On June 28, 2012, the US Patent & Trademark Office published a patent application from Apple that reveals a system and method to improve image edge discoloration. Yet at the heart of the patent, Apple states that "some embodiments of the LCD panel may be a model of the Retina display, available from Apple Inc." So if you want to know the lowdown on Apple's Resolutionary display, or at least certain aspects of this magical beast, it's now here for you to feast your eyes on.
Apple's Patent Background
Liquid crystal displays (LCDs) are commonly used as screens or displays for a wide variety of electronic devices, including such consumer electronics as televisions, computers, and handheld devices (e.g., cellular telephones, audio and video players, gaming systems, and so forth). Such LCD devices typically provide a flat display in a relatively thin package that is suitable for use in a variety of electronic goods. In addition, such LCD devices typically use less power than comparable display technologies, making them suitable for use in battery-powered devices or in other contexts where it is desirable to minimize power usage.
LCDs typically include an LCD panel having, among other things, a plurality of picture elements (pixels) arranged in a matrix to display an image. Each pixel may include sub-pixels (e.g., red, blue, and green sub-pixels) which variably permit light to pass when an electric field is applied to a liquid crystal material in each sub-pixel. However, adjacent columns of sub-pixels in an LCD panel may be susceptible to electrical coupling (also referred to as crosstalk), which may manifest as undesirable visual artifacts in the LCD display.
Moreover, due to the arrangement of sub-pixels in a pixel matrix and/or due to the images to be displayed by the LCD, crosstalk may sometimes have non-uniform affects over a display area, resulting in non-uniform visual artifacts in the displayed image. In particular, edge discoloration along edges of a display active area or along edges of a displayed object may result from such crosstalk effects.
Techniques found in Apple's invention relate to systems and methods for reducing edge discoloration in an LCD display. An LCD display typically includes a matrix of pixels, defined by columns and rows of sub-pixels (i.e., red, blue, and green sub-pixels in each pixel). Due to the configuration of a typical pixel matrix, coupling, interference, or other electromagnetic effects may occur between sub-pixel columns. Such effects may result in undesirable visual artifacts such as edge discoloration in the display area and/or edge discoloration in an object displayed on the LCD. Edge discoloration may refer to a non-uniformity in light transmittance through a first sub-pixel column (e.g., a left edge of the display or object) and a last sub-pixel column (e.g., a right edge of the display or object) with respect to the light transmittance through other sub-pixels in the display or in the object (e.g., the sub-pixels between the left and right edges). The non-uniformity in light transmittance may include, for example, a higher light transmittance through the first and last sub-pixel columns of a display or of an object due to relatively higher crosstalk between sub-pixels in the other portions of the display.
One or more embodiments involve techniques for dimming the first and last sub-pixel columns of a display to mitigate edge discoloration. For example, to reduce edge discoloration in a display area, a black mask over the first and last columns of sub-pixels may be configured to reduce light transmittance through those sub-pixels, or electrodes in the relevant sub-pixels may be shaped for reduced light transmittance. Furthermore, software may be utilized to automatically reduce the brightness of the first and last sub-pixel columns.
Embodiments also include techniques for mitigating edge discoloration in objects displayed on the LCD. In some embodiments, software may be used to detect edges of objects within the display area. Once object edges are detected, the last sub-pixel of the background and/or the first sub-pixel of the object are driven to reduce edge discoloration perceptibility. In some embodiments, each sub-pixel may be configured with a coupling extrusion on the pixel electrode to control a coupling effect between the neighboring sub-pixels to reduce edge discoloration perceptibility.
Apple's patent FIGS. 7A and 7B shown below are illustrations of edge discoloration in objects displayed by the LCD. In Apple's patent FIGS. 14A and 14B compare a finger electrode configuration in a typical sub-pixel with a finger electrode having a coupling extrusion in a sub-pixel configured to reduce edge discoloration.
Apple's patent FIG. 9 is a diagram representing a black mask and the corresponding sub-pixels covered by the black mask; Apple's patent FIGS. 10A and 10B are diagrams representing a view of a pixel matrix in the LCD of FIG. 4 and a view of the black mask over the pixel matrix; and patent FIG. 11 is a diagram representing finger electrodes in a row of sub-pixels as is shown in our cover graphic from Apple's Retina Display video.
Apple's patent application was originally filed in Q4 2010 by inventors Cheng Chen Shih Chang, Mingxia Gu and John Zhong. This is a very complex patent, as you can imagine, and trying to abbreviate it would be a shame for the technically minded. Therefore – go ahead, feast your eyes.
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