Barry Blundell's "3D Displays and Spatial Interaction"

Exploring the Science, Art, Evolution and Use of 3D Technologies

“3D Displays and Spatial Interaction, Vol I” has now been made available for free download from Barry's website – www.barrygblundell.com The book can be downloaded in two parts, the first PDF file contains the Front Matter plus Chapters 1 through to 4, and the second file contains Chapters 5 through to 9, the Appendix, and an extensive reference list (comprising just over 700 references).

Here are some excerpts from the Forward, "The author needs little introduction; he is a highly-regarded historian of ‘the technology of images’, with a deep knowledge fuelled by his own groundbreaking work in volumetric 3-D display. I have learned a great deal in the pages of Barry’s writings since I entered the field of 3-D display in 1988.

This book is exciting for two reasons. First, you’ll learn - in a very clear, completely illustrated manner – about perception, interaction, and image display. For example, in perception, you’ll encounter the architecture of the eye, a deep catalogue of depth cues, and the visual cortex. You’ll learn about haptics and interaction, including the fundamental Fitts’ Law of visual and physical target acquisition. The book is rounded out (so to speak) with Barry’s excellent teachings on a complete variety of three-dimensional displays, spanning stereoscopic, lenticular, parallax barrier, and volumetric systems.

Second, I enjoy his writing because he magically expresses treasure-troves of deep historical and scientific knowledge underlying a variety of topics. Ever wonder not about who really invented the stereoscope, but what they argued over? What’s a horopter or how do you compute 3-D imagery? Never mind ‘what’s a volumetric display’, what might its embedded electronics look like?

I hope you’ll agree that a book of this sort has really been a long time coming. When I got a sneak preview, I certainly enjoyed page after page of history and science that was new to me, even after working in the display industry for 20 years.

Gregg Favalora
August 2010
Former CTO, Actuality Systems, Inc.
Principal, Optics for Hire.
Arlington, Mass.,USA"

An Apple Branded TV Set v. the iWatch

A former senior executive at Apple recently said that an iWatch is a lot more likely from Apple than the much rumored Apple branded TV set. The reason he gave was that a watch is a much more personal item than a TV and more fitting with Apple’s previous initiatives. I would agree but for different reasons. As I have noted elsewhere that while 4K TV will have limited utility in consumer TVs, it will be a great boon to digital signage as the intended range of viewing distances for signage includes distances where 4K resolution really does matter. Further, 4K may be one of the first of a continuing stream of innovations to find a home in digital signage first before migrating to the general consumer TV market.

Apple does what it does by adapting new technology and pioneering new usage models. Absent participation in the digital signage market, Apple might not be able to do this on an ongoing basis in TV. Apple’s failure to include NFC in the latest rev of the iPhone may be due, in part, to wanting to avoid connecting smartphone innovation to the digital signage market. With 4K, the linkage between TV and digital signage innovation is here now and likely to grow.

Glass and the Russian Meteor

.... the Russian meteor stole the show Friday, fireballing across the Ural Mountains in spectacular fashion and exploding into fragments, creating a powerful shock wave that blew out windows, collapsed roofs and injured 1,200 people, mostly from broken glass.

A thing to consider about glass is that because of it partly random, partly ordered structured it is not necessarily electrically balanced on a atom to atom scale as would be the case with a fully crystallized material. This is especially true of a newly created surface. There are few things on earth quite as sharp as a freshly (freshly on the scale of microseconds) broken piece of glass. This is why, especially in situations such as an earthquake, it is a good idea to stay away from windows. The flying glass from a newly fractured window can fly right through skin and bone. Over time (seconds, minutes and for as long as a week) the electrically unbalanced nature of the new surface or of a scratch in the glass, begins to "heal" as the molecules at the newly created surface re-arrange their linkages to lower the surface energy. This healing also means that any glass particles created in a fracture or scribing operation can adhere themselves to another glass surface and become bonded there. As you would expect, every discontinuity in the glass surface has the potential to be a stress concentrator.

In general, glass strengthening processes such as thermal or chemical tempering are less effective on edges than they are on the body of a flat glass sheet. Part of this is geometry, part of this is how the edge was formed, and part is timing between the cutting and the strengthening operation. Though you would tend to think of glass as a static material, it does have its dynamic aspects. As I noted in a previous post, ion migration under the electron beam of a CRT eventually destroys the transparency of CRT glass to blue light. A bad cut, even for glass that is subsequently strengthened, even for glass that seems OK, will leave a weakened part.

The mobile device market periodically goes through periods of high display breakage. New suppliers or new staff have to attune themselves to the idea that their cutting process needs to be well engineered and maintained. Just because the glass is not shattering in their process or even in their customers does not mean that they are turning out quality for the end consumer.

Glass v. Plastic Substrates

A short Primer on CRT Longevity
The picture tube in a television was originally one of the longer lived components in a TV set. As the supporting electronics moved from tubes to solid state devices, the life of the tube was extended so that, like many glass products, it functions until you get sick of it and throw it out. In the function of a CRT, an electron beam hits phosphors deposited on the inside of a glass bottle. In addition to exciting the phosphors, the electron beam can also drive off some of the more electronegative elements in the glass. First to go is, of course fluorine, a powerful phosphor poison. This is why it is important to have negligible amounts of fluorine in the glass as it is a phosphor poison. Next is oxygen.

In the tube making process, one of the last steps is “flashing the getter”, essentially coating the inside of the tube with barium metal. Barium being one of the least electronegative elements, any liberated oxygen latches on to the barium before it can do harm in other areas. “Gettering“ found a new use in telecom electronics which get buried in the ground and expected to last for at least 40 years.

For CRTs, after 15 to 20 years or so, another failure mechanism creeps in; the surface of the glass is so depleted in oxygen that a metal layer forms blocking the blue light. This was known as browning. One of the final requests of the tube industry was for the glass industry to fix the browning issue. However, rather than ensuring an ever longer lifetime for a bunch of tubes that were probably going to be disposed of around the HDTV transition, the industry was convinced that a better glass chemistry was one that aided recycling instead. Industry attention was focused on the glass as it had essentially fixed its phosphor life issues by going to higher and higher voltage phosphors. The bigger the band gap between the excited and resting state, the fewer the species that can insert themselves and deactivate the phosphor.

So, CRTs had a virtual hermetic seal being constructed inside a glass bottle that had a substantial vacuum. What atmosphere there was inside the tube was essentially reducing. There was no opportunity to oxidize, chlorinate, fluorinate, or hydrate any of the internal components. The glass also provided precise dimensional stability. As I note in an earlier post, the medical industry was building 12K CRTs on conventional TV glass. Monitor glass, which was made to a more precise spec, would have been capable of much more. And, the industry relied on a high voltage/long lived emission to generate light. All told you had a high resolution display that was capable of functioning for years, literally until the glass wore out from oxygen depletion.

LCD Longevity
In LCD technology, since their commercialization in the consumer TV market, the product has evolved so rapidly that there are not any 20 or 30 year old LCD TVs sitting in consumers living rooms. However the glass does provide the same hermaticity. Given the decay rate of the CCFLs (light output from the cold cathode fluorescent lamps declines 50% in about the first 2 years) used in the first models, likely the original LCDs will outlast their lamps by quite a bit and likely be replaced rather than repaired. The glass also provides precise dimensional control for the LCD photolithography. The original LCD glass, 7059, was a bit soft and frothy when it was made. It had to undergo a compaction step before being used as an LCD substrate as the high temperature operations would cause it to shrink. Since then, progressively harder glasses have been introduced and compaction is no longer necessary.

So as in a LCD, as in a CRT, the glass provides a flat surface for the photolithography, a stable surface for mulit-step processing, and a hermetic seal against the usual culprits in device decay the tree most electronegative elements (oxygen, fluorine, chlorine) and the most mobile electron donor (hydrogen).

Flexible Electronics with Glass
Currently there is much talk about flexible electronics. There are actually two distinct flavors of this, displays that are truly flexible and displays that are merely curved but fixed. Of the curved displays, making an LCD with a spherical profile is probably very easy. Making a cylindrical LCD could be doable as well but considerably more difficult. Making an aspheric would be much much harder and probably could never be justified. Making the substrate for any of these or for some type of new display would be the least of the problems to be solved.

As to making a flexible display, all glass forming imparts a compression layer on the surface. As a result, all glass is flexible to a degree depending mainly on its thickness. The expansion of the glass on the outer surface of a bend has to be less than the natural surface compression; once the surface of the glass comes under tension rather than compression, there is crack propagation. Consequently, not only is the flexibility limited to thin glass but it also only can happen in 2 dimensions, making cylindrical shapes. Flexing in 3 dimensions concentrates the outer surface tension into a single point/ Flat glass could be reformed (sagged) into a cylinder changing the range of radii it can accommodate but still only a small range of change in curvature can happen without breakage.

It is also important that the outer surface be pristine as well as any small, preexisting surface irregularities can rapidly grow into cracks. This is why Corning coats the edges of its flexible glass with polymer. Coating right on the glass draw, as is done with optical fiber, ensures that the surface never picks up any contact checks. Some years ago, I suggested that they do this with all of their fusion drawn glass to fix their then yield issue. The yield issue got fixed in other ways and the company lost interest. For a flexible display, it may be critical to coat the entire outer surface if glass is to be used.

Flexible Electronics with a Polymer Substrate
If plastic is to be used, then the potential breakage problem goes away but several new problems emerge. Polymers cannot stand nearly the temperature range that glass can. As a result flexible display development has focused on printing techniques rather than traditional high temperature photolithography operations. Polymers are also not as dimensionally stable as glass and printing is not as high resolution as photolithography. Although the limit will have to be explored, polymer substrate displays will not be as high resolution as displays on glass though they may be more than adequate. Finally, not only do polymer displays not offer the hermaticity of glass but polymer films frequently have mold release on them, and tramp, highly mobile, highly electronegative species within them (particularly residue from the polymerization initiators), and are permeable to small ion gasses such as hydrogen. Polymer displays cannot be expected to last nearly as long as ones built on glass but depending on the application, 3 years may be enough.

Conclusion
So, net/net, if you bend the glass in a tight enough radius it’s still going to break. Polymer displays will ultimately be less resolution and shorter lived than displays built on glass but few products need a 20 year life or 4K resolution. It remains to be seen how good printing resolutions, and ultimately printed display resolutions, can be taken.

Chemistry and the Apple TV

Such may not be the case today but formerly at MIT two terms of calculus, or the equivalent, was required for any degree, even what passes for liberal arts there. Engineers had to take a 3rd term. Chemical engineers and materials science folk took 18.03 “differential equations”, EEs took 18.031, also differential equations but with a greater emphasis on linear systems. The difference in the math embodied much of the difference between those branches of engineering, EE’s general deal with linear systems, chemistry is decidedly non-linear.

In practice, what this frequently means is that product development is very different for chemicals and materials than for electronics. In electronics, in linear systems, you can generally reduce the product risk and speed the time to market by testing the subsystems independently. In chemical systems even if different chemistries only touch each other rather than are mixed, the interface itself is a new system that must be tested and examined. Ions can migrate across boundaries or even re-arrange themselves within a monolithic material changing or defeating the product performance. In the display industry, when displays were actually made in the US, much of the industry was composed of chemical and materials folk. Today, as displays are all purchased from Asia, the domestic industry is largely EEs that design end product and develop display specifications.

Motorola spent close to a billion dollars building a fab and developing a process to make Field Emissions Displays (FEDs). In the end, they discovered tramp elements were migrating from their substrate into the FED structure. Using a different substrate, a different glass, meant starting over completely in process development. The investment was written off. A CRT glass plant once had to throw away several full days (the plant ran 24/7) of production during a product shortage due to parts per billion of fluorine in the glass. Fluorine outgasses from the glass in CRTs and is a powerful phosphor poison as is copper. Westinghouse, the inventor of the active matrix LCD, was put out of the TV business by a parts per billion copper problem in their plant water reclamation system. TV tubes would go dark about 6 months after consumers took them home.

Reportedly, Apple recently hired the OLED expert from LG prompting speculation that the much rumored Apple branded TV set will be an OLED. In the recent release of the iPhone 5 Apple had issues with the anodized aluminum coating on the case and with the sapphire lens cover. The lens cover was an optics issue but one that would have been expected if the company had truly comprehended the difference between a glass which it is familiar with and a transparent ceramic as is sapphire, fundamentally not the same thing. Two of the iPhone 5 product issues stemmed from predictable issues due to the nature of the materials they were using. Motorola's FED problem could have been anticipated as well. After Corning sold its consumer products business, the cookware industry is now rediscovering the difference between tempered flint glass and aluminum-borosilicate which was formerly synonymous with the term Pyrex.

OLED technology has had a long gestation period due to stability issues with the material. I would not expect Apple to venture so far into new materials technology. On a LinkedIn thread regarding LCD stability and suitability as outdoor digital signage, one of the posters commented that OLEDs might provide a better solution. If any stability issues remain with OLEDs, 24/7 operation and the heat and light of an outdoor installation will certainly bring those to light more so than use as a consumer TV. I would expect a proving period in TVs, as well as a cost reduction period, before OLEDs start finding their way into outdoor signage. I don’t expect that proving period to involve an Apple branded OLED TV. If Apple comes to market with a TV, I expect it to be an LCD, a very good LCD, but an LCD none-the-less. I also expect that the Apple magic will be in how its used rather than just a good looking screen. When Tim Cook said, “When I go into my living room and turn on the TV, I feel like I have gone backwards in time by 20 to 30 years", he wasn't referring to the picture quality.

The Other part of SpectraVue

As I mentioned in the original blog posting, there were actually two parts to the SpectraVue invention, The viewing film and the channel waveguide. Although the viewing film died a quick death after AlliedSignal folded the venture, the industry was mightily impressed with the channel waveguide and the design was widely adopted both in backlights for LCD as well as general lighting. The channel waveguide is something of the reverse of the viewing film, using a cons structure to columnate light rather than disperse it. The channel waveguide was rather problematic at the time as it did such a good job columnating light that you could see each individual channel element shining right through the display. The solution that was most obvious, giving the beams from each element some distance to integrate ran contrary to the trend of thinner displays. There was no appreciable LCD monitor business at the time; everything was notebooks. Finer structures and applications that could tolerate some thickness lead to a revival of the technique and AlliedSignal, after buying then changing its name to Honeywell, had a good time suing those that had adopted the idea.

Assuming the channel waveguide structure could be mad fine enough, there is an application for it on the front of some displays as well as in the backlight. If the optical pathway is run in reverse, you have a very efficient structure for capturing all off axis light and dumping it into the wavegude at sub TIR angles. This would give a display with extremely narrow viewing angle, virtually head on only, but the captured ambient light could be redirected to the LCDs own backlight or otherwise used to power the display.

A 12K Display

In other locations, I discuss some benefits of leaving out the color filter from LCD designs for signage: lower thermal radiation absorption, no cf fading, a brighter image. There is, of course a 4th benefit to removing the color filter in that you automatically get 3X more addressable pixels. That could give you a 3K display if applied to what would otherwise be an HDTV resolution screen or a 12K display if applied to the new 4K format.

Corning used to supply the glass for a 19” 12K monochrome CRT in the 1980’s. The customer used Corning’s standard 19” CRT glass to build the display although only about ½ of the glass supplied actually was within their spec. The 12K benchmark was important to the customer as it was a replacement for medical X-ray film. Because of liability concerns, the electronic replacement had to have at least the resolution of what it was replacing. I am unsure what X-ray film resolution is, but my understanding is that standard portrait film is the equivalent of 8K. With the transition to flat panel technology and the requirement of multi- billion dollar fabs, the opportunity to build such displays went away, replaced in part by the ability to pinch and zoom.

With the widespread availability of imagers well in excess of 12K, the market for 12K devices might extend well beyond the medical device market. Again, “digital signage “ is a possibility but there are a variety of other workstations where people look at images where 12K could be useful. … certainly defense as well. I would expect that whether they be field sequential color or monochrome, the product orders for 12K displays will start showing up.

Unbundling the Optical Stack for Better Environmental Performance

LCDs used outdoors as digital signage must be protected from the environment. Typically, they will have a cover glass to protect them from being poked and prodded. They may also have air-conditioning to protect the LCD from reaching its thermal clearing temperature or otherwise suffering thermal damage. Objects in direct sun can reach temperatures as much as 185⁰ F, and more than 70⁰ F above the ambient air temperature. The cover glass may be plate glass or chemically strengthened glass. Chemically strengthened glass has the advantage of being thinner and lighter. Plate glass has an advantage in that if it does fracture, it typically cracks rather than shattering, a feature known as "frangibility". This is especially true if a laminated solution is used. For public spaces, especially confined spaces such as in transportation applications, management of the broken glass hazard may be critical.

However, the cover glass may also be part of the thermal solution. The polarizers of an LCD, by definition, absorb about 50% of the light that hits them. They are agnostic as to which direction the light comes from absorbing 50% of inbound sunlight as well. Removing the outer polarizer from the LCD and laminating it between the layers of the cover glass puts a few millimeters of glass and an air gap between the absorbed thermal energy and the liquid crystal. This would cut the solar radiation load on the LCD by 50% and also provide the opportunity for passive, chimney, cooling rather than a powered air conditioner. Here, I discus removing the color filter as well. In addition to the brightness benefit, removing the color filter would have some solar radiation benefits as well. Certainly it will obviate any issues with solarization or fading of the color filter.

SpectraVue for Outdoor Signage

When LCDs had terrible viewing angle, many solutions were being developed to fix the issue prescriptively. Of course, the best solution is most always fixing the issue rather than applying a bandaid which is why most of these external fixes were dropped. One of these external fixes was a product called SpectraVue. It consisted of two components, and channel waveguide and a viewing film. The viewing film was an array of cones embedded in a black matrix. Light from the LCD entered the array columnated, bounced off the side of the cones a few times and left the viewing film very dispersed. The film produced an LCD appearance that was virtually the same as a CRT. It was described by Toshiba Labs as "Virtually Perfect viewing angle". Although I have seen several startups and other corporate projects where the intended function of the device depended on building a light funnel, basic geometry shows that funnel structures have exactly the opposite effect on bosons as they do on physical matter. Spectravue takes advantage of this effect to essentially provide something of a photon diode.

Although it was a great solution to the LCD viewing angle problem, it had two problems of its own. The first is that the maker, AlliedSignal, had problems actually manufacturing the product. The second, and more compelling issue was that it was a cost adder. It was being developed at the same time as IPS technology which fixed the problem in the LCD with no additional layers or costs.

Examining the diagram, there is another advantage that SpectraVue had, though it did not count for much at the time. The surface is virtually all blackfill. It adds inherently better sunlight viewability withoug significant loss of display aperture. As IPS development was the reconsideration of an old solution, as I note in my previous post, reconsidering the LCD optical stack might be in order for the digital signage market.

Re-Thinking LCD Architecture for the Digital Signage Market

The original intent of the LCD developers was a hang on the wall Television. However, it was not until 2004 that that really happened, at least for LCD technology. Several things had to happen first. From its emergence as a viable commercial product, color performance had to be accomplished and improved, viewing angle issues needed to be fixed, it had to be cost reduced to affordable levels at 32” and above. All of this was done by about 2004. Shortly thereafter, the use of CRTs in public information displays started to disappear and we had the development of the “digital signage” concept. Previous use of CRTs as public information displays inevitably used “off the rack” consumer product as neither the display makers nor the electronics companies paid much attention to the use of their product as public displays.

Since digital signage has become a recognized market, the differences in product requirements between that and a consumer TV have become more recognized. Although most differences between the two are complimentary: e.g. thinner bezels are beneficial to both consumer TV and digital signage but count for a lot more in the signage market. In some cases, however, the differences between the two are not complimentary and signage needs a solution that would be contrary to product design for a TV. One example is viewing angle. LCD TVs today have great viewing angle: left, right, up and down. In the signage market you probably don’t want that. For overhead signage, photons directed up are completely wasted. Even for eye level signage, the up/down distribution of light would be beneficially focused left to right. For outdoor signage, in areas where there are restrictions in showing video content (especially by roadways) a narrow viewing cone might be called for.

With respect to color, color has always been a tradeoff between saturation and brightness. For outdoor applications, it may be that the loss in brightness is accepted to generate over-saturated colors knowing that they will tend to be washed out in the daylight. Alternatively, a solution could be to go with a black and white, reflective or transflective LCD and do without color. For those displays using a linear polarizer, signage, is most often in portrait orientation, the polarizer should be reoriented for those consumers that might be wearing polarized sunglasses. Finally, as signage displays will face environmental challenges that TVs generally don’t, changing the way the LCD optical stack is put together can have some significant environmental benefits.

Bunny Burgers: Is it Mkt Research or PR

The dearly departed “Spy” magazine did a story where they spoofed several large PR firms regarding a fictitious new chain of fast food restaurants called “Bunny Burgers.” The idea behind the chain was that these QSRs would stock live bunnies, cute ones, and grind them up on the spot to give their customers the absolute freshest meat in their hamburgers. Spy festooned this idea with a fake client with lots of fake money and rented a suite in the Ritz Carlton overlooking Central Park and invited 9 PR firms to bid. Of the 9 PR firms contacted, all 9 were interested in Bunny Burgers as a client and 3 of the 9 were asked to come to the Ritz to discuss the matter. Of the three, none were prepared to turn down the business although one responded seemed diffident about the idea. The other two were quite enthusiastic about it, one even noting how much the public in California would love this idea. The magazine noted, “… as a general philosophical defense of her and her peers, it is important to remember that by the very nature of their profession, they [PR people] are constantly required to represent clients seeking to market stupid, tasteless and even immoral products.”

In a follow up to the PR firm interviews, Spy hired Mark Penn, yes that Mark Penn, to conduct a focus group on the topic. Per Pen’s observations, "Even though we got people to take the first bite, they really wouldn't take a second or third… Scientifically, we tried the concept on them, we tried the reality on them, and most people didn't like either. As well as we could package it, as well as we could add sauce to it, they just didn't like it…. Clearly, if someone tried to go forward with Bunny Burgers, they would have picketers, protesters, riot outside the Bunny Burgers stands, and so the product couldn't make it."

Spy’s conclusion, “For our investigation of the world of fast-food marketing, we discovered a yawning chasm between the enthusiasm of our PR professionals and the outright, unapologetic disgust of the dining public.” Having been around long enough to see several new prospects of the “Technology of the Future” come and go, having seen these technologies of the future accompanied by market forecasts of how this new thing is going to go off like a rocket, I often think to myself, “Bunny Burgers”.

The full Spy article may be found here.

Smellivision

In April 2011, I published an article in High Resolution entitled "Smellivision vs. OTT". The article concludes, "In general, with so many new, excellent devices for viewing video, the living room TV sets would benefit from expanding on what cannot be done in a mobile setting, raising the bar for the viewing experience, providing a more engrossing experience. That already happens with the better sound that is available. Development of other features, possible smell, most certainly wider aspect ratios, would be of benefit as well. With Best Buy’s decision to expand their mobile device stores and downsize some of their main store square footage, it seems that the mobile device is on the rise at the expense of the conventional TV. While 3DTV is the current excitement and 3D can be a differentiator between fixed and mobile viewing, I feel that something else would be beneficial." The full article is available from Veritas et Visus. What I said about 3D goes double for 4K.

After I wrote the article, I saw some reports of researchers in Korea working on a Smellivision product. Now HP and Intel are doing likewise but for the digital signage market. Actually, as with other technologies, having a revenue stream behind it might mean that this technology as well gets pioneered in digital signage before finding its way into consumer TV. 4K makes more sense for signage than as a consumer product. No doubt other technologies will follow this path as well.