Re-did measurements from yesterday. Daniel brought up point about green light leaking into IR measurements and vice versa. So addressed this.
IR Laser Light: Look At filters to attenuate IR
Here we wanted to see which filter was best for viewing the GREEN light, so we wanted the filter which passed green & cut out IR. With the Prometheus laser we used its IR light. To make sure there was no Green light, we dropped in a Hoya R72 filter (to remove any Green light from laser). Then we looked at the filters I bought . So this is what we had:
- IR light from laser ONLY = 420mW
- Hoya R72 in path = 414mW
- BP550 (+ Hoya) = 3.11mW---best filter for viewing GREEN light
- lp550 (+ Hoya) = 423mW
- lp920 (+ Hoya) = 431mW
- bn532 (+ Hoya) = 167mW
The BP550 is OK, but Daniel says the OD of this filter may be low and we should look for a Schott glass filter (order of 4mm thick, similar to our old iLIGO glasses). Either that or we can see what a couple of the BP 550s filters look like in series.
GREEN Laser Light: Look At filters to attenuate Green
Here we want to see which filter is best for viewing IR light, so we want a filter which passes IR & attenuates Green. With the Prometheus laser we had green light. To make sure there is no IR light leaking in, we dropped an iLIGO goggle in the beam path as a filter.
- Only Green light = 20.2 mW
- iLIGO Glasses in path = 13.18 mW
- iLIGO + Hoya R72 = less than 5nW
- LP550 (+iLIGO glass) = 39.3 uW
- LP920 (+iLIGO glass) = less than 5nW
- BN532 (+iLIGO glass) = 7.45 mW
- BP550(+iLIGO glass) =8.03 mW
LP 920 may be good...maybe have two in series?
So the plan is this.
For Green-viewing camera, we will actually use a 4mm thick KG5 Schott filter (these are on order from UQG Optics in the UK).
For the IR-viewing camera, we actually want to try the LP 550 from the entry above (the LP920 & Hoya R72 will show IR light, but we won't see much else). Since we have one of the LP550s, we can test out this filter now. Want to make sure we can easily install this on the Rainbow zoom lens (without disturbing alignment). If we like it, we can order more of these guys.