JP2007047476A - Liquid crystal display device and driving method of liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of achieving both taking a countermeasure for reliability of frame inversion driving and displaying cinema images of high image quality. <P>SOLUTION: The liquid crystal display device performing frame inversion driving has a first mode of displaying the same image in frames of normal driving and frames of inversion driving and a second mode of displaying different images there, and the first or second mode is driven by switching in accordance with correlation of image signals of consecutive frames. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device.

  In particular, in a liquid crystal display device of a frame inversion (field inversion) driving method, a liquid crystal that can be displayed with high image quality even when a telecine conversion video signal generated by a conversion method such as a 2-3 pull-down method is input from a movie film. The present invention relates to a display device.

  Conventionally, there is JP-A-11-133376 as a liquid crystal display device that performs field inversion driving.

Conventionally, when displaying a 24Hz cinema image that has been converted to a 60Hz interlaced or progressive signal by telecine (2-3 pull-down), the same image is displayed continuously every two or three frames, and is discontinuous. There was a problem of moving.
Japanese Patent Laid-Open No. 11-133376

  However, in these liquid crystal display devices that perform frame inversion driving, it has not been possible to achieve both high-quality display of cinema images and reliability measures for liquid crystal display devices.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a display device capable of realizing both a reliability measure by frame inversion driving and high-quality display of cinema images in a liquid crystal display device.

  According to the present invention, in a liquid crystal display device that performs frame inversion driving, a first mode that displays the same image in a frame that performs normal rotation driving and a frame that performs inversion driving, and a second mode in which different images are displayed. A display device capable of realizing both high-quality display of cinema images and measures against burning and flicker by frame inversion driving by switching and driving according to the correlation of image signals of successive frames It became possible to provide.

  As described above, according to the present invention, it is possible to provide a display device capable of realizing both countermeasures such as burning and flicker by frame inversion driving and high-quality display of cinema images.

Example 1
FIG. 1 is a block diagram of a liquid crystal display device according to a first embodiment of the present invention.

  1 is a video signal input terminal, 2 is an A / D converter, 3 is an IP converter, 4 is a scaler, 5 is a frame double speed unit, 6 and 7 are memories, 8 is an inverting amplifier, and 9 is a non-inverting amplifier. Reference numeral 10 is a polarity switching circuit, 11 is a liquid crystal panel, 12 is an input timing generator, 13 is an output timing generator, 14 is a 2-3 pull-down detector, and 15 is a scene change detector.

  In the case of an image (film image) converted by the 2-3 pull-down method, a static field occurs every 5 fields. The 2-3 pull-down detection unit 14 detects this periodic pattern, identifies whether it is a film image (telecine conversion image) or a general image, and outputs detection information.

  FIG. 2 is a timing diagram for explaining a processing flow of an image signal when a normal NTSC signal of 60 Hz is input.

  2A is an NTSC signal input from the video signal input terminal 1, and FIG. 2B is an image output timing after IP conversion by the IP conversion unit 3, and FIG. ) Is a write timing to the memory 6, FIG. 2D is a write timing to the memory 7, FIG. 2E is a read timing from the memory 6, and FIG. ) Is a read timing from the memory 7, and FIG. 2G is an output of the polarity inverting circuit 10 and serves as a drive signal for the LCD 11.

  The NTSC signal input from the video signal input terminal 1 is converted into a digital signal by the A / D converter 2. FIG. 2A is a timing diagram showing an input NTSC signal. Interlaced image signals for each field such as AI, BI, CI, and DI are input at a 60 Hz period.

  The image signal A / D converted by the A / D converter 2 is input to the I / P converter 3 to convert the NTSC interlaced signal into a progressive signal. FIG. 2B shows a timing diagram of an image after IP conversion, and a 60 Hz progressive image is output using images of previous and subsequent frames by a motion adaptive IP conversion method or the like.

  The image signal after the IP conversion is input to the scaler 4, and resolution conversion processing such as enlargement / reduction is performed in accordance with the resolution of the input image displayed on the liquid crystal panel 11.

  The output image signal of the scaler 4 is input to the frame double speed unit 5, and the frame rate of the input image is converted to 2 times and output.

  FIGS. 2C and 2D are timing diagrams of images written to the memory 6 and the memory 7 by the double speed conversion unit 5. Data is alternately written into the memory 6 and the memory 7 for each frame.

  FIGS. 2E and 2F are diagrams showing timings for reading data from the memory 6 and the memory 7 by the double speed conversion unit 5. As shown in FIGS. 2E and 2F, the same image is output twice in succession by reading the data written in the memory 6 twice at twice the frame rate of writing. Next, the image data written in the memory 7 is continuously read from the memory 7 twice. As described above, the frame rate of the input image can be doubled by reading out from the memory at a double speed and reading out the image for two frames during the writing of one frame. .

  The image signal output from the frame double speed converter 5 is input to the inverting amplifier circuit 8 and the non-inverting amplifier circuit 9, amplified to a signal level suitable for driving the liquid crystal panel 11, and then input to the polarity switching circuit 10. As shown in FIG. 2 (g), the doubled images are alternately switched so as to be signals of positive polarity and opposite polarity, and are output. Here, the display without flicker can be obtained by alternately outputting positive and negative images.

  As described above, since the positive polarity and the opposite polarity image signals are the same, AC drive without charge bias can be performed, so that a highly reliable liquid crystal display device without burn-in can be obtained.

  In addition, by setting the display refresh rate to 120 Hz with respect to 60 Hz input, it is possible to prevent flicker from being visually detected even in frame inversion driving in which the drive polarity is inverted for each frame. Image quality display is now possible.

  Next, a processing method when an image converted into an NTSC signal by telecine conversion (2-3 pulldown) is input will be described.

  First, the case where the same process as the NTSC image described in FIG. 2 is performed on the telecine image will be described with reference to FIG.

  FIG. 3 is a timing chart for explaining a processing flow of an image signal when the same processing as that when the normal NTSC signal described in FIG. 2 is input is performed on a telecine image.

  Here, FIG. 3A is the timing of the original cinema image, FIG. 3B is the signal after telecine conversion input from the video signal input terminal 1, and FIG. FIG. 3D shows the timing of image output after IP conversion by the IP converter 3, FIG. 3D shows the timing of writing to the memory 6, and FIG. 3E shows the timing of writing to the memory 7. 3 (f) is the read timing from the memory 6, FIG. 3 (g) is the read timing from the memory 7, and FIG. 3 (h) is the output of the polarity inverting circuit 10 and the drive signal of the LCD 11 Become.

  FIG. 3A shows the timing of the original cinema video, which is composed of images of 24 frames per second, and the images are updated at 24 Hz.

  Here, when performing a telecine conversion of a cinema image to an NTSC 60 Hz signal, a method called 2-3 pull-down is used. As shown in FIG. 3B, two images of one cinema film are taken. By alternately repeating the case of repeating and the case of repeating three sheets, it is possible to convert from a frame rate of 24 Hz to a frame rate of 60 Hz. At this time, an interlace signal can be obtained by alternately reading the even lines and odd lines every 60 Hz frame.

  Subsequently, as in the case of FIG. 3, IP conversion, memory writing, and memory reading are performed, and an LCD drive signal is obtained by polarity inversion (FIG. 3 (h)).

  In this case, two or three images made from one cinema image are alternately subjected to frame double speed processing, so after frame double speed, as shown in FIG. 3 (h), Since the images continue alternately with four or six images, the motion may be felt unnatural in an image that continues to move continuously, causing deterioration in image quality.

  Next, a method for improving the motion of a telecine image and realizing high-quality display in a liquid crystal display device that performs frame double speed will be described with reference to FIG.

  FIG. 4 is a timing chart for explaining a processing flow for a telecine image when the 2-3 pulldown detection unit 14 detects a telecine image and detects a 2-3 pulldown phase. .

  4A shows the timing of the original cinema image, FIG. 4B shows the signal after telecine conversion input from the video signal input terminal 1, and FIG. FIG. 4D shows the timing of image output after IP conversion by the IP converter 3, FIG. 4D shows the timing of writing to the memory 6, and FIG. 4E shows the timing of writing to the memory 7. 4 (f) is the read timing from the memory 6, FIG. 4 (g) is the read timing from the memory 7, and FIG. 4 (h) is the output of the polarity inverting circuit 10 and the drive signal of the LCD 11 Become.

  From FIG. 4A to FIG. 4E, the same processing as in FIG. 3A to FIG. 3E is performed.

  If the 2-3 pull-down detection unit 14 determines that the image is a telecine image, the next time reading from the memory, as shown in FIG. Read continuously for minutes. Then, by reducing the image B read from the memory 6 by one frame, the image A and the image B are each continuous for five frames, and it is possible to obtain a high-quality video with smooth motion.

  Therefore, if it is determined that the signal has been pulled down 2-3, the signal is read from the memory 6 at the time of reading 401 of the fifth frame, and is read from the memory 7 at the time of reading 402 of the sixth frame. Output different images when driving. In this case, the images at the forward rotation 403 and the reverse rotation 404 are different, but in the case of a cinema image that is a moving image, the difference is small, and the effect of AC driving can be maintained.

  In this embodiment, the case where an NTSC interlace signal is input has been described. However, even when a progressive signal is input, only the IP conversion process is not performed, and the same process is possible. In this case, in FIG. 2, FIG. 3, FIG. 4, etc., the signal after IP conversion becomes a progressive input signal.

  In the present embodiment, the case of analog input has been described. Needless to say, the processing of the present invention can also be realized when a digital signal such as DVI is input.

  Further, in this embodiment, the description has been made assuming that two memories are used. However, the present invention is not limited to this, and the area may be divided and used by one memory.

(Example 2)
In this example, a liquid crystal display device with further improved reliability was developed.

  In the first embodiment, when a cinema image is displayed, the image is different between forward rotation and reverse drive at a rate of once every five times when the normal rotation and reverse drive are alternately performed.

  In the case of a cinema image, which is a moving image, the difference is small and the reliability is rarely deteriorated, but further improvement is necessary to further improve the reliability.

  For example, when the entire screen is switched from black display to white display, the unbalance between the positive polarity and the negative polarity is large. In this way, if the images are not continuous, if the same image is displayed during forward rotation and reverse rotation, the motion of the cinema image can be displayed with high image quality and the reliability can be improved. Is possible. In the present embodiment, the scene change detection unit detects non-continuous images, and switches the driving method from a normal telecine moving image.

  FIG. 5 is a timing chart for explaining a processing flow when the scene change detection unit 15 of FIG. 1 detects a scene change of a telecine image.

  Here, FIG. 5A shows the timing of the original cinema image, FIG. 5B shows the signal after telecine conversion input from the video signal input terminal 1, and FIG. FIG. 5D shows the timing of image output after IP conversion by the IP conversion unit 3, FIG. 5D shows the timing of writing to the memory 6, and FIG. 5E shows the timing of writing to the memory 7. 5 (f) is the read timing from the memory 6, FIG. 5 (g) is the read timing from the memory 7, and FIG. 5 (h) is the output of the polarity inverting circuit 10 and the drive signal of the LCD 11 Become.

  The operation will be described with reference to FIGS. 1 and 5.

  When the 2-3 pull-down detector 14 determines that the image is a cinema image, the scene change circuit 15 is used to compare the images corresponding to the continuous images of the original cinema image, thereby obtaining an image between frames. When it is determined that there is a difference in the image that exceeds a predetermined threshold, it is determined that the scene change has occurred.

  If the scene change is determined, the same image read from the memory 6 is output to the fifth frame 501 and the sixth frame 502 as shown in FIG.

  Then, as shown in the fifth frame 503 and the sixth frame 504 in FIG. 5H, the same image is displayed in the normal rotation and the reverse rotation.

  As described above, when the input cinema image is a normal moving image and when the correlation between successive images is small as in the case of a scene change, as shown in FIGS. By switching between displaying the same image on the eyes (403, 503) and the inverted sixth frame (404, 504), it is possible to further improve the reliability of AC drive. Become.

(Example 3)
In this embodiment, a liquid crystal display device that can further reduce power consumption and noise was developed.

  FIG. 6 is a timing diagram showing the flow of an image signal according to the present invention.

  Here, FIG. 6A shows the timing of the original cinema image, FIG. 6B shows the signal after telecine conversion inputted from the video signal input terminal 1, and FIG. FIG. 6D shows the timing of image output after IP conversion by the IP converter 3, FIG. 6D shows the timing of writing to the memory 6, and FIG. 6E shows the timing of writing to the memory 7. 6 (f) is a read timing from the memory 6, FIG. 6 (g) is a read timing from the memory 7, and FIG. 6 (h) is an output of the polarity inverting circuit 10 and the drive signal of the LCD 11. Become.

  6 (f ′) to 6 (h ′) show the timing at the time of the scene change, and FIG. 6 (f ′) shows the timing of reading from the memory 6 at the time of the scene change. (G ′) is a read timing from the memory 7 at the time of the scene change, and FIG. 6 (h ′) is an output of the polarity inverting circuit 10 at the time of the scene change and serves as a drive signal for the LCD 11.

  In the image after IP conversion in FIG. 6C, since two and three consecutive images continue, as shown in FIG. 6D, after the image 601 is written in the memory 6, the image 602 Writing is paused, and images are read from the memory 6 continuously for 5 frames, as shown in FIG.

  As shown in FIG. 6E, the memory 7 is controlled after the image 603 is written in the memory 7, the writing of the image 604 and the image 605 is suspended, and as shown in FIG. The image is read out continuously for 5 frames.

  In the polarity inversion switching circuit output, as shown in FIG. 6 (h), by providing a timing for displaying different images for normal rotation and inversion, continuous images every 5 frames are driven at frame inversion / frame double speed. It becomes possible.

  In this embodiment, the power consumption and noise during memory writing can be reduced to 1/5 of the first embodiment.

Example 4
In the present embodiment, a method of performing IP conversion at the same time when writing to the memory 6 and the memory 7 without using the IP conversion unit 3 will be described.

  Here, FIG. 7A shows the timing of the original cinema image, FIG. 7B shows the signal after telecine conversion input from the video signal input terminal 1, and FIG. FIG. 7E shows the timing of writing to the memory 6, FIG. 7E shows the timing of writing to the memory 7, FIG. 7F shows the timing of reading from the memory 6, and FIG. 7 (h) is an output of the polarity inverting circuit 10 and serves as a drive signal for the LCD 11. FIG.

  7 (f ′) to FIG. 6 (h ′) show the timing at the time of the scene change, and FIG. 7 (f ′) shows the timing of reading from the memory 6 at the time of the scene change. (G ′) is a read timing from the memory 7 at the time of the scene change, and FIG. 7 (h ′) is an output of the polarity inversion circuit 10 at the time of the scene change and serves as a drive signal for the LCD 11.

  In FIG. 7A, an image 701 is composed of even lines of a cinema image, and an image 702 is composed of odd lines of a cinema image.

  As shown in FIG. 7D, the image 701 is written in the even line storage area of the memory 6 and the image 702 is written in the odd line storage area of the memory 6.

  Then, as shown in FIG. 7 (f), by continuously reading the images stored in the memory 6, it is possible to simultaneously perform IP conversion and frame double speed.

  Similarly for the image “B”, as shown in FIG. 7E, the image 703 is written in the even line storage area of the memory 7 and the image 704 is written in the odd line storage area of the memory 7.

  Then, as shown in FIG. 7 (g), by continuously reading the images stored in the memory 7, it is possible to simultaneously perform IP conversion and frame double speed.

  As described above, according to the present invention, it is possible to simultaneously perform IP conversion and frame double speed in a frame double speed circuit without using an independent IP conversion circuit.

  In addition to high-quality display and reliability, it is possible to reduce costs and reduce the mounting area.

The block diagram by the Example of this invention. FIG. 3 is a timing chart for explaining processing in the case of NTSC input in the first embodiment. FIG. 3 is a timing chart for explaining processing in the case of telecine input in the first embodiment. FIG. 3 is a timing chart for explaining processing in the case of telecine input in the first embodiment. FIG. 10 is a timing chart for explaining processing in the case of a scene change in the second embodiment. FIG. 9 is a timing chart for explaining processing in the third embodiment. FIG. 10 is a timing chart for explaining processing in the fourth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Video signal input terminal 2 A / D converter 3 IP conversion part 4 Scaler 5 Frame double speed part 6 Memory 7 Memory 8 Inversion amplification circuit 9 Non-inversion amplification circuit 10 Polarity switching circuit 11 Liquid crystal panel 12 Input timing generation part 13 Output timing generation Section 14 2-3 Pulldown detection section 15 Scene change detection section

Claims (4)

  A liquid crystal display device that performs frame inversion driving includes a first mode that displays the same image in a frame that performs forward rotation driving and a frame that performs inversion driving, and a second mode in which different images are displayed. A liquid crystal display device that switches according to a correlation of image signals.   When the input image is determined to be a telecine image by 2-3 pull-down, a first mode for displaying the same image in a frame for forward rotation driving and a frame for inversion driving and a second mode for displaying different images are displayed. 2. The liquid crystal display device according to claim 1, wherein switching is performed according to a phase of 2-3 pull-down.   When the input image is determined to be a telecine image by 2-3 pull-down, a first mode for displaying the same image in a frame for forward rotation driving and a frame for inversion driving and a second mode for displaying different images are displayed. 2. The liquid crystal display device according to claim 1, wherein switching is performed according to the phase of 2-3 pulldown and the output of the scene change detection means. Means for detecting whether the input image is a 60 Hz telecine-converted video signal obtained by telecine-converting a 24 Hz cinema image, means for detecting the phase, and means for detecting a scene change,
A liquid crystal display device characterized in that either or both of a write timing to the memory and a read timing from the memory are changed according to the outputs of the telecine detection means, the telecine phase detection means and the scene change detection means.

Images