Instructables
Picture of Hacking an old laptop into a 3D projector
If you have an old laptop lying around, and are looking for a DIY adventure, this might be the place for you. I'm going to describe how you can go about building your very own 3D projector !
It's not for the faint of heart, and I can't possibly get into every bit of detail, but I'll try to link all the resources you will need.
For a summarized version, make sure to check out the corresponding post on my website.

It all starts on DIY projector forums, such as Lumenlab (which is now only accessible via the Wayback Machine), DIYaudio, or if you understand French, Allinbox. The folks on these forums pioneered the idea of reusing an LCD screen into a high quality, affordable, videoprojector, by using a very bright lamp as light source and finding the proper optics to make the magic happen !
There are already a few instructables (here, here, and here) based on these designs, and other external resources (here, here and here), so I'm not going to spend too much time on the technical aspects of building a regular 2D DIY projector. Some companies are even selling kits based on those ideas.
A DIY projector is a challenge in itself, but if you're really motivated, you can go one step beyond, and make it 3D !

A first idea is to use two projectors, commercial or DIY ones, place some polarizing filters in front of their objectives, and align the images on the screen so that they overlap. This has also been proposed in previous instructables, in some forums and other blogs.

However if you have only one LCD screen, you can still pull it off, with a little trick.
 
Remove these adsRemove these ads by Signing Up
lbacklund1 month ago
Nice work! I'm quite tempted to build one of my own. Although I have no idea of where to find compatible movies, so I may just go with a 2D instead. Where do you obtain your 3D movies? :)
naimo (author)  lbacklund1 month ago

Hey, glad you're interested in making one !

Most 3d videos come in Half Side-By-Side format, meaning that the images need to be split in the middle to make two streams, stretched horizontally, then stacked vertically into one video playable by the projector.

There are many places to get videos, using the words "3D SBS" in google. Here's an example with demo videos http://www.demo-world.eu/trailers/3d-high-definition-trailers.php.

userTRON8 months ago
I have an Xbox 360 and want to build a projected for it. is there a way to add an av input into this
naimo (author)  userTRON8 months ago

For a regular 2D projector, the easiest would be to do like SuperTech-IT says below, use an external monitor that has the right inputs already instead of a laptop.

For a 3D version, I don't know enough about the 3D capabilities and formats of the Xbox 360 to say, but usually the problem is that top-bottom or side-by-side 3D has images that are half the height or width, so they can't be projected as they are.

ASCAS8 months ago

Awesome project! Voted BTW :D

You've inspired me to turn my 4inch HD scrap screens to a smaller scale 3D projector!

naimo (author)  ASCAS8 months ago

Thanks ! Congrats for the Hardware Hacking.

It's great to hear that you're thinking of making a projector.

Having small LCDs will be better (than my big 15.4" screen) for the homogeneity of the light throughout the image. Make sure to check the resources about regular 2D DIY projectors, there isn't much difference for 3D except for the splitting of the lenses on the projection side.

Are you going to use two 4inch screens ? It would make things much easier indeed.

When I saw this entry I thought it would be a finalist. It's wicked cool. Congratulations!
naimo (author)  PaulMakesThings8 months ago
Congrats to you too, thanks to everyone who voted !
SuperTech-IT9 months ago
I like the concept, but I think I'd just hack an old monitor - that way I can just drive VGA input to it from a desktop, laptop, or other device.
Then we don't have to worry about uploading files and operating the laptop.
naimo (author)  SuperTech-IT9 months ago
Let's say that these can be either pros or cons, depending on the point of view. It's nice not to have to rely on another device, and to be able to store your movies on the hard drive of the laptop.
Granted - gotta love the idea of a totally mobile 3D theatre!
Back yard parties etc. especially if you have tons of the $1 polarized glasses for everyone! Talk about being the hit of the party!

I used to DJ, and I have a standard projector and 71 inch portable screen (rolls up) - and there's nothing better than being able to roll up in any car with this level of equipment and a 1200W amp and speakers on tripods.
Then you pull a laptop as your source and look at people think you are nuts...til you rock it.
Hook up the DJ-2-Go mixing console for Virtual DJ, and blast it.
I love the portability idea - but in a home environment and from a cost perspective, I'd go with a monitor.
If you wanna take it anywhere, your idea rocks.
dunnos9 months ago
I need this. Since I study mechanical engineering I have access to a LOT of pretty tools. I don't know yet if i'm going to make it 3D though.
Do you think a projection screen makes nice curtains? :D
Also, can I just use an LCD screen? I have the perfect donor standing in a corner somewhere.

I really like this project, good job!
naimo (author)  dunnos9 months ago
A projection screen makes great blackout curtains, if you have one that fits your windows perfectly !
I used a laptop because that's what I have, but an LCD screen would work too.
jareu9 months ago
I've always wondered this, but do LEDs work better in terms of heat output and brightness for Projectors like these? I have an old projector which is very noisy and I was thinking about installing LEDs instead. have you experimented at all with using different types of light?
naimo (author)  jareu9 months ago
I haven't tried with other types of lights, but people regularly use LED sources for this kind of DIY projectors based on an LCD screen. It needs less cooling and takes les space, but sometimes the color is not as good.
I've been a member of Lumenlabs (before they shut down) for a long time, and never have seen anything quite like this. It seems your process is straightforward, the end product is attractive, and the end goal has been met.

A few questions though. First, I'm guessing that the laptop you used is a 1280x768 or 1280x800 resolution -- is this correct? If so, I'm wondering if you're running an interpolated resolution to match the source resolution (meaning 1080p/720p interpolated), or if you are simply running the screen with both images set to the native resolution (meaning 768x640 or 800x640)? Also, what software packages are you utilizing in this build to produce your images? How would having a slightly newer model laptop affect the quality (is there any noticeable lag since the processor now has to generate two separate, tandem images)? Would you recommend jumping up to a wuxga screen to bring the resolution up? Or would the cost differential be too great to be feasible?

Sorry, I know it's alot of questions, but I'm seriously considering utilizing your basic design -- as I said, I've been a long time member of LumenLab and DIYAudio, and I've been waiting for a project such as this. Thanks in advance
The 3D video is actually just a 2D video with the left eye footage on the left side of the screen and the right eye footage on the right side. This project uses lenses to take an image from either side of the screen and project it onto the same space a few meters away. So in answer to your question, since the laptop's screen must display 2D footage for both eyes at once, each field can have a maximum screen space of 1/2 the resolution of the LCD monitor. EG, if it was a 1280x760, each eye would have a screen space of 640x760. This project would most likely be better suited to a 1920x1080 res display, so I'm thinking of even stripping down an old monitor to do this. That way you could have the HDMI input as well.
naimo (author)  jareu9 months ago
Indeed, captain, in my case I have a WSXGA+ LCD (1680x1050), so each image is 1050x840 max (the LCD is rotated 90degrees), which is still better than 720p by the way. Going to higher resolution would give you more pixels, but there are other aspects to improve beforehand in the design to get a better image, like optimizing the light intensity and homogeneity (potentially by using two lamps instead of one). As you probably know if you're a lumenlab alumni, the larger your LCD screen, and the shorter the focal length of the first fresnel (F1), the more vignetting you get (dimming of light in the corners).
So I would still start with a lower resolution screen, but in a size that allows to upgrade to higher resolutions in the future.

To answer your software question, you could use something like Stereoscopic Player, or Bino on linux, to convert from say Half Side-by-Side to the proper format in real time, but that's not possible on the old laptop I'm using, the CPU (or I guess GPU) doesn't have enough oommf.

Instead I'm using AVIsynth and meGui to convert my videos in advance. I stack the two channels of the stereo stream and the appropriate black spacers into one 1280x800 or 1680x1050 video, encoded at a very decent quality, that I can play in any video player. I'll add a step to the Instructable about the software side of things when I can.
Thanks for the answer! All your answers were exactly what I was expecting -- kinda nice when that happens, lol. The software is the only lagging factor for me... I understand the projection concepts well, but am lacking in software knowledge for video/audio encoding.
Thanks, but this really didn't answer my question, just reiterated what was already in the instructable. And to be honest, I don't know if I agree entirely with what you said about the resolution being best suited to 1920x1080 screen. Think about it -- the closer the native resolution of the panel gets to 1:1 (square), the closer the split aspect ratio gets to 2:1. The more "widescreen" the native resolution, the closer to 1:1 it gets. And although the resulting image will likely be higher resolution, it will have much larger, space-wasting letterbox, top & bottom. Ideally, the image projected should utilize the most available area, width-wise, that it can. Otherwise, you're sacrificing image quality.

Personally, I would probably go about sourcing a panel that would split to a 1.78:1 or 1.85:1 ratio, so as to use all of the available pixels to produce the image. Something like a 1280*1024 panel (5:4 AR) would be closer to the ideal, as the resulting split aspect ratio = 16:10 (or 4:2.5). If you lay equal length pieces (say, 10' long) of screencloth on top of each other, the only variable being the height based on AR, you'll see that 16:10 is pretty much the most appropriate home theater ratio available, due to the general limitation of width, not height, in most average homes. Also, most films are still being made in 1.78:1 format, or 1.85:1, and so far not too many have been made in 2.4:1, though it is picking up speed.

So compare the resolutions at the given width. If you have a 10' (120") wide (note: NOT diagonal) screen, at 16:10, the usable screen height is roughly 6.5'. Let's say this is produced on a 1280*1024 native LCD (1024*640). With a native resolution of 1920*1080, the split AR becomes 5:4 (1080*960), which in a 10' wide screen equates to a usable screen height of 8'-10". This in turn is a lot more wasted light going through letterboxes, rather than through an image, when anything much wider than 4:3 content is viewed. If you're going to the trouble of making a project like this, chances are you're making it to be as efficient as it can, so you don't have to oversize the bulb, etc. And light-loss is inefficient, plain & simple. If you can concentrate all of the light produced through active pixels, then your "light-to-pixel" efficiency will be higher, ie: a brighter picture for a given bulb wattage.

Let's talk pixel density for a second. Pixel density (at the screen) varies very little when differentiating between the 1280*1024 and 1920*1080 screens. The pixel density for a 1080*960 split resolution on a 10' wide screen is 9 ppi (again, at the screen). The pixel density for a 1024*640 split resolution on the same screen is 8.53 ppi, a difference of less than half of one pixel per inch. To me, I'd rather save the 4:3 content for watching on a 16:10 screen, rather than the other way round.

Also, I'm not entirely sure what "old" monitors are to you -- HDMI hasn't been an marketed option on monitors for all that long (here come the flames, I'm sure). A 1920*1080 monitor, if you can find one that's NOT a laptop screen, and is under 17", is going to likely run you a pretty penny. Keep in mind, as well, that many devices that SAY they are 1080p are not, in actuality, FHD. Many devices have interpolated resolutions that really shouldn't be called HD. All the interpolation does is read the HD signal and remove pixels to fit the native resolution of the screen. DVI is/has been a much more prevalent interface on computer monitors, as it was partially a replacement for VGA, but has better quality potential. So honestly, I'd find an older 17" monitor (1280*1024) with DVI input and a decent refresh rate and contrast ratio (5ms or less refresh, 1000:1 or better CR).

If you really want HD and HDMI interface, buy a Gen.2 iPad Mini, or if you don't need the HDMI, a Kindle Fire HDX 7" and hack it... the native resolution of the Mini is 2048*1536 (1536*1024 split, 3:2 split AR, <1080p HD), and the Kindle is 1920*1200 (1200*960 split, 5:4 split AR <1080p HD), so the pixel densities would be far superior, not to mention you could build a smaller enclosure, with a smaller lamp, due to the LCD's ultra-compact form factor. The Kindle Fire HDX 8.9" should also work, and WOULD produce a FHD stereoscopic image, due to its slightly higher resolution of 2560*1600 (1600*1280 split, 5:4 split AR, >1080p HD).

No idea if those devices are even hackable enough to make it work. Food for thought. Sorry for the long post. Got thinking about it, couldn't stop.
nfolken9 months ago
I've never played with wave plates before. You are using 2 half wave plates to rotate the polarization for each eye by 45 degrees in opposite directions. Does this cut down on light levels very much? Also, this would only work for iMAX 3D, which is linearly polarized. I think most people in the US are more used to Real-D, which is circularly polarized (doesn't mess up if you tilt your head). I just read that it would be easy to create this using quarter wave plates instead, so now I'm inspired to get out my old LumenLab style projector and start rebuilding! Also, thanks for the tip on the Ikea bowl, I had been looking for a good replacement reflector.
naimo (author)  nfolken9 months ago
In theory, compared to doing the same by using polarizing filters directly, where half of the light is filtered out, using half wave plates should only result in a few percent loss corresponding to the absorption only. At least that's my understanding.

If you want to use quarter wave plates, make sure that you get ones that have the same retardation properties on the whole visible spectrum. I don't know if that's possible without spending a fortune. Otherwise you'll get slightly different polarization depending on color, your glasses won't be able to filter the images properly and you'll get crosstalk.

I also wanted to use circular polarization initially, but because of this problem I had to switch to half wave plates, which still have variation with color, stacked with linear polarizers which clean up the light polarization.
cliffyd9 months ago
very nice
iamchrismoran9 months ago
What a great idea.
Given ownership of a preexisting laptop, what might this project cost? How crisp is the projected image? Most of the projects I've seen (here and about) for even just a 2d laptop projector generally have blurry pictures.
naimo (author)  iamchrismoran9 months ago
Thanks, it's really nice to see the project receiving so much interest.

Given pre-ownership of a laptop, the next most expensive part was actually the passive 3D-compatible screen, in my case a Da-Lite Silver Matte, that I bought for $115. People have been trying to make their own screen either using metallic paints or even anodized aluminum sheets, with various level of success, but it would certainly make it cheaper.

Next most pricey is the lamp and its power supply. The latter, which is called a ballast in the case of metal halide light bulbs, is also used a lot in aquariums and for indoor growing (hydroponics for example). I was lucky to get a used bulb and ballast from ebay for $45.

Then, the smaller things can add up if you buy them new. However, fresnel and triplet lenses can be scavenged from overhead projectors, fans from old desktop computers. I don't know of a good source of polarizing filters, and especially of half wave retarder films.

As for the quality of the projected image, it doesn't have to be blurry. Here's a link to a former lumenlab post where the (2D) projector uses a wuxga LCD screen, and he has some pretty amazing results. Mine doesn't come close to this quality, I was mainly focused on making the 3D part of things work.
whitepaper_019 months ago
Gr8 I'ble. Clear and Concise
Hope I get some time to have a crack @ it!!
cool project. Nice idea of using same LCD for both views.
graham6419 months ago
An excellent instructible. Clear writing, good photos and really clever application.
andrea biffi9 months ago
Oh my gosh, that's a huge project!
audreyobscura9 months ago
So cool! Nice build too! Thank you so much for sharing this, it was helpful to learn about the polarization of images!