Stroboscopic Glasses

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daniloberserk
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Stroboscopic Glasses

Post by daniloberserk » 30 Jun 2022, 01:49

So, I was thinking. Wouldn't be possible to just create "stroboscopic glasses" that flickers at an set frequency that hides the vision for both eyes be an "better" solution for sample and hold motion blur on displays instead of backlight strobing?

I mean, I've never used those Nvidia 3D glasses back then, but I'm pretty sure they work like that (but instead of closing the lid for both eyes, it just flickers between then).

It may sound weird, but wouldn't this work for basically anything? Even VRR wouldn't be a problem, although I'm not sure how our brains would "interpret" the scene.

I did a quick search and it actually exists some stroboscopic glasses for sports training, although I have no idea of how "versatile" it might be when trying to match configurations like, 360 Hz flickering frequency with 1ms of exposition or something like that.

It might be an stupid idea, but I would actually like to try something like that.

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Re: Stroboscopic Glasses

Post by Chief Blur Buster » 02 Jul 2022, 13:09

daniloberserk wrote:
30 Jun 2022, 01:49
So, I was thinking. Wouldn't be possible to just create "stroboscopic glasses" that flickers at an set frequency that hides the vision for both eyes be an "better" solution for sample and hold motion blur on displays instead of backlight strobing?
It definitely a doable concept and there are already multiple threads about this.

viewtopic.php?t=5837
viewtopic.php?t=8509

The second link is the most useful.

The problem is strobe crosstalk is worse than if the LCD and backlight co-operates more perfectly, including the Quick Frame Transport tricks documented at www.blurbusters.com/xg2431

However, it definitely reduces motion blur of displays that does not support motion blur reduction at all.

Also it was discovered that mechanical strobing was superior (less crosstalk) to electronic strobing (shutter), because a rolling shutter slit can slide downwards in sync with the LCD scanout since not all LCD pixels refresh at the same time (high speed videos www.blurbusters.com/scanout ...)

A spinning cardboard disc (connected to Arduino) mounted in front of the monitor, and staring at the monitor through it, works too. Or putting the mechanical shutter in front of an LCD/LCoS projector -- which works great too (better than DLP strobing, in fact!) once the cardboard is cut and slitted properly and the phase is adjusted correctly (need to use a VSYNC monitor, but there are many ways to do that). To avoid spinning the disc fast (60 spins per second) multiple slits in the mechanical rolling shutter is recommended.

If you build a mechanical strobing system, please post here!
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daniloberserk
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Re: Stroboscopic Glasses

Post by daniloberserk » 04 Jul 2022, 06:26

Oh! Just missed those topics! Thanks! I'm glad to know that such thing might be possible/feasible. Maybe as technology evolves it might have some uses.

Although I'll pretty much prefer the 1000Hz journey with FRAT =)

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Re: Stroboscopic Glasses

Post by Chief Blur Buster » 06 Jul 2022, 17:07

daniloberserk wrote:
04 Jul 2022, 06:26
Oh! Just missed those topics! Thanks! I'm glad to know that such thing might be possible/feasible. Maybe as technology evolves it might have some uses.
It's already feasible.

You just have to tune it carefully, and mechanical shutters sometimes produce vastly superior results to the backlight strobing. Especially in monitors with fully adjustable overdrive-gain (100-levels) and you have a phase adjustment (VSYNC time offset) in an Arduino-based synchronous spinning motor, perhaps with ad8e's open source VSYNC-listening algorithm.

But it is a lot of simultaneous skills if you want to build a mechanical strobing rig:

- Understanding rasters (Tearline Jedi)
- Understanding LCD scanout (High Speed Videos of LCD Refresh)
- Understanding Electronic Circuits (wiring a synchronous motor to an Arduino that's listening to VSYNC/VBI heartbeats over USB to PC, with USB--jitter-filtering)
- Understanding Arduino programming (Arduino program that spins the wheel precisely in sync with a dejittered/filtered VSYNC/VBI heartbeat, with a phase-offset adjustment, to allow you to carefully strobe out-of-phase with LCD GtG)
- Understanding Optical Physics (correct slit size, larger disc with more slits to allow slower spin speeds, correct distance of spinning cardboard disc away from screen, correct head position if using a screen instead of a projector)

But if you have all these skills concurrently, please... build it and post your results!

The most successful mechanical strobing is an Arduino-driven spinning rolling shutter in front of a LCD/LCoS projector lens. Then head position does not matter. But you will want to use very thin slit sizes & a large wheel at least several inches away from the projector lens, to create the sharpest shadow edges in the rolling shutter, and the rolling shutter should scan downwards in sync with the LCD/LCoS projector scanout behavior.

A high speed camera (At least 8x your strobe Hz) such as the 960fps feature of a Samsung Galaxy, will make development easier of a mechanical strobing rig.
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elexor
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Re: Stroboscopic Glasses

Post by elexor » 14 Aug 2022, 05:30

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took apart an old set of 3d glasses and connected directly to a 5v arduino direct driving the lcd glass. qft60hz on my lcd works better then I expected. I might end up using this with the dell ultrawide qdoled when I get one. since the monitor has zero blur reduction features global shutter shouldn't be as much of an issue with qft modes + oled g2g.

I want to try mechanical strobing too but this is much easier to setup and more practical to use.

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Re: Stroboscopic Glasses

Post by Chief Blur Buster » 15 Aug 2022, 00:16

elexor wrote:
14 Aug 2022, 05:30
took apart an old set of 3d glasses and connected directly to a 5v arduino direct driving the lcd glass. qft60hz on my lcd works better then I expected. I might end up using this with the dell ultrawide qdoled when I get one. since the monitor has zero blur reduction features global shutter shouldn't be as much of an issue with qft modes + oled g2g.

I want to try mechanical strobing too but this is much easier to setup and more practical to use.
Excellent to see!

As long as the LCD GtG of the shutter is fast enough, and the LCD GtG of the panel is fast enough, your blur-reducing shutter glasses can do some good motion blur reduction duty on almost any non-strobed LCD.

If you decide to try a mechanical spinning wheel, I recommend the table-edge-mounted version, with perhaps 10, 12 or 15 slits, so you only need to spin the wheel 6, 5, or 4 times a second for 60 Hz. The mechanical spinning wheel can also make QFT less necessary by "sweeping" a tiny slit out of phase of the LCD GtG fade zone. it could be very handy for LCD or LCoS projectors as well.

The bonus is a mechanical spinning wheel works wonderfully with LCD projectors (Even cheap $100 chinese LCD projectors). Just make sure the cardboard wheel is designed big enough and calibrate lens-to-shutterwheel distance, if you're going to do mechanical "rolling scan" of the clearly refreshed pixels between the LCD GtG fadezones (not all pixels refresh at same time -- LCD projectors do the same as www.blurbusters.com/scanout ...).

The lack of overdrive in many chinese LCD projectors does add a smidge of crosstalk. On the other hand, the high heat of chinese LCD projectors does accidentally speed up the GtG (run it for a while to make it hot and toasty for minimum crosstalk). But adding software-based overdrive actually creates major reductions to LCD crosstalk.

Incidentally, this is one of the reasons I want to see the existence of an open-source virtual windows indirect display driver with software-based overdrive (superior clone of ATI Radeon overdrive). If you know windows indirect display driver programming, send a PM to say hi!

If you have a ~1000fps high speed camera mode (Samsung Galaxy), this is very handy in debugging a homebuilt external strobing accessory (e.g. whether shutter wheel or modified shuttter glasses)
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elexor
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Re: Stroboscopic Glasses

Post by elexor » 18 Aug 2022, 07:16

Love your ideas really want to see more people experimenting with this stuff! especially the virtual display driver stuff, software bfi sorely needs this. Speaking of cheap chinese projectors do you know of any that can display 60hz without much processing delay?

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