Dr. Tobias Binkele Profile

Dr. Tobias Binkele

Sales Engineer Mission Systems at OPTIMARE Systems GmbH

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Publications (9)

Proceedings Article | 2 March 2020 Presentation + Paper

Fast measurement of optical components using a PSD for experimental ray tracing

T. Binkele, D. Hilbig, M. Essameldin, T. Henning, F. Fleischmann

Proceedings Volume 11287, 112870V (2020) https://doi.org/10.1117/12.2542252

KEYWORDS: Sensors, Calibration, Optical components, Ray tracing, Optical testing, Signal detection, Time metrology, Geometrical optics, Laser beam propagation

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Proceedings Article | 15 November 2019 Presentation + Paper

Measurement of form and mid-spatial-frequency errors of specular freeform surfaces

T. Binkele, D. Hilbig, M. Essameldin, F. Fleischmann, T. Henning, W. Lang

Proceedings Volume 11175, 1117513 (2019) https://doi.org/10.1117/12.2536887

KEYWORDS: Optics manufacturing, Optical components, Manufacturing, Optical testing, Ray tracing

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Proceedings Article | 21 June 2019 Paper

Precise measurement of known and unknown freeform surfaces using Experimental Ray Tracing

Tobias Binkele, David Hilbig, Mahmoud Essameldin, Thomas Henning, Friedrich Fleischmann, Walter Lang

Proceedings Volume 11056, 110561N (2019) https://doi.org/10.1117/12.2526025

KEYWORDS: Reflection, Cameras, Data modeling, Ray tracing, Matrices, Process modeling, Systems modeling, Sensors, Optical components

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Lenses and mirrors with freeform surfaces are the latest step in the evolution of optical components. However, the measurement of these components still challenges metrology. We have developed a gradient-based measurement technique that is able to measure freeform specular surfaces either if their form is known or not. The measurement of freeform surfaces is a challenge for every measurement system. Especially if the form of the surface is not known in advance. Our measurement system can measure continuous freeform surfaces with up to 10° deviation from a plane surface even if the surface model is not known in advance. Therefore, a ray, represented by a narrow laser beam, is targeted on the surface under test (SUT) under a certain angle. Affected by its slope, the surface reflects the ray in a new direction. This direction is measured by using a variation of Experimental Ray Tracing (ERT). This includes the measurement of the position of the reflected ray in two parallel planes. Calculating the difference of the position on these planes, the direction of the ray in relation to them can be calculated. Having the direction of the reflected ray, as well as the direction of the incident ray, one can determine the surface normal at the point of reflection. By moving the SUT, the incident ray targets on a different point on the SUT. Therewith, various points are investigated. Using appropriate integration methods, the surface can be reconstructed. Although, with the introduction of the incident ray under a certain angle comes the issue, that the point of reflection changes with the sag of the SUT. This leads to an unequal distant measurement grid of points of reflection even if the SUT has been moved to equal distant sample points. This shift has to be considered for the reconstruction of the surface. This issue is solved in different ways for known or unknown surfaces. For an unknown surface, the investigated sample points are transferred into a coordinate system where they are equal distant. This is the coordinate system of the incident beam. Performing the integration here and transferring the reconstructed surface back into the coordinate system of the SUT leads to the expected shift of the sample points. For a known surface, the expected surface form is taken into account to determine the sample point shift. Therewith, the difference between the measured surface normals and the expected normals can be calculated and the integration can be performed only on the normal residuals. By adding the residuals to the model, the surface can be reconstructed. The measurement technique described above has been implemented in an experimental setup. To show the abilities of this technique, we will show the process of the measurement of a known and an unknown surface using the same sample. The results will be evaluated and compared.

Proceedings Article | 4 March 2019 Paper

Characterization of gradient index optical components using experimental ray tracing

Tobias Binkele, Rebecca Dylla-Spears, Michael Johnson, David Hilbig, Mahmoud Essameldin, Thomas Henning, Friedrich Fleischmann

Proceedings Volume 10925, 109250D (2019) https://doi.org/10.1117/12.2511072

KEYWORDS: Refractive index, GRIN lenses, Printing, Optics manufacturing, Wavefronts, Ray tracing, Phase shifts, Diffraction, Interferometry, Gradient-index optics

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Proceedings Article | 28 May 2018 Paper

Measurement of spherical, aspherical and freeform specular surfaces using experimental raytracing in simulation and measurement

Tobias Binkele, David Hilbig, Friedrich Fleischmann, Thomas Henning

Proceedings Volume 10695, 106950F (2018) https://doi.org/10.1117/12.2314924

KEYWORDS: Spherical lenses, Optical spheres, Calibration, Ray tracing, Optical testing, Data modeling, Reflection, Numerical integration, Freeform optics, Industrial metrology, Optical metrology, Metrology

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With the improved abilities in the manufacturing of optical components, including spherical, aspherical and freeform optics, measurement systems with high potential in accuracy and repeatability are required. In this work, enhanced improvements and abilities of the new measurement technique based on a variation of experimental ray tracing (ERT), recently introduced at the “SPIE – Optifab 2017”, are presented. The idea of ERT is to detect the direction of a ray, deflected by the device under test (DUT), by measuring its location in two known planes. Originally, this has been proposed to measure the function of lenses in transmission. The potential of this original idea is demonstrated in several papers considering the measurement of imaging lenses, objectives and progressive additional lenses. Relying on the experiences from these works, a variation of the original ERT is shown in this work. Therefore, a setup has been created using a ray, represented by a narrow laser beam, introduced into the measurement system under a certain angle. This ray is directed on the DUT. After the ray has been reflected from the specular surface, a camera chip catches this ray and determines its position. By moving the camera chip along a linear axis, the direction of the reflected ray is calculated. Performing this test for a high number of points on the DUT, the surface can measured completely. The advantage of this technique is the simplicity of the measurement principle. In contrast to other non-contact surface measurement techniques, no optical components are needed between the DUT and the measurement sensor. Thus, no errors can be introduced to the measurement results from defective optics in the measurement setup. Furthermore, using only the principle of reflection leads to the advantage, that no reference for the detection of the surface data is needed. Furthermore, the principle of single rays propagated through the measurement system opens up the area of computer vision. High efficient algorithms make the representation of the measurement data in the evaluation process fast and easy. With this measurement setup, the measurement of a huge variety of surfaces is possible. Spheres, aspheres and freeform optics can be measured all in the same way. However, certain limits are given from the measurement setup. The results are compared to the results of commercially available measurement systems.

Proceedings Article | 16 October 2017 Paper

Shape measurement of freeform surfaces using experimental ray tracing

T. Binkele, D. Vassmer, D. Hilbig, F. Fleischmann, T. Henning

Proceedings Volume 10448, 1044816 (2017) https://doi.org/10.1117/12.2279797

KEYWORDS: Ray tracing, Sensors, Optical spheres, Optical testing, Optical components, Lenses, Reflectivity, Reconstruction algorithms, Metrology

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Proceedings Article | 26 June 2017 Paper

Calibration of the incident beam in a reflective topography measurement from an unknown surface

Tobias Binkele, David Hilbig, Friedrich Fleischmann, Thomas Henning

Proceedings Volume 10329, 103291S (2017) https://doi.org/10.1117/12.2270291

KEYWORDS: Calibration, Cameras, Reflectivity, Deflectometry, Imaging systems, Precision measurement, Head, Ray tracing, Reflection, Optical calibration, Sensors, Signal detection, Zernike polynomials

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The precision of measurements as well as the need for precise measurements are increasing more and more. Thus, the importance of a good calibration of a setup is increasing, too. In the world of topography measurement a huge variety of techniques are available. Some of these techniques are using known shadow patterns reflected by the device under test (DUT). The reflected patterns are recorded using a camera with imaging optics. From the changes of the patterns, the topography can be resolved. Other measurement techniques are using a tactile sensing head, which is in contact with the surface to determine its topography. However, these techniques need a reference surface to calibrate movements. If this reference surface presents deviations from its expected form, errors are introduced.
We have developed a calibration method for reflective surface measurements based on experimental ray tracing (ERT) without the need of a reference surface. In our measurement setup, a narrow laser beam introduced in the measurement under a certain angle is reflected by the device under test. After the reflection the position and the direction of the ray in terms of the coordinate system of the camera is detected. Thus, no errors are introduced by using an additional imaging optic. To calibrate position and direction of the incident ray in respect to the coordinate system of the camera, the reflected rays from the measurement are used only. From these rays, the incident ray is determined by detecting the line, all reflected rays are intersecting with. This leads to two major advantages. First, there is no calibration run needed, since the measurement data can be used directly for the calibration. Second, for the calibration no well-known reference surface is needed. However, some regulations have to be considered for a stable process of this calibration method. In terms of peak-to-valley values of the sag of the surface as well as of the change of the surface slope, the surface has to show values deviating from zero. If a surface like this is measured, a separate measurement run can be performed using another surface fulfilling these requirements. Since the DUT is scanned by moving the DUT itself, the position and the direction of the incident ray is not changed from one measurement to another and can be reused. We describe the newly introduced calibration method for the incident ray in detail and present the necessary boundary conditions. The calibration has been tested using simulations and has been implemented in a measurement setup. Within this measurement setup, the expected performance resulting from the simulations has been examined.

Proceedings Article | 20 February 2017 Paper

Determination of the paraxial focal length using Zernike polynomials over different apertures

Tobias Binkele, David Hilbig, Thomas Henning, Friedrich Fleischmann

Proceedings Volume 10110, 1011008 (2017) https://doi.org/10.1117/12.2251442

KEYWORDS: Zernike polynomials, Photonics, Metrology, Wavefronts, Lens design, Ray tracing, 3D metrology, Monochromatic aberrations, Wavefront sensors, Sensors, Collimation

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Proceedings Article | 28 August 2016 Presentation + Paper

Determination of the paraxial focal length of strong focusing lenses using Zernike polynomials in simulation and measurement

Tobias Binkele, David Hilbig, Friedrich Fleischmann, Thomas Henning

Proceedings Volume 9960, 99600N (2016) https://doi.org/10.1117/12.2238059

KEYWORDS: Lenses, Wavefronts, Zernike polynomials, Ray tracing, Monochromatic aberrations, Lens design, Manufacturing, Tolerancing, Wavefronts, Zernike polynomials, Spherical lenses, Computer simulations

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