Homing of stepping motor stages

All stepping motors of the microscope have a home position, that is defined by a physical switch in the stage. At the home position all encoders (the numbers shown on the front panel of the motor controller and in the microscope program) should read 0.

In case of a hangup of the motor controller or an accidental reset of the motor position, it is necessary to bring all motors that are affected into their home position and reset (set the encoder to 0) them. The established alignment parameters (like the right $X$ position for the detector, etc.), that are stored in the alignment file, will remain valid after homing and resetting the motors. To home a motor, press the HOME button of the corresponding axis on the front panel of the motion controller. To reset the position (to 0), press the reset button. Be careful, since once you press the HOME button, only a STOP ALL or turning the power off will stop the motor from moving. Since errors in this procedure can lead to crashes be sure to watch the action of each step and intervene (STOP ALL button or POWER button of motion controller) if necessary to avoid damage to the stages.
The procedure is as follows:

• Home and reset ZDET. This will retract the detectors fully out of the sample stage. Check clearance before continuing
• Home and reset YDET
• Home and reset XDET. Make sure ZSTG is not all the way downstream before doing this, there needs to be enough space for the detector stage to pass it by.
• Move XDET and YDET, so that the VLM is roughly on beam axis (important!) and then ...
• home ZSTG. For this you have to click Advanced $\rightarrow$ Homing $\rightarrow$ Z Axis.
• Home and reset YSTG
• Home and reset XSTG. A fast way is to just click the home button and then manually make XDET keep up with the XSTG motion (the VLM has to stay roughly in the center of the piezo stage, otherwise you may crash into a detector. Also you need to make sure, that ZSTG is far enough downstream, so you won't hit an interferometer had with one of the mirrors. Slow way: move XSTG and XDET step by step (about 2cm=20000 step pos) outboard.
• Move the ZOSA motor all the way downstream and remove the OSA. Home and reset ZOSA. This will cause it to move all the way upstream (!), so make sure the OSA is out. Move ZOSA all the way downstream to insert the OSA again. You might need to check the proper alignment of the OSA in respect to the ZP before you continue to measure.
• Open the scanning microscope control program
• Move ZOSA to the proper position for which it had been aligned. Look in the alignment file or a recent printout if you are not sure.
• Hit the button to insert the sample stage
• Hit the button to insert the detector (if aligned previously)