page_title: OLPC XO
section_title: Display
hierarchical_section_title: OLPC XO / Hardware / Display
caption_attribution_description: 1 square millimeter (1×1mm) of two laptop screens, displaying plain white, to show the subpixel arrangement: OLPC XO-1 screen (XO-1 Test-B2 pre-release model) (left image) a "typical" laptop monitor: Lenovo X61: 12" diagonal, 1024×768 pixels [0.2381 dot pitch (mm); 106.67 PPI] Both images were photographed with the displays at maximum brightness, under identical conditions, and have been (minimally) processed identically.
context_page_description: The OLPC XO, previously known as the $100 Laptop, Children's Machine, and 2B1, is an inexpensive laptop computer intended to be distributed to children in developing countries around the world, to provide them with access to knowledge, and opportunities to "explore, experiment and express themselves". The XO was developed by Nicholas Negroponte, a co-founder of MIT's Media Lab, and designed by Yves Behar's Fuseproject company. The laptop is manufactured by Quanta Computer and developed by One Laptop per Child, a non-profit 501 organization.
  The subnotebooks are designed for sale to government-education systems which then give each primary school child their own laptop. Pricing was set to start at $188 in 2006, with a stated goal to reach the $100 mark in 2008 and the 50-dollar mark by 2010. When offered for sale in the Give One Get One campaigns of Q4 2006 and Q4 2007, the laptop was sold at $199.
  The rugged, low-power computers used flash memory instead of a hard disk drive, and came with an operating system derived from Fedora Linux as their pre-installed operating system with the Sugar GUI.
context_section_description: 1200×900 7.5 inch (19 cm) diagonal transflective LCD (200 dpi) that uses 0.1 to 1.0 W depending on mode. The two modes are:
  Reflective (backlight off) monochrome mode for low-power use in sunlight. This mode provides very sharp images for high-quality text
  Backlit color mode, with an alternance of red, green and blue pixels
  XO 1.75 developmental version for XO-3 has an optional touch screen
  The first-generation OLPC laptops have a novel low-cost LCD. Later generations of the OLPC laptop are expected to use low-cost, low-power and high-resolution color displays with an appearance similar to electronic paper.
  The display is the most expensive component in most laptops. In April 2005, Negroponte hired Mary Lou Jepsen—who was interviewing to join the Media Arts and Sciences faculty at the MIT Media Lab in September 2008—as OLPC Chief Technology Officer. Jepsen developed a new display for the first-generation OLPC laptop, inspired by the design of small LCDs used in portable DVD players, which she estimated would cost about $35. In the OLPC XO-1, the screen is estimated to be the second most expensive component (after the CPU and chipset).
  Jepsen has described the removal of the filters that color the RGB subpixels as the critical design innovation in the new LCD. Instead of using subtractive color filters, the display uses a plastic diffraction grating and lenses on the rear of the LCD to illuminate each pixel. This grating pattern is stamped using the same technology used to make DVDs. The grating splits the light from the white backlight into a spectrum. The red, green and blue components are diffracted into the correct positions to illuminate the corresponding pixel with R, G or B. This innovation results in a much brighter display for a given amount of backlight illumination: while the color filters in a regular display typically absorb 85% of the light that hits them, this display absorbs little of that light. Most LCD screens at the time used cold cathode fluorescent lamp backlights which were fragile, difficult or impossible to repair, required a high voltage power supply, were relatively power-hungry, and accounted for 50% of the screens' cost (sometimes 60%). The LED backlight in the XO-1 is easily replaceable, rugged, and inexpensive.
  The remainder of the LCD uses existing display technology and can be made using existing manufacturing equipment. Even the masks can be made using combinations of existing materials and processes.
  When lit primarily from the rear with the white LED backlight, the display shows a color image composed of both RGB and grayscale information. When lit primarily from the front by ambient light, for example from the sun, the display shows a monochromatic (black and white) image composed of just the grayscale information.
  "Mode" change occurs by varying the relative amounts backlight and ambient light. With more backlight, a higher chrominance is available and a color image display is seen. As ambient light levels, such as sunlight, exceed the backlight, a grayscale display is seen; this can be useful when reading e-books for an extended time in bright light such as sunlight. The backlight brightness can also be adjusted to vary the level of color seen in the display and to conserve battery power.
  In color mode (when lit primarily from the rear), the display does not use the common RGB pixel geometry for liquid crystal computer displays, in which each pixel contains three tall thin rectangles of the primary colors. Instead, the XO-1 display provides one color for each pixel. The colors align along diagonals that run from upper-right to lower left (see diagram on the right). To reduce the color artifacts caused by this pixel geometry, the color component of the image is blurred by the display controller as the image is sent to the screen. Despite the color blurring, the display still has high resolution for its physical size; normal displays as of February 2007 put about 588(H)×441(V) to 882(H)×662(V) pixels in this amount of physical area and support subpixel rendering for slightly higher per
caption: Comparison of the XO-1 display (left) with a typical liquid crystal display (LCD). The images show 1×1 mm of each screen. A typical LCD addresses groups of 3 locations as pixels. The OLPC XO LCD addresses each location as a separate pixel
exif: {}