DLP projectors

1
HI,
I just saw a paper in which a Pico DLP projector from texas instruments was used for retina visual stimulus projection. Is there any knowledge of whether Psychtoolbox would work with this type of device ? It would greatly simplify setup, as I have a smaller dark room now, and I am demagnifying my visual stimuli by bouncing the stimulus back and forth through several mirrors. Apologies if there were previous posts, but I could not find any.

Tudor
2
--- In psychtoolbox@yahoogroups.com, "xrli2002" <xrli@...> wrote:
> If anyone has a simple solution to reduce the brightness, please let me know.

What's wrong with a neutral density filter[1]? And though not too "neutral", variable ND filters allow one to tune the brightness[2].

Ian
----
[1] Wratten filters are commonly considered to have scientific grade spectral consistency: http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=2928
[2] http://www.singh-ray.com/varind.html
3
"The falling time to half height from maximum brightness is about 15 ms."
...it seems these units cannot be correct. The half-life from full brightness is almost an entire 60Hz frame??

Units aside, interesting that the DLP rise/fall dynamics are reversed from every LCD I've seen...rise times usually much slower than fall ('shark-fin'). Though still short of CRTs, newer LCDs (over last 3 yrs) are becoming more an more impulse like.

Is this a 1 or 3 chip DLP? Given its a Christie it could be a 3 chip, but would be drastically more expensive.

Thanks,
Thad.

--- In psychtoolbox@yahoogroups.com, "xrli2002" <xrli@...> wrote:
>
> This reminds me to share my experience of Christie DLP projectors.
>
> We recently tested a DLP projector used for MRI scanner. I like to share some result in case that someone is interesed in it.
>
> Onset timing is pretty stable. The time delay from Screen('flip') is about 20 ms (an old model of the same brand is about 70 ms with larger variation) for both VGA and DVI input. This is a little unbelievable. And a good feature is that, it is always 20 ms, no matter which part of screen the stimulus is. This means the display is not scanning line by line (as CRT and LCD do).
>
> The rising and falling time are not consistent. The former is very fast (<1ms), while the falling time is not as good as rising time. The falling time to half height from maximum brightness is about 15 ms.
>
> Its color property is also good according to our measurement.
>
> Its brightness is very high, and display size is big. These are good features normally, but become problem to us. We have to use a special lens to achieve shorter throw distance and smaller display size.
>
> If anyone has a simple solution to reduce the brightness, please let me know.
>
> Thanks.
>
> -Xiangrui
>
>
>
> --- In psychtoolbox@yahoogroups.com, tudor badea <tudorcb@> wrote:
> >
> > HI,
> > I just saw a paper in which a Pico DLP projector from texas instruments was used for retina visual stimulus projection. Is there any knowledge of whether Psychtoolbox would work with this type of device ? It would greatly simplify setup, as I have a smaller dark room now, and I am demagnifying my visual stimuli by bouncing the stimulus back and forth through several mirrors. Apologies if there were previous posts, but I could not find any.
> >
> > Tudor
> >
>
4
Ciao PTB community,

we try to setup a vision experiment in the MEG that needs a high refresh rate (something above 60 Hz) for empirical reasons. We are using a Panasonic 3 chip DLP projector for stimulation that according to the manual and the control settings in the grafics card should support refresh rates up to 120 Hz.
After various timing tests on the setup with a photo diode, we found a variable delay between stimulus onset and trigger. As well stimulus ontimes below 50 msecs do not seem to work (in fact 25 msecs seem to be either 16 msecs or 33 msecs). We tried combinations of different refresh rates, pixel resolutions and monitor settings (projector in single mode, clone mode and dual view mode). PTB does not report any missed flips, but only 60 Hz seems to yield proper timing. The same piece of code run on a LCD screen works fine.

Info
Dell T3400 Intel QuadCore 2
Windows XP
nVidia grafics card
PTB 3.0.8 -beta; SVN Revision 1561

Any suggestions?

Thank you. Best,
Andreas Wutz
Center for Mind and Brain Sciences,
University of Trento



--- In psychtoolbox@yahoogroups.com, scovils@... wrote:
>
> On a somewhat related note,
>
> does anyone know of any high resolution, reasonable high speed projectors? We're looking to do some vision work and want to have low latency, but unfortunately it seems the newest 1080i (or similar resolution) projectors that support "120hz" are using two inputs at 60Hz, which leaves us with still the latency a 60Hz system would.
>
> Anybody have any suggestions?
>
> Thanks,
>
> Stephen Scovil,
> BioMotionLab,
> Queen's University
>
>
> ----- Original Message -----
> From: xrli2002 <xrli2002@...>
> Date: Monday, April 18, 2011 6:00 pm
> Subject: [psychtoolbox] Re: DLP projectors
> To: psychtoolbox@yahoogroups.com
>
> > Alan's suspicion was right. The long falling time comes
> > measurement instrument. The blame is the photocell. The actual
> > blame should be me :)
> >
> > I haven¡¯t measured the DLP with photodiode yet because of
> > access limitation. But the result comparison from LCD confirmed
> > the reason. With the photocell I used before, the falling time
> > is about 15ms, but with a photodiode, it is less than a
> > millisecond to fall to half of maximum height. The time to reach
> > half maximum height for the LCD is about 2ms. This means the
> > Dell P2211H is almost good enough for vision experiments.
> >
> > The more expensive Dell U2211P is actually worse in term of
> > timing. The above two numbers are 3 and 5 ms respectively.
> >
> > I will measure the DLP and report the result if I get a chance.
> >
> > -Xiangrui
> >
> > --- In psychtoolbox@yahoogroups.com, "xrli2002" <xrli@> wrote:
> > >
> > > Yes, it is about 15 ms. That is why I think it is not good in
> > that aspect. However, it is possible that my method intruduced
> > the error. What I used are a photocell + a battery + a resistor
> > + oscilloscope. I measured the voltage at the two ends of the
> > resistor. Do you think this could introduce some problem?
> > >
> > > Yes, it is a 3-chip DLP, and expensive ...
> > >
> > > -Xiangrui
> > >
> > > --- In psychtoolbox@yahoogroups.com, "thadczuba"
> > <tbc.class@> wrote:
> > > >
> > > > "The falling time to half height from maximum brightness is
> > about 15 ms."
> > > > ...it seems these units cannot be correct. The half-life
> > from full brightness is almost an entire 60Hz frame??
> > > >
> > > > Units aside, interesting that the DLP rise/fall dynamics are
> > reversed from every LCD I've seen...rise times usually much
> > slower than fall ('shark-fin'). Though still short of CRTs,
> > newer LCDs (over last 3 yrs) are becoming more an more impulse like.
> > > >
> > > > Is this a 1 or 3 chip DLP? Given its a Christie it could be
> > a 3 chip, but would be drastically more expensive.
> > > >
> > > > Thanks,
> > > > Thad.
> > > >
> > > > --- In psychtoolbox@yahoogroups.com, "xrli2002" <xrli@> wrote:
> > > > >
> > > > > This reminds me to share my experience of Christie DLP
> > projectors.> > >
> > > > > We recently tested a DLP projector used for MRI scanner. I
> > like to share some result in case that someone is interesed in it.
> > > > >
> > > > > Onset timing is pretty stable. The time delay from
> > Screen('flip') is about 20 ms (an old model of the same brand is
> > about 70 ms with larger variation) for both VGA and DVI input.
> > This is a little unbelievable. And a good feature is that, it is
> > always 20 ms, no matter which part of screen the stimulus is.
> > This means the display is not scanning line by line (as CRT and
> > LCD do).
> > > > >
> > > > > The rising and falling time are not consistent. The former
> > is very fast (<1ms), while the falling time is not as good as
> > rising time. The falling time to half height from maximum
> > brightness is about 15 ms.
> > > > >
> > > > > Its color property is also good according to our measurement.
> > > > >
> > > > > Its brightness is very high, and display size is big.
> > These are good features normally, but become problem to us. We
> > have to use a special lens to achieve shorter throw distance and
> > smaller display size.
> > > > >
> > > > > If anyone has a simple solution to reduce the brightness,
> > please let me know.
> > > > >
> > > > > Thanks.
> > > > >
> > > > > -Xiangrui
> > > > >
> > > > >
> > > > >
> > > > > --- In psychtoolbox@yahoogroups.com, tudor badea
> > <tudorcb@> wrote:
> > > > > >
> > > > > > HI,
> > > > > > I just saw a paper in which a Pico DLP projector
> > from texas instruments was used for retina visual stimulus
> > projection. Is there any knowledge of whether Psychtoolbox
> > would work with this type of device ? It would greatly
> > simplify setup, as I have a smaller dark room now, and I am
> > demagnifying my visual stimuli by bouncing the stimulus back and
> > forth through several mirrors. Apologies if there were
> > previous posts, but I could not find any.
> > > > > >
> > > > > > Tudor
> > > > > >
> > > > >
> > > >
> > >
> >
> >
> >
>