What are wearables?
Wearable computers, also called ‘wearables’, are technological devices that can be worn as clothing or accessories. Some wearables are based on relatively simple technology, similar to a scaled-down desktop computer, but some involve innovative technologies. Wearables include different products, such as fitness bands, wearable headsets, smart watches, healthcare monitoring and displays embedded in textiles.
The wearables market is diverse, but faces similar challenges like minimizing size and weight of components, deciding on optimal display location, choosing suitable services and applications to provide and balancing cost-to-price ratios.
What are OLEDs?
OLED is a light-emitting diode built from thin films of organic electroluminescent material sandwiched between electrodes. Since the materials are luminescent, they produce light when the current is run through them. No other display technology creates light directly like this: LCDs use color filters and light-blocking liquid crystals above a light-creating backlight. Plasmas use UV light created by igniting pockets of gas to excite phosphors.
This means that OLED screens are thinner, lighter, more efficient and offer better performance and color quality than other existing technologies. Each pixel can be shut off, providing absolute black and amazing contrast ratio.
Most OLEDs use a glass substrate, but much effort is put into developing OLEDs with plastic substrates and many companies have ongoing Plastic OLED development projects. Plastic OLEDs can be made thinner and lighter than glass ones, as well as more durable as they are much less prone to shattering. They can also present a flexible form and even cost less. However, plastic OLEDs present several manufacturing challenges that currently impede their use, like plastics that can stand high temperatures, appropriate coating and encapsulation processes and more.
AMOLED vs. PMOLED
The "AM" in AMOLED stands for "active matrix", a way of running an OLED screen that's better for motion (like video). Each pixel can be addressed individually, which is what you want in, for example, a television. AMOLEDs can also be made much larger than PMOLED and have no restriction on resolution.
Passive matrix OLEDs, or PMOLEDs, use a simpler control scheme to control rows or columns rather than individual pixels. They are cheaper and easier to make, but also less efficient and suffer from lower lifetime, as well as size and resolution restrictions. They are typically used to display character data or small icons and are currently being used in MP3 players, mobile phone sub displays, etc. Here's more information about AMOLED vs. PMOLED technologies.