Introduction: Hacking an Old Laptop Into a 3D Projector

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.

Step 1: The Trick

Picture of The Trick

The trick is to consider the two halves of your LCD screen as two separate screens, that you need to project using separate optics. In my case, I decided to rotate my 15.4" LCD screen so that the height is the longest dimension, and consider the top and bottom halves as separate screens.

It is then possible to place the front Fresnel and  objective lenses such that the projected images are superimposed on the projection screen. This uses a concept called lens-shift, which says that you can move around the projected image from a fixed source by moving the lens in between.

It's relatively basic geometry and linear optics : first calculate the throw of your projector and the size of your projected image using the same equations as for any 2D DIY projector, then determine the position of the center of the fresnel and objective lenses (triplet lenses) that will offset the two projected images so that they overlap as in the pictures I uploaded.

Once the position of the center of the lenses has been calculated, you can then cut the front fresnel lenses so that they cover the whole LCD screen when placed next to one another. This way you can make use of the whole surface of the LCD, and not lose precious pixels.

The values shown in the images correspond to my 15.4" LCD screen, my 330mm focal fresnel lenses and 327mm focal objective lenses. However, the dimensions of the box and relative position of the different optics depend on the dimensions and specifications of the elements you have, so don't just reuse those values, you'll have to recalculate them.
I have a little script on my website (it needs the Mathematica plugin, sorry), which allows you to play with different parameters and see how it changes the dimensions of the box and the relative positions of the optics.

Step 2: Material Needed

Here's what you'll need for this project
  • Your old laptop, with a decent quality (color!) LCD screen, its power supply
  • Wood panels (plywood, MDF)
  • Lamp and its power supply (metal halide, LED, your call) : good color and intensity are the main requirements
  • Fresnel lenses, one on the lamp side, two on the projection side : make sure to get them in the right size and with the right focal length
  • Two triplet (projection) lenses : get the right focal length depending on you projection throw and image size
  • Reflector and condenser lens : to increase the light intensity and homogeneity
  • Lexan sheet to protect the optics from the heat of the lamp
  • Cables, switches, connectors
  • Two or more computer fans and a matching power supply
  • Filters : half wave plates and linear polarizing films
  • Aluminum and wood scraps, fasteners for mounting the different elements
  • Wood finish (oil, varnish...)
  • A projection screen compatible with passive 3D (like a Dalite Silver Matte)

Step 3: Building the Box, Mounting the Lenses

Picture of Building the Box, Mounting the Lenses

After selecting your optics (fresnel lenses, triplets), based on the size of your LCD screen, your projection length and screen size, you should have a good idea of the dimensions of your box. I built mine in 1/2" plywood for the side panels, and 3/4" MDF for the front and back.

Cut and mount your Fresnel lenses inside the box at the right position. 
The fresnels must be cut according to your calculation in step 1. Since they're made of plastic, anything will work, really. Just be sure to protect the part of the lenses that you will actually use, since scratches and defects might eventually be visible on the projected image. I cut mine at the same width of the box, to be able to just slide them in with proper guides made of wood scraps.

Open apertures in the front panel of your box, and mount your projection lenses. It's good to leave some room to adjust their position at the end, to correct for miscalculations and inaccuracies in the fabrication. For that purpose, I allowed the small panels that hold my triplets to move up and down thanks to knobs that I can tighten manually.

Step 4: LCD Stripping & Mounting

Picture of LCD Stripping & Mounting

Take the LCD screen out of the laptop. Very carefully, strip the LCD screen so that you are left with only the PCB and the LCD sandwich itself. Check this Lifehacker link, or this engadget link for more information on how to strip a LCD screen.

Mount your LCD screen in between the fresnel lenses. There are many great ways to do this in the 2D projector resources I mentioned. I once again used some wood scraps, cut in the right shape, to maintain my LCD screen.

With the fresnel lenses and LCD in place, you know have two separated compartments in your box. The lamp is in the back compartment, so I suggest you place all your electronics (laptop, power supplies) in the front one so that they don't suffer from the heat of the lamp. However, make sure that the electronics are not in the way of the light !

Step 5: Fabricating the Lightbox

Picture of Fabricating the Lightbox

The lightbox is one of the crucial elements of any DIY projector. Once again the resources I mentioned on 2D projectors will help you design it based on the type of lamp, the reflector and the condenser lens you have.

After making a quick 3D model of it, I built mine in 1/4" aluminum sheet, cut using a waterjet. It holds the lamp socket, the IKEA bowl that I use as reflector and my 9mm diameter condenser lens.

At this point, a good sanity check is to verify that you obtain two images of your lamp by your set of lenses, which are roughly focused at the location of your triplet lenses. This will tell you if your fresnel lenses are well cut and positioned.

You can see that I mounted two fans at the back of the box, which extract the heat produced by the lamp. The air enters through an aperture on the side of the box, flows in between the LCD screen and the fresnel F1 to cool these elements first, before entering the back compartment of the box.
Cooling is a crucial part of any DIY projector using anything else than an LED lamp.

Step 6: Testing the Projection

Picture of Testing the Projection

Once the lamp, lenses, LCD and laptop are in place, it's time to test the projection.

First, determine the throw by obtaining the best focus of your image on the screen. You should be able to see the pixels of your LCD screen since they are now magnified.

On the software side, regular 3D video streams have to be edited so that the images corresponding to the right and left eyes are displayed on the two halves of the LCD screen (consider it as two screens). AVIsynth is a great utility to do video editing, and in particular to take two video streams and stack them vertically or horizontally into one combined video.
You can start by making a static test image to be displayed fullscreen on your LCD. I made one with a few rectangles and a letter A or B in the center, to verify my alignment.

If you calculated correctly the position of your lenses, you should be able to obtain, on the screen, a good superposition of the images formed by the top and bottom halves of your LCD.
If this works, congratulations, the hardest part is done !

Step 7: Adding Polarizing Filters

Picture of Adding Polarizing Filters

So that the image can be watched with regular 3D cinema glasses (like IMAX 3D), the light passing through the two objectives has to be polarized in perpendicular directions.

The good news is that the light coming out of our good old LCD screens is already polarized, so we just need to rotate the polarization in two different directions to obtain two images polarized perpendicularly. The next good news is that this is exactly what a half wave plate does !
Just stick two pieces of half wave film before or after your objective lenses, and rotate them around until the light is correctly filtered by your 3D glasses. Since these half wave films are usually slightly chromatic (they rotate the light differently depending on the color of the light), it is probably good to add a linear polarizer after the wave plate to filter out any light that is not properly polarized. I hope that the uploaded picture makes things clearer.

And there you go, all you need is a projection screen compatible with "Passive 3D projection" (ie based on polarization of the light), and you'll soon be able to watch your favorite 3D movies at home.

Step 8: Finishing the Box, Mounting the Electronics

Picture of Finishing the Box, Mounting the Electronics

When everything is in working condition, it's time to finalize the box.

Properly mount the electronics in the front compartment, where it's cold, secure the cables along the walls so that they don't move in the path of the light. Add some switches and electrical connectors to be able to operate the projector without having to open the box, and cut out some apertures to have access to the USB and VGA ports of the laptop, to make it possible/easier to copy files, start videos, etc

Step 9: Taking It All Apart, Staining the Wood, Adding Details

Picture of Taking It All Apart, Staining the Wood, Adding Details

After putting so much efforts in building a kickass 3D projector, it would be too bad to leave it unfinished.
Take it all apart ! Use some nice wood varnish, or your favorite wood finish and make it pretty.

To decorate the air intake apertures, I cut some small wood pieces and glued them to the panel to make a nice looking ventilation grille which prevents light from coming out.
I also added some hinges to be able to open the top panel more easily.

Step 10: Putting It Back Together !

Picture of Putting It Back Together !

Here you go ! A functioning 3D projector built from a hacked laptop.
I know that I am missing a lot of details. However most of them are not specific to my 3D version of a DIY projector, and can be found elsewhere in the links that I provided.

For the 3D-related details, I'll try to add some over time and keep updating this instructable, and I'll be glad to answer any questions in the comments. In the meantime, I wanted to put this project out there, hoping that it will be of interest to some DIYers in quest of a challenge !


balb (author)2015-06-27

Happy sethiya (author)2015-03-30

it is so cool

dean.husan (author)2015-01-26

Searched for 3d projector diy, and found 3d diy projector, good work man... well i have an i5 old laptop that i could use, and a atx psu.... so kinda half way there haha... i have a few questions, if you could answer that would be great (or anyone who has knowledge of them)

1st. I would like to hook my xbox 360 up as i play alot of splitscreen, is there software with the function 3d top and bottom, where it could merge the the pciture as one, scaling top half and bottom half in to one?

As most 3d tvs have this function, and xbox games have the function dual play.

2nd. I know this can be done with 2 projectors to make tje 3d effect. We all know most of th cheap proje tors in china have really bad light and what n9t, wouldnt it possible to buy some and put better equipment in, light, lens and so on?

For now that are allthe questions i have untill i get paod and try this bad boy out. Thanks for the tranlation versio and link. Dj

PiyalS (author)2015-01-11

is there any software that play top and bottom mode of any file ? then the software part will become more easier ..

PiyalS (author)2015-01-11

hello naimo will this type of video(top and bottom) is the only file for this type of 3d projector that u have made?

PiyalS (author)2015-01-09

so in this technique we can see anything in 3d . even can see live football matches in 3d . plz correct me if i m wrong. thank u..

naimo (author)PiyalS2015-01-10

The video has to be filmed in a special way (usually with two cameras) so that it can be seen in 3d later. Or sometimes the 3d effect is added in post-production on some movies (especially animated like the lion king). So regular TV won't work.

If it doesn't exist yet though, I'm sure we'll have live sports in 3D in the near futur.

PiyalS (author)naimo2015-01-11

ok i c brother..

lbacklund (author)2014-08-14

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)lbacklund2014-08-26

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

userTRON (author)2014-01-19

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)userTRON2014-01-20

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.

ASCAS (author)2014-01-10

Awesome project! Voted BTW :D

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

naimo (author)ASCAS2014-01-14

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.

PaulMakesThings (author)2014-01-07

When I saw this entry I thought it would be a finalist. It's wicked cool. Congratulations!

naimo (author)PaulMakesThings2014-01-08

Congrats to you too, thanks to everyone who voted !

SuperTech-IT (author)2013-12-13

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-IT2013-12-16

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.

SuperTech-IT (author)naimo2013-12-16

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.

dunnos (author)2013-12-13

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)dunnos2013-12-16

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.

jareu (author)2013-12-12

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)jareu2013-12-16

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.

CaptainPointless (author)2013-12-10

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

jareu (author)CaptainPointless2013-12-10

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)jareu2013-12-11

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.

CaptainPointless (author)naimo2013-12-11

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.

CaptainPointless (author)jareu2013-12-11

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.

nfolken (author)2013-12-11

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)nfolken2013-12-11

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.

cliffyd (author)2013-12-11

very nice

iamchrismoran (author)2013-12-10

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)iamchrismoran2013-12-11

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_01 (author)2013-12-11

Gr8 I'ble. Clear and Concise
Hope I get some time to have a crack @ it!!

Antzy Carmasaic (author)2013-12-10

cool project. Nice idea of using same LCD for both views.

graham641 (author)2013-12-10

An excellent instructible. Clear writing, good photos and really clever application.

andrea biffi (author)2013-12-10

Oh my gosh, that's a huge project!

audreyobscura (author)2013-12-09

So cool! Nice build too! Thank you so much for sharing this, it was helpful to learn about the polarization of images!

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