As covered in detail in parts 1 and 2, for years LCD companies have claimed that their sets can be viewed all the way to 170+ degrees. That number would be like viewing the panel all the way to the side, almost parallel to the edge of the TV frame. Have you actually tried to do that with your set? Do you still see the same image quality if any image at all? Is the image still appealing to you, or you rather move back to the center? Try moving gradually from the center passing the 20 degrees angle to the left or right and keep increasing the angle (20 degrees is about what your companion viewer may be seeing if sitting right by your side). This report (Viewing Angles section) covers more detail about the subject.
Companies like Panasonic, Sharp and others have implemented new technologies that claim view-angle improvement on their sets, but one company have created a product that could be used by all manufacturers that would like to adopt it, that company is 3M.
How this technology can be applied to the type of LCD/LED you like?
As mentioned in part 2, the 3M product adds two components to the typical light source and LCD panel components.
Light Distribution Films. This box can represent the various combinations of diffuser, prism, and microlens films that are used to shape and make uniform the output of the light source. The output from the Light Distribution Films is spatially uniform, and it is typically collimated to some degree, meaning the light is contained within a cone. The shape or size of the cone is entirely defined by the combination of Light Distribution Films.
Reflective Polarizer. This box can represent 3M's DBEF and APF families of products. I am trying to represent several things with this film. First, some of the light from the Light Distribution Films is transmitted directly through the Reflective Polarizer (blue arrows). These blue arrows are within the same cone as that which comes from the Light Distribution Films. Second, some light of the wrong polarization is reflected by the Reflective Polarizer and interacts with one or more of the Light Distribution Films before being reflect back toward the Reflective Polarizer (thick green arrows). This is the light that has a chance to emerge from the Reflective Polarizer at broader angles than the cone defined by the Light Distribution Films. Third, there is a portion of light reflected by the Reflective Polarizer which makes it all the way back to the light source before being reflected back toward the panel (thick red arrows). This light emerges from the reflective polarizer within the cone defined by Light Distribution Films.
Based on the description Dr. David Lamb detailed in Part 2 of this series and excerpted above I asked him the following questions (in bold), and his responses are below (in italic):
1) Although you specified that the light source of your example could be LED arrays (local dimming) or edge-lit source, it appears to me that there may be a difference/preference in the results when you apply your product, expecting an increase of light even on local dimming designs. I am not sure your graph was already representing local dimming, and perhaps top/edge light LCD design should show a graph with less light reaching the distributor layer.
Even if more light can be obtained from the light source layer, local dimming typically helps in accurately directing the light to small areas of the image while keeping surrounding areas dark if the content is such, increasing contrast ratio (CR). Wouldn't your distributor/polarizer be counteracting with the needed directionality of a local dimming design and actually reduce CR? If so, would your product fit better for top/edge lit designs? And should rather not be used with local dimming designs because it may reduce CR?
Our products work similarly in all types of panels, whether edge-lit or direct lit. You make a good point about local dimming and dynamic contrast. We have not quantified a reduction in contrast for locally dimmed sets, but I would expect it to be a second order effect. From a market acceptance standpoint, our products are used in the highest end locally dimmed LCDs on the market, so any reduction in contrast is at least accepted by our customers and all major brands and panel manufacturers use our films in some portion of their product portfolios.
We simply have not quantified what I would call "cross-talk effects" in locally-dimmed sets. Given that our products are used in TVs which are locally-dimmed, I think that the cross-talk effects (which I acknowledge will be real) either is not large enough to be noticed or that manufacturers using our film can design the local dimming algorithm to minimize the effects of cross talk. I have never been asked about this by our customers, but I agree that it is an interesting subject.
2) Other than showing non-uniformity, what is the reason your graph shows a perfect 90 degree angle in one side of the light but a spread of light on the other side? In theory if using local dimming the light output should be spread evenly 180 degrees on each LED, and your distributor/polarizer would amplify the effect on the final image.
The cartoon that I drew was supposed to be representative of many different types of lighting. What I have shown is more consistent with what is seen in edge lit displays. You are correct: In direct-lit displays, the output from the light source is angularly much more uniform (though not spatially). Please be careful in drawing too many conclusions about specific ray paths in my cartoon.
3) What is the estimated light reduction of having two extra layers (distribution and polarizer) vs. the gaining of light output they provide? for example: 60% light gaining due to the technology spreading light, minus 20% light blocking due to the two extra layers (green and red arrows) would net a 40% light increase? (of course in addition to the benefit of spreading the light evenly) Do you have such numbers?
There is not a big optical penalty for having additional layers in the backlight. The layers have very little absorption -- otherwise the performance would suffer tremendously.
4) When I casually saw the demo the panel appeared to maintain color/contrast/brightness uniformity at least up to 60% view-angle (120 degrees L-to-R), not to the level of plasma but quite an improvement compared to the typical 15% of many LCDs before they start to drop image quality. Although 3M may not want to publish a number in angle improvement due to legal considerations, would my gross estimate of 60% be consistent with your lab tests?
I think your assessment of our demo and the viewing angle benefit is fair.
5) How much more would a $500 LCD panel would cost if using this technology? Would the technology be so costly to be non-attractive until a panel price hits $1000 or so? (You fill the blank). Would the technology cost more as panel size increases? Not recommended for small panels?
The price of our products is, of course, based on volume, so it's difficult to give you exact details. Also, the application of our film enables the removal of other components from the system (such as light sources), so it is possible (in some cases) for our film to reduce the overall system cost. On an order of magnitude, though, our solution costs $10 (not $1 and not $100). Anecdotally, we can find TVs in the market with our film that has a lower selling price than similarly-featured TVs without our film. Because we are so far back in the supply chain, we don't think our film significantly affects the final price of the TV to consumers.
With "enables the removal of other components from the system (such as light sources)," I meant additional light sources. This is true as long as the design is not uniformity-limited. In cases where uniformity limits the number of light sources, the addition of our films can still result in savings. For a fixed number of LEDs, adding our film enables those LEDs to be run at a lower power to achieve the same brightness. This reduces requirements for the electrical power supply and can result in a cost reduction somewhere else in the system.
This is the last part of this LCD article series about angle of view, and I hope the reader found it useful. LCD is also known to be subjected to blurriness because of the sample-and-hold mode of operation and this article covers the subject.
I thank again Dr. David Lamb of 3M for his participation in this article.
Posted by Rodolfo La Maestra, June 11, 2012 7:55 AM
About Rodolfo La Maestra
Rodolfo La Maestra is the Senior Technical Director of UHDTV Magazine and HDTV Magazine and participated in the HDTV vision since the late 1980's. In the late 1990's, he began tracking and reviewing HDTV consumer equipment, and authored the annual HDTV Technology Review report, tutorials, and educative articles for HDTV Magazine, DVDetc and HDTVetc magazines, Veritas et Visus Newsletter, Display Search, and served as technical consultant/editor for the "Reference Guide" and the "HDTV Glossary of Terms" for HDTVetc and HDTV Magazines. In 2004, he began recording a weekly HDTV technology program for MD Cable television, which by 2006 reached the rating of second most viewed.
Rodolfo's background encompasses Electronic Engineering, Computer Science, and Audio and Video Electronics, with over 4,700 hours of professional training, a BS in Computer and Information Systems, and thirty+ professional and post-graduate certifications, some from MIT, American, and George Washington Universities. Rodolfo was also Computer Science professor in five institutions between 1966-1973 in Argentina, regarding IBM, Burroughs, and Honeywell mainframe computers. After 38 years of computer systems career, Rodolfo retired in 2003 as Chief of Systems Development from the Inter-American Development Bank directing sixty+ software-development computer professionals, supporting member countries in north/central/south America.