(19) United States
`(12) Reissued Patent
`Kimpe et a].
`
`USO0RE43707E
`
`US RE43,707 E
`(10) Patent Number:
`(45) Date of Reissued Patent:
`Oct. 2, 2012
`
`(54) METHODS, APPARATUS, AND DEVICES FOR
`NOISE REDUCTION
`
`_
`.
`_
`(75) Inventors- Tom Kimpe, Ghent (BE), Paul
`MatthlJS, Eke (BE)
`
`(73) Assignee: Barco N.V., Kortrijk (BE)
`
`.
`(21) Appl' NO" 13/338380
`_
`(22) Flledl
`
`Dec- 28, 2011
`
`Related US. Patent Documents
`
`Reissue of:
`7,639,849
`(64) Patent No.:
`Dec. 29, 2009
`Issued:
`11/134522
`Appl- No:
`May 23’ 2005
`Heidi _
`'
`'
`U.S. Appl1cat1ons:
`(60) Prov1s1onal appl1cat1on No. 60/ 681,429, ?led on May
`17’ 2005
`
`(51) Int, Cl,
`(200601)
`G06K 9/00
`(2006.01)
`G09G 5/10
`(52) US. Cl. ...................................... .. 382/128; 345/690
`(58) Field of Classi?cation Search ................ .. 382/128,
`382/129’ 130’ 131’ 132’ 133134’ 189; 600/407’
`600/425; 345/156, 180, 182, 183, 204, 207,
`345/619, 659, 689, 690, 903, 904
`See application ?le for complete search history.
`
`(56)
`
`References Cited
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`(Continued)
`
`Primary Examiner iAbolfazl Tabatabai
`(74) Attorney, Agent, or Firm *Hartman Patents PLLC
`
`ABSTRACT
`(57)
`.
`.
`.
`.
`.
`Embodlments Include applymg a compensatlon to an Image
`signal based on nonuniformity of a display device. The com
`pensation is based on information about Variations in light
`output response among elements of the display device. The
`compensation is also modi?ed based on a characteristic of a
`
`desired use Of the
`115 Claims, 16 Drawing Sheets
`
`for each of a plurality of pixels of a
`display, obtaining a measure of a
`light-output response
`
`T100
`
`6
`
`T200
`
`‘7
`
`modifying a map that is
`based on the measures
`
`T300
`
`V
`
`obtaining a display signal
`based on the modi?ed map
`and an image signal
`
`1
`
`Inter Partes Review of RE 43,707
`IPR 2014-00778
`Exhibit 1015
`
`

`
`US RE43,707 E
`Page 2
`
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`5/2007 Cok
`7,227,519 B1
`6/2007 Kawase
`7,301,618 B2* 11/2007 Cok et al. .................... .. 356/218
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`3/2009 Yasuda
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`8/2009 Eckhardt
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`2001/0024178 A1
`11/2001 Takeuchi
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`2002/0047568 A1
`10/2002 Greene
`2002/0154076 A1
`2004/0174320 A1
`9/ 2004 Matthij s
`4/ 2006 Johnson
`2006/0071886 A1
`2010/0033497 A1
`2/2010 Ueno
`
`EP
`EP
`JP
`JP
`JP
`JP
`JP
`W0
`W0
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`FOREIGN PATENT DOCUMENTS
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`European Patent Of?ce. Examination report for European applica
`tion No. 024472334, dated Apr. 11, 2005 (7 pp.).
`European Patent Of?ce. Examination report for European applica
`tion No. 024472334, dated Nov. 14, 2005 (6 pp.).
`Digital Imaging and Communications in Medicine (DICOM) Part
`14: Grayscale Standard Display Function. 1988, 16 pp. (cover, i-iii,
`1-12), Nat’l Elec. Mfgrs. Assoc., Rosslyn, VA.
`T. Kimpe et al. Human vision-based algorithm to hide defective
`pixels in LCDs. SPIE Electronic Imaging 2006, Jan. 15-19, 2006, San
`Jose, CA (9 pp.).
`T. Kimpe. Defective Pixels in Medical LCD Displays: Problem
`Analysis and Fundamental Solution. Journal of Digital Imaging,
`Springer NewYork, Jan. 2006, vol. 19, No. 1, pp. 76-84 (preprint).
`T. Kimpe et al. Defective pixels in medical LCD displays: problem
`analysis and fundamental solution. Soc. Computer Appl. Radiology
`(SCAR) 2005, Jun. 2-5, 2005, Orlando, USA (poster, 1 p.).
`
`T. Kimpe et a1. Solution for Nonuniformities and Spatial Noise in
`Medical LCD Displays by Using Pixel-Based Correction. Journal of
`Digital Imaging, Springer New York, Jul. 2005, vol. 18, No. 3, pp.
`209-218 (proof).
`T. Kimpe et al. Solution for non-uniformities and spatial noise in
`medical LCD displays by using pixel-based correction. Proc. Soc.
`Computer Appl. Radiology (SCAR) 2004, Hot topics session, May
`20-23, 2004, Vancouver, Canada (3 pp.).
`T. Kimpe et al. Spatial Noise and Non-Uniformities in Medical LCD
`Displays: Solution and Performance Results. Proc. Soc. Info. Dis
`play/ Americas Display Eng. Appl. Conf. (SID/ADEAC) 2004, Oct.
`25-27, 2004, Ft. Worth, TX (4 pp.).
`T. Kimpe et al. Increasing Image Quality of Medical LCD Displays
`by Removing Spatial Noise and Luminance Non-uniformities. Rad.
`Soc. N. America (RSNA) 2004, Dec. 3, 2004, Chicago, IL. Last
`accessed Oct. 8, 2005 at http://rsna2004.rsna.org/rsna2004/V2004/
`conference/eventidisplay.cfm?emiid:4410632 (2 pp.).
`T. Kimpe et a1. 7.3: Solving the problem of pixel defects in matrix
`displays based on characteristics of the human visual system.
`EuroDisplay 05, Edinburgh, UK, Sep. 2005. (3 pp.).
`T. Kimpe. Making defective LCD display pixels invisible. Last
`accessed Dec. 25, 2007 at http://spie.org/documents/Newsroom/Im
`ported/195/2006040195.pdf (2 pp.).
`L.J. Kerofsky et al. 15.2: Optimal rendering for Colour Matrix Dis
`plays. ADEAC 05, Oct. 2005, Portland, OR, pp. 123-126.
`D.S. Messing et al. 15.3: An Application of Optimal Rendering to
`Visually Mask Defective Subpixels. ADEAC 05, Oct. 2005, Portland,
`OR, pp. 127-129.
`H. SeetZen et al. P 54.2: A High Dynamic Range Display Using Low
`and High Resolution Monitors. SID 03 Digest. Last accessed Dec. 25,
`2007 at http://www.anyhere.com/gward/papers/sid03.pdf (4 pp.).
`Clerk of US District Court for the Northern District of Georgia.
`Report on the Filing or Determination of an Action Regarding a
`Patent or Trademark for case 1: 11-cv-02964-RLV regarding US Pat.
`No. 7,639,849. Sep. 6, 2011 (1 p.).
`Complaint of plaintiffs Barco NV and Barco, Inc. in case 1:11-cv
`02964-RLV. Sep. 2, 2011 (15 pp.).
`Answer of defendants EiZo Nanao Corp. and EiZo Nanao Technolo
`gies Inc. in case 1:11-cv-02964-RLV. Dec. 6, 2011 (23 pp.).
`European Patent Of?ce. Examination report for European applica
`tion No. 0244472334, dated Apr. 11, 2005 (7 pp.).
`Digital Imaging and Communication in Medicine (DICOM) Part 14:
`Grayscale Standard Display Function. 1998, 16 pp. (cover, i-iii,
`1-12), Nat’l Elec. Mfgrs. Assoc. Rosslyn, VA.
`
`* cited by examiner
`
`2
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`

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`US. Patent
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`0a. 2, 2012
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`US RE43,707 E
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`US RE43,707 E
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`US. Patent
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`0a. 2, 2012
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`Sheet 13 0f 16
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`US RE43,707 E
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`FIG. 20
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`for each of a plurality of pixels of a
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`Oct. 2, 2012
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`US RE43,707 E
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`
`US. Patent
`
`Oct. 2, 2012
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`Sheet 15 0f 16
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`US RE43,707 E
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`Oct. 2, 2012
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`
`US RE43,707 E
`
`1
`METHODS, APPARATUS, AND DEVICES FOR
`NOISE REDUCTION
`
`Matter enclosed in heavy brackets [ ] appears in the
`original patent but forms no part of this reissue speci?ca
`tion; matter printed in italics indicates the additions
`made by reissue.
`
`RELATED APPLICATIONS
`
`This application claims bene?t of US. Provisional Patent
`Application No. 60/681,429, entitled “METHODS, APPA
`RATUS, AND DEVICES FOR NOISE REDUCTION,” ?led
`May 17, 2005.
`
`CROSS-REFEREN CE T 0 RELATED
`APPLI CA 17 ON
`
`This application is a reissue 0fU.S. Pat. No. 7,639, 849,
`issued Dec. 29, 2009.
`
`20
`
`FIELD OF THE INVENTION
`
`This invention relates to image display.
`
`BACKGROUND
`
`Image noise is an important parameter in the quality of
`medical diagnosis. Several scienti?c studies have indicated
`that even slight increase of noise in medical images can have
`a signi?cant negative impact on the accuracy and quality of
`medical diagnosis. In a typical medical imaging system there
`are several phases, and in each of these phases unwanted
`noise can be introduced. The ?rst phase is the actual modality
`or source that produces the medical image. Examples of such
`modalities include X-ray machines, computed tomography
`(CT) scanners, ultrasound scanners, magnetic resonance
`imaging (MRI) scanners, and positron emission tomography
`(PET) scanners. As for any sensor system or measurement
`device, there is always some amount of measurement noise
`present due to imperfections of the device or even due to
`physical limitations (such as statistical uncertainty). A lot of
`effort has been put into devices that produce low-noise
`images or image data. For example, images from digital
`detectors (very alike to CCDs in digital cameras) used for
`X-rays are post-processed to remove noise by means of ?at
`?eld correction and dark ?eld correction.
`Once the medical image is available, this image is to be
`viewed by a radiologist. Traditionally light boxes were used
`in combination with ?lm, but nowadays more and more dis
`play systems (?rst CRT-based and afterwards LCD-based)
`are used for this task. The introduction of those digital display
`systems not only improved the work?ow e?iciency a lot but
`also opened new possibilities to improve medical diagnosis.
`For example: with display systems it becomes possible for the
`radiologist to perform image processing operations such as
`Zoom, contrast enhancement, and computer assistance (com
`puter aided diagnosis or CAD). However, also signi?cant
`disadvantages of medical display systems cannot be
`neglected.
`Contrary to extremely low noise ?lm, display systems suf
`fer from signi?cant noise. Matrix based or matrix addressed
`displays are composed of individual image forming elements,
`called pixels (Picture Elements), that can be driven (or
`addressed) individually by proper driving electronics. The
`driving signals can switch a pixel to a ?rst state, the on-state
`
`2
`(luminance emitted, transmitted or re?ected), to a second
`state, the off-state (no luminance emitted, transmitted or
`re?ected). For some displays, one stable intermediate state
`between the ?rst and the second state is usedisee EP 462 619
`which describes an LCD. For still other displays, one or more
`intermediate states between the ?rst and the second state
`(modulation of the amount of luminance emitted, transmitted
`or re?ected) are used. A modi?cation of these designs
`attempts to improve uniformity by using pixels made up of
`individually driven sub-pixel areas and to have most of the
`sub-pixels driven either in the on- or off-stateisee EP 478
`043 which also describes an LCD. One sub-pixel is driven to
`provide intermediate states. Due to the fact that this sub-pixel
`only provides modulation of the grey-scale values determined
`by selection of the binary driven sub-pixels the luminosity
`variation over the display is reduced.
`A known image quality de?ciency existing with these
`matrix based technologies is the unequal light-output
`response of the pixels that make up the matrix addressed
`display consisting of a multitude of such pixels. More spe
`ci?cally, identical electric drive signals to various pixels may
`lead to different light-output output of these pixels. Current
`state of the art displays have pixel arrays ranging from a few
`hundred to millions of pixels. The observed light-output dif
`ferences between (even neighboring) pixels is as high as 30%
`(as obtained from the formula (minimum luminance-maxi
`mum luminance)/minimum luminance).
`These differences in behavior are caused by various pro
`duction processes involved in the manufacturing of the dis
`plays, and/or by the physical construction of these displays,
`each of them being different depending on the type of tech
`nology of the electronic display under consideration. As an
`example, for liquid crystal displays (LCDs), the application
`of rubbing for the alignment of the liquid crystal (LC) mol
`ecules, and the color ?lters used, are large contributors to the
`different luminance behavior of various pixels. The problem
`of lack of uniformity of OLED displays is discussed in US
`20020047568. Such lack of uniformity may arise from dif
`ferences in the thin ?lm transistors used to switch the pixel
`elements.
`EP 0755042 (US. Pat. No. 5,708,451) describes a method
`and device for providing uniform luminosity of a ?eld emis
`sion display (FED). Non-uniformities of luminance charac
`teristics in a FED are compensated pixel by pixel. This is done
`by storing a matrix of correction values, one value for each
`pixel. These correction values are determined by a previously
`measured emission e?iciency of the corresponding pixels.
`These correction values are used for correcting the level of the
`signal that drives the corresponding pixel.
`It is a disadvantage of the method described in EP 0755042
`that a linear approach is applied, i.e. that a same correction
`value is applied to a drive signal of a given pixel, independent
`of whether a high or a low luminance has to be provided.
`However, pixel luminance for different drive signals of a pixel
`depends on physical features of the pixel, and those physical
`features may not be the same for high or low luminance levels.
`Therefore, pixel non-uniformity is different at high or low
`levels of luminance, and if corrected by applying to a pixel
`drive signal a same correction value independent of the drive
`value corresponds to a high or to a low luminance level,
`non-uniformities in the luminance are still observed.
`
`SUMMARY
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`A method of image processing according to one embodi
`ment includes, for each of a plurality of pixels of a display,
`obtaining a measure of a light-output response of at least a
`
`19
`
`

`
`US RE43,707 E
`
`3
`portion of the pixel at each of a plurality of driving levels. The
`method includes modifying a map that is based on the
`obtained measures, to increase a visibility of a characteristic
`of a displayed image during a use of the display. The method
`also includes obtaining a display signal based on the modi?ed
`map and an image signal.
`An image processing apparatus according to an embodi
`ment includes an array of storage elements con?gured to
`store, for each of a plurality of pixels of a display, a measure
`of a light-output response of at least a portion of the pixel at
`each of a plurality of driving levels. The apparatus also
`includes an array of logic elements con?gured to modify a
`map based on the stored measures and to obtain a display
`signal based on the modi?ed map and an image signal. The
`array of logic elements is con?gured to modify the map to
`increase a visibility of a characteristic of a displayed image
`during a use of the display.
`The scope of disclosed embodiments also includes a sys
`tem for characterizing the luminance response of each indi
`vidual pixel of a matrix display, and using this characteriza
`tion to pre-correct the driving signals to that display in order
`to compensate for the expected (characterized) unequal lumi
`nance betWeen different pixels.
`These and other characteristics, features and potential
`advantages of various disclosed embodiments Will become
`apparent from the folloWing detailed description, taken in
`conjunction With the accompanying draWings, Which illus
`trate, by Way of example, principles of the invention. This
`description is given for the sake of example only, Without
`limiting the scope of the invention. The reference ?gures
`quoted beloW refer to the attached draWings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
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`FIG. 1 illustrates a matrix display having greyscale pixels
`With equal luminance.
`FIG. 2 illustrates a matrix display having greyscale pixels
`With unequal luminance.
`FIG. 3 illustrates a greyscale LCD based matrix display
`having unequal luminance in subpixels.
`FIG. 4 illustrates a ?rst embodiment of an image capturing
`device, the image capturing device comprising a ?atbed scan
`ner.
`FIG. 5 illustrates a second embodiment of an image cap
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`turing device, the image capturing device comprising a CCD
`camera and a movement device.
`FIG. 6 schematically illustrates an embodiment of an algo
`rithm to identify matrix display pixel locations.
`FIG. 7 shoWs an example of a luminance response curve of
`an individual pixel, the curve being constructed using eleven
`characterization points.
`FIG. 8 is a block-schematic diagram of signal transforma
`tion according to an embodiment.
`FIG. 9 illustrates the signal transformation of the diagram
`of FIG. 8.
`FIG. 10 is a graph shoWing different examples of pixel
`response curves.
`FIG. 11 illustrates an embodiment of a correction circuit.
`FIG. 12 shoWs an example of a contrast sensitivity func
`tion.
`FIGS. 13-20 shoW examples of neighborhoods of a pixel or
`subpixel.
`FIG. 21 shoWs a ?oW chart of a method M100 according to
`an embodiment.
`FIG. 22 shoWs a ?oW chart of an implementation M110 of
`method M100.
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`FIG. 23 shoWs a ?oW chart of an implementation M120 of
`method M100.
`FIG. 24 shoWs a block diagram of an apparatus 100 accord
`ing to an embodiment.
`FIG. 25 shoWs a block diagram of a system 200 according
`to an embodiment.
`FIG. 26 shoWs a block diagram of an implementation 102
`of apparatus 100.
`In the different ?gures, the same reference ?gures refer to
`the same or analogous elements.
`
`DETAILED DESCRIPTION
`
`The scope of disclosed embodiments includes a system and
`a method for noise reduction in medical imaging, in particular
`for medical images being vieWed on display systems. At least
`some embodiments may be applied to overcome one or more
`disadvantages of the prior art as mentioned above.
`Various embodiments Will be described With respect to
`particular embodiments and With reference to certain draW
`ings but the invention is not limited thereto but only by the
`claims. The draWings described are only schematic and are
`non-limiting. In the draWings, the size of some of the ele
`ments may be exaggerated and not draWn on scale for illus
`trative purposes. Where the term “comprising” is used in the
`present description and claims, it does not exclude other
`elements or steps. Unless expressly limited by its context, the
`term “obtaining” is used to indicate any of its ordinary mean
`ings, such as sensing, measuring, recording, receiving (eg
`from a sensor or external device), and retrieving (eg from a
`storage element).
`In the present description, the terms “horizontal” and “ver
`tical” are used to provide a co-ordinate system and for ease of
`explanation only. They do not need to, but may, refer to an
`actual physical direction of the device.
`Embodiments relate to a system and method for noise
`reduction, for example in real-time, in medical imaging and in
`particular of the non-uniformity of pixel luminance behavior
`present in matrix addressed electronic display devices such as
`plasma displays, liquid crystal displays, LED and OLED
`displays used in projection or direct vieWing concepts.
`Embodiments may be applied to emissive, transmissive,
`re?ective and trans-re?ective display technologies ful?lling
`the feature that each pixel is individually addressable.
`A matrix addressed display comprises individual display
`elements. In the present description, the term “display ele
`ments” is to be understood to comprise any form of element
`Which emits light or through Which light is passed or from
`Which light is re?ected. A display element may therefore be
`an individually addressable element of an emissive, transmis
`sive, re?ective or trans-re?ective display. Display elements
`may be pixels, eg in a greyscale LCD, as Well as sub-pixels,
`a plurality of sub-pixels forming one pixel. For example three
`sub-pixels With a different color, such as a red sub-pixel, a
`green sub-pixel and a blue sub-pixel may together form one
`pixel in a color LCD. A subpixel arrangement may also be
`used in a greyscale (or “monochrome”) display. Whenever
`the Word “pixel” is used, it is to be understood that the same
`may hold for sub-pixels, unless the contrary is explicitly
`mentioned.
`Embodiments Will be described With reference to ?at panel
`displays but the range of embodiments is not limited thereto.
`It is understood that a ?at panel display does not have to be
`exactly ?at but includes shaped or bent panels. A ?at panel
`display differs from a display such as a cathode ray tube in
`that it comprises a matrix or array of “cells” or “pixels” each
`producing or controlling light over a small area. Arrays of this
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`kind are called fixed format arrays. There is a relationship
`between the pixel of an image to be displayed and a cell of the
`display. Usually this is a one-to-one relationship. Each cell
`may be addressed and driven separately.
`The range ofembodiments includes embodiments that may
`be applied to flat panel displays that are active matrix devices,
`embodiments that may be applied to flat panel displays that
`are passive matrix devices, and embodiments that may be
`applied to both types of matrix device. The array of cells is
`usually in rows and columns but the range of embodiments
`includes applications to any arrangement, e.g. polar or hex-
`agonal . Although embodiments will mainly be described with
`respect to liquid crystal displays, the range of application of
`the principles disclosed herein is more widely applicable to
`flat panel displays of different types, such as plasma displays,
`field emission displays, electroluminescent (EL) displays,
`organic light-emitting diode (OLED) displays, polymeric
`light-emitting diode (PLED) displays, etc. In particular, the
`range of embodiments includes application not only to dis-
`plays having an array of light emitting elements but also to
`displays having arrays of light emitting devices, whereby
`each device is made up of a number of individual elements.
`The displays may be emissive, transmissive, reflective, or
`trans-reflective displays, and the light-output behavior may
`be caused by any optical process affecting visual light or
`electrical process indirectly defining an optical response of
`the system.
`Further the method of addressing and driving the pixel
`elements of an array is not considered a limitation on the
`application of these principles. Typically, each pixel element
`is addressed by means ofwiring but other methods are known
`and are useful with appropriate embodiments, e.g. plasma
`discharge addressing (as disclosed in U.S. Pat. No. 6,089,
`739) or CRT addressing.
`A matrix addressed display 2 comprises individual pixels.
`These pixels 4 can take all kinds of shapes, e.g. they can take
`the forms of characters. The examples of matrix displays 2
`given in FIG. 1 to FIG. 3 have rectangular or square pixels 4
`arranged in rows and columns. FIG. 1 illustrates an image of
`a perfect display 2 having equal luminance response in all
`pixels 4 when equally driven. Every pixel 4 driven with the
`same signal renders the same luminance. In contrast, FIG. 2
`and FIG. 3 illustrate different cases where the pixels 4 of the
`displays 2 are also driven by equal signals but where the
`pixels 4 render a different luminance, as can be seen by the
`different grey values in the different drawings. The spatial
`distribution ofthe luminance differences ofthe pixels 4 can be
`arbitrary. It is also found that with many technologies, this
`distribution changes as a function of the applied drive to the
`pixels. For a low drive signal leading to low luminance, the
`spatial distribution pattern can differ from the pattern at a
`higher driving signal.
`The phenomenon of non-uniform light-output response of
`a plurality ofpixels is disturbing in applications where image
`fidelity is required to be high, such as for example in medical
`applications, where luminance differences of about 1% may
`have a clinical
`significance. The unequal
`light-output
`response of the pixels superimposes an additional, disturbing
`and unwanted random image on the required or desired
`image, thus reducing the signal-to-noise ratio (SNR) of the
`resulting image.
`Moreover, at the end the only goal is to increase the accu-
`racy and quality ofthe medical diagnosis, and noise reduction
`is a means to accomplish this goal. Therefore, noise reduction
`does not necessarily have the same meaning as correction for
`non-uniformities. In other words, if the non-uniformities do
`not interfere with the medical diagnosis then there is no
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`advantage to correct for the non-uniformities. In some cases
`correcting those non-uniformities can even result in lower
`accuracy ofdiagnosis as will be explained in detail later in this
`text. This also means that the noise reduction algorithms in
`the ideal case are matched with the type of medical image
`being looked at, as will be explained later.
`In order to be able to correct matrix display pixel non-
`uniforrnities, it is desirable that the light-output of each indi-
`vidual pixel is known, and thus has been detected.
`The range of embodiments includes a characterizing
`device such as a vision measurement system, a set-up for
`automated, electronic vision of the individual pixels of the
`matrix addressed display, i.e. for measuring the light-output,
`e.g. luminance, emitted or reflected (depending on the type of
`display) by individual pixels 4, using a vision measurement
`set-up. The vision measurement system comprises an image
`capturing device 6, 12 and possibly a movement device 5 for
`moving the image capturing device 6, 12 and/or the display 2
`with respect to each other. Two embodiments are given as an
`example, although other electronic vision implementations
`may be possible reaching the same result: an electronic image
`of the pixels.
`According to a first embodiment, as represented in FIG. 4,
`the matrix addressed display 2 is placed with its light emitting
`side against an image capturing device, for example is placed
`face down on a flatbed scarmer 6. The flatbed scarmer 6 may
`be a suitably modified document or film scanner. The spatial
`resolution ofthe scanner 6 is so as to allow for adequate vision
`of the individual pixels 4 of the display 2 under test. The
`sensor 8 and image processing hardware of the flat bed scan-
`ner 6 also have enough luminance sensitivity and resolution
`in order to give a precise quantization of the luminance emit-
`ted by the pixels 4. For an emissive display 2, the light source
`10 or lamp of the scanner 6 is switched off: the luminance
`measured is emitted by the display 2 itself. For a reflective
`type of display 2, the light source 10 or lamp of the scanner 6
`is switched on: the light emitted by the display 2 is light from
`the scarmer’s light source 10, modulated by the reflective
`properties of the display 2, and reflected, and is subsequently
`measured by the sensor 8 of the scanner 6.
`The output file of the image capturing device (in the
`embodiment described, scanner 6) is an electronic image file
`giving a detailed picture of the pixels 4 of the complete
`electronic display 2.
`According to a second embodiment of the vision measure-
`ment system, as illustrated in FIG. 5, an image capturing
`device, such as e. g. a high resolution CCD camera 12, is used
`to take a picture ofthe pixels 4 ofthe display 2. The resolution
`of the CCD camera 12 is so as to allow adequate definition of
`the individual pixels 4 of the display 2 to be characterized. A
`typical LCD panel may have a diagonal dimension of from 12
`or 14 to 19 or 21 inches or more. In the current state of the art
`
`of CCD cameras, it may not be possible to image large matrix
`displays 2 at once. As an example, high resolution electronic
`displays 2 with an image diagonal of more than 20" may
`require that the CCD camera 12 and the display 2 are moved
`with respect to each other, e.g. the CCD camera 12 is scarmed
`(in X-Y position) over the image surface of the display 2, or
`vice versa: the display 2 is scanned over the sensor area ofthe
`CCD camera 12, in order to take several pictures of different
`parts of the display area 2. The pictures obtained in this way
`are thereafter preferably stitched to obtain one image of the
`complete active image surface of the display 2.
`Again, the resulting electronic image file, i.e. the output file
`of the image capturing device, which is in the embodiment
`described a CCD camera 12, gives a detailed picture of the
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`pixels 1 of the display 2 that needs to be characterized. An
`example of an image 13 of the pixels 4 of a matrix display 2
`is visualized in FIG. 6a.
`
`Once an image 13 of the pixels 4 of the display 2 has been
`obtained, a process is run to extract pixel characterization data
`from the electronic image 13 obtained from the image cap-
`turing device 6, 12.
`In the image 13 obtained, algorithms will be used to assign
`one luminance v