Impact of detector position accuracy on the MTF measurement of optical lenses

Simone Fohrmann; Patrik Erichsen; Markus Schake; Michael Schulz

doi:10.1117/12.2602744

28 October 2021 Impact of detector position accuracy on the MTF measurement of optical lenses

Simone Fohrmann, Patrik Erichsen, Markus Schake, Michael Schulz

Proceedings Volume 11889, Optifab 2021; 118890A (2021) https://doi.org/10.1117/12.2602744
Event: SPIE Optifab, 2021, Rochester, New York, United States

Abstract

Despite the strong demand for high-precision Modulation Transfer Function (MTF) measurements for industrial and scientific applications, currently there is a lack of MTF calibration services traceable to national standards. Trioptics GmbH, in cooperation with the National Metrology Institute in Germany (PTB), is establishing an accredited laboratory for traceable MTF measurements of optical lenses aiming at an expanded uncertainty of 𝑈_MTF= 0.01 for coverage factor 𝑘 = 2. To reach this goal, influences of misalignment and mechanical stage positioning errors need to be considered. We present an experimental approach to investigate the influence of the detector’s positioning accuracy on the MTF measurement uncertainty depending on the imaging properties of individual lenses under test. For samples with different optical properties (effective focal length and aperture), the MTF is measured at various positions in a 2D grid spanned over image field and focusing direction. At each position, the derivatives of MTF in field and focusing direction are calculated. Knowing the overall mechanical uncertainty of the detector, this data can be used to determine local uncertainties of the measured MTF. In contrast to the classical way of defining measurement uncertainty only by benchmarking the accuracy of the measurement equipment, we now include MTF-sensitivity of the sample under test. Hereby, a more precise and application-oriented analysis of the MTF accuracy for a measurement system can be achieved.

Conference Presentation

Citation Download Citation

Simone Fohrmann, Patrik Erichsen, Markus Schake, and Michael Schulz "Impact of detector position accuracy on the MTF measurement of optical lenses", Proc. SPIE 11889, Optifab 2021, 118890A (28 October 2021); https://doi.org/10.1117/12.2602744

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