CN101673520A - Liquid crystal display (LCD) device and image signal processing method - Google Patents
Liquid crystal display (LCD) device and image signal processing method Download PDFInfo
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Abstract
The invention discloses a liquid crystal display (LCD) device and an image signal processing method applied to the LCD device. The LCD device comprises a decoding module, a dynamic backlight control module, a time sequence control module, a liquid crystal driving module, an LCD panel, a backlight driving module and an LED backlight module, wherein the dynamic backlight control module is connectedwith the decoding module and is used for receiving an image RGB grey scale signal, carrying out gamma correction on the RGB grey scale signal and statistics on the average value and the standard deviation, calculating to obtain the backlight adjusted value, calculating a backlight brightness signal according to the reference brightness value which is preset or input by a user, and outputting the backlight brightness signal to the backlight driving module to drive the LED backlight module to lighten the LCD panel. The invention also discloses the corresponding image signal processing method. The device and the method can effectively reduce the power consumption, increases the contrast, avoids the situation of ultra-low backlight brightness when the image is monochrome image with less standard deviation, and improves the display effect.
Description
Technical Field
The present invention relates to the field of liquid crystal display, and more particularly, to a liquid crystal display device and a method for processing an image signal applied to the liquid crystal display device.
Background
Liquid Crystal Displays (LCDs) are being used in various fields of production and living gradually due to their advantages of small size, light weight, and the like. Since the LCD is a passive display and does not emit light, the LCD requires a backlight unit as its light source to display images by means of transmitted light.
Conventional LCD display devices have two significant drawbacks: first, the power consumption is high. In electronic products using LCDs, the energy consumption of the LCD accounts for 30% to 70% of the total energy consumption, and the backlight of the LCD is the most power consuming part of the LCD. Second, the contrast is insufficient. Since the backlight is always fully bright and the LCD cannot turn off the unwanted light completely, even a black image does not appear sufficiently black, thereby causing a problem of reduced image contrast.
In order to solve the above problems, a full screen dynamic backlight technology using LEDs as a backlight source is proposed. One method of determining the dynamic backlight is to use the luminance maximum of the input image, but this method of using the maximum has problems of small power consumption saving and being too sensitive to noise. Another common method for determining dynamic backlight is to use the average brightness of the input image, but this method has the problem that the backlight brightness is too low and the image details are lost when processing a dark image.
In US20080291153 of hong kong applied science and technology research institute, a method of calculating the average and variance of brightness of an image by using a histogram of the image and obtaining a backlight adjustment value from the average and variance of brightness is proposed, but it has a problem that the brightness of a monochrome image backlight is too low, for example, the backlight brightness of a blue image calculated by this method is only 0.4, and when the image is displayed on an LCD, the phenomenon of too dark image is obvious.
Accordingly, the prior art is deficient and needs improvement.
Disclosure of Invention
The present invention provides a liquid crystal display device, and further provides a liquid crystal display device using an LED as a backlight source, wherein the luminance of the LED backlight can be dynamically adjusted according to the change of the liquid crystal display content, and a method for processing digital image signals in the liquid crystal display device, which is used in a direct-type or edge-type backlight liquid crystal display device.
The technical scheme of the invention is as follows:
a liquid crystal display device comprises a decoding module, a time sequence control module, a liquid crystal driving module, a backlight driving module, a liquid crystal panel, an LED backlight module and a dynamic backlight control module; the dynamic backlight control module is connected with the decoding module and used for receiving image RGB gray signals, carrying out gamma correction on the RGB gray signals, counting the average value and the standard deviation of the RGB gray signals, calculating a backlight adjusting value, calculating a backlight brightness signal according to a preset or input reference brightness value, and outputting the backlight brightness signal to the backlight driving module; the backlight driving module is connected with the LED backlight module and used for driving the LED backlight module according to the backlight brightness signal to illuminate the liquid crystal panel.
The liquid crystal display device, wherein the dynamic backlight control module and the decoding module are integrally arranged.
The liquid crystal display device, wherein the dynamic backlight control module comprises an image signal receiving unit, a searching unit, a statistical unit, a calculating unit and a backlight control unit which are connected in sequence; the image signal receiving unit is used for receiving R, G, B gray scale signals in the image signals and sending the signals to the searching unit; the searching unit is used for converting R, G, B gray signals into signals R ', G ' and B ' after gamma correction and sending the signals to the statistical unit; the statistical unit is used for respectively counting the average value and the standard deviation of the signals R ', G ' and B ' and sending the average value and the standard deviation to the calculating unit; the calculation unit is used for calculating to obtain a backlight adjustment value T according to each average value and each standard deviation and sending the backlight adjustment value T to the backlight control unit; the backlight control unit is also connected with the backlight driving module and used for obtaining a backlight brightness signal BL according to the backlight adjustment value T and a preset reference brightness value S and sending the backlight brightness signal BL to the backlight driving module.
The liquid crystal display device, wherein the dynamic backlight control module further comprises a user input unit, connected to the backlight control unit, for presetting a reference brightness value S and sending the preset reference brightness value S to the backlight control unit; and the backlight control unit is used for obtaining a backlight brightness signal BL according to the backlight adjustment value T and the input reference brightness value S and sending the backlight brightness signal BL to the backlight driving module.
In the liquid crystal display device, the statistical unit is provided with a histogram subunit for respectively counting histograms of the image signals R ', G', and B ', and the average value and the standard deviation of R', G ', and B' are calculated through the histograms.
In the liquid crystal display device, the calculating unit is provided with a linear combination subunit, a judging subunit, a calculating subunit and a user input subunit; the linear combination subunit is used for calculating signals R ', G'The maximum X of the linear combination of the mean and standard deviation of B'; wherein, the linear combination of any signal is the sum of the standard deviation multiplied by a preset coefficient and the average value thereof; and, the preset coefficient is more than 0 and less than or equal to 1; the judgment subunit is configured to judge whether the maximum value X is greater than 255, set T equal to 1 if the maximum value X is greater than 255, and otherwise, start the calculation subunit; the calculation subunit is used for adopting a formula T ═ 1-Tmin)X/255+TminCalculating the backlight adjustment value T; wherein, TminT is more than or equal to 0.5 and is a preset parameterminLess than or equal to 0.9; the user input subunit is used for inputting the preset coefficient and/or the preset parameter.
In the liquid crystal display device, the user input subunit may be provided together with the user input unit.
An image signal processing method applied to any one of the above liquid crystal display devices includes the steps of: a1, receiving an image signal R, G, B; a2, converting the image signal R, G, B into signals R ', G ', and B ' by gamma correction; a3, calculating the average value and standard deviation of R ', G ' and B ' respectively; a4, calculating a backlight adjustment value T according to each average value and each standard deviation; and A5, obtaining a backlight brightness signal BL according to the backlight adjustment value T and a preset or input brightness reference value S, sending the backlight brightness signal BL to a backlight driving module, driving the LED backlight module, and illuminating the liquid crystal panel.
In the image signal processing method, any one of the steps a1 to a5 is preceded by the following step a0, wherein the brightness reference value S is preset or input.
The image signal processing method, wherein the step a1 further includes the step a11 of buffering the image signal.
In the image signal processing method, in step a3, the mean values and standard deviations of R ', G', and B 'are calculated by counting the histograms of R', G ', and B', respectively.
The image signal processing method, whereinA4 specifically executes the following steps: a41, calculating the maximum value X of the linear combination of the mean and standard deviation of the signals R ', G ', B '; wherein, the linear combination of any signal is the sum of the standard deviation multiplied by a preset coefficient and the average value thereof; and, the preset coefficient is more than 0 and less than or equal to 1; a42, judging whether the maximum value X is larger than 255, if so, setting T to 1, otherwise, executing a step a 43; a43, using formula T ═ 1-Tmin)X/255+TminCalculating the backlight adjustment value T; wherein, TminT is more than or equal to 0.5 and is a preset parametermin≤0.9。
The image signal processing method, wherein, before the step a41, the step a40 of inputting the preset coefficient and/or the preset parameter is further performed
The image signal processing method, wherein the step a5 further includes the following step a51 of buffering the backlight luminance signal BL.
In the image signal processing method, in step a5, the backlight luminance signal BL is a product of the reference luminance value S and the backlight adjustment value T.
By adopting the scheme, the invention adopts a full-screen dynamic backlight adjustment method, and adjusts the brightness of the backlight source according to the image to be displayed, so that the backlight brightness can move along with the image, thereby greatly reducing the power consumption and improving the contrast of the image displayed by the LCD.
Furthermore, for an image with a smaller average brightness value or a monochrome image with a smaller standard deviation, an ideal adjustment value can be obtained through reasonable parameter control, and the situation that the backlight brightness is too low is avoided, so that a better display effect is obtained. The defects in the prior art are overcome.
Drawings
FIG. 1 is a schematic diagram of the prior art;
FIG. 2 is a schematic structural view of embodiment 1 of the present invention;
FIG. 3 is a schematic structural view of embodiment 2 of the present invention;
FIG. 4 is a flow chart of an image signal processing method of the present invention;
fig. 5 is a histogram obtained by image signal processing of the present invention.
Detailed Description
The invention is described in detail below with reference to the figures and the specific embodiments.
Example 1
As shown in fig. 1 and fig. 2, the present embodiment provides a liquid crystal display device, which includes a decoding module 90, a dynamic backlight control module 100, a timing control module (also referred to as a T-CON board) 110, a liquid crystal driving module 120, a liquid crystal panel 130, a backlight driving module 140, and an LED backlight module 150, where the connection relationships and functions of the decoding module 90, the timing control module 110, the liquid crystal driving module 120, the backlight driving module 140, the liquid crystal panel 130, and the LED backlight module 150 belong to the prior art, and as shown in fig. 1, are not repeated herein. The following focuses on the dynamic backlight control module 100.
As shown in fig. 2, the dynamic backlight control module 100 is connected to the decoding module 90, but in order to reduce the cost, the dynamic backlight control module 100 may be integrated into the decoding module 90, as shown in the dashed line frame in fig. 2, that is, for one example, the dynamic backlight control module 100 is integrally provided with the decoding module 90.
The decoding module 90 is configured to receive an image signal, which may include signals such as VGA, HDMI, AV, and CABLE according to various interface types, perform certain processing on the image, such as motion compensation and scaling, and then transmit the processed image signal to the dynamic backlight control module 100 in a corresponding interface form, such as an FPD-Link interface form. The dynamic backlight control module 100 is configured to receive the image signal processed by the decoding module, dynamically analyze the digital image signal in a full screen manner, and dynamically adjust backlight brightness data according to an analysis result. For example, the dynamic backlight control module is connected to the decoding module, receives RGB gray signals of an image, performs gamma correction on the RGB gray signals, counts the average value and standard deviation of the RGB gray signals, calculates a backlight adjustment value, calculates a backlight luminance signal according to a preset or input reference luminance value, and outputs the backlight luminance signal to the backlight driving module; the backlight driving module is connected with the LED backlight module and used for driving the LED backlight module according to the backlight brightness signal, namely backlight brightness data, so as to illuminate the liquid crystal panel. It should be noted that the method for dynamically adjusting the backlight brightness may be calculated by any algorithm known to the skilled person. The dynamic backlight control module 100 outputs backlight luminance data and liquid crystal gray scale data to the backlight driving module 140 and the timing control module 110, and the timing control module 110 is connected to the liquid crystal driving module 120, and is configured to generate a corresponding timing control signal according to the liquid crystal gray scale data, and transmit the timing control signal to the liquid crystal driving module 120, so as to drive the liquid crystal panel 130. The backlight driving module 140 is connected to the LED backlight module 150, and is used for driving the LED backlight module 150 according to the backlight brightness data to illuminate the liquid crystal panel 130.
Example 2
On the basis of the above example, the present embodiment provides a liquid crystal display device, as shown in fig. 3, the dynamic backlight control module 100 includes an image signal receiving unit 101, a searching unit 102, a counting unit 103, a calculating unit 104, and a backlight control unit 106, which are connected in sequence.
The image signal receiving unit 101 is connected to the searching unit 102, and is configured to receive R, G, B grayscale signals in the image signal of one frame of video and send the signals to the searching unit 102. The search unit 102 is connected to the image signal receiving unit 101 and the statistic unit 103, respectively, converts the R, G, B grayscale signal into signals R ', G', and B 'after γ correction, and sends the signals R', G ', and B' to the statistic unit 103.
The statistical unit 103 is connected to the searching unit 102 and the calculating unit 104, respectively, and is configured to calculate an average value and a standard deviation of the signals R ', G ', and B ', respectively, and send each average value and each standard deviation to the calculating unit 104.
The calculation unit 104 is connected to the statistics unit 103 and the backlight control unit 106, respectively, calculates a backlight adjustment value T, and sends the backlight adjustment value T to the backlight control unit 106.
The backlight control unit 106 is respectively connected to the computing unit 104 and the backlight driving module 140, and is configured to receive the backlight adjustment value T input by the computing unit 104, obtain a backlight brightness signal BL according to a preset reference brightness value S, and send the backlight brightness signal BL to the backlight driving module 140. The backlight driving module 140 is respectively connected to the backlight control unit 106 and the LED backlight module 150, and receives the backlight luminance signal BL to drive the LED backlight module 150 to illuminate the liquid crystal panel 130.
Or, for example, the dynamic backlight control module 100 may further include a user input unit 105. The user input unit 105 is connected to the backlight control unit 106 for inputting a reference luminance value S thereto. The user may change the base luminance value at any operating time of the display device, or the reference luminance value may be input from the decoding board at any operating time of the display device.
In this way, the backlight control unit 106 is respectively connected to the computing unit 104, the user input unit 105 and the backlight driving module 140, and is configured to receive the backlight adjustment value T input by the computing unit 104 and the reference brightness value S input by the user input unit, obtain a backlight brightness signal BL, and send the backlight brightness signal BL to the backlight driving module 140. The backlight driving module 140 is respectively connected to the backlight control unit 106 and the LED backlight module 150, and receives the backlight luminance signal BL to drive the LED backlight module 150 to illuminate the liquid crystal panel 130.
As another example, the statistical unit is configured with a histogram subunit for respectively counting histograms of the image signals R ', G', and B ', and calculating the mean and standard deviation of R', G ', and B' through the respective histograms. The method of histogram statistics may be a useful addition to the examples described above.
As another example, on the basis of the above embodiments, the calculating unit is provided with a linear combination subunit, a judgment subunit, a calculating subunit, and a user input subunit; the linear combination subunit is used for calculating the maximum value X of the linear combination of the average value and the standard deviation of the signals R ', G ' and B '; wherein, the linear combination of any signal is the sum of the standard deviation multiplied by a preset coefficient and the average value thereof; and, the preset coefficient is more than 0 and less than or equal to 1; the judgment subunit is configured to judge whether the maximum value X is greater than 255, set T equal to 1 if the maximum value X is greater than 255, and otherwise, start the calculation subunit; the calculation subunit is used for adopting a formula T ═ 1-Tmin)X/255+TminCalculating the backlight adjustment value T; wherein, TminT is more than or equal to 0.5 and is a preset parameterminLess than or equal to 0.9; the user input subunit is used for inputting the preset coefficient and/or the preset parameter. The user input subunit can input the preset coefficient and the preset parameter simultaneously; only the preset coefficient or the preset parameter can be input; a storage subunit may also be provided for storing each average value, each standard deviation, the maximum value X, the numerical value 255, a preset coefficient, a preset parameter, and the like, so that other subunits may call these data.
For example, when there is a user input unit, the user input subunit may be provided together with the user input unit.
Example 3
The present embodiment provides an image signal processing method, which is applied to any one of the liquid crystal display devices described above, and includes the following steps.
A1, receiving an image signal R, G, B; for example, step a1 further includes the following step a11, buffering the image signal.
A2, converting the image signal R, G, B into signals R ', G ', and B ' by gamma correction;
a3, calculating the average value and standard deviation of R ', G ' and B ' respectively; for example, the mean and standard deviation of R ', G', and B 'are calculated by counting the histograms of R', G ', and B', respectively.
And A4, calculating the backlight adjusting value T according to each average value and each standard deviation.
For example, step a4 specifically executes the following steps:
a41, calculating the maximum value X of the linear combination of the mean and standard deviation of the signals R ', G ', B '; wherein, the linear combination of any signal is the sum of the standard deviation multiplied by a preset coefficient and the average value thereof; and, the preset coefficient is more than 0 and less than or equal to 1;
a42, judging whether the maximum value X is larger than 255, if so, setting T to 1, otherwise, executing a step a 43;
a43, using formula T ═ 1-Tmin)X/255+TminCalculating the backlight adjustment value T; wherein, TminT is more than or equal to 0.5 and is a preset parametermin≤0.9。
As another example, before step a41, step a40 is further performed, and the preset coefficient and/or the preset parameter are input.
And A5, obtaining a backlight brightness signal BL according to the backlight adjustment value T and a preset or input brightness reference value S, sending the backlight brightness signal BL to a backlight driving module, driving the LED backlight module, and illuminating the liquid crystal panel. For example, the backlight luminance signal BL is a product of the reference luminance value S and the backlight adjustment value T. For another example, step a5 further includes the following step a51, buffering the backlight brightness signal BL.
For example, for any one of the steps a1 to a5, the following step a0, presetting or inputting a luminance reference value S, may also be performed before the step is performed. The user may change the base luminance value at any operating time of the display device, or the reference luminance value may be input from the decoding board at any operating time of the display device.
Example 4
The present embodiment provides a method for processing image signals, which is applied to the liquid crystal display devices of the above embodiments, and with reference to fig. 2 and 4, the method includes the following steps.
A1, the image signal receiving unit 101 receives R, G, B gray scale signals and sends the gray scale signals to the searching unit 102; for example, step a1 further includes the step a11 of the image signal receiving unit 101 buffering the image signal, thereby synchronizing the output of the image signal with the output of the backlight adjustment value.
A2, the search unit 102 converts the gray signal R, G, B into signals R ', G', B 'by γ correction, and sends the signals R', G ', B' to the statistic unit 103, which has the calculation formula:
R’＝Rγformula (1)
G’＝GγFormula (2)
B’＝BγFormula (3)
Wherein the gamma values for gamma correction of R, G, B can be different, and the value range is [2, 3], i.e. 2 ≦ gamma ≦ 3, for example, the gamma values for gamma correction of R, G, B are 2.1, 2.2, 2.25, respectively.
A3 and a statistical unit 103 calculate the average value and standard deviation of the signals R ', G' and B ', which are respectively marked as R'avg，G’avg，B’avgAnd R'std，G’std，B’std. Next, the statistical unit 103 sends the calculated average value and standard deviation to the calculation unit 104.
Suppose that a frame of picture has N pixels, which are numbered 1, 21’、G1’、B1’；R2’、G2’、B2’；.....RN’、GN’、BN', then
R’avg＝(R1’+R2’+......RN')/N equation (4)
G’avg＝(G1’+G2’+......GN')/N equation (5)
B’avg＝(B1’+B2’+......BN')/N formula (6)
A4, the calculation unit 104 calculates the backlight adjustment value T and sends the backlight adjustment value T to the backlight control unit 106. In the calculation unit, first the maximum value of the linear combination of the mean and standard deviation of the signals R ', G ', B ', noted X, is calculated, i.e.
X＝Max(R’avg+a0*R’std；G’avg+a0*G’std；B’avg+a0*B’std)
Wherein the value range of a0 is (0, 1), namely, a0 is more than 0 and less than or equal to 1.
Secondly, a brightness adjustment value T is calculated according to X, and the formula is as follows:
T＝(1-Tmin)X/255+Tminformula (10)
Wherein T isminIs a pre-specified parameter with a numerical range of [0.5, 0.9 ]]I.e. 0.5. ltoreq. TminLess than or equal to 0.9. When the value of X is larger than 255, the value of T is fixed to 1.
As can be seen from the above formula, when a black image is displayed, that is, when the gray scale of each pixel point is 0, X is 0, and formula (10) is substituted, T is TminThe brightness value during the black screen is reduced to the maximum extent, so that the screen is dark enough, and the contrast is improved.
When the image has a small standard deviationWhen monochrome image, by reasonably presetting parameter TminThe situation that the backlight brightness is too low can be avoided.
A5, the backlight control unit 106 calculates the backlight brightness signal BL according to the backlight adjustment value T, and the preset reference brightness value S or the reference brightness value S input by the user:
BL is S X T formula (11)
The backlight control unit 106 sends the backlight luminance signal BL to the backlight driving module 140, and drives the LED backlight module 150 to emit a backlight with a specified luminance, so as to illuminate the liquid crystal panel 130.
For example, the step a5 further includes a step a51 in which the backlight driving module 140 buffers the backlight luminance signal BL, thereby synchronizing the output of the image signal with the output of the backlight adjustment value.
For example, in any of the image signal processing methods described above, step a0 is further performed before any of steps a1 through a5, and the user input unit 105 presets the luminance reference value S. The user input unit sends S to the backlight control unit 106 for calculating the backlight brightness signal BL.
Example 5
In addition to embodiment 4, in step a3, the statistical unit respectively calculates the histograms of signals R ', G', and B 'by the histogram subunit, and calculates the mean and standard deviation of signals R', G ', and B' by the histograms as shown in fig. 3.
Wherein, it is assumed that the number of times of the i-th level gray levels of R ', G ', B ' corresponding to the gray levels of 0 to 255 appear is N, respectivelyRi，NGi，NBiThen, the average value:
Calculate outR’avg，G’avg，B’avgAnd R'std，G’std，B’stdThen, the operations are sequentially performed according to the steps a4, a5 and a6 in embodiment 3 until a backlight luminance signal BL is obtained, and the backlight luminance signal BL is output to the backlight driving module 140 to drive the LED backlight module 150 to illuminate the liquid crystal panel 130. And will not be described in detail herein.
By performing the full-screen dynamic backlight processing on the image signal, the method remarkably reduces power consumption and improves contrast. In addition, the luminance average value and the standard deviation of the image are simultaneously considered when calculating the backlight luminance. Since the brightness mean and the standard deviation are statistics, even if there is noise on the image, the backlight adjustment value obtained by the final calculation is not affected. For an image with a small luminance average value and standard deviation, the parameter T in equation (10) is controlledminAn ideal adjustment value can be obtained, and the situation that the backlight brightness is too low can not occur.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
Claims (10)
1. A liquid crystal display device comprises a decoding module, a time sequence control module, a liquid crystal driving module, a backlight driving module, a liquid crystal panel and an LED backlight module, and is characterized by also comprising a dynamic backlight control module;
the dynamic backlight control module is connected with the decoding module and used for receiving image RGB gray signals, carrying out gamma correction on the RGB gray signals, counting the average value and the standard deviation of the RGB gray signals, calculating a backlight adjusting value, calculating a backlight brightness signal according to a preset or input reference brightness value, and outputting the backlight brightness signal to the backlight driving module;
the backlight driving module is connected with the LED backlight module and used for driving the LED backlight module according to the backlight brightness signal to illuminate the liquid crystal panel.
2. The liquid crystal display device of claim 1, wherein the dynamic backlight control module is integrated with the decoding module; or, the dynamic backlight control module comprises an image signal receiving unit, a searching unit, a counting unit, a calculating unit and a backlight control unit which are connected in sequence; wherein,
the image signal receiving unit is used for receiving R, G, B gray scale signals in the image signals and sending the signals to the searching unit;
the searching unit is used for converting R, G, B gray signals into signals R ', G ' and B ' after gamma correction and sending the signals to the statistical unit;
the statistical unit is used for respectively counting the average value and the standard deviation of the signals R ', G ' and B ' and sending the average value and the standard deviation to the calculating unit;
the calculation unit is used for calculating to obtain a backlight adjustment value T according to each average value and each standard deviation and sending the backlight adjustment value T to the backlight control unit;
the backlight control unit is also connected with the backlight driving module and used for obtaining a backlight brightness signal BL according to the backlight adjustment value T and a preset reference brightness value S and sending the backlight brightness signal BL to the backlight driving module.
3. The LCD device of claim 2, wherein the dynamic backlight control module further comprises a user input unit connected to the backlight control unit for presetting a reference brightness value S to be sent to the backlight control unit;
and the backlight control unit is used for obtaining a backlight brightness signal BL according to the backlight adjustment value T and the input reference brightness value S and sending the backlight brightness signal BL to the backlight driving module.
4. The liquid crystal display device according to claim 2, wherein the statistical unit is provided with a histogram subunit for separately counting histograms of the image signals R ', G', B ', and calculating the mean value and standard deviation of R', G ', B' from the respective histograms; or,
the computing unit is provided with a linear combination subunit, a judgment subunit, a computing subunit and a user input subunit;
the linear combination subunit is used for calculating the maximum value X of the linear combination of the average value and the standard deviation of the signals R ', G ' and B '; wherein, the linear combination of any signal is the sum of the standard deviation multiplied by a preset coefficient and the average value thereof; and, the preset coefficient is more than 0 and less than or equal to 1;
the judgment subunit is configured to judge whether the maximum value X is greater than 255, set T equal to 1 if the maximum value X is greater than 255, and otherwise, start the calculation subunit;
the calculation subunit is used for adopting a formula T ═ 1-Tmin)X/255+TminCalculating the backlight adjustment value T; wherein, TminT is more than or equal to 0.5 and is a preset parametermin≤0.9；
The user input subunit is used for inputting the preset coefficient and/or the preset parameter.
5. An image signal processing method applied to the liquid crystal display device according to any one of claims 1 to 4, comprising the steps of:
a1, receiving an image signal R, G, B; for example, step a1 further includes the following steps a11, buffering the image signal;
a2, converting the image signal R, G, B into signals R ', G ', and B ' by gamma correction;
a3, calculating the average value and standard deviation of the signals R ', G ' and B ', respectively;
a4, calculating a backlight adjustment value T according to each average value and each standard deviation;
and A5, obtaining a backlight brightness signal BL according to the backlight adjustment value T and a preset or input brightness reference value S, sending the backlight brightness signal BL to a backlight driving module, driving the LED backlight module, and illuminating the liquid crystal panel.
6. The image signal processing method according to claim 5, wherein in the steps A1 to A5, the following step A0, presetting or inputting a brightness reference value S, is further performed before any step.
7. The image signal processing method according to claim 5, wherein in step A3, the mean values and standard deviations of R ', G', B 'are calculated by counting the histograms of R', G ', B', respectively.
8. The image signal processing method according to claim 5, wherein the step A4 specifically executes the steps of:
a41, calculating the maximum value X of the linear combination of the mean and standard deviation of the signals R ', G ', B '; wherein, the linear combination of any signal is the sum of the standard deviation multiplied by a preset coefficient and the average value thereof; and, the preset coefficient is more than 0 and less than or equal to 1;
a42, judging whether the maximum value X is larger than 255, if so, setting T to 1, otherwise, executing a step a 43;
a43, using formula T ═ 1-Tmin)X/255+TminCalculating the backlight adjustment value T; wherein, TminT is more than or equal to 0.5 and is a preset parametermin≤0.9；
For example, before the step a41, the step a40 is further performed, and the preset coefficient and/or the preset parameter are input.
9. The image signal processing method according to claim 5, wherein the step A5 further comprises the step A51 of buffering the backlight luminance signal BL.
10. The image signal processing method according to claim 5, wherein in step A5, the backlight luminance signal BL is a product of a reference luminance value S and a backlight adjustment value T.
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