Ok, I have a question for some of the more technically knowledgeable folks on the board. I am having a serious heat issue on the LCD Surface from light intensity. I am using a 5" LCD so I am focusing alot of light onto the LCD. I also am experementing with several different light sources for my projector.
Within a few seconds My LCD is blackening, which tells me the temps are way to high. In doing some research I have found that most of the heat comes from the IR (Longwave) Light spectrum. I also know that UV is very bad for the LCD's life expectancy.
So...I have set out on a quest to design a cheap multi filter that both blocks the IR rays to keep me running cool as well as the UV rays to keep my LCD running for a long time.
I found out about the UV blocking ability of XL10 lexan from ace, Hillbilly and Guy on here. So I began to do a little more research on Low-E and Various other coated materials designed to block various different types of light. I found quite a bit of techincal information.
What I belelive I have been able to decifer is that coated material designed to block UV is directional in that it is desined to block UV rays and alow the rest of the spectrum in. However by reversing the mediam the other way will allow more UV to pass and block more longwave or IR. I beleive this is the reason why you can reverse some windows in the summer verses the winter. Maybe I am way off , someone enlighten me.
So off to home depot I went and I purchased a sheet of XL10 at lunch today....As I was sitting here I thought about another issue and that is how to deal with the heat being absorbed and reflected by the lexan. I will explain as I go along.
So my plan is to take the lexan and cut two pieces of equal size and have the side that is supposed to face outside (towards the sun) and face them together in the middle. I also was thinking that I may be able to dissipate some of the heat by placing a piece of glass against the side reflecting the IR. Here is a diagram
Total cost was $11.50 or so. What are the guru's thoughts on this? I will do some testing this weekend.
Within a few seconds My LCD is blackening, which tells me the temps are way to high. In doing some research I have found that most of the heat comes from the IR (Longwave) Light spectrum. I also know that UV is very bad for the LCD's life expectancy.
So...I have set out on a quest to design a cheap multi filter that both blocks the IR rays to keep me running cool as well as the UV rays to keep my LCD running for a long time.
I found out about the UV blocking ability of XL10 lexan from ace, Hillbilly and Guy on here. So I began to do a little more research on Low-E and Various other coated materials designed to block various different types of light. I found quite a bit of techincal information.
What I belelive I have been able to decifer is that coated material designed to block UV is directional in that it is desined to block UV rays and alow the rest of the spectrum in. However by reversing the mediam the other way will allow more UV to pass and block more longwave or IR. I beleive this is the reason why you can reverse some windows in the summer verses the winter. Maybe I am way off , someone enlighten me.
So off to home depot I went and I purchased a sheet of XL10 at lunch today....As I was sitting here I thought about another issue and that is how to deal with the heat being absorbed and reflected by the lexan. I will explain as I go along.
So my plan is to take the lexan and cut two pieces of equal size and have the side that is supposed to face outside (towards the sun) and face them together in the middle. I also was thinking that I may be able to dissipate some of the heat by placing a piece of glass against the side reflecting the IR. Here is a diagram
An externally hosted image should be here but it was not working when we last tested it.
Total cost was $11.50 or so. What are the guru's thoughts on this? I will do some testing this weekend.
hey that looks like a good idea. Im going to try that
i think you picture may be backwards.
i thoght the green coated side blocked the uv
i think you picture may be backwards.
i thoght the green coated side blocked the uv
Re
Re beackwards, Maybe I should have used a different color by coatd side I meant the side that has te uve protection not the green film...sorry about that.
So Tested it last night. There was a reduction of heat but not much at all. I magine it did take care of the UV but not the IR and heat so much. I compared it to a real UV/IR filter and IR is still a problem with this set up...so back to the drawing board...lol.
Re beackwards, Maybe I should have used a different color by coatd side I meant the side that has te uve protection not the green film...sorry about that.
So Tested it last night. There was a reduction of heat but not much at all. I magine it did take care of the UV but not the IR and heat so much. I compared it to a real UV/IR filter and IR is still a problem with this set up...so back to the drawing board...lol.
harmful IR?
It's UV light that will damage the LCD color filters over time. The IR light just heats it up, because the panel will absorb most of the IR hitting it. I don't think long wave IR (AKA far IR, AKA heat) is absorbed any differently than short wave IR (AKA near IR). If you try to use low-E glass as your only heat control measure, a lot of short wave IR will get through to heat up the LCD. That's why people are paying the big bucks for hot mirrors & cold mirrors: They seperate the visible light from almost all of the IR.
It's UV light that will damage the LCD color filters over time. The IR light just heats it up, because the panel will absorb most of the IR hitting it. I don't think long wave IR (AKA far IR, AKA heat) is absorbed any differently than short wave IR (AKA near IR). If you try to use low-E glass as your only heat control measure, a lot of short wave IR will get through to heat up the LCD. That's why people are paying the big bucks for hot mirrors & cold mirrors: They seperate the visible light from almost all of the IR.
Guy,
In your set-up, how much light do you think is lost when you put the ir filter that you bought from diybuilder? Does image color became lighter?
Do you think its really better to use a cold mirror than ir filter whic is installed perpendicular to light path?
Will you not lose some light using cold mirror and not affect the color also?
this kind of filter and mirror is scarce here. I can only test the brightness loss and color impact using a thin 2mm ordinary glass to reduce heating up of lcd.
regards,
hertz
In your set-up, how much light do you think is lost when you put the ir filter that you bought from diybuilder? Does image color became lighter?
Do you think its really better to use a cold mirror than ir filter whic is installed perpendicular to light path?
Will you not lose some light using cold mirror and not affect the color also?
this kind of filter and mirror is scarce here. I can only test the brightness loss and color impact using a thin 2mm ordinary glass to reduce heating up of lcd.
regards,
hertz
hot mirror & light loss
The spectrum plots I have seen for the most expensive hot mirrors show about a 10% loss of visible light. That is not much more than you would lose going through a sheet of ordinary glass. I have no such specs for the DIYBuilderGroup hot mirrors, but I am using only a 250 Watt MH lamp and my screen image seems very bright to me. I think the light does get a bit bluer, since the hot mirror reflects some of the longer wavelength red visible light. This would make the color temperate a bit higher. It looks fine to me!
A cold mirror would have the same effects: Some visible light lost, a bit less red in the output. I started with a cold mirror, but I could not fit it into the light path between my lamp and my 15" LCD. Even with a 330 mm condensor fresnel, it would take a very large cold mirror. (Try drawing a picture of it and you'll see what I mean.) The hot mirror can be run at 0 degrees, so it is very easy to get into the light path right at the lamp. One big advantage of using an elliptical reflector would be that you can fit a cold mirror at the second focal point.
Dichroic glass mirrors are expensive and hard to find everywhere! If you look at mainstream optical manufacturer's websites, they cost hundreds of dollars for very small pieces. The useful ones I have seen are surplusshed.com's $5 cold mirrors, DIYBuilder's hot mirrors, and maybe the 48 Euro www.exclusiv-online.com filter. All the rest are way too expensive or just ineffective low-E glass.
There are alternatives: Water is an excellant absorber of IR while passing most of the visible light. You can build a little water-tight "aquarium" with two sheets of ordinary glass held 1 cm apart. I made one with lexan & polyester resin (surfboard & boat resin). It can't be totally sealed, because the water will expand when it gets hotter, so you need to have at least one fitting for an expansion pipe to an overflow reservoir. If you have two fittings, then you could let water circulate through and go to an external heat exchanger. A ground fault interrupter would be a good idea if anybody tries making one of these, so you don't electrocute anybody if it leaks!
The spectrum plots I have seen for the most expensive hot mirrors show about a 10% loss of visible light. That is not much more than you would lose going through a sheet of ordinary glass. I have no such specs for the DIYBuilderGroup hot mirrors, but I am using only a 250 Watt MH lamp and my screen image seems very bright to me. I think the light does get a bit bluer, since the hot mirror reflects some of the longer wavelength red visible light. This would make the color temperate a bit higher. It looks fine to me!
A cold mirror would have the same effects: Some visible light lost, a bit less red in the output. I started with a cold mirror, but I could not fit it into the light path between my lamp and my 15" LCD. Even with a 330 mm condensor fresnel, it would take a very large cold mirror. (Try drawing a picture of it and you'll see what I mean.) The hot mirror can be run at 0 degrees, so it is very easy to get into the light path right at the lamp. One big advantage of using an elliptical reflector would be that you can fit a cold mirror at the second focal point.
Dichroic glass mirrors are expensive and hard to find everywhere! If you look at mainstream optical manufacturer's websites, they cost hundreds of dollars for very small pieces. The useful ones I have seen are surplusshed.com's $5 cold mirrors, DIYBuilder's hot mirrors, and maybe the 48 Euro www.exclusiv-online.com filter. All the rest are way too expensive or just ineffective low-E glass.
There are alternatives: Water is an excellant absorber of IR while passing most of the visible light. You can build a little water-tight "aquarium" with two sheets of ordinary glass held 1 cm apart. I made one with lexan & polyester resin (surfboard & boat resin). It can't be totally sealed, because the water will expand when it gets hotter, so you need to have at least one fitting for an expansion pipe to an overflow reservoir. If you have two fittings, then you could let water circulate through and go to an external heat exchanger. A ground fault interrupter would be a good idea if anybody tries making one of these, so you don't electrocute anybody if it leaks!
Guy,
Thanks for that information. My other reason why i want to use ir filter other than heat reduction is improvement of color of image and i guess it will somewhat improve a bit the contrast also.
regards,
PS. attched image is from MIB2-superbit copy. Its the dvd copy i've seen better than 5th element.
hertz
Thanks for that information. My other reason why i want to use ir filter other than heat reduction is improvement of color of image and i guess it will somewhat improve a bit the contrast also.
regards,
PS. attched image is from MIB2-superbit copy. Its the dvd copy i've seen better than 5th element.
hertz
Attachments
As far as heat (ir) and uv, I just replaced my shattered low e glass. (it literally exploded due to heat) with Neoceram.
After doing research I was going to try pyroceram glass, but it was too yellow (not letting a full range of white light through, but I found that for 3 bucks more neoceram did both blocked uv and ir plus let a broad range of white light through and is resistant to 1100 deg f temp. (over kill)
After doing research I was going to try pyroceram glass, but it was too yellow (not letting a full range of white light through, but I found that for 3 bucks more neoceram did both blocked uv and ir plus let a broad range of white light through and is resistant to 1100 deg f temp. (over kill)
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