CN101290754B - Methods of LCD backlight dimming, LCD/image signal compensating and LCD display controlling - Google Patents
Methods of LCD backlight dimming, LCD/image signal compensating and LCD display controlling Download PDFInfo
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- CN101290754B CN101290754B CN2008101100618A CN200810110061A CN101290754B CN 101290754 B CN101290754 B CN 101290754B CN 2008101100618 A CN2008101100618 A CN 2008101100618A CN 200810110061 A CN200810110061 A CN 200810110061A CN 101290754 B CN101290754 B CN 101290754B
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Abstract
A method for reducing energy consumption inside a liquid crystal display (LCD) illuminated by backlight equipment comprises the following steps that: backlight is adjusted darker and image luminance is adjusted to compensate the darker backlight. According to an amplitude limiting point, a backlight keeping-down factor is determined, and the amplitude limiting point is determined according to the pixel luminance distribution of an image signal. Image luminance is adjusted according to the keeping-down factor, wherein a first image signal mapping function is used to adjust the pixel luminance blow a luminance threshold, while a second image signal mapping function is used to adjust the pixel luminance above the luminance threshold.
Description
Technical field
The present invention relates to liquid crystal display (LCD) equipment that uses backlight to illuminate display image.The present invention be more particularly directed to dim backlight to cut down the consumption of energy, and to adjust LCD printing opacity value (transmittance value) simultaneously or brightness of image value (image intensity value) dims backlight with compensation.
Background of invention
Various liquid crystal displays (LCD) equipment use a light source with image projection to display surface (as screen), or light source is placed on the LCD panel back so as direct viewing to the image that on the LCD panel, produces.The expectation that cuts down the consumption of energy and increase LCD display image contrast (contrast of image) has expedited the emergence of multiple technologies, dynamically changes light source and/or this LCD equipment luminance brightness (light intensity) backlight.The variation of common this light-source brightness can cause being darkened to below the luminance brightness that can watch display image is whole.
In order to overcome this problem, many compensation techniques have been suggested and have been used for backlight dimming.In the United States Patent (USP) 5,717,422 that licenses to Fergasson, the United States Patent (USP) 7,053,881 that licenses to Itoh, the United States Patent (USP) 7,176,878 that licenses to Lew etc. and U.S. Patent application 2007/0092139, various technical examples have been disclosed.United States Patent (USP) 5,717,422 propose one dims the factor and expands the LCD transmittance simply based on the backlight of picture signal mean flow rate, and this can cause blocking of high luminance values.United States Patent (USP) 7,053,881 propose the factor that dims backlight of an and highest brightness value average based on picture signal, compensate and do not carry out LCD, and this can cause the perception of display image to dim.United States Patent (USP) 7,176, the 878 linear amplitudes growths that propose a LCD signal dim with compensate for backlight, but the method that dims are not discussed.At last, U.S. Patent application 2007/0092139 has proposed one and has dimmed the factor and expand the LCD transmittance simply based on the backlight of picture signal highest brightness value, and this can cause high luminance values to be blocked.
Summary of the invention
So, an object of the present invention is to provide a kind of method of LCD display backlight that dim to cut down the consumption of energy.Another object of the present invention provides the method that a kind of LCD of adjustment printing opacity value or brightness of image value dim with compensate for backlight.
Disclosed a kind of method that keeps the visual image perceived brightness on the LCD backlight that dimming at this, this method may further comprise the steps:
According to one dim that the factor dims backlight liquid crystal display and
Dim the factor based on this and determine a compensation range and a luminance threshold in compensation range, luminance threshold is about the function of clipping point and less than clipping point,
Below luminance threshold, use the brightness range of the first picture signal mapping function (tone mapping) spread signal, more than luminance threshold, use the brightness range of the second picture signal mapping function restricting signal.
Preferably, the method that dims LCD backlight may further comprise the steps:
Determine a clipping point (clipping point) based on the pixel brightness contribution of picture signal,
Based on clipping point determine one backlight dim the factor and
Illuminate backlight on the factor in definite dimming.
Preferably, clipping point is between 60% and 99% percentage point of pixel brightness contribution.
Preferably, pixel brightness contribution is based on the no colour brightness (achromatic intensity) of picture signal interior pixel.
Preferably, pixel brightness contribution is based on the maximal value of redness, green and the blue channel brightness of picture signal interior pixel.
Preferably, dimming the factor is to be determined by following equation:
Wherein CP is the amplitude limit point value, and Imax is the maximal value of pixel intensity, and p is one and is not less than 1 constant.The p value is to determine according to LCD input and output feature, common gamma value near display.
Preferably, luminance threshold is less than clipping point.
Preferably, threshold value is to be determined by following equation: | FP-CP|=|CP-Imax|.Wherein FP is a threshold value, and CP is a clipping point, and Imax is the maximal value of pixel intensity.
Preferably, a function in the first and second picture signal mapping functions is non-linear.
Preferably, second mapping function is a Nonlinear Mapping function.
Preferably, the non-linear second picture signal mapping function produces according to pixel brightness contribution.
Description of drawings
Now by example also with reference to the accompanying drawings, an exemplary embodiment of the present invention is described, wherein:
Fig. 1 describes the module map that dims with the LCD/ image signal compensating backlight according to the present invention;
Fig. 2 is the brightness histogram of a LCD or image, signal, is used to describe determine the clipping point that dims backlight.
Fig. 3 is a luminance signals histogram, and the expansion that is used to describe the luminance signals scope dims with compensate for backlight.
Fig. 4 be illustrated in Fig. 2 original signal brightness range and Fig. 3 expand between the brightness range the picture signal mapping and
Fig. 5 graphic extension is shone upon to improve more blocking of high luminance values according to picture signal of the present invention.
Exemplary embodiments describes in detail
Now will be in detail with reference to an exemplary embodiments of the present invention, its example will be described in corresponding accompanying drawing.
According to the present invention, a kind of method of controlling the brightness of LCD display device such as LCD TV comprises dimming the pixel transmittance that improves simultaneously on the LCD panel backlight, thereby keeps or improve the original visual brightness feature of display image.The present invention includes two aspects.First aspect is a kind ofly to determine the factor, an and adaptation method of carrying out the picture carrier distributional analysis especially of dimming backlight based on the brightness of image feature.Thereby the brightness of the image that a second aspect of the present invention is a kind of brightness value of adjusting the LCD transmittance adaptively or adjusting picture signal equally sees with the reduction of compensation on backlight illumination can be because of the method that changes that dims backlight.In second aspect, determine a compensation range based on the factor that dims backlight.Find out the threshold value (Fidelity Point) in compensation range, use different picture signal mapping algorithms more than threshold value, to shine upon then, strengthen the brightness of display image with following compensation range.When these two aspects of the present invention were used to the backlight LCD display device, the present invention had lower energy consumption, but but did not damage the apparent brightness of display image.
To describe method of the present invention in detail now.When describing, term brightness (brightness), brightness (1uminance) and signal intensity (intensity) can be exchanged, be meant the visible light of the relative populations of sending from image or each image pixel, it can be felt when the people watches image.The brightness value of each pixel is that 1uma passage by picture signal provides in the image.In a LCD display, the 1uma channel value is determined the transmittance of LCD pixel.A second aspect of the present invention is illustrated by the compensation of LCD printing opacity, but this is not intended to limit the scope of the invention or function.It will be understood to those of skill in the art that by direct compensation LCD drive signal or by the 1uma value in the compensating image signals, can implement the present invention.Relation between the perceived brightness of image (B), backlight illumination (L) and the LCD transmittance (T) is B=L * T.
The key step of a preferred embodiment of the invention as shown in Figure 1.An input LCD signal inputs to Luminance Distribution analysis 2 to find out luminance signals Nogata Figure 10.Aspect backlight control of the present invention, in brightness histogram, determine a clipping point (Clipping Point), determine that according to clipping point dims a factor 4 then.Aspect LCD control of the present invention (as image compensation), at first step 5 is to determine compensation range and a threshold value of a LCD (or image) signal.Then step 6,7 is determined picture signal mapping curve separately, is used for being mapped to more than the threshold value original LCD range of signal and following compensating signal scope.These two picture signal mapping curves are incorporated into step 8, and to form a final picture signal mapping curve, it produces output LCD signal 9.
Fig. 2 describes a kind of brightness histogram 10 of input LCD signal 1 that utilizes and finds out clipping point and the method for optimizing that dims the factor backlight.In image histogram shown in Figure 2, X or transverse axis are represented the original signal brightness value (as the white gray-Y channel code value of image) from minimum value (Imin) to maximal value (Imax).Y or Z-axis represent to have in the signal 1 number of pixels of that brightness value.The peak value of pixel intensity in the piece image, Ip is equal to or less than Imax; In the signal of a typical 8-bit, minimum luminance value Imin is 0 to Ip less than Imax. in this figure, and maximum brightness value Imax is 255.For the purpose of the present invention, these occurrences are optional, also can be that arbitrary value is represented minimum and high-high brightness level.
For the ease of explaining the present invention, the inventor has introduced the notion of a clipping point 11 (Clipping Point).Clipping point 11 is positioned at 95% percentage point of Luminance Distribution scope, only has 5% pixel to drop in signal Nogata Figure 11 on it.5% this value be the inventor find out so that optimal results to be provided, but be not essential to the present invention.Usually, clipping point will be between 60% and 99% percentage point of Luminance Distribution scope, but according to specific image type, higher or lower value may produce better or same acceptable result.A key character of clipping point 11 is: to a darker image, clipping point 11 will be a low value (low value), because most of pixel has a low brightness values, but to a bright image, clipping point 11 will be a high value, because more pixels have higher brightness value.The position that it should be appreciated by those skilled in the art that clipping point 11 in video image will dynamically change frame by frame.
The factor (BLdim) that dims backlight is the function of a backlight illumination that dims about an amplitude limit point value, that is:
Wherein CP is the amplitude limit point value, and Imax is the maximum pixel brightness value, and p is one and is not less than 1 constant.The p value is to determine according to LCD input and output feature, and the gamma (gamma) near display is worth usually.
In preferred embodiment, the factor (BLdim) that dims backlight is limited between the upper and lower bound.Maximum dims the factor, and promptly dimming of minimum is 85%, and the minimum dim factor, promptly dimming of maximum is 55%.If the factor that dims backlight is higher than the upper limit, the factor that dims then backlight promptly becomes the upper limit or 85%.Be lower than lower limit if dim the factor, then dim the factor and promptly become lower limit or 55%.This boundary can be represented by following equation.
If BLdim＞85%, then BLdim=85%
If BLdim＜55%, then BLdim=55%
The upper and lower bound that dims the factor backlight is not to be used for limiting the scope of the invention or function.The inventor believes that 55% and 85% boundary can produce best result in according to method of the present invention.But also can find out other boundary provides same acceptable or possibility even better result.In one particular embodiment of the present invention, this boundary can be adjusted by spectators, produces that value of best result so that satisfy individual subjectivity to watch.
For fear of totally dimming on the image perceived brightness, must before display image, adjust LCD printing opacity value or brightness of image value.But this is not a most critical to a first aspect of the present invention, determines that a method that dims the factor backlight can be used in the LCD display, and does not need to compensate LCD or picture signal and allow backlight dimming.Determine that the method that dims level backlight is dynamic, and consider the brightness of picture signal, so this is an improvement that dims method backlight as used herein.
The compensation of LCD signal input 1 is shown in Figure 12 by the Nogata of Fig. 3, and wherein the brightness of image scope expands to Imax/ (BLdim) from Ip
1/pThe method of another kind of range expansion is to elongate image histogram 12, makes clipping point 11 move to Imax, thereby the brightness of 5% pixel in the image is greater than Imax.
Fig. 4 only is used as explanation, the compensating image signals mapping of describing in its displayed map 3.The horizontal X axle is represented the original brightness scope of LCD signal, and the vertical Y axle is represented the up-to-date or subject brightness range of signal.The mapping that dotted line 15 expressions are one 1 pair 1, wherein original scope does not change.Linear mapping of dotted line 16 expressions, and Nonlinear Mapping of solid line 17 expressions from the original brightness scope to up-to-date brightness range from the original brightness scope to up-to-date brightness range.The map type that uses in the present invention is not most important, can use any linearity well known in the art or nonlinear images signal map algorithm.Those skilled in the art can prove, in fact can not be with the brightness of image range expansion to more than the Imax value, and will be shown device hardware and block because be higher than the brightness value of Imax.In order to overcome this problem, the present invention introduces a threshold concept, and below threshold value, by the brightness range of the first picture signal mapping function spread signal, thereby the transmittance that improves the LCD crystalline substance dims with compensate for backlight.More than threshold value, use the brightness range of the second picture signal mapping function compressed signal, so that the brightness of image value is limited in the actual maximum brightness value Imax.
Fig. 5 describe a kind of with picture signal mapping be limited in threshold value more than 18 to minimize the method that high luminance values is blocked.On an appropriate brightness value that is lower than clipping point 11, select threshold value 18.In preferred embodiment, threshold value is according to equation | FP-CP|=|CP-Imax| selects, and still, this is not essential for the purpose of the present invention, those of skill in the art will recognize that to select the whole bag of tricks of an appropriate threshold will produce suitable result.Below threshold value, use first linearity or nonlinear images signal map function that signal map is arrived up-to-date brightness range.The first picture signal mapping function is by solid line 19 expressions.Guarantee like this that below threshold value LCD transmittance or picture carrier increase dim with compensate for backlight.But more than threshold value, a different picture signal mapping function is used to limit brightness value, makes maximum brightness value can not surpass Imax, the i.e. actual maximal value of brightness.The second picture signal mapping function is by shown in the line 20.In fact, be that the brightness range at the following expanded images signal of threshold value dims with compensate for backlight, and block avoiding in the brightness range of the above limited images signal of threshold value.
An example of the present invention and exemplary embodiments have below been described.This is not intended to limit usable range of the present invention or function.Should be appreciated that correction that it will be apparent to those skilled in the art and change should not be counted as exceeding outside the scope of the present invention.
Claims (9)
1. method that on the LCD that illuminates by back light apparatus, cuts down the consumption of energy, this method may further comprise the steps:
Determine to be displayed on the pixel brightness contribution of the picture signal on the LCD,
Determine a clipping point based on the pixel brightness contribution of this picture signal,
Determine the factor that dims backlight based on this clipping point, and dim factor adjustment backlight illumination according to this,
Dim the factor based on this and determine a compensation range and a luminance threshold in compensation range, luminance threshold is about the function of clipping point and less than clipping point,
Below luminance threshold, use the brightness range of the first picture signal mapping function spread signal, more than luminance threshold, use the brightness range of the second picture signal mapping function restricting signal.
2. method according to claim 1, wherein clipping point is between 60% and 99% percentage point of pixel brightness contribution.
3. method according to claim 1, wherein pixel brightness contribution is based on the white gray brightness value of picture signal interior pixel.
4. method according to claim 1, wherein pixel brightness contribution is based on the maximal value of redness, green and the blue channel brightness of picture signal interior pixel.
5. method according to claim 1, wherein dimming the factor is to be determined by following equation:
Wherein CP is the amplitude limit point value, and Imax is the maximal value of pixel intensity, and p is one and is not less than 1 constant that the p value is to determine according to LCD input and output feature, common gamma value near display.
6. method according to claim 1, wherein threshold value is to be determined by following equation:
|FP-CP|＝|CP-Imax|
Wherein FP is a threshold value, and CP is a clipping point, and Imax is the maximal value of pixel intensity.
7. method according to claim 1, wherein a function in the first and second picture signal mapping functions is non-linear.
8. method according to claim 1, wherein second mapping function is a Nonlinear Mapping function.
9. method according to claim 8, the wherein non-linear second picture signal mapping function produces according to pixel brightness contribution.
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| CN101667406B (en) * | 2009-08-14 | 2011-08-31 | 西安龙腾微电子科技发展有限公司 | Backlight dynamical adjusting method of TFT-LCD |
| CN102377956B (en) * | 2010-08-09 | 2014-03-12 | 厦门华侨电子股份有限公司 | Dynamic backlight regulation method of LCD (liquid crystal display) television |
| JP5088408B2 (en) * | 2010-09-22 | 2012-12-05 | 株式会社ニコン | Image processing apparatus, image processing program, and electronic camera |
| CN102820008B (en) * | 2011-06-10 | 2015-04-01 | 晨星软件研发(深圳)有限公司 | Display control circuit and method |
| JP2013238693A (en) * | 2012-05-14 | 2013-11-28 | Sharp Corp | Image display apparatus, image display method, and program |
| KR102023930B1 (en) * | 2012-12-04 | 2019-09-23 | 엘지디스플레이 주식회사 | Liquid crystal display device and method for driving the same |
| CN106448578A (en) * | 2016-12-22 | 2017-02-22 | 广东欧珀移动通信有限公司 | Display screen back light control method, display screen back light control device and computer equipment |
| CN106997750B (en) * | 2017-04-28 | 2020-06-09 | 南京白下高新技术产业园区投资发展有限责任公司 | Terminal screen backlight adjusting method, mobile terminal and computer readable storage medium |
| CN107342056B (en) * | 2017-07-31 | 2019-05-31 | 天津大学 | A kind of region backlight dynamic light adjustment method for shuffling the algorithm that leapfrogs based on improvement |
| JP7075272B2 (en) | 2018-04-20 | 2022-05-25 | キヤノン株式会社 | Image processing equipment, information display equipment, control methods, and programs |
| JP7075271B2 (en) * | 2018-04-20 | 2022-05-25 | キヤノン株式会社 | Image processing equipment, information display equipment, control methods, and programs |
| CN109166533A (en) * | 2018-09-29 | 2019-01-08 | 重庆石墨烯研究院有限公司 | A method of display backlight is adjusted according to image brightness values |
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