Switchable Lenses and Polarizers Grab Attention at SID
I’m attending and reporting from SID’s DisplayWeek confab in Los Angeles this week. What I have seen so far is a lot of interest in LCD technology that can create switchable lenses or can rotate polarization. The first is of interest to autostereoscopic display developers, while the latter is of interest to display makers who offer passive-polarized 3D glasses-based solutions.
One of the more common approaches to making an eyewear-free 3D display is to use a lenticular sheet. This is a plastic sheet that consists of long cylindrical lenses that are aligned diagonally to the LCD imaging panel. This helps direct views to the eyes in 3D mode, but it can distort the image if you want to use the panel for 2D content.
To address this, researchers are developing liquid crystal device structures that can create a lens in one state that is optically transparent in the other state. This allows the lenses to be turned on or off, thus increasing the utility of the panel. An undistorted 2D image is certainly a requirement for an autostereoscopic 3DTV solution, with switching lenses being one way to get there.
The first products based on switchable lenticular arrays are coming this year, most notably a laptop from Toshiba. I don’t know if this is on exhibit at SID yet (I will find out), but there were a number of interesting papers given by researchers from the U.S. and Taiwan.
For example, researchers from Kent State University described a project that created a LC lens with a tunable focus. The use of diffractive and refractive designs was explored and explained.
The University of Central Florida is quite active with several projects including a design that electronically moves the switchable lens laterally as well as a new design for a switchable lens using Blue-Phase liquid crystal. You will be hearing more about Blue-Phase LCs because they have the capability for very fast switching, potentially allowing field sequential LCDs. That means panel makers can triple resolution (no spatial color filter matrix) and reduce costs. The University is very active in this area and commercialization of products now seems 2-3 years off.
National Chiao Tung University in Taiwan is also quite active and showcased several design options.
Polarization switching is the other big theme. The concept was highlighted two years ago at SID by LG Display who calls the process Active Retarder. They presented a paper on this again this year, but it would seem most of their efforts at this time are focused on Film Patterned Retarder (FPR) rather than Active Retarder. The key advantage of the Active Retarder approach is that it allows the delivery of full resolution images to each eye and the use of passive polarized glasses, without vertical viewing angle restrictions (FPR offers half resolution per eye with some vertical viewing angle restrictions).
But two other groups are taking up the charge. One is RealD and Samsung LCD, which showed their Active Shutter version of the technology at SID. We saw their demos in a private suite at CES and we were quite impressed. I have not yet had a chance to see it on the show floor at SID.
The other group is being led by LC Tech that has developed a very fast (400Hz switching) double LCD cell approach. This has been commercialized as a polarization switcher by Lightspeed Design for Cinema and ProAV applications. LC Tech is now working with Seiko Epson to adapt the technology to LCD panels.
These polarization switching panels are fairly simple devices. Both LGD and RealD use a scanning approach (RealD uses 8 bands that switch in synchrony with the row scanning), while LC Tech uses a single cell.
The big question for commercialization for flat panels is the cost of this additional LCD element. Clearly, current TFT LCD fabs are way too costly to make this component, so these parties are trying to understand the manufacturing options and fab investment costs to determine if and when commercial products will come. Samsung and RealD seem comfortable enough with the solution to have announced availability of 23-inch and 27-inch monitor products by the end of 2012, but did not say when up to 55" TVs would come to market. Essentially, the industry will need a Gen 8 to Gen 11 fab for TN/STN panels for these polarization switchers, if cost-effective LCD TVs are to come to market.
By Chris Chinnock, Display Daily
