MRC Compact Laser Beam Stabilisation Installation Guide

: June 9, 2024
: MRC

Table of Contents

MRC Compact Laser Beam Stabilisation
Standard scope of delivery
Before the first operation
Introduction
Start of operation
Full operation
References
Read User Manual Online (PDF format)
Download This Manual (PDF format)

MRC Compact Laser Beam Stabilisation

This guide can assist you in setting up the beam stabilisation for the first time. It shows all main steps. For a more comprehensive description we refer to the user manual which you can find on the enclosed memory stick or download from our website www.mrc-systems.de/en.

Standard scope of delivery

The following table shows the standard scope of delivery of a 4-axis beam stabilisation. There are many optional functions and components for the system so that your individual scope of delivery might differ. You can find it on the packing list which you received with the system.

Component	Qty.	Component	Qty.
Compact controller	1	quick installation guide	1
Piezo-driven steering mirror mount with attached cable	2	extension cable for
actuator, length: 10m	1
position detector with embedded optical filters	2

2×2

Many customers order the optional interface and can connect a PC. These customers can use the communication and visualization software on the memory stick. To install the software you can follow the instructions in the software manual which is also on the memory stick.

Before the first operation

Please store the components for at least 24 hours in a dry environment before the first operation.

Introduction

A 4-axes beam stabilisation comprises two independent control stages each with a Piezo-driven actuator and a position detector. With these components you can either stabilize two positions along the beam path or one position and the angle.

Start of operation

You can follow the steps in the following sections to put the beam stabilisation into operation.

Stable setup of optical components
Our modular system allows various configurations of the optical components in the beam line. You can find detailed information and examples in the user manual.

Take care for stable posts, especially if you have large beam heights. This is important for the detectors in order to guarantee their high accuracy as well as for the steering mirror mounts in order to avoid oscillations.

Place the two pairs of steering mirrors and position detectors at suitable positions in your setup. Take care for sufficient distances between each mirror and the corresponding detector. We recommend distances of 0.5 m or more.

The detectors define the beam position. They need only low power and can (but don’t have to) be placed behind mirrors.
The first detector should be placed close to the second steering mirror. In that way it can fix the beam position on this mirror. If you have only little space you can add a lens and image the mirror’s surface onto the detector. You can find further examples in the user manual.

Connection of cables
Figures 1 and 2 show the side panels of the controller with the connections for the Piezo actuators, the power supply and the detectors.

Connect the first mirror actuator to Actuator 1 and the second mirror actuator to Actuator 2. Similarly, connect the first detector to Det1 and the second detector to Det2.

warning: If you use a detector in the lying / horizontal orientation, connect its x line to the y input and its y line to the x input.

Note: Some options can lead to a changed layout of the side panels and require additional cable connections.

Power connection
Connect the power supply to the 12V input at the controller. Switch on the controller by toggling the on/off-switch on the left side. After that the four green Range LEDs on the top of the controller should shine.

Adjustment of intensity on detectors

The detectors have LED indicators for the beam position and the intensity level on the back. You can adjust the intensity level by means of a poten- tiometer at the detectors’ housings. A screwdriver is included in the delivery. Turning the potentiometer counter-clockwise increases the gain.
In the optimal case you get 9 LEDs shining. If this is not possible, you can exchange the optical filters which are placed in front of the sensors or remove one of the two filters. However, it’s also possible to achieve a good stabilisation with less intensity.

Pre-adjustment of laser beam
Don’t activate the control stages (Active LEDs off), but adjust the laser beam onto the two detectors until you only see the central green LEDs of the position indicators. If you use the software you can also observe the positions in the displays there.

warning: The controller must be powered in this step in order to bring the Piezos into the zero position.

Direction coding
Now activate the first control stage by pushing the Start/Stop button on the keyboard of the controller (see figure 3) or in the software (see figure 4). The Active LED should shine now. MRC-Compact-Laser-Beam-Stabilisation-
fig-2

If red Range LEDs on the controller light up when you activate the stage (or the Range indicators in the software go to an extreme position), it is very likely that you have an incorrect direction coding. In this case toggle the corresponding Directions switch x or y at the controller (see figure 2). The Range indicators tell you which directions are affected.Once you have stage 1 running, apply the same steps for the second stage. MRC-Compact-Laser-Beam-
Stabilisation-fig-3

Fine-adjustment of stage 1
For the fine-adjustment inactivate both control stages once again by pressing the Start/Stop button (Active LEDs off). Manually adjust the laser beam by means of the adjustment screws of the steering mirrors or any other mirrors in your setup until it precisely hits the centers of the detectors. You can observe the LED crosses at the housings or the read-out of the x / y position outputs on the keyboard with an oscilloscope. If your system is equipped with the communication interface, you can also read out the positions via the software. The outputs provide voltages which reflect the deviation from the target position. The voltages should be close to 0 V. Good values are typically 10 – 100 mV, depending on the beam fluctuations without stabilisation.

warning: The better the zero position in the inactive state (Active LEDs off) matches the target position, the smaller will be the beam shift when you activate the stabilisation.

Fine-adjustment of stage 2
Activate only stage 1 by pressing its Start/Stop button. Leave stage 2 inactive. Proceed with stage 2 as you did with stage 1.

Full operation

After this step the Piezos have their largest tilting range into each direction. For the stabilized 4 axes operation you can now activate both stages. With activated control the laser beam should show no fluctuations of the beam position after the last mirror.

Determination of accuracy
The position outputs of the controller provide voltages which reflect the deviation from the target position. In the user manual you can find equations on how you can calculate real positions from these voltages. In the software you can switch between voltages and positions in µm.

Optional: Optimization of bandwidth
At the controller you find two potentiometers P1 and P2 for adjustment of the P factors of both control stages (see figure 2). The factors can also be changed in the software. With the P factors you can optimize the stabilisation bandwidth. You can again use the delivered screwdrivers to turn the potentiometers. Make sure that both stages are active (Active LEDs on). Turn P1 in clockwise direction until the position on detector 1 starts to oscillate. Then reduce the P factor until the oscillation stops and a stable operation is guaranteed. Do the same with P2 for stage 2.

warning: At the right side of the controller there are also the Bandwidth switches L (low) and H (high). Usually you can choose the H position. However, if your setup tends to oscillate e.g. due to unstable mechanical mounts or a mixing between the two control stages it can be of advantage to choose L. The switches independently adjust the P factors of both stages with a large step.

If it doesn’t work right away

If you observe problems with the stabilisation you may have a suboptimal setup. Please consider the section “Set-up of optical components” in the user manual. You can also check the section “Troubleshooting” at the end of the manual.

Please don’t hesitate to contact us in case of questions: