Mirasol Display

Qualcomm engineers have developed MEMS (Micro Electro Mechanical System) based Mirasol display. It mimics the way butterfly or peacock feathers produce brilliant, iridescent and shimmering colours. Light reflected from an image, for instance paper is more appealing to human eye than the backlit displays [1]. Due to the use of light reflection, mirasol display's readability does not diminish even in the presence of direct sunlight. A report from Pike research [2] states that mirasol is more energy efficient than other display device technologies. Mirasol displays are capable of displaying video. The only hiccup is cost. Let us hope it will come down in future. I was introduced to mirasol display by an article published in MIT's Technology Review magazine [7].

Microprocessors, memory chips diligently follow Moore’s law, so in short duration we get phenomenal capacity improvement. In the case of display system, improvement is in snail's pace [4]. Matured technologies like Liquid Crystal Displays (LCD) and Light Emitting Diodes (LED) are lit from back. The display market is dominated by back lit (60%) and transflective (40%) type LCDs. Combination of back lit and reflective technology is called transflective. The remaining displays use OLED and they constitute 5 percentage of entire display market [5].  Above discussed technologies consumes more energy than the reflective type. E-ink's Triton is another reflective display technology that rivals mirasol [3] with good colour capability. Earlier e-ink based ereaders like Kindles and Nooks were limited to black and white only.

Interferometric Modulator (IMOD) is the building block of mirasol display. IMOD is made up of top thin-film and height adjustable (deformable) reflective membrane supported by a transparent substrate. Incident light is reflected from thin-film and as well as from reflective layer. Depending upon the height (i.e. distance between thin film and reflective membrane) constructive interference and destructive interference occurs. So few colors are amplified and others are diminished due to destructive interference. For example, if red colour gets constructive interference then that spot will appear as red. This arrangement can be thought of a optical resonator. IMOD can take only two states or positions.Height can be adjusted(either minimum level or maximum level) by applying voltage between the reflective layers. When all RGB subpixels are in minimal position then ultra-violet ray only will be reflected and other colours are lost in interference. As humans cannot perceive ultra-violet, it appear as a black dot for them. The deformation required will be in the range of few hundred nanometers and time taken will be in the range of microsecond. Due to this only displaying a video is perfectly possible.

A typical mirasol display will be 5.3" (measuring the diagonal of the screen) with 800x480 with 223 pixels per inch. With same dimension but with XGA resolution screens are also available in the market.  But the cost is not pocket friendly. Following products use mirasol displays: Kyobo ereader, Hanvon C18, Bambook Sunflower, Koobe Jin Yong reader, and Bichrome displays. In one blog it was mentioned Kyobo ereader has stopped using mirasol. One has to check its veracity.

Environment friendliness of the product is not measured by usage power consumption alone. The entire lifecycle of the product starting from mining the ore for minerals, manufacturing, assembly, packaging, shipping and ending with disposal, amount of energy used is monitored and noted. In usage and life cycle analysis IMOD based mirasol displays outperform conventional LCDs and LEDs [5]. It is estimated that there are four billion mobiles devices in the year 2008, with LCD and OLED displays. If all of them switched to IMOD display then 2.4 Terawatt-hour of power can be conserved per year. It also noted only 10% of light generated reaches the human eye in LCD and remaining is absorbed by components present in the system itself.

Source:

1.  Mirasol display, http://www.mirasoldisplays.com
2.  Pike Research, http://www.pikeresearch.com 
3. Qualcomm's Mirasol Display Could Mean New Color Nooks and Kindles, by Sascha Segan, http://www.pcmag.com/article2/0,2817,2400889,00.asp
4. Mirasol Display Technology Could Be the Screens of the Future, http://www.tomshardware.com/news/mirasol-mems-e-ink-display-screens,14867.html
5.  Energy Efficient Displays for Mobile Devices, Published 4Q 2009, (Pike Research - Energy Efficient Displays_Final.pdf) http://www.mirasoldisplays.com/sites/default/files/resources/doc/Pike%20Research%20-%20Energy%20Efficient%20Displays_Final.pdf
6. (Picture Courtesy) Qualcomm Mirasol display for color e-readers inspired by butterflies http://www.robaid.com/bionics/qualcomm-mirasol-display-for-color-e-readers-inspired-by-butterflies.htm 
7. MIT Technology Review magazine, http://www.technologyreview.com/magazine/