So here is the scoop: To enhance the battery life of a mobile device, Palm had the ingenious idea to take away the color of your screen when battery power is dwindling down. Before the technocrats among you indulge in sneers and laughter, listen to how
US patent 7002569 describes it:
In one embodiment, the electronic device is a hand held computer system with a display device. When the battery level is detected as below a preselected level, a message is generated on the computer display screen. The message informs the user that the display mode of the screen can be changed to enhance the battery life. If selected, the display mode can change from color to monochrome thereby saving power because the monochrome display does not utilize a back-lighting element. In one embodiment, color sequential techniques are used to provide a flat panel color display. Within the display, a transreflective layer provides reflective light for monochrome applications. When the battery energy returns to normal levels, the color display mode can be re-entered automatically. It is appreciated that the display mode changes can also be performed automatically if the battery level falls below certain critical levels.
Attached you find a diagramm which illustrates this invention. As you perhaps know, the biggest drain on mobile devices is the LCD screen; and the single greatest culprit that contributes to an LCD's power usage is the backlight. Every transreflective LCD is backlit by a small, fluorescent (CCF) tube. The brighter you want your screen to be, the harder that tube has to work. The energy it takes to power that tube in what the industry considers a "typical" setting accounts for roughly 75 percent of the total LCD power usage.
This is where Palm's invention comes into play. Once the system detects that the battery runs low, it turns your device's screen from color to monochrome. This effectively reduces battery consumption of the display by up to 75 percent as monochrome screens don't require the backlight to stay on. Once your battery is being recharged and exceeds a predetermined level again, the system automatically places the display back into color mode. One thing's for sure: the monochrome display may not only give you more power to pass the time while you're bored on the subway or waiting for the movie to start, but it will also stir a nostalgic rush of good old memories.