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Motion Control

NanoTrak™ “Auto-Aligment System” Tutorial… page 2 of 2

Translation StagesMotorized device piezoelectric actuators to drive thecomponent into alignment (in the direction of increasing signal).When the device is centered on the signal peak,the signal gradient around the circle of motion is zero and the NanoTrak™ has achieved optimalcoupling of the device under its control. At thispoint the NanoTrak™ “dithering” can be suspended (outputs latched) for static alignment requirements or dithering continued at smaller amplitudes for active continuous alignment inapplications that suffer from drift.The speeds of response of the control unit and thepiezo-controlled nanopositioners are measured in milliseconds, and consequently, the time taken from signal acquisition (when the scanning covers the maximum area) to achieve alignment andmaximum optical transmission is of the order oftens of milliseconds.
Mirror Mounts , the vertical motion is at the maximum, however, the powerdoes not reach a maximum until t
1 . Similarly, the motion is at a minimum at timet
Rotation Stages3 Axis Flexure Stages 2 , whereas the minimum power is not reached until t
3 . Therefore, the optical powerlags the vertical motion by a phase angle (figure 4).Therefore, it is by detecting the phase of the optical power signal, that theNanoTrak™ can automatically align two components. Once the NanoTrak™ hasfound the maximum signal, it locks on to it, and even if one of the components is moved slightly, the NanoTrak™ corrects for the movement to maintain the maximum power. Phase Sensitive Detection
& Accessories By considering only the vertical component of the motion and plotting the amplitude against time, this produces a sine wave, as shownbelow (figure 3). At t
4, 5 & 6-Axis Stages Drive Electronics& Auto-Alignment Actuators & Adjusters Figure 4 Phase angle between opticalpower and vertical motion

Summary

The NanoTrak™ from Thorlabs can automatically align fibers to devices such as waveguides in less thanone second. It can dramatically simplify characterisation and pigtailing procedures, and can ensure drift-free positioning and accurate data acquisition. By using the NanoTrak™ in autoalignment systems there are significant advantages to be gained because of the improvement in the alignment process.
â–  Scanning and Searching to Find a Transmitted Optical Signal
â–  Rapidly Acquiring a Throughput Optical Signal
â–  Maximizing the Optical Signal Through Constant Adjustment of the Appropriate Position ofthe Piezo Actuators
â–  Active “Real Time” Compensating of Mechanical Cross-talk on Multi-axis Stage Mechanisms byVirtue of Optical Signal Feedback Loop
â–  Similarly Active Correction of Positional Changes Caused by Environmental Disturbances Such asTemperature Change and Vibration Figure 3Optical power and verticalmotion as a function of time
â–  Countering Bonding Forces During Pigtailing Operation, Eliminating Erratic UV Curing andOther Undesirable Effects

Tools of the trade - Vol 18 - 36188 TOOLSOF THETRADE

6-Axis NanoPositioning Stages& ControllersSee Pages 309-323 & 352

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