Abstract:
The present invention relates to a stereoscopic image display and to a driving method thereof, and more particularly, to a stereoscopic image display capable of preventing the occurrence of crosstalk, and to a driving method thereof. The method for driving the stereoscopic image display of the present invention, comprises the steps of: generating a double-speed image signal containing a left eye image signal and a right eye image signal having a period shorter than one frame of input frame units, and a black image signal with no scene signal for image signals input by said frame units which separately contain a left eye image and a right eye image; and outputting a driving signal for driving a display panel in accordance with the double-speed image signal.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a 3-dimensional image display and a driving method thereof, and more particularly, to a 3-dimensional image display which can prevent the occurrence of crosstalk, and a driving method thereof. 
         [0003]    2. Discussion of the Related Art 
         [0004]    With recent advances in digital display technology, new displays have been introduced which are capable of displaying realistic, 3-dimensional (3D) images in addition to displaying high-definition images on a large screen, thereby satisfying consumer demand. 
         [0005]    Large-screen 3D image displays developed up to now include a polarization type and a parallax barrier type. Especially, the polarization type does not deteriorate resolution of images unlike the parallax barrier type. 
         [0006]    The polarization type 3D image display includes an active shutter glasses type in which an active shutter is applied to glasses and a passive glasses type using polarized glasses. 
         [0007]    The active shutter type generates parallax using a liquid crystal shutter in glasses over time with respect to a left-eye image and a right-eye image. The passive glasses type generates different polarized signals over time by installing a liquid crystal element in a display and displays alternately left-eye and right-eye images using polarized glasses. 
         [0008]    A device for displaying left-eye and right-eye images over time includes a micro display (LCD, LCoS, DLP, etc.) and a direct view display (CRT, LCD, PDP, etc.). 
       SUMMARY OF THE INVENTION 
       [0009]    Accordingly, the present invention is directed to a 3D image display which can reduce mutual interference between a left-eye image and a right-eye image by a double-speed image signal having a black image signal interval upon generating a 3D image signal, and a driving method thereof. 
         [0010]    Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned through practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
         [0011]    To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method for driving a three-dimensional image display includes generating a double-speed image signal including a black image signal with no screen signals and including left-eye and right-eye image signals having a shorter period than one frame, with respect to an input image signal in units of frames, wherein the input image signal separately contains a left-eye image and a right-eye image, and generating a driving signal for driving a display panel by the double-speed image signal. 
         [0012]    In another aspect of the present invention, a three-dimensional image display includes a driving signal processor for generating a double-speed image signal including a black image signal with no screen signals and including left-eye and right-eye image signals having a period shorter than one frame, with respect to an input image signal in units of frames, wherein the input image signal separately contains a left-eye image and a right-eye image, and a display panel driven by a driving signal generated from the driving signal processor. 
         [0013]    In a further aspect of the present invention, a three-dimensional image display includes a driving signal processor for generating a double-speed image signal and an inverted driving signal with respect to an input image signal, generating a double-speed image signal by doubling the input image signal to the same signal upon generating a two-dimensional image signal, and generating a double-speed image signal including a black image signal between a left-eye image signal and a right-eye image signal upon generating a three-dimensional image signal. 
         [0014]    In still another aspect of the present invention, a three-dimensional image display includes a light source, a Polarization Beam Splitter (PBS) for controlling a path of light emitted from the light source, a display panel having a black image signal between a left-eye image signal and a right-eye image signal to achieve a three-dimensional image, wherein light passing through the PBS is incident on the display panel and wherein the display panel is driven by a driving signal having an inverted signal at a period of sum of the left-eye image signal and the right-eye image signal, and a projection lens for projecting an image achieved by the display panel. 
         [0015]    It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
           [0017]      FIG. 1  is a block diagram of a display; 
           [0018]      FIGS. 2   a  to  2   e  illustrate an example of driving signal waveforms of a display panel; 
           [0019]      FIGS. 3   a  to  3   e  illustrate an example of driving signal waveforms of a 3D image; 
           [0020]      FIG. 4  is a graph illustrating liquid crystal response signals; 
           [0021]      FIG. 5  is a graph illustrating the occurrence of crosstalk caused by the signals shown in  FIG. 4 ; 
           [0022]      FIGS. 6   a  to  6   f  illustrate another example of driving signal waveforms of a 3D image; 
           [0023]      FIG. 7  is a graph illustrating liquid crystal response signals; 
           [0024]      FIG. 8  is a graph illustrating the occurrence of crosstalk caused by the signals shown in  FIG. 7 ; 
           [0025]      FIG. 9  is a schematic diagram illustrating an exemplary embodiment of a 3D display; and 
           [0026]      FIG. 10  is a diagram illustrating implementation of 3D image. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
         [0028]    As illustrated in  FIG. 1 , a driving signal processor of a display receives an input signal a 1  which separately includes a left-eye image and a right-eye image to achieve a 3D image, or an input image signal which is input after signal processing is performed in the display. 
         [0029]    Upon receiving the input image signal a 1 , the driving signal processor  10  generates a double-speed image signal b 1  and an inverted driving signal b 2 . The double-speed image signal b 1  is obtained by doubling the same frame so that the input image signal a 1  can be driven at double speed for the purpose of frame inversion to avoid an after image of a display panel  30 . The inverted driving signal b 2  serves to determine inversion polarity for frame inversion. Hereinafter, an LCD panel is described as an example of the display panel  30 . 
         [0030]    The double-speed image signal b 1  and the inverted driving signal b 2 , which are digital signals generated from the driving signal processor  10 , are input to a Digital/Analog (D/A) converter  20 . The D/A converter  20  then generates a liquid crystal driving signal c 1 , which is an analog signal, to drive the display panel  30 . 
         [0031]    The LCD panel  30  includes an illuminator  31  (usually, referred to as a backlight) for supplying light to the LCD panel  30 . The driving signal processor  10  generates an illumination control signal d 1  which can control the timing at which light generated from the illuminator  31  is irradiated to the LCD panel  30 . 
         [0032]    Waveforms of output signals generated through the above process are illustrated in  FIGS. 2   a  to  2   e . Namely, if an input image signal a 1  is input to the driving signal processor  10  in units of frames, the driving signal processor  10  generates a double-speed image signal b 1 , a period of which is half a period of the input image signal a 1  in one frame, and generates an inverted driving signal b 2  for inverting the same signals within one frame. 
         [0033]    In the input image signal a 1 , reference symbols D 1 , D 2 , . . . denote images of respective frames and the respective frame images are comprised of the double-speed image signal b 1  having the same double-speed signals D 1 +, D 2 +, . . . . 
         [0034]    A liquid crystal driving signal c 1  is obtained by multiplying the double-speed image signal b 1  by the inverted driving signal b 2 . The liquid crystal driving signal c 1  is comprised of image signals D 1 +, D 1 −, D 2 +, . . . , each being double the rate of the input image signal and having opposite polarities. 
         [0035]    Thus, the liquid crystal driving signal c 1  may solve an after image problem in the LCD panel by driving the display using image signals having opposite polarities. 
         [0036]    In this case, an illumination control signal d 1  of an always high state is generated and the illuminator  31  may remain on at all times. 
         [0037]    Meanwhile, a 3D image has an input image signal a 1  comprised of left-eye images (L 1 , L 2 , etc.) and right-eye images (R 1 , R 2 , etc.) in units of frames. The 3D image generates output waveforms as illustrated in  FIGS. 3   a  to  3   e  through the above-described process. 
         [0038]    Specifically, the left-eye images (L 1 , L 2 , etc.) alternate with the right-eye images (R 1 , R 2 , etc.) as shown in  FIG. 3   a . The alternating image signals are generated as a double-speed image signal b 1  including the same double-speed signals (L 1 +, L 1 +, R 1 +, R 1 +, etc.) as shown in  FIG. 3   b . The double-speed image signal b 1  is generated as a liquid crystal driving signal c 1  as shown in  FIG. 3   d  by multiplication with an inverted driving signal b 2  shown in  FIG. 3   c . The liquid crystal driving signal c 1  is comprised of inverted image signals (L 1 +, L 1 −, R 1 +, R 1 −, etc.). 
         [0039]    In this case, an illumination control signal d 1  is always in a high state so that the illuminator  31  may always remain an on state. 
         [0040]      FIG. 4  shows times written into the first pixel and the last pixel of a display panel and liquid crystal response signals of the two pixels in a full High Definition (HD) (1080 pixels) LCD when a frame rate of the 3D input image signal a 1  is 60 Hz, and a frame rate of each of a left-eye image and a right-eye image is 120 Hz. 
         [0041]    Hereinafter, a display characteristic is described in the case of achieving a 3D image in a display panel having such liquid crystal response signals. To this end, image signals of only the first pixel and the last pixel of the display panel are shown for convenience because the display characteristic is sufficiently predicted when the 3D image is displayed in the display panel only by the images of the first and last pixels. 
         [0042]    Referring to  FIG. 4 , solid lines denote liquid crystal brightness signals by the left-eye images (L 1 , L 2 , etc.) in the first pixel of the display panel, and dotted lines denote liquid crystal brightness signals by the left-eye images (L 1 , L 2 , etc.) in the last pixel. 
         [0043]    In addition, dash-dotted lines denote liquid crystal brightness signals by the right-eye images (R 1 , R 2 , etc.) in the first pixel of the display panel and dash-dot-dotted lines denote liquid crystal brightness signals by the right-eye images (R 1 , R 2 , etc.) in the last pixel. 
         [0044]    More specifically, L 1 F denotes a liquid crystal brightness signal in the first pixel of the display panel by the signal L 1 , and L 1 N denotes a liquid crystal brightness signal in the last pixel of the display panel by the signal L 1 . 
         [0045]    Similarly, R 1 F denotes a liquid crystal brightness signal in the first pixel of the display panel by the signal R 1 , and R 1 N denotes a liquid crystal brightness signal in the last pixel of the display panel by the signal R 1 . 
         [0046]    As shown, the signal L 1 N is started after a liquid crystal signal write time since the signal L 1 F has been started. A field period of the signal L 1  or R 1  for displaying the left-eye or right-eye image may be twice the liquid crystal signal write time. 
         [0047]    In terms of LCD properties, a response time is needed until full brightness is realized when a liquid crystal signal is enabled and the response time is also needed for liquid crystal to fully darken when the liquid crystal signal is disabled. 
         [0048]    Accordingly, as shown in  FIG. 5 , when a 3D image is achieved in an LCD, crosstalk indicating that a left-eye image interval and a right-eye image interval interfere with each other may be generated. 
         [0049]    In  FIG. 5 , reference symbol RnF denotes a right-eye image signal of the first pixel of a previous screen invading on a left-eye image interval. RnN denotes a right-eye image signal of the last pixel of a previous screen invading on a left-eye image interval. That is, crosstalk that the right-eye image signals RnF and RnN are present in the left-eye image interval may occur. A left-eye image signal area with no crosstalk in the left-eye image interval occupies only a part indicated by ‘L’. 
         [0050]    Similarly, reference symbol L 1 F denotes a left-eye image signal of the first pixel, which has been enabled in the left-eye image interval, invading on a right-eye image interval by a disabled signal. L 1 N denotes a left-eye image signal of the last pixel invading on the right-eye image interval. A right-eye image signal area with no crosstalk in the right-eye image interval is indicated by ‘R’. 
         [0051]    As described above, due to the liquid crystal response time and the time for writing an image signal into the display, the right-eye image signal may invade on the left-eye image interval and the left-eye image signal may invade on a right-eye image interval. When realizing a 3D image using a left-eye and right-eye time difference in an LCD, considerable crosstalk may be generated due to the liquid crystal signal write time as well as due to the response speed of liquid crystal. 
         [0052]    To improve such a phenomenon, it is favorable to use the driving signals shown in  FIGS. 2   a  to  2   e  when achieving a 2D image signal by an LCD, and to use the following driving signals when achieving a 3D image signal by the LCD. 
         [0053]    That is, left-eye image signals (L 1 , L 2 , etc.) and right-eye image signals (R 1 , R 2 , etc.) are alternately located in an input image signal a 1  as shown in  FIG. 6   a . The alternating signals are generated as a double-speed image signal b 1  including a black image signal having no screen signal in each period. 
         [0054]    The period of the double-speed image signal b 1  may be ½ the period of the input image signal a 1 . That is, the speed of the double-speed image signal b 1  may be twice the speed of the input image signal a 1 . However, the double-speed image signal b 1  may be a signal of 3 times, 1.5 times, etc. the input image signal a 1 . 
         [0055]    As described above, the double-speed image signal b 1  includes the black image signal in each period. Although, in  FIG. 6   b , the image signal has the same duration as the black image signal, they may have different durations. For example, the length of the black image signal may be longer or shorter than the length of the left-eye or right-eye image signal. 
         [0056]    Thus, an L 1  interval includes an L 1 + signal and a black signal, and an R 1  interval includes an R 1 + signal and a black signal. Similarly, an L 2  interval includes an L 2 + signal and a black signal, and an R 2  interval includes an R 2 + signal and a black signal. 
         [0057]    The driving signal processor  10  generates an inverted driving signal b 2  for frame inversion. The inverted driving signal b 2  has a period of sum of a pair of a left-eye image signal and a right-eye image signal constituting one image. 
         [0058]    That is, the period of the inverted driving signal b 2  is changed after the L 1 + signal and R 1 + signal. 
         [0059]    Accordingly, a panel driving signal c 1  includes an L 1 + signal, a black signal, an R 1 + signal and a black signal of one period. From an L 2 − signal, inverted signals are generated during the same length of one period. Again, normal signals (non-inverted signals) are generated after one period. 
         [0060]    In the driving signal c 1 , an interval {circle around (a)} denotes an active interval during which the driving signal is written into liquid crystal, and an interval {circle around (b)} denotes a dummy interval during which writing is not performed. 
         [0061]    As shown in  FIG. 6   e , an illumination control signal d is always in a high state so that the illuminator  31  may remain on state at all times. 
         [0062]    However, in the above case, the same function may be performed by turning off the illuminator  31  in a black image signal interval. 
         [0063]    That is, illumination may be turned off while the black signal shown in  FIG. 6   d  is generated. Meanwhile, even when the same double-speed signal is generated without generating the black signal as shown in  FIG. 3   d , the occurrence of crosstalk may be suppressed by turning off the illumination while at least one double-speed signal is generated. 
         [0064]    Namely, as shown in  FIG. 6   f , even when the same double-speed signal is generated without generating the black signal, the occurrence of crosstalk may be suppressed by turning off illumination by the illuminator  31  in an interval during which a subsequent double-speed signal is generated. 
         [0065]    Thus, at a prescribed part of the double-speed image signal, for example, at a part where a subsequent double-speed signal is generated, the illumination may be turned off. In this case, in an illumination off interval, the black signal may be generated or the double-speed signal may be generated. 
         [0066]      FIG. 7  shows input times of signals written into the first pixel and the last pixel of a display panel in an LCD and liquid crystal response signals of the two pixels. 
         [0067]    In  FIG. 7 , L 1 F denotes a liquid crystal brightness signal of the first pixel by the signal L 1 , and L 1 N denotes a liquid crystal brightness signal of the last pixel by the signal L 1 . Similarly, R 1 F denotes a liquid crystal brightness signal of the first pixel by the signal R 1 , and R 1 N denotes a liquid crystal brightness signal of the last pixel by the signal R 1 . 
         [0068]    It can be seen in  FIG. 7  that an interval between the liquid crystal brightness signals becomes wider. Accordingly, as shown in  FIG. 8 , crosstalk due to a liquid crystal signal write time is eliminated and only crosstalk due to a liquid crystal response speed remains, thereby remarkably reducing an area where crosstalk between the left-eye image and right-eye image occurs. 
         [0069]    In  FIG. 8 , a part indicted by ‘L’ denotes a left-eye image signal area having no crosstalk in a left-eye image interval, and a part indicated by ‘R’ denotes a right-eye image signal area having no crosstalk in a right-eye image interval. As shown, an area where crosstalk occurs is remarkably reduced. 
         [0070]    As an exemplary embodiment of a 3D image display realized by the above-described method, a liquid crystal projection display (an LCD, LCoS, etc.) is shown in  FIG. 9 . 
         [0071]    In the projection display which can achieve a 3D image, light emitted from a light source  40  is incident on a Polarization Beam Splitter (PBS)  60  by an illumination lens group  50 . The light which is incident on the PBS  60  forms an image by a display panel  30  which is driven by an output driving signal c 1  generated through a driving signal processor  10  and the D/A converter  20 , and is projected onto a screen  90  through a projection lens  80 . 
         [0072]    The output driving signal c 1  drives the display panel  30  through the following process. 
         [0073]    First, the driving signal processor  10  receives an input signal a 1  which separately includes a left-eye image and a right-eye image to achieve a 3D image, or an input image signal which is input after signal processing is performed in the display. 
         [0074]    The driving signal processor  10  generates a double-speed image signal b 1  by doubling the same frame of the input image signal a 1  of the display panel  30 . A black image signal is located between each left-eye image and each right-eye image constituting one scene. 
         [0075]    The driving signal processor  10  also generates an inverted driving signal b 2  which serves to determine inversion polarity and has a period of sum of the left-eye image and the right-eye image. 
         [0076]    The double-speed image signal b 1  and the inverted driving signal b 2 , which are digital signals generated from the driving signal processor  10 , are input to the D/A converter  20 . The D/A converter  20  then generates a liquid crystal driving signal c 1 , which is an analog signal, to drive the display panel  30 . 
         [0077]    The polarization conversion cell  70  polarizes the left-eye image and right-eye image generated from the display panel  30  so as to achieve different polarized states. A liquid crystal panel may be used as the polarization conversion cell  70 . 
         [0078]    Namely, as shown in  FIG. 10 , the left-eye image and the right-eye image generated from the display panel  30  have different polarized states by the polarization conversion cell  70  and viewers can view a 3D image through polarized glasses  100  including a left-eye glass L and a right-eye glass R corresponding to the two different polarized states. 
         [0079]    Accordingly, the left-eye image and the right-eye image generated from the display panel  30  can be independently seen through the left-eye glass L and the right-eye glass R of the polarized glasses  100 , thereby producing a stereoscopic image. 
         [0080]    Meanwhile, upon generating the double-speed image signal and the inverted driving signal with respect to the input image signal, the display may generate different double-speed image signals and the inverted driving signal when generating a 2D image signal and when generating a 3D image signal. 
         [0081]    Namely, the driving signal processor  10  may be controlled to generate a double-speed image signal by doubling the input image signal to the same signal when generating the 2D image signal, and to generate a double-speed image signal including a black image signal between a left-eye image signal and a right-eye image signal when generating the 3D image signal. 
         [0082]    Meanwhile, when the display panel  30  receives light generated from an illuminator  31 , the illuminator  31  may turn off illumination in an interval during which the black image signal is generated and a normal double-speed image signal may be generated instead of the black image signal in this interval. 
         [0083]    In this case, it is favorable for the driving signal processor  10  to generate an inverted image signal having a period of sum of the left-eye image signal and the right-eye image signal upon generating the 3D image signal. 
         [0084]    An LCD panel may be used as the display panel  30 , and the display panel  30  is applicable to all devices using LCD panels such as LCD TVs, monitors, etc. 
         [0085]    The present invention uses a liquid crystal driving signal including a black signal to reduce interference between a left-eye image and a right-eye image caused by slow write speed, thereby realizing a high-quality 3D image. 
         [0086]    It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.