Using the Visible Light Microscope (VLM)

The visible light microscope (VLM) built into STXM V is used to align the microscope, and to prefocus on and locate interesting specimen areas. It is assumed that all cable connections have been made properly. Refer to Fig. 2.3 for the location of the hardware. Turn on the illuminator and the electronics for the VLM, which are located on the top of the electronics rack.

**Figure 2.3:** The illuminator (A) supplies light to the VLM by fiber optics. The white electronics box (B) supplies all power to the VLM. Turn it on with the red button. The black CCD readout electronics box (C) is powered by the white box (B) and does not need to be turned on.
$\includegraphics[height=2.in]{images/vlm_hardware}$

We use a "Axis 241Q Video Server" to web cast the VLM signals. Just open a web browser and type vlm in the address bar. An icon labeled VLM is on the client computer desktop, which opens this address in Mozilla Firefox. The opening screen will show a combination of four streams, of which only the first two (Inboard and Outboard) are used. Click on the pertaining quadrant to open a large view of one branch as shown in Fig. 2.4.

**Figure 2.4:** VLM view of a sample in outboard stxm. The blue square in the center shows, where the optical axis (zone plate, order sorting aperture, x-ray focus) is. The tool in the upper right corner is for snapshots
$\includegraphics[width=0.75\textwidth]{images/vlm_view}$

The blue square in the middle indicates, where the optical axis of the microscope is. Basically zone plate, order sorting aperture and x-ray focus lie within, so you want to move your sample, until the interesting area lies inside the square. To move the square go to Setup (upper right, root password required), then go to Video & Image $\rightarrow$ Video 1(in case of outboard) $\rightarrow$ Image. Under Overlay Settings you can adjust the X/Y coordinates of the blue square. Click Test to check the new position of the square and keep adjusting until you're satisfied. Don't forget the click Save at the bottom, before going back to Live View.
If you don't want to use the blue square, but rather mark the exit snout and zone plate positions (see 12.2.1) on the monitor (local client only), will have to align the vlm image to the lower right edge of the desktop. It won't snap into position, so you will have to use good eye sight for this.
To save the VLM picture to a file for later use, just click the Snapshot button, and then right click on the created jpg and save it.