ADAPTIVE OPTICS ON A BENCH: BUILDING A DEFORMABLE MIRROR WHOSE SURFACE YOU CAN BEND WITH MAGNETS AND COILS
A hobby optics maker built a 25-actuator deformable mirror on his bench, the kind of part big telescopes use to fight atmospheric blur, and measured every bend with an interferometer.
by Huygens Optics
ScienceWorkshop
- difficulty
- ●●●●●
- time
- several weekends
- license
- license not specified
- repo
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●●●●● · several weekends · license not specified · 0 stars · repo
WHAT YOU’LL NEED
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COMPAREE VERDICT
This is what adaptive optics looks like when you build it yourself: 25 small magnets glued under a thin face sheet, each sitting on a silicone pillar inside a hand-wound coil, so current pushes or pulls the surface locally. Huygens Optics starts with a 2.3 mm quartz photomask, finds it too stiff to show the effect of single actuators, and switches to a 1.3 mm sheet of ZERO near-zero-expansion glass-ceramic that Nippon Electric Glass sent him. He works through the magneto-motive force and power dissipation on camera (0.22 mm wire, 1 ohm coils, 6 mm magnets, about 0.1 N per actuator at 1 amp) and measures every deformation interferometrically. It is a proof of principle, not a working adaptive optics system, and he says so himself, including a design flaw he found: heat from the coils expands the silicone pillars and bumps the face sheet. There is no repository, no drawings and no parts list, so you are working from what you see on screen. This is for someone who wants to understand how a deformable mirror works and has, or wants to build, an interferometer to see what it is doing.
IN THE REPO
GOOD TO KNOW
- —No repository, no files to download, no parts list.
- —This is a documented build — a 31-minute filmed walkthrough with the physics worked through on camera.
- —You will need to source thin near-zero-expansion glass-ceramic yourself (the creator's ZERO sheets were sent by Nippon Electric Glass), bond 25 magnets precisely, wind coils, and measure the result interferometrically.
- —The measurement rig is built from scratch and not detailed in a way someone could copy without already owning an interferometer.
- —Educational documentation, not a build guide. No licence stated.
Parts to buy
6 itemsFrom our check of the build. Exact quantities and part numbers are in the creator’s BOM.
Can I build this?
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
Videos
Creator’s build video31:21
31-minute filmed build and measurement. The physics of the actuators is worked through on camera, the actuator design and the assembled mirror are shown, and the interferometric maps are explained.
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Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Watch the video end to end (This is the only documentation. Take notes on the actuator spacing, magnet sizes, and coil parameters as they appear on screen.)
- 2.Source the glass-ceramic stock(NEG ZERO or an equivalent near-zero-expansion material, about 1.3 mm thick. The creator's sheets were sent by Nippon Electric Glass; he started with a 2.3 mm quartz photomask before switching.)
- 3.Measure the face sheet before you actuate it(The creator did not polish his sheets flat. He measured the unactuated sheet in the interferometer (about 6 lambda concave for the quartz plate, about 9 lambda convex for the ZERO sheet) and used that shape as the zero reference, so every later measurement shows only the change caused by the actuators.)
- 4.Wind the coils and build the actuator array(The video gives the key numbers: 0.22 mm copper wire wound to about 1 ohm per coil, 6 mm magnets, roughly 0.1 N per actuator at 1 amp. It also shows that at a fixed power the number of turns barely matters. There is no drawing of the bobbins.)
- 5.Measure each actuator(Interferometric measurement is the only way to see what each actuator is doing. If you do not have an interferometer, this step becomes its own project.)
KNOWN ISSUES
- No repository means no files to download. You are reverse-engineering this from a video, and the tolerances matter.
- NEG ZERO glass-ceramic is not a common stock item. The creator's sheets were sent by Nippon Electric Glass; you will have to contact NEG or a distributor, or start with a thin quartz plate as he did.
- Face sheet thickness decides what you can see. With the 2.3 mm quartz plate the creator could not tell neighbouring actuators apart; only the 1.3 mm sheet showed single-actuator effects. Neither sheet was truly flat (one was about 9 lambda convex); he subtracted the rest shape in the interferometry software.
- Magnet bonding position accuracy matters. A magnet even slightly off-center will pull the sheet asymmetrically.
- The interferometric measurement rig is shown but not documented as something you can build separately. If you do not already have an interferometer, add weeks.
- The video calculates the magneto-motive force and thermal limits on camera, but those are starting points. Your coils and magnets will differ and you will need to redo the math.
Is there a repository or a bill of materials?
No. This is a filmed build with no downloadable files, no parts list, and no CAD. You are working from what you see on screen.
Where do I buy NEG ZERO glass-ceramic?
The creator did not buy it: Nippon Electric Glass sent him two thin ZERO sheets (1.6 and 1.3 mm), and the video description links NEG's product page. ZERO is a near-zero-expansion glass-ceramic from Nippon Electric Glass. For your own build, contact NEG or an optical-materials distributor, or start the way he did, with a thin quartz plate (he began with a 2.3 mm quartz photomask).
Do I need an interferometer?
Yes, if you want to measure what each actuator is doing. All the deformation maps in the video come from an interferometer running near-real-time software (Wavefront Pro), at a resolution of fractions of a wavelength.
Can I build this without optics fabrication experience?
It helps a lot. The creator is an experienced optician and still ended up with face sheets that were several wavelengths out of flat, which he handled by subtracting the rest shape in the measurement software. Cutting thin glass, bonding 25 magnets in position and reading interferograms are the real skills here.
How much does the glass-ceramic cost?
Not stated. The creator's sheets were a gift from Nippon Electric Glass, so the video gives no price. Ask NEG or a distributor for a quote for the size and thickness you need.
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Discussion1
FROM THE COMPAREE TEAM
The creator got his ZERO glass-ceramic sheets straight from Nippon Electric Glass. If you were building this without that kind of help, what would you use for a thin, low-expansion face sheet?
Huygens Optics
A YouTube channel dedicated to building and explaining optical systems from first principles. This deformable mirror project is filmed as a teaching exercise, not as a replicable design, and the focus is on understanding how adaptive optics works on a bench.
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DISCLAIMER
- Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
- Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
- Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
CompareeTEAM1mo agoedited
Practical notes from our verification: this is a filmed build with no repository, no downloadable files and no parts list. The video runs about 31 minutes, the physics is worked through on camera, and the interferometric maps are explained clearly. The key numbers are spoken rather than written down: 0.22 mm wire, 1 ohm coils, 6 mm magnets, about 0.1 N per actuator at 1 amp. The ZERO glass-ceramic sheets were a gift from Nippon Electric Glass, so plan your own sourcing. The creator points out his own design flaw: coil heat expands the silicone pillars and lifts the face sheet, and he says a PCB with integrated coils or piezo actuators would be better. Without interferometer access you cannot see what the mirror is doing. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.