Slashdot Mirror
Building Cheap 100 Inch TVs
Nastar writes "If you visit eBay and such places there are guys selling 'kits' so that you can easily build your own 100 inch projection screen. There are websites such as 100InchTV selling the instructions for around $10 a pop. They say "this is the only product of this kind on the web" and "it is now possible to convert any type of television or computer monitor into a 100 inch video system that's truly amazing!". I don't like the idea of these people selling this information, especially when you can get it free from the good people at BSTV BSTV. Ihaven't built mine yet, but the reports of quality differ from so-so to fantastic! I suppose it depends on perfecting the technique involved. "
This is great!
I can get a diploma, make $20,000 in just 2 weeks, and now I can have a 100 inch tv for little cost at all!
I'm gonna start reading my hotmail bulk-mail folder more often!
So, once people can buy tiny TV's and make them project perfectly well onto large screens, does this mean that the consumer electronics industry will have to readjust itself? Or does anyone think that there will be lawsuits from industry groups and lobbyists to try to block this kind of thing?
When nuance becomes the only objective we lose the ability to function
A crappy looking site AND a pop-up. Thanks, for the heads up.
How big of a room do you need for these monster screens? It seems to me that you would first have to have a huge room for this. Friends of mine have a 65" TV in a rather large living room and still it's pretty close. In this case you would also need some distance for the projector, right?
/.-ed faster than the blink of an eye.
PS I couldn't get the bstv I guess they were
i wonder if CmdrTaco is "high-up" on a "worthwhile" pyramid scheme...
Is this a misprint?
The biggest TV I've ever had was 12-inches and he said he'd never seen one bigger. Great tits as well.
I can't believe this is on Slashdot... so disappointing.
This is as stupid as blowing up a 150x150 pixel image to 1600x1200 in photoshop and expecting a good result.
You'll end up with a dark, low contrast, blurry mess, but go for it.
The guy who posted this story is probably someone who was selling the plans either on eBay or on the `net for $10 a pop and figured "If you can't beat them, /. them".
Well, it worked.
Yeah, the instruction costs $10. It doesn't tell you the equipments you have to buy.
For me, constructing 100 inch or even more display is "easy". Just buy a projector (that costs $4000) and then project it to a screen or wall. Simple. The farther the distance, the bigger is the resulting image. You can then adjust the focus. Voila. Fragging big time! :-)
--
Error 500: Internal sig error
Life size porn. [homer drool]
While the idea of turning a 17" monitor into a 100" one that would take up a good portion of my wall sounds intriguing, it sounds incredibly doubtful to me. Think about how ugly low resolution is.. especially on a large monitor. I haven't looked at the site yet, but I would imagine they simply magnify the image someway, if that's the case then you're just blowing it up.. nothing special. But doing that would uglify everything. 1/2" pixels don't sound particularly appealing to me.
<wik>/bin/finger that girl in the back row of machines.
I've heard that the quality is only good for either animated movies, or real movies. I can't remember which it was, but at the time I was researching this stuff, I saw mostly images of one type, which I think was animated.
As you can see from the image at BSTV, actual footage comes out as you would expect, only so-so. It makes sense that this would only work well for animations, as those usually have large areas of solid colors, and would appear less pixelated when blown up as such.
XML is like violence. If it doesn't solve the problem, use more.
The link given in the article goes to a domain's for sale page.
Damn... and to think, all this time I thought my 21" monitor was the bomb. I didn't see that my RedHat config supported a 100x100 bazillion pixel resolution, but maybe in the 7.2 release.
Why on earth would I want a 3-foot tall transvestite?
Matt
I remember reading about one of these a while ago.
I can't get to the linked site right now (I'm presuming it was slashdotted allready), but the way it worked was to basically use a magnifing glass. The screen emmits through a box of a certain size (the screen size), If you put a lense over that, in theory, you could magnify that light, so that it would be large enough to fill a "100 inch" screen, but it would look horrible!
I would think it would be very blurred, very hard to see (they don't give off THAT much light), and the colours would wash out.
I'd be curious to hear of anyone's actual experiences in building one of these.
Just MHO, of course.
Colin Davis
At least for me, the site popped up a window I couldn't get rid of when I tried to leave, and Netscape crashed.
Down with sites that abuse javascript.
Oh, and nevermind the fact that with today's technology and a greater emphasis than ever on DVD and digital picture we're willing to throw away $10 at whatever snake oil peddler comes along. "Just project it on your bed sheets!"
For shame this made it as a Slashdot topic.
Schnapple
http://members.tripod.com/schnapple99/
Schnapple
Anyone wonder if this might be an illegial modification of your Television, depriving the TV producers of the money you would have paid for larger sets?
Colin
Colin Davis
I have an oollllddd (1980??) copy of Popular Electronics kicking around somewhere that shows you how to do this too. Maybe when big screen TVs were hard to come by and insanely expensive, this was a good idea...
"Tomorrow's forecast: a few sprinkles of genius with a chance of doom!" - Stewie Griffin
http://www.google.com/search?q=cache:1pInHo8PDFk:w ww.webone.com.au/~caoz/bsinstructions.htm+%22free+ 100+inch+TV+projector%22&hl=en
Many years ago I participated in a "buy something/subscribe to something (I dont' remember what it was but it was something I wanted at the time) and get a free big screen TV". What I got was a large fresnel lens in a plastic frame that you put in front of a regular TV to project its image on a wall, just like on the website. I never tried it out for its intended use but I did have a good time using it as a death ray^h^h^h solar concentrator to set leaves and stuff on fire.
Error:
Strike 4, your outta here mister.
Now take that and multiply it times your worst possible dream to get pixels the size of green peas across the wall in your 100" display.
Still, it would be cool for gaming. Can you imagine playing Quake III with this? And it would be more suited to gaming than an LCD projector, because the refresh rate is going to be whatever your monitor uses, rather than the dismal LCD refresh rate. All in all, a pretty cool idea.
If a message that has been moded up recieves enough troll responses then it actually will get moded back down. I like to think of it as the "troll pull" effect.
Google cache right here
w ww.webone.com.au/~caoz/bsinstructions.htm+BSTV+100 +inch+plans&hl=en
http://www.google.com/search?q=cache:1pInHo8PDFk:
This is that "turn your TV brighness ALL the way up and then some, and use this frenzel (?) lense" thing, no?
Humm.... do I pay $3,600 for a 3x3 LCD wall.
Or $10 for a kit to make a 100 inch TV....
The big screen TV people are working hard on cost reductions and vast improvements in quality and maintainability -- I've seen some demos of stuff that's coming out soon and it's fantastic and can be made cheaply.
There are other sites with the instructions that haven't been slashdotted. See: http://www.greenspun.com/bboard/q-and-a-fetch-msg. tcl?msg_id=0038A5
If that doesn't survive, get it from the google cache.
ARP
Asked who what?
Like my eye sight isn't bad enough already!
Maybe you've heard of Amway...No??? Well sit down, let's chat. HEY!!! Where you going???
Darn....guess it's back to "Lose weight now, Ask me how!!"
Anyone sending money to this guy is a foole.
Color me surprised. Having made one in the past, uh. On the cheap, it's not horrible, but let's just say I won't be trading in my Vega anytime soon.
Easy does it!
This comment has been submitted already, 276865 hours , 59 minutes ago. No need to try again.
GOOD CALL! Yeah, I did. But my linux box decided not to boot one day after I moved it from one house to another. As such, slashbot was dead. But... I've been writing one for AIM that uses the Protista functionality. Fun stuff, but hard to finish while taking midterms. (as such in 9 minutes)
To scratch the surface. Javascript is fundamentally evil. It is the spwawn of Satan and it need to be consigned to hell where it belongs. Javascript is the beast unleashed upon the earth. The best way to repel the beast is of course to turn off Javascript. Just look at the incredible number of evil things you can do in the way of spying and remote hacking and destruction with Javascript. Check window size, check browser, open as many windows as you want till the browser crashes, run nimba launch scripts and other viral and trojan script kiddiez. As I said the perversion of Javascript is limitless because of its evil nature. Turn the shit off.
My dad had a setup years ago that was basically a wooden box with a lens. Inside the box, he put a 13" TV with the picture reversed and upside down (I have no idea ho he managed that). He projected it on the wall. It looked fantastic. The most expensive part was the lens.
The only real downside was that you could really only see it well if the lights were turned down (or off).
"Tell me doctor, with all of your defenses, are there any provisions for an attack by killer bees?"
I have found the plans for the Top Secret Big Screen Simulator that THEY don't want you to see! Banned in 52 states! And I'm not even going to charge you:
1. Close eyes
2. Place forehead against monitor
3. Open Eyes
Voila! Experience the field of view, the giant pixels, the intense headaches without even having to alter your current setup.
m00.
I view selling this type of information on the same level as selling free software. Effectively the seller is earning his money by finding audiences who aren't otherwise aware of the information and promoting it to them.
It's always fun to go into the junk-mail folder and look at some of the crap that _somehow_ must seem believable to some people.
Here's what the site itself says:
"For entertainment purposes only. This is a FUN site. We make no claim that anyone will be completely satisfied with our product"
is that if you magnify a TV's screen by a factor of 2, you reduce the brightness by a factor of 4. Magnification factors of the sort mentioned makes the TV too dark to comfortably watch.
This would be great. Right now, I can barely see my pixels. If I could blow them up really huge, I might take the time to get to know each one. Soothe them when they're red, give 'em a hug and a smile when they're blue. Sometimes, just drop by to talk.
I've considered doing this in the past, but didn't think it would be possible and never bothered investigating. This stuff is old hat, but still something fun to do i'm sure :)
I remember doing something like what I can only guess is on the site (seeing as its slashdotted now) when I was like 14. Just get a big magnifying glass lens, the type you can pick up at American Science and Surplus for really cheap, get a decent mirror, put your TV on its back, setup the mirror in a box at a 45 degree angle, cut a hole in the side of the box for the lens, put the whole contraption on the TV, point it at a sheet, turn off the lights and viola, really big, crappy resolution TV. It was a bunch of fun as a kid, playing crappy resolution NES games on it though, and an application of physics if you're into that sort of thing (or teaching your kids that sort of thing or whatever)
If not now, when?
I'm a rising optics major in U or Rochester, and know my share of optics, and would just like to say, that there simply is no way you can make quality, sharp, brigh, 100inch image without precision optical design and parts. Just be cause of limitation's of .. well physics... There are very good reasons 100inch projection TV's are pricy, assuming you dont want a muddy chromlay and geometricaly distorted blob.
I watched the first shuttle launch on this type of setup when I was a kid. My dad knew the owner of a TV/Stereo store who loaned him the fresnel lens converter.
We had to use a 13" TV because that's how big the hood was, and had to set it upside-down on a table to get the projected picture rightside-up. If we turned the brightness and contrast all the way up, we got a passable picture in a completely dark room. CRT's are made for direct viewing and don't put out enough light to project well.
So yeah, technically it works, but don't expect the same image quality you might see from even a low-end projection rig. It does make a cool toy for a kid or a cheap science fair project though...
I experimented with a similar lens arrangement like 15 years ago with a fresnel lens from an overhead projector. Neat idea, but, well, it sucked.
I've been wondering for years, and have wondered aloud here before but gotten no response, about the possibility for building a scanning projection TV out of LEDs and mirrors.
Basically, rather than projecting an entire image at once, like an LCD projector does (and, thus, limiting your resolution to how big your LCD or DLP array is), this would take the output of red, green, and blue LEDs and bounce them off a mirror vibrating in two directions (horizontally and vertically) to provide a raster scan. With today's high brightness LEDs (ever notice how blindingly bright the new LED traffic lights are?), I'd think this could, with the right focusing system, give you a quality image on a decent screen.
All that remains is to decode the video signal for processing by the projector. In a simple mode, you might even be able to simply take the HSYNC and VSYNC signals and, essentially, use them to mark the edges of your scanning motion, then simply vibrate the mirror back and forth within that time frame. (this is hard to describe, but hopefully it'll make sense to some of you).
For something like this, the most expensive bit would be the lens at the front. You'd have a bunch of $2 LEDs (running cool and quiet, too, unlike the bulbs in DLP/LCD projectors), a simple electro-magnetic mirror mount (speaker coil for a prototype, maybe?), and maybe $50 worth of electronics.
Any EEs out there who think this makes sense? Or should I just keep waiting for HDTV projectors to come down to a kilobuck?
--brian
How is this any different than (say) O'Reilly selling books on Perl/Oracle/Linux, when people can get all that information for free on the web as well ? Someone has gone to the trouble of packaging the information, and sending it to people who may not even have web access, or may want printed instructions, so I say all the more power to them.
God forbid the light catch this thing just right. Probably burn a hole through your wall... or your cat.
http://windows.scares.us
I would think it would be very blurred, very hard to see (they don't give off THAT much light), and the colours would wash out.
I'd be curious to hear of anyone's actual experiences in building one of these.
I built a setup like this as a kid using a fresnel lens and a bed sheet. I even rigged a translation stage for the lens for precise focusing.
Problems were as follows, in order of severity:
Because nothing really acts like an ideal lens, the image focused on to a curved surface. I was using a flat sheet as my screen. This meant that either the center was in focus, or a ring around it was in focus, but not both.
You can reduce this by using a longer focal length, an aperture, or both, but this is trickier and loses light.
I was using one lens. This turned the image upside-down. This meant I had to turn the TV upside-down to get a usable picture. This made the TV image turn funny colours. I have no idea if this happens to most TVs or not. A well-made TV *shouldn't* have this problem - it _should_ only be gravity-sensitive if some of the focusing coils are loose inside it. The electron beam certainly doesn't care about gravity. YMMV.
You can get around this by using two lenses instead of one, or by turning the image upside-down with two mirrors before projecting it. This adds complexity and takes up space.
An alternate solution - that I used the first year I did this - is to put the TV flat on the floor and project on to a sheet on the cieling.
You get some colour spreading, but not that much. The main problem is that the image will be at least a little blurry no matter what you do. Especially if your lens is like mine and is scratched up from handling.
Projecting through a sheet degrades resolution, because the sheet scatters light within itself. You can either look at the image from the back (either getting a mirror-image or needing a mirror to flip the image), or use a very thin sheet and view it from the front.
I solved this by hosting my video parties in the basement and covering the windows. YMMV. Real projection TVs have CRTs designed to operate more brightly than normal TV screens.
These aren't insurmountable problems; just very annoying ones to solve.
I looked at this a year or so ago. I have an unresolved question which is slightly interesting. How well would a vector monitor (aka "Asteroids" or "Tempest") fair when projected? The lines are bright, but skinny. Will they be lost in the magnificant?
I make a joke about something that is an obvious gimmick instead of a serious product and it is moderated as flamebait? Interesting.
yeah and your reading and repsponding bozo
Why do I keep seeing all these instructions for building stringed musical instruments? "Do thing A, do thing B and viola!"
;)
Or perhaps you mean "voila!"
You forgot "hold their hair back when they're Green."
This is esentially the same idea as a school projector. The idea works but TVs don't put out enough light to make a very briliant picture. So you can only watch at night. You also still need a flat white screen to project your image onto. Essentially this is your poor man's big screen. It will never rival a real big screen TV but it will be cool to impress your frineds or at least for a fun physics project on light. Here's a link that I found that contains instructions as well as comments. http://www.greenspun.com/bboard/q-and-a-fetch-msg. tcl?msg_id=0038A5
The plans are for a box that mounts in front of your TV set that contains a giant Fresnel lens. These are scams and have been scams for the last thirty years.
You see those posters on street corners that say "Have a PC? Work from home! $1500/weekly"? This is the kind of crap you'll be selling.
Why is this even on Slashdot?
I was curious and found a link to plans. Assume it is the same type of design. I'll stick with my projector.
On a similar note... last year, I wanted a bigger TV set, but didn't have the money. So I just moved my couch closer to the TV... yes, I know it's sad. But it has nearly the same effect as getting a bigger set. :)
OtakuBooty.com: Smart, funny, sexy nerds.
Gives a whole new meaning to the Memorex ads. (is it live or is it Memorex)
Soprano's and Band of Brothers on 100"?
Then hook that up to the surround sound...
I'm there!
Goran
Carpe Scrotum - The only way to deal with your competition.
A buddy of mine built one of these things, or something similar to them. I don't know about all these people saying the quality sucks, but it was crystal clear for him. And oh god is Quake 3 gorgoues on it...
The difference is he started with a bigger TV (32"), and used a really high quality lense. I forget what he calls it, but he had in machine made espcially for this purpose. Cost about $700 to have done, but when you consider how expensive a reall 100" would be, it's not that bad
The thing is, you just can't skimp out like they say you can... Don't use a bedsheet, just a real projection screen, for instance.
This is totally valid technology, as long as you don't cheap out.
Has anyone stacked 4 CRTs and then used mirrors to stretch the images to cover the plastic monitor edges?
If possible, it would be much much cheaper than stacking 3x3 lcd projectors.
Heck, even using laptop screens would work as they have much narrower plastic borders.
For only $5, I will show you how to turn your puny 27" TV into a 686mm beast!
"People that quote themselves in their signatures bother me" - athakur999
Will this work with the $10 C.A.B.L.E. D.E.S.C.R.A.M.B.L.E.R that I can build with parts available at any Radio Shack?
Whilst ripping apart an old lapop a couple of weeks ago, it struck me that the heart of an LCD screen is just a glass panel. After thinking about having moving pictures on the wall, I came up with a possible idea.
Take one OHP (Overhead Projector), and one LCD screen. Remove all packaging on the LCD screen until you can see through it. Place the LCD screen on the OHP and hold down with some masking tape. Turn on OHP and LCD (make sure it's connected to something!).
Any comments as to why this won't work? I work out costs at around £400ukp new (£300 for LCD screen, £100 for projector).
Wireless Bristol
Something like that, for it's digital movie projectors. Costs an arm and both legs for the projector.
Best Slashdot Co
Great experience, it was like watching a Monet.
pronoblem
Well, I saw this ad on ebay six months ago, and realized it was nothing but a fresnel lens magnifiying a TV screen. I happened to have a really small one sitting around so I tried projecting my 5" B&W beast onto the ceiling. Well, it worked, but all the lights had to be off and even then it was a very dim picture and hard to keep in focus. It was about 100" though. A word of warning: I ordered some larger Fresnels from Edmund Scientifics to continue experimenting, but their focal length was way too long for them to be of any use. If you're going to try this, make sure you understand optics better than I do.
IANAEE, I got tired three credits short, but...
Consider a hypothetical tv show which displayed a solid, bright, red background. Your red LED would need to put out enough light to illuminate your screen bright red. Now, take your Photon microlight out of your pocket. (Surely all slashot readers have at least one of those by now. Ultra bright LED on a keychain.) Sit in a lit room and shine the microlight on a white surface, adjust the distance from the surface until your red (or white, or whatever color your microlight is) spot is about as bright as you would like the TV to be. Compute the area of the spot on the white surface. Mine is four square inches with a white microlight in a dim room. Maybe calibrate your idea of brightness by looking at your TV up close and then comparing to your illuminated spot.
Using the `no free lunch' rule of physics, you need to admit that a single LED is only going to provide enough light to adequatly illuminate 4 square inches. Hence, a 100" tv (4800sq in) is going to take 1200 LEDs. The way bright LEDs are something like $3 each in huge quantity, thats $3600 before you add optics, mechnical oscillators, and electronics.
This idea has been around forever. I don't remember when it came out, but I'm going to guess around 94 there was a 64k demo out on the demo scene. It was called acidwarp. I still have it somewhere. acidwarp.exe and after it's done running, it tells you how to build this. I made one, you just have to buy the fresnel lense for about $4 or so, and find a cardboard box to put it in. I only use it for showing geiss or other visualization programs on a screen in my room. The focus isn't good enough for watching movies/reading subtitles/browsing the web.
This has to be the worst scam i've ever seen on /.
"Here come see, read our reviews we are the best but the shit we're selling you, can't see it. You have to pay to see it first, and our screenshots there all unexisting files. Of course.... Oh and BTW! feel free to click on our tons of spam generating links. Click on our banners we need your clicks also, bla bla bla..."
Look, it's simple, bigger isn't better.
The satire form of expression is the most wonderful one in the world.
I found another site with the instructions for free. This one hasn't been /.ed yet so have fun:
http://www.ductape.net/~bradya/100inchtv/
Dozings.com -- Its kinda funny... If you're as crazy as me.
There is no need to reverse the image in a addition to turning it upside down. You only need to invert the vertical and invert the horizontal.
Turning it upside down effectivly inverts the vertical and the horizontal at the same time.
Think about it. Top becomes bottom, and left becomes right.
Im not here now... Im out KILLING pepperoni
Has anyone ever taken apart (or seen the inside) of a big screen TV? Do any of you youngins remember the old big screens from the 70's and early 80's?
The picture display tubes used in typical big screen TV's are in reality nothing more than liquid cooled versions of the tube used in a typical TV. These tubes are liquid cooled (on the front - it is a passive cooling - think of using water as a heat sink, with no pump) because they are driven to insane brightness levels (way brighter than maximum brightness on a normal TV set), to get the picture as clear as possible in the final result. Furthermore, most big screen systems use three tubes, one red, one blue, and one green (they are black and white tubes with filters - not unlike stage gels), each aimed and focused separately to get the highest resolution picture possible (this seperate aiming, etc is one reason why you should have your big-screen adjusted after moving it - even if it is across the room). HDTV sets merely use ultra high-res SVGA tube systems to get the resolution needed.
After that step, it is simple optics - most of the time no more than one or two largish glass lenses (with anti-chomatic aberation built in) and a mirror or two to flip and reverse the image - sometimes the image is projected inverted and reversed and bounced off of one mirror to get the final image. The idea is to get the projection as near parallel with the screen as possible. Where that isn't possible (due to the size of the cabinet), special lenses are added (or it is done electronically) to "keystone" the image in the proper direction so that it comes out "square" in the end.
That is all - amazing, isn't it, that one would pay almost 2000 bucks for a few TV sets, some wood , and some optics? Well, you do get a better quality system, and the optics are top notch, too - plus, the TV sets are anything but normal...
What these 100 inch plans and systems try to do is do all of that on the cheap - a light tight box is built around the TV set, a fresnel lens is added (it is a cheap lens), and you turn the TV set upside down and add a mirror to reverse the image. Typically, you might also crank the brightness up to get a slightly better image for the larger 100 inch displays.
What does this get you? Actually, if you do everything perfectly (and watch out turning that set upside down - sometime the magnetic field of the earth screws things up, and you need to degauss the set to recover in the upside down mode), have it all aligned, use a good fresnel lens, a good lighttight, square, painted black inside box with a nice mirror, and you use a larger set (15-19"), and a good projection surface (not a sheet - not enough reflection - ideally, you want a silver beaded projection screen, for maximum gain - but since it would be stupid to spend $150 on a screen for a $10 big screen, there are alternatives, more on that later) - you can get a reasonable image. You will have to turn out the lights, and let your eyes adjust - but you will get a watchable image. It isn't a scam. The edges will tend to be fuzzy, though, because a fresnel lens isn't a perfect lens, and has focus issues at the edges. Put a black border around your projection surface to mask these off, and things don't look too bad. Also, don't try to go for a 100" display - try a 40" display first, and adject until you are happy with pixel size and clarity. It is possible to make it look damn good, good enough for most entertainment uses.
Now, want to know how to make a better projection TV system (though this time, it will cost a bit - more than $10, but less than $500)?
LCD projection systems are really systems designed to rip the gullible off. At least with CRT projection, the manufacturers have an out with the special CRTs and optics they use. LCD projectors, though, are the simplest of them all (note, DLP projectors are not LCD projectors, so I can forgive their cost) - it is crazy that they sell these ultra expensive projectors that are nothing more that glorified slide projectors...
That's right! Slide projectors! The optics and light system are the same (nearly equal) as to what is in an "old-time" slide projector - the slide now is an LCD panel! This panel is typically rather small for it's resolution - but this doesn't excuse the cost, because LCD production quality is supposed to go up as the size goes down, and the price is supposed to go down as well, right? Well, it hasn't - at least I don't know where I can get a $150.00 800x600 LCD projector yet, which typically uses a smaller LCD display (less than 2" diagonal). Anyhow - all one has to do to build their own LCD projector is to get an LCD about the size of a slide, and drop it in place of the slide in a slide projector (which can be bought cheap off of Ebay). This kind of projector system was first described by Robin Cook in his book "The Virtual Reality Homebrewer's Handbook". One thing he recommended was to use a fan to cool the LCD, because the projection lamp could overheat the LCD, causing it to shut down or burn out. What is used for the LCD? Why, an LCD TV, of course - you take one apart, remove the backlight (because the projection bulb will be your backlight), and put the screen in place of the slide in an old slide projector. You also need to re-route the electronics and cabling, but it can be done. Also, try to use a TV with a TFT display for clearest moving images. It is also possible to scale this up by using larger LCD displays (various electronics surplus dealers sell $99.00 4 inch LCD displays for use in in-car video systems), and a custom lens/projection system. A larger LCD will give a clearer image.
Now, what will be the quality of such a system? All I can compare it to is a device I have, that works the same way, and is how I got my "Big Screen" experience cheap. I own a Fujix P401 LCD projector - cost me $250.00 a few years ago, and gives me an "OK" picture. I can comfortably display X on it if I use a 640x480 setting - some things are readable - but mostly I watch VCDs on it (using mtvp - anyone know of an equal Free replacement to mtvp?). Higher res images can be displayed, but they are fuzzy, at best. I would imagine a homebrew system to be comparable to this, possibly better.
Now, would it be possible to reproduce a three tube CRT system? Of course! You could build three of the 100" systems, but use black and white sets with colored pieces of plexiglas (or stage gels) in front of them. It would be a little bulky, though. I could imagine gutting some small (9" or smaller) portables to do this, and building a custom cabinet. Another possibility is to get (through various electronics surplus retailers on the net) surplus big-screen optics (which shouldn't cost more than $25.00/ea), and put them in front of the CRTs you are using. This would result in a more compact system (especially if you removed the casing of the TVs - be careful of the high-voltage inside, though - one hand in pocket when poking around inside those sets!!!).
Now, what to use for the projection screen - well, since you are doing this on the cheap, you can't very well buy a nice screen - they can be expensive. However, sometimes you can get a used silver projection screen fairly cheap (under $50.00 sometimes on Ebay, less at garage sales) - but make sure it is good quality. Most of these are tripod style, and don't have a ratchet mechanism to allow a "pull-down-from-ceiling" setup, that is much more enjoyable. To solve this, use what I used: A pure-white blackout shade. These can be found at Home Depot, and they can be had for ultra-cheap prices (less than $30.00 for the largest size). You can build mounts by using some bolts and a couple of bookshelf brackets, with careful setup, a pull down system is easy (I had mine together in an hour). These shades are smooth, have a high reflectivity, and are very inexpensive. Another alternative is high reflectivity white paint on a board. You can also use a white vinyl shower curtain, stretched tight. There are numerous options. Just look around and imagine.
Finally, I want to tell you what I used to display X under Linux on a TV (or projection system with composite input, like these homebrew projectors use). There is a device called the Averkey iMicro that is a true plug-and-play system. Pop it into your VGA port, load up X, and it will recognize the settings - no need to mess around with your XF86config settings (unless you need a certain res) - high-res, low-res - don't matter - it can recognise it. And it gives a great image, and it is cheap (around $100). I highly recommend this product.
OK - now you know the scoop. I hope this long, long comment will help someone. Realize that you won't get the be-all and end-all of projection images with these systems. However, I don't think they are a scam - in reality, they are selling the lens and some plans, and true, as good or better plans could be found on-line. But people are lazy, so I tend to think that they are selling a lens, some plans, and the cost of research - for $10.00 or less in many cases, that isn't a bad deal. I tend to wonder if I compiled all the info I had onto a CD, and sold that with a lens, if I could make some cash - but I am lazy, so if someone else wants to take a stab at it, go for it!!!
Have fun, my friends!
Reason is the Path to God - Anon
Alot of people have remarked that the pixels would be huge. I just wanted to point out that television and television CRT's are innately analog and have no pixels. The scan line is drawn in one continuous swipe horizontally across the screen. I'm not arguing that the image would be great, I'm sure it wouldn't be, but I don't think it would be as grainy as alot of you suppose.
I would imagine that the issues here would be with brightness more than grainyness. Large screen televisions are limited to the same basic resolution as small screen televisions are, the source data, a.k.a. the video signal, is sent at the same resolution to all TV's. Televisions have 525 vertical scan lines, but horizontal resolution is difficult to describe in terms of pixels as they are different for the chroma and luma components. The luma ( brightness, i.e. black and white ) horizontal resolution is 442, the chroma ( color ) horizontal resolution is 377. This was done for a number of reasons, including bandwidth limitations, backwards compatibility with black and white televisions, etc... If you take this overlap of color and black and white signal, then add the fact that the vertical scanlines are interlaced ( vert refresh is 60 Hz, i.e. 30 frames per second ), you will see that standard television is not at all similar to computer monitors. Televisions are very low definition devices ( thus the need for HDTV ) and that low definition means that a magnified image might benefit from the shortcomings of the human eye.
Please note that all my numbers were for NTSC, most PAL implementations run at 50Hz vertical refresh, 625 vertical scan lines ( chroma and luma horizontal resolutions vary amongst the PAL standards ). SECAM is 50Hz, 625 lines as well.
Also note that this is for standard TV, HDTV used MPEG-2 just like DVD video and thus is obviously a digital format.
The way one uses a tv vs a monitor are different, I tend to sit kess then 3ft from my computer display but perfer to watch our 50in toshiba from accross the room. So even if your picture is a bit grainy its not like you'll see it all that much unless your vision is like 20:10 or something inhuman.
Drat. I clicked this hoping for some tasteful and intelligent bestiality, and all I got was a lame supremacist rant.
Used to have a 486 laptop designed to double as a projection system. You could remove the plastic back from the display and lay the computer on an overhead projector. It was a generic make. (Sunflower?)
The biggest problem with it was that the screen sat an inch or so above the normal focal plane of the projector. You couldn't rack the lens up high enough to focus, especially if you were trying for a big image. Other problems were the result of the flimsy generic hardware: cheap telescoping aluminum legs to prop up the laptop base, weak fans to keep the LCD cool... Very mickey mouse. Used this for a year before talking the boss into a more expensive but more convenient InFocus.
With sufficient use of duct tape and some kludging of the lens, I expect this would be an improvement over the "100-inch TV" projection method
Sweet, this means I can blow up old Dukes of Hazzard reruns onto my trailer wall, and charge my friends $$$$ to view them. Nothin like some Pat's Blue Ribbon and a good flick on a hot, tuesday afternoon. I may even accept food stamps.. wow thanks!
Please post some news. As in NEWs.
Thank you.
If you could be told what you can see or read, then it follows that you could be told what to say or think - BoC
The problems are in the physics. TV's can get by with a very small number of electron guns because they are extremely fast - they move the dot around at frequencies in the tens of kilohertz. This is a smidge higher than most reasonable mechanical systems would even think of tolerating. [handwaving approximation: 10KHZ ~= 600,000rpm]
So to trade this off, you can have a pile of LEDs, except that the LED's aren't exactly small. Especially the spiffy new ones that www.lumileds.com / www.luxeon.com are coming out with. In order to get an image out on the wall, you need to dump an optical system in front of the LEDs, and big LEDs means big optics (unless you start trading off efficiency/complexity/cost by hiring a smarty-pants optical engineer).
Its not exactly a small/simple task, but there might be room in there for a reasonably useful system.
Personally I'm poking around a diode-laser based vector graphics using some of the small micromotors (few mm diameter) that are pretty common nowadays. mmmm. wall sized emacs session.
AC comments get piped to
"My TV distorts colour when turned upside-down"
Tv's are balanced for the magnetic poles of the region of the world that they are to be operated. When you flip a TV over the earth's poles are reversed causing the discoloration.. The same can be said for monitors. The cure is to degauss the screen. Most current TVs will do this automatically, but you might have to power on and off several times.
Your idea has merit. But -- and this is a big one -- there would be a ton of design work necessary.
I've worked with galvanometrically-controlled mirrors (the kind used to make x-y projectors for laser display systems). Cool stuff. Very, very expensive for good ones, and to get a nice, clean picture, you sure would need a set of good ones. Why? Think of the simplest monochromatic case where you want to project a single LED (or laser) in a scanning path. Any slight deviations from perfectly straight lines in a regular array during the scan will appear as distortions in the image. Getting a motor to track so that a projected dot moves not only at a constant rate on a screen, but also does so without any substantive deviations is difficult. In my lab at Caltech, we spent well over $10,000 building a very similar system, although ours was for projecting static images rather than dynamic ones. The lengths you must go through to get something that is usable are remarkable.
To get decent response time (in merely 10s of ms; for video you'll need better) you need special ultra-light mirrors and big heavy motors. Speaker coils are designed to move speaker cones, not mirrors which weigh 1-2 orders of magnitude more. Also, the controllers for such things are non-trivial and must be carefully tuned for the individual load. Don't expect to slap together a 100W audio amplifier from some design book and expect it to work in this case. The loads are very different.
To get decent mechanical rigidity for such a system, you will need an optical bench, and a friendly machinist who is willing to make high-accuracy parts. You can skimp on things like the supports (we used a wooden frame), but if, for example, the two X and Y mirrors are 89.95 degrees apart instead of 90.00, you get a mixed trapezoid and parallelogram image that will need to be corrected in the decoder. We ended up using independent first-degree corrections for each axis; we should have used a two-dimensional, second-degree (parabolic) correction.
Because such things are also going to be sensitive to temperature variation (remember, everything expands when it gets hot), you will also need a heating system and nice controller for it. The gavanometer controllers we used also had a nice heating system built in that kept the motors at 40C, independent of what we were doing to them.
That said, you can probably do a crude job with
surplus equipment, as scanning mirror assemblies are often used in photocopiers, printers, and the like, but it's not the kind of thing you can do in a weekend. Getting an image that would rival a middle-of-the-road DLP/LCD projector would take a very long time and a lot of effort.
Getting spinning mechanical things to achieve the kind of accuracy to get reliable pixel-by-pixel resolution without distortion is not easy. Not impossible, but definitely not easy.
-- pz.
Put my fist through my alarm clock with its ding-dong death inside my ear. - The Blackjacks.
yeah baby, it's all good beeyotch!
second society
Suppose you used a middling-sized laser rather than an LED: could this be bright enough? (Monitor burn-in is an issue, though. :)
Alternately, instead of a pixel-mapped display, you could use this scheme for a vector display (anybody remember those?). Trickier to drive, but potentially a lot easier to get enough brightness.
"it ain't easy bein' green."
And yes, I ment the frog. Not the file transfer protocol.
Ribbit
I don't like the idea of Red Hat selling Linux, especially when you can get it for free from the good people at Debian.
I don't like the idea of record companies selling cds, especially when you can get them for free from the good people at Gnutella.
Here is an idea --- cache a website in multiple places, THEN release the story/cool new product/file/whatever while linking to the cached info.
I sure would like to visit the webpage and read for myself all of the interesting details.
What do you think? Too difficult?
Screw television.
Here's what I think would be fun:
For about $100, you can buy a 48"x36" freznel lense. I want to mount it in a giant magnifying glass frame with a long handle, (kind of like one of those leaf scoopers used to clean the crud from the surface of suburban swimming pools.).
Then. . . Oh boy the damage you could cause!
We're talking about being able to set on fire, with a dowel and a sheet of plastic, the upholstery inside parked cars, punishing stupid owners who leave their automobile anti-theft devices blaring unattended. --Without even having to touch the vehicle! --Or you can set office buildings on fire by shining sunlight through the windows just by walking down the side walk with the magnifier over your shoulder. Any number of bizarre fire-crimes become feasible.
Yeah, yeah, I know you could get the same net effect with a can of gasoline and lighter, but this is FAR cooler! (What!? I'm just walking here with my sheet of plastic! I don't care about optics! Get your filthy law enforcing paws off me!) And if you somehow managed not to get caught, the authorities wouldn't know what the heck to make of it. --You might even be able to popularize the term, 'spontaneous office furniture combustion,' or something equally weird.
Of course, in this day and age of too many cameras and rampant terrorist paranoia, you'd probably have your eight foot magnifying glass and turban confiscated.
Bummer.
Fantastic Lad --What's a little pyromania among friends?
A TV scans across (the horizontal refresh rate) the picture tube at 15.7 KHz. The mirror would have to match this rate to reproduce a picture from a convention broadcast facility, so it would have to vibrate across the chosen field of view 15,700 times per second. I don't know the physics involved behind making a mirror move that fast, but it sure would sound awful, since its vibration would cause compression waves in the air at a very high pitch.
The TV scans from the top of the screen to the bottom (the vertical trace and retrace) 60 times per second. The mirror would therefore also have to deflect up and down 60 times a second. In my opinion, that makes the mirror movement pretty complicated.
Don't despair, all is not lost! I remember seeing an early head mounted display that used a column of pixels and a mirror that vibrated left and right 60 times per second. I think that a pretty good image could be created by making a row of 640 clusters of LEDs (each cluster being 3 LEDs - a red, green and blue) and scanning the mirror up and down 30 times per second (Only 30 instead of 60 because you can paint both the odd and even frames at the same time). There would be some electronics involved, since the horizontal picture image must be captured and store in the LEDs. This also has the advantage of providing way more light than 3 LEDs, so you'd have a brighter image.
Good luck
Some great infos and links on howstuffworks.com
http://howstuffworks.lycos.com/question244.htm
- Curiosity is not a default !
I used to sit in the dining room and watch the TV in the next room thru $20 binoculars. It looked huuuuge!
And since we only had a 1963 B&W set, the color fringing from the glasses made it a "color" TV!
I was five at the time, but hey.
"Win treats sysadmins better than users. Mac treats users better than sysadmins. Linux treats everyone like sysadmins."
I recently built a projection system using an LCD Panel (manufactured 1995,640x480 16m colors), a used high intensity projector (you at least want to get 4,000 lumens), and a TV tuner card for the computer. All of these products were purchased off of Ebay.
:-) I get a clear, 5x4 ft projection screen on my wall, all for about the cost of $300.
I have watched DVD's, TV, and played 3d games, and it works flawlessly (other than the fact my bulbs burn out every 50-75 hours)!
"Shake yur bon bon"
I remember this exact concept, but it was applied to microdisplays rather than macrodisplays: Head-mounted displays for wearable computers. You basically described the exact workings of several of the products that the 'borgs at MIT used.
It seems to me that two spinning mirror cylinders set at right angles could scan out a sqare area on the wall much more effectively than jiggling a static mirror all over the place. You could add more sides to the cylinders to reduce the rotational velocity (or to increase the scan rate). Thus you have two parts moving in nice simple to control ways and intertia is working for you (once they've spun up).
Also, don't forget that led's have capacitance. In order to scan with an ultra-bright led, you need to be able to change it's brightness faster than your scan rate or bright sections will smear into dimmer sections and vice versa, i.e. blur.
My roommate and I did something similar to this in college, except we used a low-powered laser. Our goal wasn't to make a tv-type display; it was to make something similar the the laser projectors used at laser shows. There were no lenses involved. We bought 2 cheapo 4-watt speakers and ripped the cones out. Then we rubber cemented a mirror from the solanoid to the edge. We then mounted these at 90 degrees to each other and shined the laser so it reflected off both mirrors then hit the projection surface. We hooked the speakers up to an amplified sound card and generated frequencies that painted pictures with the laser. It worked great except we couldn't turn the laser off to make discontinuous objects, frequency response characteristics of the speakers and sound card limited what we could draw, one color, and our 0.5mW laser wasn't bright enough to cover large areas.
Sounds like you want to do something similar to a laser show. See http://www.laser-light-show.com/ for an example. The biggest draw back I can see with doing it with a led is keeping the beam focused over the projection distances you proposed. Now if we had cheap RGB lasers, it would be a fun project.
How am I going to watch "Fist of the Legend" subtitled, when the words are backwards?
If you live near a university, find the place where they surplus old stuff. At my university, University Surplus is part of the Property Control department, is only open one day a week, and hidden in some WWII military barracks on the South side of campus. You may have to look hard to find the one near you. Ask a custodian or somebody who works in a machine shop.
I go by regularly, and often see projection screens that are cheap. They sometimes have slide and flimstrip projectors. The prices are often lower than those on e-Bay because they are not trying to turn a profit, and you don't have to pay shipping.
Wow, awesome timing.
I'm in the middle of a Lunar Projection System(tm) project. I've solved the focus issue - infinity gives pretty accurate results. I've got a couple of ideas on improving the brightness. That just leaves one problem to resolve - can anyone suggest a really cheap solution to delaying the audio stream 2 seconds?
- - You can't take something off the Internet! That's like trying to take pee out of a swimming pool.
AcidWarp and The Warper
I am not really sure if this is the earliest incarnation - somehow, I doubt it. But it has to be an early one (1992)...
Reason is the Path to God - Anon
Box Camera.
This technique does better at reducing an image. It is a novelty, but the "projector" is huge.
by adding a magnifying glass or projector to the screen, you are depriving the copyright owners by reproducing the image on an unlicensed object, such as a wall
Not as far-fetched as it may seem as first. By modifying your television to have a larger display size, you potentially convert it into a tool for public performance, and even without the Digital Millennium Copyright Act and foreign counterparts, the copyright laws of the United States and most other jurisdictions reserve the right of public performance to the copyright holder.
Will I retire or break 10K?
I don't really think things are so bad that we need to moderate the editors, but just a weensy bit of research can help in these cases. There will always be slips, thank god for the BS detectors of the /. readers!
I survived the Dick Cheney Presidency 7 to 9 AM 7-21-07
Image Inversion:
It is possible to flip the wires around on the deflection coil in your TV or monitor. It is also possible to rotate the deflection coil assembly on some monitors/TVs. Here is a webpage detailing flipping wires.
BE VERY CAREFUL IF YOU ARE WORKING ON THE INSIDE OF A TV OR MONITOR - THERE ARE LETHAL VOLTAGES PRESENT, EVEN IF THE TV OR MONITOR IS OFF!!! DISCHARGE THE PICTURE TUBE AND ALL CAPACITORS!!! EVEN THEN, BE ULTRA-EXTRA CAREFUL - YOU CAN KILL YOURSELF IF YOU ARE NOT CAREFUL!!! IF YOU HAVE _ANY_ DOUBTS, DON'T FUCK WITH IT!!! I CANNOT STRESS THIS ENOUGH!!! (maybe I should add more exclamation points?)
I am amazed that the kid (at the link I gave) didn't kill himself.
Correcting Fuziness:
Two options - bend the screen horizontally (like the Torus screens in theaters), possibly vertically as well, to bring the edges in focus. Might be difficult to do. Option B (probably more difficult) would be to bend the fresnel lens slightly...
Reason is the Path to God - Anon
Thanks to the entire slashdot community for dashing my dreams. Now I just have to figure out how to get LEDs for, lessee, a 1920x1080 array, and...umm...HOW MUCH would that cost?
Seriously, I'm glad I finally got a good rundown on some of the issues here, especially the feasibility of image retention for such a fast scan (doesn't work) and the problem of precision hardware. Someone else mentioned lasers, but even the little laser pointers scare the bejeesus out of me, and I certainly wouldn't advocate making a TV out of 'em.
*sigh*
Now, about that array of microscopic thermocouples to use as an air conditioner / power source....
d.
(anyone ever think it might be useful to have a "crazy ideas" website to discuss, well, crazy ideas?)
Something I just thought of:
Maybe the edges are blurry because most TVs and monitors have curved glass fronts (especially cheap TVs) - perhaps using a WEGA or some other flat tube might help things? I know that the actual image may be "flat" - but there is a lot of glass it still has to pass through, thus possibly distorting it when you magnify it?
Reason is the Path to God - Anon
Offtopic? I didn't see him talking about shoes or anything else not directly related to the repeated topic.
I'll meet you in MetaMod.
Actually, TV's _do_ have pixels (except they aren't called pixels, but instead "dots", hence, "dot-pitch ratio", which gives the distance between adjacent dots).
Each dot is formed by a thin piece of material called the "electron gun shadow mask", which is basically a very fancy method of saying "a piece of thin metal with lots of precisely placed holes in it". This mask is swept on the back by the electron stream from the "electron gun" in the back (actually, three different "guns" are used, one for each color R, G and B). As the beam passes over the hole, it lights up a corresponding dot of red, green, or blue phospor, which glows in the proper color. This beam is varied in intensity, to change the color level of each dot, to give the wide variety of colors (interesting point - most TVs aren't balanced to pure white, but rather to the blue end of the spectrum, adding blue to a display makes it look brighter to our eyes, but purists have issues with it - also note the same is used in laundry detergent). These dots are very small, and close together, but they exist nonetheless. If this mask wasn't used, extreme smearing would result (now, your statement is correct prior to the mask, but not after it). One other thing, some picture tubes use a grid of vertical wires as a mask - not sure how it works, but I would imagine it is similar, but with less interfereing, and no holes to create pinhole camera electron beam distortion effects, there exists less blurring (ie, the beam doesn't stray from its phospor dot onto adjacent dots). I am sure there is a good FAQ on this out there.
If you want to "see" these dots, up close, take a magnafying glass and look at your monitor or TV, or, alternatively, get some beads of water on your TV, and you can see them (badly, of course).
Reason is the Path to God - Anon
All that remains is to decode the video signal for processing by the projector. In a simple mode, you might even be able to simply take the HSYNC and VSYNC signals and, essentially, use them to mark the edges of your scanning motion, then simply vibrate the mirror back and forth within that time frame. (this is hard to describe, but hopefully it'll make sense to some of you).
:).
An easier way to do this is to use two spinning mirrors to do your scanning. The problem with this is that you'd need to buffer and re-send the image data, because your "blanking intervals" will be much larger than your display time under this scheme. If you don't mind hacking CRTC settings and are using a computer instead of a TV, you might be able to get your video card to drive its monitor port with this kind of signal instead (had a lot of fun making video cards do things they were never intended to a couple of years back).
You'll also need to have the spinning mirrors fairly far from your projection screen or wall to avoid distortion (you're scanning at constant angular frequency, not constant linear speed on the wall). This makes sych problems worse (blanking interval is that much larger, because you're using that much narrower a wedge of the circle the beam is scanned through).
Electronics to synch the mirror rotation to the synch pulses is easy to build. Use a classical control system with extra damping. $2 worth of electronics to clean up the input signals and $1 worth of electronics to control the speed of the mirror-spinning motors.
Now, the big problem (as others have pointed out) is that you must deliver enough power to your LEDs to brightly illuminate a large patch of wall (or screen, if you prefer). This means shelling out tens of thousands of dollars for a high-power krypton laser (so you get R/G/B from one laser), some decent optics (gratings to separate out the colours, mirrors, etc), and "three accousto-optic modulators" (devices that modulate a signal on to a laser beam). This will probably be cheaper than your laser, but that's only because the laser is bloody expensive.
Still a very fun project; just not a cheap one
The scanning would have to be very fast.
r trayal/ that suggests doubling the 24 fps by simply displaying the same image twice in a row would get rid of most of the flickering.
CRT screens have colored phosphors on the inside of the screen that glow after being hit for an instant with a stream of electrons. The phosphors have a characteristic 'persistance' which is how long they continue to glow after being stimulated by the electron beam. However, your wall (or bedsheet or projector screen) has no persistance, so you would have to scan your beam across the wall somewhat faster than the electron beam gets scanned across the TV screen, or the image would flicker.
We know from motion pictures that the human brain can be fooled into seeing uninterrupted motion if a picture is cycled in front of us at 24 frames per second, but I don't know what the duty cycle is. There is an interesting paper by Charles Poynton at http://www.inforamp.net/~poynton/papers/Motion_po
Of course the easy solution would just be to use one red, one green, and one blue LED, each focused into a beam, and use portable gravity generators just in front of the beam source to sweep the beam across the wall!
Chris Owens
Santa Clara, CA
factotum@pair.com
It's ammusing that this is still floating around the net. First time I remember seeing it was back on my 286 when I downloaded AcidWarp. Sure enough, the docs are still on Noah's site.
http://www.noah.org/acidwarp/warper.html
actually, laser printers work much the same way. the paper rolls across a drum while a laser horizontally scans across the page. the laser bounces off a rotating mirror (called a roof mirror); this mirror is typically hexagonal- or octagonal-shaped.
it seems to me that you could do the same sort of scanning setup with a laser/lasers. (1) mount the laser(s) on a rotating drum like a VCR head. the VCR head has the additional plus of being a rotating transformer so you could get power to the laser(s). (2) rotate a roof mirror perpendicular to the rotation of the laser(s). this would produce a helically scanned image which would have to be rectified through a cylindrical lens of some sort. maybe you could curve a frensel lens to the correct radius of curvature. anyway just an idea.
What about instead of vibrating a mirror (which would as you said cause compression waves in the air and send pretty substantial vibrations through the machine (which could then travel to the leds throwing their focus off, but I digress). Why not have a box with mirrors on the outside and rotate it . Because you'd have four mirrors you'd only have to rotate it at 7.5 rps, you'd counteract any vibrations (assuming you balance the box right) and you'd get a smoother motion to boot (no slow down at the extremeties of the pictures, its hard to vibrate something in a manner thats not sinusoidal (though sinusoidal motion in that mirror could be counteracted by a cylindrical mirror afterwards but again I digress)).
The problem with using a row of 640 leds is that you once again have the fixed resolution problem (at least horizontally). I don't know if it would be feasable to rotate a miror box at 3925 rps (to do the horizontal scan with one led) but it would solve that problem.
>Now take that and multiply it times your worst possible dream to get pixels the size of green peas across the wall in your 100" display
:)
YOU MIGHT NOT LIKE THAT, but for me, it's the only way to actually see my dick with a webcam
Not enough millicandella (or candela) output, I'd suggest R G and B lasers to do it, but that would be cost prohibitive... but REALLY bright and nice color balancing.
--- Metamoderating abusive downgraders since my 300th post.
Afraid the Fresnel lens will degrade the quality of the image from your expensive LCD? Try this Bausch & Lomb lens--it appears to be a non-Fresnel, so it doesn't have the lines that could cause some quality loss. You could end up creating a better quality product than a $4000 LCD if this lens works the way I think it does.
Some video source thoughts:
-- 7-inch 16:9 LCD (I don't know where the 7 inches are--I think they're horizontal) being offered to Playstation/PSX owners
-- good source of variety of LCDs?
-- there are several 5-inch TFT NTSC LCDs available for use with the Playstation/PSX (some better than others)
If I weren't able to get good resolution out of the 16:9 version, I'd rather use a VGA LCD at ~$260-350 any day with the NTSC LCD prices Best Buy and Radio Shack charge.
Final thoughts on the dimness issue.. With an LCD, you should be able to remove the reflective backing (ever so carefully, pack a UV-protectant clear sheet of plastic over the back of the device and pump some flourescent, arc, or other bright lighting through it.
Some problems foreseen:
-- may take some experimentation to find the light that irritates the eyes the least
-- may need two settings for day and night
-- be very cautious as not to create a fire hazard
I don't think so....
If you have 3 LED's, RGB, and you want to use a moving mirror to project their light, you suddenly have two big problems:
1. At 640x480, each pixel will be 1/307200 of the brightness of the non-moving LED. In other words, imagine how those little LED's would look spread over such a large surface area.
2. You have mechanical problems. Let's assume that you use rotating mirror assemblies on an equalateral triangle configuration so that one revolution of the motor = 3 scans across the surface. The vertical scanning mirror will need to spin at 20Hz. Not too bad. The horizonal scanning mirror will need to spin at 9,600Hz (480 scanlines x 60 frames / 3 for our mirror config). Trust me when I tell you that you can't buy normal motors that move that fast without it being sealed and within a closed and tightly controlled environment (think : inside of a harddrive)
Now, you can make the arguement "Well! Let's use a row of these LED's to act as a single scan line and we can fix both of those problems." Well, not so fast, sparky. Your $6 in LEDS just became at least $3000 in LEDS and you've created an ENORMOUS amount of mechanical, heat, and electrical problems for yourself. Can you even comprehend how much power 1500 LED's (480x3) would take?!?!? It would be enormous.
If you did some research you'd find that mechanical scanning displays have been around since at least as long as electron gun CRT's, but the mechanical problems were either never solved or never solved well enough to make an actual, practical display from.
I admire the cognitive inventiveness, as it kept me awake one night, too. But after some rational consideration of the real problems that it'd create (instead of just asking for help from "EE's"...shame on you! Where's that DIY hacker ethic?) I realized that mentally I was barking up the wrong tree and got back to work fixing my broken CRT projector.
I built soemthign like this in college out of a big old black and white set and a lense from a Xerox machine.
The problem was brightness, it was basicly unviewable except in pitch black. You can up the brightenss by putting a tube transformer in the set but it reduces your picture tube life. (You can also up the brightness by getting a scotchlite screen, but they are serious bucks.)
This one even has diagrams and all.
http://broch.subnet.dk/projector/start.htm
Guys, Why not just buy a overhead project and put your TV in where the globe normally goes? Wouldn't that work? Then you'd have focus ability. Cheers Watto
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I mean sure, 100" sounds impressive... but really, it can't compete with Frank's 2000" TV!
Actuaries - making accountants look interesting since 1949
I hear sunlight pasteurizes that shit to. How long do you have to leave spores in sunlight to kill them?
Anthrax spores have an unusual characteristic in that it has a flat end on the rod that a standard optical analyiser ought to easily be programmed to detect.
The danger seems to be that spores can't be digested by macrophages so they choke up the body. Couldn't Hyperbaric Oxygenation force the spores into active mode whereupon the macrophges' digestive processses might be effective
I think anyone who can't understand why Americans are so upset by 9 1 1 , ought immediately be hospitalized indefinitely, if the loss of six thousand college educated, civilized human beings doesn't impress them, treatment for psychosis ought to begin promptly. How many times must we allow witless savages to repeat this, for no other reason but bragging rights.
A CRT projector of the 3 tube variety uses this setup for several reasons related to brightness. Number one on the list is no slot mask! Each tube is one color. You are not blocking 80% of the electron beam to the phosphor with a matrix shadow mask inside the CRT.
Number 2 on the list is F stop. A large CRT giving off light with a lens far away gets very little light to and thru the lens. Most (about 80% or more) of the light hits the inside of the box instead of the lens. A projector set uses a small set of CRT's so the lens is very close to the CRT getting most of the light thru the lens. The smaller CRT's can easly have flat faces taking care of the focal plane problem also.
Raw Power.. The small CRT's in a projection set are not limited in beam current as there is no shadow mask to worry about overheating. The face of the CRT is gel or liquid coupled to the lense to reduce interelement reflections and aid in cooling. They can put out brightnesses on the face of the CRT's that can be painful to look at unlike a conventional tube.
The last item is when the distance to a projection surface doubles, the brightness goes down with the square of the distance. Doubling the distance to double the size decreases the brightness 4 fold. This is true for both a real projector and the home made variety, but the home made doesn't have the brightness to sacrifice on the larger immage.
With all these factors working for a 3 tube projector and against a single tube, the diffrence in projected brightness is typicaly more than 200X brighter. Translation.. a room with a couple candles in it will typicaly wash out the image on the home made projectors.
The truth shall set you free!
I seem to remember an old DOS eyecandy program called "Acidwarp" and i remember there used to be
a commandline switch that printed a small instruction sheet for doing this with a computer screen.
i thought the idea was pretty cool for projecting
CG onto walls at parties.
Please forgive me if this has already been mentioned, but what about using overhead projector optics with a regular tv? Reasonably self-contained optics, has the focusing hardware, and if you're lucky, you might get one of those fancy roll-around carts that conjures up images of elementary school hallways... :)
"Ummmm..."
WOW, thats hearfelt. Man, I hope you're doing OK, thats quite the story. I hate to be so brunt but Jane is a bitch, get over her. Find someone elso who respects your feelings and loves you back.
Broken Heart,
Detroit
It is related to gravity.. The picture tube has a shadow mask. It is thin. It sags slightly (affected by gravity). It is true the beam is affected by the earth's magnetic field, but distortions to the shadow mask are a bigger influence. Try this at home... turn a large TV around and notice the color shift. This color shift is due to reversing the earth's magnetic field 180 degrees. Now lay the set on it's side or upside down. This color shift is due to both gravity and magnetic field. Notice how much greater this shift is. Only a small portion of the shift is due to the earth's magnetic field. The magnetic field was most noticable on large computer monitors that has a fine dot pitch as the small shift could more easly misallign the beam to the phosphor. Most TV's have large pitch so the magnetic field has a smaller effect on color purity.
The truth shall set you free!
Colored filters? Never seen one. If you buy a set of projector CRT's (visit a repair shop and ask to see a set of used ones) it is about impossible to tell the colors apart. They all have a yellow whitish phosphor and no filter. To keep from blocking the light produced, they use a phosphor that only produces the color of light needed. No filter = no blocked light = brighter image. If you don't have access to a projector tube set, use a good magnifing glass and look at the screen of your TV when it is off. Can you tell the difference between the red, green and blue phosphors? I can't.
The truth shall set you free!
I built a projection TV lens system over 20 years ago with a $10 plastic fresnel lense - it worked (in a very dark room) and I also had to re-wire the deflection yoke on the TV to invert and rotate the image (reference optics 101). It was an interesting experience for a 13 year old ( I still can't believe my mother let me tear apart the TV to do the deflection yoke mod ).
Anyway it sucked 20 years ago and it still would suck today I'm sure....
I was actoually about to buy one of these things off ebay after I found that it was impossible to find the instructions off the internet somewhere. Good job people!
Daddy would you like some sausage?
Now there's an idea! If you wanted to set something on fire without being caught, all you'd have to do is set the lens up someplace (on top of a car sunroof is good) and leave! Plus, you can blind people with the intense sunlight as an extra bonus! I wonder if you could use this in conjunction with some swivel-mounted computer-controlled mirrors to mount a death ray above your doorstep? >:D
Omnes arx vestrum sunt adiuncta nobis.
Who has not as a kid played with lenses, I got my first fresnel lenses from a surplus supply house.
Other then burning leaves and ant's, I found that I could project my B&W TV against the wall.
I have seen other TV to big screen converts, using an old copier lenese....
Having to have a total dark room to use the 100" screen device is not a big deal.
I also have played with the real deal, even the high end units look best in a dark room.
Wise men speak because they have something to say, Fools because they have to say something!!!!
One warning: I've seen plans for doing this that involve using a much higher second anode voltage on a standard CRT, to get an unusually bright image. This can push the CRT over the threshold where it starts emitting X-rays. Bad idea.
Everything I've read about modifying the insides of TVs says even days after power is removed they can store a huge amount of charge. Be careful!
Anyone with more solid info care to comment?
And
here's a FAQ explaining why Northern hemisphere monitors don't work so well in the South
I hope you'll use a condom while your fucking all those people, cause I sure wouldn't want you to breed...
If it don't GO... chrome it. ~ Frank Banks
Is it just me or does this 100" TV project a mirror image ie words are spelled backwards?
You can do this sort of thing - a friend of mine took the guts from a portable TV and put it in an old slide projector - viola! Projection TV. It worked really well... for about a minute. Unfortunately many LCDs degrade when they get hot. However, solve the cooling problem, and you're golden!
.mpg of how to put one together, but I can't find the URL any more... :(
He used to have a
I've been wondering why no-one seems to make any VGA (640x480) resolution projectors any more? If they were available at half the price of the current XGA projectors, they would make a nice projection TV system.
Andrew Yeomans
Believe that and you'll believe that you can use a pinhole instead of a lense.
This still leaves us with the problem of getting enough optical power (light) onto the mirrors from a single set of LEDs. Lasers (contrary to the hilarious post made earlier) would produce alot of light and shouldn't cause "burn-in" unless the mirrors failed.
So far, I'd say that the rotating mirror, combined with a row of LEDs would be the best combination.
They do this for laser light shows.
Uh... expensive does not even begin to describe this set up.
The scanning mirrors have to be ultralight, and verry refined (may be able to skip this since your not using such a pure beam). Then the motors to drive them are EXPENSIVE and FINICKY!!
Now that being said, the best scan rate anyone has ever managed with lasers was about 64 lines (Don't hold me to that, it's been a while), and the control board capable of this is only manufactured by one company, in Orlando (whom I used to work for). Top notch equipment if you can afford it. And even they can't do a video projection for TV yet. (www.pangolin.com)
Moving parts suck.
I would rather be ashes than dust!
One sure way to know if it works - try it.
I built one yesterday evening, after reading Slashdot, using plans I found free on the web.
I bought a sheet magnifier at Staples for $5.50 and spent about one hour with duct tape, a swiss army knife, two medium u-haul boxes and a 19" color television. I used a mirror to project it onto the ceiling and correct the image backwardness.
It does not work great, but it does work - and it was a fun excercise.
I think I'll watch Enterprise on the ceiling tonight!
with a 13" CTV, a cardboard lightbaffle, and a lens from an Opaque Projector!
Of course, without a correcting inverter-lens, all I got was a dim gigantic upsidedown image on the wall and ceiling!
And I got tied of holding the Lens Barrel and the the cardoard!
Regards,
JK
(David Bowman, EVA near HUGE Monolithic Win-PC in orbit around Jupiter) "My God - its full of Malware!"
Cool murder mystery from Analog science fiction magazine, some 20 years ago: Revenge-seeker kills his target by carefully pivoting the computer-controlled climate-regulating windows of the office building across from the target's apartment, turning the building into a giant parabolic sun-miror.
- - - -
The real Tetsujin 28 is a giant robot.
Yeah, but it only shows up as a couple of peas and a pod...
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"