20|
3.0 Initial Setup
3.3.3 Aligning the laser to the Scanhead
The process below describes the necessary stages for aligning the laser
beam through the scanner to the back aperture of the objective.
The scanner input cage accessory can be used to build the 6mm cage
rods from the x galvo assembly to the top periscope mirror.
Two irises, one near the periscope top mirror and the other at the x
galvo assembly can be used to direct the beam parallel to the table and
orthogonal to the x galvo assembly (whilst maintaining centration with
the input port). To do this each iris should be opened and closed in turn
as follows:
General alignment procedure of laser to Scanhead
The 3U Galvo drive rack needs to be powered on throughout the
following process.
1.
Screw the projector lens with graticule into the MDU or MOC
using the supplied adapter.
2.
Place the IR alignment card on the sample stage and look at
the image of the graticule projected onto it from the projector
lens.
It is likely that the image of the graticule is not evenly
illuminated due to residual misalignment of the laser beam.
3.
Close down the iris near the top periscope to a diameter
approaching that of the beam waist. Adjust the bottom
periscope mirror mount micrometer screws to move the
beam until it is centred on the iris.
4.
Open the iris nearest the top periscope mirror mount to allow
the beam to pass through it unclipped, then close down the
iris nearest the x galvo assembly. Similarly direct the beam
towards this iris by turning the micrometer screws of the top
periscope mirror mount.
5.
Repeat steps 3 and 4 above until the beam is central on both
irises.
6.
View the enlarged projected image of the graticule on a small
rectangular piece of card, so that it is approximately 30-40
mm in diameter but is still visible. If the beam is well centred
on the image of the graticule, then no further alignment is
required. If this is not the case proceed to the next step.
7.
With the iris furthest away from the scanner shut to
approximately the beam diameter e.g. 3 mm, use the pair of
periscope mirror mount screws from top and bottom mounts
to move the beam in the same direction e.g. up and down or
left and right.
8.
Once the image of the graticule is evenly illuminated and the
beam is centred on the iris the Scanhead is nominally aligned
to both back aperture and centre of specimen image plane.
