Renishaw HS20 Installation Manual page 59

ii. The intensity distribution of the individual spots.
The intensity distribution of each spot should be such that the spots appear as circular
dots with maximum intensity in the centre, little flaring and virtually no speckle outside the
perimeter of the main spot. At distance diffraction rings concentric with the main spot are
expected.
It will be possible from the above observations to determine if the problem is caused by
contamination (uneven intensity distribution) or misalignment (return beams not positioned
correctly) or possibly a combination of both.
Cleaning external optics
NOTE: The system optics are delicate components, to avoid damaging component coatings/
surfaces cleaning should only be undertaken with the correct materials following the
guidelines below.
It is recommended that the optical surfaces be cleaned only when necessary. If the signal strength is
low, first ensure that the beam alignment is optimised, as this may be the cause of the reduced signal
strength.
In some cases it will be possible to clean the optics on the machine, other cases will dictate that the
optics be removed for cleaning. To minimise the realignment exercise in cases where the optics need
to be withdrawn, remove one optical element (Interferometer or measurement arm retroreflector) at a
time. Reposition the cleaned element and check optical alignment before removing the second optical
component.
Only the external surfaces that are exposed to the environment will require cleaning. This should be
performed using the procedure outlined in the optical cleaning procedure below
Cleaning the HS20 window
NOTE: Cleaning the HS20 window is an extremely delicate operation, cleaning should only be
undertaken after cleaning and alignment adjustment of external optics. The correct materials
should be used and performed by following the guidelines below. This procedure should be
preformed with extreme caution as damage to the window cannot be rectified in the field. The
unit must then be returned to Renishaw.
There are no user-serviceable parts inside the HS20. The only parts of the system that may require
attention throughout their life are the exposed optics. If the system is not operated in a clean environment,
surface contamination will accumulate on the optics over a period of time. This contamination will
eventually affect the system performance by causing deterioration in the signal strength. In extreme
cases it may be necessary to clean the window on the front of the HS20.
To clean the HS20 window the shutter must first be removed from the front of the unit.
Note the shutter retaining bolt is secured using Loctite adhesive. Care should be taken when removing
the bolt and adhesive will be required for reassembly.
To remove the shutter use a 2.5 mm allen key to remove the central bolt, which will expose the
windows for cleaning. The window can now be carefully cleaned using the procedure described below.
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