LGSW CalUnit alignment

After having assembled the WFS up to the periscope we inserted the calibration unit into it.

To start aligning the CalUnit the pupil motors have to be moved towards the mechanical axis of the sensor by 0.91mm (143 steps). So new pupil motors positions are:

Pupil X Y
Blue 365 412
Yellow 234 301
Red 364 306

Then we have centred the beam from cal unit on the hole on the back of the EW. Keeping the spot centred there we pistoned the cal unit mirrors to bring the pupil on its nominal position (measured on the alignment flange) just after the PiezoMirrors. Once the pupil is in the proper place we nulled the tilt of the beam after the PiezoMirrors moving the beam from the cal unit across the back of the EW.

For the Blue and Red channels we could align the cal unit with the pupil motors on the position stated above. Since the YellowChannel had the field stop out of its nominal position by almost 1.5mm we had to move the pupil motor and piezo to bring the cal unit beam on the nominal path.

Blue 365 412 0 0
Yellow 264 361 -0.002 0
Red 364 306 0 0

Lenslet array alignment

We started with rotating in clock the LA to match the spots on the pixel grid (final clock value is below 0.5px/260px = 0.1deg). We double checked that the clock alignment was conserved dismounting and mounting again the LA.

The focus alignment of the LA was done putting the mount in its nominal position of 554mm measured from the PC frange back to the LA mount baseplate back.

The LA has been firstly centred on the rail using the caliper (<0.1mm discrepancy between dx-sx and back-front sides).

We checked the mechanical axis position on the camera putting the alignment mask in front of the PnCCD. We measured the center of the spot position to be 145px in the vertical direction and 136px in the horizontal. Since the camera is connected to the SX electronics we had a 180deg rotation. So finally the mechanical axis of the WFS as visualized from the alignment mask is 0.624mm below the chip centre (wrt the 0.83mm nominal).

We then aligned the LA in XY directions to put a lens into the centre of the chip.

Alignment verification

We mounted then the rest of the sensor: RL, FL and collimator together with the dummy PockelsCells. Since the camera was rotated we could not properly double check the alignment closing the pupil and jitter loops. We moved by hand the pupil motots to match the pupils position on the CCD:

Blue 425 472
Yellow 264 421
Red 364 246

-- MarcoBonaglia - 27 Aug 2015
Topic revision: r1 - 27 Aug 2015, MarcoBonaglia
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