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6) 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) 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.
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