WO2000079791A1

WO2000079791A1 - Freeze-frame function in an electronic projection system

Info

Publication number: WO2000079791A1
Application number: PCT/US1999/023476
Authority: WO
Inventors: David Dashefsky; Timothy L. Mccullough
Original assignee: 3M Innovative Properties Company
Priority date: 1999-06-17
Filing date: 1999-10-07
Publication date: 2000-12-28
Also published as: AU6511899A; WO2000079791A9

Abstract

A method and an electronic presentation system for facilitating electronic projection presentations. The presentation system comprising an electronic projection system having a video frame buffer and a computer electronically coupled to the electronic projection system. The method includes the steps of transmitting a first image from the computer into the video frame buffer of the electronic projection system and storing the first image in the video frame buffer. The first image then is projected using the electronic projection system. A first command may be issued to the electronic projection system to maintain the first image in the video frame buffer and to ignore any other images transmitted by the computer, while continuing to project the first image using the electronic projection system.

Description

FREEZE-FRAME FUNCTION IN AN ELECTRONIC PROJECTION SYSTEM

BACKGROUND OF THE INVENTION

The present invention relates generally to the electronic presentation of viewable images to an audience. More specifically, the present invention relates to an electronic presentation system and a method for implementing a freeze-frame feature in an electronic projection device.

Overhead projector / film-based presentation has been in existence since early 1960s. The presentation style established at that time is still with us today. Specifically, a presentation outline is prepared, then visual aids, such as 8 1/2 by 11 -inch slide transparencies, are prepared to help the presenter communicate the message to the audience. The transparencies typically are organized in sequence. A careful presenter may prepare private notes and "back up transparencies" that the presenter could use to answer various questions as they arose. This "talk and show" presentation style was simple and quite user-friendly and naturally formed the basis for new presentation technologies.

More recently, LCD multimedia projectors have started to be used for presentations. The transparency slides, which once were actual pieces of film, were replaced by images on a computer. To present these slide images to the audience, the video port of the presenter's computer is connected to an LCD projector, such as via a 15 pin D-Sub cable. Connected in this manner the LCD projector receives and simultaneously attempts to display whatever image is showing on the computer's native screen, at the same resolution. This "computer based presentation" has grown in popularity as projection quality has increased and proj ector cost has decreased.

Computer based presentation has many advantages. However, the fact that the projector connected to the video port duplicates the computer screen's image exactly, also has limited the presenter's flexibility. Any action performed by the presenter, be it rearranging or manipulating a slide, is displayed simultaneously to the audience. Similarly, any presenter's notes displayed on the computer screen are no longer private. The presenter therefore may be unable to modify the presentation images and may be forced to maintain them in a preset sequence. In this "single view" mode the presenter is deprived of the flexibility of having a private perspective that would allow him/her to view and manipulate computer speaker notes and skip or add slides. Also, since the image transmitted to the projector has the same resolution as the native screen image, another limitation is lack of assurance of compatibility between the computer and the projector. Both computer screens and projectors are available in several resolutions, e.g. VGA (640x480 pixels), SVGA (866Ox6OO) or XGA (1024x768). When the resolution of the native computer screen, and thus the resolution of the image transmitted out of the video port, does not match the resolution of the projector, the projected image is degraded. Traditional projectors try to correct for resolution differences through the use of scaling algorithms implemented using hardware and/or software. However, presently, scaling algorithms still provide a degraded image with respect to the native resolution. Image degradation becomes even more apparent and problematic when the image is projected onto a large screen.

Commercially available presentation software usually has two basic modes; authoring mode and presenting/presentation mode. The authoring mode is the most powerful mode since it is where the presenter prepares the images that help to reinforce the presenter's speech/viewpoint. In the authoring mode the author creates the slides that include supportive visual aids. These visual aids may include text, charts, images and other visual objects that emphasize or explain a particular point. Many times visual aids, also referred to as objects or bullet points, are coded to appear onto a slide in a certain sequence predetermined by the author. This allows the presenter to use the slide to make his/her point premise by premise. Likewise the sequence of slides is important; and common authoring software allows the author to arrange the slide sequence prior to the presentation. The author may code certain slides to be 'hidden' (i.e., not shown) during presentation mode. To add drama and artistic flair the slides may be coded to transition smoothly from one to another, such as using a fade, rather than just jump to the next slide. During the presentation mode the slides are displayed in the predetermined authored sequence using the predetermined transition. Further the bullets/objects within each slide likewise are displayed in their predetermined sequence. The presenter does not have the ability to modify, or "re-author", the presentation transparently without leaving the presentation mode. The presenter, by way of a keystroke or mouse click, may control the transition from slide to slide and bullet/object to bullet/object. For the purpose of the present description, the appearance of a new object onto a slide, or the transition of one slide to another will both be referred to as an "image transition", since the image that is being viewed by the audience has transitioned to another image.

The presentation described above appears on the computer screen of the presenter. As described above, to show the presentation to a large audience the same image usually is sent, raster line by raster line, to a multimedia projectors via the 15 pin D-Sub connector. Due to the large variety of computers and changing video standards, the image data may come at various rates. The multimedia projector must then synchronize the frame rate of this input signal with the frame rate of the LCD imaging devices.

One method to accomplish the synchronization is the use of a video frame buffer. As the image data is received from the computer, an electronic version of the image is written into the video buffer at the rate dictated by the computer. This image data is then read out of the buffer at a rate optimal for the LCD imaging devices. For this type of hardware design a complete image replica of the computer screen exist in the projector's video buffer for a very short period of time. This image is updated very rapidly, usually about every 1/60* of a second. Current video frame buffers still do not resolve resolution discrepancy image degradation.

During a typical presentation the presenter first will show a slide/bullet point, discuss the content and the meaning of the slide/bullet, and then proceed to the next slide/bullet.

While a slide is being discussed, the same slide appears to remain on the screen. However, the computer actually continues to transmit raster image information every 1/60* of a second.

Several methods have attempted to address the limitations of single view, single resolution presentations. One method includes creating a custom presentation computer having two video boards and two corresponding video ports, one for the presenter's screen and one for the multimedia projector. This method is relatively expensive and requires a custom-modified computer. Another method is to incorporate a video driver in a PCMCIA card. This method also is relatively expensive, requires custom modifications and hinders ease of use.

Still another method is to use a "smart" projector having independent memory and image processing capabilities. A database of duplicate, resolution independent images then may be stored in the smart projector. The presenter, while not able to manipulate the images, may remotely signal the projector to present the appropriate slide while maintaining independent notes in the presenter's own computer. This method, albeit useful, requires in fact two image management systems, one for the presenter and one incorporated inside the projector. The method does not work well for ceiling mounted projectors or other projectors that are difficult to access and increases the cost of the projector.

There remains a need for a solution that would operate with most commercially available computers and operate with popular authoring and presentation software.

Ideally, the solution would give the presenter the freedom to have a private view including the audience's view, a view of the next slide in sequence, and speaker notes, while allowing the presenter to manipulate the slides privately. It also would be desirable to have a system that would correct automatically for any mismatch between the computer and the projector.

SUMMARY OF THE INVENTION

The present invention relates to a method and an apparatus for facilitating electronic projection presentations with an electronic presentation system. The presentation system includes a computer and an electronic projection system.

In an exemplary embodiment, the computer may include a central processing unit having a video output. The computer may further include a user video display unit coupled to receive and display images transmitted by the video output. The electronic projection system includes illumination and projection optics, one or more imagers and an image buffer. The electronic projection system is coupled to the computer to receive and display the image frames transmitted by the video output. The electronic projection system further may be coupled to the computer to receive a control commands.

The electronic projection system includes hardware and/or software, wherein upon receipt of a first control command the image buffer retains a last image frame transmitted 5 by the video output prior to the reception of the first command and the electronic projector continues to display the last image frame.

The method of the present invention comprises the steps of transmitting a first image frame from the computer and storing the image frame into the video frame buffer of the electronic projector. The electronic projector projects the first image frame onto an 0 audience screen. The user or the computer then may issue the first command to the electronic projector. Upon receipt of the first command, the projection system maintains the first image frame in the video frame buffer and ignores any other image frames transmitted by the computer. The projection system continues to project the first image frame stored in the video frame buffer. Meanwhile, the video display unit continues to 5 display images transmitted by the computer after the transmission of the first command.

The method further may include the step of transmitting a second command. Upon receipt of the second command, the electronic projection system resumes accepting other image frames transmitted by the computer. These new image frames are stored in the video frame buffer and are displayed by the projection system. The commands may be o issued by the user using a control panel or remote control, or may be programmed to be issued by the computer.

In an exemplary embodiment, the computer is programmed to automatically switch from a presentation or display mode to an authoring or presenter mode upon issuance of the first command. Similarly, the computer may be programmed to switch to display 5 mode in conjunction with the issuance of the second command. In a preferred embodiment, the computer is programmed to automatically switch to display mode prior to allowing the image buffer to accept new image frames, thus maintaining a transparent image transition to the audience. The computer may be further programmed to then transmit a new image frame or slide, again issue the first command, and automatically o return to authoring mode. The electronic projection system may have a first image resolution and the video display unit may have a second image resolution. In such case, the computer also may be programmed to switch to the resolution of the projector during display mode and to the resolution of the video display unit during the authoring mode. The present invention encompasses a computer program product for controlling the electronic projection system coupled to the computer. The computer program product includes a computer usable medium having computer readable program code for causing a computer to transmit digital images; and computer readable program code for causing a computer to transmit a first control signal instructing the electronic projector to continue to display a received digital image and to ignore further transmitted digital images.

The computer program product further may include computer readable code for causing the computer to transmit a second control signal instructing the electronic projector to receive and display transmitted digital images. The computer program product also may include computer readable code for causing the computer to launch a presenter interface upon transmission of the first control signal and for causing the computer to launch the second control signal upon launch of a presentation interface. A plurality of said digital images are presentation slides. The product may further comprise computer readable code for causing the computer to transmit the first control signal upon transmission of each of the presentation slides.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic diagram of an electronic presentation system in accordance with the present invention.

Figure 2 is a block diagram representing the flow of presentation images in accordance with the present invention.

Figure 3 is a flowchart of an exemplary embodiment of a method in accordance with the present invention. Figure 4 is a schematic diagram of the electronic projection system of Fig. 1 during an exemplary use of a method in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION Figures 1 and 4 illustrate an electronic presentation system 100 in accordance to the present invention. The electronic presentation system 100 includes a personal computer 10 and an electronic projector 30. The personal computer 10 includes a central processing unit (CPU) 12 and a video display terminal 14. The CPU 12 may include a microprocessor, memory, and a video graphics card. The computer 10 also may include an alphanumeric input device (e.g., keyboard) 16, a mouse 18, a resident data storage device 20, such as a hard disk, and a removable data storage read/write device 22, such as a floppy disk driver. An additional input device, such as an infrared remote controller or a stylus also may be included in the personal computer 10. The computer 10 also includes appropriate software, such as an operating system, stored within the computer memory and/or data storage devices. The computer 10 may be implemented using a laptop computer, such as a Thinkpad 560 laptop computer from IBM Corporation of Armonk, N.Y., running Windows 98 DOS and Microsoft Power Point presentation software, from Microsoft Corp. from Redmond, Washington.

In other exemplary embodiments, the present invention may be implemented using other types of computers or data processing systems, including, for example, a remote terminal or an internal processor integrated with the electronic projector. The use of intelligent workstations, mini-computers or other similar devices also is contemplated to be within the scope of the present invention.

Figure 2 illustrates in block diagram form the electronic connections of the electronic projection system 100. The electronic projector 30 includes an internal video buffer 32 electronically coupled to one or more imagers 34. The internal video buffer in the present exemplary embodiment is a random access memory device, such as DRAM, SGRAM, or

SDRAM, designed to store video image information. For the present exemplary embodiment, the projector 30 has a frame buffer 32 having a memory size at least equal to twenty-four (24) times the number of pixels in the native resolution (for a 24-bit color system) of a single image frame. The frame buffer is controlled by a frame buffer control unit. A VGA signal is interfaced from the video port of the computer 10 to the projector 30 through a High-Density 15 (HD 15) pin male connector. Analog signals for Red, Green, and Blue are available at this connector. In the projector 30, each analog color signal is sent to the input of an 8-bit analog to digital converter. On the output end of the analog to digital converter is a digital representation of the analog signal at a given moment of time (the pixel clock). The pixel clock period is determined by horizontal and vertical synch signals, that are also available on the HD- 1 5 connector, by matching the timing of the horizontal and vertical sync signals with a value in a table stored on the CPU in the system. This table is determined by existing video standards such as VESA. The output of the analog to digital converter is written into the frame buffer in a specific location based on the number of horizontal and vertical synch signals which have been received up to this point by a frame buffer control unit. At this time, the next pixel is available at the output of the Analog to digital converter.

The embodiment of the projector 30 also will have a CPU with the ability to receive and decode commands sent on a data link to the outside world, such as an RS232 cable. Incoming commands then may be executed. In the present embodiment, the CPU of the projector 30 has a freeze and an unfreeze command in the command set, which the CPU can decode. Control commands generally are represented by strings of bytes received serially specifying a function and any parameters that are necessary. Upon receipt and decoding of a freeze control command, the CPU of the projector will send signals to the frame buffer control unit to accept no new pixels and simply refresh the existing data in the image buffer. Upon receipt and decoding of an unfreeze command, the CPU will send signals to the frame buffer controller unit to begin accepting new pixels for the analog to digital converter. Exemplary imagers include transmissive and reflective liquid crystal displays

(LCDs), plasma imaging devices, and digital micro-mirror devices. Illumination and projection optics are arranged to project the picture displayed by the imager(s) 34 onto a screen 36 (Fig. 4). The term screen is meant to include any suitable projection surface, such as a specialized controlled reflection screen or a blank wall.

The electronic projector 30 includes an input signal port 40 electronically coupled to the video buffer 32. Likewise, the computer 10 includes a video output signal port 42 having a data connector, such as a 15 pin D-Sub connector. The computer video output port 42 is coupled to the input signal port 42 of the projector via a video/data connector cable 44, such as a VGA video cable. Additionally, a control cable 46, such as an RS-232 serial control cable, may electronically couple a control port 48, such as a serial port, of the computer 10 to a control port 50, such as a serial port, of the projector 30. The control port 48 of the computer 10 is coupled to the CPU 12, while the control port 50 of the projector 10 is coupled to the data buffer 32. In the present exemplary embodiment, the VGA video cable 44 carries a video image from the computer's video output port 42 to the projector's video input port 40. The RS-232 serial control cable 46 carries digital commands from the computer's serial port 48, to the projector's serial port 50.

An exemplary electronic projector 30 may be implemented using a commercially available projector, such as the 3M Model No. MP8625, from Minnesota Mining and Manufacturing in St. Paul, MN.

The projector 30 of the present invention has two modes, a simultaneous display mode and a freeze mode. During the simultaneous display mode, the video buffer 32 is updated approximately every 1/60* of a second with a new frame transmitted from the computer 10 through video output port 42. While, naturally, there may exist some minimal delay in transmitting and projecting the image, to the user's eyes the display of the image on the resident video display unit 14 and on the screen 36 are basically simultaneous. The image displayed by the projector 30 is the same as that displayed by the native video screen 14 of the computer 10. The computer 10 has the capability to send a digital (or analog) "Freeze" command over the RS-232 serial control cable 46, through some other serial or parallel data link such as USB or RS-422, or even through the video data cable 44, such as through the Display Data Channel. Alternatively, the presenter may use a remote control, such as control 38, either linked by a cable to the projector 30 or by an infrared or RF transmitter/receiver. Issuance of the Freeze command by the computer 10 may be activated by a user-inputted command, such as a keystroke or mouse click, a preprogrammed toggle input, or may be programmed to be automatically issued, for example, to follow the transmission of a selected slide(s). When the Freeze command is received by the projector 30, the projector 30 "locks" in the most recent image in the video buffer 32 preventing any updates. The video buffer 32 ignores any new images transmitted by the computer 10 and continues to transmit to the imager 34 the same raster data for the last image stored in the video buffer 32. In an exemplary embodiment, the projector 30 includes a basic CPU. The step of "freezing" the image buffer 32 is accomplished by instructing the projector's CPU, via software commands, to not place any more data into the frame buffer. Alternatively, the image buffer may be configured to have a "do not accept" mode, which may be switched upon receipt of the appropriate electronic command. The described step may be accomplished readily in a variety of ways by those skilled in the art. Similarly, the computer and/or the presenter may issue an "Unfreeze" command.

Upon receipt of the "Unfreeze" command, the projector 30 returns to simultaneous display mode. The Unfreeze command, when received by the projector 30, will unlock the video buffer 32, allowing the buffer 32 to be updated with new images.

The freeze mode may be implemented using a computer program that controls the functions of the image buffer 32. The program controls the frame/image buffer 32 through commands sent over the control cable or data link to the projector 30. In alternative embodiments, the same function may be implemented by the use of a hardware relay or switching mechanism. Figure 3 illustrates the logic steps involved in practicing a method for facilitating presentations in accordance with the present invention using the electronic presentation system 100. The method may be implemented through the use of hardware installed into the projector, such as the frame buffer and the logic implementation for the freeze function (the buffer control unit and CPU) and/or software installed into the computer.

The presenter prepares a presentation, which may include presentation slides, reserve slides, presenter notes and reference materials. The presentation may be authored using standard commercially available authoring software such as PowerPoint from Microsoft. The presenter stores the presentation on the computer 10 (for example, in the computer's memory or data storage devices). Alternatively, such as when explaining the operation of a software program or referencing an Internet page, the slides may comprise functional screen images and the step of preparing such images may comprise accessing such images.

When the presentation commences, the presenter displays a first slide on the resident video display terminal 14. The presenter, for example, may start the presentation using the projector 30 in the simultaneous-display mode or may toggle to such mode. The image is transmitted to the video buffer 32, which receives the image in step 110. The image is stored in the video buffer 32 (step 120) and displayed by the projector 30 (step 130). The same image appears in the presenter's video screen 14 and simultaneously is projected for the audience. As long as the projector 30 remains in the simultaneous display mode, the image buffer 32 will continue to receive and store new images transmitted by the computer 10. The presenter may discuss the present slide or update the projected image with a new slide or bullet point.

At some point, a Freeze command is issued, placing the projector 30 in Freeze mode. Step 140 illustrates the decision routing that occurs when the projector switches modes. Rather than continuing to receive new images, the projector 30 ignores any new image input and continues to display the last stored image. The switch to Freeze mode is transparent to the audience, who continues to see the current slide. With the projector 30 in Freeze mode, the presenter is then free to switch privately to a separate view, such as an authoring or presenter's mode. Figure 4 illustrates the operation of the method and the system of the present invention. The projector 30 is in freeze mode, automatically continuing to project the last active slide onto the screen 36. The raster information for this slide is stored in the buffer 32. Meanwhile, the presenter's private screen 14 may be used to display notes, other slides or other information. The presenter may have full authoring capability and may delete, add or reorder the slides or even change the content of the slides themselves.

Figure 4 shows a larger representation of an exemplary presenter's view in presenter's mode. The presenter's view includes a smaller version of the audience view (sometimes referred to as a 'thumbnail' view), speaker notes, a thumbnail version of the next slide, speaker notes accompanying the next slide, and a means to control the flow of the presentation (such as on-screen buttons having the following functions: return to the beginning, advance one slide, go back one slide, go to the end and pause). In an exemplary embodiment, the authoring software has been modified also to include a means, such as an on-screen menu or button, to jump to the presentation mode of the presentation software.

A further advantage of the software of the present invention is that, if the projector is a different resolution from the computer, the software will configure the video driver on the computer using the facilities of the operating system to match the resolution of the projector. Thus, the method of the present invention offers a user transparent mechanism for obtaining a proper image just prior to issuing the freeze command. The computer is switched to match to resolution of the projector by the software and then frozen. In this case the video driver of the computer is then reconfigured back to match the resolution of the resident computer screen prior to displaying the authoring view. The ability to switch back between the resolution of the projector and the resolution of the computer screen allows optimal use of both the projector and the computer without image degradation and without the use of scaling hardware or software. The presenter enjoys the freedom and full functionality of the authoring view, as exemplary described above in reference to Figure 4, until it is time for the next transition. Just prior to the next transition, the user returns to a presentation view and the Unfreeze command is issued. The authoring mode and the presentation mode may be implemented using two different software programs. Issuance of the Unfreeze command may be programmed to return control automatically to the presentation software or mode for the duration of the transition. At the end of the transition, the Freeze command may be issued and control automatically returned to the authoring software or mode. This present freeze- authoring mode-present-unfreeze flow process may continue for each selected slide/bullet until the presentation is terminated.

The method of the present invention may be equally applicable to facilitating presentation of "real-time" information. For example, a presenter may navigate and load images from the Internet or a computer program, while, at the same time describing a previously accessed image. This ability would allow for seamless presentations without apparent navigation or downloading delays.

Those skilled in the art will appreciate that the present invention may be used when facilitating previously prepared presentations, as well as when presenting "real time" images. While the present invention has been described with a reference to exemplary preferred embodiments, the invention may be embodied in other specific forms without departing from the spirit of the invention. Accordingly, it should be understood that the embodiments described and illustrated herein are only exemplary and should not be considered as limiting the scope of the present invention. Other variations and modifications may be made in accordance with the spirit and scope of the present invention.

Claims

WHAT IS CLAIMED IS:

1. A method for facilitating electronic projection presentations with an electronic presentation system (100), the presentation system comprising an electronic projection system (30) having a video frame buffer (32) and a computer (10) electronically coupled to the electronic projection system, the method comprising the steps of a) transmitting a first image from the computer into the video frame buffer of the electronic projection system; b) storing said first image in the video frame buffer-, c) projecting the first image using the electronic projection system; d) issuing a first command from the computer to the electronic projection system to maintain the first image in the video frame buffer and to ignore any other images transmitted by the computer; and e) continuing to project the first image using the electronic projection system.

2. The method of claim 1, further comprising the step of transmitting a second command to the electronic projection system and allowing the video frame buffer to accept other images transmitted by the computer.

3. The method of claim 1, wherein the computer includes a video display unit (14), wherein the video display unit displays images transmitted by the computer, and wherein the video display unit continues to display images transmitted by the computer after the step of issuing the first command.

4. The method of claim 1, wherein prior to the step of issuing the first command, the computer is in a display mode and upon issuing the first command, the computer automatically shifts to a presenter mode.

5. The method of claim 4, wherein the computer includes a video display unit having a first resolution and the projection system has a second resolution, wherein during the display mode the computer transmits images in the second resolution and during the presenter mode the computer transmits images in the first resolution.

6. The method of claim 4, further comprising the step of issuing a second command from the computer to the electronic projection system, the second command allowing the video frame buffer to accept other images; wherein in conjunction with the step of issuing the second command, the method includes the step of automatically returning the computer to the display mode.

7. The method of claim 6, further comprising the step of transmitting a second image from the computer to the video frame buffer, automatically followed by the step of again issuing the first command and returning the computer to the presenter mode.

8. The method of claim 1, wherein the computer is capable of issuing commands to the electronic projection system through the video output.

9. An electronic presentation system comprising: a) an electronic projection system (30) having an image buffer (32); b) a computer (10) having a video output (42) coupled to the image buffer, wherein the video output transmits image frames and wherein the electronic projection system is coupled to receive and display the image frames transmitted by the video output; and c) a display unit (14) coupled to the video output, wherein the display unit is coupled to receive and display the image frames transmitted by the video output; d) the electronic projection system being able to receive control commands from the computer, wherein upon receipt of a first control command the image buffer retains a last image frame transmitted by the video output prior to the reception of the first command and the electronic projection system continues to display the last image frame.

10. The electronic presentation system of claim 9, wherein the computer is capable of issuing the control commands through the video output.

11. The electronic presentation system of claim 1 0, wherein after issuing the first control command, the video output of the computer continues to transmit other image frames that are displayed by the display unit.

12. The electronic presentation system of claim 10, wherein prior to issuing the first control command the computer is in a presentation mode and wherein in conjunction with issuing the first control command, the computer automatically shifts to an authoring mode.

13. The electronic presentation system of claim 9, wherein upon receipt of a second control command the projection system receives and displays other image frames transmitted by the video output.

14. The electronic presentation system of claim 12, wherein the computer is capable of issuing a second control command allowing the electronic projection system to accept and display other image frames; wherein in conjunction with issuing the second control command, the computer processor automatically returns to the presentation5a second image frame from the computer to the electronic projection system, and then to issue automatically the first control command and return the computer to the authoring mode.

16. The electronic presentation system of claim 12, the electronic projection system having a first resolution and the video display unit having a second resolution, wherein during the presentation mode the computer transmits image frames in the first resolution and during the authoring mode the computer transmits image frames in the second resolution.

17. The electronic presentation system of claim 12, wherein the presentation mode engages a first computer program and the authoring mode engages a second computer program.

18. A computer program product for controlling an electronic projection system (30) coupled to a computer (10), the product comprising: a) a computer usable medium having computer readable program code for causing a computer to transmit digital images; and b) computer readable program code for causing a computer to transmit a first control signal instructing the electronic projection system to continue to display a received digital image and to ignore further transmitted digital images.

19. The computer program product of claim 18, further comprising computer readable code for causing the computer to transmit a second control signal instructing the electronic projection system to receive and display transmitted digital images.

20. The computer program product of claim 18 or 19, further comprising computer readable code for causing the computer to launch a presenter interface upon transmission of the first control signal.

21. The computer program of claim 20, further comprising computer readable code for causing the computer to launch the second control signal upon launch of the presentation interface.

22. The computer program product of any one of claims 18 to 21, wherein a plurality of said digital images are presentation slides, the product further comprising computer readable code for causing the computer to transmit the first control signal upon transmission of each of the presentation slides.