JP2008197334A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a moving picture display characteristic approximate to that of an impulse type of a CRT and the like by constituting the backlight of a liquid crystal display (LCD) in such a manner that a light spot is two-dimensionally scanned. <P>SOLUTION: The LCD device irradiates the back surface of a liquid crystal panel 1 with the light spot 3 of a prescribed size emitted from a backlight light source 2 by a two-dimensional scanning means 4. In addition, a timing controller 5 controls the two-dimensional scanning means 4 and a driver 6 which updates the data of the pixel of the liquid crystal panel 1 on the basis of a video signal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  According to the present invention, in a liquid crystal display device that displays an image by irradiating light emitted from a backlight light source onto a liquid crystal panel, the light emitted from the backlight light source is a light spot having a predetermined diameter, and the liquid crystal panel has a horizontal direction. The present invention relates to an apparatus for improving moving image display characteristics by a configuration in which two-dimensional scanning is performed at a predetermined timing in the vertical direction.

  The liquid crystal display device (hereinafter referred to as LCD) is a hold type as described in “Shinpei Naemura: First Liquid Crystal Display Technology, Industrial Research Committee, P188”, and in general, a cathode ray whose moving image display performance is an impulse type. It is inferior to a tube display device (hereinafter referred to as CRT).

As an improvement measure, the motion of the image is detected, and the light source is intermittently driven according to the dimming pulse having a different period, phase, or pulse width according to the motion detection result, so that the optimum according to the amount of motion is achieved. There is one that causes a light source to emit light at timing (see, for example, Patent Document 1). There is also a scan backlight method in which a plurality of backlights are sequentially blinked in accordance with the line sequential scanning of the liquid crystal panel (for example, see Non-Patent Document 1).
JP 2002-287700 A (paragraphs 0019 to 0020, paragraph 0091, paragraphs 0094 to 0096, FIGS. 1 and 3) Shohei Naemura, “First Liquid Crystal Display Technology” Engineering Research Committee, April 20, 2004, p. 190)

  However, in the conventional liquid crystal display device with improved moving image characteristics, for example, the liquid crystal display device according to Patent Document 1 requires image motion detection means and backlight dimming means, and high-speed arithmetic processing is required to realize this. In addition, the liquid crystal display device according to Non-Patent Document 1 requires a plurality of backlights, requires a dimming control for each of the plurality of backlights, and also in the same document. Although described, there has been a problem that the screen brightness is greatly reduced.

  An object of the present invention is to provide a liquid crystal display device having a moving image display characteristic close to that of an impulse-type display device with a relatively simple configuration, and with little reduction in screen luminance.

  A liquid crystal display device according to the present invention includes a liquid crystal panel that transmits or blocks incident light from the back of the panel based on a video signal and displays an image on the front of the panel, and a driver that scans the liquid crystal panel line-sequentially from top to bottom. A timing controller that outputs a control signal for controlling the driver; a light source that emits a light spot of a predetermined size; and the light spot that is two-dimensionally in a horizontal direction and a vertical direction on the back surface of the liquid crystal panel at predetermined cycles. And two-dimensional scanning means for scanning.

  In the present invention, since the backlight of the LCD is configured to two-dimensionally scan the light spot, there is an effect that moving image characteristics similar to those of the impulse type can be obtained.

Embodiment 1 FIG.
FIG. 1 is a functional block diagram showing schematic functions of the LCD according to Embodiment 1 of the inventive device. In the figure, the back surface of the liquid crystal panel 1 is illuminated with a light spot 3 emitted from a backlight light source 2 and scanned by a two-dimensional scanning means 4. The timing controller 5 generates a liquid crystal panel control signal for sequentially scanning the liquid crystal panel 1 from the upper line to the lower line based on the scanning control signal for controlling the two-dimensional scanning means 4 and the vertical synchronizing signal and horizontal synchronizing signal of the image signal. The driver 6 drives the pixels of the liquid crystal panel 1 based on the liquid crystal panel control signal.

  FIG. 2 is a schematic diagram showing an example of the scanning order of two-dimensional scanning on the back surface of the liquid crystal panel 1 of the light spot 3 in the first embodiment of the present invention. In the drawing, the arrows indicate the order in which the light spot 3 scans the back surface of the liquid crystal panel 1.

  FIG. 3 is a diagram showing the pixel transition area and the pixel stability area of each line in consideration of the response time of the liquid crystal panel in line sequential scanning of the liquid crystal panel 1 in Embodiment 1 of the present invention. The vertical axis represents the line of the liquid crystal panel 1, and the horizontal axis represents the time axis. The uppermost vertical axis indicates the uppermost first line of the liquid crystal panel 1, and the lowermost indicates the lowest line of the liquid crystal panel 1.

  4 is a partially enlarged view of FIG. 3 in the first embodiment of the present invention. A scanning region indicating the time during which the light spot 3 is scanning for each line is additionally illustrated. This is a schematic diagram in which the start timing of the scan area, in other words, the range of the delay time for starting the two-dimensional scan starting from the vertical synchronization signal can be geometrically understood.

  FIG. 5 is a schematic diagram showing a scanning method of a two-dimensional scan when the horizontal light amount integral value of the light spot 3 is not constant in the first embodiment of the present invention. The left side of the figure shows the order of the two-dimensional scanning of the light spot 3 and the overlap of the light spot 3 as in FIG. 2, the right side shows the vertical position of the liquid crystal panel 1 and the horizontal axis shows the light amount integration in line units. Figure showing the values.

  Unlike the CRT, the liquid crystal panel 1 is a hold type in which the pixel transmittance is held after the pixel data (transmittance) is updated. Therefore, when the backlight is constantly illuminated without blinking, blurring occurs due to the synergistic effect of the tracking operation of the human eye and the time integration effect of the visual system during moving image reproduction. On the other hand, since the CRT is an impulse type in which one pixel emits light sufficiently, the time integration effect can be ignored and no blurring of the image occurs. Therefore, if the LCD backlight is an impulse type with respect to the pixels, image blurring does not occur even in moving images, and moving image reproduction performance equivalent to CRT can be realized.

  In the present invention, the backlight of the liquid crystal panel 1 is made a light spot of a predetermined size, and the back of the liquid crystal panel 1 is line-scanned from top to bottom in the same manner as the CRT. By doing so, the period during which one pixel of the liquid crystal panel 1 emits light is greatly shortened, and an impulse-type display can be realized.

  Hereinafter, the operation of the first embodiment will be described in detail with reference to FIGS. 1 to 4. The liquid crystal panel 1 shown in FIG. 1 is based on a line-sequential scanning driving system with a total number N of lines. The liquid crystal panel 1 has a configuration in which the highest line is one line and the lowest line is N lines. Then, starting from the vertical synchronizing signal of the video signal, first, the uppermost line is driven and updated, and the driving update is performed in synchronization with the horizontal synchronizing signal up to the Nth line, which is the lowest line, sequentially one line at a time. Therefore, the line update cycle for each line is substantially the same as the horizontal sync signal cycle. Assuming that the period of the vertical synchronization signal is T, the update period dt for each line is expressed by the following equation because N-line horizontal scanning is performed for each horizontal synchronization signal.

  The timing controller 5 and the driver 6 have a function of scanning the liquid crystal panel 1 line-sequentially based on the video signal.

  When the light amount distribution in the light spot 3 is substantially constant, the light spot 3 can be regarded as having a size having a vertical dimension of 1 / integer with respect to the total pixel length in the vertical direction of the liquid crystal panel 1. In the example shown in FIGS. 1 and 2, the vertical size of the light spot 3 is set to 1/5 of the total vertical pixel length of the liquid crystal panel 1. Accordingly, in this example, five horizontal scans are sequentially performed from the top to the bottom for each period of the vertical synchronization signal, and the rear surface of the liquid crystal panel 1 is two-dimensionally scanned from the top to the bottom. In this figure, the horizontal scanning direction is from left to right, but it may be reversed.

  For example, assuming that the liquid crystal panel 1 conforms to the HD 1080p standard, the total number N of lines is 1125. The vertical size of the light spot 3 is 225, for example, if it is 1/5 of the total number of lines as shown in the figure. On the other hand, if the total number of horizontal pixels is 2200, and the horizontal size of the light spot 3 is the same as the vertical size, the horizontal size of the light spot 3 with respect to the total number of horizontal pixels can be calculated as approximately 1 / 9.88. . Therefore, the size of the light spot 3 with respect to all the pixel surfaces of the liquid crystal panel 1 (assuming the shape of the light spot 3 is square) is expressed by the following equation.

  Since the light spot 3 having an area of 48.9 is scanned in the same period on the entire screen of the liquid crystal panel 1, the irradiation time per pixel is about 48.9 minutes as compared with the conventional method. Thus, the irradiation time can be greatly shortened. As a result, it becomes a characteristic close to an impulse type, and it is possible to realize a moving image display performance without blur.

  Next, an efficient shape of the light spot 3 and a scanning order will be described. FIG. 2 shows an example of the order in which the light spot 3 scans the back surface of the liquid crystal panel 1. In this figure, the shape of the light spot 3 is defined as a square. Even if the light amount distribution of the light spot 3 is uniform, if the horizontal length of the light spot 3 is not uniform, a difference occurs in the irradiation time of the pixels in the vertical direction due to the horizontal scanning. Pixels (lines) scanned in an area where the horizontal length of the light spot 3 is long are bright, whereas pixels (lines) scanned in an area where the horizontal length is short are dark. Therefore, in this embodiment, the shape of the light spot 3 is a square having a uniform horizontal length.

  Thus, the shape of the light spot 3 is preferably a square when the light amount distribution of the light spot 3 is uniform, but is not limited to this when the light amount distribution is not uniform. An optimal solution is a shape in which the horizontal integrated value of the light amount distribution of the light spot 3 in each pixel line is a constant value.

  In FIG. 2, the light spot 3 first scans the back surface of the liquid crystal panel 1 from the position a to the position aa, starting from the vertical synchronization signal. Next, it instantaneously moves from the position aa to the position b. Similarly, b, bb and c, c, cc and d are repeated. Finally, after moving from e to ee, the robot instantaneously moves to the starting point a. These series of operations are performed so as to be completed in one cycle of the vertical synchronizing signal. If the operation trajectory is defined in this way, the light spot 3 always scans without turning off the liquid crystal panel 1, so that the light use efficiency is high, and as a result, a bright screen display is possible. Further, since the scanning order is defined to scan in the same direction as the line sequential scanning of the liquid crystal panel 1, that is, from the top to the bottom of the screen, and further defined in the same cycle as the line sequential scanning, the response of the liquid crystal panel of the liquid crystal panel 1 described later A configuration that is not affected by time can be adopted.

  Such scanning of the light spot 3 is performed by the two-dimensional scanning means 4 of FIG. 1, and specifically, for example, can be realized by two polygon mirrors (not shown). A horizontal scanning polygon mirror that performs horizontal scanning and a vertical scanning polygon mirror that performs vertical scanning can be combined in series.

  The backlight light source 2 is required to have a function of outputting a strong amount of white light. In this embodiment, there is no need to blink, it is only necessary to supply a predetermined amount of light, and there is no need to respond quickly to the light emission command value. Therefore, the backlight light source 2 can be composed of a wide variety of light sources such as mercury lamps and white LEDs.

  In the above description, the shape in which the integral value in the horizontal direction of the light amount distribution of the light spot 3 in each pixel line is a constant value has been described as an example. However, the present invention can be applied even when this condition is not satisfied. is there. FIG. 5 shows an example of a two-dimensional scan suitable when the light amount distribution of the light spot 3 is not constant.

  In FIG. 5, the size of the light spot 3 is one or more times the number of horizontal scans in one vertical scan with respect to the total pixel length in the vertical direction of the liquid crystal panel 1. Further, the horizontal integrated value of the light amount distribution of the light spot 3 in each pixel line is a large value in the center region of the light spot and small on the upper and lower sides as shown in the stipple region on the right side of the figure. It has trapezoidal characteristics.

  In such a case, as in the description of FIG. 2, the light spot 3 first scans the back surface of the liquid crystal panel 1 from the position a to the position aa, starting from the vertical synchronization signal. Next, it instantaneously moves from the position aa to the position b. Similarly, b, bb and c, c, cc and d are repeated. Finally, after moving from e to ee, the robot instantaneously moves to the starting point a. These series of operations are performed so as to be completed in one cycle of the vertical synchronizing signal. If the operation trajectory is defined in this way, the light spot 3 always scans without turning off the liquid crystal panel 1, so that the light use efficiency is high, and as a result, a bright screen display is possible. Further, since the scanning order is defined to scan in the same direction as the line sequential scanning of the liquid crystal panel 1, that is, from the top to the bottom of the screen, and further defined in the same cycle as the line sequential scanning, the response of the liquid crystal panel of the liquid crystal panel 1 described later A configuration that is not affected by time can be adopted. This is the same as the effect already described in FIG.

  Further, in the horizontal integrated value of the light amount distribution of the light spot 3, the lower light amount reduction region is overlapped with the upper light amount reduction region of the next horizontal scanning. The vertical line area on the right side of the figure shows the overlap of the lower light amount shortage of the previous horizontal scan and the upper light amount shortage of the current horizontal scan. Since the overlap amount can be simply added to the integrated light amount in units of lines, it is added to the horizontal axis of the figure, and a substantially constant light amount can be realized regardless of the vertical position of the liquid crystal panel 1. This makes it possible to perform a two-dimensional scan with a constant light amount for all the pixels of the liquid crystal panel 1.

  Next, a response to the optical response time of the liquid crystal of the liquid crystal panel 1 will be described. The optical response time is an error within a predetermined value (for example, 10%) with respect to the final value when the transmitted light intensity has sufficiently passed the drive voltage when the drive voltage is applied to the liquid crystal of the liquid crystal panel 1. It is defined as the time until. Therefore, even if a drive signal is applied from the driver 6, the pixels of the liquid crystal panel 1 do not react immediately, and pixels whose transmitted light intensity is substantially in accordance with the drive signal are determined after the response time of the liquid crystal panel. Here, a state in which the pixels of the liquid crystal panel 1 are responding is defined as a pixel transition region, and a state in which pixels after the response time are determined is defined as a pixel stable region.

  FIG. 3 is a diagram showing a pixel transition region and a pixel stability region of each line in consideration of the response time of the liquid crystal panel in the line sequential scanning of the liquid crystal panel 1. The vertical axis represents the line of the liquid crystal panel 1, and the horizontal axis represents the time axis. The uppermost vertical axis indicates the uppermost first line of the liquid crystal panel 1, and the lowermost indicates the lowest line of the liquid crystal panel 1. The vertical axis indicates the effective pixel line indicating the effective pixel area and the total pixel line indicating the total pixel area (the total number of pixel lines is N). A region that is not an effective pixel line is a so-called blanking period of a vertical scanning signal. In this figure, td is the response time of the liquid crystal panel.

  From the figure, even if the first line is irradiated with the light spot 3 from the vertical scanning signal as a starting point, it becomes a pixel transition region, the transmittance of the pixel is not fixed, and accurate pixel information cannot be displayed. In order to obtain accurate pixel information, it is necessary to perform the irradiation timing of the light spot 3 not in the pixel transition region of FIG. Hereinafter, the conditions under which the light spot 3 scans the pixel stable region will be described in detail.

  FIG. 4 is a partially enlarged view of FIG. 3 so that the state transition of one line unit in FIG. 3 can be seen. In the drawing, the line 1 to the line k and the line (N−2) to the final line N are enlarged and displayed. The vertical axis and the horizontal axis are the same as those in FIG. 3, and the vertical hatched portion in FIG.

  Assume that the vertical size of the light spot 3 is k lines in terms of lines. In this case, the number n of horizontal scans in one vertical synchronization period is obtained by dividing the total number of pixel lines N by k, and is expressed by the following equation.

  The scanning time Th of the light spot 3 per line is obtained by dividing the vertical synchronization period T by the number of horizontal scans n, and is given by the following equation.

  The period during which the line is irradiated by the horizontal scanning of the light spot 3 is defined as a scanning region, and is displayed in the stippled area in the figure. As described above, the scan area needs to be performed in the pixel stable area, not in the pixel transition area in FIG. Therefore, the condition for arranging the scan area in the pixel stable area is obtained. The scan area has a vertical size of k lines that is the vertical size of the light spot 3, and a horizontal size of Th.

  An example where the delay time is the shortest starting from the vertical synchronization signal, that is, the two-dimensional scan operation start area is shown in FIG. . Similarly, an example in which the delay time is the longest, that is, a two-dimensional scan operation start region is indicated as B. The conditions for A are shown below.

  The pixel update time dt for each line is as follows.

ｋライン目の画素更新の総時間ｋｄｔは、次式の通り。

The total pixel update time kdt for the k-th line is as follows.

  When the delay time in the case of A is Td (A), it is the sum of the response time td and the kdt, and is given by the following equation.

  On the other hand, when the delay time in the case of B is Td (B), the scanning time Th of the light spot 3 per line is subtracted from the vertical scanning period T, and therefore, the following equation is obtained.

  Accordingly, the condition that the scan area is arranged not in the pixel transition area but in the pixel stable area is that Td (A) and Td (Td (A) and Td ( Since it may be set during (B), it is as follows.

上記の式に基づいて、２次元スキャンを開始するタイミングを設定すれば、光スポット３は必ず画素安定領域を走査するので、正確な画像表示が可能となる。

If the timing for starting the two-dimensional scan is set based on the above formula, the light spot 3 always scans the pixel stable region, so that an accurate image display is possible.

  As described above, according to the first embodiment of the present invention, since the light spot 3 is two-dimensionally scanned on the back surface of the liquid crystal panel 1, a moving image display performance without blur can be realized. Furthermore, since the start timing of the two-dimensional scan is set to be delayed based on an arithmetic expression that takes into consideration the optical response time of the liquid crystal of the liquid crystal panel 1, accurate image display is always possible.

It is a block diagram which shows the schematic function of LCD of Embodiment 1 of this invention. It is a schematic diagram which shows an example of the scanning order of the two-dimensional scan in the back surface of the liquid crystal panel 1 of the light spot 3 of Embodiment 1 of this invention. It is a figure which shows the pixel transition area | region and pixel stable area | region of each line which considered the response time of the liquid crystal panel in the line sequential scanning of the liquid crystal panel 1 of Embodiment 1 of this invention. FIG. 4 is a partially enlarged view of FIG. 3. FIG. 4 is a schematic diagram illustrating an example of a scanning order of a two-dimensional scan on the back surface of the liquid crystal panel 1, which is preferable when the light amount distribution of the light spot 3 is not uniform.

Explanation of symbols

  1 liquid crystal panel, 2 backlight source, 3 light spot, 4 two-dimensional scanning means, 5 timing controller, 6 driver.

Claims (6)

A liquid crystal panel that transmits or blocks incident light from the back of the panel based on a video signal and displays an image on the front of the panel;
A driver for line-sequentially scanning the liquid crystal panel from top to bottom;
A timing controller that outputs a control signal for controlling the driver;
A light source that emits a light spot of a predetermined size;
2. A liquid crystal display device comprising: a two-dimensional scanning unit that two-dimensionally scans the light spot in the horizontal direction and the vertical direction on the back surface of the liquid crystal panel at a predetermined period.   2. The liquid crystal display device according to claim 1, wherein the shape of the light spot is set so that a horizontal integrated value of a light amount distribution of the light spot in each pixel line is a constant value.   The liquid crystal display device according to claim 2, wherein the shape of the light spot is substantially rectangular.   2. The horizontal scan overlaps with the immediately preceding scan when the horizontal integrated value of each pixel line in the light amount distribution of the light spot has a large light spot center and a small periphery. Liquid crystal display device.   In the two-dimensional scanning means, the vertical scanning period of the two-dimensional scanning is a period of the vertical synchronizing signal of the video signal, the horizontal scanning period of the two-dimensional scanning is set to 1 / integer times the vertical scanning period, 2. The liquid crystal display device according to claim 1, wherein the two-dimensional scanning is performed in order from the top to the bottom of the liquid crystal panel. In the two-dimensional scanning means, the response period of the liquid crystal panel is td, the period of the vertical synchronizing signal of the video signal is T, and the horizontal scanning period of the two-dimensional scanning is 1 / n times the vertical scanning period (n is a natural number). 3. The liquid crystal display device according to claim 2, wherein, when set, a scanning start point of the two-dimensional scanning means is set from the vertical synchronizing signal by a delay time Td of the following equation.

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