Testing the Geometry of Optical Components

Groß, Herbert; Dörband, Bernd; Müller, Henriette

doi:10.1002/9783527699230.ch8

Cited by 2 publications

(2 citation statements)

References 64 publications

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“…The surface of microlenses can be divided into two qualitatively different components: 22 first, the surface form or figure, 23 which contains the low spatial frequencies of the surface and shapes the wavefront; and second, the roughness, which contains the high spatial frequencies and is mainly responsible for light scattering. [24][25][26] This specific division is not absolute and there is no general admitted rule to determine the cutoff frequency between these two regimes.…”

Section: Microlens Surfacementioning

confidence: 99%

Commented review on refractive microlenses and microlens arrays metrology

Béguelin

Voelkel

Scharf

2021

J. Optical Microsystems

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The fabrication of high-quality microlenses is possible only when it is assisted by efficient and accurate metrology. For this reason, developing expertise in measurement procedures is crucial for the micro-optics manufacturer. We review and comment on this topic by first discussing what features of microlenses must be characterized and controlled. We then review the existing techniques and instruments that can be employed for this task. Finally, we detail the limitations of these different methods, we compare them, and we propose practical guidelines to setup effective metrology methodology. We believe that this paper can be an introduction to the topic but also serves as a reference document for the more experienced reader. © The Authors.Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Section: Microlens Surfacementioning

confidence: 99%

Commented review on refractive microlenses and microlens arrays metrology

Béguelin

Voelkel

Scharf

2021

J. Optical Microsystems

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“…An example of a local plane approximation for a sphere is presented on the right. diffraction limited microlenses, surface deviations RMS in the order of 50 nm have to be measured [18]. The exact value depends on the microlens material and on the operating wavelength.…”

Section: Surface Error Investigationmentioning

confidence: 99%

Correction of spherical surface measurements by confocal microscopy

Béguelin

Scharf

Noell

et al. 2020

Meas. Sci. Technol.

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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 resolution, short measurement time and areal information. However, when measuring non-flat surfaces, errors appear caused by aberrations of the microscope objective used in such systems, which significantly limit the achievable quality of the manufactured spherical surfaces. Approaches have been proposed to tackle these errors, but none of them demonstrated its validity for measurements of high quality microlenses. In this work, we demonstrate that the surface error depends on the surface position within the field of view of the microscope objective and on the surface slope. We then explain how to record the value of this error experimentally: this can be done by measuring a reference ball placed at different positions in the field of view. We finally use a machine learning algorithm to fit the experimental data in order to correct subsequent measurements. We apply this approach to measurements performed by a 20× numerical aperture 0.6 microscope objective of a confocal microscope. The effectiveness of the proposed method is demonstrated by showing that the surface error corresponds to a RMS wavefront error of λ/7 before correction and of λ/50 after correction for glass microlenses used in the visible range. This method thus allows the use of high numerical aperture microscope objectives for an accurate characterization of microlenses. Likewise, the fabrication capability of microlenses in terms of slope and quality is greatly extended, which is especially important for aspheres or freeforms.

show abstract

Testing the Geometry of Optical Components

Cited by 2 publications

References 64 publications

Commented review on refractive microlenses and microlens arrays metrology

Commented review on refractive microlenses and microlens arrays metrology

Correction of spherical surface measurements by confocal microscopy

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