct a single image.  
      According to one embodiment, the invention is used for displaying a screen having one or more windows, as in a conventional graphical user interface. A window projector  101 A is used to display the currently active window (i.e., the window that currently has focus, also referred to herein as the “focus window”); all other windows (if any) are displayed by workspace projector  101 C. If the user changes focus, for example by clicking on another window on the screen to make it the active window, workspace projector  101 C takes over the task of displaying the previously active window, allowing window projector  101 A to pan and zoom over to the location of the newly selected window. Once oriented correctly, window projector  101 A takes over the display of the newly active window, and workspace projector  101 C displays nothing within the region occupied by the newly active window.  
      In one embodiment, the present invention is implemented using one or more projectors such as the LP250 from InFocus of Wilsonville, Oreg. In one embodiment, the image is projected onto one or more projection screens such as those available from Rose Brand of New York, N.Y.  
      Referring now to  FIG. 3 , there is shown an example of a pan/tilt mechanism  302  according to one embodiment of the present invention. In one embodiment, instead of moving the entire display mechanism of projector  101 A (and other projectors), a mirror  301  is mounted on a pan/tilt mechanism  302  and placed in such a way that the image from projector  101 A is reflected onto the screen in the appropriate location. Pan/tilt mechanism  302  is coupled to and controlled by control computer  106 . If the high-resolution window is resized, in one embodiment projector  101 A is moved closer or farther away from the screen. Alternatively, projector  101 A may include zoom lens mechanism  303  allowing the image projected from projector  101 A to be made larger or smaller as needed. Both zoom lens mechanism  303  and pan/tilt mechanism  302  can be motorized and steered in such a way that the high-resolution window image from projector  101 A appears in the correct location and at the correct size in the workspace image.  
      In one embodiment, the configuration of pan/tilt mechanism  302 , and the location of projector  101 A are established such that the image from projector  101 A can be steered to any location in the workspace image. Control computer  106 , after determining the location of the high-resolution window, calculates the correct angle and zoom of pan/tilt mechanism  302  and zoom lens mechanism  303 . Motors in pan/tilt mechanism  302  and zoom lens mechanism  303  are activated to drive each device to the proper position, allowing the window to be resized and located properly. When the high-resolution window is to be moved, new values for the pan/tilt and zoom are calculated, and the devices are moved to the new, correct positions. In one embodiment, pan/tilt mechanism  302  is implemented using a PTU-46-17.5 high-speed pan/tilt unit, available from Directed Perception of Burlingame, Calif., along with appropriate software for controlling pan/tilt angles. In one embodiment, projector  101 A includes a motorized zoom lens  303 ; alternatively, a motor can be added to a mechanical zoom lens on an existing projector. Driving mechanical systems with a computer-controlled motor is well understood in the art.  
      If projector  101 A lacks a zoom lens, it can be placed closer to the screen than the workspace projector  101 C. In this way, the resolution of the image coming from projector  101 A will be higher than the image from the workspace projector  101 C. Smaller windows can be projected by restricting the displayed image to a subset of the total display area of the projector and blacking out or turning off the pixels outside of the smaller window.  
      In one embodiment, adjustments are made to window  103 A from projector  101 A so as to account for “keystoning.” Keystoning is a well-known phenomenon wherein images on a screen formed by a projector are distorted if the projector and screen are not perfectly aligned. For instance, as the front of the projector is elevated, the top part of the projected image appears to widen. This is due to the increased distance from the lens to the screen at the top of the image. Most projectors have electronic adjustments to counter the keystoning effect; one example is the Canon LV-7215 projector made by Canon USA, Inc. of Lake Success, N.Y., USA.  
      When window  103 A from projector  101 A is moved from one location to another, in one embodiment window  103 A is “de-keystoned” so that it remains rectangular on the screen. There are well-known ways of de-keystoning, including for example redrawing the window so that edges of the window that would be elongated are shortened before they are displayed. In other words, the window being projected is distorted in such a way as to counter the keystoning effect, so that the final window  103 A is rectangular. Since different types and degrees of keystoning may occur depending on the position and size of window  103 A, this de-keystoning operation may be performed every time window  103 A is moved or resized. Where appropriate, similar adjustments are made to the blank area of workspace display image  102 , projected by projector  101 C.  
      Referring now to  FIG. 4 , there is shown an example of a composite image  104  generated by an embodiment of the present invention. Image  104  includes window  103 A, which currently has focus and is displayed at high resolution. Image  104  also includes workspace display image  102  and windows  103 B,  103 C,  103 D, which do not currently have focus and are displayed at lower resolution.  
      Referring now to  FIG. 5 , there is shown an enlarged detail  502  of an area  501  of composite image  104 , for illustrative purposes. It can be seen from detail  502  that window  103 A is presented at higher resolution than are windows  103 B,  103 C, and workspace display image  102 . The invention thus provides higher resolution for that section of image  104  that is currently of greatest importance, namely window  103 A, without requiring a large high-resolution display of entire image  104 .  
      As described above, in one embodiment a composite image  104  such as that shown in  FIG. 4  is generated using two projectors: a workspace projector  101 C for displaying workspace display image  102 , and a second, high resolution projector  101 A for displaying window  103 A. One skilled in the art will recognize that workspace projector  101 C is not necessarily of lower resolution than projector  101 A; however, since the image generated by workspace projector  101 C covers a larger area than the image generated by projector  101 A, in general the effective resolution of the image generated by projector  101 A will have a higher degree of resolution.  
      Referring now to  FIG. 6 , there is shown an example of workspace display image  102  displayed by workspace projector  101 C. Workspace display image  102  includes all areas of image  104  other than the region occupied by window  103 A of  FIG. 4 . Area  601 , corresponding to the location of window  103 A of  FIG. 4 , is left blank, as described above, so as not to interfere with the image from high-resolution projector  101 A (not shown in  FIG. 6 ). Area  601  is shown white in the Figure for clarity; however, as described above area  601  is generally colored black or whatever color does not interfere with the display of high-resolution windows.  
      Referring again to  FIG. 3 , there is shown an example of high-resolution projector  101 A displaying window  103 A. Control computer  106  controls mirror  301  to place window  103 A in the appropriate location. Thus, window  103 A overlays area  601  generated by workspace projector  101 C, so as to form composite image  104  as shown in  FIG. 4 . Since projector  101 A is dedicated to displaying window  103 A and need not display other portions of image  104 , the resolution of window  103 A can be maximized.  
      When focus changes from one window  103  to another, for example in response to a user clicking on a window  103  other than the one that currently has focus, high-resolution projector  101 A switches to display the window  103  that has been given focus. If appropriate, the image generated by projector  101 A is moved (by, for example, using control mechanism  302  to move mirror  301 ) so that the image is properly positioned at the location of window  103  that currently has focus.  
      Focus can change from one window  103  to another in response to other types of events as well. For example, a window  103  may become active in response to some event either internal or external to the operation of the computer, such as when a new window is created because new output becomes available, or a new dialog box is displayed, or a message in the window changes and is of sufficient importance that it is to be shown in high resolution.  
      Referring now to  FIG. 7 , there is shown an example of a technique for transitioning from one focus window to another, according to one embodiment. In the example of  FIG. 7 , images  801 A,  801 B, and  801 C are generated by high-resolution projector  101 A at different times, and images  802 A,  802 B, and  802 C are generated by workspace projector  101 C at respective different times.  
      Initially, in the example of  FIG. 7 , window  103 A has focus. Workspace projector  101 C displays image  802 A, including all windows and background except for window  103 A. The area corresponding to the position of window  103 A is left blank, leaving a place for projector  101 A to display window  103 A. Projector  101 A displays image  801 A corresponding to window  103 A in the area left blank by projector  101 C. Area  803 A is shown white in the Figure for clarity; however, as described above area  803 A is generally colored black or whatever color does not interfere with the display of high-resolution windows. The combination of images  801 A and  802 A yields a complete image wherein window  103 A has focus and is displayed at high resolution.  
      In response to the user indicating that window  103 B should be given focus, for example by clicking on window  103 B using a cursor or pointing device, high-resolution projector  101 A stops displaying window  103 A, possibly by turning off the projection completely. Control computer  106  causes zoom lens mechanism  303  and pan/tilt mechanism  302  to adjust (and mirror  301  to be repositioned) so that projector  101 A can properly display window  103 B instead. While zoom lens mechanism  303  and pan/tilt mechanism  302  are in transition, image  802 B is displayed by the workspace projector  101 C. Image  802 B is complete in that all windows, including  103 A and  103 B, are shown, and no blank or neutral areas are left to be displayed by high-resolution projector  101 A. In one embodiment, image  801 B (an all-blank image) is transitional and is displayed for only a brief period of time while mirror  301  is repositioned.  
      Once mirror  301  and zoom lens mechanism  303  are in position, images  801 C and  802 C can be displayed. Since window  103 B now has focus, high-resolution projector  101 A begins to display window  103 B at high resolution as shown in  801 C. Workspace projector  101 C displays image  802 C, including workspace component  102 . Workspace display image  102  now includes all areas of the image other than area  803 C, corresponding to the position of window  103 B. Workspace projector  101 C leaves area  803 C blank. The combination of images  801 C and  802 C yields a complete image wherin window  103 B has focus and is displayed at high resolution.  
      Of course, one skilled in the art will recognize that two or more high-resolution projectors  101  can be provided, so that both windows  103 A and  103 B can simultaneously be displayed at high resolution. In such an embodiment, a switch in focus may not necessarily cause a projector  101 A to be repositioned or to change the window it is displaying.  
      When a user moves or resizes a window  103  that currently has focus, control computer  106  moves mirror  301  and zoom lens mechanism  303  so that projector  101 A can continue to display the window  103  having focus. In one embodiment, the resolution of the focus window  103  is adjusted based on the current size of the window  103 , so that maximum use is made of the capabilities of the high-resolution projector. For example, the total number of pixels presented in window  103  can be held constant, so that when window  103  is made smaller, effective resolution per unit screen area is increased.  
      Concurrently, the blank portion of workspace display image  102  generated by workspace projector  101 C is moved so that projector  101 C leaves blank the area of the display corresponding to the window  103  that has focus.  
      The present invention provides several advantages over prior art techniques. As indicated, it provides high-resolution for large-scale displays, while avoiding the prohibitive cost of providing high-resolution over the entire display. It integrates well with existing window-based user interfaces, wherein a particular area of a screen (a window having focus) is known to be of greater interest to the user than the rest of the screen. In addition, the border between the focus window and the adjacent area of the screen provides a natural boundary that minimizes the discontinuity between the higher- and lower-resolution displays.  
      The high-resolution portion of the display moves naturally and in an intuitive manner when the user moves or resizes the window having focus, or when the user changes focus to another window; thus the user need not learn any new techniques in order to operate the invention. The user need not explicitly specify or designate a particular area of the screen image  104  to be displayed at high resolution, and need not move a focus window (not shown) to any particular area of the screen in order to see it in high resolution. Rather, the appropriate area to display at high resolution is implicit in the user&#39;s activation of a window, an operation that is commonly made in the normal course of interaction with a window-based user interface. Control mechanism  302  is driven by window manager move/resize/pop requests, as provided by conventional operating systems, so that the invention can be easily integrated with existing window management software. By adjusting resolution based on the current size of the window, maximum use is made of the capabilities of the high-resolution projector.  
      One skilled in the art will recognize that many variants and alternative embodiments are possible. For example, referring now to  FIG. 8 , there is shown an embodiment using multiple workspace projectors and multiple high-resolution projectors. The main display image  104  is divided into six sections  102 A-F, which may or may not overlap. Each section  102 A-F is generated by a different workspace projector (not shown in  FIG. 8 ). Additional high-resolution projectors (not shown in  FIG. 8 ) generate the display of windows  103 A and  103 B. The six workspace projectors leave blank the areas corresponding to windows  103 A and  103 B. Thus, the combination of six workspace projectors and two high-resolution projectors generates the final image  104 .  
      One advantage of a display as shown in  FIG. 8  is that windows  103 A and  103 B are seamless. Thus, even if a transition, or seam, is visible between sections  102 A-F projected by workspace projectors, the seam is eliminated from those areas of the image that are of prime importance (windows  103 A and  103 B).  FIG. 8  is therefore exemplary of a technique using the principles of the present invention that can be extended to create very large displays wherein certain key portions of the display are shown at high resolution.  
      Referring now to  FIG. 9 , there is shown an embodiment wherein a flat-panel display  1000  (or other display technology) is used instead of workspace projector  101 C. Window projector  101 A projects window  103 A onto the surface of display  1000 . Display  1000  leaves blank the area occupied by window  103 A, in the same manner as described above for workspace projector  101 C. As described above, control mechanism  302  (not shown in  FIG. 9 ) is used to move and resize the output of projector  101 A, and display  1000  moves its blank area accordingly. As described above, more than one window projectors, such as  101 A, can be used.  
      Other variations are possible, as will be apparent to one skilled in the art. For example, in one embodiment, rather than (or in addition to) providing a higher degree of resolution, window projector  101 A can provide some other characteristic, capability, or feature that is not provided by workspace projector  101 C. For example, it may be desirable to display, in window  103 A, motion picture output from a video source (such as a DVD player), while the remainder of workspace display image  102  is output from a computer source. Window projector  101 A provides the video output in window  103 A, while workspace projector  101 C displays the remainder of workspace display image  102 , leaving blank the area occupied by window  103 A. As described above, window  103 A can be movable and resizable, so that control mechanism  302  is employed to move the image presented in window  103 A according to such movements and resizing. Similarly, as described above, the blank area is moved accordingly.  
      As will be apparent to one skilled in the art, window projector  101 A can provide other characteristics, capabilities, or features not provided by workspace projector  101 C. For example, window projector  101 A might have color capability, while the remainder of workspace display image  102  is shown in monochrome. Alternatively, window projector  101 A might have any other visual characteristic that is not provided by window projector  101 A. Thus, when color (or another visual characteristic) is desirable but too expensive for the entire image, the present invention allows color to be provided in those areas of the screen currently having focus, without wasting such capability on the rest of the image.  
      One potentially useful application is to provide a system for radiologists and doctors to read X-rays. X-rays are high-resolution, high-contrast monochrome images. Other user interface elements that may be appropriate to display on-screen along with X-rays are more suitable for color display. In one embodiment, therefore, a monochrome projector providing high-resolution, high-contrast images for the X-rays is employed for displaying one or more windows, whereas the workspace display image is displayed in color at a lower resolution.  
      Other embodiments are also possible. In some embodiments, the invention is implemented in such a way that it operates independently of any on-screen windows, and can operate in the absence of any on-screen windows. In such embodiments, regions  103 A and  103 B (as shown in  FIG. 1 ), represent areas within image  104  that are not windows and do not necessarily correspond to windows. If desired, no window border need be displayed at the edges of regions  103 A and  103 B. Positions and sizes of regions  103 A and  103 B can be controlled by user operation of a pointing device or other input device, which causes control computer  106  to reposition and re-zoom projectors  101 A and  101 B accordingly.  
      Such embodiments operate in a similar manner to the techniques described above, with projectors  101 A,  101 B projecting images for regions  103 A and  103 B, and projector  101 C projecting workspace display image  102 . Regions  103 A and  103 B may be of higher resolution than workspace display image  102 , or they may have some other characteristic not present in workspace display image  102 . Image source  105  provides the image that is to be displayed by projectors  101 A-C. As described above, more than one image source  105  may be provided; for example, projector  101 A may obtain its image from a regional image source  105 , projector  101 B may obtain its image from another regional image source  105 , and projector  101 C may obtain its image from a workspace image source  105 .  
      According to one example of such an embodiment, projector  101 A projects an infrared camera image in region  103 A, while projector  101 C projects a visible-light workspace display image  102  (leaving blank the area occupied by region  103 A).  
      According to another example, workspace projector  101 C displays a panoramic image (such as one from a panoramic video camera), leaving an area blank. Projector  101 A displays an image in the blank area from a different video source trained at a portion of the panoramic area such that a higher-resolution (or higher-frame rate) view of the area is displayed in region  103 A.  
      In either of these examples, the system can be implemented without showing a visible border around region  101 A, so that region  103 A is an arbitrary area of overall image  104 .  
      It will be understood by those skilled in the relevant art that the above-described implementations are merely exemplary, and many changes can be made without departing from the true spirit and scope of the present invention. Therefore, it is intended by the appended claims to cover all such changes and modifications that come within the true spirit and scope of this invention.