Aris Silzars Display Technology Consulting

DISPLAY CONSULTING

 

Now, it looks so much easier…

It has taken us over forty years to achieve dominance with flat-panel display technologies.  Along the way, there were serious doubts that we would ever get there.  Only a relatively few years ago, the conventional wisdom within the display community was that LC displays would only be able to be made in sizes up to about 20 inches and that the larger size television displays would have to be either plasma panels or rear projection systems.   How wrong that turned out to be. 

Both LC and Plasma displays are now available at affordable prices in sizes up to 60 inches -- with a few even larger.  Given the many years of struggles to get us to this level of capability, it’s especially interesting to take a look at what we now have and how much effort it took to get here.

Let’s take a look at a few of these larger flat-panel televisions.  Should we start by taking the back cover off and see what we find?  On either a plasma panel or LCD television, the opened chassis greets us with a very logical circuit board layout.  There is, of course, a readily identifiable power supply.  Then we see the various video inputs – way too many in my opinion, but that’s more a reflection on the difficulty of establishing any kind of industry standards than on any lack of skill on the part of the design engineers.  The video circuitry is similarly easy to locate and identify.  Next, we can locate the circuitry that converts the video signal to the format needed to drive the rows and columns.  From here we can follow the signal paths to the row and column drivers along the edges of the display panel. 

The panels themselves look quite simple except for the flexible circuitry that seems to carry an impossibly high density of signal lines.  These lines are fed from driver chips that are either on the edges of the chassis or built right into the flexible circuits that connect to the panel.

If we take our observations one level higher and begin to probe the various circuits, we find the rows of these displays being driven with sequential activating signals and the columns carrying the video information in proper synchronization with the rows as each is activated in turn.  It all seems so logical – and yes – even easy.   Plasma panels may look a bit more complicated with their time sequenced gray scale signals, but once we appreciate the concept of 8 or 10 sub-frames providing the brightness modulation, the addressing becomes similarly easy to understand.   

So why did it take us so long to achieve this level of elegant simplicity?  

Do you remember CRTs?  They were once the dominant display technology – as a matter of fact, for many years, the only one.  In the mid-60s, I took on the challenge of assembling a 27-inch television from a kit sold by a company that only some of you may remember – Heathkit.  I spent many hours placing and soldering the various circuit components into the boards and then mounting all of these into place in the chassis.  It was a moment of sheer terror when I finally flipped the power switch to see what would happen.  To my great relief, a video image of sorts appeared on the screen.  The next steps were to “align” the picture and to adjust the “convergence” boards.   Without these steps, the video image was geometrically distorted and the three colors were badly out of registration.   The convergence board contained at least 24 adjustments that acted on the various parts of the screen – sort of.  The adjustments interacted with each other so that it was necessary to repeat the process over and over until finally the colors were all properly aligned with each other.  Even after all this adjusting, vertical lines were only more or less vertical and a full-screen circle was noticeably not quite a circle. 

Well, the years passed and CRT technology continued to improve.  In the mid-90’s I acquired a 32-inch Sony Trinitron television.   Well over ten years later this same television is still working perfectly.  The image has stayed perfectly converged – with no help from me.  Colors are still as pure and as perfect as the video signal can make them.   Lines are straight and circles are as perfect as I can observe.  Not only that, this CRT television has experienced several relocations with no change in its operating characteristics.  What a contrast to the Heathkit television that I built thirty years earlier! 

Thus, it seems that every technology needs time and effort to achieve its eventual full capabilities.  And so it has been and will be with both LCDs and Plasma panels.  It has taken many years to work out the optimum way to do each step, be it the way the pixels are laid out in an LCD or how the discharge is controlled in a plasma panel.  The combinations of materials and driving waveforms have similarly taken years of effort to optimize.  

But once this optimization is achieved, the final product is exceedingly robust, elegant in its simplicity, and capable of many years of reliable operation.  The good news is that even with the excellent performance that we have already achieved from both LC and Plasma displays, we still have much that can be done before we get to full product maturity.  LC displays, for example, are beginning to transition to LED backlighting and Plasma panels are becoming more efficient, brighter, and achieving highly reliable long-life operation. 

The past forty years have brought us to full product success.  It is likely to take another ten to twenty years before LCDs and Plasma panels achieve their full technology maturity.  It will be exciting to see just exactly what those displays will look like.  Should you wish to comment on this column, you may contact me directly from this site or by telephone at 425-898-9117.