A recently published patent application suggests Apple is exploring ways to incorporate e-ink display technology into its iPhone, iPad, and iPod touch. And unlike other e-ink devices, Apple's hybrid system would be able to display sharp text in a range of lighting situations without sacrificing the ability to display full color, video, and graphics.

The application, Systems and Methods for Switching Between an Electronic Paper Display and a Video Display, was originally filed in October 2009. It describes a hybrid system that employs a combination of "electronic paper" with a more traditional color LCD or OLED display to gain the advantages of both display types. Such a display would be formed by sandwiching a transparent e-ink screen between a backlit color LCD or OLED panel on the bottom and a touch-sensitive glass panel on the top. The color display could display full color graphics and video, while the e-ink layer could display sharp text.

While that description sounds somewhat similar to Pixel Qi's hybrid e-ink displays which can switch between e-ink and color LCD modes, Apple's patent takes things a couple steps further. Control circuitry would analyze the video input and could switch modes depending on the type of content. Furthermore, the control circuitry could independently switch different areas of the screen to either mode as needed. For instance, a webpage may have a range of text with an inline video. The system could display razor-sharp text using e-ink, while the video is displayed using the underlying color display.

One particular feature of the system, according to the application, is that the control circuitry in particular analyzes the video input to determine how fast different elements are changing. If the rate of change exceeds the refresh rate of the e-ink display, the color display would take over. Imagine the webpage in the preceding example: if you scroll the page quickly, the color display would be used to smoothly animate the scrolling. Once the scrolling stopped, however, the e-ink display would take over for the text once again.

Apple files numerous patents every year, so the mere fact that Apple filed a patent for a hybrid e-ink display is no guarantee that it will incorporate the technology into a future product. However, the technology could particularly enhance the iPad for e-book reading purposes. The iPad's current display is great for reading books heavy on color images or that contain motion graphics or video, but the relatively low pixel density and backlit screen still makes reading long passages of text tiresome for many users. Many readers tend to prefer e-ink based devices like Amazon's Kindle for this reason.