FAQ/Objective versus relay GRIN lenses
Very likely the wrong class of GRIN lens. This has cost multiple labs entire cohorts. The V4 needs a RELAY GRIN lens. Relay lenses have a pitch a little less than 0.5 × n (n = 1, 2, 3 …) and roughly 200 µm front and back working distance. An OBJECTIVE GRIN lens will not work with the V4. Objective lenses — for example Edmund 64-519, 1.8 mm diameter, 0.25 pitch — are what the V3 used, implanted directly into the brain, and they have a pitch slightly under 0.25. The two are easy to confuse because both are sold as implantable GRIN lenses. The V4 images through a cranial window with no external lens at all, or deeper via a relay lens. All relay lenses sold by Inscopix are V4-compatible. Salvage for animals already implanted with an objective lens: stack a second GRIN lens on top of the implanted one — the pair then behaves as a relay, and you may get usable imaging out of the cohort. The symptom is total darkness with healthy optics, verified expression and correct aspiration depth: exactly the case that otherwise sends people hunting for inflammation or photobleaching. See also FAQ/Catalogue working distance and pitch are not what you get.
More help on this wiki
- GRIN Lens Information — Pitch, index profile and the difference between lens roles.
- Imaging With Thin GRIN Lenses — Scope modifications for 1 mm and thinner relay lenses.
- Miniscope V3 — What the V3 optical path expected, for anyone inheriting older parts.
- Guide/Miniscope V4 part procurement — Ordering the right parts for a V4.
Still stuck? Bring it to the drop-in office hours, browse the full FAQ library, or see Guide/Common pitfalls and FAQs.
Discuss this FAQ
Have a follow-up question, a result that contradicts this, or a correction? Please post it on the wiki forum rather than the Google Group, so the discussion stays next to the answer and stays searchable here.
No one has discussed this FAQ on the wiki yet — start the first thread in Forum:Experiments and methods. The subject and a link back to this page are filled in for you — add your question and sign it with four tildes.
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 |
|---|---|---|
| Absolutely no signal while attempting to baseplate | 2020-12-08 → 2021-03-04 | Daniel Aharoni |