Screen Material
To all of you interested to know what Good Rear Projection TV's use as a screen materail, it's simple, it's ground glass, sometimes a thin sheet, sometimes it varies in thickness from edge to center, ground glass has a texture so the viewing angle is wider because when the light hits it it is diffused, and there is less hot spotting, though if you have the F-Lengths correct/optimal with regard to lens hot spotting is not so much of an issue anyway. Ground glass is also used on telecine transfer machines for putting film onto video tape/computer.
Cheaper rear projection tv's have a cheaper Bulk diffuser screen, which uses plastic that has been impregnated with small
particles of material that have a different index of refraction from
the plastic. These particles are dispersed randomly throughout
the plastic, hence the name bulk diffusers. Bulk diffusers have
very high-resolution capabilities, but limited contrast control
relying on tinting to reduce ambient light reflections. This tinting
reduces the projected light through the screen. Bulk diffuser can
have asymmetric viewing angles with the use of a lenticular, but
the addition of a lenticular allows the possibility of moiré
patterns occurring.
Another method used in cheaper rear projection tvs/screens is Beaded Diffusers, Beaded screens use a sheet of transparent beads imbedded into a black plastic substrate. These beads are pushed through the black plastic so that just the tip of the bead is clear through on the viewer side of the screen. By doing this, the ambient light hits the mostly black surface and is absorbed. This allows the beaded screen to display the blackest blacks and hence the best contrast. The back of the bead focuses the projected light through the clear tip of the bead, keeping projected light losses at
a minimum. The beads are small enough for this screen to have high resolution. This screen suffers from the inability to have separate viewing angles in the vertical and horizontal directions, limiting the screen gain or brightness of the display. Because
this is not a lenticular screen, moiré noise is not a big factor, but uneven distribution of the beads can give a mottled look that can be disturbing to the viewer. Speckle is still an issue to be resolved.
The third type often used, again on cheaper tv's/screens are Surface Relief Diffusers (SRD’s). Surface relief diffusers are engineered perturbations in the surface of the plastic that refract the projected light into a diffusive pattern. This type of screen has very fine features allowing for high resolution. The screens can be engineered to have different viewing angles in the vertical and horizontal directions. Since the patterns are random, there is no periodicity to create moiré patterns. Two advantages of SRD’s are high efficiency and a high degree of flexibility in defining viewing angles. Because of their efficiency, SRD’s can have very high gain, however, for good contrast control tinting is sometimes necessary, which negates some of brightness advantage.
Top of the range rear projection tv's use glass-beaded screens, and tinted surface relief diffusers as well as good old fashioned ground glass. I would have to say, IMO the only type of screen that someone can make that will be anywhere near a professional screen is ground glass (sand blasted glass is effectively just the same). Just buy some grinding paste and off you go with some 1500 grade W&D sandpaper, making sure that there is more relief in the centre of the screen if you suffer from very bad hot spotting, if hot spotting is not really a problem, grind the glass evenly all over. If you do use ground glass, you don't need a frsnell, as the ground glass is doing the necessory diffusing.
Hope this helps you all.
To all of you interested to know what Good Rear Projection TV's use as a screen materail, it's simple, it's ground glass, sometimes a thin sheet, sometimes it varies in thickness from edge to center, ground glass has a texture so the viewing angle is wider because when the light hits it it is diffused, and there is less hot spotting, though if you have the F-Lengths correct/optimal with regard to lens hot spotting is not so much of an issue anyway. Ground glass is also used on telecine transfer machines for putting film onto video tape/computer.
Cheaper rear projection tv's have a cheaper Bulk diffuser screen, which uses plastic that has been impregnated with small
particles of material that have a different index of refraction from
the plastic. These particles are dispersed randomly throughout
the plastic, hence the name bulk diffusers. Bulk diffusers have
very high-resolution capabilities, but limited contrast control
relying on tinting to reduce ambient light reflections. This tinting
reduces the projected light through the screen. Bulk diffuser can
have asymmetric viewing angles with the use of a lenticular, but
the addition of a lenticular allows the possibility of moiré
patterns occurring.
Another method used in cheaper rear projection tvs/screens is Beaded Diffusers, Beaded screens use a sheet of transparent beads imbedded into a black plastic substrate. These beads are pushed through the black plastic so that just the tip of the bead is clear through on the viewer side of the screen. By doing this, the ambient light hits the mostly black surface and is absorbed. This allows the beaded screen to display the blackest blacks and hence the best contrast. The back of the bead focuses the projected light through the clear tip of the bead, keeping projected light losses at
a minimum. The beads are small enough for this screen to have high resolution. This screen suffers from the inability to have separate viewing angles in the vertical and horizontal directions, limiting the screen gain or brightness of the display. Because
this is not a lenticular screen, moiré noise is not a big factor, but uneven distribution of the beads can give a mottled look that can be disturbing to the viewer. Speckle is still an issue to be resolved.
The third type often used, again on cheaper tv's/screens are Surface Relief Diffusers (SRD’s). Surface relief diffusers are engineered perturbations in the surface of the plastic that refract the projected light into a diffusive pattern. This type of screen has very fine features allowing for high resolution. The screens can be engineered to have different viewing angles in the vertical and horizontal directions. Since the patterns are random, there is no periodicity to create moiré patterns. Two advantages of SRD’s are high efficiency and a high degree of flexibility in defining viewing angles. Because of their efficiency, SRD’s can have very high gain, however, for good contrast control tinting is sometimes necessary, which negates some of brightness advantage.
Top of the range rear projection tv's use glass-beaded screens, and tinted surface relief diffusers as well as good old fashioned ground glass. I would have to say, IMO the only type of screen that someone can make that will be anywhere near a professional screen is ground glass (sand blasted glass is effectively just the same). Just buy some grinding paste and off you go with some 1500 grade W&D sandpaper, making sure that there is more relief in the centre of the screen if you suffer from very bad hot spotting, if hot spotting is not really a problem, grind the glass evenly all over. If you do use ground glass, you don't need a frsnell, as the ground glass is doing the necessory diffusing.
Hope this helps you all.
by glass beaded you mean like etched or sand blasted? I have done sand blasting on a car before and did not get one of the windows covered good and the glass got blasted along the edge. looked just like etched glass. if going with the grinding paste, what is it called and where do you get it? this post answers several questions I've had. the screens on the older type RPTV do not look good up close like the new HD screens do, not taking resolution into account. when sitting too close to the older type you see the vertical ridges in the screen. which way is the beaded side of the glass turned? toward the viewer or toward the projector?
Thanks,
David
Thanks,
David
Addition to my origional post above
******* Adition to origional post*********
I have just though of another alternative if you don't think you are up to making a ground glass screen. Go and buy some rear projection screen material, after all it is designed for this sort of aplication, it used to be used a lot for presentations before the days of video projectors, when 16mm film projectors were the order of the day. You can still get hold of this material easilly, and it is not that expensive. You could be quite clever and get the stuff that is 'sound transparent', this stuff is screen material which has millions of tiny holes in it so sound can travel through it with making the screen material move. Cinemas use sound transparent screens and mount speakers behind the screen. There would be two advantages of doing this:
1) you could mount some speakers behind the screen (just out of the light path) so the sound actually came from the picture, not just below.
2) but better still, it would be great because it would allow great air flow through the whole unit, e.g. hot air from the light source could esceape through the screen! Don't worry, this is not a personal theory, it was one advantage that makers of sound transparent screens used to market their goods on. So you could keep the unit cooler much more easilly.
Again Hope this helps.
******* Adition to origional post*********
I have just though of another alternative if you don't think you are up to making a ground glass screen. Go and buy some rear projection screen material, after all it is designed for this sort of aplication, it used to be used a lot for presentations before the days of video projectors, when 16mm film projectors were the order of the day. You can still get hold of this material easilly, and it is not that expensive. You could be quite clever and get the stuff that is 'sound transparent', this stuff is screen material which has millions of tiny holes in it so sound can travel through it with making the screen material move. Cinemas use sound transparent screens and mount speakers behind the screen. There would be two advantages of doing this:
1) you could mount some speakers behind the screen (just out of the light path) so the sound actually came from the picture, not just below.
2) but better still, it would be great because it would allow great air flow through the whole unit, e.g. hot air from the light source could esceape through the screen! Don't worry, this is not a personal theory, it was one advantage that makers of sound transparent screens used to market their goods on. So you could keep the unit cooler much more easilly.
Again Hope this helps.
Here is a link showing showing the theory of a rear projection tv, many elements are the same today,
http://www.californiahistoricalradio.com/photos10.html
dbc105, The glass beaded screens have very fine pieces of glass, I mean really fine, e.g. like the size of flour, glued onto a clear substrate, I'm affraid I don't know much about these screens as they are a new idea (well the idea is an old one, but it is only recentley that firms have started to make them) It is the same methods as was used on top of the range screens made back in the 1960's (i'm showing signes of age here!!) Where believe it or not Asbestos dust was epoxy glued onto a sheet, giving a very high quality screen, but I bet you can't get hold of these anywhere now, well, not here in the UK anyway!
As for sand blasting, you need to use really really fine sand, if it is not really really fine you start to get an etched effect. As for grinding glass, I call it grinding paste, as for where you get it, try in an automotive shop , it may be sold as engine cylinder grinding paste, or another alternative would be paint grinding paste which is designed to take the shine off paint. The best bet is to go along to an automotive shop and tell them what you want to do, and see if they have anything that will work. Once you have the paste you mix it into a liquid and using 1500 or 2000 or greater grit wet and dry sand paper you really just sand down the sheet of glass. Look on Google and do a search for people who have made their own 'ground glass focusing screens' for 'sheet film camers'. There are lots of sites out there as I have seen a few myself. If you just want to test to see if you want to go down the glass path just pick up an old pice of glass, any type, just a cheap pice and use usual wet and dry sand paper and just water, the screen wont be as good as glass ground with propper paste but it should give you a good idea of what is possible, though I do warn you, it takes a bit of practice to get right! - I say that from experience!
The ground part would be toward the projector so there is a nice flat pice of glass towards the viewer, the reason for this is it makes it easier to apply a good anti-reflective coating, I beleive it is actually really easy to make these anti-reflective coatings, I know people used to make them out of easilly avalable chemicals - does any one have any ideas here?
Sorry if I keep refering to the past like this, but it has been some years since I did any rear projection work - I used to do a lot with 16mm film projectors - back in the good old days as I like to call them.
I would guess what you are refering to is actually black plastic strips embeded in some screens, they were called double
lenticular screens with black stripes, the have one problem that they have insufficient resolution for new, higher definition pictures that people want. The black strips were a clever method and simple method I would say of reducing the effects of ambient light bouncing off the screen, they may have been other reasons for these strips bit I'm not sure what they were, if there were any.
I have noticed that people seem to be using shower curtains, I do not think this that this is a very good idea as the screen needs to diffuse the light, plastic shower curtains are very poor difusers, in fact most are not really true difusers at all, they just impair the transmission of the light through it, they don't diffuse it.
******
Another cheap alternative could be artists tracing paper, the good stuff, which almost has a shiny plastic feel to it, you can get this in large lengths and widths, but I have no idea where from. This stuff iinfact acts like a difuser, though not a very efficient one.
Again, hope this helps, keep the questions going, i'm facinated to see how good diy rear projection tvs made by people reading these forums really are, I would guess they shoul be surprisingly good, there is no reason why they should not be as good, in fact they should be much much better than projectors people are making out of old OHP's and Projection panels! As less light is required to project a good image in the short distances involved.
http://www.californiahistoricalradio.com/photos10.html
dbc105, The glass beaded screens have very fine pieces of glass, I mean really fine, e.g. like the size of flour, glued onto a clear substrate, I'm affraid I don't know much about these screens as they are a new idea (well the idea is an old one, but it is only recentley that firms have started to make them) It is the same methods as was used on top of the range screens made back in the 1960's (i'm showing signes of age here!!) Where believe it or not Asbestos dust was epoxy glued onto a sheet, giving a very high quality screen, but I bet you can't get hold of these anywhere now, well, not here in the UK anyway!
As for sand blasting, you need to use really really fine sand, if it is not really really fine you start to get an etched effect. As for grinding glass, I call it grinding paste, as for where you get it, try in an automotive shop , it may be sold as engine cylinder grinding paste, or another alternative would be paint grinding paste which is designed to take the shine off paint. The best bet is to go along to an automotive shop and tell them what you want to do, and see if they have anything that will work. Once you have the paste you mix it into a liquid and using 1500 or 2000 or greater grit wet and dry sand paper you really just sand down the sheet of glass. Look on Google and do a search for people who have made their own 'ground glass focusing screens' for 'sheet film camers'. There are lots of sites out there as I have seen a few myself. If you just want to test to see if you want to go down the glass path just pick up an old pice of glass, any type, just a cheap pice and use usual wet and dry sand paper and just water, the screen wont be as good as glass ground with propper paste but it should give you a good idea of what is possible, though I do warn you, it takes a bit of practice to get right! - I say that from experience!
The ground part would be toward the projector so there is a nice flat pice of glass towards the viewer, the reason for this is it makes it easier to apply a good anti-reflective coating, I beleive it is actually really easy to make these anti-reflective coatings, I know people used to make them out of easilly avalable chemicals - does any one have any ideas here?
Sorry if I keep refering to the past like this, but it has been some years since I did any rear projection work - I used to do a lot with 16mm film projectors - back in the good old days as I like to call them.
I would guess what you are refering to is actually black plastic strips embeded in some screens, they were called double
lenticular screens with black stripes, the have one problem that they have insufficient resolution for new, higher definition pictures that people want. The black strips were a clever method and simple method I would say of reducing the effects of ambient light bouncing off the screen, they may have been other reasons for these strips bit I'm not sure what they were, if there were any.
I have noticed that people seem to be using shower curtains, I do not think this that this is a very good idea as the screen needs to diffuse the light, plastic shower curtains are very poor difusers, in fact most are not really true difusers at all, they just impair the transmission of the light through it, they don't diffuse it.
******
Another cheap alternative could be artists tracing paper, the good stuff, which almost has a shiny plastic feel to it, you can get this in large lengths and widths, but I have no idea where from. This stuff iinfact acts like a difuser, though not a very efficient one.
Again, hope this helps, keep the questions going, i'm facinated to see how good diy rear projection tvs made by people reading these forums really are, I would guess they shoul be surprisingly good, there is no reason why they should not be as good, in fact they should be much much better than projectors people are making out of old OHP's and Projection panels! As less light is required to project a good image in the short distances involved.
Nice post JR, and yeah age is getting on me too lol though not quite as much as yourself lol, ok for a difuser u can actually buy the stuff, 3m make it and its the same thats use in the backlight of lcd's, i think the best thing to do is to send 3m an emal and ask for a sample pack, from memory they hand these out free, just try to make out your are some big firm willing to buy the product in your email.
Trev
Trev
Trev, I though the days of firms giving things out for free was long gone! It's nice to be wrong sometimes!!
What sort of material is this 3m diffuser, is it a sheet of plastic or is it a pice of film e.g. like an OHP transparency sheet? If it is a thick pice of plactic I would guess it would not work as it will diffuse the light too much, so the projected image may not look right at all. I would guess it may also have a colour in it so that only light of a certain wavelength get's through, as I would guess LCD's would be designed to look best with certain colours of light, what do you think? But if you can get a pice for free go for it, and report the results, as even if it were of no use as a screen it may be of interest to people trying to make an ultra bright backlight style projector. Really you want a very thin material to diffuse the light, so there is not too much light loss, or a thick piece of glass with a thin diffusing layer on one side, e.g. if one side of ground.
What sort of material is this 3m diffuser, is it a sheet of plastic or is it a pice of film e.g. like an OHP transparency sheet? If it is a thick pice of plactic I would guess it would not work as it will diffuse the light too much, so the projected image may not look right at all. I would guess it may also have a colour in it so that only light of a certain wavelength get's through, as I would guess LCD's would be designed to look best with certain colours of light, what do you think? But if you can get a pice for free go for it, and report the results, as even if it were of no use as a screen it may be of interest to people trying to make an ultra bright backlight style projector. Really you want a very thin material to diffuse the light, so there is not too much light loss, or a thick piece of glass with a thin diffusing layer on one side, e.g. if one side of ground.
JR
its a thin film buddy, 3m makes all different kinds of thin films, difusers, polarisers filters u name it, some are stick on and some are just a thin film, i have a pile of difuser here thats from ripped lcds so i dont need to get any to test but yeah its an option for those who dont have any, your right about the light colour too with lcds, the best colour range is 4000k to 6000k, most backlights in lcd's are actually 6000k now.
Trev
its a thin film buddy, 3m makes all different kinds of thin films, difusers, polarisers filters u name it, some are stick on and some are just a thin film, i have a pile of difuser here thats from ripped lcds so i dont need to get any to test but yeah its an option for those who dont have any, your right about the light colour too with lcds, the best colour range is 4000k to 6000k, most backlights in lcd's are actually 6000k now.
Trev
That 3m diffuser sounds good for people who don't want to bother with ground glass, could you post some pics of some results for people not familiar with diffusers to see so we can compare the quality to that of ground glass?
It would seem that 3m still make everything you can think off, many a time I've heard many storiesof people on the phone to them for hours trying to find out about a a single product as it took so long for people at 3m to search through their product litsts to find the info you want!
It's interesting that you should mention the colour range, I was wondering how people were tackling this problem. It used to be quite easy using film in most cases, all you had to do was photograph a colour sheet and the labs did the rest for you, and you got back a nice 'correct' looking positive print, with all the colour correction done for you. All you then had to make sure was that you were using the correct bulb in the projector.
What is everyone doing when it comes to light temperature, what light sources is everyone using, are people going down the OHP/Projection panel route mounted sideways in a case, projecting onto a screen or using other methods. I seem to remeber that OHP Projection panels only had SVideo and/or just RCA Video inputs, not RGB inputs. Are you all building simple circuits to convert SVIDEO/Video signals into RGB then correcting each colour level then recombining to SVideo again, so as to allow you to easilly compensate for incorrect colour values from OHP style lamps, or change contrast?
It would seem that 3m still make everything you can think off, many a time I've heard many storiesof people on the phone to them for hours trying to find out about a a single product as it took so long for people at 3m to search through their product litsts to find the info you want!
It's interesting that you should mention the colour range, I was wondering how people were tackling this problem. It used to be quite easy using film in most cases, all you had to do was photograph a colour sheet and the labs did the rest for you, and you got back a nice 'correct' looking positive print, with all the colour correction done for you. All you then had to make sure was that you were using the correct bulb in the projector.
What is everyone doing when it comes to light temperature, what light sources is everyone using, are people going down the OHP/Projection panel route mounted sideways in a case, projecting onto a screen or using other methods. I seem to remeber that OHP Projection panels only had SVideo and/or just RCA Video inputs, not RGB inputs. Are you all building simple circuits to convert SVIDEO/Video signals into RGB then correcting each colour level then recombining to SVideo again, so as to allow you to easilly compensate for incorrect colour values from OHP style lamps, or change contrast?
JR most people in here use desktop lcd monitors, they are vga so the colouring of the actual lcd is acurate, the light we are using is metal halide, we are using the colour temp of 4200k - 6000k, im using 4200k now and its white enough for me, another isue i see is the colour of the screen its self, a yellow will yeald better skin tones and add abit more colour while it will also make some colours too dark, a white screen can be too white and make colours too light and tend to wash out the image, so its not just the lcd, light source and filters colour we have to worry about but also the screen, thats where it starts to get technical, i do have some of that diffuser here as im making a front projector right now and not a rear projectiion tv i dont have any shots nor can test in a rear veiw kind of way right now, but ill take a pic of the difuser for you and hold it upto my crt if you'd like.
Trev
Wow glad I tripped into here!!! Awesome feedback... IM into making a 3 wall cave for gaming, most of you have probable seen!
So I need rear screen material but I don't want it to be COSTLY... I did also hear about the OPaque curtain but then somone told me that's not gonna have enough light...
My projectors are NEC VT440 & 2 LT155, 1,100 lumens and 1,500
What and where to buy and how much is what I want to know?
The size I'd like to acheive is 6x8 for each wall... Give or take when everything is set... I have a rear screen 20x30 from Dalite which cost $110 which does look nice.. Im sure getting anthing bigger is gonna be way to much...
Any Ideads Tnx Alot
Mike
So I need rear screen material but I don't want it to be COSTLY... I did also hear about the OPaque curtain but then somone told me that's not gonna have enough light...
My projectors are NEC VT440 & 2 LT155, 1,100 lumens and 1,500
What and where to buy and how much is what I want to know?
The size I'd like to acheive is 6x8 for each wall... Give or take when everything is set... I have a rear screen 20x30 from Dalite which cost $110 which does look nice.. Im sure getting anthing bigger is gonna be way to much...
Any Ideads Tnx Alot
Mike
You guys should certainly get awards for ingenuity. Sounds to me like you are getting a good projector/rear projection TV for a bargain price, good work, is all I can say!
As for a light source, metal halide is a good one, they last for ages, but watch out, most pump out a lot of UV, even if there are no marks on the glass of the bulb!
One thing does interest me though, you say that the screens are vga so the colouring of the actual lcd is accurate, I’m not arguing with you there, I’m sitting in front of a laptop screen now and it looks perfect, but when you shine a light source with a spectrum of light output with a relatively high variance around the stated value, e.g. a metal halide bulb, surely you then suffer subtractive filtering so the colour value will change when the light goes through the panel, e.g. basically do you get general colour casts . This is a common problem with Film projection. Or have I got over excited and put a physics lab coat on and have started to read too much into all of this?
As for screens, there are equations for working out what the best colour screen for different colour temperature values are, but I never paid much attention to them, they are probably on the internet somewhere, as when you got an answer, there was usually never any screen that exactly matched what you needed anyway. Though if you are dealing with Rear Projection, you thankfully don't need to worry about this.
.
Ground Glass
Here are some links I though might be usefull to anyone thinking of making a ground glass screen:
http://www.philsan.com/ground_glass.htm
http://rhoadescameras.bizland.com/Camera%20Creation/Ground%20Glass/ground_glass.htm
http://www.phototechmag.com/previous-articles/2003/mj-dokas/dokas.html
These pages are all writen by people making ground glass focusing plates for large format sheet film cameras, but they are exactley the same as for a rear projection tv.
Further to what David asked in an earlier post, aluminum oxide is a great grinding medium or failing that silicon carbide, but this is not as good as aluminum oxide, you should be able to get grinding compounds/pastes containing both of these from an automotive parts shop, or the internet somewhere.
Here are some links I though might be usefull to anyone thinking of making a ground glass screen:
http://www.philsan.com/ground_glass.htm
http://rhoadescameras.bizland.com/Camera%20Creation/Ground%20Glass/ground_glass.htm
http://www.phototechmag.com/previous-articles/2003/mj-dokas/dokas.html
These pages are all writen by people making ground glass focusing plates for large format sheet film cameras, but they are exactley the same as for a rear projection tv.
Further to what David asked in an earlier post, aluminum oxide is a great grinding medium or failing that silicon carbide, but this is not as good as aluminum oxide, you should be able to get grinding compounds/pastes containing both of these from an automotive parts shop, or the internet somewhere.
Yeah, you won't get a Dalite one of size 6x8 feet for under $3500 to $4000 USDs, but that is what quality costs, since the 1950's they have always produced great products.
As for alternatives, I would guess a pice of glass of size 6x8 would be very expensive too, plus dangrous. I'll give it some thought as to what you could use as an alternative.
yeah they do , they are suposed to be the one bulb that pumps out the most uv, the bulb i have has a uv stop in it wich filters out the uv, not all but atleast 50%, better then none, some use plexi glass as uv filters and some dont use anything, myself i use plexi in my design anyway and a fair amount of it to hold my frensels together, yep and its a optical grade too well it would want to be at 200euro's for half a sheet.
Trev
How does a euro relate the a US dollar? Who or what is Dalite? I have been in the basement looking at the Pioneer RPTV that I removed the back from. I am going to take some measurements this afternoon and remove the CRT lenses to see if these look like usable parts. I am worried about focal length. Do I have to host an image to post it here or will the forum host it? I guess what I mean to ask is how do I post a pic or drawing? ater I get the measurements I can post a drawing showing what confines I am looking at.
Thanks,
David
Thanks,
David
Another screen idea is to use those plastic sheets that cover flourescent light, the kind you see in schools and office buildings they come in alot of textures and they are cheap. You can also use a thin sheet of HDPE plastic, this plastic is used to make those flexiable cutting boards. You can get a sheet from www.usplastics.com
Got a question. Can a 75 watt MR16 light bulb put out 2200 lumens because I found that does and I dont think the specs on it were right. Most 75 watt bulbs put out about 900-1000 lumens and highest I have seen one go was 1200 lumens.
Got a question. Can a 75 watt MR16 light bulb put out 2200 lumens because I found that does and I dont think the specs on it were right. Most 75 watt bulbs put out about 900-1000 lumens and highest I have seen one go was 1200 lumens.
Good UV filter
You could use 'Low-E' insulated glass or any other insulated glass with an inert gas in the middle of two pains, as insualting glass will stop UV but better still it will also reduce the amount of IR hitting the LCD. Small pieces of Low-E glass, e.g. 10x10 inches, are not that expensive at all.
You could use 'Low-E' insulated glass or any other insulated glass with an inert gas in the middle of two pains, as insualting glass will stop UV but better still it will also reduce the amount of IR hitting the LCD. Small pieces of Low-E glass, e.g. 10x10 inches, are not that expensive at all.
David, Dalite, or rather 'DA-LITE' are one of the best manafactures of screens for projection applications, IMO the best. They are a German Firm, seem to remember they started back in the 1950's. They make wonderful rear projection screens as well, with lots of options.
Here is their web page:
http://www.da-lite.com
They make every sort of screen, they will also make one of a kind screens for you. But as with all good screens, they cost a lot of money. Most people don't realise that a good screen will cost much more than a good projector. You can easilly spend $10,000 + on a screen.
1 EUR = 1.23840 USD as of 2004.01.31 15:33:13 GMT,
or
1 USD = 0.807495 EUR
David, is there a chance of some pics of the inside of your Pioneer RPTV, as I would be interested to see what they are like inside these days, as i'm sure many other people would be!
jr, I will have to try to bring a camera home with me next weekend. I don't have one but I can borrow one at work. I have made a drawing with measurements that may help also, if I can get it posted. I removed the bracket that holds the lenses and the CRTs. I then removed the center CRT. There was water? between the CRT and the first lense. The first lense is in a sphere. Above that is an adjustable double lense. Of course there are 3 of these in a row. The size of the CRT screen is about 5" x 4". The screen on the TV is 40" wide by 30" tall. I would like to reuse these lenses if possible. They already have the correct focal length. If I can mount a lcd where the CRT was and have the light come up through it. I don't know about fresnels or the sphere shaped lense. If I can find someone I can borrow a camera from I will get some pics up sooner. Maybe this drawing will give an idea of what I have. I know the mirror angle is wrong and it is not in proportion but it will give you an idea.
Thanks,
David
Thanks,
David
An externally hosted image should be here but it was not working when we last tested it.
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