Patent Publication Number: US-10311824-B2

Title: Multiple driver IC back light unit and liquid crystal response timing for LCD for virtual reality

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of U.S. Provisional Patent Application No. 62/326,442 filed on Apr. 22, 2016 which is incorporated herein by reference for all purposes as if fully set forth herein. 
    
    
     BACKGROUND 
     The present disclosure generally relates to enhancing a Liquid Crystal Display (LCD) for use in a virtual reality, mixed reality, or augmented reality system. 
     SUMMARY 
     A display device that includes a liquid crystal (LC) panel, a back light unit (BLU), a first data driver, and a second data driver. The LC panel includes a plurality of rows of pixels in a pixel area including a first row and a last row. The back light unit (BLU) emits light during an illumination portion of a frame period and does not emit light during a remaining portion of the frame period. A first data driver writes data to a first portion of the pixels of the LC panel. A second data driver writes data to a second portion of the pixels of the LC panel. The first and second data drivers write data at an overlapping time during a write portion of the frame period. The write portion overlaps in time with the remaining portion of the frame period during which the BLU does not emit light. 
     Also described is a method of displaying an image by a display device, the method including steps of emitting, by a back light unit (BLU), light during an illumination portion of a frame period and not emitting light during a remaining portion of the frame period; writing, by a first data driver, data to a first portion of pixels of a liquid crystal (LC) panel; writing, by a second data driver, data to a second portion of the pixels of the LC panel, wherein the first and second data drivers write data at an overlapping time during a write portion of the frame period, the write portion overlapping in time with the remaining portion of the frame period during which the BLU does not emit light. 
     In one embodiment, the first data driver and the second data driver write data during the write portion of the frame period such that liquid crystal material in all rows of the pixels complete transition before the illumination portion of the frame period. In one aspect, the frame period may be 11 milliseconds in length, the write portion may be 3 milliseconds in length, and the illumination portion may be 2 milliseconds in length. 
     In another embodiment, the write portion occurs during an entire frame period. 
     In an embodiment, liquid crystal material in one or more rows of the pixels transitions during the illumination portion of the frame period. The liquid crystal material in the last row of the pixels may complete transition after an end of the write portion of the frame period and before an end of the frame period. The liquid crystal material in the first row of the pixels may complete transition after the end of the write portion of the frame period and before the end of the frame period. In one aspect, the frame period may be 11 milliseconds, the write period may be 5 milliseconds, and the illumination period may be 2 milliseconds. 
     In one embodiment, the first data driver and the second data driver are located on a same side of the pixel area. The first and the second data driver may write data to the LC panel from the first row to the last row of the pixels. In one aspect, the LC panel includes a plurality of columns of the pixels and the first portion of the pixels are in a first half of the columns and the second portion of the pixels are in a second half of the columns. The first half of the columns may be even columns and the second half of the pixel columns may be odd columns. 
     In another embodiment, the first data driver and the second data driver are located on opposite sides of the pixel area. In one aspect, the first portion of the pixels include a top half of rows of the pixels in a top half of the pixel area and the second portion of the pixels include a bottom half of rows of the pixels in a bottom half of the pixel area. The first data driver may write data from a bottom row of the top half of the rows to the first row of the LC panel and the second data driver may write data from a top row of the bottom half of the rows to the last row of the LC panel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a system environment including a virtual reality system, in accordance with an embodiment. 
         FIG. 2A  is a diagram of a virtual reality headset, in accordance with an embodiment. 
         FIG. 2B  is a cross section of a front rigid body of the VR headset in  FIG. 2A , in accordance with an embodiment. 
         FIG. 3A  is a top view of an example electronic display, in accordance with an embodiment. 
         FIG. 3B  is a cross section of an example electronic display, in accordance with an embodiment. 
         FIG. 4A  is a diagram illustrating a frame cycle of an LCD in global illumination mode in accordance with an embodiment. 
         FIG. 4B  is a diagram illustrating a frame cycle of an LCD in black insertion mode in accordance with an embodiment. 
         FIG. 4C  is a diagram illustrating a frame cycle of an LCD using two data driver ICs in global illumination mode in accordance with an embodiment. 
         FIG. 4D  is a diagram illustrating a frame cycle of an LCD using two data driver ICs in black insertion mode in accordance with an embodiment. 
         FIG. 4E  is a diagram illustrating a frame cycle of an LCD using two data driver ICs in hybrid mode in accordance with an embodiment. 
         FIG. 5A  is a diagram illustrating an LCD using two data driver ICs with one scan direction in accordance with an embodiment. 
         FIG. 5B  is a diagram illustrating an LCD using two data driver ICs with two scan directions in accordance with an embodiment. 
     
    
    
     The figures depict embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles, or benefits touted, of the disclosure described herein. 
     DETAILED DESCRIPTION 
     System Overview 
       FIG. 1  is a block diagram of a virtual reality (VR) system environment  100  in which a VR console  110  operates. The system environment  100  shown by  FIG. 1  comprises a VR headset  105 , an imaging device  135 , and a VR input interface  140  that are each coupled to the VR console  110 . While  FIG. 1  shows an example system  100  including one VR headset  105 , one imaging device  135 , and one VR input interface  140 , in other embodiments any number of these components may be included in the system  100 . For example, there may be multiple VR headsets  105  each having an associated VR input interface  140  and being monitored by one or more imaging devices  135 , with each VR headset  105 , VR input interface  140 , and imaging devices  135  communicating with the VR console  110 . In alternative configurations, different and/or additional components may be included in the system environment  100 . 
     The VR headset  105  is a head-mounted display that presents media to a user. Examples of media presented by the VR head set include one or more images, video, audio, or some combination thereof. In some embodiments, audio is presented via an external device (e.g., speakers and/or headphones) that receives audio information from the VR headset  105 , the VR console  110 , or both, and presents audio data based on the audio information. An embodiment of the VR headset  105  is further described below in conjunction with  FIGS. 2A and 2B . The VR headset  105  may comprise one or more rigid bodies, which may be rigidly or non-rigidly coupled to each other together. A rigid coupling between rigid bodies causes the coupled rigid bodies to act as a single rigid entity. In contrast, a non-rigid coupling between rigid bodies allows the rigid bodies to move relative to each other. 
     The VR headset  105  includes an electronic display  115 , an optics block  118 , one or more locators  120 , one or more position sensors  125 , and an inertial measurement unit (IMU)  130 . The electronic display  115  displays images to the user in accordance with data received from the VR console  110 . In various embodiments, the electronic display  115  may comprise a single electronic display or multiple electronic displays (e.g., an electronic display for each eye of a user). 
     An electronic display  115  may be a liquid crystal display (LCD), an organic light emitting diode (OLED) display, an active-matrix organic light-emitting diode display (AMOLED), a TOLED, some other display, or some combination thereof. 
     The optics block  118  magnifies received light from the electronic display  115 , corrects optical errors associated with the image light, and the corrected image light is presented to a user of the VR headset  105 . An optical element may be an aperture, a Fresnel lens, a convex lens, a concave lens, a filter, or any other suitable optical element that affects the image light emitted from the electronic display  115 . Moreover, the optics block  118  may include combinations of different optical elements. In some embodiments, one or more of the optical elements in the optics block  118  may have one or more coatings, such as anti-reflective coatings. 
     Magnification of the image light by the optics block  118  allows the electronic display  115  to be physically smaller, weigh less, and consume less power than larger displays. Additionally, magnification may increase a field of view of the displayed media. For example, the field of view of the displayed media is such that the displayed media is presented using almost all (e.g., 110 degrees diagonal), and in some cases all, of the user&#39;s field of view. In some embodiments, the optics block  118  is designed so its effective focal length is larger than the spacing to the electronic display  115 , which magnifies the image light projected by the electronic display  115 . Additionally, in some embodiments, the amount of magnification may be adjusted by adding or removing optical elements. 
     The optics block  118  may be designed to correct one or more types of optical error. Examples of optical error include: two dimensional optical errors, three dimensional optical errors, or some combination thereof. Two dimensional errors are optical aberrations that occur in two dimensions. Example types of two dimensional errors include: barrel distortion, pincushion distortion, longitudinal chromatic aberration, transverse chromatic aberration, or any other type of two-dimensional optical error. Three dimensional errors are optical errors that occur in three dimensions. Example types of three dimensional errors include spherical aberration, comatic aberration, field curvature, astigmatism, or any other type of three-dimensional optical error. In some embodiments, content provided to the electronic display  115  for display is pre-distorted, and the optics block  118  corrects the distortion when it receives image light from the electronic display  115  generated based on the content. 
     The locators  120  are objects located in specific positions on the VR headset  105  relative to one another and relative to a specific reference point on the VR headset  105 . A locator  120  may be a light emitting diode (LED), a corner cube reflector, a reflective marker, a type of light source that contrasts with an environment in which the VR headset  105  operates, or some combination thereof. In embodiments where the locators  120  are active (i.e., an LED or other type of light emitting device), the locators  120  may emit light in the visible band (˜380 nm to 750 nm), in the infrared (IR) band (˜750 nm to 1 mm), in the ultraviolet band (10 nm to 380 nm), some other portion of the electromagnetic spectrum, or some combination thereof. 
     In some embodiments, the locators  120  are located beneath an outer surface of the VR headset  105 , which is transparent to the wavelengths of light emitted or reflected by the locators  120  or is thin enough not to substantially attenuate the wavelengths of light emitted or reflected by the locators  120 . Additionally, in some embodiments, the outer surface or other portions of the VR headset  105  are opaque in the visible band of wavelengths of light. Thus, the locators  120  may emit light in the IR band under an outer surface that is transparent in the IR band but opaque in the visible band. 
     The IMU  130  is an electronic device that generates fast calibration data based on measurement signals received from one or more of the position sensors  125 . A position sensor  125  generates one or more measurement signals in response to motion of the VR headset  105 . Examples of position sensors  125  include: one or more accelerometers, one or more gyroscopes, one or more magnetometers, another suitable type of sensor that detects motion, a type of sensor used for error correction of the IMU  130 , or some combination thereof. The position sensors  125  may be located external to the IMU  130 , internal to the IMU  130 , or some combination thereof. 
     Based on the one or more measurement signals from one or more position sensors  125 , the IMU  130  generates fast calibration data indicating an estimated position of the VR headset  105  relative to an initial position of the VR headset  105 . For example, the position sensors  125  include multiple accelerometers to measure translational motion (forward/back, up/down, left/right) and multiple gyroscopes to measure rotational motion (e.g., pitch, yaw, roll). In some embodiments, the IMU  130  rapidly samples the measurement signals and calculates the estimated position of the VR headset  105  from the sampled data. For example, the IMU  130  integrates the measurement signals received from the accelerometers over time to estimate a velocity vector and integrates the velocity vector over time to determine an estimated position of a reference point on the VR headset  105 . Alternatively, the IMU  130  provides the sampled measurement signals to the VR console  110 , which determines the fast calibration data. The reference point is a point that may be used to describe the position of the VR headset  105 . While the reference point may generally be defined as a point in space; however, in practice the reference point is defined as a point within the VR headset  105  (e.g., a center of the IMU  130 ). 
     The IMU  130  receives one or more calibration parameters from the VR console  110 . As further discussed below, the one or more calibration parameters are used to maintain tracking of the VR headset  105 . Based on a received calibration parameter, the IMU  130  may adjust one or more IMU parameters (e.g., sample rate). In some embodiments, certain calibration parameters cause the IMU  130  to update an initial position of the reference point so it corresponds to a next calibrated position of the reference point. Updating the initial position of the reference point as the next calibrated position of the reference point helps reduce accumulated error associated with the determined estimated position. The accumulated error, also referred to as drift error, causes the estimated position of the reference point to “drift” away from the actual position of the reference point over time. 
     The imaging device  135  generates slow calibration data in accordance with calibration parameters received from the VR console  110 . Slow calibration data includes one or more images showing observed positions of the locators  120  that are detectable by the imaging device  135 . The imaging device  135  may include one or more cameras, one or more video cameras, any other device capable of capturing images including one or more of the locators  120 , or some combination thereof. Additionally, the imaging device  135  may include one or more filters (e.g., used to increase signal to noise ratio). The imaging device  135  is configured to detect light emitted or reflected from locators  120  in a field of view of the imaging device  135 . In embodiments where the locators  120  include passive elements (e.g., a retroreflector), the imaging device  135  may include a light source that illuminates some or all of the locators  120 , which retro-reflect the light towards the light source in the imaging device  135 . Slow calibration data is communicated from the imaging device  135  to the VR console  110 , and the imaging device  135  receives one or more calibration parameters from the VR console  110  to adjust one or more imaging parameters (e.g., focal length, focus, frame rate, ISO, sensor temperature, shutter speed, aperture, etc.). 
     The VR input interface  140  is a device that allows a user to send action requests to the VR console  110 . An action request is a request to perform a particular action. For example, an action request may be to start or end an application or to perform a particular action within the application. The VR input interface  140  may include one or more input devices. Example input devices include: a keyboard, a mouse, a game controller, or any other suitable device for receiving action requests and communicating the received action requests to the VR console  110 . An action request received by the VR input interface  140  is communicated to the VR console  110 , which performs an action corresponding to the action request. In some embodiments, the VR input interface  140  may provide haptic feedback to the user in accordance with instructions received from the VR console  110 . For example, haptic feedback is provided when an action request is received, or the VR console  110  communicates instructions to the VR input interface  140  causing the VR input interface  140  to generate haptic feedback when the VR console  110  performs an action. 
     The VR console  110  provides media to the VR headset  105  for presentation to the user in accordance with information received from one or more of: the imaging device  135 , the VR headset  105 , and the VR input interface  140 . In the example shown in  FIG. 1 , the VR console  110  includes an application store  145 , a tracking module  150 , and a virtual reality (VR) engine  155 . Some embodiments of the VR console  110  have different modules than those described in conjunction with  FIG. 1 . Similarly, the functions further described below may be distributed among components of the VR console  110  in a different manner than is described here. 
     The application store  145  stores one or more applications for execution by the VR console  110 . An application is a group of instructions, that when executed by a processor, generates content for presentation to the user. Content generated by an application may be in response to inputs received from the user via movement of the HR headset  105  or the VR interface device  140 . Examples of applications include: gaming applications, conferencing applications, video playback application, or other suitable applications. 
     The tracking module  150  calibrates the VR system  100  using one or more calibration parameters and may adjust one or more calibration parameters to reduce error in determination of the position of the VR headset  105 . For example, the tracking module  150  adjusts the focus of the imaging device  135  to obtain a more accurate position for observed locators on the VR headset  105 . Moreover, calibration performed by the tracking module  150  also accounts for information received from the IMU  130 . Additionally, if tracking of the VR headset  105  is lost (e.g., the imaging device  135  loses line of sight of at least a threshold number of the locators  120 ), the tracking module  140  re-calibrates some or all of the system environment  100 . 
     The tracking module  150  tracks movements of the VR headset  105  using slow calibration information from the imaging device  135 . The tracking module  150  determines positions of a reference point of the VR headset  105  using observed locators from the slow calibration information and a model of the VR headset  105 . The tracking module  150  also determines positions of a reference point of the VR headset  105  using position information from the fast calibration information. Additionally, in some embodiments, the tracking module  150  may use portions of the fast calibration information, the slow calibration information, or some combination thereof, to predict a future location of the headset  105 . The tracking module  150  provides the estimated or predicted future position of the VR headset  105  to the VR engine  155 . 
     The VR engine  155  executes applications within the system environment  100  and receives position information, acceleration information, velocity information, predicted future positions, or some combination thereof of the VR headset  105  from the tracking module  150 . Based on the received information, the VR engine  155  determines content to provide to the VR headset  105  for presentation to the user. For example, if the received information indicates that the user has looked to the left, the VR engine  155  generates content for the VR headset  105  that mirrors the user&#39;s movement in a virtual environment. Additionally, the VR engine  155  performs an action within an application executing on the VR console  110  in response to an action request received from the VR input interface  140  and provides feedback to the user that the action was performed. The provided feedback may be visual or audible feedback via the VR headset  105  or haptic feedback via the VR input interface  140 . 
       FIG. 2A  is a diagram of a virtual reality (VR) headset, in accordance with an embodiment. The VR headset  200  is an embodiment of the VR headset  105 , and includes a front rigid body  205  and a band  210 . The front rigid body  205  includes an electronic display  115 , the IMU  130 , the one or more position sensors  125 , and the locators  120 . In the embodiment shown by  FIG. 2A , the position sensors  125  are located within the IMU  130 , and neither the IMU  130  nor the position sensors  125  are visible to the user. 
     The locators  120  are located in fixed positions on the front rigid body  205  relative to one another and relative to a reference point  215 . In the example of  FIG. 2A , the reference point  215  is located at the center of the IMU  130 . Each of the locators  120  emit light that is detectable by the imaging device  135 . Locators  120 , or portions of locators  120 , are located on a front side  220 A, a top side  220 B, a bottom side  220 C, a right side  220 D, and a left side  220 E of the front rigid body  205  in the example of FIG.  2 A. 
       FIG. 2B  is a cross section  225  of the front rigid body  205  of the embodiment of a VR headset  200  shown in  FIG. 2A . As shown in  FIG. 2B , the front rigid body  205  includes an optical block  230  that provides altered image light to an exit pupil  250 . The exit pupil  250  is the location of the front rigid body  205  where a user&#39;s eye  245  is positioned. For purposes of illustration,  FIG. 2B  shows a cross section  225  associated with a single eye  245 , but another optical block, separate from the optical block  230 , provides altered image light to another eye of the user. 
     The optical block  230  includes an electronic display  115 , and the optics block  118 . The electronic display  115  emits image light toward the optics block  118 . The optics block  118  magnifies the image light, and in some embodiments, also corrects for one or more additional optical errors (e.g., distortion, astigmatism, etc.). The optics block  118  directs the image light to the exit pupil  250  for presentation to the user. 
       FIG. 3A  is a top view and  FIG. 3B  is a cross section of an electronic display  115 , in accordance with an embodiment. In one embodiment, the electronic display  115  is a LCD device including a LC panel  310 , BLU  320 , a data driver  330 , and a controller  340 . The LC panel  310  covers the BLU  320  and includes a pixel area  302  comprising a plurality of rows of pixels including a first row  304  and a last row  306  of pixels. A cross section of the pixel area  302  along line  312  is shown in  FIG. 3B  and shows the LC panel  310  covering the BLU  320 . 
     The BLU  320  includes a light source (not shown) that is an electrical component that generates light. The light source may comprise a plurality of light emitting components (e.g., light emitting diodes (LEDs), light bulbs, or other components for emitting light). In one aspect, intensity of light from the light source is adjusted according to a backlight control signal from the controller  340 . The backlight control signal is a signal indicative of intensity of light to be output for the light source. A light source may adjust its duty cycle of or an amount of current supplied to the light emitting component (e.g., LED), according to the backlight control signal. For example, the light source may be ‘ON’ for a portion of a frame time, and ‘OFF’ for another portion of the frame time, according to the backlight control signal. Example operations of the BLU  320  are further described in detail below with respect to  FIGS. 4A to 4E . The BLU  320  projects light from the light source towards the LC panel  310 . The BLU  320  may include a light guide plate and refractive and/or reflective components for projecting light towards the LC panel  310 . The light guide plate may receive light with different colors from light sources, and may project combined light including a combination of the different colors towards the LC panel  310 . 
     The LC panel  310  includes a bottom substrate  322 , a top substrate  324 , and LC material  326  between the bottom and top substrates  322  and  324 . Although not shown in  FIG. 3B , the bottom substrate  322  may include driver pixel circuitry and transparent pixel electrodes, and the top substrate  324  may include color filters, a black matrix, and transparent conductive electrodes. Also, spacers may be used to control the spacing between the top substrate and the bottom substrate, although not shown in  FIG. 3B . The LC material  326  is placed between the top and bottom substrate  322  and  324 . 
     The data driver  330  is coupled to the LC panel  310  and writes display data to pixels in the pixel area  302  of the LC panel  310 . Although shown as a separate component, the data driver  330  may be included in the LC panel  310 . The data driver  330  writes the display data in a scan direction  314  from a first row  304  to a last row  306  of pixels in the pixel area  302 . The display data written to a pixel may be in the form of an analog voltage that may be applied across electrodes on the bottom and/or top substrate  322  and  324  of a pixel to change the orientation of LC material  326  in the LC panel  310 . The change in orientation of the LC material  326  allows a portion of the light from the BLU  320  to reach a user&#39;s eye  245 . 
     The controller  340  is a circuit component that receives an input image data and generates control signals for driving the data driver  330  and BLU  320 . The input image data may correspond to an image or a frame of a video in a VR and/or AR application. The controller  340  instructs the data driver  330  to write data to the LC panel  310  to control an amount of light from the BLU  320  to the exit pupil  250  through the LC material  326 . The controller  340  generates the backlight control signal for turning ON or OFF the BLU  320 , as described in more detail for  FIGS. 4A   4 E. In other embodiments, the electronic display  115  includes different, more or fewer components than shown in  FIGS. 3A and 3B . For example, the electronic display  115  may include a polarizer and a light diffusing component. 
     GI and BI Modes for LCDs in VR Headset 
     The electronic display  115  in a VR headset has certain requirements such as a short duty cycle to prevent image streaking and short illumination times to reduce latency. While the electronic display  115  could be a Liquid Crystal Display (LCD), LCDs are currently one or two orders of magnitude slower than active matrix OLED displays (AMOLEDs). The switching time associated with the liquid crystal (LC), or the amount of time required for the LC to change state, may take several milliseconds (ms), making it difficult to achieve a short duty cycle with LCDs and limiting the speed of LCDs. In addition, normal mode of an LCD has the backlight unit (BLU) always turned on and do not have short illumination times. To improve LCD performance in a VR headset, a shorter duty cycle and illumination time may be achieved by using alternative operating modes for LCDs such as a global illumination (GI) mode or a black insertion (BI) mode. 
     In the GI mode, the backlight of a display turns on only after a frame of data is written (data scan out and charging) and all the LCs in a display have completed a change of state. An initial portion of the frame time is for the data scan out and charging to occur, a middle portion of the frame time is for the LC switching time, and a final portion of the frame time is for the BLU illumination. 
       FIG. 4A  shows an example frame time for a 90 Hz LCD in GI mode according to one embodiment. During a frame time of 11 ms, the data scan out and charging may take an initial 3 ms of the frame time, the LC material may take the next 6 ms of the frame time to transition, and the illumination of the BLU may take the last 2 ms of the frame time. 
     In BI mode, the data scan out and charging for a frame of data may be written during the entire frame time and the backlight of a display is turned on only during a final portion of each frame cycle. In this mode, the BLU may turn on during the data scan out and charging or during the LC switching time for some pixels of the LCD. The resulting image that is shown during the illumination portion of the BLU may include compromised pixels which have not completed the LC transition to the state indicated by the written data, and old pixels from a previous frame which are being updated during the illumination portion of the BLU. 
       FIG. 4B  shows an example frame time for a 90 Hz LCD in BI mode according to one embodiment. During a frame time of 11 ms, the data scan out and charging may take the full frame time of 11 ms. The illumination of the BLU may turn on during the last 2 ms of the frame time (e.g., approximately 20% of the frame time). During the illumination portion of the BLU, pixels updated during the first 3 ms of the frame time displays data that is updated and correct; pixels updated during the next 3 ms to 9 ms of the frame time may be in a compromised state, and pixels updated during the last 2 ms of the frame time may display old images from a previous frame. In a LCD running with BI mode where the pixels are updated from a top row to a bottom row, the bottom rows of the LCD may display compromised or old image data. 
     Embodiments of GI mode and BI mode are further described in U.S. Provisional Patent Application No. 62/326,286 filed on Apr. 22, 2016 and U.S. Provisional Patent Application No. 62/325,920, filed on Apr. 21, 2016, which are hereby incorporated by reference herein in their entirety. 
     Multiple Driver ICs for GI or BI Mode LCD 
     An LCD in a VR headset in GI or BI mode can benefit from multiple data driver integrated circuits (DIC) to read data voltages in the pixels. In a typical LCD, there is a single DIC to write data to pixels of the LCD. Having multiple DICs to write pixel data simultaneously to different pixels of a display may increase the time a single DIC has to write data to pixels of the LCD within a frame and increase the speed of the LCD. For an LCD with a single DIC, the DIC may have a predetermined amount of time to write a frame of data. With multiple DICs (n number of DICs) a single DIC has the same predetermined amount of time to write less data (1/n of a frame of data) or a single DIC may complete writing the data in a shorter amount of time (1/n of a predetermined amount of time) to allow the LCD to run at faster speeds. 
       FIG. 4C  is a diagram illustrating a frame cycle 90 Hz LCD using two data driver ICs in global illumination mode in accordance with an embodiment. During a frame time of 11 ms, the first and second DICs (DIC 1  and DIC 2 ) take an initial 3 ms of the frame time for data scan out and charging, the LC material may take the next 6 ms of the frame time to transition, and the illumination of the BLU may take the last 2 ms of the frame time. In this embodiment, DIC 1  has 3 ms for data scan out and charging of one half frame of data, and DIC  2  has 3 ms for data scan out and charging of the other half frame of data. In comparison, a single DIC has 3 ms for data scan out and charging of an entire frame of data in the baseline GI mode LCD embodiment of  FIG. 3A . 
       FIG. 4D  is a diagram illustrating a frame cycle of a 90 Hz LCD using two driver ICs in black insertion mode in accordance with an embodiment. During a frame time of 11 ms, the first and second DICs (DIC  1  and DIC  2 ) take the entire frame time of 11 ms for data scan out and charging and the illumination of the BLU may take the last 2 ms of the frame time. In this embodiment, DIC  1  has 11 ms for data scan out and charging of one half frame of data and DIC  2  has 11 ms for data scan out and charging of the other half frame of data. In comparison, a single DIC has 11 ms for data scan out and charging of an entire frame of data in the baseline BI mode LCD embodiment of  FIG. 3B . 
     Multiple Driver ICs for Hybrid Mode LCD 
     The LCD could also operate in a hybrid mode (combination of GI and BI modes) in which an initial portion of the frame time is for data scan out and charging, the remaining portion of the frame time is for the LC material to transition, and a part of the remaining portion is used for the illumination of the BLU. In the hybrid mode, a portion of frame time for the data scan out and charging is smaller than the portion of time set for a BI mode, but larger than the portion of time set for a GI mode. The remaining amount of frame time may be for the LC switching time, and the BLU turns on during a final portion of the frame time. Similar to the GI mode, the BLU does not turn on during the data scan out and charging period of the time frame. However, unlike the GI mode, the BLU may turn on during the LC switching time for some pixels of the LCD. The resulting image is similar to the BI mode in that the image shown during the illumination of the BLU may include compromised pixels which have not completed the LC transition to the state indicated by the written data. However, unlike the BI mode, old images from a previous frame would not show up during the illumination of the BLU since all pixels were updated during the initial data scan out and charging period. 
       FIG. 4E  is a diagram illustrating a frame cycle of a 90 Hz LCD using two data driver ICs in hybrid mode in accordance with an embodiment. During a frame time of 11 ms, the first and second DICs (DIC  1  and DIC  2 ) take the initial 5 ms of the frame time for data scan out and charging, the remaining 6 ms of the frame time for LC material to transition, and the last 2 ms of the frame time (overlapping the LC switching time) for the illumination of the BLU. In this embodiment, DIC  1  has 5 ms for data scan out and charging for one half frame of data and DIC  2  has 5 ms for data scan out and charging of the other half frame of data. In comparison, an embodiment using a single DIC would have 5 ms to write an entire frame of data. 
     Scan Direction for Multiple Driver ICs 
       FIG. 5A  is a diagram illustrating an LCD using two DICs with one scan direction in accordance with an embodiment. In this embodiment, the first DIC  520  and second DIC  522  are located at the top of the pixel area  510  of an LCD. Alternatively, the first DIC  520  and second DIC  522  could be located at the bottom of the pixel area  510 . In one embodiment, the first DIC  520  could write data to even pixel columns and the second DIC  522  could write data to odd pixel columns of an LCD. The scan direction is indicated by arrow  430  from a top to a bottom row of the pixel area  510 . In this embodiment, one scan driver could be used to scan the rows of pixels and the data lines are arranged such that the even data lines are connected to one DIC and the odd data lines are connected to another DIC. 
       FIG. 5B  is a diagram illustrating an LCD using two data driver ICs with two scan directions in accordance with an embodiment. In this embodiment, the first DIC  560  and the second DIC  562  are on opposite sides of the pixel area  550 . The first DIC  560  is located above the pixel area  550  and the second DIC  562  is located below the pixel area  550 . The first DIC  560  may write data to pixels covering an upper half of the pixel area  550 . The second DIC  562  may write data to pixels covering a lower half of the pixel area  550 . The scan direction for the first DIC  560  may be in an upward direction, starting at a row located at or just above the middle row of the display and ending at the top row of the display, as indicated by scan direction  580 . The scan direction for the second DIC  562  may be in a downward direction, starting at a row located at or just below the middle row of the display and ending at the bottom row of the display, as indicated by scan direction  582 . This embodiment includes two separate scan drivers for scanning the upper and lower halves of the active area, and the data lines in the top and bottom areas are cut in half, extending only half of the active area. This embodiment may have advantages for a BI mode LCD or hybrid mode LCD. In BI mode, the last pixels to be written may be compromised or contain data from old pixels. In this case, according to scan direction  580  and  582 , the last pixels to be updated would be at the top or bottom of the display. It is likely that the eye of a user is focused for the most part at the central area  570  of the display. While using such an embodiment for BI mode LCD, the pixels containing compromised or old pixel data will be in the top and bottom rows and not in the center area  570  of the LCD. While using such an embodiment for hybrid mode LCD, the pixels containing compromised data will be in the top and bottom rows and not in the center area  570  of the LCD. 
     Although  FIGS. 4C-4E and 5A-5B  illustrate embodiments having only two DICs, other embodiments may include multiple DICs such as three or four DICs.  FIGS. 5A-5B  show placement of DICs as being at the top and bottom locations bordering the pixel area of a display. However, DICs may be placed in other configurations, such as the right and left sides of the pixel area. 
     Additional Configuration Information 
     The foregoing description of the embodiments has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the patent rights to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure. 
     The language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the patent rights be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments is intended to be illustrative, but not limiting, of the scope of the patent rights, which is set forth in the following claims.