Alignment of the prisms on the SmallFibres module

Important to know what the tolerances are on the alignment of these prisms.

The prisms are 44-44-92 degrees. This is for compensating the telecentrisitie of the beam coming from the telescope on to the fieldplate. There fore the beam entering the prisms will have a maximum difference of about ±2 degrees. This means that the accuracy of the alignment of the image exiting the prism has to be within ±0.5 degree.

Also the position of the prism to the button is not important for the placing robot can cope with this.

The alignment of the rotation in the fibre axis is important. This should be aligned as accurate as possible.

The next steps will guide you through the alignment of the gluing jig and the gluing and aligning of the prisms.

Alignment of the gluing jig

Fire a laser on the right height, where the prism will be, to the jig. On the position of the prism put a flat mirror mounted to the jig.

Align the laser until the reflected beam I goes back into the laser.

Put a target under the laser exit, which has its centre 4 degrees down. The distance of the target centre to the laser exit depends on the distance of the target/laser to the prism.

Gluing of the buttons and the prisms

Things to do before gluing the buttons and the prisms

- Glue the magnets in the buttons. Make sure that the magnet is within the button and that glue isn't spilled on the reference surfaces of the button.

- Look for orientation of the prisms. There is a facet off the prism, which indicates the coated side of the prism. You can also look for the uncoated surface of the prism. This side has to be glued on the fibre

- Clean the fibre ends

Gluing the buttons and prisms

1) Mount the button with the fibre on the jig against the mechanical top at the top.

2) Align the fibre with target behind the jig.

3) Put some glue on the fibre end.

4) Check if the fibre is still at the stop or bring it to it again and check the alignment.

5) Bring the prism to the fibre end

6) Align the prism to the target within its tolerance band (+- 0.2 degrees)

7) Lower the prism and check / realign the prism

8) Bring in the UV-lamps and let the glue harden for 100 seconds

9) Take out the fibre from the jig and check the cosmetic quality of the gluing

10) Continue to the next fibre