ESAD Shearing Deflectometry: A Primary Flatness Standard with Sub-Nanometer Uncertainty

Ralf D. Geckeler

doi:10.4028/www.scientific.net/KEM.381-382.543

Paper Titles

Nanomechanical Properties and Nanostructure of CMG and CMP Machined Si Substrates
p.525

Development of Nanometrology for Nanoelectronics: Growth and Characterization of Transition Metal Monolayer Films on Silicon
p.529

On the Measurement of Dielectric Constant of Coatings with Capacitance Sensors
p.533

Broadband Dielectric Properties of the Ba₃MnTa₂O₉Complex Perovskites
p.537

ESAD Shearing Deflectometry: A Primary Flatness Standard with Sub-Nanometer Uncertainty
p.543

Achieving Nanorad Level Stability of Beam Deflection with Scanning Pentaprisms
p.547

Traceable Dimension Metrology by AFM for Nanoscale Process Control
p.549

Test Artefacts for the Verification of Optical Digitizers
p.553

Kalman Filter for Estimation of a Linear Regression Model with Account of the Regression Vector Error and its Application to Calibration of Measuring Instruments
p.557

HomeKey Engineering MaterialsKey Engineering Materials Vols. 381-382ESAD Shearing Deflectometry: A Primary Flatness...

ESAD Shearing Deflectometry: A Primary Flatness Standard with Sub-Nanometer Uncertainty

Abstract:

To overcome the limitations of conventional interferometry, a technique has been developed which allows the absolute topography measurement of near-plane and slightly curved optical surfaces of arbitrary size with low measurement uncertainty. The Extended Shear Angle Difference (ESAD) method combines deflectometric and shearing techniques in a unique way to minimize measurement errors and to optimize measurand traceability. A device for the topography measurement of optical surfaces up to 500 mm in diameter, achieving sub-nanometer repeatability, reproducibility and uncertainty, was built at the Physikalisch-Technische Bundesanstalt (PTB). The ESAD method is optimally suited for creating a primary standard for straightness and flatness with highest accuracy by which the three-flat test or liquid mirrors can be replaced as starting points of the traceability chain in flatness measurement. In the following, the improved ESAD device which uses optimized opto-mechanical components is presented. Central aspects of the proper design and use of deflectometric systems are highlighted, including the optimal use of pentaprisms.