Long time viewer, first time poster.
All parts ordered to build my first projector, Light engine from Izzotek.com and lense/fresnel's from Alan (DIYLABS). Already stripped 15" LCD panel and mounted in aluminium frame. I will setup a test-bench before actually building the box (want to make it as small as possible). Here is my question.
Is it an option to fold the light between the bulbs condensor and the first fresnel using a mirror. My thinking is to use a cold mirror which as you all know will reflect light and pass through heat. Has any one actually tried this. I have trawled through the posts and have found suggestions on doing this but no one has actually admitted to doing it.
BTW: LCD used is a HP 1530, strips incredibly easy with no flexi-cables to worry about and has VGA and DVI input. Contrast is 400:1, not sure of response time, will post when I confirm.
All parts ordered to build my first projector, Light engine from Izzotek.com and lense/fresnel's from Alan (DIYLABS). Already stripped 15" LCD panel and mounted in aluminium frame. I will setup a test-bench before actually building the box (want to make it as small as possible). Here is my question.
Is it an option to fold the light between the bulbs condensor and the first fresnel using a mirror. My thinking is to use a cold mirror which as you all know will reflect light and pass through heat. Has any one actually tried this. I have trawled through the posts and have found suggestions on doing this but no one has actually admitted to doing it.
BTW: LCD used is a HP 1530, strips incredibly easy with no flexi-cables to worry about and has VGA and DVI input. Contrast is 400:1, not sure of response time, will post when I confirm.
Hello
Here is the link for site where is posted one such project.
It is under T1000 and T800. This is translated with google:
http://translate.google.com/transla...&hl=en&ie=UTF-8&oe=UTF-8&prev=/language_tools
This guy that built T1000 design also sells FFC cables.
Original is in french if you prefer it:
http://www.allinbox.com
look under "projects allinbox"
Hope it helps.
There is a LOT of projects 15" and 7" diagonal with results that will be of interest to all of you if you did not see this page already.
Bye
Here is the link for site where is posted one such project.
It is under T1000 and T800. This is translated with google:
http://translate.google.com/transla...&hl=en&ie=UTF-8&oe=UTF-8&prev=/language_tools
This guy that built T1000 design also sells FFC cables.
Original is in french if you prefer it:
http://www.allinbox.com
look under "projects allinbox"
Hope it helps.
There is a LOT of projects 15" and 7" diagonal with results that will be of interest to all of you if you did not see this page already.
Bye
What Kodsnoba said hehe...pitty the allinbox site is in French some great looking PJ's there... Along with the T1000 and T800 designs there is also http://allinbox.com/hakkukakt3/hakkukakt.htm this fella used a 10.5" panel and a cold mirror, his design is reasonably compact for the size of the LCD, he has even mounted the 'guts' of his computer in the projector lol
I don't imagine that it matters whether you use a mirror after or before your condensor. You have to think about your distances/focal lengths to work out if its practical. I think most condensors are mounted about 1" away from the bulb so having the mirror after it would make sense.
Fitting in a cold mirror
I have been making some full-scale drawings of the light path from an HQI arc or a condensor, to the fresnel at a 15" panel. Then I try to position a small cold mirror in that path, so all the light makes it to the fresnel.
It looks like it is easier without the condensor lens, but still requires a very large cold mirror if you are using a 220 mm fl lower fresnel. It also looks like you can use a smaller cold mirror (ie. 4.75 inch diameter) if you use a 330 mm fl fresnel instead.
Hot mirror that performs well enough from 0 to 45 degrees, should be a lot easier to use: It can be placed perpendicular to the central ray, since the heat reflection can just bounce straight back toward the lamp. (Most of it will miss the lamp because of the angles.) I think I can cover the light field between a 1" long arc and a 220 mm fl fresnel on a 15" panel, with a piece of hot mirror that is about 3" diagonal. Just maybe a single 50 mm by 55 mm piece will do.
Another idea: Use a large elliptical reflector to focus the light to a small point. The reflector has to be large enough to create a cone of light that diverges from that second focal point to fill the lower fresnel. (Hint: make a drawing!) The narrow light path around the second focal point gives you a chance to fit in small hot or cold mirrors.
I have been making some full-scale drawings of the light path from an HQI arc or a condensor, to the fresnel at a 15" panel. Then I try to position a small cold mirror in that path, so all the light makes it to the fresnel.
It looks like it is easier without the condensor lens, but still requires a very large cold mirror if you are using a 220 mm fl lower fresnel. It also looks like you can use a smaller cold mirror (ie. 4.75 inch diameter) if you use a 330 mm fl fresnel instead.
Hot mirror that performs well enough from 0 to 45 degrees, should be a lot easier to use: It can be placed perpendicular to the central ray, since the heat reflection can just bounce straight back toward the lamp. (Most of it will miss the lamp because of the angles.) I think I can cover the light field between a 1" long arc and a 220 mm fl fresnel on a 15" panel, with a piece of hot mirror that is about 3" diagonal. Just maybe a single 50 mm by 55 mm piece will do.
Another idea: Use a large elliptical reflector to focus the light to a small point. The reflector has to be large enough to create a cone of light that diverges from that second focal point to fill the lower fresnel. (Hint: make a drawing!) The narrow light path around the second focal point gives you a chance to fit in small hot or cold mirrors.
Thanks for the response
Thanks for the replies, I checked out the sites that were recommended, makes more sense now.
As another note, I did post an earlier thread couple of days ago, but not seen it yet, probably got lost.
For everyones info, the LCD I am using is a Compaq HP 1530, this is a current product line and so the price will only getter lower, here's the specs;
Contrast: 400:1
Resposnse time: 23ms
Inputs: RGB & DVI
It strips very easily, no flexi cables to worry about - nice screen.
Hope this helps.
Once again, thanks for the replies. Going to start on my projector this week, I'm sure I'll be posting more questions.
Thanks for the replies, I checked out the sites that were recommended, makes more sense now.
As another note, I did post an earlier thread couple of days ago, but not seen it yet, probably got lost.
For everyones info, the LCD I am using is a Compaq HP 1530, this is a current product line and so the price will only getter lower, here's the specs;
Contrast: 400:1
Resposnse time: 23ms
Inputs: RGB & DVI
It strips very easily, no flexi cables to worry about - nice screen.
Hope this helps.
Once again, thanks for the replies. Going to start on my projector this week, I'm sure I'll be posting more questions.
Not at all, cos you are condenseing the light into a beam. The condenser has its own cone too and thats what you need to consider aswell as the bottom frensels cone. Dont go using a condenser thats any bigger then 80mm on a 250w setup as its abit too big for the lamp and you will get a large base cone, a large condenser also wont give us a very bright image compared to a smaller condenser as its condenseing the light in a beam that starts off far too wide.
Trev🙂
See drawing
It would be easy to fit a cold mirror in the path to a 7" LCD. It is very tight if you use a 220 mm fl lower fresnel and a 15" LCD. Look at the drawing. It is a pretty good approximation to scale, but you can draw your own to see just how tight it is. The lamp arc needs to be about 220 mm from the fresnel to get parallel rays heading into the LCD. The panel's corners are 7.5 " or 190.5 mm from the center. So the ray going from a point source to a panel corner would be pretty close to 45 degrees.
In the attached drawing, the lamp arc is at the left, the lower fresnel without a cold mirror is at the right, and the rays follow the path needed by the lower fresnel to light the corners of the panel. When we add the cold mirror (blue), the visible rays (red) get reflected down to the new fresnel + LCD position. Takes a pretty big cold mirror. I think a condensor would have to be a bit closer to the lower fresnel, so that would make the mirror space even smaller.
It gets a lot easier with smaller LCD panels or a longer focal length lower fresnel.
It would be easy to fit a cold mirror in the path to a 7" LCD. It is very tight if you use a 220 mm fl lower fresnel and a 15" LCD. Look at the drawing. It is a pretty good approximation to scale, but you can draw your own to see just how tight it is. The lamp arc needs to be about 220 mm from the fresnel to get parallel rays heading into the LCD. The panel's corners are 7.5 " or 190.5 mm from the center. So the ray going from a point source to a panel corner would be pretty close to 45 degrees.
In the attached drawing, the lamp arc is at the left, the lower fresnel without a cold mirror is at the right, and the rays follow the path needed by the lower fresnel to light the corners of the panel. When we add the cold mirror (blue), the visible rays (red) get reflected down to the new fresnel + LCD position. Takes a pretty big cold mirror. I think a condensor would have to be a bit closer to the lower fresnel, so that would make the mirror space even smaller.
It gets a lot easier with smaller LCD panels or a longer focal length lower fresnel.
Attachments
Re: See drawing
Well its gonna depend on the size of your condenser and its hight, power ect to determine just how far we can place the light from the cold mirror, its totally doable, what ever size this measures out to be is just physics, we cant change the laws involved of size to that degree. The only thing you could do as you mentioned is using an eliptical reflectior and unfortunatley they are big bux for a dichoric one, and not so easily found.
What happends if we dont use a condenser? we have the light from the bulb scatterd all over the place, and the image will be dull as, therefore we need the condenser to collect and focus the light into a concentrated beam, so we use the most of our light and not loose it. The more light that hits that cold mirror not only will our image become brighter, but the more light we will cool.
What it basically comes down to is: you get what you pay for, how much you want to pay and what is available at the time for what tech or way you choose to use, if you cant aford or find the parts then dont do it, its that simple, or change your lcd size to acomodate the parts you can aford.
Trev🙂
Guy Grotke said:
Well its gonna depend on the size of your condenser and its hight, power ect to determine just how far we can place the light from the cold mirror, its totally doable, what ever size this measures out to be is just physics, we cant change the laws involved of size to that degree. The only thing you could do as you mentioned is using an eliptical reflectior and unfortunatley they are big bux for a dichoric one, and not so easily found.
What happends if we dont use a condenser? we have the light from the bulb scatterd all over the place, and the image will be dull as, therefore we need the condenser to collect and focus the light into a concentrated beam, so we use the most of our light and not loose it. The more light that hits that cold mirror not only will our image become brighter, but the more light we will cool.
What it basically comes down to is: you get what you pay for, how much you want to pay and what is available at the time for what tech or way you choose to use, if you cant aford or find the parts then dont do it, its that simple, or change your lcd size to acomodate the parts you can aford.
Trev🙂
Hello Trev,
How well does your lens stand up to the heat? Or to put it another way. Would it be posible to place a 400w lamp this close to the lens?
DJ
Aslong as it can handle 300deg c no problem, so the correct glass used would be B270. If you cool the condenser its possible to run a lower grade glass, but its risky. Ive got a new condenser being custom made at the moment that will be all of my multi element light engine lenses designed into the one, the grade of glass on that will be B270, so we will see how it goes. I do have a lens here that has half the focal length of the lens that im getting made, and i tell ya, its made the 150w lamp brighter quite a fair bit then the 250w. If this is the case with the new condenser (which has even higher specs then my test lens, so it should be even brighter) i think i may stick with the 150w to save power and heat.
Hillbilly yeah thats what happends on a lower grade of glass with a lack of cooling on the condenser lol, the 250w isnt a very friendly bulb at the best of times.
Trev🙂
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