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Section 4: Optical Alignment
The PF850 is mounted in the infinity space of the microscope. In order perform correctly it needs to
be aligned with the optical path. First, the refractive and reflective optical elements of the PF850 head
must be aligned with the microscope objectives. The focal point of the laser on the sensor must then
be determined, half of the laser blocked in order to generate signal imbalance either side of focus,
and the average background illumination reaching the PureFocus850 sensor calculated. Optical
alignment of the system is only required once.
4.1 Aligning the PF850 with the optical path
Rotate or move the nosepiece to place the alignment target into the optical path.
Place the PF300 alignment camera onto the microscope stage using an appropriate sample holder.
Connect the camera to the PC via the USB, using the 1.8-metre extension lead if required. Move
microscope stage to manoeuvre the camera close to the centre of the alignment target (Fig. 4).
Open the ‘camera’ application, select USB Camera 2.0, and then click start.
Start the PureFocus850 GUI. Go to the offset submenu and select ‘Go to Limit’. The offset lens will
move in the PureFocus850 head.
A pink laser signal should be visible on the camera. Ensure the centre of the target is in the centre of
the field of view. Set the PureFocus850 controller into MAN OFF mode and rotate the digipot to extend
the laser signal to the approximate diameter of the first visible ring of the target.
