JP2004317895A - Signal processing method for image information and image information display device - Google Patents

Signal processing method for image information and image information display device Download PDF

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Publication number
JP2004317895A
JP2004317895A JP2003113568A JP2003113568A JP2004317895A JP 2004317895 A JP2004317895 A JP 2004317895A JP 2003113568 A JP2003113568 A JP 2003113568A JP 2003113568 A JP2003113568 A JP 2003113568A JP 2004317895 A JP2004317895 A JP 2004317895A
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JP
Japan
Prior art keywords
image information
auxiliary light
group
light source
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP2003113568A
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Japanese (ja)
Inventor
Shigeo Mikoshiba
Tomokazu Shiga
Makoto Yasuda
誠 安田
茂生 御子柴
智一 志賀
Original Assignee
Hitachi Lighting Ltd
日立ライティング株式会社
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Priority to JP2003113568A priority Critical patent/JP2004317895A/en
Publication of JP2004317895A publication Critical patent/JP2004317895A/en
Application status is Pending legal-status Critical

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Abstract

<P>PROBLEM TO BE SOLVED: To solve the serious problem of reducing the power consumption when the diagonal size of a liquid crystal TV or the like increases because the power consumption of a backlight increases in accordance with the increase of the diagonal size. <P>SOLUTION: In an image information display device provided with auxiliary light sources, auxiliary light sources are divided into a plurality of groups, and the light output of each group of auxiliary light sources is controlled in accordance with the signal of image information, and simultaneously, the signal intensity is calculated again in accordance with the light output of auxiliary light sources. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a signal processing method for image information that requires an auxiliary light source, and an image information display device that requires an auxiliary light source, such as a liquid crystal television that requires a backlight and a liquid crystal monitor for a personal computer.
[0002]
[Prior art]
As a conventional image information signal processing method, for example, the IEICE Technical Report, Vol. 99, No. 143, p. It is stated that it is shortened. Similarly, a method for improving the image quality without increasing the power consumption of the auxiliary light source is described in IEICE Technical Report, Vol. 101, No. 600, page 23 (2002). Are described, a combination of a blink backlight method of blinking the backlight at a time and a black display data insertion method.
[0003]
[Problems to be solved by the invention]
In a conventional liquid crystal television, as the diagonal size increases, the power consumption of the backlight becomes important. A 40-inch diagonal wide-screen LCD TV requires 800 cd / m 2 at peak luminance equivalent to that of a CRT. If the transmittance from the backlight of a liquid crystal module including a polarizer and a color filter is 4%, the backlight Requires a peak luminance of 20,000 cd / m 2 . At this time, if the efficiency of the lamp is 40 lm / W, the peak luminous flux is 28,000 lm, and the power consumption is 700 W. If further applying the blink backlight method or a black display data insertion method for a hold time 1/8 peak intensity of the lamp it must be increased in 160,000cd / m 2. When the black display data insertion method is applied, the power of the lamp becomes 5,600 W, which increases to an unrealistic value. However, the average level of ordinary television broadcast signals is about 25%, which means that the power consumption of the backlight can be reduced to this level. A first object of the present invention is to reduce power consumption by dimming the brightness of a backlight.
[0004]
A second object of the present invention is to enhance the display capability of gray gradation for a low-luminance image.
[0005]
[Means for Solving the Problems]
First, the principle for solving the above problem will be described. For the first object of the present invention, signal processing for dimming will be described. A backlight unit having 48 fluorescent lamps shown in FIG. 2 will be described as an example. The method can be applied to other backlight systems, for example, a system using LEDs. It is assumed that the lamps are divided into eight groups and dimmable inverters are prepared for each group. FIG. 3 is an example of the luminance distribution after passing through the diffuser when only group m is lit at full power. Vertical position of the center of intensity and the group of peaks (y) respectively L mmax, expressed as y m. The curve is L m (y) = L mmax × f (y−y m )
Is represented by Here, f (y) is a luminance distribution function. The luminance distribution function L b (y) when all the lamps are turned on is as follows.
L b (y) = Σ L mmax × f (y-y m),
Here, Σ is to calculate the sum of m = 1 to 8.
The principle of the improved dimming technique according to the present invention is illustrated in FIG. 4 where for simplicity there is only a single lamp in the backlight system. In the figure, L b (y) indicates the luminance of the backlight before performing the improved dimming, and s i (y n ) indicates the n-th horizontal scanning line before performing the improved dimming. This is the largest input signal of all pixels. The greatest signal s r (y n) of all pixels in the n-th horizontal scanning line after conversion is obtained by the following equation.
s r (y n ) = s i (y n ) × L bmin / L b (y n )
Here, Lbmin represents the minimum value of the luminance on the diffusion plate.
Maximum value s r (y n) max of s r (y n) of all pixels are less than or equal to the maximum limit s max of the signal output. Therefore L b (y n) must be converted by a factor k = s r (y n) max / s max. Then, the luminance L a (y) of the backlight after dimming becomes equal to kL b (y). At the same time signal s a after improved dimmer according to the invention (y n) changes to s r (y n) / k , s a (y n) max is equal to s max. Output s a from the liquid crystal television (y n) L a (y n) will be proportional to s i (y n).
[0006]
Next, the principle for achieving the second object of the present invention will be described. When the peak level of the video signal is 255 as shown in FIG. 1, when the backlight is fully lit, 256 gray levels can be displayed. However, if the peak level of the signal is 10, only 11 levels can be displayed. If the brightness of the backlight is adjusted by a coefficient of 256/11 = 23 and the original signal is interpolated so as to fit the 256 levels, the brightness can be increased to 256 gray levels. Dimming of the lamp is achieved, for example, by using pulse number modulation or duty factor modulation.
[0007]
Although the principle has been described in detail above, in order to solve the above problem, in the present invention, in an image information display device provided with an auxiliary light source, the auxiliary light sources are divided into a plurality of groups, and the auxiliary light sources are divided according to the signal strength of the image information. The light output is controlled for each group of light sources, and at the same time, the signal intensity is recalculated according to the light output of the auxiliary light source.
[0008]
Further, in the present invention, the signal processing is performed based on the luminance information immediately before from the auxiliary light source.
[0009]
Further, according to the present invention, when the signal strength is low, the gradation level is set finely in accordance with the low signal strength.
[0010]
Further, in the present invention, the image information display device is configured to include the above-described signal processing method.
[0011]
Further, according to the present invention, a fluorescent lamp is provided as an auxiliary light source.
[0012]
Further, in the present invention, a light emitting diode is provided as an auxiliary light source.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 5 is a flowchart showing a signal processing procedure according to the present invention. Here is not analytical methods, such as the previous section, in order to obtain a set of values k m, and using numerical methods. Here k m is a dimming factor of the lamp group m (percentage). A luminance distribution function f (y) is required as an initial value. In step # 2 of FIG. 5, a process provided for a lamp having a long (about 20 minutes) time constant to reach a saturation brightness level, for example, detecting the brightness of the lamp using a photodetector. is there. This slow change is dependent on the change in lamp temperature. It should be noted that if the temperature of the lamp falls below the critical value of about 60 ° C., the efficiency of the lamp containing mercury will decrease. This condition occurs when there is considerable (deep) dimming for a long period of time. Step equations # 6, the displayed image relationship indicates that no change even after the dimming process s a (y n) L a (y n) = s r (y n) L b ( obtained from y n).
In step # 8, the power consumption of the backlight after dimming is calculated so that it becomes minimum in step # 10. Step # 11 is added for blinking control and is not directly related to this dimming technique. Step # 15 is for signal interpolation as described in FIG. The above process is repeated, for example, every second.
Control of eight lamp groups requires a number of calculation steps. These steps can be reduced by, for example, the following method. (1) The calculation can be omitted where the change in brightness from the diffused light is negligible. (2) The calculation is started from the initial condition that the brightness of the lamp is equal to the average image level in each lamp group. ) s a (y n) to stop the calculation when it began to decrease.
[0014]
If the light leakage between adjacent lamp groups is not large, the signal processing process can be very simple, as described in the flowchart of FIG. Here, first, the dimming coefficient of the lamp luminance of each group is determined such that the lamp power is minimized ignoring the diffusion of light from other groups (steps # 1 to # 5). Then, L a (y) is calculated in consideration of diffusion of light from another group (step # 6). Step # 7 is for calculating the signal after performing the improved dimming of the present invention.
[0015]
The embodiment of the signal processing method according to the present invention has been described above. An embodiment of an image information display device such as a liquid crystal television is shown in FIG. In the figure, reference numeral 1 denotes a signal processing circuit. Reference numeral 2 denotes a flat fluorescent lamp, which is arranged in a row in the vertical direction to cover an entire display screen area. In the flat fluorescent lamp 2, for example, electrodes covered with a pair of dielectrics are arranged on opposite sides of a flat discharge space in which a discharge gas mainly composed of xenon is sealed, and a flat discharge is performed between the electrodes to generate a wide discharge. This is a light source that can emit light in an area and is suitable as a backlight of a liquid crystal television. Reference numeral 3 denotes an inverter for driving the flat fluorescent lamp, and there are eight inverters corresponding to the respective flat fluorescent lamps. Reference numeral 4 denotes a diffusion plate which is provided on the flat fluorescent lamp. On one side of the surface of the diffusion plate 4, a linear optical sensor 5 for measuring the luminance distribution in the vertical direction is installed. A liquid crystal module 6 is provided on the diffusion plate. Reference numeral 7 denotes a liquid crystal panel, and reference numerals 8 and 9 denote circuits for driving the liquid crystal panel 7 from signals in the vertical and horizontal directions, respectively. The operation of the image information display device of FIG. 9 is as follows. The luminance distribution on the diffusion plate 4 is detected by the optical sensor 5. The value of L max for each m and the video signal obtained from the detection result of the optical sensor are input to the signal processing circuit 1, and the signal processing shown in FIG. 5 is performed. As a result, a signal indicating the dimming ratio of the flat fluorescent lamp 2 is sent from the signal processing circuit 1 to the corresponding inverter 3 and the dimming is performed accordingly. Then, a signal is sent from the signal processing circuit 1 to the vertical driving circuit 8 and the horizontal driving circuit 9 of the liquid crystal module 6, and the signal is displayed.
[0016]
In the present embodiment, since the light output of the flat fluorescent lamp 2 is adjusted to a level at which sufficient luminance can be obtained by using a video signal from the outside, an image information display device having sufficient luminance with low power is used. Can be realized.
[0017]
The modification of this embodiment is easy. For example, the auxiliary light source is not limited to a flat fluorescent lamp, and may be a cold cathode fluorescent lamp, a fluorescent lamp of an external electrode type for high-frequency lighting, or a discharge gas containing mercury or a rare gas alone. Further, a solid-state light emitting device such as an LED, an inorganic EL, and an organic EL may be used.
[0018]
【The invention's effect】
6 shows the result of calculating the effect of the present invention in accordance with the flowchart of FIG. FIGS. 7A and 7B show the luminance distribution L b (y) and the original input signal s i (y n ) before applying the improved dimming of the present invention, respectively. After the addition of improved dimming of the present invention, the luminance distribution L a (y) and the signal s a (y n) it is also shown in FIG. 7, respectively and (c) (d). The optimal combination of the dimming coefficients may be [k] = (1.0, 0.7, 0.2, 0.2, 0.1, 0.1, 0.3, 0.1). I was found. Then, the power of the backlight was reduced to 34% before dimming.
FIG. 8 shows the result of calculating the same Lb (y) and s i (y n ) when m = 8 using FIG. 6 which is a simplified calculation method. The optimal combination of the dimming coefficients is [k] = (0.9, 0.9, 0.4, 0.3, 0.2, 0.2, 0.3, 0.3) Power was reduced to 44%. When m = 48, when the same s i (y n ) was used using the simplified calculation method, the power reduction was 37%. This results in a greater power reduction compared to the method of FIG. 8, but this method requires 48 inverters instead of eight.
[0019]
ADVANTAGE OF THE INVENTION According to this invention, even if an image display apparatus becomes large, the power consumption of a backlight can be reduced. In the case of an image with a low luminance signal, more detailed gradation display can be performed by interpolating the signal.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating the principle of the present invention.
FIG. 2 is a diagram illustrating the principle of the present invention.
FIG. 3 is a diagram illustrating the principle of the present invention.
FIG. 4 is a diagram illustrating the principle of the present invention.
FIG. 5 is a flowchart illustrating a signal processing method according to the present invention.
FIG. 6 is a flowchart illustrating another signal processing method according to the present invention.
FIG. 7 is a diagram showing one embodiment of a signal processing method according to the present invention.
FIG. 8 is a diagram showing another embodiment of the signal processing method according to the present invention.
FIG. 9 is a diagram showing an embodiment of an image information display device according to the present invention.
[Explanation of symbols]
Lb : luminance distribution when all lamps are turned on before dimming,
s i : distribution of the largest input signal in horizontal scanning lines before dimming,
s r : distribution of the largest signal in the horizontal scanning line in consideration of the luminance distribution of the auxiliary light source,
L a: after dimming, brightness distribution when all lamps are lit,
s a: tone after light, the distribution of the largest signal among the horizontal scanning lines,
k m: dimming factor of lamp group m (percentage),
1: signal processing circuit, 2: flat fluorescent lamp, 3: inverter,
4: diffusion plate, 5: optical sensor, 6: liquid crystal module, 7: liquid crystal panel,
8: vertical driving circuit, 9: horizontal driving circuit.

Claims (10)

  1. In an image information display device provided with an auxiliary light source, the auxiliary light sources are divided into a plurality of groups, and the light output is controlled for each group of the auxiliary light sources according to the signal intensity of the image information. A signal processing method for image information, wherein the image information is re-calculated accordingly and the image information is displayed based on the re-calculated signal strength.
  2. The signal processing method for image information according to claim 1,
    s i (y n) distribution of the maximum signal for each horizontal scan line of the input signal, the maximum value of the luminance distribution of the group m of the auxiliary light source L mmax, the luminance distribution of L mmax f (y-y m ) a group m , L b (y n) of the luminance distribution when all groups lit, the L bmin is the minimum value of L b,
    [K] a set of dimming ratio k m of the group m when (k 1, k 2, ··· , k m, ···) and,
    s r (y n ) = s i (y n ) × L bmin / L b (y n ),
    L a (y) = Σk m L mmax f (y-y m),
    s a (y n) = s r (y n) L b (y n) / L a (y n),
    Is calculated, and the auxiliary light is set using a set [k] of dimming ratios when s a (y n ) is smaller than the maximum value s max in the input signals of all pixels and the total power consumption of the auxiliary light source is minimum. Control the light output of the light source,
    Signal processing method of the image information and obtaining from the signal intensities of all pixels s a (y n).
  3. The signal processing method for image information according to claim 1,
    s i (y n) distribution of the maximum signal for each horizontal scan line of the input signal, the maximum value of the luminance distribution of the group m of the auxiliary light source L mmax, the luminance distribution of L mmax f (y-y m ) a group m , L b (y n) of the luminance distribution when all groups lit, the L bmin is the minimum value of L b,
    s r (y n ) = s i (y n ) × L bmin / L b (y n ),
    The dimming ratio k m of each group m, determined from the maximum value of s r (y n) in the group m, the total power consumption of the auxiliary light source controls the optical output of the auxiliary light source so as to minimize , L a (y) = Σk m L mmax f (y-y m),
    s a (y n) = s r (y n) L b (y n) / L a (y n),
    And calculating the signal intensities of all the pixels from s a (y n ).
  4. 4. A signal processing method for image information according to claim 1, wherein said signal processing is performed by measuring a light output of each auxiliary light source group at substantially constant time intervals. .
  5. In the signal processing method for image information according to any one of claims 1 to 4, the maximum luminance in each group of the auxiliary light sources is higher than the maximum signal level or the original input signal level according to the dimming ratio. A signal processing method for image information, wherein the calculation is performed by interpolating the signal intensities of all pixels.
  6. In an image information display device provided with an auxiliary light source,
    6. The at least one signal processing device according to claim 1, wherein the auxiliary light source is divided into a plurality of groups, each group including at least one dimmable power supply, and a unit that controls light output for each group. An image information display device comprising a method.
  7. The image information display device according to claim 6,
    An image information display device comprising: means for detecting a light output for each group of auxiliary light sources.
  8. 8. The image information display device according to claim 6, further comprising a fluorescent lamp as an auxiliary light source.
  9. 8. The image information display device according to claim 6, further comprising a light emitting diode as an auxiliary light source.
  10. 8. The image information display device according to claim 6, further comprising an EL as an auxiliary light source.
JP2003113568A 2003-04-18 2003-04-18 Signal processing method for image information and image information display device Pending JP2004317895A (en)

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007183499A (en) * 2006-01-10 2007-07-19 Sony Corp Display device and display method
JP2008102499A (en) * 2006-09-20 2008-05-01 Seiko Epson Corp Image display device and method
JP2008514969A (en) * 2004-08-31 2008-05-08 エヌヴィディア コーポレイション LCD backlight with variable brightness
WO2008099319A1 (en) * 2007-02-16 2008-08-21 Koninklijke Philips Electronics N.V. 2d-dimming of illuminating member for display device
JP2009288793A (en) * 2009-06-08 2009-12-10 Toshiba Corp Liquid crystal display
JP2010054839A (en) * 2008-08-28 2010-03-11 Toshiba Corp Information processing apparatus, image display device and method
EP2398016A1 (en) * 2005-01-25 2011-12-21 Sharp Kabushiki Kaisha Display device, instrument panel, automatic vehicle, and method of driving display device
US8159451B2 (en) 2008-05-26 2012-04-17 Kabushiki Kaisha Toshiba Light-emission control device and liquid crystal display apparatus
JP2014146034A (en) * 2014-02-26 2014-08-14 Dolby Lab Licensing Corp Plurality of modulator displays and related method

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JPH11109317A (en) * 1997-09-30 1999-04-23 Sony Corp Liquid crystal display device
JP2000294026A (en) * 1999-04-09 2000-10-20 Matsushita Electric Ind Co Ltd Backlight device
JP2000321571A (en) * 1999-05-10 2000-11-24 Nec Viewtechnology Ltd Liquid crystal display device and backlight luminances adjusting method
JP2002099250A (en) * 2000-09-21 2002-04-05 Toshiba Corp Display device

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Publication number Priority date Publication date Assignee Title
JPH11109317A (en) * 1997-09-30 1999-04-23 Sony Corp Liquid crystal display device
JP2000294026A (en) * 1999-04-09 2000-10-20 Matsushita Electric Ind Co Ltd Backlight device
JP2000321571A (en) * 1999-05-10 2000-11-24 Nec Viewtechnology Ltd Liquid crystal display device and backlight luminances adjusting method
JP2002099250A (en) * 2000-09-21 2002-04-05 Toshiba Corp Display device

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008514969A (en) * 2004-08-31 2008-05-08 エヌヴィディア コーポレイション LCD backlight with variable brightness
EP2398016A1 (en) * 2005-01-25 2011-12-21 Sharp Kabushiki Kaisha Display device, instrument panel, automatic vehicle, and method of driving display device
JP2007183499A (en) * 2006-01-10 2007-07-19 Sony Corp Display device and display method
JP2008102499A (en) * 2006-09-20 2008-05-01 Seiko Epson Corp Image display device and method
US8674926B2 (en) 2006-09-20 2014-03-18 Seiko Epson Corporation Image display device and image display method using black display
WO2008099319A1 (en) * 2007-02-16 2008-08-21 Koninklijke Philips Electronics N.V. 2d-dimming of illuminating member for display device
US8159451B2 (en) 2008-05-26 2012-04-17 Kabushiki Kaisha Toshiba Light-emission control device and liquid crystal display apparatus
JP2010054839A (en) * 2008-08-28 2010-03-11 Toshiba Corp Information processing apparatus, image display device and method
JP2009288793A (en) * 2009-06-08 2009-12-10 Toshiba Corp Liquid crystal display
JP2014146034A (en) * 2014-02-26 2014-08-14 Dolby Lab Licensing Corp Plurality of modulator displays and related method

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