Patent Publication Number: US-2007097024-A1

Title: Multi-channel imaging system

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS  
      This application claims priority from Korean Patent Application No. 10-2005-0096501, filed on Oct. 13, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      Apparatuses consistent with the present invention relate to a multi-channel imaging system, and more particularly, to a multi-channel imaging system that allows multiple viewers to simultaneously see different images in a full-screen mode on a single screen.  
      2. Description of the Related Art  
      Currently, televisions (TVs) or monitors employing a multi-channel, imaging system that can display a plurality of different images on a single screen are being widely used. Typically, a multi-channel imaging system can be implemented using a Picture in Picture (PIP) feature whereby a small sub-screen is displayed in a corner of a main screen as shown in  FIG. 1A  or using a double screen function whereby two images of the same size are displayed on the left and right sides of a screen as shown in  FIG. 1B .  
      However, a multi-channel imaging system realized using the methods as shown in  FIGS. 1A and 1B  cannot display each image in a full-screen. Another drawback is that when a user intends to view only the desired image, a plurality of other images displayed are likely to irritate the user&#39;s eyes. In the PIP mode shown in  FIG. 1A , a portion of the main screen is hidden by the sub-screen. In the double screen mode shown in  FIG. 1B , an image displayed on the screen is distorted, i.e., vertically lengthened because the horizontal dimension of the image is reduced compared to an original image size.  
      Thus, to overcome the drawbacks, a multi-channel imaging system that allows multiple users to view their desired images as a full-screen image on a single screen without being irritated due to the presence of other images has been proposed.  
       FIG. 2  shows a related art multi-channel imaging system proposed in Japanese Patent Publication No. 62-65580. Referring to  FIG. 2 , in the conventional multi-channel imaging system, multiple users  11  through  13  wear glasses  14  through  16 , respectively, to selectively view one of images A, B, and C sequentially displayed on a display device  10  at high speed. The glasses  14  through  16  may have a liquid crystal shutter. The liquid crystal shutter is open when the desired image is displayed and closed for when other images are displayed. Thus, a user can selectively view one of images A, B, and C by allowing the shutter to open and close in synchronization with the display of the appropriate image on the display device  10 . However, in the conventional multi-channel imaging system, the image scanning speed of the display device  10  and the liquid crystal shutter speed of the glasses  14  through  16  must be sufficiently high to prevent flickering. Also, the liquid crystal shutters of the glasses  14  through  16  must be very precisely synchronized with the display device  10 .  
       FIG. 3  shows a related art multi-channel imaging system disclosed in Japanese Patent Publication No. 62-91926. Referring to  FIG. 3 , in the multi-channel imaging system, two images from projectors  20  and  20 ′ are transmitted through a polarization plate  22  or  22 ′ and projected onto a screen  23 . Multiple users wear one of two orthogonal polarizing glasses  24  and  24 ′ to view an image. In this case, because an image having a polarization orthogonal to that of polarizing glasses that a user wears occludes, the user is able to selectively view only an image having the same polarization as that of the polarizing glasses. However, the multi-channel imaging system of  FIG. 3  can apply only to a projection structure and requires an expensive polarization-preserving screen.  
     SUMMARY OF THE INVENTION  
      The present invention provides a multi-channel imaging system that enables multiple viewers to simultaneously view different images in full-screen mode on a single screen.  
      The present invention also provides a multi-channel imaging system that enables multiple viewers to simultaneously view different images in full-screen mode on a single screen without degradation in image resolution.  
      According to an aspect of the present invention, there is provided a multi-channel imaging system including: a mode selector which selects a general two-dimensional (2D) mode, a multi-channel 2D mode, or a three-dimensional (3D) mode; a source selector which provides an image of at least one channel selected by a user; a conversion unit which interlaces two images received from the source selector so that the two images alternate with each other when the multi-channel mode or the 3D mode is selected; a display which displays the alternating two images received from the conversion unit so that they have orthogonal polarizations; 3D polarizing glasses which provide a different image to the left and to the right eye when the 3D mode is selected; and a pair of multi-channel polarizing glasses each of which provides a user with only one of two images being displayed when the a multi-channel 2D mode is selected.  
      The display may include a liquid crystal display (LCD) panel which displays at least one image having specific polarization directions; and a multi-channel screen that is disposed in front of the LCD panel and includes a plurality of birefringence elements arranged at regular intervals which rotate the polarization direction of one of the two images being alternately displayed on the LCD panel by 90 degrees.  
      The birefringence element may include one a rotator which rotates incident light by 90 degrees or a retarder which delays the phase of incident light by λ/2.  
      The display may include: a non-polarizing display panel which displays at least one image having no polarization; and a multi-channel screen that is disposed in front of the display panel and includes first and second polarizing plates with orthogonal polarization directions arranged at regular intervals so that the two images being alternately displayed on the display panel have orthogonal polarizations.  
      The display panel may be a Plasma Display Panel (PDP), a Field Emission Display (FED) panel, or a Cathode Ray Tube (CRT) panel. When the multi-channel 2D mode is selected, the source selector may provide two images, selected by the user among images independently provided by a plurality of image sources, to the conversion unit. The plurality of image sources may include at least one of a TV channel, a VCR, a PC, and a DVD player.  
      When the multi-channel 2D mode is selected, the conversion unit downscales the resolution of the two images provided by the source selector and interlaces the two images so that they alternate with each other.  
      Alternatively, when the multi-channel 2D mode is selected, the conversion unit may repeat a first step of time-dividing the two images provided by the source selector, interlacing the odd lines of a first image of the two images and the even lines of a second image of the two images so that they alternate with each other and providing the alternating images to the display and a second step of interlacing the odd lines of the second image and the even lines of the first image so that they alternate with each other and providing the alternating images to the display. The conversion unit makes a frame rate of an image provided on the display after the interlacing process twice that of a frame rate of the image provided by the source selector, thus enabling multiple users to simultaneously view two images in full size on a single screen without degradation of the image resolution.  
      When the 3D mode is selected, the source selector provides a left eye image and a right eye image to the conversion unit. The conversion unit downscales the resolution of the left eye image and the right eye image provided by the source selector and interlaces the left and right eye images so that they alternate with each other.  
      Alternatively, when the 3D mode is selected, the conversion unit may repeat a first step of time-dividing the left eye image and the right eye image provided by the source selector, interlacing the odd lines of the left eye image and the even lines of the right eye image so that they alternate with each other, and providing the alternating images to the display and a second step of interlacing the odd lines of the right eye image and the even lines of the left eye image so that they alternate with each other and providing the alternating images to the display. The conversion unit makes a frame rate of an image provided on the display after the interlacing process double a frame rate of the image provided by the source selector, thus enabling a user to view a 3D image without degradation in image resolution.  
      The 3D polarizing glasses include left and right orthogonal polarizing plates.  
      The pair of multi-channel polarizing glasses includes first polarizing glasses having first left and right polarizing plates with a first polarization and second polarizing glasses having second left and right polarizing plates with a second polarization orthogonal to the first polarization. In the multi-channel 2D mode, the first polarizing glasses provide only a first image of the two images being displayed on the display to the user and the second polarizing glasses provide only a second image of the two images being displayed to the user.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other aspects of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
       FIGS. 1A and 1B  schematically illustrate screens for realizing multiple channels in a conventional split-screen multi-channel imaging system;  
       FIGS. 2 and 3  schematically show conventional multi-channel imaging systems supporting multiple channels in a full-screen;  
       FIG. 4  is a block diagram of a multi-channel imaging system according to an exemplary embodiment of the present invention;  
       FIGS. 5A-5E  schematically show the constructions of a display in the multiple-channel imaging system of  FIG. 4 ;  
       FIG. 6  schematically shows the construction of a conversion unit in the multiple-channel imaging system of  FIG. 4 ;  
       FIG. 7  schematically shows a plurality of exemplary polarizing glasses used for imaging modes of a multi-channel imaging system;  
       FIGS. 8A and 8B  schematically shows operations of a multi-channel imaging system in each imaging mode according to an exemplary embodiment of the present invention; and  
       FIG. 9  schematically shows the operation of a time-division multi-channel imaging system according to an exemplary embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION  
      Referring to  FIG. 4 , a multi-channel imaging system  30  according to an exemplary embodiment of the present invention includes a mode selector  31  which selects operation modes; a source selector  32  which provides an image of at least one channel selected by a user; a conversion unit  33  which interlaces two images received from the source selector  32  so that they alternate with each other; and a display  34  which displays an image received from the conversion unit  33 . As shown in  FIG. 7 , the multi-channel imaging system  30  further includes a set of polarizing glasses including a three-dimensional (3D) polarizing glasses  43  and a pair of multi-channel polarizing glasses  41  and  42 . The mode selector  31  allows a user to select one of a general 2D mode, a multi-channel 2D mode, and a 3D mode so that the multi-channel imaging system  30  can operate in the selected mode. The source selector  32  allows a user to choose one or two images from image sources such as TV channel, VCR, PC, and DVD player according to an operation mode.  
      The multi-channel imaging system  30  operates on a principle similar to a stereoscopic image display system using polarizing glasses. In a typical stereoscopic image display system using polarizing glasses, left-eye image and right-eye image are interlaced so that the images alternate with each other and two interlaced images are displayed on a display so that the left-eye and right-eye images have orthogonal polarizations. The polarizing glasses having two orthogonal polarizing plates are used to present the separate left-eye and right-eye images to a user&#39;s left and right eyes.  
      Similarly, the display  34  of the multi-channel imaging system  30  displays images of two channels received from the source selector  32  so that they have orthogonal polarizations. For example, as shown in  FIG. 5A , the display  34  may alternately display images having vertical and horizontal polarizations in a longitudinal direction. As shown in  FIG. 5B , the display  34  may alternately display images having vertical and horizontal polarizations in a transverse direction. Referring to  FIG. 5C , the display  34  may alternately display images having vertical and horizontal polarizations in a square matrix. The conversion unit  33  interlaces two images received from the source selector  32  so that the two images alternate as shown in  FIGS. 5A and 5C . The display  34  displays the images received from the conversion unit  33  while assigning specific polarization direction to the images being displayed.  
      To achieve this function, the display  34  includes a display panel  35  displaying an image and a multi-channel screen  36  or  37  assigning polarization to an image being displayed. The display panel  35  may be any type of display panel such as an LCD panel, a PDP, a FED panel, or a CRT panel. The multi-channel screen  36  or  37  is located in front of the display panel  35  and includes two types of optical elements arranged in the same pattern as two images are interlaced by the conversion unit  33 . The two types of optical elements in the multi-channel screen  36  or  37  assign orthogonal polarizations to the two images.  
      For example, when the display  34  shown in  FIG. 5D  uses an LCD panel as the display panel  35 , an image being displayed on the LCD panel already has polarization of specific direction. In this case, by rotating the polarization direction of one of two images by 90° while allowing the other image to pass through, the two images with two orthogonal polarizations can be obtained. To achieve this purpose, the multi-channel screen  36  may include a plurality of birefringence elements  36   b  arranged at regular intervals rotating the polarization direction of one of two images being alternately displayed on the display panel  35  by 90 degrees and transmissive plates  36   a  that are disposed between adjacent birefringence elements  36   b  and transmit the other image. The birefringence elements  36   b  may be rotators rotating incident light by 90 degrees or retarders delaying the phase of incident light by λ/2.  
      On the other hand, when an image being displayed on a display panel  35  such as a PDP, FED, or CRT panel does not have polarization, polarization can be assigned to two images using two polarizing plates having orthogonal polarizations. That is, as shown in  FIG. 5E , the multi-channel screen  37  disposed in front of a non-polarizing display panel includes first and second polarizing plates  37   a  and  37   b.  having orthogonal polarization directions arranged at regular intervals.  
       FIG. 7  schematically shows a plurality of polarizing glasses used for imaging modes of a multi-channel imaging system. Referring to  FIG. 7 , two polarizing glasses  41  and  42  are a set of multi-channel polarizing glasses being used for a multi-channel 2D mode. For example, the first polarizing glasses  41  has first left and right polarizing plates transmitting only horizontal polarization components while the second polarizing glasses  42  has second left and right polarizing plates transmitting only vertical polarization components. Thus, a user who wears the first polarizing glasses  41  can view only an image formed by the horizontal polarization component while another user who wears the second polarizing glasses  42  can view only an image formed by the vertical polarization component. Thus, the multi-channel imaging system enables multiple users to view different images using a single display system. Third polarizing glasses  43  are 3D polarizing glasses for viewing a 3D image in a 3D mode and have left and right orthogonal polarizing plates. Thus, a user&#39;s left eye can see only a left eye image being displayed on the display  34  in a 3D mode and the right eye can see only a right eye image while wearing the third polarizing glasses  43 , thus enabling a stereoscopic image.  
      The operation of the multi-channel imaging system  30  will now be described in more detail.  
      First, a user selects one of a general 2D mode, a multi-channel 2D mode, and a 3D mode through the mode selector  31 . When the user selects the general 2D mode, the user selects one channel through the source selector  32  and observes an image being displayed on the display  34  without polarizing glasses. In this case, signal processing through the conversion unit  33  is not required.  
      When two or more users intend to view images from different channels on the same screen, a multi-channel 2D mode is selected. Then, each user selects a desired image from two channels or sources through the source selector  32 . The user can select one of various image sources such as TV, PC, DVD player, and VCR according to desired service type. In particular, different channels on TV can be considered as different sources. Two image signals selected by the source selector  32  are scaled according to the resolution of the display  34  by the conversion unit  33  and are then displayed on the display  34 .  
       FIG. 6  illustrates the operation of the conversion unit  33 . Referring to  FIG. 6 , assuming that the display  34  has an N×M resolution, signals input to the conversion unit from different channels are downscaled to a N/2×M resolution. Then, downscaled versions of images from two channels are interlaced by a multiplexer (Mux) so that the images alternate and are eventually displayed at the original resolution ( N×M) of the display  34 . For convenience of explanation,  FIG. 6  shows an example in which the odd and even lines of an image are polarization-encoded separately by the display  34  as shown in  FIG. 5A . However, the conversion unit  33  may interlace two images as shown in  FIGS. 5A-5C .  
      As a result, as shown in  FIG. 8B , an image from channel  2  (CH 2 ) may be displayed with vertical polarization on the odd lines of the display  34  while an image from channel  1  (CH 1 ) may be displayed with horizontal polarization on the even lines. Thus, a user who desires to view the image from CH 1  wears the first polarizing glasses  41  and another user who desires to see the image from CH 2  wears the second polarizing glasses  42 . The user wearing the first polarizing glasses  41 , which block the image from CH 2  having vertical polarization and allows the image from CH 1  having horizontal polarization to pass through, can view only the image from CH 1  without being irritated. The user wearing the second polarizing glasses  42  can see the image from CH 2  without being annoyed due to the presence of an image from another channel.  
      A user who desires to view a stereoscopic image selects a 3D mode. The source selector  32  provides left eye image and a right eye image from a 3D channel selected by the user to the conversion unit  33 . As in the multi-channel 2D mode, the conversion unit  33  downscales the resolutions of the left eye image and the right eye image received from the source selector  32  and interlaces the two images so that they alternate with each other before providing the alternating images to the display  34 . In this case, the user wears the 3D polarizing glasses  43  to see the two images being displayed on the display  34  as shown in  FIG. 8A , thereby perceiving a stereoscopic image.  
      As described above, the multi-channel imaging system  30  allows a user to select one of a general 2D screen, a multi-channel 2D screen, and a 3D screen and to view the desired image.  
      Images in the multi-channel 2D mode and the 3D screen have half the resolution of an image in the general 2D mode. Thus, to prevent degradation of resolution, an image can be displayed in a time-sharing manner as shown in  FIG. 9 . Referring to  FIG. 9 , at time  1 , the conversion unit  33  interlaces the odd lines of an image from CH 1  and the even lines of an image from CH 2  so that they alternate with each other and provides the interlaced images to the display  34 . At time  2 , the conversion unit  33  interlaces the odd lines of the image from CH 2  and the even lines of the image from CH 1  so that they alternate with each other and provides the interlaced images to the display  34 .  
      When the period of time  1  or time  2  is half the time when two images are displayed on a screen in a general 2D mode, the original resolution of the image can be maintained. That is, the remaining portion of an image not displayed at time  1  due to the presence of an image from a different channel can be displayed at time  2  by repeatedly changing the display position of images from the two channels CH 1  and CH 2  over a short period. Thus, the entire image can be displayed without loss, thus preventing degradation in resolution.  
      Further, the display  34  repeatedly rotates the polarization direction of an image being displayed by 90 degrees or allows the image to pass through in synchronization with the speed of time-sharing display so that the images from CH 1  and CH 2  retain vertical and horizontal polarizations, respectively. To achieve this function, a polarization switch (not shown) may be disposed in front of the multi-channel screen  36  or  37  shown in  FIG. 5D  or  5 E. The polarization switch being turned off allows light to pass through while the polarization switch being turned on rotates the polarization direction of light by 90 degrees. Thus, when the polarization switch is turned on or off repeatedly in synchronization with the speed of time-sharing display of an image, each image can always maintain the same polarization direction.  
      Like in the multi-channel 2D mode, in the 3D mode, the conversion unit  33  interlaces the odd lines of a left eye image and the even lines of a right eye image so that they alternate with each other and provides the interlaced images to the display  34 . The conversion unit  33  also interlaces the odd lines of the right eye image and the even lines of the left eye image so that they alternate with each other and provides the interlaced images. The conversion unit  33  repeats the above processes. A polarization switch is turned on or off repeatedly in synchronization with the alternating display of two images, thereby allowing a user to view a stereoscopic image without degradation in resolution.  
      While  FIG. 9  shows the time-sharing display method applied to a case in which the display  34  separately polarization-encodes the even and odd lines of an image, the same method can also be applied to cases in which images are interlaced as shown in  FIG. 5B  or  5 C.  
      While in the above description an image being displayed on the display  34  has a linear polarization, the principle of the present invention can apply when an image has a circular polarization.  
      As described above, the multi-channel imaging system according to an exemplary embodiment of the present invention allows multiple viewers to simultaneously view images from different channels in full size on a single screen using a simple method compared to a conventional imaging system. Furthermore, the multi-channel imaging system uses a time-sharing display method to allow multiple users to simultaneously see images from different channels in full size on a single screen without degradation in image resolution.  
      While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.