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3) Now adjust angle of prism to find the angle of minimum deviation using rotation stage (coarse adjustment). Do this by placing an IR card far away and rotating prism to find angle where beam is furthers to the right.
4) Now make sure reflected beam and incident beam are coplanar by adjusting You will now adjust the angle of the prism and looking at the height of the reflected beam on the IR card. The reflection is very faint and needs an IR viewer to be seenusing the Polaris mount. You will need a hex key cut down to fit the adjustment knobs on the underside of the Polaris mount to which the prism is glued. There are two adjustments to make:
4a) Ensure that the partial reflection of the beam off the prism surface is co-planar with the incident beam. You can see the reflected beam using an IR viewing card (ThorLabs VRC4 is nice) but you may also need an amplified IR viewing device. Use one of the adjusters on the Polaris mount to change the prism tilt and read the change in angle using the height of the beam on the IR card.
4b 5) Now make sure the refracted beam traveling through the prism is coplanar with the reflected and incident beam by adjusting tweaking the other angle of the prism with the other adjuster.
65) Redo finding angle of minimum deviation using fine adjustment. This will be the angle where the beam is the rightmost possible.
76) Align the retroreflector axis. Adjust height of retroflector such that the return beam is centered on the roof mirror. Then adjust close side of rail such that the returning beam is hitting the prism a little further into the prism (2 to 3 mm). Then adjust the back position such the rail is exactly parallel to the beam. Slide the retroreflector back and forth along the rail to check that it is moving along the axis of the beam (beam does not deviate as reflector is moved). An easy way of doing this is to tape thin lens cleaning paper over an SM2 lens and bolt this in front of the mirror. The paper will fluoresce yet allow the beam through. You can visual the beam using either a specialised IR viewer or a cell phone (you may need to turn off the lights when using a phone).
7 8) Adjust lateral position of roof prisms so that return beam is entering the prism, and rotate it so that the outbound beam 3 is hitting the retroreflector. Do fine angle adjustments of the prisms angle such that return beam 4 is level to table and colinear with track.
9 8) Mount output coupler. Place in bypass mode, and set target card after exit iris. Left bypass mode. Align exit beam to pass through iris and hit target by adjusting height of retroreflector so that beam passes through center of exit iris and move mirror to translate mirror, and use angle of mirror to make beam hit target on iris card.
109) Add two mirrors such that beam is level as it goes into the entrance of periscope.
1110) Set periscope entrance mirror center to be 120 mm heigh (or height of laser beam).
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