WO2005022925A1 - Procede et systeme de commande de contraste dynamique pour un systeme d'affichage - Google Patents

Procede et systeme de commande de contraste dynamique pour un systeme d'affichage Download PDF

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Publication number
WO2005022925A1
WO2005022925A1 PCT/IB2004/051427 IB2004051427W WO2005022925A1 WO 2005022925 A1 WO2005022925 A1 WO 2005022925A1 IB 2004051427 W IB2004051427 W IB 2004051427W WO 2005022925 A1 WO2005022925 A1 WO 2005022925A1
Authority
WO
WIPO (PCT)
Prior art keywords
light
brightness
display system
input signal
image input
Prior art date
Application number
PCT/IB2004/051427
Other languages
English (en)
Inventor
Adrianus J. S. M. De Vaan
Original Assignee
Koninklijke Philips Electronics N.V.
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 N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2005022925A1 publication Critical patent/WO2005022925A1/fr

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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
    • 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]
    • H04N9/3191—Testing thereof
    • H04N9/3194—Testing thereof including sensor feedback
    • 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
    • G09G2320/0653—Controlling or limiting the speed of brightness adjustment of the illumination source

Definitions

  • This invention relates to a light modulating display system comprising light control means for dynamically controlling contrast of a displayed image.
  • a display system such as described in European patent application no. EP 1 170 959, utilises a light shielding member between a lens array and a polarisation conversion element array for arbitrarily reducing the quantity of the incident light on the polarisation splitting films constituting the polarisation conversion element. Further, the European patent application describes how the light shielding member is driven by an existing drive mechanism, however, the European patent application provides no solution for dynamically controlling brightness of the projected image. Further, a projection system, such as described in American patent application no. US 2001/0015775, comprises luminous flux quantity adjusting means adapted to adjust a light quantity caused by an effective luminous flux on the light valve, which adjusting means are disposed within or near the integrator unit.
  • a display system such as described in American patent application no. US 2002/0105621, which is considered the closest prior art, comprises a movable stripe stop disposed at a position, whereat an integrator light source image is projected, is stopped down to make the amount of projection light small, thereby achieving that the projection of unnecessary leak light or scattered light from a light modulating element is suppressed and a firm black display is presented.
  • the movable stripe stop is controlled by a controller generating a control signal in accordance with the luminance level of an input image signal.
  • An object of the present invention is to provide a system and method for dynamically controlling contrast of light- valve based projection systems. It is a further object of the present invention to provide a system and method for accurately addressing brightness levels in a projected image. It is a further object of the present invention to provide a system and method for reflecting light at light blocking grids in a projection system in a controlled way.
  • a particular advantage of the present invention is provision of a projected image without visible display artefacts like visible flicker.
  • a further advantage of the present invention is provision of a system and method providing high brightness capabilities in combination with having an improved lifetime expectancy.
  • a particular feature of the present invention relates to shielding means having a shape so as to limit degradation problems of the housing and unwanted reflection of light back into the light-source.
  • the display system according to the first aspect of the present invention ensures a fast response time by simultaneously minimizing visible flicker in the image input signal, e.g. a video stream, by optimizing for a fast response time to increase brightness of output and a slower response time to reducing brightness of output.
  • the display system according to the first aspect of the present invention may comprise a direct view LCD system, or, alternatively, a projection display system.
  • the light control means according to the first aspect of the present invention may be adapted to control the brightness of the light incident on the light modulation means by means of controlling a power feed to the light source. Alternatively, the light control means may be adapted to control the brightness of the light incident on the light modulation means by means of controlling a LCD shutter for adjusting brightness of the light.
  • the light control means may be adapted to control the brightness of the light incident on the light modulation means by means of controlling a diaphragm for adjusting brightness of the light.
  • the light control means may be adapted to control the brightness utilising any combination of the above alternatives.
  • the light control means according to the first aspect of the present invention may operate in a fast opening action when increasing brightness is identified in the image input signal, and may operate in a slow opening action when decreasing brightness is identified in the image input signal. Since the response time of the human eye at lower brightness levels is limited compared to the response time of the human at higher brightness levels, the response time for decreasing the brightness is advantageously designed to be greater than the response time for increasing the brightness.
  • the light control means according to the first aspect of the present invention may operate in a fast opening action with a first response time in the range of 10 to 30 ms or 15 to 25 ms, such as a first response time of 20 ms. Further, the light control means may operate in a slow opening action with a second response time in the range of 400 to 600 ms or 450 to 550 ms, such as a second response time of 500 ms. By selecting response times within these ranges visible flicker is effectively prevented.
  • the display system may further comprise a light sensor for measuring brightness of the light transferred to the light modulation means, the light sensor may be adapted to generate a signal and may be adapted to communicate the signal to the light control means, and an amplifier unit controlled by the light control means may be adapted to amplify the image input signal in accordance with the signal.
  • the light sensor and light control means in combination provide brightness regulation determining the maximum brightness levels of the display system, while simultaneously providing a full dynamic range of the light modulation means by amplifying the image input signals.
  • generally prior art display systems of these types are prone to visible flicker due to the brightness regulation mechanism.
  • the integrator means according to the first aspect of the present invention may comprise a first integrator plate and a second integrator plate axially shifted relative to light path from the light source and the light modulation means.
  • a diaphragm may be disposed in the light path between the first and second integrator plates. The regulatory function of the diaphragm is thus moved forward on the light path in the display system thus enabling dynamic optimization of the contrast of the image presented.
  • the light sensor according to the first aspect of the present invention may be disposed on the light path between the diaphragm and the light modulation means. Hence the light sensor senses the light exiting the diaphragm and enables the light control means to select appropriate amplification of the input image signal so as to continuously achieve an optimal contrast.
  • the light control means may comprise conversion means for converting the image input signal to a digital image data, a processor for determining brightness of the digital image data and adapted to generate a brightness signal and a curve select signal, a dimming driver for operating a light shutter between an open and closed position in accordance with the brightness signal received from the processor, a peak selection unit for determining maximum brightness of the digital image data and adapted to generate a maximum brightness signal, and an amplifier unit for amplifying the image input signal in accordance with the curve select signal received from the processor and the maximum brightness signal received from the peak selection unit.
  • This configuration avoids the requirement of having an exact characterization of the diaphragm and that higher tolerances for the diaphragm are allowed.
  • the display system may comprise an amplifier unit adapted to receive the image input signal and to amplify the image input signal as a function of the brightness of the light incident on the light modulation means.
  • the light modulation means may comprise panel means driven by the image input signal amplified by the amplifier unit.
  • the panel means such as panel displays, are driven by voltage signals and are adapted to modulate the colours "Red", "Green” and “Blue” of the light so as to generate an image to be presented on a surface.
  • An object of the light control means may be in an application to drive a light source in a back-light system of a direct view LCD display so as to introduce dynamic contrast in such a display device.
  • the processor according to the first aspect of the present invention may be adapted to generate a first brightness signal for establishing the first response time and a second brightness signal for establishing a second response time.
  • the processor thereby minimizes the problems relating to visible flicker.
  • the light shutter according to the first aspect of the present invention may comprise a first mask closest to the light source and a second mask furthest away from the light source, which first and second masks are movable in direction perpendicularly to the light path and relative to one another thereby establishing a open mask allowing the light through and a closed mask stopping the light.
  • the first mask may, in addition, comprise a structured surface facing the light source, which structured surface may comprise a plurality of miiTors adapted to reflect incident light away from the light source.
  • the dimming driver may comprise a electro-mechanical transducer.
  • the electro-mechanical transducer may comprise any type of stepping motor or precision actuators.
  • the dimming driver may comprise a fast reacting mechanism for opening the light shutter and a slow reacting mechanism for closing the light shutter.
  • the fast reacting mechanism may comprise a spring element and the slow reacting mechanism may comprise an electro -magnet.
  • a light control unit for dynamically controlling contrast of an image displayed in accordance with an image input signal characterized in that being adapted to control brightness of a light incident on a light modulation means in accordance with a brightness signal in said image input signal and to control brightness of said light incident on said light modulation means in a fast and slow action, such that said brightness of said light incident on said light modulation means is controlled in a fast action when increasing brightness is identified in said image input signal and is controlled in a slow action when decreasing brightness is identified in said image input signal.
  • the control unit according to the second aspect of the present invention may incorporate any features of the light control means according to the first aspect of the present invention.
  • a method for dynamically controlling contrast of an image displayed in accordance with an image input signal in a display system according to the first and second aspect of the present invention comprising: (a) determining brightness of said image input signal and generating a brightness signal, (b) measuring resultant brightness of light incident on said light modulation means by means of a light sensor, (c) amplifying said image input signal in accordance with said brightness signal and forwarding said amplified image input signal to said light modulating means, and (d) adjusting brightness of said light incident on said light modulation means in a fast and slow action, such that said brightness of said light incident on said light modulation means is controlled in a fast action when increasing brightness is identified in said image input signal and in a slow action
  • Figure 1 shows a schematic diagram of a projection system according to a first embodiment of the present invention
  • Figure 2 shows a schematic diagram of a part of the projection system according to a second embodiment of the present invention.
  • Figure 1 shows a schematic diagram of a projection system designated in its entirety by reference numeral 100 and comprising an optical system 102 and a image processing system 104.
  • the optical system 102 comprises a projection lamp 106 supplying the light illustrated by dashed lines 108.
  • the light 108 is received at a first integrator plate 110 and a second integrator plate 112 for focussing and gathering the light 108.
  • a masking unit 114 comprising a first mask 116 and second mask 118 is disposed between the first and second integrator plate 110, 112.
  • the term mask is in this context to be construed as a grid or a net enabled in cooperation with another corresponding mask to block light in one position and to allow light through in a second position.
  • the cooperation may be constituted by shifting the first and second mask 116 and 118 in the plane perpendicularly to normal of the first and second masks 116, 118.
  • the mask may comprise apertures which are rectangular, quadratic, circular, elliptical or any combination thereof.
  • the shifting operation of the first and second mask 116 and 118 is accomplished by a mask driver 120, which may be any electro-mechanic transducer device such as a stepping motor, precision actuator, electro-magnet, mechanical spring element or any combination of, or any controllable mechanical actuator.
  • the mask driver 120 may advantageously have a first response time for closing and a second response time of opening the mask unit 114.
  • the response time may be controlled mechanically by for example having a spring element assisting in one direction and opposing in the other direction.
  • the variance of the response time is particularly advantageous in connection with the projection system 100 since it reduces flicker on the image to be presented.
  • Focussed light 122 exiting the second integrator plate 118 is received by a polarisation array 124 polarizing the incoming light and providing polarized light 126 to a first lens 128 focussing the polarized light 126 onto a first reflector 130.
  • the first reflector 130 partly reflects the focused polarized light to a mirror array 132 for separating the polarized light into colours “Red”, “Green” and “Blue” and partly reflects or transmits the polarized light to a light sensor 134 measuring the luminance or brightness of the polarized light and generating a brightness signal.
  • the reflector array 132 comprises a first reflector 136 for reflecting other than “Red” light component 138, a second reflector 140 for reflecting other than “Green” light component 142, and a third reflector 144 for reflecting "Blue” light component 146.
  • the "Red” light component 138, the "Green” light component 142, and the “Blue” light component 146 each are communicated to display panels 148a, 148b, 148c modulating the polarized light in accordance with a desired image input signal.
  • the polarized and encoded light is then received in a recombination prism 150 gathering each of the polarized and encoded light beams from each of the coloured light paths, i.e.
  • the prism 150 may be implemented in a wide variety of ways, however in the presently preferred embodiment of the present invention the prism 150 is implemented by a dichroic cube.
  • the image processing system 104 comprises a control module designated in its entirety by reference numeral 154 for controlling the brightness and contrast of the image to be projected by the optical system 102.
  • the image processing system 104 comprises an image provider 156 such as a DVD player.
  • the image provider 156 provides an image input signal constituted by a "Red” colour image signal 158, a “Green” colour image signal 160, and a “Blue” colour image signal 162, which image input signal is communicated to an amplifier array 164 and to input conversion elements 166 of the control module 154,
  • the input conversion elements 166 convert the respective "Red” colour image signal 158, the "Green” colour image signal 160, and the "Blue” colour image signal 162 into a processor readable format, such as a digital format, and communicates the processor readable format of the colour image signals 158, 160 and 162 to a processor 168 and a peak selection unit 170.
  • the peak selection unit 170 determines maximum brightness of converted processor readable format of the "Red” colour image signal 158, the "Green” colour image signal 160, and the “Blue” colour image signal 162 and generates a maximum brightness signal 172.
  • the processor 168 performs a histogram analysis on the processor readable format of the colour image signals 158, 160 and 162 on the basis of a gamma signal 159, response time signal 161 and a slope reference signal 163, and generates a curve select signal 174. Further, the processor 168 receives the brightness signal generated by the light sensor 134 and utilises the brightness signal to provide a control brightness signal to the mask driver 120 amplifier array 164.
  • the processor 168 controls the mask driver 120, so as to reduce or increase the brightness of the focussed light 122, and the processor selects an appropriate brightness of the focussed light 122 in accordance with the image input signal presented to the processor 168 in a readable format.
  • the control module 154 comprises a local pixel gain unit 176 receiving the curve select signal 174 from the processor 168 and receiving the maximum brightness signal 172 from the peak selection unit 170.
  • the local pixel gain unit 176 generates a local pixel gain signal 178, which is communicated to the amplifier array 164, so as to control a specific amplification of the colour image signals 158, 160 and 162.
  • FIG. 2 shows part of a projection system according to a second embodiment of the present invention.
  • figure 2 shows a part of a optical system 200 of a projection system, which part comprises a projection lamp 202, a first integrator plate 204, a second integrator plate 206, and a masking unit 208 disposed between the first and second integrator plates 204, 206.
  • the masking unit 208 comprises a first mask 210 and a second mask 212, which first mask 210 has a structure surface 214 facing the projection lamp 202.
  • the structure surface 214 comprises a plurality of tilted peaks 216 reflecting light from the projection lamp 202 away from the projection lamp 202, thereby avoiding over heating of the projection lamp 202 due to dimming of the light.
  • the structured surface 214 may be formed directly on the first mask 210 or it may in fact be added on to the first mask 210 so that the first mask 210 defines a composite of layers.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Projection Apparatus (AREA)
  • Liquid Crystal Display Device Control (AREA)

Abstract

L'intention se rapporte à un procédé et un système d'affichage (100) permettant de présenter une image en fonction d'un signal d'entrée d'image (158, 160, 162) et comportant une source lumineuse (106) générant une lumière, des moyens intégrateurs (110,112) permettant de recueillir et de focaliser ladite lumière, des moyens modulateurs de lumière (148a, 148b, 148c) destinés à moduler ledit signal d'entrée d'image (158, 160, 162) par rapport à ladite lumière, et des moyens de commande (154) destinés à ajuster la lumière incidente sur les moyens modulateurs de lumière (148a, 148b, 148c) en fonction de la luminosité du signal d'entrée d'image (158, 160, 162). L'invention se rapporte en outre à une unité de commande dynamique (154) du contraste d'une image affichée sur une surface.
PCT/IB2004/051427 2003-08-28 2004-08-09 Procede et systeme de commande de contraste dynamique pour un systeme d'affichage WO2005022925A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP03103242.8 2003-08-28
EP03103242 2003-08-28

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Publication Number Publication Date
WO2005022925A1 true WO2005022925A1 (fr) 2005-03-10

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WO (1) WO2005022925A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2043079A3 (fr) * 2007-09-28 2010-03-17 Sharp Kabushiki Kaisha Appareil d'affichage vidéo avec contrôle dynamique du rétroéclairage

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5597223A (en) * 1993-12-27 1997-01-28 Kabushiki Kaisha Toshiba Display apparatus
US20010015775A1 (en) * 2000-02-18 2001-08-23 Chikara Yamamoto Illumination optical system and projection type display apparatus using the same
EP1170959A2 (fr) * 2000-07-05 2002-01-09 Seiko Epson Corporation Système d'illumination optique et projecteur comprenant ce sytème
US20020021292A1 (en) * 2000-05-08 2002-02-21 Yukihiko Sakashita Display apparatus and image signal processing apparatus
US20020050987A1 (en) * 2000-08-14 2002-05-02 Yukihiko Sakashita Display device
EP1235428A2 (fr) * 2001-02-27 2002-08-28 Mitsubishi Denki Kabushiki Kaisha Dispositif d'affichage par projection
US20030063263A1 (en) * 1999-09-02 2003-04-03 Douglas Stanton Method of and device for generating an image having a desired brightness
US20030086265A1 (en) * 2001-10-09 2003-05-08 Seiko Epson Corporation Lighting apparatus and projection type display, and driving method therefore
US20030146919A1 (en) * 2001-04-25 2003-08-07 Masahiro Kawashima Video display apparatus and video display method

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5597223A (en) * 1993-12-27 1997-01-28 Kabushiki Kaisha Toshiba Display apparatus
US20030063263A1 (en) * 1999-09-02 2003-04-03 Douglas Stanton Method of and device for generating an image having a desired brightness
US20010015775A1 (en) * 2000-02-18 2001-08-23 Chikara Yamamoto Illumination optical system and projection type display apparatus using the same
US20020021292A1 (en) * 2000-05-08 2002-02-21 Yukihiko Sakashita Display apparatus and image signal processing apparatus
EP1170959A2 (fr) * 2000-07-05 2002-01-09 Seiko Epson Corporation Système d'illumination optique et projecteur comprenant ce sytème
US20020050987A1 (en) * 2000-08-14 2002-05-02 Yukihiko Sakashita Display device
EP1235428A2 (fr) * 2001-02-27 2002-08-28 Mitsubishi Denki Kabushiki Kaisha Dispositif d'affichage par projection
US20030146919A1 (en) * 2001-04-25 2003-08-07 Masahiro Kawashima Video display apparatus and video display method
US20030086265A1 (en) * 2001-10-09 2003-05-08 Seiko Epson Corporation Lighting apparatus and projection type display, and driving method therefore

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2043079A3 (fr) * 2007-09-28 2010-03-17 Sharp Kabushiki Kaisha Appareil d'affichage vidéo avec contrôle dynamique du rétroéclairage

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