EP2312567A1 - Correction de luminance pour affichages à cristaux liquides avec modulation de rétroéclairage - Google Patents

Correction de luminance pour affichages à cristaux liquides avec modulation de rétroéclairage Download PDF

Info

Publication number
EP2312567A1
EP2312567A1 EP20100179819 EP10179819A EP2312567A1 EP 2312567 A1 EP2312567 A1 EP 2312567A1 EP 20100179819 EP20100179819 EP 20100179819 EP 10179819 A EP10179819 A EP 10179819A EP 2312567 A1 EP2312567 A1 EP 2312567A1
Authority
EP
European Patent Office
Prior art keywords
intensity
lcd
dimming
backlight
transmittance
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP20100179819
Other languages
German (de)
English (en)
Inventor
Emrah Tasli
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Vestel Elektronik Sanayi ve Ticaret AS
Original Assignee
Vestel Elektronik Sanayi ve Ticaret AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Vestel Elektronik Sanayi ve Ticaret AS filed Critical Vestel Elektronik Sanayi ve Ticaret AS
Publication of EP2312567A1 publication Critical patent/EP2312567A1/fr
Ceased legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G09G3/342—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
    • G09G3/3426—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines the different display panel areas being distributed in two dimensions, e.g. matrix
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/0646—Modulation of illumination source brightness and image signal correlated to each other

Definitions

  • This invention relates to a method and a system for improving the contrast in displays illuminated by individually controlled led blocks.
  • the Led blocks placed behind the LCD layer of the displays are controlled individually to locally dim or boost the illumination level such that the local characteristics of the image can be better visualized.
  • the major advantage of this approach lays in a remarkable improvement in the contrast performance of the display where a local dimming of the Leds enables minimal light leakage thorough the LCDs.
  • the proposed method describes how local LCD pixel values are enhanced (compensated) after the local variation of illumination level.
  • the proposed method provides a solution for LCD compensation for any given Led driving intensities.
  • the objective metric used for performance comparison is used as the main reference algorithm for performing the correct compensation.
  • the method mathematically simulates the screen intensity and depending on the accurate display measurements (Led point spread function (PSF) and LCD sweep characteristics) it provides a compensation of the LCD pixels.
  • initial LCD value is used to compute the initial reference intensity (1)
  • the Led screen intensity is used to find the intensity after local dimming (2)
  • the updated LCD values are defined (3).
  • Conventional LCD displays are formed by a constant and uniform backlight and a LCD panel.
  • the backlight supplies constant light source and liquid crystal cells work as switches controlling the brightness of corresponding pixels.
  • Conventional LCDs suffer the drawback of poor image contrast due to the light leakage from liquid crystals.
  • Led Backlight Displays There is an increasing interest in the Led Backlight Displays in the market due to the notable performance increase and energy saving characteristics.
  • Led Backlight can be created by using the temporal characteristics of the image or by using different scanning methods to achieve better motion picture performance. These benefits encouraged researchers to study on methods to utilize this technology to achieve higher image quality using the conventional LCD characteristics.
  • the brightness of the pixel (the amount of light passing through each LCD) perceived by the viewer is the result of the combined effect of backlight intensity, filter transmittance and LCD level in the display.
  • the ratio of minimum and maximum light leakage (corresponding to the 0 and 255 values of LCD) is constant for a constant backlight.
  • Led Backlight the minimum light leakage level may be decreased to lower levels; hence boosting up the contrast performance of the display.
  • the benefits come with difficulties in deciding the correct values of the Led backlight levels and LCD values corresponding to updated backlight luminance. This represents a remarkable drawback of the solutions currently available on the market.
  • the proposed method utilizes the main idea of making the pixel brightness after the local dimming equal to the reference brightness for the three main colour channels R, G and B channels and hence compensating the local decrease in the intensity by an increase in the LCD transmittance.
  • the decrease in the dark regions (where a soft thresholding idea is employed) is not compensated in order to realize the minimal light leakage and a real black screen.
  • I Full BL Full x CV Full / 255 ⁇
  • the parameterization of the intensity output of a display presents quite some difficulties and it is not a straightforward computing by employing the above equations. The empirical measurements show that this rough estimate deviates from the real values.
  • the compensation methods in the prior art all depend on the compensation in the Y domain which mostly contains the intensity information (some use also the idea to compensate in R, G and B channels independently).
  • the main idea stems from the basic fact that the increase in the Y value of the image causes an increase in the output intensity, and it can be used to compensate the effect of the backlight dimming. But since no gamma curve is able to represent the display characteristics without error, the assumption produces a solution which, de facto it is only a rough estimation of the correct solution. Since our method does not use a mathematical model to estimate the display parameters, (but uses only the experimental outputs) it ends up with the correct value in order to reach the real required intensity, overcoming in this way the limitations of the approaches of the state of the art.
  • Another aspect of the present invent relates to varying the LCD transmittance to keep the intensity value of a pixel faithful to the intensity value of the image to be displayed.
  • Another aspect of the present invention relates to a backlighting system formed of a plurality of backlighting areas, each controlled by relevant backlighting driving units and dimming control units.
  • Another aspect of the present invention relates to adapting the LCD transmittance in accordance with the values of the Point Spread Function.
  • Another aspect of the present invention relates to employing an L 2 norm to measure the error between the required pixel intensity and the intensity changed by dimming, so to vary adequately the LCD transmittance for compensating such error.
  • Another aspect of the present invention relates to the usage of look-up tables for changing the transmittance of the LCD panel.
  • Another aspect of the present invention relates to the usage of predetermined thresholds to recover the intensity level.
  • the invention is directed to a system and method for improving the faithfulness of images to be used in any kind of display (or projector) whose backlight can be locally enhanced in order to obtain better contrast characteristics.
  • the method uses the predetermined Led driving values to calculate the led intensity on the display and then enhance the LCD pixels to compensate for the possible image deterioration due to misrepresented low pass behaviour caused by a little number of Leds (possible configuration 16x8)
  • the invention uses the information of carefully measured display characteristics: the display sweep intensities for R, G and B channels, the PSF (Point Spread Function) and the placement of the Led groups in the display.
  • Figure 1 shows the grey level sweep intensity levels for a conventional display with static contrast ratio 800:1. Such sweep intensity is aimed to keep the maximum value constant and to decrease the minimum value which is the light leakage, namely reduce the intensity to a minimum value when the LCD values are set to 0.
  • Diagrams of the individual intensity values for R, G and B channels, parameters which play a major role in the present method, are given in figures 4 , 5 and 6 .
  • the present invention can use the Led value estimates from any algorithm proposed in the literature.
  • the estimated Led intensities are used to produce (more precisely to simulate) the display intensity using the PSF of the display. It is worth noting that the PSFs of the Led groups in different parts of the display may vary due to the reflections differences in different display areas (ie, corners may have more reflection components and hence produce higher intensity distribution).
  • Initial step of the algorithm consists in simulating the Led intensity on the display when the Leds are driven with the estimated values.
  • This simulation can be any kind of simulation already available, and it is of paramount importance that it is as accurate as possible.
  • Figure 3 shows a simulation result for the display intensity when only one of the Leds in the middle of the screen is driven with 255 (white) while others are assigned to 0 (black).
  • the superposition principle intensity of light is cumulatively added
  • the final intensity distribution is then used to calculate how much the intensity has diverged from the reference intensity.
  • an objective metric for quality assessment of the final solution.
  • the Error is calculated before and after the compensation. Since it is possible to calculate the error for different methods, regardless which is the estimation method employed, it provides an objective metric to judge the algorithm. As stated before, since this method proposes an objective measurement dependent approach, it suffices the minimum error criterion.
  • the following step is to enhance the LCD pixel values so that the reference intensity is preserved.
  • the intensity measurements for R, B and G channels which are plotted in figures 4 , 5 and 6 are used as look up tables to decide on the update values corresponding to the required intensity. For each pixel on the screen the Led intensity measurement is combined with the original LCD value.
  • the initial intensity Linit is computed with the condition that all Leds are assigned to 255 (max value). After the local dimming algorithm the Led and intensity values have been updated and the light leakage through each pixel (for the three components) has changed. Using the look up table the new values are obtained.
  • the method is described in figure 8 .
  • the bold continuous line shows conventional grey level sweep intensity where the dotted line represents an updated intensity after the Led value estimation (a local dimming of 50% is shown in the example).
  • the intensity level corresponding to the initial LCD values are computed using the Look Up Tables (LUTs) for three channel components (1); the intensity has then to be compensated with the updated Led values (2); finally the updated LCD level is obtained using the LUTs. This operation is repeated for each channel R, G, B.
  • LUTs Look Up Tables
  • a major problem that may arise in any kind of compensation method is clipping.
  • Clipping is the situation when more than one (usually 10 to 30) initial LCD values (say from 230 to 255) are assigned to 255 after compensation.
  • the reason is that the initial intensity with all Leds at full brightness may not be compensated with the updated Led brightness (ie. initial LCD level of 200 may produce a brightness of 400 cd/m2, when the updated Led values are driven, the same intensity level may be reached with LCD value of 255).
  • all the LCD values from 200 to 255 may be assigned to 255, which cause a great loss of detail in the bright regions.
  • This problem can not be tolerated; hence a soft thresholding idea is used with a gradual decrease in the required intensity as the LCD level goes above the given threshold.
  • intRef>thrhigh intRefUpd intRef * 1 - intRef - thrHigh / maxInt - thrHigh
  • a similar approach (mirrored to reflect the behaviour at the low level of the scale of the intensities to be thresholded) can be used for the dark pixels which may also need special attention.
  • the pixels below the given threshold should not necessarily reach the initial intensity; on the contrary they should decrease in order to achieve better contrast performance.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Liquid Crystal Display Device Control (AREA)
EP20100179819 2009-10-02 2010-09-27 Correction de luminance pour affichages à cristaux liquides avec modulation de rétroéclairage Ceased EP2312567A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
TR2009/07513A TR200907513A2 (tr) 2009-10-02 2009-10-02 LCD ekranlar için yeğinlik düzeltimi.

Publications (1)

Publication Number Publication Date
EP2312567A1 true EP2312567A1 (fr) 2011-04-20

Family

ID=43244546

Family Applications (1)

Application Number Title Priority Date Filing Date
EP20100179819 Ceased EP2312567A1 (fr) 2009-10-02 2010-09-27 Correction de luminance pour affichages à cristaux liquides avec modulation de rétroéclairage

Country Status (2)

Country Link
EP (1) EP2312567A1 (fr)
TR (1) TR200907513A2 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104112433A (zh) * 2013-04-22 2014-10-22 华为技术有限公司 一种图像补偿方法及装置
CN110189714A (zh) * 2019-06-25 2019-08-30 京东方科技集团股份有限公司 具有区域调节背光的显示方法及装置、电子设备、介质
US10726801B2 (en) 2015-04-17 2020-07-28 Microsoft Technology Licensing, Llc Display defect compensation with localized backlighting

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080180466A1 (en) * 2004-07-27 2008-07-31 Dolby Canada Corporation Rapid image rendering on dual-modulator displays
US20090141178A1 (en) * 2007-11-30 2009-06-04 Kerofsky Louis J Methods and Systems for Backlight Modulation with Scene-Cut Detection
US20090201245A1 (en) * 2007-12-10 2009-08-13 Ryosuke Nonaka Liquid crystal display apparatus

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080180466A1 (en) * 2004-07-27 2008-07-31 Dolby Canada Corporation Rapid image rendering on dual-modulator displays
US20090141178A1 (en) * 2007-11-30 2009-06-04 Kerofsky Louis J Methods and Systems for Backlight Modulation with Scene-Cut Detection
US20090201245A1 (en) * 2007-12-10 2009-08-13 Ryosuke Nonaka Liquid crystal display apparatus

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
FANG-CHENG LIN ET AL.: "Dynamic Backlight Gamma on High Dynamic Range LCD TVs", JOURNAL OF DISPLAY TECHNOLOGY, June 2008 (2008-06-01), pages 139 - 146
HIGH CONTRAST LCD TV USING ACTIVE DYNAMIC LED BACKLIGHT SID SYMPOSIUM DIGEST OF TECHNICAL PAPERS, vol. 38, no. 1, May 2007 (2007-05-01), pages 1336 - 1338
SID SYMPOSIUM DIGEST OF TECHNICAL PAPERS, vol. 37, June 2006 (2006-06-01), pages 1242 - 1245

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104112433A (zh) * 2013-04-22 2014-10-22 华为技术有限公司 一种图像补偿方法及装置
CN104112433B (zh) * 2013-04-22 2016-06-29 华为技术有限公司 一种图像补偿方法及装置
US10726801B2 (en) 2015-04-17 2020-07-28 Microsoft Technology Licensing, Llc Display defect compensation with localized backlighting
CN110189714A (zh) * 2019-06-25 2019-08-30 京东方科技集团股份有限公司 具有区域调节背光的显示方法及装置、电子设备、介质

Also Published As

Publication number Publication date
TR200907513A2 (tr) 2011-04-21

Similar Documents

Publication Publication Date Title
CN103502881B (zh) 双lcd显示器、控制器、产生驱动信号的方法
US9601062B2 (en) Backlight dimming method and liquid crystal display using the same
US9595229B2 (en) Local dimming method and liquid crystal display
US8890900B2 (en) Liquid crystal display and method of local dimming thereof
KR101588901B1 (ko) 액정표시장치 및 그의 로컬디밍 제어방법
TWI436344B (zh) 補償像素資料之方法及液晶顯示器
US8810611B2 (en) Liquid crystal display device
CN101383132B (zh) 液晶显示方法
US8400385B2 (en) Method for enhancing an image displayed on an LCD device
KR20110060268A (ko) 액정표시장치 및 그의 로컬디밍 제어방법
KR20110068151A (ko) 액정표시장치와 그 구동 방법
KR20120036477A (ko) 액정표시장치 및 그의 로컬디밍 제어방법
CN102472904A (zh) 液晶显示装置和光源控制方法
US20120086740A1 (en) Liquid Crystal Display Device And Light Source Control Method
Chen et al. 39.3: Locally Pixel‐Compensated Backlight Dimming for Improving Static Contrast on LED Backlit LCDs
EP2312567A1 (fr) Correction de luminance pour affichages à cristaux liquides avec modulation de rétroéclairage
KR20120038180A (ko) 액정표시장치
US8983220B2 (en) Error diffusion method and liquid crystal display using the same
Burini et al. Image dependent energy-constrained local backlight dimming
KR20110061173A (ko) 액정표시장치 및 그의 로컬디밍 제어방법
KR102438248B1 (ko) 디밍 제어회로, 및 이를 포함한 액정표시장치와 그 디밍 제어방법
WO2009086742A1 (fr) Procédé et appareil d'amélioration d'une image affichée sur un dispositif lcd
Cheng et al. P‐56: An Advanced High Dynamic Range Display Technology with Power Saving Algorithm of Adaptive Real‐time Controllable Backlight

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR

AX Request for extension of the european patent

Extension state: BA ME RS

17P Request for examination filed

Effective date: 20111003

17Q First examination report despatched

Effective date: 20130610

APBK Appeal reference recorded

Free format text: ORIGINAL CODE: EPIDOSNREFNE

APBN Date of receipt of notice of appeal recorded

Free format text: ORIGINAL CODE: EPIDOSNNOA2E

APBR Date of receipt of statement of grounds of appeal recorded

Free format text: ORIGINAL CODE: EPIDOSNNOA3E

APAF Appeal reference modified

Free format text: ORIGINAL CODE: EPIDOSCREFNE

APBT Appeal procedure closed

Free format text: ORIGINAL CODE: EPIDOSNNOA9E

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN REFUSED

18R Application refused

Effective date: 20190409