Surface Slope Metrology: High Precision Tilt Stage Achieves 30nrad Absolute Accuracy

Back to PI WebsiteA recent paper shows significant advances in the accuracy of long trace profilers, auto-collimator based deflectometers, and other surface metrology instrumentation. Scientists at the ALS X-Ray Optics Laboratory, HZB/BESSY-II and PTB devised a new universal calibration method for deflectometers.  One key component in the system is a high accuracy, piezo-motor-driven flexure tilt stage developed in collaboration with PI (Physik Instrumente). Overall absolute accuracy of better than 30nrad over the entire instrumental dynamic range was achieved.  The flexure stage is made of invar for higher long-term stability and equipped with a pair of 60-picometer resolution SONY LASERSCALE® linear encoders, fed back to a modified E-712 digital piezo controller. The differential evaluation cancels out parasitic linear errors to get the best possible reading of the true angular values.

The PI N-310K021 flexure-guided, invar tilt stage is driven by a nanometer-precision piezowalk motor. (Source: AIP|Scitation)
The PI N-310K021 flexure-guided, invar tilt stage is driven by a nanometer-precision piezowalk motor. (Source: AIP|Scitation)

 

Step/settle and repeatable small angle resolution performance test of the tilt stage. The graph shows the response of the stage to a 1Hz target input with a 30nrad peak-peak amplitude. The highest resolution is 10nrad. (Source: AIP|Scitation)
Step/settle and repeatable small angle resolution performance test of the tilt stage. The graph shows the response of the stage to a 1Hz target input with a 30nrad peak-peak amplitude. The highest resolution is 10nrad. (Source: AIP|Scitation)

 

Closed-loop angular stability test of the tilt stage shows precision equivalent to a standard deviation of σ = 4nrad (Source: AIP|Scitation)
Closed-loop angular stability test of the tilt stage shows precision equivalent to a standard deviation of σ = 4nrad (Source: AIP|Scitation)

 

The heart of the piezowalk linear motor: The operating principle is based on coordinated motion of a number of preloaded piezo elements acting on a ceramic runner as shown in the animation seen here. (Images: PI)
The heart of the piezowalk linear motor: The operating principle is based on coordinated motion of a number of preloaded piezo elements acting on a ceramic runner as shown in the animation seen here. (Images: PI)

 

The piezowalk drive principle is also available in miniaturized linear positioners, such as the N-565 series shown above. (Image: PI)
The piezowalk drive principle is also available in miniaturized linear positioners, such as the N-565 series, shown above. (Image: PI)

 

Read the full article here: http://scitation.aip.org/content/aip/journal/rsi/87/5/10.1063/1.4950729

 

 

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About PI

PI (Physik Instrumente) is a leading manufacturer of precision motion control equipment, piezo motors, air bearing stages and hexapod parallel-kinematics for semiconductor applications, photonics, bio-nano-technology and medical engineering. PI has been developing and manufacturing standard & custom precision products with piezoceramic and electromagnetic drives for 4 decades. The company has been ISO 9001 certified since 1994 and provides innovative, high-quality solutions for OEM and research. PI is present worldwide with fifteen subsidiaries, R&D / engineering on 3 continents and total staff of more than 1,000.

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