Projection Microscope From Broken Projector

The idea for this instructable came from the Build My Lab Contest

I was over at a friends house and he had a broken projector that he had pulled from a dumpster, we of course started to disassemble the device.

It became immediately clear that it was abandoned because of a broken bulb. While some LED projectors are now on the market, the majority still are and have been based on a big honkin' bulb to project an image. The big disadvantage is that an incandescent bulb is typically used, which puts out a lot of heat and eventually burns out.

These bulbs are then very expensive to replace, and as projectors get cheaper, it is often easier to buy a new projector than to replace a bulb on a previous generation model.



From the projector I pulled out a whole bunch of goodies for use in future projects. Lots of centrifugal fans, used here for their small form factor, and usable in many projects. There were also two AC to DC converters, one for the electronics in the projector, and one just for the bulb. The different optics in the device were also pretty cool, with some polarized lenses each filtered for red green or blue.



The most important piece (for this instructable) is the actual lens of the projector. 

Step 1: Brainstorm!

This is always one of the most fun parts of making something, granted the ideas don't always make it to production.

Step 2: Gather Materials & Tools

Materials:

Projector lens assembly. Dumpsters and ebay are both great resources. A friend of mine saw that a nearby school was throwing out a bunch of electronics and took a look in the trash (various laws on dumpster diving, it was perfectly ok when he did). 

Aluminum extrusion for mounting everything. The aluminum extrusion was bought for another project and seemed like the most practical thing that I had lying around. This is great stuff and super practical for a whole range of uses, I've seen it used for everything from a bicycle at school, to a mobile platform for a rocket engine at my old job. 

Light source. Here I used a flashlight, but a small directional lamp would have been more practical since I would then not have to worry about batteries (but would need wall power, so this decision depends on your intended usage).

A sheet or towel. Always helpful for teardowns, it ensures that you don't have any little pieces running away, and limits the maximum extent of your mess.

A flat white surface. Needed to project the images onto, here I used corrugated plastic, but could have used any number of things. Again it was about using the materials that I had on hand.

Finally having a small set of different size nuts and bolts is very helpful. I had to wait for some m4 bolts to come in before I could mount up the lens. The sizes that you need will be dependent on the lens assembly that you get, and the design of other parts.

Tools:

A screw driver or allen key for the bolts that you're using.

Pliers or a wrench to hold nuts in place for tightening.

While I do use a 3D printer in this project, everything necessary could just as easily be made out of wood. Given some thin balsa wood, enough wood glue, and a hobby saw, each of the 3D printed parts could also be made by hand.

An electric drill was key to drilling the different mounting holes throughout the project. Because of the 3D printer, I could have simply made all of the parts with the holes already inside them, which would have negated the need for a drill.

Other:

Dubstep. I always find that It's the best to listen to dubstep while doing engineering.

Step 3: Dis-assembly

For dis-assembly I always recommend working on a sheet or towel. This way any small parts will be caught and easily recovered. Taking the projector apart wasn't too tricky. Preventing scratched to the lens is something to be mindful of.

Make sure to be careful of the large capacitors in the power supply. These can stay charged even when the unit has been unplugged for an extended amount of time. Gloves are always a good precaution when taking something apart that could have sharp pieces, and even more so if there is a risk of shock. Of course all safety gloves are not created equal, so make sure you are using a pair that is rated for the task at hand (get it).


I inevitably decided to make this instructable after the teardown so I do not have any photos of the process, guess I should always have a camera rolling!

Step 4: Measure Optics

The reason that I'm not including specific dimensions in this instructable is because each type of projector will have a lens with a different focal length. Before designing any mounting parts, you'll need to see how far from the lens a sample needs to be held in order to focus the light at the distance you want to project it. All you need for this is the lens, a light, and some clear tape to act as the sample. I chose clear tape (like kapton or scotch) because it's very easy to stick your finger print on it for a sample (we'll worry about all the cool stuff we're going to look at with the microscope later).

While this dimension is not explicitly present in the design, it effected how I designed the lens mount, since I had to ensure that the sample could be brought close enough to come into focus. The lens itself has a focusing ring, so keep in mind where that ring is while making measurements. Since the design is literally open ended (in that it will project the image on a surface not part of the apparatus), the focal length is less important than if we were designing a true microscope.

Step 5: Measure Other Dimensions

The important dimensions here are the diameter of the flashlight, and the diameter of the lens housing, and the length of the part of the lens assembly that will attach to the mount . We can ignore the bolt pattern for the lens mount if a drill is accessible and you're comfortable using it.

A vernier caliper would definitely be the best tool for this job, but one can always make do by using string or paper, then measureing it against a ruler.

Step 6: Modelling

Here I used tinkercad. while I have access to solidworks at my job, I thought I would try out this free online software.

Tinkercad has its limitations, and my design was definitely modified as a result. That being said, engineering as a whole is simply modifying your ideas in order to build them with the tools that you have; the key is to not lose the awesomeness of those ideas in the process!

There are three parts to model (and two are the same!). First is a mount for the lens assembly. Then the mount for the flashlight (or other light source) . there were a number of ready-made flashlight holders on Thingiverse, but I thought this would be a good first model to make with Tinkercad. Finally, there is the specimen-holder-holder, aka the part that will hold the acrylic/glass plate that the specimen will rest on. Thankfully, the lens mount also works perfectly for this part.

I chose to omit the bolt holes in each of these parts, because I would it easier to drill them after printing. I felt that this gave me greater accuracy (I was able to trace the holes for the lens mount from the lens mount itself), and the bolt holes came out nicer without having to print over a void.

When making these models we need to ensure that our other parts will fit into them. I did this by making each key dimension a few mm larger than it needed to be. This not only made up for the sloppiness of my measurement, but also gave a good margin of error for any shrinking/warping that the 3D printed object might do.

Find the files at Tinkercad under the same username.

Step 7: Print It!

Anyone who has used an FDM printer (aka filament extruder) knows the trials and tribulations of their use. Hang in there kitty! I will say that I had many fewer issues printing with PLA than ABS, and it smelled wonderful.

In the end I printed two of the flashlight mounts, and two of the lens/speciment holders. 

Step 8: Assembly

This should be the most straight forward step (hopefully this whole instructable is, but you never know). The basic sequence is measure, measure, mark, measure, drill, mount, repeat.

Step 9: Adjust

Remember here that you have three variables for bringing something into focus:

1) distance from specimen to projection surface

2) distance from specimen to lens

3) focus of lens

Where the flashlight sits can also be adjusted, but isn't an issue for focus

Step 10: Voila!

Enjoy exploring worlds unseen! Or on a more practical level, this device can help you view fingerprints, look a microscope slides, and maybe even look at a bug or two if you can get them to stay put for long enough.