Microscope Dock
Everything anyone sees down a microscope gets written down as a word. About 80%. Looks healthy. Some debris. A photograph settles all three, and the camera to take it is already in your pocket — the only hard part is holding it still, square, and at the right height over a 20 mm circle of glass. This is the printed dock that does the holding: a collar that clamps the eyepiece barrel, a cradle that puts the phone’s camera on the optical axis, and a bench arm underneath carrying the weight so none of it hangs off the microscope.
The models aren’t posted yet. What is below is the bill of materials, the print settings this part wants, and the measuring and camera work that decide whether it produces anything usable — the STLs will land in the download section at the bottom.
If your microscope has a trinocular photo port, don’t build this. A proper C-mount camera on that port beats any phone dock, permanently. This is for the binocular scope in the corner that nobody is ever going to buy a camera for.
Parts
Some links below are Amazon affiliate links. As an Amazon Associate I earn from qualifying purchases — at no extra cost to you. It helps keep these guides free. Outside the US, they should send you to your own Amazon store; if one doesn't, searching the part number there will find it.
- Digital caliper — the eyepiece barrel diameter is the whole project. Measure it before anything else
- PETG filament, 1.75 mm — the collar goes in this
- PLA+ filament, 1.75 mm — the cradle, and the cheaper spool for test rings (4 × 1 kg, black)
- TPU filament, 1.75 mm — a thin band inside the collar, and pads in the cradle floor if you’d rather print them than stick the rubber ones in. Nothing rigid touches the eyepiece or the phone
- M3 heat-set threaded inserts — one in the collar’s clamp boss, one in the cradle where the standoff bolts on (100 pcs, you need two)
- M3 screw, nut and washer assortment — 562 pieces, and you will use about four of them
- M3 knurled thumb screws — worth it. Gloved hands and a hex key are a bad combination, and a collar you can only loosen with a tool is a collar that never comes off
- Articulating magic arm with a bench clamp — clamps to the bench and carries the phone. This is the part that stops a phone hanging off an eyepiece
- 1/4 in-20 mounting screw — the cradle onto the arm. The arm’s mounting stud screws out and this goes up through the cradle into the thread it came out of, so the printed part needs a clearance hole and nothing else
- Deburring tool — one pass round the inside of the collar. A burr on the bore is a scratch on the eyepiece
- Self-adhesive rubber bumpers — two in the floor of the cradle, so the phone’s back rests on rubber rather than on layer lines (200 pcs, you need two)
- Optical lens tissue — for the eye lens afterwards, because a phone dock is a machine for putting fingerprints on an eyepiece
The microscope is the one you already have. So is the phone.
Before you print
Measure the barrel, not the eyecup. The collar clamps the metal tube of the eyepiece, below the rubber eyecup, which folds down or pulls off. Eyecups are soft, they are different on every eyepiece, and a clamp tightened onto one goes slowly out of alignment as the rubber relaxes. Put the caliper on the metal and work from that number.
Do not take the microscope tube bore as the answer either. A lab scope’s tubes are usually 23.2 mm or 30 mm, but that is the hole the eyepiece drops into — the part you are clamping is the shoulder above it, and it is a different diameter on every eyepiece I have measured. There is no standard here worth trusting over thirty seconds with a caliper.
Then find out where your phone’s camera actually is. It is not centred, it is not in the same corner on two models, and a modern phone has three of them a centimetre apart. Pick the lens you are going to use — the main wide, not the ultrawide — and measure from the phone’s edges to that one. The cradle exists to put that single lens over the optical axis; everything else about the phone is packaging.
Print settings
| Setting | Value |
|---|---|
| Layer height | 0.2 mm |
| Walls / perimeters | 4 on the collar, 3 on the cradle |
| Infill | 20% |
| Supports | None |
| Material | PETG for the collar, PLA+ for the cradle |
| Orientation | Collar axis vertical, cradle flat on its back |
The collar prints with its axis vertical, so the clamp band’s extrusions run round the bore rather than across it. Printed on its side, the band is a stack of layer lines pulling apart in exactly the direction the clamp screw pulls, and it splits the first time somebody over-tightens it.
Turn up wall count rather than infill on the collar. It is a thin ring under a permanent squeeze; perimeters carry that load and sparse infill does nothing.
Material
PETG for the collar. It is a clamp, and a clamp is a part that lives under a constant load — PLA creeps under one, and a collar that has crept is a collar that lets go, a week after you stopped watching, with a phone in it. PETG also takes a 70% ethanol wipe, which anything that goes into a tissue culture room gets whether you planned for it or not.
PLA+ is fine for the cradle. It carries the phone in compression, sees no sustained clamping load, and prints more accurately, so the camera cutout lands where the model says it does.
TPU for the band inside the collar, and nothing hard in its place. The two things this part touches are somebody’s optics and somebody’s phone. The adhesive bumpers do the same job in the cradle floor if you don’t want to swap filament for two pads.
Fitting it
-
Print a test ring first. A 10 mm slice of the collar’s bore and nothing else — minutes rather than hours. Slide it onto the eyepiece. It should go on dry with light thumb pressure and no rocking. Adjust the bore in the model and print another; do not fix it with the slicer’s scale box, which scales the screw boss and the wall thickness along with the hole.
-
Melt the inserts in. One in the collar’s clamp boss, one in the cradle where the standoff bolts on. Soldering iron at 200 °C or so, straight down, and let it cool before you thread anything into it.
-
Line the collar with a strip of TPU, and stick the two rubber bumpers in the cradle floor. Nothing rigid touches glass or phone, and nothing adhesive goes anywhere near the barrel.
-
Clamp the arm to the bench first. Unscrew its mounting stud, bring the arm up under the cradle and run the 1/4 in-20 screw up through the cradle into the arm. Set the arm so it is holding the phone’s weight before you tighten the collar — the collar is there to hold alignment, not load.
-
Focus the microscope on something with hard edges before you go anywhere near the phone. A slide with writing on it, or the edge of a flask’s growth surface. You cannot centre a camera on a grey blur.
-
Drop the phone in and slide the cradle until the bright circle sits in the middle of the frame. Lock it there. This is the ten minutes that decides whether the dock is worth having, and it only has to be done once per phone.
Getting a picture worth keeping
Zoom in about 2×. The eyepiece throws a small image circle and a phone’s wide lens sees the black tube all the way round it, so the raw frame is a postage stamp in a ring of nothing. Zooming crops that away in the camera app instead of you doing it afterwards, and it costs nothing, because the pixels you are throwing out only ever held the inside of a brass tube. Check it hasn’t switched lenses on you, though — on a lot of phones 2× is the telephoto, which sits a centimetre from the wide the cradle was aligned to.
Lock focus and exposure. Press and hold on the field until the camera shows its AE/AF lock. A phone left on auto hunts continuously on a low-contrast field of cells, and it meters the bright empty background rather than the specimen, so it underexposes the one thing in the frame you care about.
Lock white balance too if the app will let you. A halogen lamp on a dimmer changes colour as you change brightness. Two pictures of the same flask a week apart, taken at different lamp settings, come out different colours — and the first thing anyone does with a colour difference is read it as a change in the culture.
Take the picture with the volume button or a timer. Tapping the screen pushes the phone, and a phone sitting on an eyepiece is a lever with the pivot in the wrong place.
Living with it
The cradle is the expensive part to get right and the collar is the cheap part, so print a collar per scope rather than a whole dock per scope. Same cradle, same phone alignment, a different bore for each eyepiece in the room, and it moves between them in the time it takes to loosen one thumbscrew.
Nothing printed goes in the autoclave. An autoclave cycle runs at 121 °C and both PETG and PLA are well past soft by then. Wipe it with 70% ethanol and keep it out of the chamber and the glasswasher.
Take it off a shared microscope when you are done. Somebody else’s scope, somebody else’s alignment, and the next person to sit down at it did not agree to a phone bracket on the eyepiece. Ask first if it is not yours.
Troubleshooting
The image is a small circle in a black frame. Zoom in, and check the height. The camera has to sit at the eyepiece’s eye point — the plane where all the light from the objective comes to a narrow bundle. Too high or too low and the circle shrinks. If zoom alone can’t fix it, shorten or lengthen the cradle standoff rather than living with it.
One side of the field is dark. The camera is off axis. Slide the cradle, do not tilt the collar — tilting also swings the phone’s centre of mass out over the eyepiece.
Everything is sharp except the cells. The phone focused on dust on the eye lens. Clean the eyepiece with lens tissue and lock focus again on the specimen.
It drifts out of alignment during a session. The collar is clamped on the rubber eyecup instead of the metal barrel, or the arm is not actually taking the weight. Both show up as an image that was centred when you set it up and is not an hour later.
Files & downloads
The source files for this project aren't in the repo yet — there's nothing to download
beyond the notes. They land in projects/microscope-dock/ when they do, and this
section fills itself in.