JP2006042014A - Illumination control method of liquid crystal screen in portable radio terminal and portable radio terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out effective display and reduce power consumption, by switching the luminance of back light under control in consideration of color tone and contrast of the display image. <P>SOLUTION: When a user performs key operation from a key operation unit 4 of a portable telephone, image data designated by the key operation is generated to a liquid crystal display unit through a control unit. In the control unit, occurrence frequency of each luminance level is counted for color information of each one scene of the image data, and the luminance distribution of the display scene is determined. If the number of the level used as the color information outputted on the display unit out of color information represented by a prescribed number of levels is a previously set number or smaller, it is determined that the luminance is in a dispersion condition, and the luminance of the back light is darkened relatively. If the number of the level used as the color information outputted to the display unit is ovet the prescribed number, it is determined that the luminance distribution is uniform and the luminance of the back light is made brighter relatively. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a portable wireless terminal such as a cellular phone having a liquid crystal display means with a backlight as a display device, and in particular, power saving is achieved by controlling the brightness of the backlight according to the display form. Regarding technology.

  A portable wireless terminal such as a cellular phone includes a backlit liquid crystal display device for displaying a telephone number or the like during a call or during a dialing operation before starting a call, or for displaying the contents of an email when sending / receiving an email. Yes. When the terminal is in use, the backlight is always automatically turned on so that the caller can clearly see the display content. Therefore, there is a problem that power consumption increases and the usable time is shortened.

  Portable wireless terminals are usually used while going out, but since a battery (secondary battery) is used as a power source, it should be used even if it is carried when the battery is exhausted in a situation where the battery cannot be charged. Can not be. Accordingly, various ideas for reducing power consumption during use of the portable wireless terminal have been proposed. For example, Patent Document 1 includes a brightness adjusting unit that makes the brightness of the backlight variable, and reduces the brightness of the backlight during a call. This reduces power consumption and reduces battery consumption.

  Further, in Patent Document 2, in a portable information processing apparatus that can also play back moving images, when the display data is a moving image, the luminance of the backlight is relatively increased, while when the display data is a still image. Describes a technique for reducing the power consumption of the light source by lowering the luminance of the backlight relatively, thereby extending the usable time.

JP 2000-115307 A JP 2002-229499 A

  In recent mobile phones, there are an increasing number of cases of receiving and displaying still image photographs, WEB contents, and the like during a call. If the brightness is reduced, these photographs, WEB contents, etc. received and displayed during a call must be viewed with a low-light backlight, resulting in a problem that the displayed image is difficult to see.

  Similarly, even in the technique described in Patent Document 2, since the brightness of the backlight is uniformly lowered in the case of a still image, the stillness with gorgeous colors such as the above-mentioned photograph, WEB content, built-in game, etc. Even if the image is sent to the display unit of the mobile phone, if the backlight brightness is relatively low, the gorgeous colors at the corners will fade out and the appearance of the image displayed on the liquid crystal display screen will be improved. There is a problem that it cannot be realized.

  In view of the above problems, an object of the present invention is to provide an effective display by providing means for actively switching and controlling the brightness of a backlight in consideration of the color tone and contrast of a displayed image. And to reduce power consumption.

  The method for controlling backlight illumination of a liquid crystal display in a portable wireless terminal according to the present invention analyzes the color information of a display signal output to each dot constituting the liquid crystal display screen of the portable wireless terminal, and the color information constituting one screen. When the luminance level of the color information is uniformly distributed, the backlight of the liquid crystal display is relatively bright, and the luminance level of the color information constituting one screen has a discrete distribution. In this case, the backlight of the liquid crystal display is relatively darkened.

As a method of identifying the luminance level distribution of the color information, the color information is a luminance of 2 ⁿ (n is a natural number) gradations for each color of R (red), G (green), and B (blue). When the number of gradations appearing in the image data of one screen is larger than 2 ^m (m is a natural number smaller than n), the luminance level of the color information has a uniformly continuous distribution. When the number of gradations that appear in the image data of one screen is 2 ^m or less, it is determined that the luminance level of the color information has a discrete distribution.

  The portable wireless terminal of the present invention includes a wireless unit that performs wireless communication with a base station, a liquid crystal display unit that displays mail, characters such as characters, and image data such as photographs and web contents, A backlight that illuminates the liquid crystal display unit, and a control unit that transmits character data such as characters and image data such as photographs and WEB contents to the liquid crystal display unit and performs display control thereof. The luminance is switchable, and the control unit is configured to determine luminance distribution from color information of image data constituting one screen sent to the liquid crystal display unit; When the luminance distribution determining means determines that the luminance level of the color information is a discrete distribution, the luminance is switched so as to make the luminance of the backlight relatively dark, Wherein the luminance level of the serial color information has a backlight illumination control means for switching control so as to relatively brighter luminance of the backlight when it is determined that the continuous certain distribution.

  In the present invention, the signal supplied to each dot constituting the liquid crystal display screen is color information of R (red), G (green), and B (blue), even if it is a still image, a photograph, WEB content Focusing on the fact that the brightness distribution of color information differs between still images with gorgeous colors such as games and character data such as e-mail, the color information output to the display unit The state of the luminance distribution is determined by the control unit, and the brightness of the backlight of the liquid crystal display device is controlled based on the determination result.

  In other words, in the case of still images with brilliant colors such as photographs, WEB contents, and games in which the luminance distribution of the color information is uniformly continuous, the backlight is brightened and the colors are displayed in a rich manner. To be able to feel On the other hand, if the color information is character information such as text data that is output as discrete brightness levels, such as e-mail, if it is displayed so that it is legible, there is no problem even if it is a little dark and there is little influence on the appearance . Therefore, in the case of character data such as e-mail, the backlight is relatively darkened to reduce battery consumption and extend the usable time of the terminal.

  In the present invention, in the case of character data with few colors, the contents can be read even if the backlight is somewhat dark, so the lighting is relatively darkened to reduce power consumption, and the colors of photographs, WEB contents, games, etc. are gorgeous In the case of images, the backlight illumination is controlled to be brighter, so it is possible to reduce power consumption and provide a display that can be seen as beautiful in the case of images with many colors such as photographs, Effective and efficient display control can be performed while suppressing power consumption.

  FIG. 1 is a block diagram showing a configuration of a mobile phone to which the present invention can be applied. A wireless unit 1 for connecting to a line as a mobile phone, a display unit 2, and a back for illuminating the display unit 2 from the back side. The light 3, the key operation unit 4, the microphone 5 and the receiver 6 for calling, the key input from the key operation unit 4, the communication control of the wireless unit 1 or the display control of the display unit 2, etc. The control part 7 which performs illumination control of the backlight 3 in this invention, the memory | storage part 8 which stores the control program for the control part 7 to perform various controls including the control of this invention, various data, etc. are provided. The mobile phone is also provided with a speaker for incoming notification, a vibrator, a battery as a power source, etc., but is not shown because it is not directly related to the present invention.

  The display unit 2 is configured as a liquid crystal display (LCD) having a backlight 3, and the display unit 2 is read from the storage unit 8 under the control of the control unit 7 at the time of transmission. Has a function of displaying a telephone number, e-mail, web content, built-in game, or photo. The backlight 3 has a function of switching to two or more types of brightness under the control of the control unit 7. The power consumption increases as the illumination of the display unit 2 is brightened by the backlight 3, and the power consumption decreases as it is darkened.

  In the present embodiment, the control unit 7 monitors the luminance distribution of the display image data output to the display unit 2, and the luminance level is the same as image data with brilliant colors such as photographs, WEB contents, and games. If it is determined that the image data is uniformly distributed, the luminance of the backlight 3 is relatively increased to improve the appearance of the image, and the luminance level of the image data is discrete like character data such as mail. When it is determined that the average distribution is shown, the luminance of the backlight 3 is relatively lowered to reduce power consumption.

  The luminance distribution of the image data displayed on the display unit 2 is monitored by analyzing color information for each dot output from the control unit 7 to the display unit 2 for screen display. That is, in the case of character data such as e-mail, the color information of most dots excluding the position where the character is displayed is a color information signal of the same luminance indicating, for example, “white”, and the character is displayed. Since the color information signal supplied to the dots at the position is, for example, information of the same luminance indicated by a fixed character color such as “black”, “red”, “green”, etc., the luminance distribution of this signal Is obtained from the signal level (luminance level) for each color information of R, G, and B, all become discrete luminance distributions concentrated only on a specific luminance level.

  On the other hand, in the case of image data with brilliant colors such as photographs, WEB contents, games, etc., the level (brightness level) of the signal indicating the color information supplied to each dot will be various levels. When the luminance distribution is obtained, all of R, G, and B represent a uniformly continuous luminance distribution. In addition, in the case of a photograph, even a monotone photograph is displayed on the screen in shades, so the level of the signal indicating the color information (brightness level) supplied to each dot varies, and from that signal level Similarly, when the luminance distribution is obtained, it represents a uniformly continuous luminance distribution.

For example, R sent from the control unit 7 to each dot of the display unit 2, G, when the luminance level of the color information B are represented by 2 ⁷ gradations consisting level of 0 to 127, respectively, display When the data is character character data, the gradation (luminance level) of each color information of R, G, B used in the image data of one screen displayed on the display unit 2 is only a limited level. The number of appearing gradations is an extremely small value such as ten or more out of 128 luminance levels. On the other hand, when the display data is image data with brilliant colors such as photographs, WEB contents, and games, gradations (luminances) transmitted as R, G, and B color information in order to express various colors and shades. Level) can span almost all 128 levels.

Therefore, when the number of gradations that emerged more than once, for example 2 to ⁴ in the image data of one screen, the control unit 7, image data displayed on the display unit 2 is composed of discrete luminance distribution configured to determine that the character data, whereas, in the luminance level of the color information in the image data for one screen currently being displayed on the display unit 2, than the number of gradation that appeared more than once, for example 2 ⁴ If there are many, the control unit 7 is set so that the image data displayed on the display unit 2 is determined to be image data having a gorgeous color such as a photograph, WEB content, or game having a uniform luminance distribution. Keep it.

  FIG. 2 is a flowchart showing the operation for controlling the brightness of the backlight in the present embodiment, and FIGS. 3 to 6 are diagrams for explaining the operation for controlling the brightness of the backlight in the present embodiment. is there. Hereinafter, the operation of the present embodiment will be described with reference to FIGS. The general operation of the mobile phone is widely known and will not be described.

  When a key operation by the user is performed from the key operation unit 4 of the mobile phone (S1), the control unit 2 outputs image data designated by the key operation to the display unit 2. At that time, the control unit 2 determines the luminance distribution of the display screen by counting the appearance frequency of each luminance level for color information of image data for one screen output to the display unit 2, for example (S2). .

When the image data is centered on a character character as shown in FIG. 3, the background is usually information of a certain luminance level consisting of one color (white), and each character is usually one color (black, red, green, etc.). since a constant luminance level of information consisting of), for example, among the color information represented by the 2 ⁷ level, number of levels of each color information output to the display unit 2 (number of gradations) is small, the luminance distribution As shown in FIG. 4, the histogram of FIG. 4 is a signal in which about 10 or more brightness levels of data appear discretely.

  On the other hand, in the case of image data that changes continuously in color and has rich colors, such as photographs, WEB contents, and games shown in FIG. For each color information of G and B, the luminance level is a signal that is uniformly distributed over almost all levels. 4 and 6, the horizontal axis represents the luminance signal level, and the vertical axis represents the appearance frequency of each luminance signal level (gradation).

The control unit 2, for example, among the color information represented by the tone consisting of 2 ⁷ level, the number of gradations that have been used as the color information output to the display unit 2 is, for example, in the case of 2 to ⁴ Determines that the luminance is discrete (S3), and makes the luminance of the backlight 3 relatively dark (S4). On the other hand, if the number of gradations which are used as the color information output to the display unit 2 is, for example, greater than 2 ⁴ determines that the luminance distribution is uniform (S5), the backlight 3 The brightness is relatively increased (S6).

  Therefore, in the case of an image with many shade changes or colors such as a photograph, the backlight illumination is automatically brightened and a beautiful image with good appearance can be displayed, while the shade change is small. Alternatively, in the case of character data or the like with few colors, the backlight illumination is automatically switched to a brightness that allows the content to be read and controlled to suppress power consumption.

  Note that the determination of the number of gradations used as the color information output to the display unit 2 does not necessarily have to be performed for all the R, G, and B color information, but one of them, for example, R ( It is possible to identify whether the luminance level of one screen is uniform or discrete only by determining only the color information of (red). In addition, a threshold value is set for the number of appearances for each luminance level (for example, 10 times or more), and the number of luminance levels having an appearance frequency larger than the set threshold value is set as a determination target. By excluding the luminance level, it may be determined whether the luminance distribution is uniform or discrete.

In the above embodiment, the brightness distribution histogram is classified into two types, ie, discrete or uniform, and the two-level illumination control is performed. However, the brightness is switched to three or more levels. It can also be controlled. For example if each color information is represented by 2 ⁷ brightness levels, and relatively brighter luminance of the backlight 3 when the number of occurrences gradation (luminance level) is greater than 2 ⁶ appearance gradation When the number is 2 ⁶ to ^25, the luminance of the backlight 3 is set to a medium level, and when the number of appearing gradations is less than ²⁵ , the luminance of the backlight 3 is controlled to be relatively dark. good.

It is a block diagram which shows the structure of the mobile telephone which can apply this invention. It is a flowchart which shows the operation | movement which controls the brightness of the backlight in this embodiment. It is a figure for demonstrating the operation | movement which controls the brightness of the backlight in this embodiment. It is a figure for demonstrating the operation | movement which controls the brightness of the backlight in this embodiment. It is a figure for demonstrating the operation | movement which controls the brightness of the backlight in this embodiment. It is a figure for demonstrating the operation | movement which controls the brightness of the backlight in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radio | wireless part 2 Display part 3 Backlight 4 Key operation part 5 Microphone 6 Receiver 7 Control part 8 Storage part

Claims (7)

  When the color information of the display signal output to each dot constituting the liquid crystal display screen of the portable wireless terminal is analyzed, and the luminance level of the color information constituting one screen is uniformly distributed If the backlight of the liquid crystal display is relatively bright and the luminance level of the color information constituting one screen has a discrete distribution, the backlight of the liquid crystal display is relatively darkened. A backlight illumination control method for liquid crystal display in a portable wireless terminal. The color information is expressed by luminance levels of 2 ⁿ (n is a natural number) for each color of R (red), G (green), and B (blue). When the number of appearing gradations is larger than 2 ^m (m is a natural number smaller than n), it is determined that the luminance level of the color information has a uniform and continuous distribution, and appears in one screen image data. 2. The backlight illumination of the liquid crystal display in the portable wireless terminal according to claim 1, wherein when the number of gradations is 2 ^m or less, the luminance level of the color information is determined to have a discrete distribution. Control method.   The backlight of a liquid crystal display in a portable wireless terminal according to claim 2, wherein the color information to be analyzed is any one of R (red), G (green), and B (blue). Lighting control method.   2. The backlight illumination control method for a liquid crystal display in a portable wireless terminal according to claim 1, wherein the brightness of the backlight is switched to three or more levels according to a distribution state of luminance levels of the color information. A wireless unit that performs wireless communication with a base station, a liquid crystal display unit that displays image data such as characters such as mail, characters, and photographs, WEB content, and a backlight that illuminates the liquid crystal display unit, In a portable wireless terminal having a control unit that sends characters such as characters and image data such as photographs and web contents to the liquid crystal display unit and performs display control thereof,
The backlight is configured to be switchable in luminance.
The control unit includes a luminance distribution determining unit that determines a luminance distribution from color information of image data constituting one screen sent to the liquid crystal display unit, and the luminance level of the color information is continuously determined by the luminance distribution determining unit. When it is determined that there is a general distribution, the luminance of the backlight is switched to be relatively bright, and when the luminance level of the color information is determined to be a discrete distribution, the luminance of the backlight is relatively A portable radio terminal characterized by having backlight illumination control means for switching control so as to darken. The color information is expressed by luminance levels of 2 ⁿ (n is a natural number) for each of R (red), G (green), and B (blue), and the luminance distribution determining unit When the number of gradations appearing in one screen image data is greater than 2 ^m , it is determined that the luminance level of the color information has a continuous distribution, and the number of gradations appearing in one screen image data is 2 ^m. 6. The portable wireless terminal according to claim 5, further comprising a function of determining that the luminance level of the color information has a discrete distribution when (m is a natural number smaller than n) or less. 7. The luminance distribution determination unit has a function of performing the determination based on any one color information of R (red), G (green), and B (blue). The portable wireless terminal described in 1.

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