Control signal generation circuit, video display device, and control signal generation method

Patent metadata

Field	Value
Publication number	US-2015348506-A1
Application number	US-201514722777-A
Country	US
Kind code	A1
Filing date	May 27, 2015
Priority date	May 27, 2014
Publication date	Dec 3, 2015
Grant date	—

Abstract

A control signal generation circuit includes: a first circuit unit which controls, according to inputted video signals, light-up amount of each pixel of a display panel where a plurality of pixels constituted by including a white sub-pixel are disposed; and a second circuit unit which controls luminance of a backlight that lights up the display panel from a back surface. The second circuit unit calculates a saturation feature value in one frame from the saturation value of each pixel, generates a signal for controlling the luminance of the backlight based thereupon, and calculates a luminance increase rate by using the saturation value of each pixel and the saturation feature value. The first circuit unit performs luminance decreasing processing of each pixel according to the luminance increase rate, and supplements the saturation of each pixel according to the light-up amount of the white sub-pixels.

First claim

What is claimed is:

1 . A control signal generation circuit, comprising:
a first circuit unit which controls, according to an inputted video signal, light-up amount of each pixel of a display panel where a plurality of pixels constituted by including a white sub-pixel are disposed; and a second circuit unit which controls luminance of a backlight that lights up the display panel from a back surface, wherein: the second circuit unit comprises an each-pixel saturation calculation circuit which calculates a saturation value of each pixel, a feature value/luminance decrease amount calculation circuit which calculates a saturation feature value in one frame by using the saturation value of each pixel, and calculates luminance decrease amount of the backlight based thereupon, a PWM signal generation circuit which generates a signal for controlling the luminance of the backlight based on the luminance decrease amount of the backlight, and transmits the generated signal towards the backlight, and an each-pixel luminance increase rate calculation circuit which calculates a luminance increase rate of each pixel by using the saturation value of each pixel and the saturation feature value; and the first circuit unit comprises a saturation supplementing circuit which supplements the saturation of each pixel according to the light-up amount of the white sub-pixel.

2 . The control signal generation circuit as claimed in claim 1 , wherein
the first circuit unit further comprises an each-pixel luminance decreasing circuit which performs luminance decreasing processing of each pixel according to the luminance increase rate.

3 . The control signal generation circuit as claimed in claim 1 , wherein
the feature value/luminance decrease amount calculation circuit comprises: an each-pixel saturation judging section which judges whether the saturation value of each pixel is larger or smaller with respect to a saturation threshold value set in advance; an each-pixel saturation deviation sum calculation section which individually calculates sum total of saturation deviation regarding a case where the saturation value is judged as being equal to or less than the saturation threshold value and a case where the saturation value is judged as being larger than the saturation threshold value, by the each-pixel saturation judging section, respectively; a total-pixel saturation deviation average calculation section which calculates a saturation deviation average value of total pixels by using the sum total of the each saturation deviation and number of resolution of the display panel; and a saturation feature value calculation section which calculates the saturation feature value by using the saturation deviation average value of the total pixels, a saturation maximum value of the total pixels, and a coefficient regarding luminance control of the backlight.

4 . The control signal generation circuit as claimed in claim 3 , wherein
the feature value/luminance decrease amount calculation circuit calculates the luminance decrease amount of the backlight to be a small value according to an average value of the saturation value of each pixel in a case where the average value is a higher value than the saturation threshold value, calculates the luminance decrease amount to increase continuously as the average value becomes decreased until reaching the saturation threshold value from the higher value, calculates the luminance decrease amount to decrease continuously as the average value becomes decreased after exceeding the saturation threshold value, and calculates the luminance decrease amount to continue at the saturation threshold value.

5 . The control signal generation circuit as claimed in claim 3 , wherein
provided that the sum totals of the each saturation deviation are defined as Xa, Xb, the saturation threshold value is defined as a coefficient A (0<A<1), the saturation value of k-th (k is an arbitrary value from 1 to the number of resolution) pixel is defined as chroma(k), the feature value/luminance decrease amount calculation circuit calculates value of Xa by applying a numerical expression Xa=Σ{1−(1/A)×chroma (k)} in a case where the chroma(k) is equal to or less than the coefficient A, calculates value of Xb by applying a numerical expression Xb=Σ{1/(1−A)}×(chroma (k)−A) in a case where the chroma(k) is larger than the coefficient A, and calculates a quotient acquired by dividing the sum totals by the number of resolution as the saturation deviation average value of the total pixels.

6 . The control signal generation circuit as claimed in claim 5 , wherein
provided that the saturation deviation average value of the total pixels is defined as DAVE, a saturation maximum value of the total pixels is defined as MAX(chroma), the saturation feature value is defined as Rank, and a coefficient regarding luminance control of the backlight is defined as B (0<B<1), the feature value/luminance decrease amount calculation circuit calculates the saturation feature value based on a numerical expression Rank=MAX(chroma)×{B×DAVE+(1−B)}.

7 . The control signal generation circuit as claimed in claim 6 , wherein
the feature value/luminance decrease amount calculation circuit calculates a PWM value PWM used for the luminance control of the backlight from a numerical expression PWM=1/{C−(C−1)×Rank} by using another coefficient C (1≦C≦2) regarding the luminance control of the backlight, and calculates the luminance decrease amount of the backlight based on the PWM value.

8 . The control signal generation circuit as claimed in claim 3 , wherein
the saturation threshold value is set as a value that is larger than 0 and equal to or smaller than 0.5.

9 . The control signal generation circuit as claimed in claim 3 , wherein
the coefficient regarding the luminance control of the backlight is set as a value acquired by subtracting the saturation threshold value from 1.

10 . The control signal generation circuit as claimed in claim 1 , wherein
the feature value/luminance decrease amount calculation circuit calculates the luminance decrease amount of the backlight as a small value in a case where the video signal is a case of a high saturation color display, calculates the luminance decrease amount of the backlight as a large value in a case where the video signal is a case of low saturation color display or a case of intermediate saturation color display containing primary color display in a part thereof, and calculates the luminance decrease amount of the backlight as a small value in a case where the video signal is a case of achromatic display containing primary color display in a part thereof.

11 . The control signal generation circuit as claimed in claim 7 , wherein
in a case where a ratio between the maximum white luminance of the white sub-pixel and the maximum white luminance generated by the video signal is 1:1, the feature value/luminance decrease amount calculation circuit sets the another coefficient C as a value that is twice a ratio of an aperture area of sub-pixels of an RGBW-type display panel with respect to an aperture area of sub-pixels of an RGB-type display panel.

12 . The control signal generation circuit as claimed in claim 10 , wherein
provided that a ratio of an aperture area of sub-pixels of an RGBW-type display panel with respect to an aperture area of sub-pixels of an RGB -type display panel is defined as Y, and a ratio of a maximum white luminance of the white sub-pixels and a maximum white luminance generated by the video signal is p:q, the feature value/luminance decrease amount calculation circuit calculates the another coefficient C from a numerical e

Assignees

• Nlt Technologies Ltd

Inventors

• Ooga Kouichi

Classifications

• G09G2300/0426

  Layout of electrodes and connections · CPC title

• G09G2330/021

  Power management, e.g. power saving · CPC title

• G09G5/02

  characterised by the way in which colour is displayed {(details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607)} · CPC title

• G09G3/3611

  Control of matrices with row and column drivers · CPC title

• G09G2300/0452

  Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components · CPC title