Here is a link for a discussion on lens, parabolic and elliptical reflectors.
www.oriel.com/down/pdf/01009.pdf
www.oriel.com/down/pdf/01009.pdf
Yeah, for a spherical mirror or lens, the focal length is half the radius of curvature. Anyways, does anyone expect a spherical mirror to produce a bad image quality? If not, I might have to start whipping one up. I'm starting to come over to the dark side of LCD projection, and giving up on laser projection... 🙄
re: laser projection
i talked to one of my friends who works in a conpany on hard drive development, and he knows a little about optics. He said that lasers are too intense for LCD panels. there are about 175000 lumens in the ray of a laser pointer....hehe. that is about ten times more then the projector bulb. he said that the good thing is that they do not give off heat, but on the other hand, your LCD panel will be demaged permanently in abour 3 minutes.
Aleksey
i talked to one of my friends who works in a conpany on hard drive development, and he knows a little about optics. He said that lasers are too intense for LCD panels. there are about 175000 lumens in the ray of a laser pointer....hehe. that is about ten times more then the projector bulb. he said that the good thing is that they do not give off heat, but on the other hand, your LCD panel will be demaged permanently in abour 3 minutes.
Aleksey
prjctr_builder, a laser projector wouldn't use a LCD panel. Check out the laser projector thread for more information.
Here's another site to play around with optical elements! It's a german site, but the buttons are easy to understand. You can drag several points to change parameters. To reset, click at the little red cross at the bottom of the animation.
http://members.aol.com/dustmannfw/gopt/optik.htm
Have fun!
xblocker
http://members.aol.com/dustmannfw/gopt/optik.htm
Have fun!
xblocker
I did a little more digging on Xterrian's Newtonian telescope idea and found a good site for amateur telescope building. Dan Cassaro will give you just about everthing you need to make a 16" parabolic mirror for $320. His kit includes the grinding tools needed and he will even do the initial rough grinding for you on a diamond grinding wheel. (This will save you about 10 hours on a 16" mirror.) You also get an 8" mirror blank to practice on.
It looks like the telescope idea can be cost competitive with the fresnel route. The only question is, will it work as well or better? One advantage of the telescope route is that there will be no chromatic or spherical aberration (since we do not use any lenses). However, I am still concerned about the possibility of blocking pixels with the secondary mirror. On a 15" XGA LCD, the pixels measure 1/3 mm x 1/3 mm. I think you would need a mirror smaller than this to make sure no pixels are blocked, but maybe I am missing something.
BTW, here is the link to Dan Cassaro's page for cheap 16" mirror blank kits:
http://home.attbi.com/~dcass/
CR
It looks like the telescope idea can be cost competitive with the fresnel route. The only question is, will it work as well or better? One advantage of the telescope route is that there will be no chromatic or spherical aberration (since we do not use any lenses). However, I am still concerned about the possibility of blocking pixels with the secondary mirror. On a 15" XGA LCD, the pixels measure 1/3 mm x 1/3 mm. I think you would need a mirror smaller than this to make sure no pixels are blocked, but maybe I am missing something.
BTW, here is the link to Dan Cassaro's page for cheap 16" mirror blank kits:
http://home.attbi.com/~dcass/
CR
My site
My Projector
This is a link to my site I got it up to date on what I have right now and will be adding as I get further along with the project.
My Projector
This is a link to my site I got it up to date on what I have right now and will be adding as I get further along with the project.
Whelp, had some time today, so, decided to give it another test for kicks. Eagerly awaiting my 400W Metal Halide! This test was in-line (I am not using an overhead projector-style setup.
What I used:
10,500 lumen Quartz Halogen double-ended bulb /w floodlight fixture (Hardware Store, $10.99)
10" x 12" Piece of Glass (Lowes, $1.96)
OHP Fresnel Lens (Scavenged, free)
Sharp QA-1750 ($125)
5 7/8" diam Plano-Convex Lens (Surplusshed, $13.50)
91 1/4" diagonal 16:9 Plas-Tex custom-built screen (Lowes, $55)
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The glass did a great job of cutting the heat. The last test I did, I just put the fresnel in front of the halogen. After about 10 minutes, the fresnel warped. It didn't melt, but, I'm sure if I had left it, it would have. This time, spacing the glass and fresnel about 1 inch apart with some spacers I made, I left the fresnel there for over 15 minutes with no noticable warping. sounds good to me, considering I havent even put the planned fans on it yet! my final plan will more than likely include 2 glass panes behind the fresnel. I imagine that the 400W Metal halide is going to produce much less heat than a 500W Quartz Halogen, also.
I was doing the test close to the wall, so, the image was only about 40" diagonal. It was clear, and, viewable, with a lot of ambient light (its a sunny day! shades all 3/4-pulled). Had my Dreamcast hooked up to it 🙂 This makes me feel VERY good about my metal halide that is coming. 4 times the brightness = good fun. Especially after I finish my reflector. in addition, the metal halide is actually going to have more of a point-light source than the long 500W halogen bulb does!
My end projector box is going to be about 16" wide, 14" tall, and about 3 feet in length.
What I used:
10,500 lumen Quartz Halogen double-ended bulb /w floodlight fixture (Hardware Store, $10.99)
10" x 12" Piece of Glass (Lowes, $1.96)
OHP Fresnel Lens (Scavenged, free)
Sharp QA-1750 ($125)
5 7/8" diam Plano-Convex Lens (Surplusshed, $13.50)
91 1/4" diagonal 16:9 Plas-Tex custom-built screen (Lowes, $55)
---
The glass did a great job of cutting the heat. The last test I did, I just put the fresnel in front of the halogen. After about 10 minutes, the fresnel warped. It didn't melt, but, I'm sure if I had left it, it would have. This time, spacing the glass and fresnel about 1 inch apart with some spacers I made, I left the fresnel there for over 15 minutes with no noticable warping. sounds good to me, considering I havent even put the planned fans on it yet! my final plan will more than likely include 2 glass panes behind the fresnel. I imagine that the 400W Metal halide is going to produce much less heat than a 500W Quartz Halogen, also.
I was doing the test close to the wall, so, the image was only about 40" diagonal. It was clear, and, viewable, with a lot of ambient light (its a sunny day! shades all 3/4-pulled). Had my Dreamcast hooked up to it 🙂 This makes me feel VERY good about my metal halide that is coming. 4 times the brightness = good fun. Especially after I finish my reflector. in addition, the metal halide is actually going to have more of a point-light source than the long 500W halogen bulb does!
My end projector box is going to be about 16" wide, 14" tall, and about 3 feet in length.
About the discussion on the spherical reflector
These two angles don't look equal at all
This is what it should look like
An externally hosted image should be here but it was not working when we last tested it.
These two angles don't look equal at all
This is what it should look like
An externally hosted image should be here but it was not working when we last tested it.
New screen
Well I just ordered a 6'X8' 1.5 gain screen for $210 should be here in a few weeks. Im so happy!!!!
Well I just ordered a 6'X8' 1.5 gain screen for $210 should be here in a few weeks. Im so happy!!!!
I talked to some Parabolic mirror gurus today and aparently the secondary mirror will block pixels. To do what I want to do I will need an off axis parabolic mirror. It does the same thing as a normal parabolic mirror except that the focal point is off axis and negates the need for a secondary mirror in the line of site. I will do complete plans prior to spending the first dollar. This will take some time, but I pal on building my projector for less than $100. I will just have to spend a lot of extra time to do it. I should just work two extra shifts and buy a regular lcd projector.
Xterrian:
I thought of this too, but I do not think we can easily make off-axis parabolic mirrors.
I am not going to give up on the Newtonian just yet. Since the light transmitted through the LCD is linearly polarized, we may be able to play a trick that makes use of a polarizing beam splitter and a wave plate to take care of those blocked pixels.
CR
I thought of this too, but I do not think we can easily make off-axis parabolic mirrors.
I am not going to give up on the Newtonian just yet. Since the light transmitted through the LCD is linearly polarized, we may be able to play a trick that makes use of a polarizing beam splitter and a wave plate to take care of those blocked pixels.
CR
Hi
Im interested into following in your footsteps and building a projector of a LCD powered by some white leds.
Could you please tell me some more about what kind of LCD you purchased, and what resolution it does?
A normal DVD is around 720x480 if I dont remember wrong, so I assume getting a LCD that can do that minimum is a good idea? Getting a LCD that can do even more would be nice, hi-res quake ye-haa 🙂 But as far as I have seen finding LCDs that are 5" and below that can do these resolutions are hard to find.
I admit Im quite a newbie, so any suggestions on where to start are more than welcome 🙂 For example, what more parts than the LEDs themselves should I get? Some board to solder them on I assume, any suggestion on where to get these and so on? 🙂
Thanks in advance.
Im interested into following in your footsteps and building a projector of a LCD powered by some white leds.
Could you please tell me some more about what kind of LCD you purchased, and what resolution it does?
A normal DVD is around 720x480 if I dont remember wrong, so I assume getting a LCD that can do that minimum is a good idea? Getting a LCD that can do even more would be nice, hi-res quake ye-haa 🙂 But as far as I have seen finding LCDs that are 5" and below that can do these resolutions are hard to find.
I admit Im quite a newbie, so any suggestions on where to start are more than welcome 🙂 For example, what more parts than the LEDs themselves should I get? Some board to solder them on I assume, any suggestion on where to get these and so on? 🙂
Thanks in advance.
malte:
You would probably need over 300 efficiently used super-bright white LEDs in order for it to be bright enough. 300 *$1.50 or so (average cost of a bright-white LED) = $450. Plus, 300 LEDs takes up a little too much room. Toss the idea out, we did.
Undream
You would probably need over 300 efficiently used super-bright white LEDs in order for it to be bright enough. 300 *$1.50 or so (average cost of a bright-white LED) = $450. Plus, 300 LEDs takes up a little too much room. Toss the idea out, we did.
Undream
I would not rule out the LEDs on cost alone just yet. Sure, it will be more expensive than HID lighting, but with LEDs, you will never have to replace them. It will also be much more energy efficient and cost less to use red, blue, and green LEDs than white ones, but then you have to do the color balance yourself. Another advantage of LEDs is that unlike HID lighting, the light from an LED is somewhat directional, and you only generate light in the visible (no UV or IR is ever generated), so they will not get as hot.
A friend of mine recently built an LED array for his research. He had 200 blue LEDs in the array, and let me tell you, it is very, very bright. He only knows the intensity (Watt/m^2), but if we can figure out how to convert from lumens to intensity we could do a direct comparison.
CR
A friend of mine recently built an LED array for his research. He had 200 blue LEDs in the array, and let me tell you, it is very, very bright. He only knows the intensity (Watt/m^2), but if we can figure out how to convert from lumens to intensity we could do a direct comparison.
CR
Thanks Chuck
Now I will have to read for many hours about beam splitters and polarization. It will probably be worth it if I can avoid using the off axis parabolic mirror though.
Now I will have to read for many hours about beam splitters and polarization. It will probably be worth it if I can avoid using the off axis parabolic mirror though.
Daily Dose of Tim
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In fact, you could make a good mirror really easily by taking an old satellite dish, stripping the paint off, and applying the mylar.
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Great Idea except my wife won't let me relocate that satellite dish into my living room! Gotta give you guys credit for thinking outside the box!!
Now about SERIOUS BUSINESS. You bastards better quit outbidding me on these LCD panels!! I'm just a poor Mississippi boy trying to put together a trailer trash video projector. I plan on using it to show pictures of my Pontiac Transmero soon as I get the new paint job! Right now, between the primer and the rust, it's sorta Salvidor Dali-ish. Gotta run.
http://www.drbukk.com/gmhom/park.html
Enjoy.
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In fact, you could make a good mirror really easily by taking an old satellite dish, stripping the paint off, and applying the mylar.
-------
Great Idea except my wife won't let me relocate that satellite dish into my living room! Gotta give you guys credit for thinking outside the box!!
Now about SERIOUS BUSINESS. You bastards better quit outbidding me on these LCD panels!! I'm just a poor Mississippi boy trying to put together a trailer trash video projector. I plan on using it to show pictures of my Pontiac Transmero soon as I get the new paint job! Right now, between the primer and the rust, it's sorta Salvidor Dali-ish. Gotta run.
http://www.drbukk.com/gmhom/park.html
Enjoy.
I'm setting a goal.
I'm going to *plan* a movie-party on the day of the Lord of the Rings: Fellowship of the Rings DVD is released on August 6. I will be done with my project, oh yes, I will.
Oh yeah! I forgot to tell you. The charges on my credit card for the ballast and bulb came through, and they only charged me $86.something! WOW. A brand new 400W Metal Halide Ballast and brand spankin new 400W 40,000 lumen bulb for $86. Man, did I get a deal. It should arrive at my door Wednesday!
I'm going to *plan* a movie-party on the day of the Lord of the Rings: Fellowship of the Rings DVD is released on August 6. I will be done with my project, oh yes, I will.
Oh yeah! I forgot to tell you. The charges on my credit card for the ballast and bulb came through, and they only charged me $86.something! WOW. A brand new 400W Metal Halide Ballast and brand spankin new 400W 40,000 lumen bulb for $86. Man, did I get a deal. It should arrive at my door Wednesday!
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