Publications by Wilfried Noell

Tolerancing the surface form of aspheric microlenses manufactured by wafer-level optics techniques

Toralf Scharf, Wilfried Noell, Jeremy Béguelin

Tolerancing is an important step toward the fabrication of high-quality and cost-effective lens surfaces. It is critical for wafer-level optics, when up to tens of thousands microlenses are fabricated in parallel and whose surfaces cannot be formed individ ...

OPTICAL SOC AMER2020

Optical characterization of high numerical aperture microlenses for quality assessment and fabrication process optimization

Toralf Scharf, Wilfried Noell, Jeremy Béguelin

Accurate characterization of high numerical aperture aspheric microlenses currently is a nonstandard procedure that remains an open challenge. Here, we present and discuss a characterization method based on interferometric and point spread function measure ...

OPTICAL SOC AMER2020

Correction of spherical surface measurements by confocal microscopy

Toralf Scharf, Wilfried Noell, Jeremy Béguelin

Refractive microlenses are nowadays widely used in optical systems. Characterizing their surface is essential to ensure their quality and to optimize their fabrication process. This is realized by optical surface profilers thanks to their vertical resoluti ...

2020

Specification of aspherical surfaces used as refractive elements in micro-optical systems

Toralf Scharf, Wilfried Noell, Jeremy Béguelin

The optical performance of refractive plano-convex microlenses is mainly related to the quality of their (a)spherical surface. An efficient tolerancing of this surface is a key step towards the manufacturing of high quality microlenses. However, we demonst ...

SPIE-INT SOC OPTICAL ENGINEERING2019

Leveraging wafer-level manufacturing process limitations to increase large scale fused silica microlens array uniformity

Toralf Scharf, Wilfried Noell, Raoul Kirner, Jeremy Béguelin

The wafer-level production of Fused Silica microlens arrays is limited by systematic process non-uniformities. The common molten resist-reflow process with subsequent dry-etching allows for manufacturing of microlens arrays on 200 mm wafers. A thorough pro ...

SPIE-INT SOC OPTICAL ENGINEERING2019

Correction of surface error occurring in microlenses characterization performed by optical profilers

Toralf Scharf, Wilfried Noell, Jeremy Béguelin

Characterizing the surface of microlenses by optical profilers has the important advantages of measurement speed, flexibility and automation. Nevertheless, the accuracy of such characterization is limited by error occurring in non-flat measurements. Here, ...

SPIE-INT SOC OPTICAL ENGINEERING2019

Spatial coherence properties of an LED-based illumination system for mask-aligner lithography

Hans Peter Herzig, Toralf Scharf, Wilfried Noell, Raoul Kirner, Johana Bernasconi

A high-power LED-based illumination system has been developed as a replacement for the mercury arc lamps used in mask-aligner lithography. LEDs are arranged in a grid array and placed in the entrance aperture of individual reflectors. Those reflectors decr ...

SPIE2019

Computational rule-based approach for corner correction of non-Manhattan geometries in mask aligner photolithography

Toralf Scharf, Wilfried Noell, Chen Yan, Raoul Kirner, Andreas Vetter

In proximity mask aligner photolithography, diffraction of light at the mask pattern is the predominant source for image shape distortions such as line end shortening and corner rounding. One established method to mitigate the impact of diffraction is opti ...

2019

Improvements on the uniformity of large-area microlens arrays in Fused Silica

Toralf Scharf, Wilfried Noell, Raoul Kirner, Jeremy Béguelin

The uniformity of large microlens arrays in Fused Silica is governed by the production process. It comprises photolithographic patterning of a spin-coated layer of photoresist on a 200mm wafer with a molten resist reflow process and subsequent dry etching. ...

OPTICAL SOC AMER2019

Printing sub-micron structures using Talbot mask-aligner lithography with a 193 nm CW laser light source

Toralf Scharf, Wilfried Noell, Raoul Kirner, Andreas Vetter

A continuous improvement of resolution in mask-aligner lithography is sought after to meet the requirements of an ever decreasing minimum feature size in back-end processes. For periodic structures, utilizing the Talbot effect for lithography has emerged a ...

2018