[Kiwamu, Masayuki, Yutaro]

We aligned the IR beam so that it reaches X end, and now the green and IR beams reach X end at the same time and we assume both hit at the center of PR2/3.

= What we did =
1. checked the beam position at PR2. It was off in YAW by 5mm (+y) so we rotated IMMT2 in YAW by ~ -100urad.
2. behind PR2, tried to find the beam on the way from PR3 to BS, but failed.
3. actuated PR2 so that IM horizontal OSEMs got healthy and oplev outputs became close to zero by using IM pico and the traverser.
4. found the beam at behind PR2, and it was low compared with green by ~ 5cm.
5. overlapped the IR beam on the green one by rotating IMMT2 in PIT (by ~-150urad).
6. swept the angle of PR3 to find the IR beam at X end; the angle we found the IR beam was different from that of the green beam mainly in PIT direction (by ~300urad).
7. rotated PR2 so that IR reached X end with such an angle of PR3 that green reached X end at the same time.
8. while doing 7., found that the maximum power reached X end got decreased and decreased. This was due to change of the spot position at PR3; we next rotated IMMT2.
9. rotated IMMT2 and PR2 in such a way that the beam was kept reaching X end and the PIT angle of IMMT2 got close to 0urad, where we know the IR beam hits at the center of PR2 (this has been confirmed in 1.).
10. centered oplev QPD for PR2, since we rotated PR2 by a few mrad in - PIT direction in the process 7-9 and it was no longer in the effective range.