EP1576811A1 - Procede de correction de non uniformite des couleurs et appareil a compensation optique et electronique de panneau d'affichage a cristaux liquides - Google Patents

Procede de correction de non uniformite des couleurs et appareil a compensation optique et electronique de panneau d'affichage a cristaux liquides

Info

Publication number
EP1576811A1
EP1576811A1 EP03813263A EP03813263A EP1576811A1 EP 1576811 A1 EP1576811 A1 EP 1576811A1 EP 03813263 A EP03813263 A EP 03813263A EP 03813263 A EP03813263 A EP 03813263A EP 1576811 A1 EP1576811 A1 EP 1576811A1
Authority
EP
European Patent Office
Prior art keywords
recited
optical
uniformity
correction
video
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.)
Withdrawn
Application number
EP03813263A
Other languages
German (de)
English (en)
Inventor
Michael Bakhmutsky
Viktor Gornstein
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.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
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 Koninklijke Philips Electronics NV filed Critical Koninklijke Philips Electronics NV
Publication of EP1576811A1 publication Critical patent/EP1576811A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3179—Video signal processing therefor
    • H04N9/3182—Colour adjustment, e.g. white balance, shading or gamut
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/74—Projection arrangements for image reproduction, e.g. using eidophor
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/205—Neutral density filters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/74—Projection arrangements for image reproduction, e.g. using eidophor
    • H04N5/7416—Projection arrangements for image reproduction, e.g. using eidophor involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal
    • H04N5/7441—Projection arrangements for image reproduction, e.g. using eidophor involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal the modulator being an array of liquid crystal cells

Definitions

  • the present invention relates generally to video processing for color displays, and in particular to a method and apparatus for providing color non-uniformity correction in color displays, including liquid crystal (LC) color displays.
  • color displays including liquid crystal (LC) color displays.
  • Color displays are used in a variety of electronic devices. These include monitors for personal computers, televisions, and other video displays. These displays may be direct-view, cathode-ray tube devices, or projection devices.
  • projection device is based on the optical properties of liquid crystals, such as nematic crystals.
  • These projection devices may include a layer of liquid crystal disposed over a semiconductor transistor array.
  • the array is one of complementary metal-oxide-semiconductor (CMOS) transistors that are used to selectively produce electric fields across the layer of liquid crystal. These electric fields change the polarization angle of the liquid crystal material molecules enabling the modulation of light that traverses this material.
  • the light may be reflected by reflective elements or may be transmitted to the screen. In either case, the modulated light is projected onto a screen by optical elements forming a video image.
  • CMOS complementary metal-oxide-semiconductor
  • LCOS liquid crystal on semiconductor
  • resolution is the number of pixels a screen displays. Often, the resolution is expressed in a particular pixel dimension (e.g. 800 x 600 for many computer monitors). In this example, the monitor has 800 pixels in the horizontal dimension, and 600 pixels in the vertical dimension. Of course, the greater the number of pixels for a given display area, the smaller area of each pixel, and the greater the resolution.
  • Color depth defines how many colors can be displayed on a screen.
  • color depth is described in binary logic (bits).
  • bits Each of the three primary colors used in color displays (red, blue, green) has a number of bits that describes its color depth, or the number of shades of a particular color that may be displayed.
  • the number of colors is normally described via binary exponential notation (e.g., 2 8 (referred to as 8 bit video) for 256 shades of each of the three primary colors).
  • binary exponential notation e.g., 2 8 (referred to as 8 bit video) for 256 shades of each of the three primary colors.
  • the greater the number of color bits the greater the number of shades of the color, and the greater the color depth.
  • the greater the color depth the better is the display quality.
  • While the resolution, brightness, contrast, and color depth may be chosen for a particular desired image quality, certain factors may deteriorate the image quality. For example, differences in both the optical path and the imager (LC panel) characteristics in LCOS projection devices can have deleterious effects on the quality of the projected image.
  • a method comprises correcting video non-uniformity of a liquid crystal display; and correcting optical non-uniformity of an optical system using optical compensation.
  • apparatus for correcting a video non-uniformity comprises an electronic correction device that corrects video non-uniformity of a liquid crystal display; and an optical device that corrects optical non-uniformity of an optical projection system.
  • FIG. 1 is a perspective view of a video correction apparatus in accordance with an exemplary embodiment of the present invention.
  • Fig. 2 is an illustration of bilinear interpolation of correction data in accordance with an exemplary embodiment of the present invention.
  • the present invention relates to a method and apparatus for providing color non-uniformity correction in real-time in LCD projection systems by correcting the video non-uniformity of both the LCD and the optical system.
  • the correction for the LCD panel non-uniformity is effected electronically by a bilinear interpolation technique that does not require the storage of all of the correction data for all the pixels of all the colors in a memory.
  • the correction of optical video non-uniformity of the projection system includes an optical element that decreases the brightness level at regions that exceed the desired brightness. Beneficially, video signal clipping and its deleterious affects are substantially avoided by virtue of the exemplary embodiments.
  • Fig. 1 shows an LCD apparatus 100 in accordance with an exemplary embodiment.
  • An LCD 101 is connected to an electronic correction device 102, which provides the electronic correction of video non-uniformity due to LCD panel non-uniformity.
  • a video input 107 is coupled to the electronic correction device 102.
  • the output of the electronic correction devicel02 is input to an LCD driver 108, which is connected to the LCD 101 as shown.
  • the electronic correction is illustratively effected by a bilinear interpolation correction technique that is described in further detail herein.
  • the electronic correction device 102 includes the required elements to effect the calculation of the correction data (e.g., an interpolator) and to control the LCD in order to alter the video level at each pixel as needed.
  • the output 105 from the LCD is incident on an optical element 103, which is illustratively the optical inverse of the projection system's non-uniformity distribution.
  • the optical element may be a photographic negative of the screen taken when the video levels applied are uniform gray with no presence of LCD 101 in the system. In this manner, the light 105 is transmitted through the optical element 103, and emerges as light 106 that is incident on the screen.
  • the level of correction is increased, and the image quality at the image screen 104 is enhanced.
  • clipping of the video signal is substantially avoided.
  • the electronic device 102 provides electronic color non-uniformity correction by video modification.
  • the brightness distributions for each pixel at a number of video levels are evaluated individually for each color path.
  • not all pixels are evaluated. Rather, a limited number of pixels located at a grid of points spaced with respect to each other by a predetermined number of pixels both vertically and horizontally are evaluated. Differences between the actual and the nominal brightness for the particular video level under evaluation are calculated and stored as correction coefficients.
  • the color correction data is obtained for a variety of color levels. In an exemplary embodiment, four correction data are stored in a memory device in such a manner that they are readily available for computations.
  • Fig. 2 shows conceptual view of a bilinear interpolation scheme in accordance with an exemplary embodiment of the present invention.
  • the interpolation block 201 includes four measured and stored correction coefficients (202, 203, 204 and 205) at points representative of points on an image screen.
  • the correction coefficient for any interpolated point on a map of correction data 200 (e.g., interpolated point 205) is illustratively determined by the electronic correction device 102 by a technique described in U.S. Patent Application Serial Number 10/179,319, entitled “Color Non-Uniformity Correction Method and Apparatus," to Michael Bhatmustsky, and filed on June 24, 2002.
  • the disclosure of this application is incorporated herein and for all purposes.
  • the video level of a particular pixel is at 190, and the correction coefficient is determined to be 100, applying this level of correction exceeds the maximum video level of 255. As a result the video signal will be clipped, and there will be harmonics in the signal that are manifest as undesirable artifacts on the image display.
  • the amount of electronic correction required from the electronic correction device 200 is reduced, which means lower level of electronic correction and less clipping in video processing.
  • the amount of electronic correction relied upon is limited to avoid clipping the video signal.
  • a portion of the compensation needed to achieve the higher levels of correction, which can cause clipping in an all-electronic correction method is effected via the electronic correction device, while the remaining portion is exacted using the optical element 103.
  • color non-uniformity is corrected by a combination of the electronic correction device, which controls the LCD panel, and the optical element, which provides optical correction. Accordingly, by not requiring the electronic correction device to correct for video non-uniformity from both the LCD panel and the optical system, video clipping is avoided, and the overall correction capability is increased.
  • the optical element 103 is usefully the inverse of the image screen 104, generally resulting from a gray level uniform video without the LCD in the system, although variations are certainly possible. Illustratively, three separate inverse images are used (i.e., one per video color). Alternatively, one inverse image may be used to compensate for overall brightness non-uniformity, with the remaining correction exacted electronically via the electronic correction device 102.
  • the optical element 103 may be a type of photographic negative. However, it is noted that the optical element 103 may be fabricated by image processing techniques, to include digital photography and other digital imaging techniques. Finally, it is noted that optical element 103 may be a color negative (inverse image) of the image screen; although three black-and-white negatives may be used in the paths of the primary colors.
  • the optical element 103 may be fabricated by installing mirrors instead of the LCD panel in the projection system in which the LCD is used.
  • the optical element may be tailored to the particular projection system, or a plurality of negatives for a given type of projection system could be made from a production version thereof. In the former case, the image quality is better; and in the latter the mass production capabilities are advantageous. Regardless of the degree of correction achieved by the optical element 103, the remaining correction is effected using the electronic correction device 102 and the technique(s) described above.
  • the compensation for non-uniformities due to the optical system by the optical element 103 illustratively is effected as follows.
  • the output from the LCD is projected light onto the image screen with the video correction being manifest in the intensity of the light at each pixel on the image screen. As referenced above, this may result in an increase in the compensation beyond the video level limits. Alternatively, the intensity of the light may be too low due to an under-correction in the interpolation method described above. However, by capturing the inverse (negative) of the image screen in the optical element 103, each pixel is tempered to a certain correction.
  • pixels that are too bright due to over-correction are transmitted through a correspondingly 'darker' portion of the optical element; while pixels that are under-corrected so that the intensity level is too low on the image screen are transmitted through a region of the optical element that is the optical inverse of this low level, and the corresponding pixel has a greater intensity at the screen.
  • the optical element 103 also corrects the color intensity of each pixel (e.g., the optical element 103 is a color negative or inverse of the screen image). It is further noted that the optical element alone cannot achieve high- quality correction because it is not able to provide the non-linear video compensation. To wit, the optical element 103 will correct all levels the same way. However, in combination with the electronic correction device 102, the optical element provides suitable video correction.
  • the correction technique and apparatus of the exemplary embodiments is advantageous for a variety of reasons. For example, because the electronic correction/compensation does not have to correct for errors in the optical system, the required range of video modification can be reduced. This eliminates the problem of clipping of the corrected video signal. Moreover, because the range of video modification is reduced, the computational accuracy of the correction is enhanced.
  • Another benefit of an exemplary embodiment is realized in manufacturing. Because of the combination of optical and electronic correction, the correction levels in such a system are lower, and the correction margins are subsequently higher than in known systems. This can solve more severe LCD problems and lead to a significant increase in the LCD panel yields.

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Liquid Crystal Display Device Control (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Liquid Crystal (AREA)
  • Polarising Elements (AREA)
  • Projection Apparatus (AREA)
  • Transforming Electric Information Into Light Information (AREA)

Abstract

L'invention concerne un procédé et appareil permettant de corriger une non uniformité vidéo dans un système de projection. Ledit procédé consiste à corriger la non uniformité vidéo d'un affichage à cristaux liquides et à corriger la non uniformité optique d'un système optique par compensation optique.
EP03813263A 2002-12-18 2003-12-11 Procede de correction de non uniformite des couleurs et appareil a compensation optique et electronique de panneau d'affichage a cristaux liquides Withdrawn EP1576811A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US43459402P 2002-12-18 2002-12-18
US434594P 2002-12-18
PCT/IB2003/005913 WO2004056103A1 (fr) 2002-12-18 2003-12-11 Procede de correction de non uniformite des couleurs et appareil a compensation optique et electronique de panneau d'affichage a cristaux liquides

Publications (1)

Publication Number Publication Date
EP1576811A1 true EP1576811A1 (fr) 2005-09-21

Family

ID=32595293

Family Applications (1)

Application Number Title Priority Date Filing Date
EP03813263A Withdrawn EP1576811A1 (fr) 2002-12-18 2003-12-11 Procede de correction de non uniformite des couleurs et appareil a compensation optique et electronique de panneau d'affichage a cristaux liquides

Country Status (7)

Country Link
EP (1) EP1576811A1 (fr)
JP (1) JP2006510931A (fr)
KR (1) KR20050084308A (fr)
CN (1) CN1726703A (fr)
AU (1) AU2003303006A1 (fr)
TW (1) TW200501043A (fr)
WO (1) WO2004056103A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5558001B2 (ja) * 2005-11-09 2014-07-23 コーニンクレッカ フィリップス エヌ ヴェ 減衰フィルタを均質化する機能を持つ表示デバイス
CN103037189B (zh) * 2012-12-05 2016-03-09 江苏清投视讯科技有限公司 一种实现多个投影整体输出大屏画面视频图像的方法
CN104700797B (zh) * 2015-02-12 2017-11-10 宏祐图像科技(上海)有限公司 一种液晶显示器一致性校正系统及方法
JP6744791B2 (ja) * 2015-11-11 2020-08-19 株式会社Ｊｏｌｅｄ 表示装置、表示装置の補正方法、表示装置の製造方法、および表示装置の表示方法

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1953471A (en) * 1932-01-05 1934-04-03 Electrical Res Prod Inc Optical instrument
JPS4980252U (fr) * 1972-10-28 1974-07-11
JP3719317B2 (ja) * 1997-09-30 2005-11-24 ソニー株式会社 補間方法、補間回路、画像表示装置
EP1046933B1 (fr) * 1999-04-21 2003-09-10 Asulab S.A. Dispositif optique à gradient d'absorption et à filtrage spectral sélectif ainsi qu'objectif et appareil de prise d'images munis d'un tel dispositif
NO310490B1 (no) * 2000-02-09 2001-07-09 Johan Henrik Litleskare Digital korreksjonsmodul for videoprojektor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2004056103A1 *

Also Published As

Publication number Publication date
WO2004056103A1 (fr) 2004-07-01
JP2006510931A (ja) 2006-03-30
KR20050084308A (ko) 2005-08-26
CN1726703A (zh) 2006-01-25
AU2003303006A1 (en) 2004-07-09
TW200501043A (en) 2005-01-01

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