FAQ/Horizontal stripes from the EWL driver
From the electrowetting lens driver. It generates a roughly 70 V square wave at about 5 kHz, and on each swing there is a current inrush the 3.3 V regulator cannot keep up with. That noise propagates back up the 3.3 V line to the CMOS sensor, which is unusually sensitive to it. The noise itself is very small — the sensor amplifies it into visible banding. Ordinary bypass capacitors do not isolate it, because the swings are slow. A 47 µF capacitor between 3.3 V and GND does remove it, and sits near the EWL driver on current V4 PCBs. Boards at v4.2 and v4.3 predate this: LabMaker sold a hot-fix PCB for them, and it is designed in from v4.4 onward. Every V4 shows a trace of this at maximum CMOS gain; below maximum it is usually invisible. Removing it in post is straightforward: the stripes occupy a very specific spatial frequency that is localised in the 2D FFT. Take the 2D FFT of each frame, find the one or two localised spots along the x or y axis, zero those bins, and inverse FFT. The official denoising notebook does exactly this. Same root cause as the ephys noise in FAQ/Miniscope noise in ephys recordings — one driver, two symptoms. If your lines look different from this, see FAQ/Striping artifact on V4 images, FAQ/Lines and instability at high LED values and FAQ/Banding from ground loops and shared power.
More help on this wiki
- Guide/Anatomy of a miniscope recording — What is signal and what is noise in a recording.
- Guide/Fundamentals of miniscope optoelectronics and imaging — What the electrowetting lens does and how it is driven.
- Guide/How to test and debug your Miniscope V4 — Identifying which artefact you actually have.
Still stuck? Bring it to the drop-in office hours, browse the full FAQ library, or see Guide/Common pitfalls and FAQs.
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Original Google Group threads
These are threads on the external Miniscope Google Group, not pages on this wiki. They are where this answer came from and are kept for attribution and context. For anything new, please use the wiki forum above instead.
| Google Group thread | Activity | Answered by |
|---|---|---|
| Horizontal scan lines during imaging | 2020-08-17 → 2020-09-02 | Daniel Aharoni, Federico Sangiuliano |
| Scanning horizontal lines with pcb v4.40 | 2021-07-01 → 2022-08-03 | Daniel Aharoni |