(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2006/0034492 A1
`Siegel et al.
`(43) Pub. Date:
`Feb. 16, 2006
`
`US 20060034492A1
`
`(54) HAND RECOGNITION SYSTEM
`(76) Inventors: Roy Siegel, Portland, OR (US); Willem
`den Boer, Hillsboro, OR (US); Adiel
`Abileah, Portland, OR (US)
`Correspondence Address:
`Kevin L. Russell
`Suite 1600
`601 SW Second Ave.
`Portland, OR 97204-3157 (US)
`(21) Appl. No.:
`10/285,464
`
`(22) Filed:
`
`Oct. 30, 2002
`Publication Classification
`
`(51) Int. Cl.
`(2006.01)
`G06K 9/00
`(52) U.S. Cl. .............................................................. 382/115
`
`(57)
`
`ABSTRACT
`
`A hand recognition System.
`
`41
`
`
`
`
`
`APPLICATION PROGRAM
`REQUIRES BIOMETRIC
`VERIFICATION
`
`42
`DISPLAY INSTRUCTIONAL
`INFORMATION ON DISPLAY
`
`43
`
`SCAN HAND
`
`
`
`44
`
`THICKNESS SCANS
`
`
`
`48
`
`DATA PROCESSING BY
`USING PROCESSING SYSTEM
`
`49
`
`PERMIT OR
`DENYACCESS
`
`Page 1 of 30
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`GOOGLE EXHIBIT 1016
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`Patent Application Publication Feb. 16, 2006 Sheet 1 of 19
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`US 2006/0034492 A1
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`30
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`LOCK
`ASSOCICATION
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`PROCESSING
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`BIOMETRIC
`DETERMINATIONS
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`FIG 2
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`Page 2 of 30
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`Patent Application Publication Feb. 16, 2006 Sheet 2 of 19
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`US 2006/0034492 A1
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`HAND IDENTIFICATION
`ACCESS HERE
`
`FIG. 3
`
`
`
`PROCESSING DATA ...
`
`FIG. 4
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`Patent Application Publication Feb. 16, 2006 Sheet 3 of 19
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`ACCESS APPROVED
`
`FIG. 5
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`ACCESS DENIED
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`FIG. 6
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`Patent Application Publication Feb. 16, 2006 Sheet 4 of 19
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`US 2006/0034492 A1
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`41
`
`
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`APPLICATION PROGRAM
`REQUIRES BIOMETRIC
`VERIFICATION
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`42
`DISPLAY INSTRUCTIONAL
`INFORMATION ON DISPLAY
`
`43
`
`SCAN HAND
`
`44
`
`THICKNESS SCANS
`
`48
`
`DATA PROCESSING BY
`USING PROCESSING SYSTEM
`
`49
`
`PERMIT OR
`DENYACCESS
`
`FIG. 7
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`Page 5 of 30
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`Patent Application Publication Feb. 16, 2006 Sheet 6 of 19
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`Patent Application Publication Feb. 16, 2006 Sheet 8 of 19
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`Patent Application Publication Feb. 16, 2006 Sheet 10 of 19
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`US 2006/0034492 A1
`
`Feb. 16, 2006
`
`HAND RECOGNITION SYSTEM
`
`BACKGROUND OF THE INVENTION
`0001. The present invention relates to verification
`devices. More particularly, it relates to a verification System
`which measures the hand of a user for the purposes of
`Verification.
`0002 Traditionally, keys of both a mechanical and an
`electrical nature have been used to restrict access to Secure
`areas to authorized individuals. The controlled access to
`Secure areas may be to physical areas, Such as with the
`common lock and key, or to information, Such as with
`computer terminal passwords, or to valuables, Such as with
`automatic bank teller personal identification codes. One of
`the problems with these types of Systems is that acceSS is
`provided to any key holder, and the keys are transferable and
`easily lost, Stolen or passed on.
`0.003 More recently, identification devices relying upon
`biometric characteristics unique to an individual have been
`proposed. Such biometric devices measure and compare
`characteristics of Such things as Voice, fingerprints, facial
`Scans, retinal Scans, and Signatures. Each of these biometric
`devices have performance limitations because the charac
`teristic of the perSon that is measured tends to vary greatly
`even for a given individual. For example, a perSon's finger
`prints Suffer day-to-day damage from Scratches, abrasions
`and So on, that make accurate automatic identification very
`difficult. Also, biometric devices tend to be very costly to
`manufacture because of the precision required for repeatable
`measurement of Such fine detail as fingerprint minutia in
`fingerprint recognition Systems, and high fidelity voice
`detection and background noise filtering in Voice recognition
`Systems.
`0004.
`It is generally known that people's hands differ in
`their size and shape, and that these differences may be used
`for verification of an individual’s identify. Many geometric
`characteristics of the hand may be measured and used as the
`basis to distinguish between different people. For example,
`one or more measurements Such as finger length, knuckle
`positions, width, area, perimeter, thickness, and So on, may
`be used for verification of an individual’s identify. Also,
`combinations of these measurements, Such as the ratio of
`length to width, can be used with good effect as identity
`discriminates. Depending on the particular System design,
`hand recognition Systems are relatively invariant to dirt,
`ethnicity, age, and imaging quality.
`0005 Systems exist that utilize two-dimensional pictures
`of the hand outline obtained with an electronic digitizing
`camera. However, they may be defeated by the use of an
`artifact in the shape of the hand of the claimed identity. Since
`only a simple two dimensional Shadow image is required,
`Such an artifact is easily constructed from a cardboard
`tracing of the hand of an authorized user. Such an outline can
`be obtained either Surreptitiously, or through the cooperation
`of the authorized user.
`0006 Sidlauskas, U.S. Pat. No. 4,736,203, discloses a
`three dimensional hand profile identification System. Refer
`ring to FIG. 1, Sidlauskas discloses an overall enclosure 10
`which houses a digitizing camera 12, optical beam reflecting
`mirrorS 13 and 14, a hand measuring platen 15, a keypad 16
`for entering an identity code, Suitable control and processing
`
`electronicS 17, and a comparison results indicating lamp 18.
`The camera 12 and the mirrors 13 and 14 are positioned
`within the enclosure 10 Such that the camera has a full view
`of the measuring platen 15. A first measuring Surface 20 and
`a Second measuring Surface 22 are at right angles with
`respect to each other, both constructed from a optically
`retro-reflective material. A plane mirror 24 is mounted to the
`first measuring Surface 20 on the Side opposite from the
`Second measurement Surface 22 and facing the Second
`measuring Surface but tilted at an angle of 45 degrees to both
`the first measuring Surface and the optical axis of the
`digitizing camera. While the System disclosed by Sidlauskas
`is functional, the optical System is Somewhat complex, and
`requires a relatively extensive optical path. In addition, the
`housing and associated electronics are Somewhat “indus
`trial” in appearance and not aesthetically Suitable for all
`environments.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0007 FIG. 1 illustrates an existing hand recognition
`System.
`0008 FIG. 2 illustrates an exemplary embodiment of a
`hand recognition System of the present invention.
`0009 FIG. 3 illustrates a display with textual and graphi
`cal information.
`0010 FIG. 4 illustrates a display with textual and graphi
`cal information.
`0011 FIG. 5 illustrates a display with textual and graphi
`cal information.
`0012 FIG. 6 illustrates a display with textual and graphi
`cal information.
`0013 FIG. 7 illustrates an exemplary flow chart for the
`operation of the system shown in FIG. 2.
`0014 FIG. 8 illustrates an exemplary processing block
`diagram for the system shown in FIG. 2.
`0.015 FIGS. 9A and 9B illustrates data from the system
`shown in FIG. 2.
`0016 FIG. 10 is a cross sectional view of a traditional
`active matrix liquid crystal display.
`0017 FIG. 11 is a schematic of the thin film transistor
`array.
`0018 FIG. 12 is a layout of the thin film transistor array
`of FIG. 11.
`0019 FIGS. 13A-13H is a set of steps suitable for
`constructing pixel electrodes and amorphous Silicon thin
`film transistors.
`0020 FIG. 14 illustrates pixel electrodes, color filters,
`and a black matrix.
`0021
`FIG. 15 illustrates a schematic of the active matrix
`elements, pixel electrode, photo TFT, readout TFT, and a
`black matrix.
`0022 FIG. 16 illustrates a pixel electrode, photo TFT,
`readout TFT, and a black matrix.
`0023 FIG. 17 is a layout of a thin film transistor array.
`
`Page 21 of 30
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`
`Feb. 16, 2006
`
`0024 FIG. 18 is a graph of the capacitive charge on the
`light Sensitive elements as a result of inhibiting light to the
`display at high ambient lighting conditions.
`0.025
`FIG. 19 is a graph of the capacitive charge on the
`light Sensitive elements as a result of inhibiting light to the
`display at low ambient lighting conditions.
`0.026
`FIG. 20 is a graph of the photo-currents in an
`amorphous silicon TFT array.
`0.027
`FIG. 21 is a graph of the capacitive charge on the
`light Sensitive elements as a result of inhibiting light to the
`display.
`0028 FIG. 22 is an alternative layout of the pixel elec
`trodes.
`0029 FIG. 23 illustrates a timing set for the layout of
`FIG. 22.
`0030 FIG. 24 illustrates even/odd frame addressing.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`0031. The present inventors considered the aforemen
`tioned hand recognition imaging Systems and came to the
`realization that a non-intrusive hand recognition System may
`include a display, which is capable of displaying Still images
`and/or Video images, together with integrated light Sensitive
`elements to detect the presence of the hand of the user,
`and/or the characteristics of the hand, and/or the shape of the
`hand, etc., described later. The hand may include any portion
`of the hand, Such as for example, the fingers (e.g., 1-4), the
`thumb, the palm, lines on the hand, webbing between
`fingers, knuckle positions, and translucency.
`0032 Referring to FIG. 2, the display 30 may be
`mounted to a wall, sit on a desktop, or any other Suitable
`place. In addition to being used for hand recognition, the
`display 30 may be used to present text and/or images, Such
`as information regarding use of the hand recognition System,
`responses to using the hand recognition System, context
`relevant information (e.g., welcome, instructions about a
`Situation needing biometric input, advertisements, etc.),
`advertisements, or any other application. Moreover, the
`display 30 may be the display of a desktop personal com
`puter System, where the hand recognition System is used for
`any suitable purpose. Further, the display 30 may be the
`display of a laptop computer System, Stand alone display,
`network connected display, thin-client computing device
`with display, where the hand recognition System is used for
`access and Security purposes. When the display 30 is being
`used for hand recognition a Set of light Sensitive elements
`integrated with the display capture an image of the hand or
`a portion thereof placed in overlying relationship to the
`display, Such as in contact thereto or in the proximity
`thereof. For example, the light Sensitive elements may Sense
`the contrast in the ambient light reaching the light Sensitive
`elements, with those light Sensitive elements aligned with
`the Source of ambient light and the hand having a reduced
`ambient light level with respect to other light Sensitive
`elements.
`0.033
`For purposes of “2-dimensional imaging the sys
`tem Senses the contrast of the hand outline based upon
`ambient lighting conditions. One or more external lights (32,
`34) may have their light, Such as white light, directed toward
`
`the display. The additional light directed toward the display,
`with the hand at least partially between the additional light
`and the display, will increase the contrast for measurements.
`In addition, different colored lights may be used, Such as red,
`green, and/or blue lights (or a white light with a color filter
`output) with corresponding red, green, and/or blue Sensors
`(or a white light Sensor with an associated color filter).
`Having different colored lights positioned at different loca
`tions together with different colored sensors will tend to
`increase the contrast for measurements. Moreover, one or
`more of the external white lights, and/or one or more of the
`external different colored lights may be temporally modu
`lated (such as for example, differences in intensity, differ
`ences in the color of the output light, on/off changes in
`intensity) So that the corresponding Sensors will detect
`temporal changes in the Sensed light, which likewise may be
`used to increase contrast.
`0034. Additional fraud verification may be based upon
`ambient lighting conditions. For example, the hand of the
`user may cast a shadow having different intensities which
`may be Sensed by the Sensors. In many cases, the interior
`portion of the hand will cast a dark Shadow (e.g., dark) while
`the edges of the hand will cast a light Shadow (e.g., gray
`scale). Additional fraud verification may be performed by
`temporally characterizing the edges and/or shadows (e.g.,
`grayScale) cast onto the display. For example, the System
`may be able to readily detect a cardboard cutout of a hand
`that is being fraudulently used by temporal characterization
`of a excessively thin side profile at Some point. In addition,
`the aforementioned discussion regarding additional lights,
`grayScale, Shadows, temporal analysis, filtered lights, fil
`tered Sensors, temporal modulation, etc., may likewise be
`employed for fraud verification.
`0035) In many cases, the verification potential of 2-di
`mensional processing may be limited. If desired, the System
`may include 3-dimensional processing of the characteristics
`of the hand to potentially increase the Verification accuracy,
`frequently by processing a plurality of frames. For example,
`thickness estimates of the hand of the user may be made
`using any of the aforementioned techniques, including for
`example, the temporal based shadows from external white or
`colored light. A light Sensitive display may be oriented on
`the side of the display 30, if desired.
`0036) A processing system 40 included within the display
`30, separate from the display 30, or partially within the
`display 30 and partially separate from the display 30, may be
`used for obtaining and processing data from the light Sen
`Sitive elements. In many cases, the data from the light
`Sensitive elements will be obtained in a Scanning operation
`in a row-by-row manner. The data from the light sensitive
`elements may be converted to an equivalent bit-mapped
`image, if desired. The processing System 40 may likewise
`include a biometric determination proceSS 44 which pro
`ceSSes the data from the light Sensitive elements of the
`display 30 to determine whether the hand or portion thereof
`is identified. If the hand being Sensed is identified, Such as
`by template matching, the processing System 40 may unlock
`or otherwise permit access to any associated System 50. The
`permitting acceSS is intended to broadly include any result
`ing activity or action, Such as for example, retail, e-com
`merce, financial transactions, signing up for an activity or
`program. In many cases, the resulting event is Something
`that would not have otherwise been permitted had the
`
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`
`Feb. 16, 2006
`
`biometric Verification been Successful. The template match
`ing is intended to include any and all techniques, whether
`including a formal "template' or not, for comparing hand
`related information (e.g., data) to other hand related infor
`mation (e.g., data).
`0037 Referring to FIG. 3, during the process of hand
`identification, the display 30 may provide textual or graphi
`cal indication that the display provides hand identification
`and where to locate the hand. Referring to FIG. 4, during the
`processing of the data from the light Sensitive elements, the
`display may provide an indication that the processing is
`being performed. Referring to FIG. 5, if the hand is iden
`tified then the System may indicate that access is approved,
`or otherwise denied, as illustrated in FIG. 6. In this manner,
`the display may provide the interactive feedback with the
`user without the need for additional light or Sound indica
`tions, which may be misunderstood by the user. Moreover,
`if the wrong hand is used (in the case of a right hand and left
`hand Sensitive System), the hand is not sufficiently close to
`the display, the fingers are not Sufficiently Separated, etc.,
`then appropriate messages may be displayed on the display
`to assist the user. The graphical and textual display indica
`tions may likewise be used with other hand Sensing Systems
`that are proximate the display.
`0038) Referring to FIG. 7, merely by way of illustration,
`the following Steps may be used by the System for hand
`identification. An application program running on the pro
`cessing system 40 requires biometric verification, for any
`Suitable application, Such as for example, computer log-in,
`network log-in, file access, physical access, e-commerce,
`Security, etc., at block 41. The application program displayS
`suitable instructional information on the display 30, includ
`ing for example, an outline of a hand to show the user where
`to put his hand, at block 42. The processing system 40
`provides a command to the display 30 to scan the hand or
`otherwise Scans the hand, at block 43. The Scanning may
`involve creating one or more 2-dimensional bitmaps, turning
`on and off other light Sources, reading values from light
`Sensitive elements, testing the Sufficiency of the data, aver
`aging multiple Scans (reduces signal to noise ratio), and/or
`creating differential measurements by obtaining Scans with
`and without the optional lights being turned on. The System
`may optionally perform thickneSS Scans at block 44 by
`turning on a light Source positioned during Scanning of block
`43, Such that modified Shadows are created as a function of
`the thickness of the hand. Block 43 may be repeated for
`different lights, light combinations, and/or different colors.
`0.039 The resulting data, sometimes in the format of a
`bitmap, may be transferred to the processing System 40 for
`Subsequent processing at block 48. The Subsequent proceSS
`ing may involve, for example, edge determination of the
`hand, Shadow determination of the hand, thickness determi
`nation of the hand, each of which is based upon a Single
`lighting condition or multiple lighting conditions. The result
`of the Subsequent processing may use the characteristics of
`the measured hand, Such as for example, finger length,
`knuckle positions, width, area, perimeter, ratios, 3-dimen
`Sional thickness, and/or other parameters, to compare
`against a template associated with user's hands. The System
`may then permit or deny access at block 49. One potential
`hand template system is described in U.S. Pat. No. 4,720,
`869, incorporated by reference herein. An exemplary System
`configuration for the system is illustrated in FIG. 8. Refer
`
`ring to FIG. 9A, exemplary data illustrating the Sharp edges
`to the data from the light Sensitive elements of a finger on the
`display is shown. Referring to FIG. 9B, the thresholding of
`the data shown in FIG. 9A illustrates the sharp edges that are
`obtainable.
`0040. The system may likewise be used in conjunction
`with other Systems to provide an additional layer of Security.
`For example, the display may include an associated card
`reader, RF identification badge reader, handwriting recog
`nition software (which may be sensed by the display itself,
`if desired), user entered PIN/password, other biometric
`techniques, etc.
`0041
`Referring to FIG. 10, a liquid crystal display
`(LCD) 50 (indicated by a bracket) comprises generally, a
`backlight 52 and a light valve 54 (indicated by a bracket).
`Since liquid crystals do not emit light, most LCD panels are
`backlit with fluorescent tubes or arrays of light-emitting
`diodes (LEDs) that are built into the sides or back of the
`panel. To disperse the light and obtain a more uniform
`intensity over the Surface of the display, light from the
`backlight 52 typically passes through a diffuser 56 before
`impinging on the light valve 54. For light Sources on the
`edges a light guide is used together with the diffuser 56.
`0042. The transmittance of light from the backlight 52 to
`the eye of a viewer 58, observing an image displayed on the
`front of the panel, is controlled by the light valve 54. The
`light valve 54 normally includes a pair of polarizers 60 and
`62 Separated by a layer of liquid crystals 64 contained in a
`cell gap between glass or plastic plates, and the polarizers.
`Light from the backlight 52 impinging on the first polarizer
`62 comprises electromagnetic waves vibrating in a plurality
`of planes. Only that portion of the light vibrating in the plane
`of the optical axis of the polarizer passes through the
`polarizer. In an LCD light valve, the optical axes of the first
`62 and Second 60 polarizer are typically arranged at an angle
`So that light passing through the first polarizer would nor
`mally be blocked from passing through the Second polarizer
`in the Series. However, the orientation of the translucent
`crystals in the layer of liquid crystals 64 can be locally
`controlled to either “twist' the vibratory plane of the light
`into alignment with the optical axes of the polarizer, per
`mitting light to pass through the light valve creating a bright
`picture element or pixel, or out of alignment with the optical
`axis of one of the polarizes, attenuating the light and creating
`a darker area of the Screen or pixel.
`0043. The surfaces of the a first glass substrate 61 and a
`Second glass Substrate 63 form the walls of the cell gap are
`buffed to produce microscopic grooves to physically align
`the molecules of liquid crystal 64 immediately adjacent to
`the walls. Molecular forces cause adjacent liquid crystal
`molecules to attempt to align with their neighbors with the
`result that the orientation of the molecules in the column of
`molecules Spanning the cell gap twist over the length of the
`column. Likewise, the plane of Vibration of light transiting
`the column of molecules will be “twisted' from the optical
`axis of the first polarizer 62 to a plane determined by the
`orientation of the liquid crystals at the opposite wall of the
`cell gap. If the wall of the cell gap is buffed to align adjacent
`crystals with the optical axis of the Second polarizer, light
`from the backlight 52 can pass through the Series of polar
`izers 60 and 62 to produce a lighted area of the display when
`viewed from the front of the panel (a “normally white”
`LCD).
`
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`0044) To darken a pixel and create an image, a Voltage,
`typically controlled by a thin film transistor, is applied to an
`electrode in an array of transparent electrodes deposited on
`the walls of the cell gap. The liquid crystal molecules
`adjacent to the electrode are attracted by the field produced
`by the Voltage and rotate to align with the field. AS the
`molecules of liquid crystal are rotated by the electric field,
`the column of crystals is “untwisted,” and the optical axes of
`the crystals adjacent to the cell wall are rotated progressively
`out of alignment with the optical axis of the corresponding
`polarizer progressively reducing the local transmittance of
`the light valve 54 and attenuating the luminance of the
`corresponding pixel. In other words, in a normally white
`twisted nematic device there are generally two modes of
`operation, one without a Voltage applied to the molecules
`and one with a Voltage applied to the molecules. With a
`voltage applied (e.g., driven mode) to the molecules the
`molecules do not rotate their polarization axis which results
`in inhibiting the passage of light to the viewer. Similarly,
`without a voltage applied (e.g., non-driven mode) the polar
`ization axis is rotated So that the passage of light is not
`inhibited to the viewer.
`0.045
`Conversely, the polarizers and buffing of the light
`valve can be arranged to produce a “normally black” LCD
`having pixels that are dark (light is blocked) when the
`electrodes are not energized and light when the electrodes
`are energized. Color LCD displays are created by varying
`the intensity of transmitted light for each of a plurality of
`primary color (typically, red, green, and blue) Sub-pixels that
`make up a displayed pixel. Generally, the color filters are on
`the opposite plate from the light valve aligned with the
`Sub-pixel geometry.
`0046) The aforementioned example was described with
`respect to a twisted nematic device. However, this descrip
`tion is only an example and other devices may likewise be
`used, including but not limited to, multi-domain Vertical
`alignment, patterned vertical alignment, in-plane Switching,
`and Super-twisted nematic type LCDS. In addition other
`devices, Such as for example, plasma displays, organic
`displays, active matrix organic light emitting display, elec
`troluminescent displays, liquid crystal on Silicon displayS,
`reflective liquid crystal devices may likewise be used. For
`Such displays the light emitting portion of the display, or
`portion of the display that permits the display of Selected
`portions of light may be considered to Selectively cause the
`pixels to provide light.
`0047 For an active matrix LCD (AMLCD) the inner
`Surface of the Second glass Substrate 63 is normally coated
`with a continuous electrode while the first glass substrate 61
`is patterned into individual pixel electrodes. The continuous
`electrode may be constructed using a transparent electrode,
`Such as indium tin oxide. The first glass Substrate 61 may
`include thin film transistors (TFTS) which act as individual
`Switches for each pixel electrode (or group of pixel elec
`trodes) corresponding to a pixel (or group of pixels). The
`TFTs are addressed by a set of multiplexed electrodes
`running along the gaps between the pixel electrodes. Alter
`natively the pixel electrodes may be on a different layer from
`the TFTs. A pixel is addressed by applying voltage (or
`current) to a selected line, which switches the TFT on and
`allows charge from the data line to flow onto the rear pixel
`electrodes. The combination of voltages between the front
`electrode and the pixel electrodes Sets up a voltage acroSS the
`
`pixels and turns the respective pixels on. The thin-film
`transistors are typically constructed from amorphous Silicon,
`while other types of Switching devices may likewise be used,
`Such as for example, metal-insulator-metal diode and poly
`silicon thin-film transistors. The TFT array and pixel elec
`trodes may alternatively be on the top of the liquid crystal
`material. Also, the continuous electrode may be patterned or
`portions Selectively Selected, as desired. Also the light
`Sensitive elements may likewise be located on the top, or
`otherwise above, of the liquid crystal material, if desired.
`0048 Referring to FIG. 11, the active matrix layer may
`include a set of data lines and a Set of Select lines. Normally
`one data line is included for each column of pixels acroSS the
`display and one Select line is included for each row of pixels
`down the display, thereby creating an array of conductive
`lines. To load the data to the respective pixels indicating
`which pixels should be illuminated, normally in a row-by
`row manner, a Set of Voltages are imposed on the respective
`data lines 204 which imposes a voltage on the sources 202
`of latching transistors 200. The selection of a respective
`select line 210, interconnected to the gates 212 of the
`respective latching transistors 200, permits the Voltage
`imposed on the sources 202 to be passed to the drain 214 of
`the latching transistors 200. The drains 214 of the latching
`transistors 200 are electrically connected to respective pixel
`electrodes and are capacitively coupled to a respective
`common line 221 through a respective Cst capacitor 218. In
`addition, a respective capacitance exists between the pixel
`electrodes enclosing the liquid crystal material, noted as
`capacitances Clc 222 (between the pixel electrodes and the
`common electrode on the color plate). The common line 221
`provides a Voltage reference. In other words, the Voltage
`data (representative of the image to be displayed) is loaded
`into the data lines for a row of latching transistors 200 and
`imposing a Voltage on the Select line 210 latches that data
`into the holding capacitors and hence the pixel electrodes.
`0049 Referring to FIG. 12, a schematic layout is shown
`of the active matrix layer. The pixel electrodes 230 are
`generally grouped into a “single' effective pixel So that a
`corresponding Set of pixel electrodes 230 may be associated
`with respective color filters (e.g., red, green, blue). The
`latching transistorS 200 interconnect the respective pixel
`electrodes 230 with the data lines and the select line. The
`pixel electrodes 230 may be interconnected to the common
`line 221 by the capacitors Cst 218.
`0050 Referring to FIG. 13, the active matrix layer may
`be constructed using an amorphous Silicon thin-film tran
`Sistor fabrication process. The Steps may include gate metal
`deposition (FIG. 13A), a photolithography/etch (FIG.13B),
`a gate insulator and amorphous Silicon deposition (FIG.
`13C), a photolithography/etch (FIG. 13D), a source/drain
`metal deposition (FIG. 13E), a photolithography/etch (FIG.
`13F), an ITO deposition (FIG. 13G), and a photolithogra
`phy/etch (FIG. 13H). Other processes may likewise be used,
`as desired.
`0051
`Referring to FIG. 14, with particular attention to
`the latching transistors of the pixel electrodes, a black matrix
`240 is overlying the latching transistors So that significant
`ambient light does not strike the transistors. Color filters 242
`may be located above the pixel electrodes. Ambient light
`Striking the latching transistorS results in draining the charge
`imposed on the pixel electrodes through the transistor. The
`
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