re: Transmax

[P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>Date: Mon, 23 Dec 1996 23:35:29 -0600
>From: "P3D Ivester@xxxxxxxxxxxxxxx, Paul"  <ivestep@xxxxxxxxxxx>
>Subject: re: Retina "Beamsplitter"  and New Polarizing Material

>...On another subject, I saw an article in EE Times Dec. 9, 1996 about a new 
>polarizing material.  It was reported to have been invented by Philips 
>Research Laboratories (Eindhoven, The Netherlands) and is being manufactured 
>by Merck Ltd. (Poole, England).  It is called "Transmax", and is claimed to 
>have a transmission of 70% (compared to 40% typical for other polarizing 
>films).  It is intended to provide circular polarization for use in liquid 
>crystal displays.

>Has anyone heard anything more about this material, and whether it might 
>have application in stereoscopic projection?

>Paul Ivester
>Seattle, WA, USA

It's easy to pre-judge claims like that, based on insufficient information.
My initial reaction was that 50% was the theoretical maximum, so I didn't
see how they could claim 70% transmission. I finally looked up the articles,
and it looks like they may have come up with a very clever way to get around
the limitation.

For stereo projection, it sounds like there would be both a challenge and
perhaps a great opportunity. I don't have the article(s) at the moment,
but from memory, the high transmission depends on multiple reflections from
a scattering surface, which works for a diffuse light source such as a flat
panel backlight, but which might not be optimum for projection. (I'm not
very familiar with projector geometries, so take that with a grain of salt.)

The opportunity: I recently posted a speculation that it would be nice if
the light from a projector bulb could be split into two polarizations and
used for the two views, rather than splitting the unpolarized light and
filtering with separate polarizers. This device might do the trick. I believe
the article stated that the light is sent to a sheet of cholesteric liquid
crystal material, and that this material passes about half the light with
one circular polarization, and reflects about half with the opposite
circular polarization. If the transmitted and reflected light could be
separated out, and the circular polarization preserved, then for a single
bulb stereo projector, instead of each view getting ~20% of the light from
the bulb, each view could get nearly 50% of the light from the bulb (minus
various inefficiencies in both cases, of course), a ~150% improvement!

Comments? Opinions?

John Roberts

p.s.: I hadn't heard that cholesteric LC had this property, but it doesn't
sound too implausible. For those who don't get EE Times, it's online,
and has a search facility for articles in back issues. I don't have the
address on this machine, but search engines can find it.


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