Abstract:
A document projector includes a feed through scanner having a document transport, an illumination source, and a linear image sensor for scanning and producing a digital color image of a document or transparency; a microprocessor connected to the scanner for processing the digital image and for overall control of the apparatus; a memory connected to the microprocessor for storing the digital document image; and a digital projector connected to the microprocessor for projecting the digital image.

Description:
FIELD OF THE INVENTION 
     This invention relates to document projectors and more particularly to digital electronic projectors. 
     BACKGROUND OF THE INVENTION 
     Today many business presentations requiring visuals are made using digital projection technology. While digital projectors are very costly, the quality is reasonably good and the convenience of being able to directly present slides prepared on a computer is attractive. However, many institutions such as schools or smaller businesses cannot justify the expense of such a device because of its limited capability and flexibility (only digital data files can be projected), and rely instead on overhead transparencies to make presentations. Overhead transparency projectors are relatively inexpensive but unless they are cleaned regularly and well maintained the image quality is often not very good and the preparation of transparencies, especially those in color made from computer files, is time consuming and quite costly itself in both time and materials. 
     There are further limitations to these two main presentation technologies. Digital projectors are limited in that they can only project a slide existing as a digital data file, normally residing on a personal computer hard drive, and overhead projectors can only project transparencies. Also, there are often last-minute additions which must be made to presentations, e.g. updated sales reports, recently published documents or advertising material, etc., and there may not be sufficient time to either convert the material to digital data files for projection by a digital projector or to a transparency for use with an overhead projector. It would be useful therefore to have a projector which is more flexible in the type of materials which could be projected. 
     One potential solution which addresses some of these limitations has been disclosed in Japanese laid-open patent application JP 09-294,236. The &#39;236 application discloses an apparatus which combines a document camera mounted in “copy stand” fashion on top of a digital projector. This device can capture a digital image of any object or document within the field of view of the camera and then subsequently project this digital image using the projector functionality. A significant limitation of this device, however, is the need to provide extra illumination for the camera. When such a projector is used in a darkened room, as is typical with digital projectors, the stray light from this illumination can detract from the quality of viewing. The overall image quality available from such a device is also impacted by the level and uniformity of this illumination, as well as by the resolution of the camera. The device is also typical of digital projectors in that it has no memory for the storage of multiple images. 
     These and other limitations of the prior art are addressed by the present invention. 
     SUMMARY OF THE INVENTION 
     The need is met according to the present invention by providing a document projector that includes a feed through scanner having a document transport, an illumination source, and a linear image sensor for scanning and producing a digital color image of a document or transparency; a microprocessor connected to the scanner for processing the digital image and for overall control of the apparatus; a memory connected to the microprocessor for storing the digital document image; and a digital projector connected to the microprocessor for projecting the digital image. 
     ADVANTAGES 
     The document projector of the present invention has the advantage that a high quality display can be easily produced from either transparent or opaque originals. Previously displayed images are immediately available electronically without the need to reposition the originals, and extra slides can be easily inserted into a presentation during the presentation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of the components of a document projector according to the present invention; 
     FIG. 2 is a flow chart illustrating one aspect of the operation of a particular embodiment of the present invention; and 
     FIG. 3 is a flow chart illustrating another aspect of the operation of a particular embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a block diagram of the components for a document projector, generally designated  10  according to the present invention is shown. The digital projector  10  includes a feed through scanner  12  and a digital projector  14 , which are connected to a microprocessor  16  that provides control and digital image processing support for the document projector  10 . The document projector  10  also includes an image memory  18  (typically DRAM solid state memory), control panel  20  and a power supply  22 . 
     The feed through scanner  12  contains a document transport including a set of drive rollers  24  that transport a document  26  at a controlled rate through the scanner by a drive motor  28 . The document  26  is driven past an illumination source including one or more scan lamps  30  which illuminate the document  26 . An image of the document is then captured by a linear sensor  32  such as a CCD or CMOS sensor, which produces a digital image of the document  26 . The feed through scanner  12  includes transparency scanning capability with transparency scan lamps  34  located opposite the linear sensor  32 . 
     Optionally, the scanner  12  includes a sheet sensor  36  and transparency detector  38  for detecting when a transparency has been loaded into the document projector  10 . Alternatively, the document projector  10  is provided with a reflection/transparency scanning mode switch. The transparency mode disables the reflection light source and employs a different set of look up tables to process the digital image in the microprocessor  16  prior to projection. 
     The output of the image sensor  32  is converted from an analog signal to a digital signal and is sent to the microprocessor  16 . The microprocessor  16  performs color corrections on the digital image and compresses the image so it will occupy less space in image memory  18 . The digital image is then stored in image memory  18 . 
     The microprocessor  16  controls the timing of the sequence of operation of the document projector  10 . The control panel  20  sends signals to the microprocessor  16  from the user. Finally the power supply  22  converts AC power to the required voltages for various components of the document projector  10 . 
     The digital projector  14  includes a high intensity lamp  40  for projecting the digital image. Light from this lamp  40  is focused with projection optics  42  so that it projects through a Spatial Light Modulator  44 , such as a liquid crystal (LCD) modulator, or a digital micro-mirror device (DMD), where the light is selectively attenuated or reflected by color and location so as to represent the document image. The Spatial Light Modulator  44  is controlled by signals generated from the microprocessor  16 . The light exiting the Spatial Light Modulator  44  is then focused by projection optics  42  so as to project the image onto a screen (not shown). 
     FIG. 2 is a flow chart for the operation of the document projector  10  according to the present invention, where a single or multi page document is prescanned into the image memory for display at a later time. 
     For the pre-scanning and displaying mode of operation a user would first turn the unit on  46 . The operator would then insert  48  the first page of the document to be scanned into the scanning paper path. The user would then push  50  the scan button on the control panel. Alternatively, the signal from the document sensor  36  can be used to initiate the scan. This commands the control microprocessor to turn on the scanner unit drive motor which transports the page to the scan lamps and linear sensor  52 . The control microprocessor turns on  54  the scan lamps  30  and signals the linear image sensor to collect image information  56 . The image information is processed  58  by the microprocessor  16  to adjust the color correction and to compress the digital image. The compressed image is then stored  60  in the image memory  18 . This sequence is repeated  62  until all pages of the document are scanned. 
     To display the images the user presses  64  a “Next” play image button  66  on the control panel. This commands the microprocessor to turn on  68  the display unit lamp  40 . A signal is sent to the microprocessor to retrieve  70  the first image from the image memory. This image is processed and an image signal is sent  72  to the Spatial Light Modulators  44  of the display unit  14 , where the light is selectively attenuated by color and location so as to represent the document image. The light exiting the Spatial Light Modulators is then focused by projection optics  42  so as to display  74  the image onto a screen. A previous play image button  76  may be actuated to command the microprocessor  16  to display the previous image  77 . This is repeated  78  until all the document images are displayed. 
     FIG. 3 is a flow chart for the operation of a document projector  10  according to the present invention where a presentation is being provided to the microprocessor  16  from a connected personal computer (not shown). During a presentation of this type the user may want to display additional or new documents that are not resident in the computer. This flow chart shows how a document  26  can be scanned and displayed in the middle of a presentation from a connected personal computer. 
     To add a new document to a presentation which is being provided to the microprocessor  16  from a personal computer, the user turns on the unit  46  and connects the personal computer  80  through the computer image input  84 . Digital images are then provided to the microprocessor  16  from the personal computer. Digital images from the personal computer  82  are then displayed. When a new document is to be added to the presentation the user inserts  48  the first page of the document  26  to be scanned into the scanning paper path. The user would then push  50  the scan button on the control panel  20 . Alternatively, the signal from the document sensor  36  can be used to initiate the scan. This commands the microprocessor to turn on the scanner unit feed motor, which transports the document to the scan lamps and linear image sensor  52 . The control microprocessor turns on  54  the scan lamps  30  and signals the linear image sensor to collect image information  56 . The image information is processed  58  by the microprocessor  16  to adjust the color correction and to compress the digital image. The compressed image is then stored  60  in the image memory  18 . This sequence is repeated  62  until all pages of the document are scanned. 
     To display the images the user presses  64  a “Next” play image button  66  on the control panel. This commands the microprocessor to turn on  68  the display unit lamp  40 . A signal is sent to the image microprocessor to retrieve  70  the first image from the image memory. This image is processed and an image signal is sent  72  to the Spatial Light Modulators  44  of the display unit  14 , where the light is selectively attenuated by color and location so as to represent the document image. The light exiting the spatial light modulators is then focused by projection optics  42  so as to display  74  the image onto a screen. A previous play image button  76  may be actuated to command the microprocessor  16  to display the previous image  76 . This is repeated  78  until all the document images are displayed. Digital images from the personal computer  82  are then displayed. 
     The user can switch from digital images from the personal computer  82  to scanned digital images by pressing  64  the next play image button on the control panel  20  of the document projector  10 . The user can also switch from scanned digital images to digital images from the personal computer  82  by pressing the next image button on the personal computer. 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
     PARTS LIST 
       10  document projector 
       12  feed through scanner 
       14  digital projector 
       16  microprocessor 
       18  image memory 
       20  control panel 
       22  power supply 
       24  drive rollers 
       26  document 
       28  drive motor 
       30  scan lamps 
       32  linear sensor 
       34  transparency scan lamps 
       36  sheet sensor 
       38  transparency detector 
       40  lamp 
       42  projection optics 
       44  Spatial Light Modulator 
       46  turn on unit 
       48  insert page to be scanned 
       50  push the scan button 
       52  microprocessor turns on drive motor 
       54  microprocessor turns on scan lamps 
       56  linear image sensor collects image information 
       58  image information is processed by the microprocessor 
       60  image is then stored in the image memory 
       62  sequence is repeated until all pages of the document are scanned 
       64  user presses a next play image button 
       66  next image play button 
       68  microprocessor turns on the display unit lamp 
       70  microprocessor retrieves image from the image memory 
       72  image is processed and an image signal is sent to the Spatial Light Modulators 
       74  display the image 
       76  previous play image button 
       78  display the previous image 
       80  repeated until all the document images are displayed 
       80  connect the personal computer through the computer image input 
       82  digital images from the personal computer are displayed