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- Page 1 µAligna Manual TEM Messtechnik GmbH February 19, 2020 TEM Messtechnik GmbH Grosser Hillen 38 D-30559 Hannover Tel: +49 (0)511 51 08 96 -30 Fax: +49 (0)511 51 08 96 -38 E-mail: mailto:info@TEM-messtechnik.de URL: http://www.TEM-Messtechnik.de...
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Page 3: Table Of Contents
µAligna Manual Contents 1 Introduction 2 Hardware Description 2.1 µAligna Block Diagram ....... . 2.2 Back Panel Elements . - Page 4 µAligna Manual A Principles of Beam Pointing Stabilization A.1 Reasons for Pointing Instabilities ......28 A.1.1 Thermal Properties of the Laser .
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Page 5: Introduction
µAligna Manual Introduction TEM Messtechnik’s µAligna is a multi-purpose device for controlling and stabilizing optical elements. Its ability to drive up to eight stepper motors allows it to control rotational actuators such as po- larizing filters, as well as linear actuators such as mirror mounts. The µAligna device also features freely-assignable digital-to-analog converters which can, for instance, provide the input signals for HV-amplifiers and thus control piezo-actuators. -
Page 6: Hardware Description
µAligna Manual Hardware Description µAligna Block Diagram At the heart of the µAligna device lies a micro-controller, which handles all communications over the USB interface and over the I C or SPI bus. It also does most of the signal processing, such as the implementation of PID-regulators, the generation of control signals for micro-stepper motors or digital filtering. - Page 7 DC 9..24 V TEM Messtechnik GmbH, +49 (0)511 / 510896 30 Grosser Hillen 38, 30559 Hannover (Germany) Figure 2: Back panel elements. 1 USB USB communication with a PC, configured as a virtual COM port...
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Page 8: Software Installation
Files” folder. On Windows Visa or Windows 7 systems, please avoid the “Program Files” folder and choose and a different path, for example “C:/TEM”. The button “OK, install now!” starts copying all required files from the source path to the destination path. During the installation procedure, the installation program checks all required files. -
Page 9: Installing The Usb Drivers
Found New Hardware Wizard. Here, choose to install drivers from a user-specified location. The necessary driver file is located in the directory “TEM/Service/USB Driver” in the Kangoo installation directory (or on the install CD). The Hardware Wizard will now finish the installation and no further configuration will be necessary. -
Page 10: Basic Operation
µAligna Manual Basic Operation Using the Kangoo Software The alignment of the parameters of a µAligna system is most easily done with the supplied software package Kangoo. Since the µAligna device is controlled by plain-text commands, it can be config- ured with any control software like LabView, TestPoint, or other programs written in VisualBasic, C++, C#, etc. -
Page 11: Configuration "Learn Ocl Motors
µAligna Manual Figure 3: Kangoo configuration “Aligna User Menu” intensities. “PSD A gain” and “PSD B gain” should always be adjusted such that the two intensity meters show about five volts. The button “AutoGain” below the intensity meters automatically adjusts both gains. Similar to the gains, there are offsets associated to each detector chips. With these offsets, the beam can be stabilized to positions other than the detectors’... - Page 12 µAligna Manual Figure 4: Kangoo configuration “BeamLock Basic” when a µAligna system is first set up in a new optical layout, a new OCL matrix must be determined. Figure 5: Kangoo configuration “measure OCL matrix” The Kangoo software can perform a measurement cycle to automatically determine the correct matrix.
- Page 13 µAligna Manual hit by the laser. Use the two intensity indicators to the left of the scope to verify this. Hit the “AutoGain” button, which should adjust both intensity indicators to about 5V . Next, try to roughly align both angle and position of the beam to the detectors’ centers (say to within 2V ).
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Page 14: Piezo "Ocl Matrix
µAligna Manual Figure 8: Measurement results with a roughly correct OCL matrix It is recommended to re-run the learning procedure in order to improve the OCL matrix. Typically, the learning procedure should be run three times: Once to determine a good OCL matrix, a second time to improve residual errors and a third time just to verify the results (there is no need to correct the OCL when the results look good). -
Page 15: Enabling The Piezo Regulator
µAligna Manual 4.1.5 Enabling the Piezo Regulator After a satisfactory learning procedure, it is recommended to test the regulation. This is done by pressing the large “RegOn” indicator and the small Piezo enable indicator to the right of it. If your system has motor and piezo actuators, please also enable the motor regulator before saving the parameters to ensure that motors and piezos are both active. - Page 16 µAligna Manual ˆ a test laser ˆ the mirror mounts with actuators and mirrors (with aluminum coating for testing purposes only) ˆ the 4D detector ˆ a beam sampler plate (for testing only) ˆ two apertures, representing your experimental setup The acrylic glass parts of the Plug &...
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Page 17: Advanced Operation
µAligna Manual Advanced Operation The detector delivered with a µAligna system measures the beam pointing in four dimensions, namely beam angle (A and A ) and beam position (B and B ). To this end, it contains two separate detector chips, A and B. In addition to these four pointing values, the detector measures the intensities at both chips, labelled Sum and Sum . -
Page 18: Gains And Offsets
µAligna Manual ˆ In most applications, both values (1 % and 8 %) lead to test beam intensities far above the necessary intensities. These test beam intensities have to be reduced by strong optical filters, and they are lost for the main beam. With horizontally polarized laser light, it is possible to get very low reflections by using a reflection angle around Brewster’s angle, 57 . -
Page 19: Calibration
µAligna Manual Figure 11: Kangoo section for setting thresholds. the current intensity values lies outside the minimum or the maximum threshold, the regulator stops working. This is a safety feature, to ensure for example that the regulator does not react to environment light when the laser is blocked. - Page 20 µAligna Manual Figure 12: Location of the cw/pulsed device the regulator. After that, the regulator goes into a hold state until the next pulse is detected. Therefore, the µAligna electronics work with arbitrarily low repetition rates. At low repetition rates, it may be necessary to tune the regulator gains for optimal performance. Setting up the pulsed detection To understand how to set up the pulsed detection of the µAligna we explain the detection principle of pulsed lasers used for our pointing stabilization.
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Page 21: Actuators
µAligna Manual Therefore the system only takes one sample after a Pulse-Delay at repetition rates above 4 kHz (see Figure 14). Please note that the detected beam pointing may vary if you change between the two sampling methods because the single sampling will add the environmental light to the detection. Figure 14: Single sampling above 4 kHz To set the correct delays set the repetition rate of the system to a value 4 kHz. -
Page 22: Motor Offsets
µAligna Manual The µAligna electronics are designed to drive motorized mirror mounts with micro-stepping actua- tors. The standard supplied actuators, Aligna60, are shown in Figure 15. They feature ultra-high resolution micro-stepping operation, a large angle range and optical end-switches which provide an absolute reference position. -
Page 23: Tuning The Piezo Regulator
At present, the Kangoo software cannot visualize the effects of changing the regulator settings. We recommend TEM-Messtechnik’s Aligna CON box, which breaks out the PSD detector signals to BNC plugs, and an oscilloscope. From within Kangoo, the regulator setpoints can be user-adjusted. - Page 24 0 to 1 flag to activate the stabilization RegOnOff 10 to 1000000 gain in percent for a TEM angle PSD PsdAgain 10 to 1000000 gain in percent for a TEM position PSD PsdBgain -1000 to 12000 minimum intensity for the stabilization...
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Page 25: Connectors And Electrical Specifications
µAligna Manual Connectors and Electrical Specifications Environmental Conditions The device has been designed for operation in laboratory environments with temperatures ranging between +15 C and + 45 C. The device is not to be operated in hazardous environments. Avoid exposure to heat or to emissions of other electric equipment. Protect the system against humidity, dust, aggressive fluids or vapors. - Page 26 µAligna Manual PSD input motor outputs piezo outputs Diff motor Diff motor Diff motor Diff motor 5 analog GND switch +15V +15V -15V -15V I C clock switch I C data switch HV GND motor output X motor output Y motor motor SPI clock...
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Page 27: Safety Instructions
µAligna Manual Safety Instructions Before operating the µAligna, please read this user guide carefully in order to avoid any damage of the device or connected equipment as well as any injury to persons. CAUTION! The µAligna device is intended for laboratory use only. The µAligna device should be operated by trained personnel. -
Page 28: Appendices
µAligna Manual Appendices Principles of Beam Pointing Stabilization Reasons for Pointing Instabilities Laser beams, used in experiments or in industrial applications, can move in space for many reasons. Even small movements at the laser outlet may result in rather large movements of the laser spot, depending on the distance to the target and on the optical components in the beam path. -
Page 29: Air Turbulences And Temperature Gradients In The Air
µAligna Manual changes of the environment temperature, the different thermal expansions can lead to position and — more critically — angle movements of the laser beam. The extend of these effects strongly depends on the construction, the materials, and of course on the temperature variations of the environment. -
Page 30: Or 4D Stabilization
µAligna Manual 2D or 4D Stabilization The movement of a collimated beam can be separated into four dimensions: two translational (“X”, “Y ”) and two rotational (“α”, “β”) degrees of freedom. These degrees of freedom are not really independent: If, for example, one mirror mount drifts by 100µrad due to a change in the room temperature, then the translation error will be negligible close to the mirror. - Page 31 µAligna Manual However, the detector has to be positioned in an exact image of the target. Thus, its mechanical alignment has to be very precise. Often it is difficult to find the correct z position for the detector. If this z position is wrong, the stabilization can even increase the pointing fluctuations, rather than reduce them (see Figure 19).
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Page 32: Actuator Placement
µAligna Manual Actuator Placement The µAligna system is very tolerant when it comes to actuator and detector placement. Naturally, the PSD-4D should be placed as close as possible to the experimental target, since any disturbances after the detector cannot be compensated for. Furthermore, observing the following points will lead to the best system performance. -
Page 33: Customer Service
µAligna Manual Customer Service In case of service needs, general questions, need of repair or warranty claims you will get quick and effective support at: TEM Messtechnik GmbH Grosser Hillen 38 D-30559 Hannover Germany Tel: +49 (0)511 51 08 96 -30 Fax: +49 (0)511 51 08 96 -38 E-mail: mailto:info@TEM-messtechnik.de... - Page 34 µAligna Manual Notes Aligna Manual 34 / 34 February 19, 2020...