Smartphone Microscope

The focus lens of just about any laser pointer will serve as the macro lens on the microscope stand. Don’t waste money on an expensive model; the lens from a $2 laser is fine. To achieve higher magnification (up to 325x), use two! You can also buy the bare lenses online (see the Parts list above) and skip this step.

To get the lens from the laser pointer, start by unscrewing the front cone and the back cover of the tube. Remove the batteries. Using the eraser end of a pencil, push the innards out of the front of the tube.

The front of this assembly is where the focus lens sits. Unscrew the small black plastic retainer in front of the lens and the lens will come free.

The lens is not symmetrical when viewed from the edge. You’ll see a thin, translucent strip (~1mm) on one side of the otherwise transparent lens (in this photo it’s shown on the left side). This side must face away from the camera. You can determine the correct orientation by sticking the lens between the prongs of a hairpin, then taping the rig to the back of your smartphone as shown in the second photo here. The correct orientation will provide you with a larger field of view.

As it is, you can take reasonably good macro photos with just this lens and your smartphone. But it’s extremely hard to keep the phone steady when taking zoomed-in photos. That’s why you need to build a stand!

Mark the top of the plywood base at the front 2 corners, 3/4″ in from both the sides and the front edge. Make a third mark centered 3/4″ from the back edge.

Stack the plexiglass camera stage (7″×7″) on top of the base. Then stack the specimen stage (3″×7″) on top of the camera stage, with 3/4″ of the specimen stage extending over the front of the base. Clamp and drill through the entire assembly.

The bolts that stick up through the base must be counterbored in order for the stand to sit flat. Flip the base over and counterbore the holes with a spade bit to accommodate the bolt heads.

TIP: Put a sacrificial piece of wood beneath the plywood base before drilling. You don’t want to damage your workbench.

Skill Builder: Drill acrylic without cracking: Acrylic is prone to cracking when cut or drilled. Here’s how to prevent it: First, put a piece of tape over the area you’re about to drill. For drilling thick acrylic, skip the tape and spray WD-40 as a cutting fluid to add lubrication. Measure and mark, then drill slowly, using a sharp bit and gentle pressure. Do not press hard — let the drill do the work.

Find a drill bit slightly smaller than the diameter of the lens. Then measure, mark, and drill a hole in the camera stage, 3/4″ from the front edge, in line with the bolt holes.

Press-fit the lens into the hole. If it doesn’t quite fit, use a file or sandpaper to enlarge the hole. Work slowly and test the fit often. It’s easy to overshoot and make the hole too large! You can remedy this with tiny bit of glue, but be very careful not to get glue on the lens surfaces.

When using the stand, it’s important to have the lens as close as possible to the camera. If you plan to keep your phone in a case when you use the stand, then leave the top of the lens slightly exposed so that it will rest closer to the camera. Otherwise, mount the lens flush with the stage.

If you’re using 2 laser lenses, mount them one above the other in the camera stage, inserting one lens from below and the other from above. This increased my magnification to ~325x.

Be careful not to let these lenses touch, and install them as level as possible. Failure to do so can cause aberrations in the image.

Next, drill a shallow hole in the base to accommodate your light source. (Small LED click lights work well.) It’s important that your light source is directly below the focus lens. To mark the right placement, first test-fit the base, bolts, and camera stage together, then slide the camera stage down to the base and mark the base with a pencil, directly beneath the lens.

Start with washers and nuts to hold the 3 bolts tight to the base. Add some upside-down wing nuts and then washers to the 2 front bolts. Then place the specimen stage on top of these washers.

Add a nut to each bolt, and lower them about 1/2″. Then put a compression spring over each front nut and bolt, and rest the camera stage on top of the nuts.

A level is handy here to make sure that the stage is actually flat. If you don’t own a level there are plenty of free level apps for a phone! Use wire cutters or pliers to trim or adjust the springs if necessary. When the stage is level both front to back and left to right, tighten down the final nuts.

The compression springs keep the specimen stage stabilized and allow you to make far finer adjustments with the wing nuts. Without these springs, the specimen stage can tilt one way or another if the load is imbalanced or if the bolt holes are too large.

The focal length of the lens is very short and the specimen stage can only be raised so close to it because of the nuts holding up the camera stage. Using a transparent sample slide fixes this problem and makes manipulating samples while viewing easier. Simply cut a 2″×4″ piece of plexiglass.

With 2 lenses, the focal length gets even smaller, so 2 plexi slides are required.

Or video! With $10 worth of materials and a smartphone, you just made a digital microscope.

Align your smartphone camera lens with the microscope lens. Bring the object into focus by slowly turning the wing nuts on either side, then use your phone to take a picture or video, or even zoom in for a closer look.

I’m a major proponent of making home science more accessible. My goal in designing and building this phone-to-microscope conversion stand is to provide an alternative to overly expensive microscopes. This setup is a viable option for underfunded science classrooms that would not otherwise be able to perform experiments requiring a microscope. But more than that, this device will allow people to rediscover the world around them.