Ferroelectric LCD Monitors

[seankhn]

Hi

Does anyone know of any Ferroelectric LCD based monitors or
microdisplays currently in the market? FLC is different from LCD. It
can only have two states - on or off. LCD has analog response. This
means that you don't have to do a digital to analog conversion to drive
an FLC display. I was wondering if any display manufacturer has tried
to make pixel drivers for an FLC based display given this difference.

Thanks in advance,
Sean

 

[Bob Myers]

Hi

Does anyone know of any Ferroelectric LCD based monitors or
microdisplays currently in the market? FLC is different from LCD. It
can only have two states - on or off. LCD has analog response. This
means that you don't have to do a digital to analog conversion to drive
an FLC display. I was wondering if any display manufacturer has tried
to make pixel drivers for an FLC based display given this difference.

It's been tried - Fujitsu attempted a line of FLC monitor panels (and
monitors) back, as I recall, around the early-to-mid 1990s. One
problem (among several) was that very bistability - driving something like
that at high resolutions is a real headache, and has basically no real
advantage over conventional LCs. "Not having to do a digital to
analog conversion" in the drivers is by no means an advantage per
se. The monitors in question were all monochrome types with limited
gray-scale capability.

There's still at least one company - Displaytech, here in Colorado -
doing FLC-based microdisplays, but having the display built on top
of a CMOS chip does change the economics of what you can do
in the drivers.

Bob M.

 

[seankhn]

It's been tried - Fujitsu attempted a line of FLC monitor panels (and
monitors) back, as I recall, around the early-to-mid 1990s. One
problem (among several) was that very bistability - driving something like
that at high resolutions is a real headache, and has basically no real
advantage over conventional LCs. "Not having to do a digital to
analog conversion" in the drivers is by no means an advantage per
se. The monitors in question were all monochrome types with limited
gray-scale capability.

There's still at least one company - Displaytech, here in Colorado -
doing FLC-based microdisplays, but having the display built on top
of a CMOS chip does change the economics of what you can do
in the drivers.

Bob M.

Thanks for the reply Bob, I assume the difficulty with driving such
monitors has to do with DC balancing? From what i have read FLC
materials, unless driven equally in the reverse direction, would
eventually deteriorate and cause poor picture quality. Does DisplayTech
use any special technique to get around it?

Sean

 

[Bob Myers]

Thanks for the reply Bob, I assume the difficulty with driving such
monitors has to do with DC balancing? From what i have read FLC
materials, unless driven equally in the reverse direction, would
eventually deteriorate and cause poor picture quality. Does DisplayTech
use any special technique to get around it?

DC balancing is a problem for conventional LCs. The main
problem with coming up with a drive scheme for FLCs is the
very thing you mentioned originally - they're either on or off,
with no inherent "gray scale" capability. To get any number of
gray levels, you need to use either temporal (PWM) or
spatial (dithering) modulation - neither of which is a particularly
fun thing, and there's no real advantage in either over a
conventionally-driven LC. So why bother?

Bob M.