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.