Microdisplays are displays as small as a fingernail but can be of very high resolution. Thus, microdisplays are usually only used together with an optical system, enlarging the image from the microdisplay in front of the eye of the user or for any kind of projection. Well known applications enabled by the use of microdisplays are the beamer/projectors, electronic viewfinder (EV) in modern digital cameras as well as head mounted displays (HMDs) for Virtual or Augmented Reality applications.
Several technologies for microdisplays exists today:
- DMD: Digital Mirror Devices, a reflecting technology
- LCD: Liquid Crystal Devices, a transmitting technology
- LCoS: Liquid Crystal on Silicon, a reflecting technology
- OLED: OLED-based microdisplays, with integrated light source
Digital Mirror Devices (DMDs) are based upon MEMS technology in which very small mirrors are electrically adjusted to either reflect light coming from an external light source to the user or not to reflect. Color displays are realized by either using a RGB color wheel with three different (RGB) light sources or by combining three DLP, each with one color source, to the final image.
Liquid Crystal Display (LCD) based microdisplays are based on a transmitting technology, in which small liquid crystals are electrical orientated to either transmit or to block a light source. Color displays are realized by using three LCD microdisplays, each for one color of RGB and combine them to the final picture. For both microdisplays architectures external light sources and external driver and controller ICs are needed.
LCoS and OLED based microdisplays are both build upon silicon wafers and thus come usually with driver and basic controller circuitry integrated. OLED microdisplays go one step further and integrate even the light source as well, thus enabling much lower power solutions: In OLED microdisplays each pixel usually only needs power when it is driven on, while in case of LCoS one or more (RGB) LEDs must be constantly on, throwing light onto each pixel - even if this is supposed to be off and the liquid crystal is not set for reflecting.
Thus, OLED microdisplays offer today the highest possible integration level of all microdisplay architectures with the lowest power consumption possible. But due to their self-emitting architecture and the limited efficiency of the self-emitting materials they cannot provide the highest level of brightness as needed in the projector application or in Augmented Reality application. For these LCoS microdisplays are the better solution today. This may change, as soon as the efficiency of the OLED emitters will get a drastic improvement.
Through this high level of integration and through their very small dimensions microdisplays enable the development of new, very small and highly innovative devices and thus enabling the integration of image and video information in a series of existing and new applications, in which traditional display technologies for these reasons cannot be used.
For more detailed information about OLED technology or LCoS technology and for their advantages compared to other microdisplay technologies click on any of the links in the menu to the left or below.