TissueCyte Beam Alignment: LCVR
The LCVR (liquid crystal variable retarder) on the TissueCyte regulates the laser power entering the system.
It is the first non-mirror optical element in the path.
The ThorLabs LCVR is very easily damaged: if the beam does not go straight through it, you risk toasting.
A damaged LCVR will produce slow responses, intensity gradients across tiles, etc.
This fact is not noted in the ThorLab’s manual for the device.
The damage occurs when a powerful laser beam hits or scatters onto the edges of the LCVR holder.
The holder is located inside a rotation stage and is protected by an aperture with a radius smaller than that of the LCVR itself.
The aperture is not sufficient to protect the LCVR from damage.
i.e. if the beam swipes across its surface during alignment, you risk damaging the unit.
The only safe way to re-align the beam through the LCVR is as follows:
- Block off the beam entering the device.
- Close the shutter integrated in the aperture in front of the LCVR.
- Unblock the beam and align it so that it hits the middle of the closed shutter.
- Block the beam.
- Open the LCVR shutter.
- Un-block the beam.
At this point you must leave untouched the beam upstream of the LCVR.
