Without a doubt there's a race going on behind the scenes in Techland to see who will be first to market with a killer flexible display device. Apple has at least two patent filings regarding flex displays (one, two), and Samsung has at least one that we're aware. Now enters Microsoft with their first serious work in this area. Microsoft's patent filing illustrates a few examples of devices such as the one noted above in our cover graphic. Microsoft envisions various styles including foldable and more importantly, rollable designs with some very interesting added features. The depth of this patent filing tells us that we're likely to see more patents on this subject in the coming year. Although flex display based devices are likely a good five years away from being viable, the level of increasing patent activity in the industry regarding flex displays suggests that the race to be first may produce a mobile device with a flex display sooner rather than later.
One of the biggest complaints with today's mobile phones or other handheld or portable computing devices is the limited display size. Foldable displays have been suggested as one possible solution to this complaint. However, many proposed or prototype foldable display solutions may be impractical as the mechanical stress along folds may be too extreme to allow reliable operation over many folding cycles. Suggestions for rollable displays also have raised a number of potential problems. For example, most proposals for rollable displays use an active matrix in order to provide video capability. An active matrix, unfortunately, presents serious material issues for rollable displays as the transistors tend to fail under the repeated bending caused by rolling the displays.
In general, rollable displays could be divided into emissive and reflective types. OLED is the main emissive type proposed. OLED has a number of problems. One of the most serious problems is that OLED can't tolerate water vapor and require stringent hermetic sealing. For rollable OLED displays, this becomes a very difficult material issue to solve.
OLED also has relatively low light emission efficiency when compared to inorganic LEDs. Combining with the fact that OLED is a Lambertian light emitter and do not have directional gain, rollable OLED displays will consume significant amounts of power, thereby limiting their utility for portable devices. Reflective rollable displays in general have lower hermetic sealing requirements than OLED and may be closer to reality than the OLED ones. The manufacturability and durability issues, however, remain, especially given the fact that almost all of them require active matrix driving. Also, for most of them, video rate operation and good color rendition remain unsolved issues.
As an alternative to active matrix type displays, there are a several passive matrix displays that could potentially be rollable, but suffer other problems. For example, one recent technology, which could be viewed as an electrophoretic display with an air medium, uses electret particles, particles with semi-permanent electric charges, and could achieve video rate for smaller matrices. This technology suffers from limited reflectivity, especially in color mode, restricted color gamut, and potential durability issues. Further, electret particles may suffer from charge loss from impacts with the electrodes. In addition, humidity changes have been known to affect the threshold voltage needed for proper passive matrix operation.
Another type of passive matrix display referred to as MEMS is bistable and offers limited gray scale capability. However, the color gamut is relatively small. Unfortunately, the technology of such displays is relatively immature and currently even manufacturing of a rigid version is still in the planning stages. As such while MEMS type displays may provide viable solutions in the future, no such displays in foldable or rollable formats are currently commercially available.
Microsoft Invents Flexible Mobile Displays
In general, a "Flexible Mobile Display," as described herein, provides various techniques for implementing a flexible display that, in various embodiments, is foldable and/or rollable, combined with an optical or laser-based micro or pico projector to provide a user extensible display for mobile phones or other handheld or portable computing devices. In various embodiments, a short-throw pico or micro projector is used to reduce size requirements of the Flexible Mobile Display since a short-throw projector could be placed much closer to a display screen than a conventional or long-throw projector.
However, the use of a short-throw projector is not required. Because the Flexible Mobile Display is foldable and/or rollable, it could be implemented within a very small form factor using a variety of designs and configurations to provide an extensible display screen for use in mobile devices including, but not limited to, portable or mobile communications devices or cell phones, mobile gaming devices, mobile computing devices, eBooks, eReaders, remote control devices, etc.
The display screen of the Flexible Mobile Display is rollable and/or foldable, produces high contrast images in the native color range of the pico projector, provides optional directional gain, and could be easily manufactured. Further, by placing cameras or infrared detectors in a position to share the reverse of the optical path of the projector, the Flexible Mobile Display also provides both touch sensitivity on the display surface and/or limited imaging capabilities.
Note also that a wavelength-selective beam splitter, such as, for example, a dichroic mirror, could be used in the optical path to direct particular frequency ranges of light inputs (e.g., visible and infrared) to particular devices, thereby allowing those devices to be offset from the direct optical path of the pico projector. Further, optional pressure-based or capacitive touch sensors could be added to the display surface of the Flexible Mobile Display as an alternative to infrared-based touch sensing.
Advantageously, production of the Flexible Mobile Display uses an adaptation of currently available production techniques and is expected to be relatively low cost to produce. Additionally, in various embodiments, the Flexible Mobile Display also includes a low cost touch or multi-touch sensing mechanism that could be easily integrated into the overall system (using a variety of sensing techniques, including, for example, infrared, pressure, capacitive, etc.).
Further, another advantage of the Flexible Mobile Display is that it is small enough that it could easily be integrated into particular mobile devices, or could be coupled to existing devices via a wired or wireless video or data interface. Examples of wired interfaces include, but are not limited to VGA, DVI, HDMI, Display Port, IEEE 1394, Ethernet, etc. Examples of wireless interfaces include, but are not limited to, various 802.11 standards or other radio-frequency based interfaces.
In addition, because it is so small, prior to being extended for viewing purposes, the Flexible Mobile Display could be considered as a portable device by itself that could be coupled to any other portable device having appropriate interfaces for video, I/O and/or power, depending upon the specific implementation.
Flexible Multi-Layer Display
Further, the screen or display of the Flexible Mobile Display (generally referred to herein as a "flexible multi-layer display" portion of the Flexible Mobile Display) is passive, such that only the associated projector requires power. Although, depending on the embodiment, the flexible multi-layer display may include some low-power electronics (e.g., capacitive-based touch detection). Consequently, the Flexible Mobile Display is also very energy efficient. Note that energy efficiency could come from several sources. For example, contrast improvement from the screen optics (e.g., via rejection of ambient light) and/or optical gain of the screen as a result of a narrow light output angle will both reduce energy requirements for displaying a high contrast image.
Typical pico-projectors for projecting to arbitrary surfaces typically consume on the order of about 3 watts. However, one advantage of the Flexible Mobile Display is that when projecting onto the flexible multi-layer display portion of the Flexible Mobile Display, power requirements for the pico-projector are significantly reduced while achieving equivalent contrast levels.
Example of Flex Mobile Displays
Microsoft's patent FIG. 9 and FIG. 10 shown below illustrate simple examples of mobile devices within which the Flexible Mobile Display could be implemented. For example, patent FIG. 9 illustrates a portable communications device 900, such as a smartphone. In this example, a foldable embodiment of the Flexible Mobile Display 910 (having a footprint indicated by the broken line) is coupled or integrated into the portable communications device.
Clearly, there are a number of ways in which the Flexible Mobile Display could be integrated into the smartphone. One example is to mount or attach the Flexible Mobile Display to the bottom of the smartphone and then to extend the Flexible Mobile Display for use by pulling on the pull handle 400 or tab located on the right side of the smartphone.
Another way to provide the Flexible Mobile Display within the smartphone is to construct the smartphone as a type of clamshell device that opens to expose the internal Flexible Mobile Display which could then be extended for use by pulling on the pull handle or tab.
Microsoft's patent FIG. 10 provides a similar example to that of FIG. 9. However, in this example, a rollable embodiment of the Flexible Mobile Display 1010 is coupled to one side of a portable electronic device 1000, such as a gaming control or the like. In this example, the Flexible Mobile Display is extended for use by pulling on the pull handle or tab, but this time, it opens the Flexible Mobile Display while extending the extensible support rods 410 and unrolling a multi-layer passive display as you'll see in patent figure 7 below.
A Standalone Tube Design
In general, there is no need to tie the Flexible Mobile Display to a particular device. In fact, the Flexible Mobile Display could be constructed in a self-contained format as a standalone display device, similar to a computer monitor, that requires only a video signal input and a power source to operate. Consequently, it should be clear that Flexible Mobile Display could be constructed in various form factors, such as illustrated by FIG. 11, in a standalone embodiment.
For example, in patent FIG. 11 noted above we see an illustration of a standalone rollable embodiment of the Flexible Mobile Display wherein a pull handle or tab 1100 is used to extend a spring-loaded rollable embodiment of the multi-layer passive display 1110 from a housing, such as, for example, a storage tube 1130 or the like.
In this embodiment rigid or semi-rigid support rods 1115 are locked into place after the multi-layer passive display is extended to hold the multi-layer passive display in position during use, though the aforementioned extensible rods may also be used, if desired. These support rods are then removed to allow the multi-layer passive display to be retracted back into the storage tube when not in use.
Adding a Cool Pico Projector
Interestingly, Microsoft states that their standalone embodiment of the Flexible Mobile Display would include a micro or pico projector 1120 of patent FIG. 11 above. In addition, this embodiment of the Flexible Mobile Display may also include an optional camera 1150 and/or an optional infrared detector 1160. And unlike other embodiments, this standalone embodiment of the Flexible Mobile Display would also include a video/data IO port 1140 for receiving/sending video and/or touch or camera data and a power port 1145 for receiving power for the projector, camera and infrared detector.
Other Notable Patent Figures
About Microsoft Patent Figures: FIG. 5 provides an exemplary architectural view of a rollable and extensible embodiment of the Flexible Mobile Display, shown in a partially open position; FIG. 7 provides an exemplary architectural view of an extensible embodiment of the Flexible Mobile Display; and patent FIG. 12 illustrates an abstract sectional view of the flexible multi-layer display portion of the Flexible Mobile Display
Microsoft's patent application was originally filed under serial number 070336 in Q1 2011 and published by the US Patent and Trademark Office in Q3 2012.
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