I'm just waiting to see what happens down at Rice univeristy with molecular computing.....that is some cool stuff that will eventually happen
xblocker said:
Now THAT would be incredible, if we could all get together and build a quantum computer.
Yep!
I could spend the power supply!
...i suppose we're getting a little offroad now...
xblocker
I could spend the power supply!
...i suppose we're getting a little offroad now...
xblocker
xblocker said:
true true 🙂 suppose for the person reading every page, this will be more of a relaxing point in the whole projector discussion 🙂
though discussing quantum mechanics isn't something one can read lightly...
Keyword: Relaxing point!
Was someone, who already has more or less finished his projector, able to lay back on the coach just to enjoy a movie or whatever, without looking on brightness, temperature, contrast, pixels...?
For me it's hard, although i now have 2 working systems!
xblocker
Was someone, who already has more or less finished his projector, able to lay back on the coach just to enjoy a movie or whatever, without looking on brightness, temperature, contrast, pixels...?
For me it's hard, although i now have 2 working systems!
xblocker
I recall....
Guys,
I recall someone posted a remark about using an s-video to vga converter cable to try to rid the macrovision effect...
I have been looking in to this and I have come across a website that is selling several different types of this...I may look into one of these just to see if they help an s-video signal. Any suggestions as to which one I should get? Moreover have you guys seen or heard anything about these?
Well here is the link...http://www.avtoolbox.com/video-to-vga.htm
Thanks...and eebasist do you have any idea of what material to use to rasie my panel? and what do you suggest is ample distance to raise it?
-Blackhead
Guys,
I recall someone posted a remark about using an s-video to vga converter cable to try to rid the macrovision effect...
I have been looking in to this and I have come across a website that is selling several different types of this...I may look into one of these just to see if they help an s-video signal. Any suggestions as to which one I should get? Moreover have you guys seen or heard anything about these?
Well here is the link...http://www.avtoolbox.com/video-to-vga.htm
Thanks...and eebasist do you have any idea of what material to use to rasie my panel? and what do you suggest is ample distance to raise it?
-Blackhead
Raising the NView Spectra
Somewhere in the plethora of posts, I have seen it mentioned that there is seldom any need to worry about these panels specifically designed for overhead projector use.
I have an NView Viewframe, which appears to be nearly identical to the Spectra C. It has a couple fans built in already to move air about, but I haven't gotten my overhead projector yet to try it out.
It is about to kill me because the OH projector is ALL I LACK before I can try out this panel in the mode it was intended. I know the panel is good because I hooked it up to my old 486 (with TV Tuner card) and I could see (holding up to light) the image. My wife is a school counselor and goes back to work in a couple weeks. I'm counting on her borrowing a projector for me to 'try out'.....
Enjoy.
Somewhere in the plethora of posts, I have seen it mentioned that there is seldom any need to worry about these panels specifically designed for overhead projector use.
I have an NView Viewframe, which appears to be nearly identical to the Spectra C. It has a couple fans built in already to move air about, but I haven't gotten my overhead projector yet to try it out.
It is about to kill me because the OH projector is ALL I LACK before I can try out this panel in the mode it was intended. I know the panel is good because I hooked it up to my old 486 (with TV Tuner card) and I could see (holding up to light) the image. My wife is a school counselor and goes back to work in a couple weeks. I'm counting on her borrowing a projector for me to 'try out'.....
Enjoy.
Re: I recall....
I bought one of
these from Amazon.com. It works fine up to 1024x768, and cured my Macrovision woes. Someone in the original thread had mentioned it. Less expensive than the equivalent ones on the page you refrenced too.
Blockhead said:
I bought one of
these from Amazon.com. It works fine up to 1024x768, and cured my Macrovision woes. Someone in the original thread had mentioned it. Less expensive than the equivalent ones on the page you refrenced too.
BLACKHEAD LOLOLOL I KILL MYSELF...
Oh I'm sorry guys I was reviewing some of the post and I glanced back at mine a few posts up and I noticed I put Blackhead instead of Blockhead...Jeez thank God it's Friday!
blOckhead
Oh I'm sorry guys I was reviewing some of the post and I glanced back at mine a few posts up and I noticed I put Blackhead instead of Blockhead...Jeez thank God it's Friday!
blOckhead
Heat, light and watts
Thanks Bill - Makes sense to me now! So, the total energy leaving both bulbs IS the same, but there's a lot more in the IR band leaving a halogen than MH, and a lot more in the visible spectrum leaving the MH than the halogen.
Thanks!
woneill said:
Thanks Bill - Makes sense to me now! So, the total energy leaving both bulbs IS the same, but there's a lot more in the IR band leaving a halogen than MH, and a lot more in the visible spectrum leaving the MH than the halogen.
Thanks!
I don't know if this has been mentioned before in this thread but you guys should consider making a little anamorphic lens for the DIY projector and placing the lens before the other lenses in the optical path. This will give an optical anamorphic compression without geometry problems. I hope this relates to the discussion here as I didn't read much of the thread.
The other DIY-projectors I've seen don't have the option to run anamorphic DVDs but with a lens that would be possible. The lens could slide in place for anamorphic material.
Just a quick idea. I'm in the optics forum, working on my anamorphic lens. 🙂
Tor Arne
The other DIY-projectors I've seen don't have the option to run anamorphic DVDs but with a lens that would be possible. The lens could slide in place for anamorphic material.
Just a quick idea. I'm in the optics forum, working on my anamorphic lens. 🙂
Tor Arne
Blockhead, i would say .25 inch....but depending on the quality of the OHP and panel....and within the limits of the focusing mechanism you could go higher....you could really use anything you had on had......wood, plastic....anything laying around to keep it flat...doing this will require you to make something to block out the light that escapes so you dont have it act as ambient light in the room
Hi Guys,
Does everybody here know what an anamorphic lens does?
Basically, many widescreen DVDs are encoded with "Anamorphic Widescreen". On a regular tv, this results in a picture identical to a normal widescreen DVD/VHS/Laserdisc: you get black bars at top and bottom of the picture.
However, what the anamorphic encoding does, is expand the image vertically within the 724x480 (US) image, so that the black bars are either reduced or removed. The end result is a very tall image stored using more of the resolution of the DVD.
If you have a normal tv, then your DVD player automatically compresses the image vertically to put the black bars in. But if your DVD player knows you have a widescreen tv/projector, then it does not do this, and leaves the image stretched vertically.
The anamorphic lenses allow you to convert your regular 4:3 panel so that it produces a widescreen image. This could be done by stretching the image horizontally, or compressing it vertically, or both. The end result is that you get to use more, if not all, of the pixels on your screen to contribute to the image.
A DVD disc is designed to accommodate stored images with different aspect ratios:
4:3 (normal)
16:9 (Widescreen)
2.35:1 (Cinemascope - not used)
When you see "Widescreen" on the label, the DVD is stored at 4:3 with the black bars encoded into the video signal. When you see "Anamorphic Widescreen" on the label, the video is encoded at 16:9, and there are only black bands encoded if the aspect ratio is wider than that (e.g. 2.35:1).
I was previously investigating the use of cylindrical lenses to get this effect, but it seems that prisms may be an alternative way to go...
Either way, if it works, it will beat the use of cardboard/sheet metal masks.
Bill.
Does everybody here know what an anamorphic lens does?
Basically, many widescreen DVDs are encoded with "Anamorphic Widescreen". On a regular tv, this results in a picture identical to a normal widescreen DVD/VHS/Laserdisc: you get black bars at top and bottom of the picture.
However, what the anamorphic encoding does, is expand the image vertically within the 724x480 (US) image, so that the black bars are either reduced or removed. The end result is a very tall image stored using more of the resolution of the DVD.
If you have a normal tv, then your DVD player automatically compresses the image vertically to put the black bars in. But if your DVD player knows you have a widescreen tv/projector, then it does not do this, and leaves the image stretched vertically.
The anamorphic lenses allow you to convert your regular 4:3 panel so that it produces a widescreen image. This could be done by stretching the image horizontally, or compressing it vertically, or both. The end result is that you get to use more, if not all, of the pixels on your screen to contribute to the image.
A DVD disc is designed to accommodate stored images with different aspect ratios:
4:3 (normal)
16:9 (Widescreen)
2.35:1 (Cinemascope - not used)
When you see "Widescreen" on the label, the DVD is stored at 4:3 with the black bars encoded into the video signal. When you see "Anamorphic Widescreen" on the label, the video is encoded at 16:9, and there are only black bands encoded if the aspect ratio is wider than that (e.g. 2.35:1).
I was previously investigating the use of cylindrical lenses to get this effect, but it seems that prisms may be an alternative way to go...
Either way, if it works, it will beat the use of cardboard/sheet metal masks.
Bill.
How big (small) would the lens have to be to fit inside a DIY-projector?
The main advantages with a lens is increaseed brightness, less screendoor, higher resolution and reduced LCD-artifacts (scan-lines).
If you use a PC to drive the projector then it would also be possible to make a second lens (or an adjustable one) for 2.35:1 and scale the picture on the PC so that the lens can compress it.
Tor Arne
The main advantages with a lens is increaseed brightness, less screendoor, higher resolution and reduced LCD-artifacts (scan-lines).
If you use a PC to drive the projector then it would also be possible to make a second lens (or an adjustable one) for 2.35:1 and scale the picture on the PC so that the lens can compress it.
Tor Arne
Orthogonal Parabolic Reflector
For anyone like me who wants to find out more about orthogonal parabolic reflectors, have a look at US patent #5,765,934.
(http://patft.uspto.gov/netahtml/search-bool.html)
They even have the curve formula in the description.
I had a thought about creating our own reflectors. If you've ever seen fiberglass tubs or the like being made, they start with a mold which gets the finish coat applied first, then the supporting layers laid and spayed on. Once it sets, it gets pulled off the mold, and the nice smooth finished surface is revealed.
Years ago, I experimented with a cone I'd made based on a parabolic curve to reflect sound from a driver facing upwards out 360 degrees. I made it from plaster using a forming tool I'd made from masonite, sheet metal and tubing. This technique was pretty easy and produced a very smooth and fairly accurate surface.
What my thought was, is if we were to create a mold using a similar tool like the diagram I've attached, then layer strips of foil on it, building the layers up using some sort of heat resistant adhesive, then we could produce virtually any shape reflector for which we could plot a curve. If the adhesive would handle the high heat of what we'd stuff into it afterward, we could just keep laying on more and more foil until reaching the thickness and strength desired.
Epoxy might fare OK being that the foil would form a primary heat shield. Any ideas?
For anyone like me who wants to find out more about orthogonal parabolic reflectors, have a look at US patent #5,765,934.
(http://patft.uspto.gov/netahtml/search-bool.html)
They even have the curve formula in the description.
I had a thought about creating our own reflectors. If you've ever seen fiberglass tubs or the like being made, they start with a mold which gets the finish coat applied first, then the supporting layers laid and spayed on. Once it sets, it gets pulled off the mold, and the nice smooth finished surface is revealed.
Years ago, I experimented with a cone I'd made based on a parabolic curve to reflect sound from a driver facing upwards out 360 degrees. I made it from plaster using a forming tool I'd made from masonite, sheet metal and tubing. This technique was pretty easy and produced a very smooth and fairly accurate surface.
What my thought was, is if we were to create a mold using a similar tool like the diagram I've attached, then layer strips of foil on it, building the layers up using some sort of heat resistant adhesive, then we could produce virtually any shape reflector for which we could plot a curve. If the adhesive would handle the high heat of what we'd stuff into it afterward, we could just keep laying on more and more foil until reaching the thickness and strength desired.
Epoxy might fare OK being that the foil would form a primary heat shield. Any ideas?
Attachments
tahustvedt,
The majority of the projectors here use a large panel (8" to 10") plus a convergence mechanism to beam the light from it into a cone about 1' high into an objective lens that is anywhere from 2" to 6" in diameter.
The conical beam structure feeding into the objective has some implications for the placement of any anamorphic structure if it goes before the objective.
Have you tried your lenses in this configuration, an is it better to place them before or after the objective lens?
Bill.
The majority of the projectors here use a large panel (8" to 10") plus a convergence mechanism to beam the light from it into a cone about 1' high into an objective lens that is anywhere from 2" to 6" in diameter.
The conical beam structure feeding into the objective has some implications for the placement of any anamorphic structure if it goes before the objective.
Have you tried your lenses in this configuration, an is it better to place them before or after the objective lens?
Bill.
I haven't tried them in this configuration, but they can be made as big or as small as they need to be. 🙂
The benefits of placing the anamorphic lens before the optics is that you avoid the geometry-distortion that comes from putting the anamorphic lens after the optics like with a normal projector and lens. At least I think you avoid the geometry distortion. 🙂
Tor Arne
The benefits of placing the anamorphic lens before the optics is that you avoid the geometry-distortion that comes from putting the anamorphic lens after the optics like with a normal projector and lens. At least I think you avoid the geometry distortion. 🙂
Tor Arne
After learning quite a bit from this forum and experimenting with a sharp qa-1500 and a dukane projector I have a question. Although my sharp has composite video in which works well I would like to use it with my computer. It seems as though it has a special plug on it and I got it with just a power supply. If someone would be able to post the pinout of a 26 pin vga connector that many panels use or a place to buy such a cable it would be most helpful to me and many others on this board. Easy way of finding the pinout would be a multimeter checking conductiy from one side of cable to the other. Thanks a lot.
xblocker:
you said that you had "a little sceptical to bring a fresnel into the image path. Fresnels are good in lighting path, but in the image path, image can't be better than fresnels quality". Have you ever try it and see the result? If not, then try it, you will surprise with the result, it's very little almost unseen the different with or without fresnel in front of LCD panel!
(it depend on how good your fresnel panel quality).
biteon:
your projector using 2 fresnel panel, to converge the light, how do you place the fresnel?
Is it: lamp-fresnel#1-LCD-fresnel#2-objective lens?
Or: lamp-fresnel#1-fresnel#2-LCD-objective lens?
If your setup is the second one, would you mind trying the first one, just to see the different?
Distance between lamp and fresnel#1 = focal length of fresnel#1 (OHP fresnel fl is about 1 ft), placed fresnel#2 an inch away from the LCD, adjust obj. lens until you get projected image sharp.
woneill:
latest discussion about using diffuse lamp and treat LCD panel as big and even light source.
Is it like using LOA (powerfull fluorecent lamp) that was discussed in part 1?
It failed, because the light spread away and lost.
Maybe using second fresnel after LCD will bring back the light beam and converge to obj. lens.
What do you think?
Thank's.
you said that you had "a little sceptical to bring a fresnel into the image path. Fresnels are good in lighting path, but in the image path, image can't be better than fresnels quality". Have you ever try it and see the result? If not, then try it, you will surprise with the result, it's very little almost unseen the different with or without fresnel in front of LCD panel!
(it depend on how good your fresnel panel quality).
biteon:
your projector using 2 fresnel panel, to converge the light, how do you place the fresnel?
Is it: lamp-fresnel#1-LCD-fresnel#2-objective lens?
Or: lamp-fresnel#1-fresnel#2-LCD-objective lens?
If your setup is the second one, would you mind trying the first one, just to see the different?
Distance between lamp and fresnel#1 = focal length of fresnel#1 (OHP fresnel fl is about 1 ft), placed fresnel#2 an inch away from the LCD, adjust obj. lens until you get projected image sharp.
woneill:
latest discussion about using diffuse lamp and treat LCD panel as big and even light source.
Is it like using LOA (powerfull fluorecent lamp) that was discussed in part 1?
It failed, because the light spread away and lost.
Maybe using second fresnel after LCD will bring back the light beam and converge to obj. lens.
What do you think?
Thank's.
Hi Gunawan,
I think the stuff we have been talking about recently differs from the LOA setup in two ways:
1) The LCD is quite directional, and has poor efficiency for light rays VERY off-axis (by that I mean light rays that diverge considerably from being perpendicular to the LCD). Many LCDS seem to have a noticeable fall-off in intensity once the angle of the light is > 20 degrees from perpendicular. Thus the LOA light sources would be very inefficient due to their absolutely diffuse output.
2) Like the LCD, the fresnel is quite limited in its viewing angle: one of the compromises in the construction of a fresnel that allows it to have an f-stop < 1 is that it is only designed to receive light at a given angle, and transmit that light at another given angle (within a few degrees either way). Most are designed to receive parallel(ish) light and focus it to a point. (See the fresnel-tech website for more info). When they describe a high quality fresnel, they generally specify the position of its "conjugates". These are the points where if a light source is placed at one point, its image can be effectively viewed at the other without distortion or scattering. Thus, most fresnels are designed to have the incident conjugate point at infinity, and the image conjugate point at the lens's focal point. If a viewer is placed at this conjugate point, then the fresnel will operate without significant distortion. The further away the viewer is from this conjugate position, the more distortion that is introduced by the fresnel. The same can be said for the position of the light source - the more its rays diverge from parallel, the more distortion is observed (placing an LCD emitting parallel rays close to the fresnel is in interesting philosophical point...). This is why the fresnel's can be quite directional - using it one way around gives virtually no distortion, and using it the other way ruins the image. This is also the prime reason that most OHPs use two fresnels facing each other...
Where I am trying to get to here, is that the way we are using the fresnel, it is optimised to take a roughly parallel beam coming from the LCD and beam it into a light cone with its apex at the main objective. Slight divergences from parallel in the light from the LCD are within the tollerances of the fresnel, but majorly diffuse light sources are going to give poor results with lots of scattering and distortion.
Thus, unlike the idea of throwing a LOA behind an LCD and putting a lens in front, this requires some more precise engineering. A fresnel might help, but the diffuse nature of the LOA is still far from optimal.
The situation is actually slightly more complex than this, because the optical qualities of the objective need to be fairly closely matched to the fresnel.
The fresnel is operating in magnifier mode - meaning that the light source (LCD) is placed closer then its focal point (the rays from the LCD are never 100% parallel, and hence the philosophical point mentioned earlier is resolved - yup, too much coffee!).
In this situation, even though the rougly parallel light is being beamed from the fresnel into a cone shape, the image produced by the fresnel is actually virtual - behind the fresnel, and behind the LCD itself (this is standard magnifier theory, and the reason reading glasses work - this is not just one of my crazy schemes that would have worked if it wasn't for those meddling kids...).
In order for the objective to correctly focus the image, it must be placed not only at the correct point relative to the virtual image of the LCD to focus the image on the screen, but also close to the conjugate point of the fresnel to actually make the most of the light cone, and avoid any distortion... The two points must be very close, or else, brightness, contrast and clarity suffers.
Before everybody screams, "I told you so," though, it must be said that the optics of an OHP are already optimised to work this way: the fact that a normal transparency is placed on top of the fresnel layer, and not sandwiched between its two fresnels is purely a function of convenience: it is very difficult to write on a transparency when it is between two fresnels... 😉
This is why the focal lengths of the various objective lenses for these devices are different to what would be expected if you were using the standard projector focal length calculations for original image position : projected image position...
Overall, my own personal recommendation for these configurations is to use one or more roughly parallel light sources to illuminate the back of the LCD, place a single fresnel close to the emitting surface of the LCD, and beam the light to the objective. This captures more of the light from the LCD, and relies less on the quality of the original light source being a point emitter.
Having said all that, if the LOA devices are able to produce a very high intensity light, equivalent to the MH bulbs, but without the heat, I believe that there is a fairly easy way to convert their diffuse output into a single high quality point source without TOO much loss. I was never able to find a VERY high brightness bulb at Home Depot (there are no WalMarts near me), so I never explored the option fully.
Bill.
I think the stuff we have been talking about recently differs from the LOA setup in two ways:
1) The LCD is quite directional, and has poor efficiency for light rays VERY off-axis (by that I mean light rays that diverge considerably from being perpendicular to the LCD). Many LCDS seem to have a noticeable fall-off in intensity once the angle of the light is > 20 degrees from perpendicular. Thus the LOA light sources would be very inefficient due to their absolutely diffuse output.
2) Like the LCD, the fresnel is quite limited in its viewing angle: one of the compromises in the construction of a fresnel that allows it to have an f-stop < 1 is that it is only designed to receive light at a given angle, and transmit that light at another given angle (within a few degrees either way). Most are designed to receive parallel(ish) light and focus it to a point. (See the fresnel-tech website for more info). When they describe a high quality fresnel, they generally specify the position of its "conjugates". These are the points where if a light source is placed at one point, its image can be effectively viewed at the other without distortion or scattering. Thus, most fresnels are designed to have the incident conjugate point at infinity, and the image conjugate point at the lens's focal point. If a viewer is placed at this conjugate point, then the fresnel will operate without significant distortion. The further away the viewer is from this conjugate position, the more distortion that is introduced by the fresnel. The same can be said for the position of the light source - the more its rays diverge from parallel, the more distortion is observed (placing an LCD emitting parallel rays close to the fresnel is in interesting philosophical point...). This is why the fresnel's can be quite directional - using it one way around gives virtually no distortion, and using it the other way ruins the image. This is also the prime reason that most OHPs use two fresnels facing each other...
Where I am trying to get to here, is that the way we are using the fresnel, it is optimised to take a roughly parallel beam coming from the LCD and beam it into a light cone with its apex at the main objective. Slight divergences from parallel in the light from the LCD are within the tollerances of the fresnel, but majorly diffuse light sources are going to give poor results with lots of scattering and distortion.
Thus, unlike the idea of throwing a LOA behind an LCD and putting a lens in front, this requires some more precise engineering. A fresnel might help, but the diffuse nature of the LOA is still far from optimal.
The situation is actually slightly more complex than this, because the optical qualities of the objective need to be fairly closely matched to the fresnel.
The fresnel is operating in magnifier mode - meaning that the light source (LCD) is placed closer then its focal point (the rays from the LCD are never 100% parallel, and hence the philosophical point mentioned earlier is resolved - yup, too much coffee!).
In this situation, even though the rougly parallel light is being beamed from the fresnel into a cone shape, the image produced by the fresnel is actually virtual - behind the fresnel, and behind the LCD itself (this is standard magnifier theory, and the reason reading glasses work - this is not just one of my crazy schemes that would have worked if it wasn't for those meddling kids...).
In order for the objective to correctly focus the image, it must be placed not only at the correct point relative to the virtual image of the LCD to focus the image on the screen, but also close to the conjugate point of the fresnel to actually make the most of the light cone, and avoid any distortion... The two points must be very close, or else, brightness, contrast and clarity suffers.
Before everybody screams, "I told you so," though, it must be said that the optics of an OHP are already optimised to work this way: the fact that a normal transparency is placed on top of the fresnel layer, and not sandwiched between its two fresnels is purely a function of convenience: it is very difficult to write on a transparency when it is between two fresnels... 😉
This is why the focal lengths of the various objective lenses for these devices are different to what would be expected if you were using the standard projector focal length calculations for original image position : projected image position...
Overall, my own personal recommendation for these configurations is to use one or more roughly parallel light sources to illuminate the back of the LCD, place a single fresnel close to the emitting surface of the LCD, and beam the light to the objective. This captures more of the light from the LCD, and relies less on the quality of the original light source being a point emitter.
Having said all that, if the LOA devices are able to produce a very high intensity light, equivalent to the MH bulbs, but without the heat, I believe that there is a fairly easy way to convert their diffuse output into a single high quality point source without TOO much loss. I was never able to find a VERY high brightness bulb at Home Depot (there are no WalMarts near me), so I never explored the option fully.
Bill.