JP2008304580A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve high-grade OSD display easy-to-view for a user even when dynamically modulating light emission luminance of a back light source according to an input video signal. <P>SOLUTION: The image display device is equipped with: an APL detection section 6 for detecting an average luminance level that is the featured value of the input video signal; a control microcomputer 8 for dynamically and variably controlling the light emission luminance of the back light source 9 on the basis of the detected APL; and an OSD section 1 for superposing an on-screen display image signal for OSD display on the input video signal. The control microcomputer 8 performs the change of a magnification factor of the OSD display in the OSD section 1 and/or the change of trimming display of the periphery of the OSD display in accordance with the APL of the input video signal detected by the APL detection section 6. Even when the luminance of back light is lowered in accordance with the APL, visibility of the OSD display is prevented from being deteriorated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image display apparatus that displays an image by illuminating a light-receiving light modulation means with a backlight light source, and more specifically, an image that dynamically modulates the luminance of a backlight light source in accordance with an input video signal. The present invention relates to a display device.

  2. Description of the Related Art Image display devices that display an image using a liquid crystal panel as a light receiving type light modulation means are widely used for image display of television receivers, computer devices, and the like. As is well known, an image display device using a liquid crystal panel encloses a liquid crystal between two transparent substrates provided with electrodes, and controls the voltage in units of drive electrodes arranged in a matrix. An image is displayed on the liquid crystal panel by controlling the group and orientation of the molecules and changing the transmittance of the irradiation light from the backlight source provided on the back surface of the transparent substrate.

  In such an image display device, the luminance level of the backlight light source can be set to a value manually adjusted (dimmed) by the user. In this case, the backlight light source is independent of the input video signal. The brightness level of is constant. On the other hand, in order to make the display image easier to see or to reduce power consumption, an image of a method that dynamically adjusts the brightness of the backlight light source according to the input video signal that changes from screen to screen at any time. A display device is provided.

  For example, in Patent Document 1 and Patent Document 2, an average luminance level (APL: Average Picture Level) of an input video signal is detected, and when the detected average luminance level is large, the light source luminance is decreased, and when the detected average luminance level is small, the light source luminance is increased. Thus, there has been proposed a display capable of displaying a moving image with sharpness (in which dynamic contrast is enlarged) by changing the screen brightness even when the display has the same image gradation.

  In general, in this type of image display device, various information such as a setting menu screen prepared in advance, a current time, a setting mode such as a channel selection channel, and character characters according to the operation mode are superimposed on the input video signal. It has an OSD (On Screen Display) function to display (synthesize). By using the OSD function, it is possible to realize a user interface function and to notify various information to the user.

Here, a conventional image display device capable of dynamically modulating the luminance of the backlight light source in accordance with the feature amount of the input video signal will be described with reference to FIGS.
As shown in FIG. 4, the conventional image display apparatus reads out a predetermined on-screen display image signal from a character generator (memory) (not shown), superimposes (synthesizes) it on an input video signal, and outputs it, A liquid crystal controller 2 that outputs a liquid crystal drive signal to the gate driver 4 and the source driver 5 of the liquid crystal panel 3 based on the display video signal on which the on-screen display image signal is superimposed (synthesized) by the OSD unit 1 is provided. .

  In addition, an APL detection unit 6 that detects an average luminance level of the input video signal for each screen, a remote control light receiving unit 7 that receives an instruction signal input by a user using a remote controller (remote controller) (not shown), and the remote control light reception The instruction signal received by the unit 7 is detected and analyzed, the OSD unit 1 is controlled to superimpose (synthesize) a predetermined on-screen display image signal on the input video signal, and detected by the APL detection unit 6 And a control microcomputer 18 for controlling the light source driving unit 10 such as an inverter circuit for driving the backlight light source 9 based on the average luminance level.

The control microcomputer 18 refers to a look-up table using a built-in ROM (not shown), or performs an operation using an approximate function, or the driving voltage value (or current) of the backlight light source 9 with respect to the average luminance level of the input video signal. By adaptively changing the value), the screen luminance (brightness) characteristics as shown in FIG. 5 can be realized.
FIG. 5A is a graph showing an example of the relationship between the average luminance level (APL) of the input video signal and the screen luminance, and FIG. 5B shows the APL corresponding to FIG. 5A and the screen luminance. It is a table | surface which shows a numerical value. That is, as shown in FIG. 5, in the example of the light emission luminance control of the backlight light source, the light emission luminance of the backlight light source is lowered and the screen luminance is lowered as the average luminance level of the input video signal increases. . In the light emission luminance control, contrary to the above example, the light emission luminance of the backlight is increased as the average luminance level of the input video signal increases. There is also known a technique in which the average luminance level is divided into a plurality of regions, and the light emission luminance of the backlight is maintained or increased or decreased for each region.

  In the prior art according to the above-mentioned patent document, when OSD display is performed on the screen by an on-screen display image signal, the luminance (brightness) of the OSD display unit that should be stable independently of the displayed video content is also input video. There has been a problem that the display quality changes as the signal changes, giving the user a sense of incongruity and degrading the display quality.

In order to solve such a problem, for example, Patent Document 3 discloses a high-quality image whose brightness does not fluctuate even when the light emission luminance of the backlight light source is dynamically modulated according to the input video signal. An image display device capable of performing OSD display is disclosed. The image display device includes a liquid crystal panel that displays an input video signal using a backlight light source, an APL detection unit that detects an average luminance level of the input video signal, and a backlight light source based on the detected average luminance level. A control microcomputer that dynamically and variably controls the emission luminance of the light source, and an OSD unit that superimposes (synthesizes) a predetermined on-screen display image signal on the input video signal. The control microcomputer variably controls the brightness level of the on-screen display image signal in accordance with the light emission brightness of the backlight light source. Here, the on-screen display image signal is stored in a character generator (memory). At this time, an on-screen display image signal having a different luminance level is stored, and is appropriately read and used.
In addition, there is a display that stops the dynamic control of the light emission luminance of the backlight light source during OSD display.
JP-A-8-201812 WO03 / 38799 gazette JP-A-2005-321423

The screen brightness (brightness) of the image display device is determined by the product of the transmittance of the liquid crystal panel and the light emission brightness (light quantity) of the backlight light source. That is, by dynamically changing the light emission luminance of the backlight light source, that is, the screen luminance in accordance with the content of the video to be displayed, the result is that the image quality of the moving image is sharpened, and high image quality can be realized.
However, when OSD display is performed using an on-screen display image signal, the screen brightness (brightness) of the OSD display, which should be stable independently of the display video content, also changes as the input video signal changes. As a result, the user feels uncomfortable and the display quality deteriorates.

  FIG. 6 is a diagram for explaining video display brightness and OSD display brightness in a conventional image display apparatus. As shown in FIG. 6A, in a dark image having a relatively low average luminance level (APL), the luminance of the backlight is increased, so that the OSD display having a predetermined luminance signal level is also brightened accordingly. . Further, as shown in FIG. 6B, in a bright image having a relatively high average luminance level, the luminance of the backlight is reduced, and the OSD display having a predetermined luminance signal level is darkened accordingly. That is, the screen brightness of the OSD display changes according to the light emission brightness control of the backlight following the average brightness level. At this time, when the brightness of the backlight light source decreases, if the screen brightness of the OSD display decreases too much, the OSD display itself becomes difficult for the viewer to see and the OSD visibility deteriorates. .

  Further, as in Patent Document 3, when there are a plurality of data of on-screen display image signals having different luminance levels, the number of memories for storing the data increases. In this case, it is possible to prepare an on-screen display image signal to be superimposed on the input video signal at multi-level luminance levels, but there are problems with the increase in cost due to the increase in memory capacity and the appropriateness of mounting. Arise. In addition, when the memory capacity is reduced, the amount of data is reduced, causing a problem that the user feels uncomfortable when viewing.

  The present invention has been made in view of the above circumstances, and even when the light emission luminance of the backlight light source is dynamically modulated in accordance with the input video signal, it is easy for the user to view and enables high-quality OSD display. It is an object to provide an image display device.

  In order to solve the above-mentioned problems, a first technical means of the present invention includes a light receiving type light modulation means for displaying an input video signal using a backlight light source, and a feature quantity detection means for detecting a feature quantity of the input video signal And light source control means for dynamically variably controlling the light emission luminance of the backlight light source based on the detected feature amount, and an on-screen display image signal for superimposing an on-screen display image signal for OSD display on the input video signal An on-screen display image signal superimposing unit changes an enlargement ratio of an OSD display to be displayed by an on-screen display image signal according to the feature amount detected by the feature amount detecting unit. And / or changing the border display around the OSD display.

  According to a second technical means, in the first technical means, the on-screen display image signal superimposing means performs the border display by changing the border display around the OSD display, and the feature quantity detected by the feature quantity detection means. The width of the border display is changed according to the above.

  The third technical means is the second technical means, wherein the on-screen display image signal superimposing means is an intermediate color between the OSD display color and the background color of the OSD display, or the color of the OSD display as the border display color. It is characterized by setting complementary colors.

  A fourth technical means is the technical means according to any one of the first to third aspects, wherein the on-screen display image signal superimposing means divides a possible range of the feature quantity into a plurality of ranges in advance, and divides the range of each feature quantity. Accordingly, information defining the OSD display enlargement ratio and / or surrounding border display method is stored, and the feature quantity detected by the feature quantity detection means belongs to which of the divided feature quantity ranges. An on-screen display image signal for OSD display is superimposed on an input video signal in accordance with an OSD display magnification rate determined according to the determined feature amount range and / or a surrounding bordering method. It is.

  According to a fifth technical means, in any one of the first to fourth technical means, the feature amount of the input video signal is any one of an average luminance level, a maximum luminance level, a minimum luminance level, and a luminance distribution state of the extracted video signal. Or one or a combination of two or more.

  According to the present invention, it is possible to provide an image display device that enables high-quality OSD display that is easy to see for the user even when the light emission luminance of the backlight light source is dynamically modulated in accordance with the input video signal.

  FIG. 1 is a block diagram showing an embodiment of an image display device according to the present invention. In FIG. 1, the same parts as those in the conventional example described above are denoted by the same reference numerals, and redundant description is omitted except for the parts characterizing the present invention. As shown in FIG. 1, the image display apparatus according to the present embodiment is detected by an APL detection unit 6 that detects an average luminance level (APL) per screen as a feature amount of an input video signal, and an APL detection unit 6. A control microcomputer 8 that drives and controls the light source driving unit 10 based on the average luminance level of the input video signal to modulate the light emission luminance of the backlight light source 9 is provided. The APL detection unit 6 is a feature amount detection means of the present invention.

  The control microcomputer 8 detects and analyzes the instruction signal received by the remote control light receiving unit 7 and controls the OSD unit 1 to superimpose (synthesize) a predetermined on-screen display image signal on the input video signal. The control microcomputer 8 controls the OSD unit 1 to change the enlargement ratio of the OSD display displayed by the on-screen display image signal according to the average luminance level of the input video signal detected by the APL detection unit 6. The border display around the OSD display is changed. Further, when displaying the peripheral border, control is performed to change the border width according to the average luminance level.

  The OSD display magnification data and border data corresponding to the average luminance level are stored in advance in a character generator (memory) (not shown), and the OSD unit 1 superimposes the on-screen display image signal on the input video signal. When this is done, a specific on-screen display image signal is read in accordance with an instruction from the control microcomputer 8 and superimposed on the input video signal. At this time, the on-screen display image signal generated by the character generator may be adjusted in accordance with an instruction from the control microcomputer 8.

  That is, the control microcomputer 8 dynamically variably controls the emission luminance of the backlight light source 9 according to the average luminance level (APL) of the input video signal. At the same time, when performing OSD display, the control microcomputer 8 averages the input video signal. Control is performed to change the enlargement ratio of the OSD display according to the brightness level, or to provide a frame around the OSD display and change the width of the frame. Here, for example, when the light emission luminance of the backlight light source is lowered in accordance with the average luminance level of the input video signal, the enlargement ratio of the OSD display is increased, or a frame is provided around the OSD display. It becomes possible to prevent deterioration of the visibility of the OSD display accompanying the decrease in screen brightness.

  Further, the OSD display control function according to such an average luminance level can be configured to be turned on / off by a user setting. For example, in this case, the OSD display control function can be turned ON / OFF by the user performing a predetermined operation using the remote controller. When the OSD display control function is ON, the OSD display dynamic control is executed according to the dynamic control of the light emission luminance of the backlight light source according to the average luminance level of the input video signal. When it is OFF, the OSD display dynamic control is not executed even when the light emission luminance of the backlight light source is dynamically controlled according to the average luminance level.

  In the configuration of FIG. 1, the light receiving type light modulating means of the present invention is the liquid crystal panel 3, and the light source control means of the present invention is realized by the control microcomputer 8 and the light source driving unit 10. The on-screen display image signal superimposing means of the present invention is realized by the OSD unit 1 and the control microcomputer 8.

  In the image display device of the present embodiment, either a direct type backlight system or a side edge type backlight system may be used, and the backlight light source 9 is a cold cathode tube (CCFL) that is generally used at present. In addition, a light emitting diode (LED) or the like may be used, or a combination of these may be used. Needless to say, the luminance control method of the backlight light source 9 is not limited to voltage (or current) control, and may employ duty control.

FIG. 2 is a flowchart for explaining an example of OSD display control processing in the image display apparatus according to the present invention.
In the image display device, dynamic control of the light emission luminance of the backlight light source according to the feature amount of the input video signal is started under a predetermined condition (step S1). Here, the dynamic control of the backlight light source is, for example, by detecting the movement of the input video signal, and if the input video signal is a moving image, the backlight light source dynamic control is automatically activated and the input video signal is a still image. For example, it can be set not to execute automatic control of the backlight light source. Alternatively, an operation input for turning on / off the dynamic control of the backlight light source may be enabled, and the dynamic control may be started according to the operation input.

Then, the APL detector 6 of the image display device detects the average luminance level (APL (n)) of the current frame (assumed to be n frames) (step S2). Then, the control microcomputer 8 determines which one of the predetermined APL ranges C1 to Cn corresponds to the detected APL (n) (step S3).
The APL ranges C1 to Cn are obtained by dividing the range that the APL can take in advance into a plurality of stages, and are set so that the display method of the OSD display can be changed according to each range C1 to Cn. For example, assuming that n = 4, the entire range of APL is divided into four stages. In this case, as an example, APL is 0% or more and less than 20% in the first range C1, APL is 20% or more and less than 40% in the second range C2, and APL is 40% or more and less than 60% in the third range C3. APL of 60% or more and 100% or less can be set as the fourth range C4. At this time, by increasing the number of divisions, finer display control can be performed. Data in the set range is held in a memory included in the control microcomputer 8 or a character generator provided in the OSD unit 1.

Then, the control microcomputer 8 determines which of the predetermined APL ranges C1 to Cn the APL (n) detected by the APL detection unit 6 belongs to (step S3). Then, the OSD display is controlled according to any one of the determined APL ranges C1 to Cn (step S4).
In this case, in the image display device, a display method for performing OSD display is determined for each of the predetermined APL ranges C1 to Cn. Here, the enlargement ratio of the OSD display, the presence / absence of the border around the OSD display, the border width when the border is displayed, the border color, and the like are determined. In this case, when the light emission luminance of the backlight light source is low, the OSD display is enlarged so that the visibility of the OSD display is not deteriorated by the dynamic control of the light emission luminance of the backlight light source according to the feature amount of the input video signal. It is determined to increase the rate, to give a border around the OSD display, and to further increase the border width as the light emission luminance of the backlight light source decreases. Specific examples of these OSD display controls will be described later.

  If the dynamic control of the backlight light source has been completed (step S5-YES), the control microcomputer 8 also terminates the OSD display control process. If the dynamic control of the backlight source is continued (step S5-NO), n = n + 1 is set (step S6), the process returns to step S2, and the same OSD display control is continued for the next frame.

  In the above example, the OSD display control is performed according to the APL detected for each frame. However, when the change of the APL of the input video signal is large, the accompanying change in the OSD display is also large. In order to alleviate such changes in OSD, a plurality of frames are set as one control unit, an average value (or maximum value, minimum value, etc.) of APLs of a plurality of frames is detected, and the above-mentioned is performed according to the value. You may make it perform OSD display control according to APL range.

FIG. 3 is a diagram for explaining a display control example of the OSD display according to the feature amount of the video signal. Here, a control example of night character display on the OSD according to APL will be described. In FIG. 3, 21 is a character displayed on the OSD, and 22 is a border added around the character displayed on the OSD.
FIG. 3A shows an example of an OSD display in a normal display state in which dynamic control of OSD display according to the present invention is not performed. FIG. 3B shows a state in which the light emission luminance of the backlight light source is lowered in accordance with the APL of the input video signal. As shown in FIG. 3B, when the OSD-displayed character 21 is displayed as it is when the light emission luminance of the backlight light source decreases, the screen luminance of the character 21 also decreases, 21 may become dark and difficult to visually recognize.

FIG. 3C is a diagram illustrating an example of OSD display control when the light emission luminance of the backlight light source is lowered. In the example of FIG. 3C, the OSD-displayed character 21 is enlarged and displayed, so that deterioration of the visibility of the OSD display is prevented even when the light emission luminance of the backlight light source is reduced.
The enlargement ratio can be set stepwise as appropriate according to the APL range C1 to Cn. For example, when control is performed to increase the light emission luminance of the backlight light source as the average luminance level is lower, the enlargement ratio is 1.0 times in order from C1 to Cn where the light emission luminance of the backlight light source is higher (no enlargement). , 1.1 times, 1.2 times, 1.3 times,...

  FIG. 3D is a diagram illustrating another example of OSD display control when the light emission luminance of the backlight light source is decreased. In the example of FIG. 3D, the visibility of the OSD-displayed character 21 is deteriorated by providing a border 22 around the OSD-displayed character 21 even when the light emission luminance of the backlight light source is reduced. To prevent. At this time, the color of the border 22 can be set to an intermediate color between the background color of the character 21 displayed on the OSD and the color of the character 21. Or you may set the complementary color of the character 21 which performs OSD display. For example, in a character broadcast, a character color and a background color are designated by a broadcast signal, so an intermediate color or a complementary color can be set using the designated color information. In addition, the specified color can be used in a menu or the like for which the user specifies a color.

  The width of the rim 22 at this time can be set stepwise as appropriate according to the APL range C1 to Cn. For example, when control is performed to increase the light emission luminance of the backlight light source as the APL is lower, the width of the border 22 is set to 0 dot (no border), 1 dot, 2 dots in order from C1 to Cn where the light emission luminance of the backlight light source is higher. 3 dots...

FIG. 3E is a diagram showing still another example of OSD display control when the light emission luminance of the backlight light source is lowered. In the example of FIG. 3E, the OSD display character 21 is enlarged as shown in FIG. 3C, and a border 22 is added around the character 21 to improve the visibility of the OSD display. Yes. Such display control may be displayed, for example, when the light emission brightness of the backlight light source is lower than that in the enlarged state of FIG. 3C, and when the character 21 is enlarged, the character 21 is simultaneously displayed. You may make it provide the rim | edge 22 around the circumference | surroundings.
Further, the enlargement ratio of the character 21 at this time can be variably set in multiple stages according to the APL as described above, and the width of the border 22 can be set in multiple stages at the same time. Furthermore, at this time, the width of the border 22 may be changed in multiple steps while the enlargement ratio of the character 21 is constant, and conversely, the width of the border 22 is constant and the enlargement ratio of the character 21 is changed in multiple steps. It may be.

  In any case, according to the above example, when the light emission luminance of the backlight light source changes according to the APL of the input video signal, the OSD display is enlarged and displayed as the light emission luminance of the backlight light source decreases. By displaying the border around the OSD display and changing the width of the border at the same time, or combining them to perform OSD display, the visibility of the OSD display can be improved even when the screen brightness decreases following APL. A high-quality image display can be maintained without being lowered.

  In the above embodiment, the APL of the input video signal is divided into a plurality of stages, and the OSD display is dynamically controlled according to the divided APL. However, the target backlight controlled according to the APL is used. The OSD display may be dynamically controlled according to the light emission luminance level of the light source. In this case, the light emission luminance level of the backlight light source that can be taken in accordance with the change of APL is divided into a plurality of stages, the classification is determined from the APL detected from the input video signal, and the OSD display is performed according to the determined classification. Control dynamically. By such control, even when a complicated luminance conversion characteristic that does not uniformly increase (or decrease) the light emission luminance of the backlight light source is applied to the APL, the light emission luminance level of the backlight light source. The OSD display can be controlled according to the above.

  In another embodiment according to the present invention, the control may not be performed in accordance with the APL divided into a plurality of stages as described above, but may be changed steplessly in accordance with the APL. In this case, the on-screen display image signal generated by the character generator can be adjusted steplessly in accordance with an instruction from the control microcomputer 8. For example, the OSD display enlargement ratio is changed steplessly according to the change of APL, or the OSD display is bordered below (or above) a predetermined APL level, and the border of the border is adjusted according to the increase or decrease of APL. A configuration in which the width is increased steplessly may be used.

In each of the above embodiments, the average luminance level (APL) of the detection area in the display screen is used as the feature quantity of the input video signal. However, the present invention is not limited to this, and the specific area in the display screen The peak luminance state (presence / absence or some) of the video signal may be obtained and used for luminance modulation and OSD control of the backlight light source.
Similarly, as the feature amount of the input video signal, the feature amount obtained by using the maximum brightness level, the minimum brightness level, the brightness distribution state (histogram) in a predetermined region (period) in one frame, or a combination of two or more thereof. Based on the above, the emission luminance of the backlight light source may be variably controlled and the OSD display control may be simultaneously performed. Further, the light emission luminance of the backlight light source may be variably controlled according to the feature amount of the input video signal, and the gradation correction control of the input video signal may be performed in conjunction with this.

It is a block diagram which shows one Embodiment of the image display apparatus by this invention. It is a flowchart for demonstrating an example of the control action in the image display apparatus by this invention. It is a figure for demonstrating the display control example of OSD display according to the feature-value of the video signal in the image display apparatus by this invention. It is a block diagram which shows the example of schematic structure of the conventional image display apparatus. It is a figure which shows an example of the relationship between the average luminance level of the input video signal and image luminance in the conventional image display apparatus. It is a figure for demonstrating the brightness | luminance of a video display and the brightness | luminance of OSD display in the conventional image display apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... OSD part, 2 ... Liquid crystal controller, 3 ... Liquid crystal panel, 4 ... Gate driver, 5 ... Source driver, 6 ... APL detection part, 7 ... Remote control light-receiving part, 8 ... Control microcomputer, 9 ... Backlight light source, 10 ... Light source drive unit, 18 ... control microcomputer, 21 ... OSD-displayed characters, 22 ... border.

Claims (5)

  A light receiving type light modulation means for displaying an input video signal using a backlight light source, a feature quantity detection means for detecting a feature quantity of the input video signal, and based on the detected feature quantity, An image display device comprising: a light source control means for dynamically variably controlling emission luminance; and an on-screen display image signal superimposing means for superimposing an on-screen display image signal for OSD display on the input video signal, The on-screen display image signal superimposing means changes the enlargement ratio of the OSD display displayed by the on-screen display image signal and / or changes the border display around the OSD display according to the feature quantity detected by the feature quantity detection means. An image display device characterized in that:   2. The image display device according to claim 1, wherein the on-screen display image signal superimposing unit performs the border display by changing the border display around the OSD display. An image display device, wherein the width of the border display is changed according to the amount.   3. The image display device according to claim 2, wherein the on-screen display image signal superimposing means is an intermediate color between the OSD display color and the background color of the OSD display, or the OSD display background color as the border display color. An image display device characterized by setting a complementary color.   4. The image display device according to claim 1, wherein the on-screen display image signal superimposing unit divides a possible range of the feature quantity into a plurality of ranges in advance and divides the range of the feature quantity into the divided feature quantity ranges. Accordingly, information defining the OSD display enlargement ratio and / or the surrounding border display method is stored, and the feature quantity detected by the feature quantity detection unit is in any of the divided feature quantity ranges. The OSD display on-screen display image signal is superimposed on the input video signal in accordance with the OSD display enlargement ratio determined according to the determined feature amount range and / or the surrounding edging method. An image display device characterized by the above.   5. The image display device according to claim 1, wherein the feature amount of the input video signal includes an average luminance level, a maximum luminance level, a minimum luminance level, and a luminance distribution state of the extracted video signal. An image display device characterized by being obtained by any one or a combination of two or more.

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