cold mirrors
Do a google search for "cold mirror" dichroic ,and you will find lots of general info. These would be wonderful for use in a projector: You bounce the light of it at 45 degrees (some are for 0 degrees), and >90% of the visible light we want gets reflected. >90% of the IR passes through! Almost magic!
You can also look up the counterpart "heat mirror", that reflects IR but passes most of the visible light. These are easier to use (just because of the physical geometry of the light path), but not quite as good: They cut out a bit more visible red than a cold mirror, and I have read that they wear out after a while.
I am not surprised to read that this gives you better contrast: The red range is 625 to 740 nm, which is a big difference in wavelength. If the filter cuts out some of the longer red, then you should get less chromatic aberration. In some work I did with CCD image sensors, I added IR cut filters and got MUCH sharper images. This is why most video cameras include IR cut filters.
I plan to use a heat mirror in my light engine, but I would LOVE to find a dichroic cold mirror spherical reflector. That would send about half of the IR right out the BACK of the light engine before it even gets to the condensor. I was thinking I would have to buy a high temperature PCV lens and get somebody to put the coating on it. That can't be cheap! Have you really found one we can buy at a reasonable price, Trev? please, please, please...
Do a google search for "cold mirror" dichroic ,and you will find lots of general info. These would be wonderful for use in a projector: You bounce the light of it at 45 degrees (some are for 0 degrees), and >90% of the visible light we want gets reflected. >90% of the IR passes through! Almost magic!
You can also look up the counterpart "heat mirror", that reflects IR but passes most of the visible light. These are easier to use (just because of the physical geometry of the light path), but not quite as good: They cut out a bit more visible red than a cold mirror, and I have read that they wear out after a while.
I am not surprised to read that this gives you better contrast: The red range is 625 to 740 nm, which is a big difference in wavelength. If the filter cuts out some of the longer red, then you should get less chromatic aberration. In some work I did with CCD image sensors, I added IR cut filters and got MUCH sharper images. This is why most video cameras include IR cut filters.
I plan to use a heat mirror in my light engine, but I would LOVE to find a dichroic cold mirror spherical reflector. That would send about half of the IR right out the BACK of the light engine before it even gets to the condensor. I was thinking I would have to buy a high temperature PCV lens and get somebody to put the coating on it. That can't be cheap! Have you really found one we can buy at a reasonable price, Trev? please, please, please...
Yeah your right, i first noticed the pixels being very sharp and bright, it certainly makes a big difference. I suspect it does cut out some of the longer red because whats meant to be black is black and not a blackish red, there is still a slight red tinge wich is very faint but i think thats obviously because we are only filtering the reflected light and not the light from the front of the bulb. So if i wer to use a cold mirror aswell the red would disapear.
The colours i noticed changed alot, red was a bright viabrant red, the green was the right shades of green and stood out much more where as before they wer abit dormant, and the blue was also clour corected and vibrant. Im using a 5100k colour bulb this way and with the reflected light being 300k up the reflected light becomes 5400k so realy its abit of a mix lol but half way there to perfect colouring. The backlight in the lcd is 5500k so its getting close to colour spec. After doing this i tried a 4200k colour bulb with a standard reflector and by all means i just cant turn back, the 4200k colour is just too low and makes things look dirty. To me making half of a decent image is having the right colours, it realy makes things come alive, things look real as they are meant to be rather then looking dirty and dull, a daylight scene looks like its day rather then it being over cast ect. Another thing that stood out changing to a dichoric reflector as i meanioned before was the contrast, colours blended well and stayed sharp but wearnt over powering where it wasnt meant to be, the blacks wer black and the only pixels that yealded light wer the ones that wer meant to, it realy makes a big difference.
Yeah thats right, a good example is web cams. Actually You can make them see through clothes if you only have a ir filter in lol ( with the right wave length ofcourse ), but we wont get into that.
I can prety much get you anything you want buddy, you got any specs for me? like focal of the reflector and its diameter? I got a few normal sphericals kicking around you could use one of those if your using a cold mirror and not too worried about your bulb life.
I can get you good condensers, the ones i use, they are temperd borosilicate optical glass with a strong dark green AR coating, (that makes a big diff within its self for a clear image). What size bulb are you planing on running and what type?
Trev🙂
reflectors
I am trying out a Ushio S250DD metal halide bulb first. I like the specs on this bulb:
5200 degrees K color temperature (lone_wolf84: closer to sunlight than most MH bulbs)
90 Color Rendering Index (lw84: 90/100 is much better than most MH bulbs 65/100)
And since it is an HPS replacement bulb, it is in a pretty small package. (So it can fit in a lot of existing HPS fixtures) The outer glass is a 46 mm diameter cylinder, and the arc length is 24 mm. Not quite the smallest sized bulb available, but very nice color.
It is rated to run 20000 lumens (at first, anyway 😀 ) with an average life of 15000 hours. If my projector needs a new bulb in only 7500 hours because of the reflector & hot mirror, that would be fine with me.
I picked a 250 Watt bulb because I plan to use an optical-grade front surface spherical reflector (lw84: effectively doubles the light output), and the geometry of my media room demands a 95" image from 14 feet. I am hoping the low magnification (lw84: 95/15 = 6.3 X) and good throughput of the LCD give me enough lumens on the screen. I can also go to a higher gain screen material if I need more light, since we will hardly ever have more than two people watching. (lw84: So we will be viewing the screen from directly in front.)
I am still thinking about the light path to the lower fresnel. I would like to get a cold mirror in there, but my 1:1 scale drawings seem to indicate that is not possible with a 220 mm fl lower fresnel and a 100 mm condensor. It looks like I could get a 10" diameter cold mirror in there if I use a 500 mm fl lower fresnel. Maybe a smaller condensor, or no condensor at all...
I have a 75 mm diameter 65 mm fl spherical reflector on order from jcb, but his store still shows that as backordered. (He also NEVER returns emails!) I planned to work out the light engine geometry to fit that reflector, since it looked like the best one I could find without paying $100s. (lw84: surplus or commodity parts can be a LOT cheaper than trying to order 1 of something from an industrial optics supplier)
But what I really would love to find is a reasonably-priced off-the-shelf drichroic spherical reflector. These would be so cool (pun intended) that I think somebody could make some money by getting a few hundred made and then selling them to the DIY projector community. Apparently lots of people are running 400 Watt bulbs with no reflector (or a bad reflector) and they are trying lots of things to keep excessive heat away from the LCD. They could pretty much just drop one of these into their current projector to get twice the light or half the heat.
I am trying out a Ushio S250DD metal halide bulb first. I like the specs on this bulb:
5200 degrees K color temperature (lone_wolf84: closer to sunlight than most MH bulbs)
90 Color Rendering Index (lw84: 90/100 is much better than most MH bulbs 65/100)
And since it is an HPS replacement bulb, it is in a pretty small package. (So it can fit in a lot of existing HPS fixtures) The outer glass is a 46 mm diameter cylinder, and the arc length is 24 mm. Not quite the smallest sized bulb available, but very nice color.
It is rated to run 20000 lumens (at first, anyway 😀 ) with an average life of 15000 hours. If my projector needs a new bulb in only 7500 hours because of the reflector & hot mirror, that would be fine with me.
I picked a 250 Watt bulb because I plan to use an optical-grade front surface spherical reflector (lw84: effectively doubles the light output), and the geometry of my media room demands a 95" image from 14 feet. I am hoping the low magnification (lw84: 95/15 = 6.3 X) and good throughput of the LCD give me enough lumens on the screen. I can also go to a higher gain screen material if I need more light, since we will hardly ever have more than two people watching. (lw84: So we will be viewing the screen from directly in front.)
I am still thinking about the light path to the lower fresnel. I would like to get a cold mirror in there, but my 1:1 scale drawings seem to indicate that is not possible with a 220 mm fl lower fresnel and a 100 mm condensor. It looks like I could get a 10" diameter cold mirror in there if I use a 500 mm fl lower fresnel. Maybe a smaller condensor, or no condensor at all...
I have a 75 mm diameter 65 mm fl spherical reflector on order from jcb, but his store still shows that as backordered. (He also NEVER returns emails!) I planned to work out the light engine geometry to fit that reflector, since it looked like the best one I could find without paying $100s. (lw84: surplus or commodity parts can be a LOT cheaper than trying to order 1 of something from an industrial optics supplier)
But what I really would love to find is a reasonably-priced off-the-shelf drichroic spherical reflector. These would be so cool (pun intended) that I think somebody could make some money by getting a few hundred made and then selling them to the DIY projector community. Apparently lots of people are running 400 Watt bulbs with no reflector (or a bad reflector) and they are trying lots of things to keep excessive heat away from the LCD. They could pretty much just drop one of these into their current projector to get twice the light or half the heat.
Heya Guy, one thing ill tell you and im sure you knows this, Dichoric are the most reflective reflectors we can buy, its the best surface made.
Darn why you get that bulb for? lol you should have gotten a HQI-TSD lamp, they have a built in uv filter, are 25mm in diameter, 165mm long, 20mm arc, 20000lm, 5100k, and with a 90cri, they are also 80-90lm per watt eficientcy. With this bulb we can capture more light and have a much tighter light engine thats more acurate and efficient.
About the reflector from jcb, thats not too good, he runs them at half focal or there abouts so the rays arent acurate and the focal is just too long, (the reason why they are run at half focal), you will loose light with it. However given that if it has an enhanced aluminium surface you will see the difference, i have one here thats not the same as his but has the enhanced alloysurface (50mm dia, enhanced aluminium surface, 50mm focal, 1/12 wave length) and ill tell ya right now, becarful, because those things burn holes in lcds. Mine nearly did with a 150w mh CDM-T bulb and a heap of cooling on the lcd.
You can get a decent dichoric reflector for yours BRAND NEW for about $50 in that diameter, but if you had of gotten the bulb i sujested up top, you could of gotten a smaller reflector that will give you a brighter image and possibly reflect more light for about $30.
The size of your cold mirror will depend on where you place it, the closer to the light the better for size, a 4inch should do it with those focals.
Trev🙂
Darn why you get that bulb for? lol you should have gotten a HQI-TSD lamp, they have a built in uv filter, are 25mm in diameter, 165mm long, 20mm arc, 20000lm, 5100k, and with a 90cri, they are also 80-90lm per watt eficientcy. With this bulb we can capture more light and have a much tighter light engine thats more acurate and efficient.
About the reflector from jcb, thats not too good, he runs them at half focal or there abouts so the rays arent acurate and the focal is just too long, (the reason why they are run at half focal), you will loose light with it. However given that if it has an enhanced aluminium surface you will see the difference, i have one here thats not the same as his but has the enhanced alloysurface (50mm dia, enhanced aluminium surface, 50mm focal, 1/12 wave length) and ill tell ya right now, becarful, because those things burn holes in lcds. Mine nearly did with a 150w mh CDM-T bulb and a heap of cooling on the lcd.
You can get a decent dichoric reflector for yours BRAND NEW for about $50 in that diameter, but if you had of gotten the bulb i sujested up top, you could of gotten a smaller reflector that will give you a brighter image and possibly reflect more light for about $30.
The size of your cold mirror will depend on where you place it, the closer to the light the better for size, a 4inch should do it with those focals.
Trev🙂
better bulb
Interesting... I'm not married to that Ushio bulb!
An HQI-TS form would be much easier to fit to a spherical reflector. And a smaller arc length would be nice, too. (Just a bit harder to use a double-ended bulb with a big parabolic or eliptical reflector, maybe. But those are just ideas for experiments.) But all of the HQI-TS bulbs I found seemed to be the older 4200 K 65 CRI formulation.
You said "5100k, and with a 90cri". Who makes that bulb? I would like to look at the spec sheet. I am always willing to try something better!
And who sells dichroic spherical reflectors for $30-$50?
Interesting... I'm not married to that Ushio bulb!
An HQI-TS form would be much easier to fit to a spherical reflector. And a smaller arc length would be nice, too. (Just a bit harder to use a double-ended bulb with a big parabolic or eliptical reflector, maybe. But those are just ideas for experiments.) But all of the HQI-TS bulbs I found seemed to be the older 4200 K 65 CRI formulation.
You said "5100k, and with a 90cri". Who makes that bulb? I would like to look at the spec sheet. I am always willing to try something better!
And who sells dichroic spherical reflectors for $30-$50?
Actually you can, im suprised no body has thought in how to do this yet, im holding it back for now (atleast until i try it first 🙂 ), same with the reflector link as its been proven in the past my links and designs are what some others like to profit on.
Osram, here is their spec sheet.
Trev🙂
Attachments
Any thoughts on these lamps?
Thanks, I have been poking around on the Osram site and never saw that bulb! Maybe it is newer than their website.
The little ceramic bulbs look nice, too. But I have not seen one above 150W.
What do you think about these bulbs:
http://www.ushio.com/technicalspecs/Emarc.pdf
They are DC short-arc MH bulbs designed for projection, among other applications. example:
270W 41 volts @6.7 Amps 5700 K 1.5 mm arc length 14000 lum
but only 2000 hour life. <== nothing is perfect!
They also have one of these in a dichroic eliptical reflector intended for driving an optical fiber, but from the geometry specs I think you could couple it to a 330 mm fl fresnel to light a 15" LCD panel. In this design, all the light would go through the reflector's 10 mm wide focal point before diverging to the fresnel, so it would be very easy to add a small cold mirror.
I don't see anybody selling these on the web with a google search. I will call up their sales office on Monday to ask for prices. Then maybe I will stop by and pick up one or both. They are only 17 miles from my office. 😀
Thanks, I have been poking around on the Osram site and never saw that bulb! Maybe it is newer than their website.
The little ceramic bulbs look nice, too. But I have not seen one above 150W.
What do you think about these bulbs:
http://www.ushio.com/technicalspecs/Emarc.pdf
They are DC short-arc MH bulbs designed for projection, among other applications. example:
270W 41 volts @6.7 Amps 5700 K 1.5 mm arc length 14000 lum
but only 2000 hour life. <== nothing is perfect!
They also have one of these in a dichroic eliptical reflector intended for driving an optical fiber, but from the geometry specs I think you could couple it to a 330 mm fl fresnel to light a 15" LCD panel. In this design, all the light would go through the reflector's 10 mm wide focal point before diverging to the fresnel, so it would be very easy to add a small cold mirror.
I don't see anybody selling these on the web with a google search. I will call up their sales office on Monday to ask for prices. Then maybe I will stop by and pick up one or both. They are only 17 miles from my office. 😀
They are a great system but then we are heading away from diy and the cost of those little things are as much as a normal projector bulb, as you can see they have the same/similar specs. If you go out and buy ones of those then you might aswell buy a projector wich kinda sux lol.
Prety much how this all started in here is because the replacement prices of a bulb was the problem and people try to do things on the cheap. I like to compare cars to projectors, you can go out and aford that sports car but the thing is running cost and repair costs will be the part you cant, its very similar to bought projectors as where we can aford the actual unit but we cant aford the bulbs, you get my drift? 😉 But either way the bulbs in that site you posted are great but just too darn exspensive.
Trev🙂
Prety much how this all started in here is because the replacement prices of a bulb was the problem and people try to do things on the cheap. I like to compare cars to projectors, you can go out and aford that sports car but the thing is running cost and repair costs will be the part you cant, its very similar to bought projectors as where we can aford the actual unit but we cant aford the bulbs, you get my drift? 😉 But either way the bulbs in that site you posted are great but just too darn exspensive.
Trev🙂
big elliptical reflector
>im suprised no body has thought in how to do this yet
Oh, I've thought about a lot of these sorts of things. If I just wanted a projector, then I would have bought an OHP panel on ebay and an OHP at a yard sale. But I'm more interested in learning about all the possibilities.
An elliptical reflector that is bigger than the LCD would be very cool! It could converge the light through the LCD panel, and right into the projection lens. No condensor, no fresnels!
I once made a 4 foot diameter parabolic reflector when I was a kid out of masonite, heavy paper, and aluminum foil. I might just try that again as a prototype, once I have a lamp and get my panel running again.
>im suprised no body has thought in how to do this yet
Oh, I've thought about a lot of these sorts of things. If I just wanted a projector, then I would have bought an OHP panel on ebay and an OHP at a yard sale. But I'm more interested in learning about all the possibilities.
An elliptical reflector that is bigger than the LCD would be very cool! It could converge the light through the LCD panel, and right into the projection lens. No condensor, no fresnels!
I once made a 4 foot diameter parabolic reflector when I was a kid out of masonite, heavy paper, and aluminum foil. I might just try that again as a prototype, once I have a lamp and get my panel running again.
Im the same mate, i try to get the best out of somthing lol or try to improve on an aspect in a design ect, isnt life boring just buying stuff and not learning?
Possibly, not saying that it wont work cos it will just how well is the question as the light wont be going through the lcd paralelle.
I do alot of sheet metal work and ive made a few🙂 , but its just one of those things where as its just as easy and cheap to buy one, acuracy is always questionable aswell, ive got few light engines that ive made in the past that basically recycles light, ive made others aswell that are basically just a big reflector that houses the actual normal light engine to capture the lost light. At the end of the day with the wide range of optics and projectors, we have unlimited possibilities, having this technology available to comsumers now days also helps.
Trev🙂
Osram HQI-TS 250W/D
Anyone knows if this bulb is available in the US? Or of any other places that can be ordered from ..online ?
ace3000_1 said:
Anyone knows if this bulb is available in the US? Or of any other places that can be ordered from ..online ?
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