2020
T. Feng P.K Sahoo, M. Sharma; Qiao, J.
Dynamic modelling for predicting temperature evolution and modification during fs-laser welding of borofloat glass Conference
vol. ATu3K.2, C:EO 2020 OSA 2020.
Abstract | BibTeX | Tags: CeFO, CeFO manufacturing, Freeform surfaces, Optical surfaces
@conference{CLEOc,
title = {Dynamic modelling for predicting temperature evolution and modification during fs-laser welding of borofloat glass},
author = {P.K Sahoo, T. Feng, M.Sharma, S. Patra, R.Haque, and J. Qiao},
year = {2020},
date = {2020-06-01},
volume = {ATu3K.2},
organization = {C:EO 2020 OSA},
abstract = {A dynamic heat accumulation modelling for femtosecond laser welding of Borofloat glass is developed
and verified experimentally. The temperature evolution and internal modifications are predicted by incorporating
the nonlinear electron dynamics along with temperature dependent thermal properties.},
keywords = {CeFO, CeFO manufacturing, Freeform surfaces, Optical surfaces},
pubstate = {published},
tppubtype = {conference}
}
A dynamic heat accumulation modelling for femtosecond laser welding of Borofloat glass is developed
and verified experimentally. The temperature evolution and internal modifications are predicted by incorporating
the nonlinear electron dynamics along with temperature dependent thermal properties.
and verified experimentally. The temperature evolution and internal modifications are predicted by incorporating
the nonlinear electron dynamics along with temperature dependent thermal properties.
2019
JING XU LAUREN L. TAYLOR, MICHAEL POMERANTZ; QIAO, JIE
Femtosecond laser polishing of germanium Journal Article
In: Optical Materials Express, vol. 9, no. 11, pp. 4165-4177, 2019.
Abstract | Links | BibTeX | Tags: CeFO manufacturing, CEFO metrology, fabrication, Freeform surfaces, manufacturing, Mid-Spatial Frequency error
@article{TAYLOR2019,
title = {Femtosecond laser polishing of germanium},
author = {LAUREN L. TAYLOR, JING XU, MICHAEL POMERANTZ, THOMAS
R. SMITH, JOHN C. LAMBROPOULOS, AND JIE QIAO},
url = {https://doi.org/10.1364/OME.9.004165},
year = {2019},
date = {2019-10-02},
journal = {Optical Materials Express},
volume = {9},
number = {11},
pages = {4165-4177},
abstract = {Freeform optics can reduce the cost, weight, and size of advanced imaging systems,
but it is challenging to manufacture the complex rotationally asymmetric surfaces to optical
tolerances. To address the need for disruptive, high-precision sub-aperture forming and finishing
techniques for freeform optics, we investigate an alternative, non-contact polishing methodology
using femtosecond lasers, combining modeling, experiments, and demonstrations. Femtosecondlaser-
based polishing of germanium was investigated using an experimentally-validated twotemperature
model of laser/germanium interaction to guide the understanding and selection of
laser parameters to achieve near-nonthermal ablation for polishing and figuring. For the first time
to our knowledge, model-guided femtosecond laser polishing of germanium was successfully
demonstrated, achieving precision material removal while maintaining single-digit nanometer
optical surface quality. The demonstrated femtosecond-laser-based polishing technique lays the
foundation for semiconductor optics polishing/fabrication using femtosecond lasers and opens a
viable path for high-precision, complex sub-aperture optical polishing tasks on various materials.},
keywords = {CeFO manufacturing, CEFO metrology, fabrication, Freeform surfaces, manufacturing, Mid-Spatial Frequency error},
pubstate = {published},
tppubtype = {article}
}
Freeform optics can reduce the cost, weight, and size of advanced imaging systems,
but it is challenging to manufacture the complex rotationally asymmetric surfaces to optical
tolerances. To address the need for disruptive, high-precision sub-aperture forming and finishing
techniques for freeform optics, we investigate an alternative, non-contact polishing methodology
using femtosecond lasers, combining modeling, experiments, and demonstrations. Femtosecondlaser-
based polishing of germanium was investigated using an experimentally-validated twotemperature
model of laser/germanium interaction to guide the understanding and selection of
laser parameters to achieve near-nonthermal ablation for polishing and figuring. For the first time
to our knowledge, model-guided femtosecond laser polishing of germanium was successfully
demonstrated, achieving precision material removal while maintaining single-digit nanometer
optical surface quality. The demonstrated femtosecond-laser-based polishing technique lays the
foundation for semiconductor optics polishing/fabrication using femtosecond lasers and opens a
viable path for high-precision, complex sub-aperture optical polishing tasks on various materials.
but it is challenging to manufacture the complex rotationally asymmetric surfaces to optical
tolerances. To address the need for disruptive, high-precision sub-aperture forming and finishing
techniques for freeform optics, we investigate an alternative, non-contact polishing methodology
using femtosecond lasers, combining modeling, experiments, and demonstrations. Femtosecondlaser-
based polishing of germanium was investigated using an experimentally-validated twotemperature
model of laser/germanium interaction to guide the understanding and selection of
laser parameters to achieve near-nonthermal ablation for polishing and figuring. For the first time
to our knowledge, model-guided femtosecond laser polishing of germanium was successfully
demonstrated, achieving precision material removal while maintaining single-digit nanometer
optical surface quality. The demonstrated femtosecond-laser-based polishing technique lays the
foundation for semiconductor optics polishing/fabrication using femtosecond lasers and opens a
viable path for high-precision, complex sub-aperture optical polishing tasks on various materials.
Horvath, Nicholas W.; Davies, Matthew A.; Patterson, Steven R.
In: Precision Engineering, vol. 60, pp. 535-543, 2019.
Abstract | Links | BibTeX | Tags: CeFO, CeFO manufacturing, CEFO metrology, Freeform surfaces, Kinematic Coupling
@article{Horvath19-a,
title = {Kinematic mirror mount design for ultra-precision manufacturing, metrology, and system level integration for high performance visible spectrum imaging systems},
author = {Nicholas W. Horvath and Matthew A. Davies and Steven R. Patterson},
url = {https://doi.org/10.1016/j.precisioneng.2019.09.011},
year = {2019},
date = {2019-09-20},
journal = {Precision Engineering},
volume = {60},
pages = {535-543},
abstract = {High-performance freeform optical systems, designed for broad spectral imaging from the visible to the far infrared, place new demands on optical design, precision manufacturing, and precision metrology. To meet the tolerances on figure, roughness, and relative positioning in such systems requires the ability to perform metrology and manufacturing corrections on freeform optics in a continuous feedback loop. This feedback loop requires a common interface for machining and manufacturing platforms. This paper describes the design, analysis, and testing of such an interface suitable for use with single point diamond turning and deterministic micro-grinding. The interface utilizes a torsionally preloaded, robust, kinematic mount capable of supporting manufacturing process loads while maintaining the position repeatability in five degrees of freedom required for the measurement and correction of optical figure. Results from a prototype system demonstrate absolute in-plane position uncertainty less than 200 nm and 50 nm, respectively, and axial position uncertainty is 40 nm absolute and 10 nm relative. The absolute and relative angular positioning uncertainties less than 1 µrad and 0.25 µrad respectively. The results exceed the requirements for many optical systems. The mount is also suitable for use in opto-mechanical assembly, so that the same platform can be used for manufacturing, metrology, final assembly, testing, and service.},
keywords = {CeFO, CeFO manufacturing, CEFO metrology, Freeform surfaces, Kinematic Coupling},
pubstate = {published},
tppubtype = {article}
}
High-performance freeform optical systems, designed for broad spectral imaging from the visible to the far infrared, place new demands on optical design, precision manufacturing, and precision metrology. To meet the tolerances on figure, roughness, and relative positioning in such systems requires the ability to perform metrology and manufacturing corrections on freeform optics in a continuous feedback loop. This feedback loop requires a common interface for machining and manufacturing platforms. This paper describes the design, analysis, and testing of such an interface suitable for use with single point diamond turning and deterministic micro-grinding. The interface utilizes a torsionally preloaded, robust, kinematic mount capable of supporting manufacturing process loads while maintaining the position repeatability in five degrees of freedom required for the measurement and correction of optical figure. Results from a prototype system demonstrate absolute in-plane position uncertainty less than 200 nm and 50 nm, respectively, and axial position uncertainty is 40 nm absolute and 10 nm relative. The absolute and relative angular positioning uncertainties less than 1 µrad and 0.25 µrad respectively. The results exceed the requirements for many optical systems. The mount is also suitable for use in opto-mechanical assembly, so that the same platform can be used for manufacturing, metrology, final assembly, testing, and service.
Aaron Bauer Nick Takaki,; Rolland, Jannick P.
On-the-fly surface manufacturability constraints for freeform optical design enabled by orthogonal polynomials Journal Article
In: Optics Express, vol. 27, no. 5, pp. 6129-6146, 2019.
Abstract | Links | BibTeX | Tags: Aberration correction, CeFO, Freeform surfaces, Image quality, Optical design, Optical surfaces, Optical systems
@article{Takaki_manufacturability,
title = {On-the-fly surface manufacturability constraints for freeform optical design enabled by orthogonal polynomials},
author = {Nick Takaki, Aaron Bauer, and Jannick P. Rolland},
editor = {James Leger, Ulrike Fuchs },
url = {https://doi.org/10.1364/OE.27.006129},
doi = {10.1364/OE.27.006129},
year = {2019},
date = {2019-02-20},
journal = {Optics Express},
volume = {27},
number = {5},
pages = {6129-6146},
abstract = {When leveraging orthogonal polynomials for describing freeform optics, designers typically focus on the computational efficiency of convergence and the optical performance of the resulting designs. However, to physically realize these designs, the freeform surfaces need to be fabricated and tested. An optimization constraint is described that allows on-the-fly calculation and constraint of manufacturability estimates for freeform surfaces, namely peak-to-valley sag departure and maximum gradient normal departure. This constraint’s construction is demonstrated in general for orthogonal polynomials, and in particular for both Zernike polynomials and Forbes 2D-Q polynomials. Lastly, this optimization constraint’s impact during design is shown via two design studies: a redesign of a published unobscured three-mirror telescope in the ball geometry for use in LWIR imaging and a freeform prism combiner for use in AR/VR applications. It is shown that using the optimization penalty with a fixed number of coefficients enables an improvement in manufacturability in exchange for a tradeoff in optical performance. It is further shown that, when the number of coefficients is increased in conjunction with the optimization penalty, manufacturability estimates can be improved without sacrificing optical performance.},
keywords = {Aberration correction, CeFO, Freeform surfaces, Image quality, Optical design, Optical surfaces, Optical systems},
pubstate = {published},
tppubtype = {article}
}
When leveraging orthogonal polynomials for describing freeform optics, designers typically focus on the computational efficiency of convergence and the optical performance of the resulting designs. However, to physically realize these designs, the freeform surfaces need to be fabricated and tested. An optimization constraint is described that allows on-the-fly calculation and constraint of manufacturability estimates for freeform surfaces, namely peak-to-valley sag departure and maximum gradient normal departure. This constraint’s construction is demonstrated in general for orthogonal polynomials, and in particular for both Zernike polynomials and Forbes 2D-Q polynomials. Lastly, this optimization constraint’s impact during design is shown via two design studies: a redesign of a published unobscured three-mirror telescope in the ball geometry for use in LWIR imaging and a freeform prism combiner for use in AR/VR applications. It is shown that using the optimization penalty with a fixed number of coefficients enables an improvement in manufacturability in exchange for a tradeoff in optical performance. It is further shown that, when the number of coefficients is increased in conjunction with the optimization penalty, manufacturability estimates can be improved without sacrificing optical performance.