Friday, May 27, 2016
Game Changer: CLEARink Shows Video-Rate Reflective Display
There are good very-low-power monochrome reflective displays with slow redraw times and, with the introduction of E Ink's color display, there is now a good low-power color reflective display with very slow redraw times.
What we have not had is a reflective video-rate display, and for good reasons. The only reflective technology that has proved to have both broad application and business feasibility has been electrophoretic (think E Ink), and electrophoretic displays operate by moving charged particles slowly through a significant fluid layer. The redraw time cannot be fast. (Well, it can be faster, but then the charged particles collide violently and tear each apart, with unfortunate results.)
CLEARink has turned the conventional electrophoretic model on its head. Very very briefly, the CLEARink display has a thin optical plate with lenslets on the inner surface. In the white state, incoming light experiences total internal reflection (TIR) and returns to the viewer. Reflectivity is an impressive 60%.
How does the display form a black pixel? Lurking behind the optical plate in an "ink" are black particles that are moved toward or away from the plate. When the particles touch the plate (that's a bit sloppy, but close enough for a blog), the TIR is defeated and light at that point is absorbed.
Clever, you say, but it's still electrophoresis, with a particle being moved through a fluid. How can that produce video rate? Because there's something I haven't mentioned yet. The particle only has to move through 0. 5 micron to be "touching" or "not touching" the plate, and that very small distance can be traversed rapidly.
All of this has been public for a least several weeks, but at Display Week, the company showed technology demonstrations in its suite. To demonstrate the monocrome video-rate display, CLEARink engineers had purchased a Kobo eReader, and simply replaced the E Ink imaging film with their own. With the application of a video signal, the display showed very clean, 30 fps video with the subjectively good contrast and that bright 60% reflectivity. CEO Frank Christiaens to the opportunity to note that the technology is compatible with pretty much any backplane and requires no precision alignment.
Although my colleague Bob Raikes and I were extremely impressed with this demo, Christiaens didn't want us to neglect that fact that color via matrix color filter is part of the company's mid-term road-map. Demos were effective. Using an MCF with an otherwise monochrome EPD has not been a satisfying approach in the past because too much of the reflective light was absorbed. The difference here is that CLEARink starts out with 60% reflectivity rather than 40%.
So, said Christiaens, CLEARink will soon be providing something that has never before been available: a reflective color video-rate display.
Walking back to the Moscone Center after our meeting, Raikes and I agreed that the term "game-changing" is used far too often, but that it legitimately applies here. This fast EPD can enable new applications that cannot be realized by existing display technologies. -- Ken Werner