For video projection a 320 resolution would be enough. (a VCR does not output more than about 250 pixels) but for computer graphics it isn't enough.
I don't think Micro displays are an option because, altough optics in small sizes are easier and cheaper it will be more difficult to focus it correctly and to get enough light thrue the display without overheating it.
IMMO it's easier to use a (relative) large LCD and the optics used in an overhead projector. (Because of the large area at the base it's easy to cool and as everyone can see the optics of a overhead projector is not very high tech while still archiving good quality and brightness)
An overhead projector only uses 2 lenses and a mirror, for our application the mirror is not needed. (we can mirror the projection by turning the LCD) so we only need a bright light source, one fresnel lens (at least a big as your LCD) and one normal lens ( 150 ... 400 mm focal length depending on the size of your room and desired projection size)
I'm currently tring to locate (cheap) frensel lenses here in Spain to experiment. I'll keep you guys posted.
Robin
I don't think Micro displays are an option because, altough optics in small sizes are easier and cheaper it will be more difficult to focus it correctly and to get enough light thrue the display without overheating it.
IMMO it's easier to use a (relative) large LCD and the optics used in an overhead projector. (Because of the large area at the base it's easy to cool and as everyone can see the optics of a overhead projector is not very high tech while still archiving good quality and brightness)
An overhead projector only uses 2 lenses and a mirror, for our application the mirror is not needed. (we can mirror the projection by turning the LCD) so we only need a bright light source, one fresnel lens (at least a big as your LCD) and one normal lens ( 150 ... 400 mm focal length depending on the size of your room and desired projection size)
I'm currently tring to locate (cheap) frensel lenses here in Spain to experiment. I'll keep you guys posted.
Robin
I was reading the specs of a projector last night and several models used LCDS 8" and 10". The native resolution was 800x600 on the 10" screen. I'd like to use a larger LCD screen for better resolution, but I don't know how to fit the image of a 10" screen through a 3" diameter projection lense. There are 7" screens w/ 16:9 aspect ratio. That's excellent for home theater. I'm sure it can be done, but I don't know how.
I have a source here in the USA for new frensel lenses. They have various sizes. http://www.edmundoptics.com
I have seen frensel lenses on surplus sites too.
I have a source here in the USA for new frensel lenses. They have various sizes. http://www.edmundoptics.com
I have seen frensel lenses on surplus sites too.
Robin,
what you propose is exactly what i want to do, too.
Please let me know if you can find a supplier in Spain, or the general EU. I am in Germany, ordering from the US is no option right now given the strong dollar.
I am still very interested in this project and determined to do it but i have several audio projects with higher priority.
For the optics parts i was thinking of the spare parts supply of OHP manufacturers. I used to work at a hospital where we routinely got replacement parts from the manufacturers of the projectors. Should be no problem at least if you are some sort of company...
For the display i still play with the idea of using a regular 15" LCD screen like they are sold for computers. Remove the back wall and original backlight, put LED backlight in it and DONE.
Greetings
Timo
what you propose is exactly what i want to do, too.
Please let me know if you can find a supplier in Spain, or the general EU. I am in Germany, ordering from the US is no option right now given the strong dollar.
I am still very interested in this project and determined to do it but i have several audio projects with higher priority.
For the optics parts i was thinking of the spare parts supply of OHP manufacturers. I used to work at a hospital where we routinely got replacement parts from the manufacturers of the projectors. Should be no problem at least if you are some sort of company...
For the display i still play with the idea of using a regular 15" LCD screen like they are sold for computers. Remove the back wall and original backlight, put LED backlight in it and DONE.
Greetings
Timo
Quality
I used to do a lot of photography. What we always said was: You can't beat a bigger format. The reason for this was that lens quality was always a problem, and the larger film reduced lens effects. It also reduced film effects of course.
To corroborate: One of the sharpest production lenses ever made was Kodak Disc. It needed to be so sharp because the film was so small. Kodak realized their units produced terrible quality images and spent lots of money developing much improved films. The Japanese used the better film with a larger area and we all know the rest.
Why am I going on about this? I feel that a large LED (or other source) array, ideally direct view, but also projection must be better than passing a lot of light through (or reflecting off) a small area must be better.
I am very surprised that nobody has manufactured large direct-view diode screens.
Petter
I used to do a lot of photography. What we always said was: You can't beat a bigger format. The reason for this was that lens quality was always a problem, and the larger film reduced lens effects. It also reduced film effects of course.
To corroborate: One of the sharpest production lenses ever made was Kodak Disc. It needed to be so sharp because the film was so small. Kodak realized their units produced terrible quality images and spent lots of money developing much improved films. The Japanese used the better film with a larger area and we all know the rest.
Why am I going on about this? I feel that a large LED (or other source) array, ideally direct view, but also projection must be better than passing a lot of light through (or reflecting off) a small area must be better.
I am very surprised that nobody has manufactured large direct-view diode screens.
Petter
Petter,
there are direct-view RGB LED screens. The problem seems to be that the LED, each representing a pixel, are so big, hence you need a large distance from the screen.
Besides, you need 480000 (fourhundredeightythousand) LEDs for a 800x600 screen. I don't want to assemble that, or buy so many RGB LEDs, for that matter. Then you need analog control for the color of each led. Not my project.
Here's the Philips LED wall:
http://www.projektor-beamer.de/rueckprojektion/alfresco.htm
http://www.vidiwall.philips.com/press22.htm
this seems to have 5 normal LEDs instead of the RGB led.
Advantage: digital control of the LEDs ?
Thanks for your post, reinforces my decision to use a big screen and lense.
Regards
Timo
there are direct-view RGB LED screens. The problem seems to be that the LED, each representing a pixel, are so big, hence you need a large distance from the screen.
Besides, you need 480000 (fourhundredeightythousand) LEDs for a 800x600 screen. I don't want to assemble that, or buy so many RGB LEDs, for that matter. Then you need analog control for the color of each led. Not my project.
Here's the Philips LED wall:
http://www.projektor-beamer.de/rueckprojektion/alfresco.htm
http://www.vidiwall.philips.com/press22.htm
this seems to have 5 normal LEDs instead of the RGB led.
Advantage: digital control of the LEDs ?
Thanks for your post, reinforces my decision to use a big screen and lense.
Regards
Timo
You have a good point Petter. Bigger format is better. My brother shots color and black and white photography w/ a 120 format. The sharpness and color depth is where it's at.
There are very small RGB LEDs that this can be done with. But your distance would have to be at least 10' away from the screen. Also, one of the great challenges is contrast. How black can this get in other words. LEDs can be completely shut down. The best device is DLP. 800:1. Some of the best LCD screens only do 300:1 or 400:1 ratio.
But again, 300,000+ LEDs can draw alot of current @ 20mA each.
There are very small RGB LEDs that this can be done with. But your distance would have to be at least 10' away from the screen. Also, one of the great challenges is contrast. How black can this get in other words. LEDs can be completely shut down. The best device is DLP. 800:1. Some of the best LCD screens only do 300:1 or 400:1 ratio.
But again, 300,000+ LEDs can draw alot of current @ 20mA each.
Leds are not an option for a DIY screen for several reasons.
a) It's a hell of a job to just connect all these leds.
b) Too expensive: You need 64000 RGB leds for a 320X200 screen, 256000 for a 640X400 and 480000 RGB leds for a 800X600 screen. If you use serparate Red, Green & Blue leds instead of those expensive RGB leds you need 3 times these numbers.
c) You will have to make all electronics yourself for driving the leds (in matrix configuration) at a speed of almost 4 Mhz/LED.
I've played with the idea a long time but even a monocrome red (cheapest color) it's just not do-able.
To pull something of like this you need massive resources (like Philips, Sony).
The ONLY way to go is projection.
Robin
a) It's a hell of a job to just connect all these leds.
b) Too expensive: You need 64000 RGB leds for a 320X200 screen, 256000 for a 640X400 and 480000 RGB leds for a 800X600 screen. If you use serparate Red, Green & Blue leds instead of those expensive RGB leds you need 3 times these numbers.
c) You will have to make all electronics yourself for driving the leds (in matrix configuration) at a speed of almost 4 Mhz/LED.
I've played with the idea a long time but even a monocrome red (cheapest color) it's just not do-able.
To pull something of like this you need massive resources (like Philips, Sony).
The ONLY way to go is projection.
Robin
Timo,
The easiest thing would be to find a (old) overhead projector; They have all the optics we need. (Frensel lens ,projection lens) and they have the system to adjust the focus already made.
Many years ago at my school, I allready saw a (monocrome) LCD display on a normal overhead projector. It worked perfectly.
Robin
The easiest thing would be to find a (old) overhead projector; They have all the optics we need. (Frensel lens ,projection lens) and they have the system to adjust the focus already made.
Many years ago at my school, I allready saw a (monocrome) LCD display on a normal overhead projector. It worked perfectly.
Robin
You have to take into account that there is going to be some light bleeding into the room. Any extra light diminishes the image. This washes the image out. You should, somehow, block off any extra light around the LCD.
I want to add this for some visual help. It's a bite elementry, but optics is a tough subject.
http://www.opticalres.com/kidoptx.html#ControlLight
http://www.lighting-optics.com/technical_papers.htm#lenses
[Edited by vdi_nenna on 08-21-2001 at 09:46 AM]
I want to add this for some visual help. It's a bite elementry, but optics is a tough subject.
http://www.opticalres.com/kidoptx.html#ControlLight
http://www.lighting-optics.com/technical_papers.htm#lenses
[Edited by vdi_nenna on 08-21-2001 at 09:46 AM]
http://www.lighting-optics.com/pdf/tech_papers_june2001.pdf
This is an excellent source of info! It's all drawn out for you!
This is an excellent source of info! It's all drawn out for you!
Timo,
You could try the following address for Fresnel lenses (your German is a lot better than mine):
Fresnel Optics GmbH
Flurstedter Marktweg 13
Postfach 21-99510 Apolda
Thuringia, Germany
Tel: 49-3644-50110
Fax: 49-3644-501150
(Web: http://www.fresnel-optics.com )
Please let me know the results!!
Robin
You could try the following address for Fresnel lenses (your German is a lot better than mine):
Fresnel Optics GmbH
Flurstedter Marktweg 13
Postfach 21-99510 Apolda
Thuringia, Germany
Tel: 49-3644-50110
Fax: 49-3644-501150
(Web: http://www.fresnel-optics.com )
Please let me know the results!!
Robin
Robin,
nice find.
I wouldn't know what to ask them at this time.
What do you want to know?
They seem to speak English too and even have a US division:
Fresnel Optics
1300 Mt. Read Blvd.
Rochester, NY 14606
United States of America
Telephone: 716-647-1140
Facsimile: 716-254-4940
I think the idea of finding an old projector and recycle the fresnel lense and projection optics is a good one. I'll check the newspaper for old OHPs from now on.
Regards
Timo
nice find.
I wouldn't know what to ask them at this time.
What do you want to know?
They seem to speak English too and even have a US division:
Fresnel Optics
1300 Mt. Read Blvd.
Rochester, NY 14606
United States of America
Telephone: 716-647-1140
Facsimile: 716-254-4940
I think the idea of finding an old projector and recycle the fresnel lense and projection optics is a good one. I'll check the newspaper for old OHPs from now on.
Regards
Timo
Timo,
I don't want to call the US division as we would have to pay in (expensive) US $ again :-(
The questions I have are:
1) Are they willing to deliver fresnel lenses to individuals?
2) How much do overhead fresnel lenses costs? (at least 30X20 cm big)
3) How much do rear projection tv fresnel lenses costs? ( at least 100 X 75 cm, preferable bigger)
If those big lenses are cheap enough a rear projection tv would be a very simple but nice start. take a normal TV/monitor (for example those old Commodore Amiga 1084S monitors are perfect!) put it in a big box with a big fresnel lens in front. It's like looking to a magifying glass. ( a example of what I mean can be found here: http://www.rickleephoto.com/rlcoll.htm , only our result would be a BIG screen TV)
I found several sites that offer 40X30 inch (100X75 CM)lenses for around $ 100,-
If we are able to order them directly from a factory in europe they should be a lot cheaper. (After all it's only a sheet of plastic)
I looked yesterday on one of those online marketplaces but I only found overhead projectors for about DM 200,- or more. I also found a LCD screen to be used on overhead projectors but it was back and white.
Robin
I don't want to call the US division as we would have to pay in (expensive) US $ again :-(
The questions I have are:
1) Are they willing to deliver fresnel lenses to individuals?
2) How much do overhead fresnel lenses costs? (at least 30X20 cm big)
3) How much do rear projection tv fresnel lenses costs? ( at least 100 X 75 cm, preferable bigger)
If those big lenses are cheap enough a rear projection tv would be a very simple but nice start. take a normal TV/monitor (for example those old Commodore Amiga 1084S monitors are perfect!) put it in a big box with a big fresnel lens in front. It's like looking to a magifying glass. ( a example of what I mean can be found here: http://www.rickleephoto.com/rlcoll.htm , only our result would be a BIG screen TV)
I found several sites that offer 40X30 inch (100X75 CM)lenses for around $ 100,-
If we are able to order them directly from a factory in europe they should be a lot cheaper. (After all it's only a sheet of plastic)
I looked yesterday on one of those online marketplaces but I only found overhead projectors for about DM 200,- or more. I also found a LCD screen to be used on overhead projectors but it was back and white.
Robin
Big fresnel lens
Various sizes of fresnel lenses can be bought here:
http://www.lektropacks.co.uk/acatalog/Lektropacks_Online_Television_4.html
(I've never used them so can't comment on quality/service).
Regards,
DAve
Various sizes of fresnel lenses can be bought here:
http://www.lektropacks.co.uk/acatalog/Lektropacks_Online_Television_4.html
(I've never used them so can't comment on quality/service).
Regards,
DAve
<a href="http://www.sciplus.com/category.cfm?subsection=21&category=193">American Science and Surplus</a> has these:-
(These were originally designed to fit over a TV to magnify the picture, and most have their original ’70s packaging.) The focal length of the lenses is 20”. The small lens is 7–1/2” x 10” wide. The medium lens is 10” x 13-1/2” wide. <b><u>They’re slightly tinted</u></b>, but that doesn’t affect their performance.
32571 FRESNEL LENS, SMALL $9.50/EACH
32572 FRESNEL LENS, MEDIUM $12.50/EACH
<center>Regards
James</center>
(These were originally designed to fit over a TV to magnify the picture, and most have their original ’70s packaging.) The focal length of the lenses is 20”. The small lens is 7–1/2” x 10” wide. The medium lens is 10” x 13-1/2” wide. <b><u>They’re slightly tinted</u></b>, but that doesn’t affect their performance.
32571 FRESNEL LENS, SMALL $9.50/EACH
32572 FRESNEL LENS, MEDIUM $12.50/EACH
<center>Regards
James</center>
I keep hearing this exchange rate divide..
and being in the US, what the hell..
What should I take advantage of right now using my US bucks? What is a real steal if I am looking for big amp parts and sub drivers? Or hell, even new main speakers. Even if I have to buy it now and let it sit for a little bit. I have some friends in EU, so even purchase over there would not be a big problem if mail order was an issue.
Nothing lasts forever, so what should I take advantage of?
and being in the US, what the hell..
What should I take advantage of right now using my US bucks? What is a real steal if I am looking for big amp parts and sub drivers? Or hell, even new main speakers. Even if I have to buy it now and let it sit for a little bit. I have some friends in EU, so even purchase over there would not be a big problem if mail order was an issue.
Nothing lasts forever, so what should I take advantage of?
Robin,
i have asked the questions that you posted to the factory. Will let you know if they respond and what they have to say.
I don't want RPTV, but really a high quality projector with SVGA input. It must project a sharp image of at least 2x1.5m. I cannot fit a big RPTV in my room because there is a very big audio system standing in the way. One of the goals of this projector is to remove the PC/TV monitor+desk and replace it with a projector suspended on the ceiling.
Regards
Timo
i have asked the questions that you posted to the factory. Will let you know if they respond and what they have to say.
I don't want RPTV, but really a high quality projector with SVGA input. It must project a sharp image of at least 2x1.5m. I cannot fit a big RPTV in my room because there is a very big audio system standing in the way
. One of the goals of this projector is to remove the PC/TV monitor+desk and replace it with a projector suspended on the ceiling. Regards
Timo
Timo,
Thanks!
RPTV is not my first choice either, but the optics are so easy it can't go wrong.. (more or less..) If I can make a RPTV with decent quality i'm planning to cut a hole thrue the wall that separates my living room with the room that contains only my hot water boiler. Having only the 'screen' in the living room it would be like a plasma screen on the wall
I just placed a bid on http://www.ebay.co.uk to a overhead projector plus a 640X480 LCD panel (with VGA & video inputs), it's not SVGA but good enough for video projection; this is not a DIY solution but for the current bid price it's a nice all-in-one solution for me.
I wish I could finaly find just some of these cheap page-magnifier sheets (in fact fresnel lenses) to play with. (and no I don't mean thrue a online store; I'm not willing to pay $ 2,- for the sheet plus $20,- for P&P, just a shop here in Barcelona where I can thouch and look at the sheets.)
Robin
PS: For the person in the US wondering what you could buy with our strong $$$'s : Just look for something what you want to have and order it, just beware that electrical equipment runs as 220-240 Volts/50Hz here (although many things could be adjusted to 110V/60Hz) and our television standard is PAL not NTSC. I've been told that what 'import' cd's are cheap here.
[Edited by rjacobs on 08-23-2001 at 07:27 AM]
Thanks!
RPTV is not my first choice either, but the optics are so easy it can't go wrong.. (more or less..) If I can make a RPTV with decent quality i'm planning to cut a hole thrue the wall that separates my living room with the room that contains only my hot water boiler. Having only the 'screen' in the living room it would be like a plasma screen on the wall
I just placed a bid on http://www.ebay.co.uk to a overhead projector plus a 640X480 LCD panel (with VGA & video inputs), it's not SVGA but good enough for video projection; this is not a DIY solution but for the current bid price it's a nice all-in-one solution for me.
I wish I could finaly find just some of these cheap page-magnifier sheets (in fact fresnel lenses) to play with. (and no I don't mean thrue a online store; I'm not willing to pay $ 2,- for the sheet plus $20,- for P&P, just a shop here in Barcelona where I can thouch and look at the sheets.)
Robin
PS: For the person in the US wondering what you could buy with our strong $$$'s : Just look for something what you want to have and order it, just beware that electrical equipment runs as 220-240 Volts/50Hz here (although many things could be adjusted to 110V/60Hz) and our television standard is PAL not NTSC. I've been told that what 'import' cd's are cheap here.
[Edited by rjacobs on 08-23-2001 at 07:27 AM]
- Status
- Not open for further replies.