An introduction to OLED
Ron Mertens | Technology | Published Feb 6, 2012
OLED screens are becoming increasingly common on enthusiast cameras. So, what’s all the fuss, and why should you care about the technology behind your camera’s screen?
During the world's largest electronics show, CES 2012, OLED was the most talked about technology. You have probably heard about OLEDs – flexible transparent displays that can provide brilliant colors and be power efficient. In this article I'll provide a short introduction to OLED technology and explain how it will affect you as a photographer.
|OLED screens and microdisplays are appearing in an increasing number of higher-end cameras, such as the Samsung NX200.|
OLEDs (or Organic Light Emitting Diodes) are thin, light-emitting devices, made by placing a series of organic thin films between two conductors. When electrical current is applied, a bright light is emitted. OLED are thin, efficient and bright – and can be used to make displays and white lighting panels.
Unlike LCD displays, OLEDs do not require a backlight. In an OLED display each ‘pixel’ is a small light emitting diode (or, more commonly, three: red, blue and green). This means that the basic structure of an OLED is simple (no need for backlighting, filters and polarizers) and so OLEDs are ultra-thin and lightweight.
The biggest advantages of OLED displays are the things that photographers are most likely to appreciate. Firstly, the color gamut is wider than that of an LCD display, allowing more accurate reproduction of the colors of your images. Secondly, thanks to the totally unlit black pixels, the contrast is really high, allowing a more realistic impression of how your images will look. OLED displays have greater viewing angles, allowing more flexible use of the camera, both for shooting and reviewing images, or showing them to others.
Perhaps the feature that makes OLED most attractive for use in photography is its speed. With refresh rates about 1,000 times quicker than an LCD, it can be used to represent the increasingly fast live view output from the latest cameras with ever improving realism. This is particularly important where the technology is being used for electronic viewfinders, and a rapidly updating, smooth representation of movement can help re-create the optical viewfinder experience.
OLEDs are considered very power efficient, but it is important to understand that this depends on the image shown. Each pixel is lit independently and so a black pixel does not draw power at all. When designing a user interface for an OLED display, it is better to use white text on a black background for example (when Microsoft designed the Windows Mobile 7 interface, they indeed assumed that most phones will use OLED displays and this effected their choices). The nature of photography, where the amount of black in the image varies massively, means this benefit is rather reduced, outside of menu use.
Challenges for OLED
Historically OLEDs had three disadvantages: lifetime, sunlight readability and price. It is true that OLED brightness decreases over time and the panel’s lifetime is limited, but in the past few years we've seen steady improvement in OLED device lifetime, to the point now that this is no longer a real issue (some OLED materials can last for over a million hours before degrading to half their original brightness).
In the first generation OLED panels visibility under sunlight was poor indeed (mostly because of light reflection from the metal cathode used in OLEDs). In touch panels the problem was even worse. But since then the technology advanced and the panels are brighter and behave better in such conditions. For touch displays, Samsung developed the Super AMOLED technology which embeds the touch sensor into the OLED panel. Super AMOLEDs are pretty much equivalent to a touch enabled LCD and some consider these displays to be the best mobile touch displays available today.
|Large OLED TVs are coming soon, initially at a high price. Karl Guttag|
OLEDs are indeed more expensive than LCDs – about 20% more for a small sized display, although the gap is closing quickly. Some say that eventually OLEDs will be cheaper than LCDs, especially if/when manufacturers are able to adopt a printing process. Making large sized OLED is still very costly – mostly because current OLED fabs are small, and scaling the manufacturing process is not easy. It is expected that the 55” OLED TVs unveiled at CES 2012 by Samsung and LG will cost around $8,000.
The OLED market was estimated at about $3.3 billion in 2011 (having more than doubled from about $1.25 billion in 2010). Most display makers have active OLED programs, and Samsung's investment in OLED displays alone is estimated to be around $4.3 billion in 2011 and in excess of $6 billion in 2012.
OLEDs for cameras
OLEDs have been used for camera displays since 2003 – in fact the first gadget to sport an AMOLED display was a camera: Kodak’s LS633 (though that camera was never mass produced). Today you can find OLED-equipped cameras from some of the biggest names in the industry including Sony, Nikon, Olympus and Samsung.
|The Olympus E-P3 features an OLED screen|
Cameras with OLED screens include:
- Olympus XZ-1 and E-P3
- Sony TX200V
- Samsung WB850F and WB150F
- Samsung NX200
- Nikon S100
Direct emission and microdisplays
Although I said earlier that, in OLED displays, each pixel is made from RGB sub-pixels, this is a direct-emission architecture isn't the only possibility. Some companies are actually using white OLED subpixels behind a color filters layer. While this design is less efficient, it is also easier and cheaper to make. It’s also easier to make very small, and most OLED microdisplay products sport this architecture.
|Sony's OLED microdisplays are the highest resolution electronic viewfinders currently in use but French company MicroOLED hopes to use the even finer resolution models it has just unveiled.|
OLED microdisplays are starting to be used as electronic viewfinders, with Sony being the clear OLED EVF pioneer, In August 2011 they unveiled four cameras that use an XGA OLED microdisplay (which are made by Sony themselves): the A77 and A65 SLRs and the NEX-7 and NEX-5N mirrorless interchangeable-lens cameras.
|The development of a high-resolution OLED display was a key step in Sony moving over to an electronic viewfinder design for its top-of-the-range A77.|
Reviews of this Sony EVF have been very favorable, as the OLED microdisplay offers better color, refresh rate and brightness compared to an LCD viewfinder (they should be more efficient, too). OLED EVFs are likely to be especially important for the development of mirrorless cameras – as some consider the lack of an optical viewfinder to be the biggest drawback of these cameras. OLED EVFs are starting to close that gap.
Flexible and transparent OLEDs
|Transparent OLED displays could find use in conjunction with optical viewfinder designs. Philips Lumiblade|
It is actually possible to create flexible OLEDs, and transparent ones, too. Prototypes have been shown for years, but now it seems that the technology is actually coming to the market. TDK/Futaba are already producing small transparent PMOLED panels (used in Lenovo’s S-800 phone), and Samsung promises to start offering flexible panels in 2012.
|Flexible OLEDs give more freedom to camera designers. OSRAM|
The first products probably won't themselves be bendable but the technology will make it possible to place them on a curved surface. In the same way that fast readout sensors allowed the creation of mirrorless cameras, the advent of flexible OLED technology potentially allows camera designers to step further away from the traditional idea of what shape a camera has to be.
Ron Mertens is OLED-Info’s editor-in-chief and an amateur travel photographer (with a Nikon D90 and an Olympus XZ-1). OLED-Info is the web's leading OLED portal since 2004, providing daily news and resources. OLED-Info also maintains a complete list of cameras that sport OLED displays. OLED-Info is also the publisher of The OLED Handbook, a comprehensive guide to OLED technology, industry and market.