Apple invents a unique lighting system for Foldable Devices that implements separate brightness controls for the 2 Display Halves
While Patently Apple has posted many reports on foldable devices over the years, as seen in our archives, it took until March 2021 before an Apple patent clearly spelled out the fact that one of their future foldable devices would in fact be a laptop. Apple clarified that point in 19 out of 20 of new patent claims that our report highlighted.
On Thanksgiving, the US Patent & Trademark Office published a patent application from Apple titled "Systems and Methods for Brightness or Color Control in Foldable Displays."
Apple's patent covers systems and methods for brightness or color control for a foldable display to mitigate image artifacts due to viewing conditions of different areas of the foldable display.
Electronic displays may take the form of foldable displays. Foldable displays may fold or roll up to take a variety of shapes. For example, some foldable displays may have a hinged region where two areas of the foldable display can fold inwards and/or outwards. This may give a foldable display capabilities not possible for a flat display.
For instance, foldable displays, when in a folded state, may utilize the top half of the display to display media content (e.g., mobile applications, videos, websites) and utilize the bottom half of the display as an input medium (e.g., using a touch-based keyboard or trackpad), to display a logo, to display date and time information, or to display other information.
If a foldable display utilizes a constant brightness setting for the entire display regardless of whether the display is folded, different areas of the folded display may have different normal (perpendicular) axes of light emission. That is, one area of the folded display may be folded to point toward a person's eyes while another area is not.
In some types of displays, the apparent luminance of the display will depend on the angle of emission, relative to the display normal direction (perpendicular to the display surface). In these cases, the “on-axis” light emission that is emitted in a normal direction can be noticeably different than “off-axis” light emission at some other angle (e.g., 45°). In a display that is not flat, a person may see more light coming from the area of the folded display that is folded to point toward a person's eyes, even if both areas of the of the folded display have the same amount of on-axis light emission.
This may affect not just the brightness, but also the color, viewed from the different areas of the folded display. This is because different color components (e.g., red, green, or blue display pixels) may emit more or less light off-axis in relation to on-axis.
The difference in brightness or color between two folded areas of the foldable display could produce an image artifact, as the user expects reasonably constant viewing characteristics. Viewing the foldable display in a dark room or low-light setting could amplify this effect. Thus, the ability to adjust the brightness of foldable displays can enable an improved viewing experience for the user and provide a power saving benefit.
To reduce power emission and adjust brightness of the foldable display, the foldable display may implement separate brightness control algorithms and/or driving architecture for different portions of the display, such as each half of the display for a display that folds in the middle.
For example, when a display is folded the top half of the display may display media content and the bottom half of the display may function as a keyboard or other input medium. Under some conditions, particularly during low light conditions, display viewing experience may be impacted. The display may implement different special modes (e.g., pre-adjusted or dynamically adjusted settings based on environmental conditions) for different folded areas of the display (e.g., when the folded display is folded in half, each half of the folded display may have different settings), to aid in ease of viewing experience. For example, during a low-light or nighttime scenario, the display may apply a color shift mode (e.g., Night Shift® by Apple Inc.) that involves dimming down blue light for the top half of the display.
As noted above, the color and luminance of the foldable display relative to the viewer may also be altered based on viewing angle and viewer eye position. This can lead to a lower quality viewing experience for the user based on fold angle of the display and/or the viewer's eye position relative to the display. The ability of eye position to be tracked and/or determined can enable foldable displays to dynamically adjust luminance and color output to enable an optimal viewing experience for the user.
In one example, the eye position relative to the display may be determined by a camera, proxy sensor, a face recognition system (e.g., Face ID® by Apple Inc.), folding angle of the display, or any other eye tracking method.
The luminance and/or color of the display may then be adjusted utilizing an algorithm taking into account fold angle and viewer eye position to adjust for optimal viewing conditions. The luminance and color of the foldable display may also be adjusted by the system by utilizing fold angle data and an estimated eye position in situations where an eye tracker component is not available.
Apple's patent FIG. 7 below is an unfolded view and folded view of an inwardly folding display; FIG. 8 is an unfolded view and folded view of an outwardly folding display.
Apple's patent FIG. 20 above is a diagram illustrating a method of manual color and luminance compensation for the foldable display; FIG. 22 is a diagram illustrating a foldable display that may perform semi-automatic and automatic color and luminance compensation.
For more details, review Apple's patent application number US 20220375388 A1
Shatam Agarwal: Display Analog/Mixed-Signal Architect
Hyunsoo Kim: Display EE Engineer
Henry Nho: Sr. Engineering Manager / Principal Engineer
Mahdi Baroughi: Display Electrical Engineering Manager
Hoon Kim: Product Design / New Technology (Special Project Group)