Selective Dispersion of Projected Light - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 36 Old 01-05-14, 05:50 PM Thread Starter
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Selective Dispersion of Projected Light

A method I have been contemplating for some time to increase screen gain is to find a way to selectively disperse projected light. The idea is to disperse light more in the horizontal plane and less in the vertical plane. After all, you don't sit on the ceiling to watch a movie, and most of us don't sit down on the floor.

I tried an interesting experiment today. The basic idea is to machine grooves in the vertical direction that have a semi-circular cross-section. The curvature within each groove will serve to disperse light more in the horizontal plane than in the vertical. The experiment utilized a piece of Plexiglas that I then "machined" grooves into in one particular direction (vertical) by using a wire wheel brush with fine brass wires. This is the same method used to give metals a linear brushed finish. I then used a black Sharpie marker and coated the brushed surface doing my best to get the marker ink down into the grooves.

I then put this small test panel up on the wall and checked how the light was being dispersed from the projector. It definitely works to disperse light more in the horizontal direction than in the vertical direction. I realize this is a very crude attempt but does show what can be done with simple methods. I know that grooves are made but not sure at this point if I was able to achieve a semi-circular cross-section within each groove. Also, in hindsight, it would have been better to use an opaque material rather than Plexiglas. The Sharpie marker helped with that a little but it was still too transparent.

I would like to hear what people think about using this method, perhaps combined with semi-reflective materials (paint or base materials). If anyone has any ideas on how to do this on a full-size screen I would love to hear them. I think that the ultimate goal would be to have individual reflective elements on the screen (sub-pixel size) that would control the reflected light cone in both the horizontal and vertical directions with compression of the light cone mainly in the vertical. Any ideas?
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post #2 of 36 Old 01-05-14, 07:24 PM Thread Starter
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Re: Selective Dispersion of Projected Light

Here is the concept on a 1 x 1 pixel scale showing 6 grooves. Hope this helps in understanding the concept.
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Selective Dispersion of Projected Light-pixel-element-vertical-grooves-crop.jpg  

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post #3 of 36 Old 01-06-14, 01:56 PM Thread Starter
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Re: Selective Dispersion of Projected Light

Could possible find a company that could prep the substrate at a reasonable cost. I will have to do more research on this.
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post #4 of 36 Old 01-06-14, 02:25 PM Thread Starter
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Re: Selective Dispersion of Projected Light

Another idea...could this possibly be done using a particular fabric weave? It probably would be grooves but would take advantage of the curvature of the fibers (I'm thinking polymer) and the curvature generated by the weave pattern. Any thoughts.
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post #5 of 36 Old 01-06-14, 02:49 PM
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Re: Selective Dispersion of Projected Light

This is an interesting idea, but it sounds like it's a bit complex for the average DIY'er. You might look into existing films as well. One of the problems with this whole idea is that due to the high resolution of our current PJ's and video sources (let alone the coming 4k and better stuff) the lines would have to be VERY close together to not be seen (or cause visual artifacts) during viewing.

Please keep us posted on your research!
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post #6 of 36 Old 01-06-14, 03:52 PM Thread Starter
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Re: Selective Dispersion of Projected Light

Yeah Harp...agreed. The grooves would need to be very small, especially for 4K resolutions. I did some searching for lenticular lenses but it seems the max for large format sheets is 60 lines per inch with would not be adequate. That's part of the reason why I started looking at wire brushes because brushes can be found with wire at 0.003" diameter (76 microns) which would be adequate.
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post #7 of 36 Old 01-06-14, 08:19 PM
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Re: Selective Dispersion of Projected Light

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Pyrometman wrote: View Post
Yeah Harp...agreed. The grooves would need to be very small, especially for 4K resolutions. I did some searching for lenticular lenses but it seems the max for large format sheets is 60 lines per inch with would not be adequate. That's part of the reason why I started looking at wire brushes because brushes can be found with wire at 0.003" diameter (76 microns) which would be adequate.
A wire brush won't give you perfectly straight lines, and getting an even finish might be a problem; but it certainly is worth investigating.
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post #8 of 36 Old 01-07-14, 10:03 AM Thread Starter
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Re: Selective Dispersion of Projected Light

Harp,

I checked the sample that I created...with the best my own eyes can do, the "grooves" wander somewhat confirming your statement. I will have to find a way to keep the grooves straight. I have an idea that involves a rolling pin and fine gauge wire. It will have to wait until the coming weekend however. Any other ideas from anyone would be welcomed.
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post #9 of 36 Old 01-07-14, 03:04 PM
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Re: Selective Dispersion of Projected Light

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Pyrometman wrote: View Post
Harp,

I checked the sample that I created...with the best my own eyes can do, the "grooves" wander somewhat confirming your statement. I will have to find a way to keep the grooves straight. I have an idea that involves a rolling pin and fine gauge wire. It will have to wait until the coming weekend however. Any other ideas from anyone would be welcomed.
While I'm just talking off the top of my head here I think there is a good chance that the vertical grooves don't really need to be totally straight or run the full length of the screen to achieve what you are after.
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post #10 of 36 Old 01-07-14, 05:09 PM Thread Starter
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Re: Selective Dispersion of Projected Light

I think you are essentially correct. I think that the most critical parameter is getting the curvature of the groove that you need to evenly disperse the reflected light to avoid variation in brightness as you move through the horizontal cone.
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