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I want to drive an LCD shutter, which are often found in 3D glasses, with a very low duty cycle (short time transparent, mostly opaque) but also a high frequency. The TN shutters seem to be limited to ~120hz. Pi cell shutters have a higher frequency at 1000hz. However I cannot find an online store for these, which is why I want to stick to TN shutters. What limits the TN shutters to this low frequency? Could I drive them higher at low duty cycles? It's hard to find datasheets on these and the ones I found didn't specify rise/fall times, which I figure is the limiting factor. If I would drive them at a frequency that is too high, with a low duty cycle, can I expect dimming when transparent?

For any others interested in this topic viewing this, I found this source regarding driving LCD shutters, which was really helpful:

https://hackaday.io/project/9676-shutter-glass-tests

Clarification on usecase: I'm interested in using an LCD shutter for limiting exposure of standard CMOS cameras. There are better ways to do it, but this is the one I'm interested in.

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    \$\begingroup\$ this is a case of The X/Y problem. Human visual perception is limited to far below 1kHz – thus, shutters are probabl not what you're looking for if you need higher frequency. However, you don't mention what you need that for, so we can't help you. \$\endgroup\$ – Marcus Müller Dec 20 '16 at 13:26
  • \$\begingroup\$ The case I'm interested in is using it for limiting exposure of standard CMOS cameras. There are better ways to do it, but this is the one I'm interested in. \$\endgroup\$ – J. Don Dec 20 '16 at 13:59
  • \$\begingroup\$ The Liquid Crystal chemistry is almost certainly the limiting factor. If you need millisecond exposure times, I think you'll need another solution. (However, there are uses for ~10ms shutter speeds, it depends what you're doing with the camera). \$\endgroup\$ – Brian Drummond Dec 20 '16 at 18:00
  • \$\begingroup\$ If millisecond exposure times are unpossible, then how can shutter glasses have so little ghosting (a 120hz monitor has a frame of 8.33ms)? Note that I said I need a very low duty cycle. So if the rise and fall time is in the low single milliseconds I think I'm fine. Looking at some LC shutters they are shown a "responsetime" of 2ms. That would mean I can dim to as low as 1/500 to 1/250 (depending what exposuretime means). \$\endgroup\$ – J. Don Dec 20 '16 at 21:04
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The LCDs are all about the name. Liquid Crystals = Crystals in a liquid that are steered around by voltage bias applied between electrodes. The frequency range supported by the devices is related to how fast the crystals can be steered in their liquid medium. You will not be able to change that from what a manufacturer has specified.

Also be aware that LCD crystals move slower in colder temperatures. Often times this can become very obvious if you watch the LCD's on a gas pump in -10F or -20F weather (some equipment applies heater pads to the back of the LCD glass to help with this problem although that would clearly not work for a glass used as a transmissive shutter).

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A lot of TN shutter glasses already go up to about 500Hz. These are the ones advertised with a 2ms responsetime (see https://www.researchgate.net/figure/251880525_fig1_Figure-4-Response-time-measurement-of-shutter-glasses-from-10-to-90).

With a low duty cycle you can go faster but the shutter won't open/close completely.

My mistake was to believe that advertised frequency of shutters in 3D glasses were the maximum (and, possible older, sources from other TN shutters claimed 100Hz too), however for displays they need to account for ghosting and image brightness and so are clocked lower.

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Unfortunately, even in the opaque mode, polarizer lcd shutters will let wide angle array light through.

So even using faster TN (Pi Cells, having a twist to the crystals, allowing ess drag when spinning in the liquid medium) and as you say, accept a triangular (slow rise/fall slews, but an aggregate short transparency period) you will have a washed ouf image from light entering in aporox. 10 degrees off of normal to the shutter plane.

However, there is a new diffractive TN LCD with significant advantages, but much more precise mfg process. This can be found by searching "active domain LCD ". These use no polarizer, do the transmissivity jumps to well over 90 percent from 45. Also, they only accommodate nearly parallel incoming light about 10 degrees max from normal to the plane.

The mfr has white papers that can be ordered, but their site gives good blurbs, particularly on why lcd shutters don't work well for CCD applications.

One last consideration is the scan rate of your CCD. You will likely strobe with the CCD's row scan. If the CCD imager can do à full frame exposure, then you still need to synchronize your shutter to the frame rate, else you will have a rolling strobe effect.

Good luck to you and I hope this helped.

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