Patent Background

Liquid crystal displays (LCDs) are commonly used as screens or displays for a wide variety of electronic devices, including consumer electronics such 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.

Typically, LCD panels include an array of pixels for displaying images. Image data related to each pixel may be sent by a processor to the LCD panel through a driver integrated circuit (IC). The driver IC then processes the image data and transmits corresponding voltage signals to the individual pixels. Typically, the method by which the driver IC receives and processes the image data is well suited for receiving certain types of image data, such as video images for example, but not as well suited for receiving other types of image data, such as still images.

Patent Summary

Embodiments of the present disclosure provide a system with a display that may operate in at least two display modes: a "frame-buffered" display mode, such as CPU-style interface, and a "streaming" display mode," such as an RGB-style interface. In the "frame-buffered" display mode, the processor writes image data to a frame memory of the driver IC as the image changes, and the driver IC periodically refreshes the display panel from the frame memory. In this method, the processor may reduce processing overhead by writing new image data to the driver IC frame memory only when some portion of the image changes. Furthermore, during periods when the image is still, the interface between the processor and the driver IC may be substantially unused, and the driver IC may continue to update the panel display from image data stored in the frame memory. Using this technique, the data transmission rate, i.e. the rate at which image data is transmitted from the processor to the driver IC, may be proportional to the degree to which the image changes, which may result in power savings if the image is updated infrequently. Therefore, this technique may work well for displaying images that are infrequently updated, such as menu images or word processing images, for example. However, because the processor updates the display by writing to driver IC memory, this technique may involve a higher level of processing overhead and power usage during periods of frequent image updates.

In the "streaming" display mode, the processor writes a continuous stream of image data to the driver IC, and the driver IC may process and route the streaming image data to the display panel without storing the data in a frame memory. In this method, the processor does not write to frame memory and, therefore, no memory addressing information may be included in the data stream. Using this technique, the processing overhead involved in writing data to the driver IC memory may be reduced. Therefore, this technique may work well for displaying images that change extensively over time, such as video images for example. In the streaming display mode, however, the processor continuously sends image data to the driver IC to refresh the display regardless of whether the displayed image is actually changing. Therefore, the processing overhead and power usage associated with transmitting data to the driver IC may remain the same even when the image data is updated infrequently.

In a typical electronic device with an LCD display, the method by which image data is sent to the driver IC is usually pre-determined according to the most common type of image data that is expected to be displayed and the resulting tradeoffs between power usage and memory cost. For example, an LCD television or media player may operate in a streaming display mode, i.e., using an RGB-style interface. This may reduce the cost of the display by eliminating the frame memory and may also reduce the processing overhead and power usage associated with addressing memory.

Types of Display Technology

The display may be used to display various images generated by a television (or any Apple device with a display). The display may be any suitable display such as a liquid crystal display (LCD), plasma display, or an organic light emitting diode display, for example. In one embodiment, the display may be an LCD employing in-plane switching (IPS), twisted nematic, electrically compensated birefringence, or other techniques useful in operating such LCD devices.

Apple's patent FIG. 3 is a more detailed block diagram of the processor and the source driver; FIG. 4 is a flow diagram illustrating a method of switching from a frame-buffered display mode to a streaming display mode.

Obsessed Over Quality

In a second related patent found today under number 20100225571, Apple discusses a new display architecture in great detail that provides independent adjustment of gamma with respect to each color channel of a display.

Apple's patent FIG. 4 illustrates a process flow diagram 80 depicting how image data may be processed by gamma block, displayed by an LCD panel and perceived by a user.

Apple credits Kapil Sakariya and Wei Yao as the inventors of patent application 20100225657, originally filed in Q1 2009.

Notice: Patently Apple presents only a brief summary of patents with associated graphic(s) for journalistic news purposes as each such patent application is revealed by the U.S. Patent & Trade Office. Readers are cautioned that the full text of any patent application should be read in its entirety for further details. About Comments: Patently Apple reserves the right to post, dismiss or edit comments.