Ultra short throw with Endlighten/7D006
Posted: 20 April 2012 08:32 PM   [ Ignore ]
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Just a warning here, if you want to use an ultra short throw projector you image might get blurry with materials like endlighten or 7D006, in our setup both materials cause the projected image to get blurry on the sides where the light hits the projection surface at a low angle.

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Posted: 20 April 2012 09:03 PM   [ Ignore ]   [ # 1 ]
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Hi Koabi.

this is true if you do not get your projector and material lined up correctly.  I use 7d006 and dell S300w’s without any blur on the edges.  But this requires a lot of calibration.
Short Throw projectors are more susceptible to edge blur with the slightest variance because they expand very quickly from the projection lens.

This is particularly noticeable with our hitachi ultra-short throw reflex projectors.  These do not hold up well to odd angles.

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Posted: 21 April 2012 05:56 AM   [ Ignore ]   [ # 2 ]
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We did several experiments and it looks like we cant get the edges focused at all using either 7d006 or endlighten, but when we project on a wall in the same matter we could get a sharp image. So I’m quite convinced we can not fix this with calibration, but it is a problem with the materials. I just wanted to warn others about this topic because i could not find it anywhere in this forum.

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Posted: 21 April 2012 09:21 AM   [ Ignore ]   [ # 3 ]
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Can you supply specifics as to the hardware in your experiments? 
What thickness of 7d006 and/or endlighten?
What configurations have you tested and with what results?
What projector? 
What distances? 
Are you using a mirror to bounce the image into the materials? 

The above type of information will help make your warning more useful then a blanket statement.  Additionally, I have had sheets of EndLighten that had aberrations in the material which have caused bad images in the past.  These sheets were all replaced by Evonik when I sent them images of the results.

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Posted: 23 April 2012 08:18 AM   [ Ignore ]   [ # 4 ]
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We use an Acer S5301WB for projection, 8mm Endlighten and 3mm 7D006.
Our image is projected over a surface mirror.
The unmirrored projection distance is 50cm.
The unmirrored vertical offset of top and bottom image rows is 70cm and 7cm, so the rays for the most outwards pixels hit the surface at about 55°.
In our experiments we found out:
The image is sharp if we project onto a whiteboard and look at it from bottom.
The image gets blurrier the steeper the rays hit the surface when we project onto 7D006 and the same occurs when we used Rosco Grey.
There is not to much difference between using Endlighten, Acrylic or nothing at all under the projection surface.

So it looks like the blurry image is a result of the diffusor material and the steep angle you get from a UST projector.
We ordered some samples of different projection surfaces in the hope to find some material that works better with this setup.

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Posted: 23 April 2012 11:32 AM   [ Ignore ]   [ # 5 ]
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Interesting.  I’ll try to duplicate your setup as much as possible and post the resulting images from my Dell S300’s.  I also have a Hitachi A350.

My experience is that the A350 has edge blurring due to angle of entry in the rear-projection material.  For that projector I used a thinner rear-projection material (7D513) or thinner.

With the Dell projectors, I do not have this issue.  However, the throw distance is fairly short and my angle of entry is much closer to a straight on projection.

I’d be curious to know if you have the same issue using your surface material in a straight rear-projection (no mirror) configuration.  Obviously this doesn’t work for your slim table build, but it would settle the issue regarding angle of incident versus quality of material.

Again, as I can, I’ll run these tests on my end with my equipment and attempt to post the results.  My lab space is currently configured for another project right now, so I may not be able to generate results until this weekend.

Update: also, I failed to mention how your setup is looks great!  I love the use of maytec (not 80/20 right?) aluminum extrusions.  These products are amazingly good at accommodating the multi-touch requirements.

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Posted: 23 April 2012 02:08 PM   [ Ignore ]   [ # 6 ]
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If the blurriness you are referring to is the lack of gain (general lack of colour and luster) than yes that will occur, if you look at the data sheet http://www.plexiglas-shop.com/pdfs/en/232-20_PLEXIGLAS_RP_EZ_en.pdf then you’ll see that anything with an angle of greater than +-38deg will experience half gain and i presume this will decrease proportionally as your screen size increases

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