| miatawnt2b |
I have read about this new Sony screen that is black and is supposed to do wonders for contrast. Does anyone know of a way to DIY this sort of screen? I need all the contrast ratio I can get.
J |
|
|
| ancorp |
| quote: | Originally posted by slize
ask sony :bigeyes: |
Ahahaa, Sorry, that reallyl made me laugh:D |
|
|
| jdevo2004 |
| what about using a highly reflective material...like shiney gift wrap and place a thin black translucent "wedding dress" type material over it? Wouldnt the refective material refect the white light well while the black material makes the darks look darker? Just a thought. |
|
|
| dwk123 |
I'd guess that it's going to be very difficult to DIY something like this. The idea behind the screen is that it is highly reflective only for the 3 specific wavelengths that make up a projected RGB image, and is otherwise absorptive. Since ambient light is typically very broad-spectrum, it will contain relatively small energy in any single narrow band like the ones that are reflected by the screen, thus giving the high contrast ratio.
I don't know how Sony actually does this, but typically this type of wavelength sensitivity is a thin-film application - I don't think 'normal' chromatic filters have anywhere near this type of selectivity. |
|
|
| davemcmahon |
| Hey where did you see this new screen, sounds intresting and would look better in an average room. |
|
|
| slize |
just a thought;
as lcd beamed light is polarized (through the technique an LC-Display works) what about the possibilty, that this filter on the screen is some kind of polarizing filter again...
as ambient light is mainly not polarized (this is visible through an LCD; cause it is mainly dark) this filter on the screen only lets the beamed (polarized) light through onto an reflective material , which is passed back to the viewer... so the ambient light is held back an the beamed light shines back so th econtrast would be awesome...
sorry for my poor english; i hope this is understandable to those, who know how an LCD works...
just a thought... |
|
|
| Squalish |
While messing with the polarization can do some amazing stuff (like one of the best means of making a multicolor true stereoscopic screen[though you still need classes]), I don't think that's what they're doing. They're using optical bandpass / notch filters. They have to have some specified means of coating the screen w/ 3 pigments that only reflect very narrow bands of light, and transmit (are transparent to) most of the rest of the visible spectrum.
The closest I've seen to the idea is the Light Fusion screen, which involves painting + sanding down three colored coats over an acrylic mirror. Thiswas at one point the crème de le crème of the AVSForum DIY screens section - one of its supporters who does HT installations for a living bragged that it beat the several thousand dollar Stewart screens being exhibitted at a trade show.
The Fusion is very expensive in DIY terms, mostly in the cost of the mirror/shipping + the labor involved. I doubt that you'll see anything DIYed that works on the exact same principle as the Sony product, though, and it costs about $2000 last I heard. |
|
|
| davemcmahon |
| Hello here is the wavelength chart from the US patent |
|
|
| davemcmahon |
| I also have the entire patent if anyone wants it. |
|
|
| Donny Bahama |
This thing is capable of excellent blacks and contrast even in a well-lit room:
| quote: | Originally posted by Squalish
costs about $2000 last I heard. |
Unfortunately, that price is for an 80" diagonal screen. OUCH! Gotta be some inexpensive DIY way to do this... |
|
|
| ancorp |
Wow, what a difference...
Thanks for the shot, Donny.
Cheers,
Alex |
|
|
| charlie10 |
Is there any material that can absorb light between 490 to 530nm while transmitting other wavelengths? I was thinking along the lines of specialty theater gels. This would look like a yellow gel I believe.
If one could find that, and another that absorbed 560 to 615nm, one could stick a sheet /coat of each of those in front of the projection screen. This should make the blacks blacker (absorbing ~40% of unwanted ambient light) without reducing the R G or B from the LCD.
Actually... I guess it would make the blacks sort of Purplish (guess)? Two more materials absorbing <475 and >650nm would be needed to get closer to Black. Maybe the colors would just get totally out of whack.... there's probably a good reason why Sony has a patent on their screen...
Here are some spectral charts:
http://www.sewanee.edu/chem/Chem&Ar...gment&light.htm
including a yellow gel... but it looks like that one is far too wideband.
I also found an interesting explanation at http://library.thinkquest.org/27066...nlchanges.html. |
|
|
| Donny Bahama |
Way to go, charlie10! Glad someone is thinking about this. Even if the ideas don't work, they may well lead to something that does. Personally, I don't have enough knowledge of optics, etc. to contribute much. If anything, I'll take the low-tech approach...
I'm thinking about a glossy black background (to - in theory - reinforce the areas of projected black/gray in high ambient light conditions) covered by a layer of... not sure what this fabric is called, but it's a sheer fabric - hold it up and you can see right through it, but place it on a surface and it has a sheen to it. Moire may be a problem, I'm not sure. If so, is there a way to deal with that? Anyway, due to the sheen, I'm thinking this fabric may have a decent gain to it. Not sure what effect the textured surface might have on image focus and/or whether the viewing cone might be positively or negatively effected, but the fabric I'm thinking of is pretty flat - not much texture to it. If the projection surface needed to be smoothed out, I'm guessing you could actually put a coat or two of some kind of clear finish (gloss? satin?) which would have the added effect of adhering it to the glossy black back surface.
Just thinking out loud here. Anyway, it wouldn't cost much to fab up a sample piece. (But first I have to build a projector!) |
|
|
| Hezz |
I wonder if this screen is just some kind of large diffraction grating with small areas tuned to each wavelength which would represent pixels for each pixel on the LCD.
Diffraction gratings are selective in the wavelength of light that they diffract. In theory you could design a blown up replica of the LCD pixel geometry and create a small diffraction patch tuned to the exact light wavelength at the subpixel location.
The upper areas could be coated with a black non reflective coating and the lower areas made highly reflective. In this case the lower areas would diffract light at only the proper wavelength and normal incedent light would be mostly absorbed.
Maybe?
If this is the case it would be the perfect screen because it would basically absorb all ambient light and diffract only the wavelengths designed for. Also, the diffraction is perfect because it basically acts diffusive at only the diffracted wavelengths.
The hard part about making this would be the mold because it would require micro machining or photo lythography etching. Once a metal stamps was made you could just stamp out the screens in warmed up acyrlic much like a fresnel lens is made only on a larger scale.
Hezz |
|
|
| Dazzzla |
| quote: | | I wonder if this screen is just some kind of large diffraction grating with small areas tuned to each wavelength which would represent pixels for each pixel on the LCD. |
I think that it would be made with dichroic, simular principal as the diffraction grating though.
DJ |
|
|
| Hezz |
Ok guys,
I have read the patent and it describes four different ways that the screen can be made but all of the amount to some kind of triple bandpass filter.
My first idea on how it was made would be too difficult and expensive to impliment, plus it wouldn't work for more than one aspect ratio.
In the patent the filter is constructed of four layers of polymer films which either selectively reflect the bandbass wavelengths or absorb the non bandpass wavelengths.
The materials are just transperant polymer films with colorants or dyes added which either reflect of absorb the needed frequencies.
To make a screen filter on top of a regular diffusive screen you would need a transmissive filter. Or if you had a reflective filter you could dispense with anything but the filter layer except a backing to hold it together and absorb more light.
Hezz |
|
|
| charlie10 |
Ok done reading the patent. Hezz is right looks like it boils down to an expensive triple-bandpass filter.
Not sure about diy potential here. The patent is totally vague on how exactly to construct a triple bandpass filter, but as an example it explains one way to build a double bandpass filter. It uses refraction at a micro scale. All you have to do is put down 13 layers of 3 materials (gold, quartz, and titanium dioxide) in the right order. Each layer is a thin film with an exact thickness, ie. layer 8 is 270.66nm of Ti02, and layer 9 is 4.16nm of gold.
Unfortunately, I have to say I used up all my Rust-o-leum #3166 "Elemental Gold, Thin Spray" last week re-surfacing my personal bling bling collection. (A guy has got to have his Priorities straight!)
Speaking of bling bling, we might be to take the filter film off of one of their triple bandpass rear projection screens (transmissive), cut it up into little rectangles, and make em into eyeglasses. Then just wear a pair of those shades around whenever we want to watch an RGB digital projection with the lights on. Let's see if a 160"x90" Sony RP blackscreen is $7000, and eyeglasses are 2x1"x2", that's about 3600 pairs of shades at 2 bucks each. Or 5 bucks for the Oakley style :cool:
who is up for a group buy? hehe :D |
|
|
| Hezz |
I think it would be possible for us to build one of these screens in a different manner if we had someone with sufficient knowledge on what colorants to add for each of the four films to make the filters and the desired cut off ranges. One filter must block or absorb all light below the lowest of the three frequencies. The next must block or absorb all light above the highest of the three frequencies. The next two filters must let all light pass except in the regions between the three wavelength zones. In this way you can create a filter with three distinct narrow frequency notches that pass light only at those frequencies.
We would not use films because these are likely to be custom made and expensive in large sheets. In reality the polymer film is just a carrier for the colorants and or the minerals that do the filtering. It seems to me that if you know the right things to add to each filter you could mix your own with a clear laquer or polyuethane and spray each layer on a diffusive screen building up the four successive layers as you go.
Hezz |
|
|
| Hezz |
DonnyB,
I will respond to your e-mail when I have some more time.
Hezz |
|
|
| pinkmouse |
| Dye doping will not work. The very sharp bandpass notches that are needed can only be produced by thin film dichroics, pigment molecules are far too random. |
|
|
| Hezz |
Pinkmouse,
If the bandpass regions were relaxed significantly for a DIY project so they were not so steep could dichroic dyes work to some success in a clear based carrier.
Everybody,
This whole black screen ChromaVue Sony screen thing is causing a great pradigm shift in my thinking and I am beginning to visualize what I think would be the perfect projection screen and how it would be build if such a thing could be manufactured. It would be fundamentally different than anything I have ever seen. First, it would have a dead black backing that did a good job of absorbing all light. Then it would be covered with a fine thin coating of tiny highly reflective glass mirror beads. These are tiny beads that are spherical in shape and have a mirror surface coated on them. The beads are small enough so that they are three or four times smaller than an on screen pixel.
Next the reflective beads are coated with the proper dialectric materials to created the narrow bandpass filters which transmit only the narrow spectrum three colors into the mirrored beads.
The beads transmit only the narrow bands which reflect back in all directions due to the mirror coating. Because of the spherical shape of the bead the light is reflected back in a wide angle thereby creating a virtual diffusive effect for the viewers.
The black backing of the screen is kind of like a shadow mask on a CRT television which increases black levels.
Such a screen would have high gain, high contrast, and little or no hotspotting and a wide viewing angle. The perfect screen.
If these little reflective glass beads with dichroic filters on them could be manufactured then anyone could make a very high end screen with only some black paint and some clear adhesive and some careful application.
Hezz |
|
|
| pinkmouse |
| quote: | Originally posted by Hezz
...If the bandpass regions were relaxed significantly for a DIY project so they were not so steep could dichroic dyes work to some success in a clear based carrier. ..[quote]
You misunderstand. Dichroics are made by coating glass, as in the Sony patent.
[quote]...These are tiny beads that are spherical in shape and have a mirror surface coated on them... |
Good idea, but as I read the patent, this would by covered. But I'm not a patent lawyer... ;) |
|
|
| Hezz |
Guys,
I have gone through the patent and the patent does not cover any aspect of manufacturing of the filters except in the most superficial detail.
It seems to assume that currently existing technology can be used in four different ways to build the screen. It is more of an idea patent then a manufacturing process patent.
Also, I made some assumptions above. One was that the dialectric materials that are deposited on glass to make dichroic filters could also be deposited on a metal like aluminum. So that they could be deposited on a mirrored surface.
The patent also describes dichroic filters which are reflective in the bandpass areas and transparent in the other light wavelengths. If dichroics of this nature could be deposited on glass then you could make glass beads from highly absorbent black glass and then polish them and deposit the reflective dichroic filter layers on the beads.
In closing, I wonder if anyone has tried making a high contrast DIY screen out of flat black paint and the reflective glass beads used for mixing with paint for road signs.
You could bond a thin coating of the reflective glass beads over a painted flat black surface for a higher contrast screen. Granted this does not have the filtering effect of the ChromaVue but it might work well for a cheap DIY screen.
Hezz |
|
|
| Donny Bahama |
Jinan Huaming Microbead (http://glassbead.en.alibaba.com/offerlist.html) looks to be a good source for such beads. They even have aluminum coated glass beads - I wonder if these could somehow be polished to a mirror-like surface?
Anyway, on the off chance that they may somehow have the capability of restricting the wavelengths to be reflected, I have sent them an inquiry. If he responds with, "what range of wavelengths are we talking about?", I'm going to be like "Uuuhhhh..."
edit: It seems to me like this approach is likely to result in serious hotspotting - especially in projected white or near-white colors. |
|
|
| Donny Bahama |
This page has a table showing| quote: | | numerical values for the refractive index of water as a function of wavelength in the visible part of the spectrum. |
It gives wavelengths from 400 to 700nm (violet to red) with a mean value of 550 for a yellowish-green.
Now, I have no idea how the refractive index of water translates to air, but Jinan Huaming Microbead seems to have a certain degree of control over the refractive index of their beads, so maybe we're onto something, here...
If we could get three types of beads with three refractive indices - one each optimized for red, green and blue, and find a way to apply three uniform coats to a black background...? |
|
|
| Hezz |
I think if the beads were true spheres the hotspotting would be reduced but I may be wrong. The best method would be if the glass beads were made out of a black highly light absorbent glass and reflective dichroic filter material deposited right on the glass spheres. The beads would reflect only the narrow bands and absorb the other light. If only the front of the beads could be covered with the filter material it would be even better. IF heat became an issue the backing material could be black anonized aluminum to dissipate the heat.
But here is my newest idea for a cheap DIY screen.
Start with a piece of canvas or plywood and prepare the surface to make it relatively smooth. Then apply two or three coats of flat black laytex or enamel. Laytex is generally more flat but is less durable. Then using some kind of clear spray adhesive or beads mixed with clear poly or something cover the panel of black paint with a thin but evenly coated layer of the reflective beads.
Now the final layer needs to be a fine open weave cloth of a white color that is kind of sheer but not very shiney. Usually materials of this type are made of synthetics like nylon or polyester and are more shiney than cottons or natural fibers.
Stretch the fabric tightly over the panel so as to create tiny open voids in the fabic as much as possible. Hopefully any hottspotting could be controlled with this outer fabric.
Hezz |
|
|
| Donny Bahama |
| quote: | Originally posted by Hezz
[B]The best method would be if the glass beads were made out of a black highly light absorbent glass |
Wait! I know! Black velvet beads!!! :D Could be hard to coat, though! ;)| quote: | | If only the front of the beads could be covered with the filter material it would be even better. |
I don't even want to think about the amount of time it would take to turn each bead so that it was filter side out! :D| quote: | | Start with a piece of canvas or plywood and prepare the surface to make it relatively smooth. |
Or start with MDO plywood - very smooth and beloved by sign painters for it's paper outer layers. |
|
|
| Hezz |
DonnyB,
If you can talk this company into making glass beads out of a black glass that is visable light absorbant and then have a reflective dichroic filter with narrow reflective bands at the three RGB frequencies coated onto the beads we would have the perfect glass beads for projector screens. They could be used by themselves for high gain screen and combined with other methods for screen with less hotspotting.
Hezz |
|
|
| Donny Bahama |
I'll see what I can do.
Just so I don't come off as an idiot when talking to him, are the wavelengths in the table (on the link I posted) correct? If so, we're looking to reflect 450nm (blue), 525nm (green) and 575nm (red). Sound right? |
|
|
| Hezz |
DonnyB,
The patent uses these ranges for the passband. So for a reflective filter type these frequency ranges need to be reflective.
475-490 nm BLUE,
525-565 nm GREEN,
615-650 nm RED,
These are the ranges used in the patent. It is important that each passband cover a small range to account for projector variations in color.
Also,
The other option is to coat white glass beads or mirrored glass beads with a transmissive filter at the same passbands.
Hezz |
|
|
| Hezz |
Here is another Idea that I had and I wonder if it would work.
It's a variation on the Prof's DIY high gain screen.
First a sturdy backing material. Then a mylar mirrored surface or something similar. Then a thin sheer black colored material stretched tightly over the mirrored surface. This followed by a thin acrylic final layer that is sand blasted to a frosty surface finish.
It seems that the black material would let light pass through it's open weaves at angles close to perpendicular and at angles which are not too steep but the farther any ambient light is away from the perpendicular angle the more the black mesh would absorb it. This black mesh would probably reduce the gain of the screen but would hopefully increase contrast somewhat by acting like a shadow mask and increase contrast in higher ambient light conditions.
Hezz |
|
|
| nonamer66 |
| you guys are really talking over my head but darn it you guys got me interested in this. so is there any further developments? |
|
|
| Donny Bahama |
| Absolutely no response from Jinan Huaming Microbead. :mad: |
|
|
| Hezz |
Donny,
I wonder if anyone has patented this idea of putting dichroic filters on microbeads. I think the right formulation would be the screen to end all screens.
In fact I think that it is such a good idea that someone might steal it.
The only issue is that manufacturing could be difficult and since I'm not a chemist I have no real idea how difficult it would be to coat glass microbead with the specific dilectric materials.
Dichroic beads in larger sizes are already made for hobbiests but these are too large and not highly accurate filters with discrete passbands.
Since the glass microbeads are already available I think the best approach would be to contact the optical companies that make dichroic filters for other purposes since they would likely already be the closest to having the knowledge and technology to do it.
Hezz |
|
|
| charlie10 |
I read about a fabrication technique which might be useful here. (Unfortunately I can't find the link):
Clear beads are mixed into a liquid adhesive substrate. The mixture is painted onto a surface. As the substrate dries, it recedes, exposing part of the surface of each bead. I think this was for a retroreflective application. |
|
|
| Hezz |
Charlie,
Thanks for the info. One thing that I have not been able to determine is whether or not the glass beads that are available and are used for making reflective paint are made from clear glass or white glass.
In theory the perfect screen for most applications would be made from white glass microbeads and then dichroic filter dialectric material which is transmissive at the three passbands and absorbative at all other frequencies would be deposited on the glass microbeads.
The white glass is highly diffusive and gives the best viewing angle and true white colors. But because the filter layer would absorb all light except at the three narrow passbands most ambient light would not be reflected or diffused and the screen would appear dark gray or black even in a well lit room. Only the light at the passbands which would travel through the filter would hit the white glass microbead surface and be diffused\reflected back to the viewer.
Contrast could be improved even further by depositing a thin even layer of the microbeads over a black light aborbing surface. It would act like a shadow mask increasing appearant black levels because of the very small black spaces between the glass microbeads.
Hezz |
|
|
| Booger |
I ran across this past thread from jr hilton.
http://www.diyaudio.com/forums/show...0&pagenumber=13
He describes how to make a black screen out of sandblasted lass and paint. I know this is not the method being described in this post, but it would be something a DIYer can do.
| quote: |
Hot spotting should not be a problem, if it is here are two of the reasons:
1) Too much direct light is getting through the screen,e.g. the screen is not diffracting the light. Sorry a shower curtain will never work! As it is not diffracting enough light. Hot spotting is ocouring because too many of the rays of light are able to pass straight through the screen in comparison to the number that are being diffracted. Hopefully the following diagram will help you
***Hopefully the diagram I am now going to refer to will upload ok with this post!***
In diagram 1 the black lines are the light that passes straight through the screen, the grey lines are the lines that are are being diffracted by the pitts in the glass. By the way the only way to go is a screen made out of glass!! Basically what is hanening is you are seeing too many rays of light coming straight from the blub e.g. the black lines!!!
In diagram 2 the screen is far more pitted on the back so all of the light is diffracted. Imagine millions more light lines of course, the result is a dimmer screen but with no noticeable hot spotting. Very little light just goes straight through the screen, un-diffracted, now that is the secret to success.
By the way, anyone wondering why the glass is thicker on picture 2, it’s not intended to be, when I was drawing it in Paint I forgot to move the straight line, and started to put in the light lines, then I realized and couldn’t be bothered to start agin!
To anyone wondering if this works, back in the 1980’s I did presentations using 16mm film projectors with screens sometimes greater than 6 feet in diameter, with no hot spotting problems. Some “serious film amateurs” (very serious in my mind!!!) had small cimemas in their houses and used rear projection because you can hide some of the sound of the projectors, and again no hot spot problems. The surface of the glass is not smooth, it is very very very pitted, so the light is diffracted in all directions.
2) Reason two, is down to incorrect optics, e.g. focal length of light condenser lenses, sorry I cant give any more info here but it is really a case by case scenario.
As for making a screen, they are called ground glass, but having talked to some of my ex-colleagues recently, it would appear that the name is a little deceptive; a better description is ‘severely sand blasted glass’, where the glass is really white and ruff on the projection surface (any one who has done any sand blasting of glass will recognise what I mean by that), not just a little white, but really white. Easy to make if you have a compressor and sand blasting gun. The firm I used to work for made our own screens in our workshop, so it can be done, we didn’t have any special tools ect. Now a very interesting idea I have been told about is that once the screen was sand blasted severely, it was often given a coat of black paint, then using sand paper or steel wool it was scraped back to reveal the top “humps” as it were of glass, leaving a slight back coating, it would improve viewing a wide angles as only diffracted light went through and bright ambient room light was reflected. Diagram 3 shows this idea. It would be interesting for someone to try this again! This was done before the days of easily available anti-reflective coatings. This is also basically the same idea as glass impregnated black plastic screens!
Just one more thing, please stop using / recommending shower curtains, I hope from what I have written above you will all see why they will never work, though I guess they are good just to test your ideas!
I’m working on my own design at the moment, to see if it will work with some old kit that I have accumulated over the years, I will post some results when I get started properly.
jrhilton has attached this image:
Click the thumbnail to see the original image.
|
|
|
|
| Hezz |
Thanks Booger,
I think that old idea JR Hilton describes is the last bit of information we need to make a really good high contrast DIY screen.
So here's my new recipe using JR's idea.
1. Glue mirrored mylar to backing plate.
2. Stretch sheer black or gray cloth across the mirrored surface and glue with clear adhesive.
3. Take a relatively thin sheet of acrylic and sand blast it very thoroughly with small and large size grains.
4. Clean the sheet and spray paint thined down black plastic paint on the surface.
5. Lightly sand or use a scotchbrite pad to remove the top surface of paint and reveal most of the frosty white surface finish but leaving the black paint down in the deeper pits and rough areas.
6. Glue the acylic sheet with clear adhesive to the first reflective sheet.
7. For a higher gain screen omit the sheer cloth between the plastic and mylar mirror.
The image in JR's post didn't save here so here is a copy:
Even though this screen technique was developed with rear projection in mind I think that it would work really well with a mirrored backing.
Hezz |
|
|
| nonamer66 |
| So Hezz. :D you gonna make one now ;) Somebody needs to be the crazy scientist to try this. :smash: |
|
|
| Hezz |
Nonamer66,
I will eventually but I've got to finish my projector first. I always have more ideas than money. Anyways I was hoping that someone who already has a projector and is already experimenting with screens might try it.
I think a small sheet of maybe 24 inches square would make a nice experiment. Especially if it was put up against an already projected image on say a normal painted wall to see if it offered more contrast and gain in higher light conditions.
Hezz |
|
|
| ROJERAO |
| IF we uses a material like this... |
|
|
| Hezz |
ROJERAO,
What exactly is the material used for the screen in your picture.
Hezz |
|
|
| Mikey p |
| I think he is referring to the reflective tape in the picture. |
|
|
| ROJERAO |
| It´s a reflective tape, I´ll try make test with one of this, after I´ll post any results. It´s an ideia... :smash: |
|
|
| TwoSpoons |
Reflective tape wont make a good screen. The stuff is designed to return incident light almost exactly to where it came from (within a degree or two). What you end up with is a screen with exceptionally high gain, so you have to have your head right next to the projector lens to see anything.
I use reflective tape made by both 3M and Reflexite in my work, which is how I'm familiar with the way it operates. |
|
|
| Squalish |
| Lookup "light fusion," on the AVSforums, it's a thin coat of white screenpaint over 1/8" of acrylic, over a mirror sheet. |
|
|
|
