KR20180041413A - Efficient low power contrast enhancement apparatus and method for transmissive LCDs - Google Patents

Abstract

The present invention relates to an apparatus and a method for improving a low power contrast ratio for a transmissive LCD.
According to another aspect of the present invention, there is provided a display device comprising: an image input unit receiving an input image to be displayed on a transmissive LCD; A brightness corrector for correcting brightness by reducing the brightness of the backlight and increasing the pixel value based on the input image received by the image input unit; Closing the optimization problem considering brightness correction, contrast ratio improvement, and information loss - a contrast ratio improvement part that obtains a contrast ratio conversion function by using a format solution; And an image output unit for generating an output image by applying the contrast ratio conversion function calculated by the contrast ratio improving unit to an input image and outputting the output image.

Description

[0001] The present invention relates to a low power contrast enhancement apparatus and method for transmissive LCDs,

The present invention relates to an apparatus and a method for improving a low power contrast ratio for a transmissive LCD.

Generally, a display device such as a liquid crystal display (LCD) is used for displaying an image on a TV, a notebook computer, a desktop computer, or the like.

Since a display device such as an LCD can not generate light by itself, an image is displayed using light emitted from a separate light source.

That is, the LCD includes a liquid crystal panel and a light emitting element including a backlight on the rear surface of the liquid crystal panel, and the liquid crystal panel displays an image by adjusting the transmittance of light emitted from the light emitting element.

In this way, the transmissive LCD is composed of a panel portion representing a shape and a backlight expressing brightness. Most of the power is consumed by the backlight and its power consumption is proportional to the brightness of the backlight.

Accordingly, in order to reduce the power consumed by the LCD, the brightness of the backlight is reduced, and in order to compensate the brightness of the backlight, brightness compensation is performed by increasing the pixel value to brighten the image.

In this way, since the contrast ratio of the resultant image is actually reduced when the brightness compensation is performed, the contrast ratio improvement technique should be additionally applied.

Because the display consumes the most power in a typical mobile device, it is important to reduce the power consumed by the display in order to increase the use time of the mobile device.

However, recent advanced brightness compensation techniques have a problem in that they are difficult to apply to a device having a low calculation resource such as a mobile device due to high computational complexity.

Korean Patent No. 10-024058 Korean Patent Publication No. 10-2015-0120293 Korean Published Patent No. 10-2012-0024829

1. Carroll, A., Heiser, G .: An analysis of power consumption in a smartphone. In: Proc. USENIX Ann. Technical Conf. (2010) 2. Chang, N., Choi, I., Shim, H .: DLS: Dynamic backlight luminance scaling of liquid crystal display. IEEE Trans. Very Large Scale Integr. (VLSI) Syst. 12 (8), 837-846 (2004) 3. Cho, S. I., Kang, S.J., Kim, Y.H .: Image quality-aware backlight dimming with color and detail enhancement techniques. J. Display Technol. 9 (2), 112-121 (2013) 4. Huang, T. H., Shih, K. T., Yeh, S. L., Chen, H. H. Enhancement of backlight-scaled images. IEEE Trans. Image Process. 22 (12), 4587-4597 (2013) 5. Iranli, A., Lee, W., Pedram, M .: HVS-aware dynamic backlight scaling in TFT-LCDs. IEEE Trans. Very Large Scale Integr. (VLSI) Syst. 14 (10), 1103-1116 (2006) Lee, C., Kim, C.S .: Power-constrained back-light scaling and contrast enhancement for TFT-LCD displays. In: Proc. IEEE Int. Conf. Image Process., Pp. 2793-2796 (2012) 7. Lee, C., Kim, J. H., Lee, C., Kim, C.S .: Optimized brightness com- pensation and contrast enhancement for transmissive liquid crystal displays. IEEE Trans. Circuits Syst. Video Technol. 24 (4), 576-590 (2014) 8. Lee, C., Lee, Y.Y., Kim, C.S .: Power-constrained contrast enhancement for emissive displays based on histogram equalization. IEEE Trans. Image Process. 21 (1), 80-83 (2012) 9. Ruggiero, M., Bartolini, A., Benini, L .: DBS4 video: Dynamic luminance backlight scaling based on multi-histogram frame char- acterization for video streaming application. In: Proc. ACM Int. Conf. Embedded Software, pp. 109-118 (2008) 10. Shih, K. T., Chen, H. H. Exploiting perceptual anchoring for color image enhancement. IEEE Trans. Multimedia 18 (2), 300-310 (2016) 11. Tsai, P. S., Liang, C. K., Huang, T. H., Chen, H. H. Image enhancement for backlight-scaled TFT-LCD displays. IEEE Trans. Cir- cuits Syst. Video Technol. 19 (4), 574-583 (2009)

In order to solve the above problems, the present invention proposes a method of reducing the calculation speed while maintaining the same performance by calculating the contrast ratio conversion function through the closure-type solution of the brightness compensation and the contrast ratio improvement and the optimization equation considering the information loss And to provide a low-power contrast ratio improvement apparatus and method for a transmissive LCD having the same.

According to an aspect of the present invention, there is provided an LCD comprising: an image input unit receiving an input image to be displayed on a transmissive LCD; A brightness corrector for correcting brightness by reducing the brightness of the backlight and increasing the pixel value based on the input image received by the image input unit; Closing the optimization problem considering brightness correction, contrast ratio improvement, and information loss - a contrast ratio improvement part that obtains a contrast ratio conversion function by using a format solution; And an image output unit for generating an output image by applying the control ratio conversion function calculated by the control ratio improving unit to an input image and outputting the output image.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display comprising the steps of: (A) receiving an input image to be displayed on a transmissive LCD; (B) correcting the brightness by decreasing the brightness of the backlight and increasing the pixel value based on the input image received by the brightness input unit; (C) Improvement of contrast ratio Clarification of optimization problem considering additional brightness correction, improvement of contrast ratio, and information loss; And (D) generating an output image by applying the control ratio conversion function calculated by the image output unit to the input image, and outputting the output image.

The apparatus and method for reducing the power consumption of the transmissive LCD according to the present invention can be applied to a device having a low performance such as a mobile device because the computational complexity is significantly lower than that of the prior art,

FIG. 1 is a block diagram of a low power contrast ratio improving apparatus for a transmissive LCD according to an exemplary embodiment of the present invention. Referring to FIG.
2 is a graph showing the results of the brightness compensation and the contrast ratio improvement.
3 is a detailed configuration diagram of the contrast ratio improving unit of FIG.
FIG. 4 is a flowchart illustrating a method of improving a low power control ratio for a transmissive LCD according to another exemplary embodiment of the present invention.
FIG. 5 is a diagram illustrating brightness compensated results according to the prior art and the present invention.
6 is a diagram showing a comparison between the conventional technique and the control ratio conversion function according to the present invention.
Figure 7 is a comparison of the computational complexity and run time of the conventional technique and the control ratio conversion function according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

First, the terminology used in the present application is used only to describe a specific embodiment, and is not intended to limit the present invention, and the singular expressions may include plural expressions unless the context clearly indicates otherwise. Also, in this application, the terms "comprise", "having", and the like are intended to specify that there are stated features, integers, steps, operations, elements, parts or combinations thereof, But do not preclude the presence or addition of features, numbers, steps, operations, components, parts, or combinations thereof.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

FIG. 1 is a configuration diagram of a low power control ratio improving apparatus for a transmissive LCD according to a preferred embodiment of the present invention.

Referring to FIG. 1, a low power contrast ratio improvement apparatus for a transmissive LCD according to an exemplary embodiment of the present invention includes an image input unit 100, a brightness correction unit 200, a contrast ratio improvement unit 300, a backlight driving unit 400, And a video output unit 500.

The image input unit 100 receives an input image to be displayed through a transmissive LCD.

Then, the image input unit 100 transmits the input image to the brightness correction unit 200 and the contrast ratio improvement unit 300.

The brightness correction unit 200 controls the backlight driving unit 400 to dim the brightness of the backlight, and performs brightness correction by increasing the input pixel value to compensate the backlight brightness.

In more detail, the brightness correction unit 200 obtains a transmission function t (k) with respect to the input pixel value k according to Equation (1).

(1)

t (k) =? ₁ -? ₂ (k / 255) ^?

Here,? ₁ ,? ₂ ,? Are transmission-type LCD device-dependent parameters. Transmission of the transmissive LCD is observed while changing the input pixel value (k) from 0 to 255.

Then, the transmittance can be expressed as a function of the input pixel value k, and t (k) in Equation 1 represents this.

However, not only the transmissive LCD is the same but also the transmissive function t (k) is expressed differently according to the brightness setting even in the same LCD.

At this point, the function itself does not change, but you can get the desired function for all transmissive LCDs by adjusting only three device-dependent parameters.

Thus, three parameters with different values according to the transmissive LCD are referred to as device-dependent parameters. That is, different transmissive LCDs have different values of ω ₁ , ω ₂ , and γ in the same function.

Further, the transmission luminance L with respect to the pixel value k is obtained by the following equation (2).

(2)

L = B _max · t (k)

Where B _max is the maximum intensity of the backlight.

The brightness correction unit 200 reduces power by decreasing the maximum intensity of the backlight by a dimming factor b equal to or greater than 0 and less than or equal to 1.

Then, the brightness correction section 200 keeps the transmitted luminance by increasing the input pixel value to the k y _k.

The corrected transmission luminance (corrected transmission luminance) L 'becomes L' = b · B _max · t (y _k ), and L = L '.

(3)

Let y _{k be} the output pixel value that increases the pixel value so that the brightness perceived by the eye is the same for the input pixel value _k . The brightness conversion function of the output pixel value with respect to all input pixel values is expressed as a vector y = [y ₀ , y ₁ , ... , y ₂₅₅ ] ^T.

In Fig. 2, the expression "Brightness compensation" is an example of y.

On the other hand, when the contrast ratio improving unit 300 performs brightness compensation, the contrast ratio of the resulting image actually decreases, and thus the contrast ratio is further improved.

The contrast ratio improving unit 300 includes a histogram generating unit 310, a histogram modifying unit 320, an accumulative distribution function calculating unit 330, and a converting function calculating unit 340.

The histogram generator 310 generates a histogram of the input image (data). Here, the histogram of the input image (h _k) can be obtained for the probability density function may be represented as (p _k), the probability density function (p _k) is the histogram (h _k) of the input image by dividing the total number of pixels. The probability density function (p _k ) can be defined as Equation (4).

(4)

Here, the histogram (h _k ) corresponding to the k-th represents the number of pixels having a pixel value k.

Also, 1 represents a column vector, and all of the elements represent a 1 value. T (Transpose) is an operator that creates transposed matrices.

The histogram corrector 320 may increase or decrease the histogram value of the input image and may be obtained by a modified histogram value m _k , m = f (h).

For example, the histogram corrector 320 may reduce the large value of the histogram bin of the pixel region protruding beyond the reference value out of the histogram values of the input image based on the log-based function, Value can be increased.

Here, in another embodiment, the histogram corrector 220 can be used to increase or decrease the histogram value of the input image described above.

Accordingly, when the image quality improvement based on the histogram equalization is performed, the brightness of the image is excessively changed, and the conventional problem that the noise is increased and the atmosphere of the original image is lost is solved.

If it is defined that the modified histogram described above is represented,

By a histogram (m _k) instead of the history modification grams (h _k) it may be carried out a histogram processing procedure.

Meanwhile, the cumulative distribution function calculating unit 330 calculates an cumulative distribution function for the histogram of the input image. Here, the cumulative distribution function calculating unit 330 may calculate the normalized cumulative distribution from the brightness distribution of the input image.

That is, the cumulative distribution function c _k of the pixel value k generated by sequentially adding the probability density function p _k of Equation (4) can be defined as Equation (5).

 &Quot; (5) "

The conversion function calculating unit 340 generates a conversion function for re-adjusting the dynamic range of each contrast ratio of the input image (or the original image). That is, when the cumulative distribution function is multiplied by the maximum contrast ratio, a conversion function is generated, and an output image having a high contrast ratio can be obtained by converting each input pixel of the input image into an output pixel.

In this way, the dynamic range of each of the contrast ratios of the input image is readjusted through the conversion function. For this, the contrast ratio conversion function can be defined as Equation (6).

 &Quot; (6) "

Here, (2 ^b -1) represents the maximum contrast ratio, and, for example, represents an 255 value in an 8-bit image.

Then, the control ratio conversion function (x _k ) is expressed by x = [x ₀ , x ₁ , ... , x ₂₅₅ ] ^T , which can be expressed as a vector using a difference matrix R, as shown in Equation (7).

&Quot; (7) "

는 수정된 히스토그램의 합이 최대 밝기 값인 255가 되도록 하는 정규화된 열벡터로서 하기 수학식8과 같이 정의될 수 있다. 이와 같은 정규화된 열벡터는 0부터 y₂₅₅값을 가진다.here,

May be defined as a normalized column vector such that the sum of the modified histograms is 255, which is the maximum brightness value, as shown in Equation (8). These normalized column vectors have values from 0 to y ₂₅₅ .

(8)

이며,

이다.Further, R denotes a difference matrix

Lt;

to be.

  Therefore, the brightness conversion function and the contrast conversion function have the same range.

For example, when m = h, the histogram equalization is performed. In Fig. 2, "contrast enhancement" is an example of x.

Therefore, the final control ratio conversion function x to be obtained must satisfy both of the above two conditions (brightness compensation and control ratio improvement). Therefore, it converts to the following optimization problem.

(9)

대신

를 사용한다.Where α is a constant controlling the relative importance of brightness compensation and contrast ratio improvement. Also, to compare the two functions equally

instead

Lt; / RTI >

는 대조비 최대 인자이다.From here,

Is the maximum control factor.

2, the conversion functions are converted to values larger than 255, which is the maximum value that can be expressed by a general display.

Therefore, the value converted to a value larger than 255 is set to the maximum value of 255, and then the error occurring at this time is measured.

로 정의하고, 변환함수 x를 이용하여 하나의 영상을 변환할 때 발생하는 전체 정보 손실

을 아래 수학식 10로 정의한다.That is, the information loss caused by the transform function x _k

, And the total information loss that occurs when converting one image using the transform function x

Is defined by Equation (10) below.

(10)

이며, H는 히스토그램 대각행렬이다.From here,

And H is a histogram diagonal matrix.

Finally, a new optimization problem that solves the optimization problem expressed by Equation (9) and at the same time minimizes information loss can be expressed as follows.

(11)

The constraint condition is x ₀ = y ₀ , x ₂₅₅ = y ₂₅₅ , and R x? ₀ is a constraint condition such that the control ratio conversion function is a monotone increasing function. Here, [lambda] is a parameter for improving the low power control ratio and controlling the information loss amount.

에서 아래와 같이 정의한다.In order to solve this problem, Lagrangian

Is defined as follows.

 (12)

및

는 라그랑지안 멀티플라이어이고,

는 첫번째와 마지막 원소만 1이고, 나머지는 모두 0인 행렬이다.From here,

And

Is a Lagrangian multiplier,

Is a matrix in which only the first and last elements are 1s, and all others are 0s.

The condition of the Karush-Kuhn-Tucker (KKK) is expressed by the following equations (13) to (17).

(13)

(14)

(15)

(16)

(17)

to be.

이다.Where N is the diagonal matrix of v, N = diag (v)

to be.

The converting function calculating section 340 may obtain a circulation of the equation (18) below the μ ₂₅₅ are erased, as follows except the k th term in the second term, loosen the vector of Equation 17 (k + 1), In order to simplify the expression, μ = μ ₀ .

(18)

In equation (12), x ₀ is also a constant since it is fixed at constant y ₀ .

If the left side of the equation (18) is recursively substituted into x _k -x _{k -1} on the right side of the next step, the equation (18) is expressed as the following equation (19).

(19)

Here, k? 0.

Can erase all the k≥1 v _k In Equation 19 by using Equation 14 to 16, and finally as follows: {x _0, x _1, ... , x _{k -1} }, a closed-form solution x _k can be obtained for a single variable μ as shown in Equation 20 below.

(20)

Here, k? 0.

In Equation (11), since the constraint condition is x ₂₅₅ = y ₂₅₅ , μ satisfying this condition is obtained. In other words, we define the function f (μ) = x ₂₅₅ -y ₂₅₅ for μ, and obtain the solution satisfying f (μ) = 0 by using the secant method, which is a method of finding the solution of the equation.

Once μ is obtained, since x ₀ is known, all x _k are obtained by the expression (20 ₎ , and finally the control conversion function x is obtained.

On the other hand, the backlight driver 400 reduces the brightness of the backlight under the control of the brightness corrector 200.

The output image generating unit 500 generates an output image from the input image based on the control ratio conversion function x.

FIG. 4 is a flowchart illustrating a method of improving a low power control ratio for a transmissive LCD according to another exemplary embodiment of the present invention.

Referring to FIG. 4, in step S100, an image input unit receives an input image, in step S100, a low power control ratio improvement method for a transmissive LCD according to another exemplary embodiment of the present invention.

Then, the brightness correction unit performs brightness correction (S200).

Next, the comparison ratio improvement section performs the comparison ratio improvement (S300).

The output image generator generates and outputs an output image reflecting the result of the comparison ratio improvement (S400).

The details of each step of the low power control ratio improvement method for a transmissive LCD according to another embodiment of the present invention are described and described in detail above.

(A), (b), (c) and (d) show the Iterative method and the approximate method, respectively. Show the results according to the present invention. It can be seen that the results of the present invention are not significantly different in performance from other methods.

FIG. 6 is a diagram for comparing the conversion function of the conventional technique with the conversion ratio conversion function according to the present invention. It can be seen that the conversion function according to the present invention is the same as the Iterative method.

 Figure 7 is a comparison of the computational complexity and run time of the conventional technique and the control ratio conversion function according to the present invention.

The computation complexity and the execution time show that the present invention is much faster than the Iterative method.

As described above, the apparatus and method for reducing the power consumption of the transmissive LCD according to the present invention can be applied to a device having low performance such as a mobile device, so that a high quality image can be displayed while reducing power consumption.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments of the present invention are not intended to limit the scope of the present invention but to limit the scope of the present invention. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

100: image input unit 200: brightness correction unit
300: contrast ratio improving unit 310: histogram generating unit
320: histogram corrector 330: cumulative distribution function calculating unit
340: conversion function calculating unit 400: backlight driving unit
500: Video output unit

Claims (13)

An image input unit for receiving an input image to be displayed on a transmissive LCD;
A brightness corrector for correcting brightness by reducing the brightness of the backlight and increasing the pixel value based on the input image received by the image input unit;
Closing the optimization problem considering brightness correction, contrast ratio improvement, and information loss - a contrast ratio improvement part that obtains a contrast ratio conversion function by using a format solution; And
And an image output unit for generating an output image by applying the contrast ratio conversion function calculated by the contrast ratio improving unit to the input image and outputting the output image. The method according to claim 1,
The control-
A histogram generation unit for generating a histogram of an input image;
A histogram modifier for increasing or decreasing a histogram value of the input image; And
A conversion function calculating unit for calculating a control ratio conversion function by equalizing the histogram corrected by the histogram correcting unit and calculating a control ratio conversion function using the brightness correction and the contrast ratio improvement and the optimization problem considering the information loss using a closed- A low power contrast ratio improvement device for a transmissive LCD. The method according to claim 2,
The conversion function calculating unit may be configured such that the conversion ratio conversion function is x, the difference matrix is R, y is a brightness conversion function, k is an input pixel value, x _k is a control conversion function of the input pixel value k, The information loss caused by the co-efficient conversion function x _k is _denoted by x _{c , k} ,

Where H is a histogram diagonal matrix, and λ is a parameter for adjusting the low power control ratio and the information loss magnitude, the brightness correction and the contrast ratio improvement The optimization problem considering the information loss is expressed by Equation (12) below.

(11)

The constraint condition is x ₀ = y ₀ , x ₂₅₅ = y ₂₅₅ , and R x? ₀ is a constraint condition such that the control ratio conversion function is a monotone increasing function. The method according to claim 3,
The transform function calculator may express the equation (11) as a Lagrangian of the following equation (12) and set the Karush-Kuhn-Tucker (KKK) condition as shown in the following equations (13) to , Brightness correction and contrast ratio improvement, and optimization problem considering information loss. A low power contrast ratio improvement device for a transmissive LCD that calculates a contrast ratio conversion function using a form solution.
(12)

From here,

And

Is a Lagrangian multiplier,

Is a matrix in which only the first and last elements are 1 and the rest are all 0s.
(13)

(14)

(15)

(16)

(17)

Where N is the diagonal matrix of v, N = diag (v)

being. The method of claim 4,
Calculating the transfer function unit x in the left side of the unpacking vector of Equation 17 (k + 1) by subtracting the k th term in the second term to obtain a circulation of the equation (18), equation (18) on the right side of the following steps: _k - x _{k -1} so as to express Equation (18) as shown in Equation (19), and erase all v _k in Equation (19) using Equation (14) ₀ , x ₁ , ... , x _{k -1} } is given, the closed-form solution x _k is calculated as a function of a single variable μ as shown in equation (20).
(18)

(19)

Here, k? 0.
(20)

Here, k? 0. The method of claim 5,
The conversion function calculating section defines a function f () = x ₂₅₅ -y ₂₅₅ for μ, obtains a solution of the equation satisfying f (μ) = 0 by using a secant method, A low power contrast ratio improvement device for a transmissive LCD for calculating all x _k by equation (20) and calculating a control ratio conversion function x. The method according to claim 1,
And a backlight driving unit for reducing the brightness of the backlight under the control of the brightness correction unit. (A) receiving an input image to be displayed on a transmission type LCD;
(B) correcting the brightness by decreasing the brightness of the backlight and increasing the pixel value based on the input image received by the brightness input unit;
(C) Improvement of contrast ratio Clarification of optimization problem considering additional brightness correction, improvement of contrast ratio, and information loss; And
(D) applying a control ratio conversion function calculated by the image contrast output unit to the input image to generate an output image and outputting the output image. The method of claim 8,
The step (C)
(C-1) generating a histogram of the input image by the contrast ratio improving unit;
(C-2) modifying the histogram by increasing or decreasing the histogram value of the input image; And
(C-3) calculating a control ratio conversion function through equalization of the histogram corrected with the control ratio improving unit, calculating a control ratio conversion function using the brightness correction, the control ratio improvement, and the optimization problem considering information loss, / RTI > for a transmissive LCD. The method of claim 9,
The control ratio improving unit may be configured such that the control ratio converting function is x, the differential matrix is R, y is a brightness converting function, k is an input pixel value, x _k is a control ratio conversion function of the input pixel value k, The information loss caused by the transform function x _k is _denoted by x _{c , k} ,

Where H is a histogram diagonal matrix, and λ is a parameter for adjusting the low power control ratio and the information loss magnitude, the brightness correction and the contrast ratio improvement A method for improving the low power contrast ratio for a transmissive LCD is shown in Equation (11) below.

(11)

The constraint condition is x ₀ = y ₀ , x ₂₅₅ = y ₂₅₅ , and R x? ₀ is a constraint condition such that the control ratio conversion function is a monotone increasing function. 12. The method of claim 10,
The contrast ratio improving unit may express the Equation (11) as Lagrangian of Equation (12) and set the Karush-Kuhn-Tucker (KKK) condition as Equation (13) to Equation (17) Improvement of Low Power Contrast Ratio for Transmissive LCDs that Calculate the Coefficient of Conversion Function Using Closed Form - Solving.
(12)

From here,

And

Is a Lagrangian multiplier,

Is a matrix in which only the first and last elements are 1 and the rest are all 0s.
(13)

(14)

(15)

(16)

(17)

Where N is the diagonal matrix of v, N = diag (v)

being. 12. The method of claim 11,
The daejobi improved unpacking unit vector of equation 17 (k + 1) th term in the k-th subtracting wherein to obtain a circulation of the equation (18), x in the left-hand side of equation (18) on the right side of the following steps: _k -x _{k -1} to express Equation 18 as shown in Equation 19, and all v _k in _k Equation 19 in Equation 19 are canceled using Equations 14 to 16, and {x ₀ , x ₁ , ... , x _{k -1} } is given, a closed-form solution x _k is calculated as a function of a single variable μ as shown in equation (20).
(18)

(19)

Here, k? 0.
(20)

Here, k? 0. The method of claim 12,
The control ratio improving unit defines a function f () = x ₂₅₅ -y ₂₅₅ for μ, obtains a solution of the equation satisfying f (μ) = 0 by using a secant method, how to improve low power daejobi for a transmission type LCD for calculating a transfer function daejobi x obtain all x _k by equation 20.

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