When engineers design a wearable device, such as a smartwatch, they have to be concerned about the cost of the materials and the cost of assembly. If the device costs too much to make, the company won’t be able to sell it for a profit. But there’s another budget that limits design choices just as much: the energy budget. And for devices with a display, the display often consumes the lion’s share of the electricity required to power the device. More energy efficient displays can mean that designers can use smaller batteries, resulting in thinner and lighter devices.
Last week, Japan Display Inc. (JDI) announced that they are now taking orders for their new “memory-in-pixel” LCD panels. These round displays are about 1.3 inches in diameter, and have a 320 by 300 color pixel resolution. The panels use a reflective technology that means there is no need for an energy-hungry backlight; the ambient light provides illumination, which also can help the display have better legibility in direct sunlight. The memory-in-pixel feature means that the image data is stored in a memory element at each pixel location. This saves power because the controller only has to send information to the display when the content changes.
According to JDI, these new panels draw 0.5% as much power than a traditional transmissive LCD panel with a backlight. Considering just the display, this means that a battery would last 200 times longer with this new display. Or designers could use a battery 200 times smaller and get the same lifetime between charges. This approach could lead to thinner smartwatches that go much longer on a single charge.