MRC Laser Beam Stabilization User Manual

: June 9, 2024
: MRC

Laser Beam Stabilization

Description of the communication and visualization software

MRC Laser Beam Stabilization A1

1. Introduction

The Compact laser beam stabilization system can be equipped with a serial or a TCP/IP interface, which allow the setting of parameters and the read-out of values. The serial communication runs via USB or RS232. The TCP/IP communication makes use of an ethernet connection.

The software described here makes use of these interfaces and communicates with the stabilization system. It offers real-time displays of the positions, intensities, and piezo voltages and includes some functions to control the stabilization system.

2. System requirements, installation

The software works with one or more 4-axes stabilizations, i.e. Compact systems with two position detectors and two piezo-driven 2D actuators. It can be used on any PC with USB (2.0 or higher), RS232 or ethernet interface.

Versions are available for the following operating systems:

Windows 7 and Windows 10, 32bit
Windows 10, 64bit
Linux Ubuntu (tar archive, Debian package)

In Windows you can start the installation by executing the Microsoft Installer .msi file. Depending on your installation it can be necessary to additionally install the FTDI driver. In most cases this takes place automatically. If you use the USB interface and want to reach higher data rates you can decrease the USB latency timer in the Windows driver from the default 16 ms to e.g. 2 or 1 ms. For that purpose, please start the Device Manager and find your USB port. Then call Properties, call Advanced, and change the latency timer from 16 to 2 or 1 ms.

In Linux you can unpack the archive with tar -xzf mrc- beamstabil-2.1-Bxxxx.tar.gz or use the Debian package with dpkg -i mrc- beamstabil-2.1-bxxxx-X64.deb.

Beam controllers equipped with ethernet are shipped with factory settings in DHCP mode. This means that a connection to the network can only be made via a DHCP server and not directly with the computer. If you are not familiar with a network architecture, you can ask a system administrator to determine the IP address of the device.

If you want to connect an ethernet device directly to a computer, you can disable the DHCP mode by using the WIZS2E ConfigTool. With this tool you can set a static IP address, under which you will find the system when directly connected to the computer. For a further description of the ethernet option please see section 10.

3. Configurations

The standard configuration of the software includes the following functions:

a) Start and stop of control loop
b) Activity display
c) Display of x and y positions on both detectors (voltage values, x/y plots, position-time-plots)
d) Display of intensities on both detectors (voltage values, intensity-time- plots)
e) Display of voltages applied to the piezos of both actuators
f) Data recording
g) Setting of P factor values for stages 1 and 2 of the control loop
h) Basic statistics of beam pointing
i) Calculation of beam position in [mm/µm]

If your system is equipped with the respective hardware, you can further use the following functions:

j) Set&hold function
k) Adjust-in function

If you have more than one Compact systems, you can also manage the communication with multiple systems. For this purpose we have a separate software version (see section 9).

Note: This version 2.1 of the software is compatible with older Compact systems. However, we have slightly changed the interface protocol. This leads to the limitation that the displays of the Active status of the device and the software are not synchronized, but the status itself is transferred.

4. Program start, connection with the beam stabilization

When the program is started, the beam stabilization is connected automatically. If there is no saved con nection, all serial ports of the PC are scanned and it is checked, if an MRC beam stabilization is con nected. Such a scan is not possible with TCP/IP. To check the settings of the connection you can open the Settings dialog in the menu Connection. You can find more information on the settings in section 6.

5. Main window

Figure 1 shows the main window of the program. It includes a menu bar, a control bar, and the display area. The size of the window can be adjusted. If the window does not allow to display all contents, you can use the scrollbars to shift the visible part.

MRC Laser Beam Stabilization A2 Figure 1: Main window of the communication and visualization software (Version for a single system)

You can call up further functions or dialog windows via the menu bar:

File: This menu only includes the function Exit to exit the program.
Connection: This menu includes items to (dis-)connect the interface for the beam stabilization. Furthermore you can call up the dialog window with the settings of the connection (see section 6). If you are connected to several systems, you can open an overview (see section 9.2).
Data recording: In this menu you can call up the dialog window to set, start, and stop the data recording (see section 7).
Parameters: In this menu you can call up the dialog window to display, insert, and transfer parameters (see section 8). (Note: In the version for multiple systems the dialog window is opened via the submenu System Configuration see section 9.2.)
Under ? you can find information on the software and the manufacturer.

5.2. Control bar

The control bar offers the following functions:

Start/Stop: This button enables to start and stop the display of values in the different plots.
Clear: With this button you can clear the plots.
Update rate: Here you can select the refresh rate to display the data.
Sampling rate: Here you can select the data transfer rate.
Oscilloscope / Pointing mode: This button allows to choose between different presentations in the x/y plots. “Oscilloscope” means a presentation which you are used from an oscilloscope, i.e. each displayed point is cleared immediately. In contrast, in the Pointing mode all points remain so that a cloud of points is built up over time.
Samples to take: Here you can set the number of points which shall be sampled in the Pointing mode. The display automatically stops when the entered number is reached.
Data recording enabled / disabled: This display shows if the data recording is currently activated or not.

Notes:

Please note that the update rate only indicates the cycle in which the data is drawn from the beam stabilization into the display areas. If the update rate is lower than the sampling rate, the data is buffered until the next display cycle.
The update rate can not be chosen higher than the sampling rate.
The sampling rate can only be changed if the display of values is stopped. It is limited to 430 Hz (serial) and 500 Hz (TCP/IP), respectively.
Depending on the speed of your computer/network the actual sampling rate can differ from the edited value.

5.3. Display area

In the display area there are x/y plots, position-time plots, intensity-time plots, big displays of the measured positions and intensities, as well as bar graphs of the piezo voltages of both control stages.

You can zoom into the x/y plots by dragging a rectangle with the left mouse button pressed. By clicking Zoom off you can return to the standard zoom level. If you click into an x/y plot, the coordinates of the mouse cursor are displayed.

In the position-time plots the position signal is continuously displayed as with an oscilloscope. After a defined time the plot starts again from the beginning. You can open an entry mask by clicking on the time axis where you can define the desired time frame instead of the default interval of 10 s. The x/y axis and the I axis can also be zoomed. Just click on the x/y axis to open the respective entry mask.

Further functions in the display area are:

Stabilization ON/OFF: Here you can (de-)activate the control loop. The software switch has the same function as the “Start/Stop” button at the keyboard of the system’s controller box. Switching at the box is still possible. The system always takes up the last action at the hardware or in the software.
Active/Inactive: This signal indicates if the control loop is active or not. It has the same meaning as the “Active” signal on the keyboard of the controller box. You can find more information on this signal in the user manual of the Compact beam stabilization system.
Show statistics: In the Pointing mode you can fade in additional information into the x/y plot (see the following section 5.4).

5.4. Beam pointing statistics

If you have sampled a cloud of points in the Pointing mode, you can display the centre and the variance (RMS deviation) of the points. The centre position (x, y), the number of samples, and the variance are displayed in the upper left corner of the plot. The centre and the variance are also visualised in the plot as a crosshair and the diameter of a circle. The variance corresponds to the root mean square of the distances of the sampled points from the centre. Figure 2 shows an example.

Figure 2: Presentation of beam pointing statistics in Pointing mode

6. Connection settings

You can disconnect and reconnect the beam stabilization system at any time. For this purpose there are the Disconnect and Connect items in the Connection menu. Alternatively, you can manage the connections via a dialog window which you reach via Settings. In this dialog you can save and load a connection for both, serial or TCP/IP communication. The connection settings are saved in the file ConnectionSetup.xml in the program path.

If you have multiple connections, the Disconnect and Connect items are omitted. Instead of these items you can use the System Configuration window to manage the beam stabilization systems. Please see section 9 for more information on this.

6.1. Serial interface

In the submenu Serial only those ports are displayed in the combo box Serial Port to which an MRC beam stabilization system is connected. If you do not find the correct system, you can check the ports again by clicking Rescan. If you have more than one beam stabilization system which you want to control via the same software, you can select the desired one.

Figure 3: Dialog window for the serial interface

At the option Baudrate you can change the baudrate. Please note that for a high baud rate the interface of the PC must be compatible and the beam stabilization must be adjusted. For the serial USB connection you should choose 115200 baud.

The other port parameters are pre-set as follows:

Parameter	Values
Data Bits	8
Parity	None
Stop Bits	1
Flow Control	On (Hardware CTS / RTS)

6.2. TCT/IP interface

In the submenu TCP/IP you can establish a connection with the beam stabilization via ethernet. For this purpose you must determine the IP address of the beam stabilization in your network and enter it as Address. At Port you have to enter your selected settings. The port is set to 2000 in the factory settings.

Figure 4: Dialog window for the TCP/IP interface

7. Save function for data recording

With the software you can save measurement data in the same way as with a storage oscilloscope. For this purpose you can call up the Data recording dialog window via the menu item of this name.

MRC Laser Beam Stabilization A6 Figure 5: Dialog window to set the parameters for data recording

With the items behind Save as you can select a path and enter a file name.

In Save Rate you can enter the rate for the data storage. By default the update rate of the main window is entered here. Especially for long-term recordings it can make sense to enter a lower rate. You can define the duration of the recording by entering a time into the field Automatically stops after.

For the values entered into Save rate and Automatically stops after the software automatically calculates the expected file size and the number of datablocks. In this way you get an orientation on how large the file would get so that you can change the values if necessary.

In case of file sizes larger than 2 GB you will also get a warning (see figure 6). If you wish, you can record larger files anyway, as long as your operation system and your hard disk drive allow.

Figure 6: Warning message regarding the file size for saving

The recording is started by clicking Start. With Stop you can stop it even before it would stop at the time defined in Automatically stops after. On the right side of the control bar you can see an indication if the data recording is currently running or not.

Start: 2021-01-18T16:26:57

MRC Laser Beam Stabilization A8 Figure 7: Example of the typical content in a saved data file

Figure 7 shows the structure of the data file. The time (counted in ms after the start of the recording) is followed by the position and the intensity signals of both detectors as well as the piezo ranges (“R”). All values, except the positions, are given in Volts [V]. The position can be specified in [V], [µm] or [mm], depending on the parameter settings.

Note: If the save rate is not identical to or a divider of the sampling rate, the data will not be recorded equally spaced. Instead the recording will always wait for the next datablock which corresponds to the sampling rate. If you need to have equally spaced data for a further analysis, you must choose a save rate which is identical to or a divider of the sampling rate.

8. Display, insertion, and transfer of control parameters

Via the menu Parameters you can call up the Parameters dialog window to display, insert, and transfer control parameters (see figure 8). In the version for multiple system you reach this menu via the dialog window System Configuration (see figure 10). When you call up this window the parameters are updated by the values currently set in the beam stabilization system. If you want to read in the currently set values from the system at a later time, you can click Refresh.

The respective entry masks for P-Factors and Adjust-In allow you to set new values which are transferred to the stabilization system after clicking Apply. When you close the window with Close without clicking Apply no parameters will be transferred.

Figure 8: Dialog window to display, insert, and transfer control parameters

The functions have the following meaning and ranges:

Set&Hold: With this function you can read in the current beam positions on the detectors and use them as the target positions for the beam stabilization. The position voltages are displayed in the respective fields. The function is only available if you have selected a PSD as the Detector type and the beam stabilization is off.
P-Factor: The P factor function has the same meaning as the corresponding hardware function which is described in the user manual of the Compact beam stabilization system. You can insert values between 0.01 and 5 Volts.
Adjust-in: The Adjust-in function is also similar to the function of the optional Adjust-in inputs at the controller box of the beam stabilization system. The function is only available if you have selected a PSD. You can insert values between -5 and +5 Volts.
With the switches software / external you can define independently if the P factor and the Adjust-in function shall react to the adjustments at the controller box (hardware) or to the software. In the case of the P-Factor the switches for stages 1 and 2 are synchronized.
Detector type: Here you can select different detector types.
Calculate position: You can decide to display the position data with their raw voltages or with calculated positions in mm/µm. In the latter case the software calculates the data with approximations which come close to the real values.
Beam diameter: To calculate the real position data of a 4QD and WID the beam diameter is needed. Please enter the diameter as good as possible to guarantee a good approximation.

Notes:

If you have set a position using the Set&Hold function you can further adjust it with the AdjustIn function.
If you set values with the Set&Hold function or enter voltages for the Adjust-In function, the control loop with the ADC might slightly change these values. I.e. if you click Refresh the actual values might slightly differ from the set or entered values. The accepted changes are very small so that they do not affect the stabilization accuracy.
For the calculation of the real position data the software makes use of the inverse error function in case of 4QDs and the simpler linear equation in case of PSDs. You can find further information on these approximations in the user manual of the Compact beam stabilization system.
The normalization of the WID detector allows the calculation of the positions only in the range from -2.8 to 2.8 V. Outside this range it is not possible to get a valid position in µm.

9. Management of multiple systems

The software can also manage multiple systems. For this purpose it has an additional connection and display management. As soon as more than one system shall be displayed in the display area, the control is moved to the System Configuration window, and the voltage values and the Range displays are no more visible. The plots show the respective systems with the color which you can set in the System Configuration window.

9.1. Connection settings

As in the case of a single beam stabilization system there are two different dialogs to manage serial and TCP/IP connections, respectively.

To keep the overview of multiple systems, you can assign an individual label to each beam stabilization system when you create the connection. You will find this label in the System Configuration and the Parameters windows. To simplify the connection management, a list with all connections is displayed. If you want to disconnect a system, you can do this in this list. If the connection properties are no longer needed because the properties have changed, you can click the trash can to delete them. If you want to change the label of a connection, you can click on the name in the list and change it as desired.

MRC Laser Beam Stabilization A10 Figure 9: Dialog window to handle multiple connections

9.2. System configuration

For a better overview of multiple systems you can select the item System Configuration in the menu Connection which opens a configuration window (see figure 10). There you will find a list of all connections and their controls in the respective line. You can activate the different stages and check the Active status. To get to the parameter window (figure 8) of a specific system, you can press the button Parameters. This opens the window with the system’s label in the header. In the last column you can set the colors of the graphs and decide whether or not the system is displayed in the main display area. If Show is unchecked, the system is not displayed, but still a continuous update of the status is performed.

MRC Laser Beam Stabilization A11 Figure 10: System Configuration window to manage multiple systems

9.3. Save function in case of multiple systems

To simultaneously save the data of multiple systems, there is a checkbox Save all displayed systems in the recording window (figure 11). If the checkbox is selected, all systems that are displayed will be saved. If a system is not selected for display in the System Configuration window, the system will not be saved. To distinguish the different files, the respective label of each system is added to the selected file. The data on the file size and the number of blocks is valid for each of the files. If the checkbox is not selected, only the data of the system with the last recent changes will be saved.

Figure 11: Dialog window to set the parameters for data recording in case of multiple systems

10. Ethernet module

If the ethernet module is integrated into your system, you can reconfigure it with an external software. You can download a suitable tool from WIZS2E ConfigTool. To use the tool, turn on the beam stabilization and connect the computer with this tool to the device. As soon as you start the program, you should see the MAC address of the connected beam stabilization on the left side of the screen (see figure 12). If this is not the case, try to find the beam stabilization with the Search button. Once you have found the beam stabilization, check the COM port settings as described in section 6.2. CTS/RTS must be selected as flow control parameter and the default baud rate is 921600. Before changing the baud rate here, please adjust the baud rate of the beam stabilization with the interface protocol. In the Connection section, the TCP/IP server and the port 2000 must be selected. If you want a different port, you must adjust this in the beam control configuration file ConnectionSettings.xml which you find in the folder BeamStabil of your installation. If the parameters are set correctly, you can adjust the network settings according to your wishes.

Figure 12: WIZS2E ConfigTool with dynamic IP address via a DHCP server

In the default setting of the beam stabilization the IP address is automatically assigned by your DHCP server. This setting is shown in figure 12. To find the newly assigned IP address you have to display all systems in the network via the command line of your operating system. If you need help with this, please contact your system administrator.

To connect directly to a computer you need a static IP address. You can set this as shown in the example in figure 13. Please note that your addresses may differ from the example depending on the settings on your computer.

Figure 13: WIZS2E ConfigTool with static IP address

11. Error messages

In addition to the already mentioned error and warning messages there are a number of further messages which can occur in specific cases. Most messages concern errors or time delays of the communication. They shall not be reproduced here. If a message pops up frequently and you do not find a reason for that, please do not hesitate to contact us.