Mustafa Ekinci - Academia.edu (original) (raw)
Papers by Mustafa Ekinci
Applied Optics, 2020
We present the realization of a high-precision, 0.5 m aperture size Cassegrain collimator system.... more We present the realization of a high-precision, 0.5 m aperture size Cassegrain collimator system. The optical design, the optomechanical design, the mirror manufacturing, and the telescope alignment with a performance evaluation are extensively discussed. The optical design of the collimator is based on the Cassegrain telescope design with two aspheric mirrors. An athermalized, high stability optomechanical structure is conceived for the collimator to meet stringent performance requirements. The high-quality mirrors are made of low-expansion Zerodur glass–ceramic and the primary mirror is light-weighted to 63% of its initial weight. The design of a dedicated five-axis flexure mechanism driven by nanopositioner stages to compensate the secondary mirror misalignments is given. Primary and secondary mirrors with aspheric surfaces are manufactured, and their forms are measured by computer-generated holograms with a phase-shifting Fizeau interferometer. The alignment strategy is based on...
International Optical Design Conference 2021, 2021
In this study, we present a simulation and experimental investigation of binodal astigmatism in N... more In this study, we present a simulation and experimental investigation of binodal astigmatism in NAT with a Cassegrain telescope. The high-precision telescope system utilizes a piezo-actuated flexural mechanism to introduce secondary mirror misalignments and generate aberrations intentionally. The induced aberrations are measured interferometrically and quantified for a grid of field points on the image plane of the telescope. For this purpose, a coma-free pivot point of the secondary mirror was simulated for isolating the binodal astigmatism field response. A simulation of binodal astigmatism was generated using a real ray trace model of the Cassegrain system and analyzed to compare to the experimental results. The experimental results were consistent with the simulations, hence experimentally validating NAT for binodal astigmatism for the first time.
SPIE Proceedings, 2012
The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation instrument planned ... more The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation instrument planned for the Very Large Telescope (VLT) and the Adaptive Optics Facility (AOF) 1. It is an AO assisted instrument that will make use of the Deformable Secondary Mirror and the new Laser Guide Star Facility (4LGSF), and it is designed for the Cassegrain focus of the telescope UT4. The project just concluded its conceptual design phase and is awaiting formal approval to continue to the next phase. ERIS will offer 1-5 m imaging and 1-2.5 m integral field spectroscopic capabilities with high Strehl performance. As such it will replace, with much improved single conjugated AO correction, the most scientifically important and popular observing capabilities currently offered by NACO 2 (diffraction limited imaging in J-M band, Sparse Aperture Masking and APP coronagraphy) and by SINFONI 3 , whose instrumental module, SPIFFI, will be re-used in ERIS. The Cassegrain location and the performance requirements impose challenging demands on the project, from opto-mechanical design to cryogenics to the operational concept. In this paper we describe the baseline design proposed for ERIS and discuss these technical challenges, with particular emphasis on the trade-offs and the novel solutions proposed for building ERIS.
Cumhuriyet Science Journal, 2018
Optics express, 2021
We present simulations and an experimental investigation of binodal astigmatism in nodal aberrati... more We present simulations and an experimental investigation of binodal astigmatism in nodal aberration theory (NAT) for a customized, high-precision Cassegrain telescope system. The telescope system utilizes a five-axis, piezo-actuated flexural mechanism to introduce secondary mirror misalignments and generate aberrations intentionally. The induced aberrations are measured interferometrically and quantified for a grid of field points on the telescope system's image plane. For this purpose, a coma-free pivot point of the secondary mirror was simulated for isolating the binodal astigmatism field response. The separation of the nodes is proportional to the introduced misalignments. A simulation of Fringe Zernike coma and binodal astigmatism was generated using a real ray trace model of the optical system and analyzed to compare to the experimental results. A statistical analysis of the measurements was performed to show the experimental results' accuracy and stability. The experim...
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II, 2016
Applied Optics, 2016
We describe the design of a thermal refocusing method for spaceborne high-resolution imagers wher... more We describe the design of a thermal refocusing method for spaceborne high-resolution imagers where Korsch optical design is usually implemented. The secondary mirror is made of aluminum, a high thermal expansion coefficient material, instead of conventional zero-expansion glass ceramics. In this way, the radius of the curvature can be controlled by means of temperature change of the mirror. Change in the radius of curvature also changes the effective focal length of the camera which is used for compensation of the defocus that occurred in space. We show that the 30 μm despace of the secondary mirror in the optical system can be compensated by an ∼10°C temperature change of the mirror while the image quality is maintained.
2015 7th International Conference on Recent Advances in Space Technologies (RAST), 2015
ABSTRACT
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II
Applied Optics, 2020
We present the realization of a high-precision, 0.5 m aperture size Cassegrain collimator system.... more We present the realization of a high-precision, 0.5 m aperture size Cassegrain collimator system. The optical design, the optomechanical design, the mirror manufacturing, and the telescope alignment with a performance evaluation are extensively discussed. The optical design of the collimator is based on the Cassegrain telescope design with two aspheric mirrors. An athermalized, high stability optomechanical structure is conceived for the collimator to meet stringent performance requirements. The high-quality mirrors are made of low-expansion Zerodur glass–ceramic and the primary mirror is light-weighted to 63% of its initial weight. The design of a dedicated five-axis flexure mechanism driven by nanopositioner stages to compensate the secondary mirror misalignments is given. Primary and secondary mirrors with aspheric surfaces are manufactured, and their forms are measured by computer-generated holograms with a phase-shifting Fizeau interferometer. The alignment strategy is based on...
International Optical Design Conference 2021, 2021
In this study, we present a simulation and experimental investigation of binodal astigmatism in N... more In this study, we present a simulation and experimental investigation of binodal astigmatism in NAT with a Cassegrain telescope. The high-precision telescope system utilizes a piezo-actuated flexural mechanism to introduce secondary mirror misalignments and generate aberrations intentionally. The induced aberrations are measured interferometrically and quantified for a grid of field points on the image plane of the telescope. For this purpose, a coma-free pivot point of the secondary mirror was simulated for isolating the binodal astigmatism field response. A simulation of binodal astigmatism was generated using a real ray trace model of the Cassegrain system and analyzed to compare to the experimental results. The experimental results were consistent with the simulations, hence experimentally validating NAT for binodal astigmatism for the first time.
SPIE Proceedings, 2012
The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation instrument planned ... more The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation instrument planned for the Very Large Telescope (VLT) and the Adaptive Optics Facility (AOF) 1. It is an AO assisted instrument that will make use of the Deformable Secondary Mirror and the new Laser Guide Star Facility (4LGSF), and it is designed for the Cassegrain focus of the telescope UT4. The project just concluded its conceptual design phase and is awaiting formal approval to continue to the next phase. ERIS will offer 1-5 m imaging and 1-2.5 m integral field spectroscopic capabilities with high Strehl performance. As such it will replace, with much improved single conjugated AO correction, the most scientifically important and popular observing capabilities currently offered by NACO 2 (diffraction limited imaging in J-M band, Sparse Aperture Masking and APP coronagraphy) and by SINFONI 3 , whose instrumental module, SPIFFI, will be re-used in ERIS. The Cassegrain location and the performance requirements impose challenging demands on the project, from opto-mechanical design to cryogenics to the operational concept. In this paper we describe the baseline design proposed for ERIS and discuss these technical challenges, with particular emphasis on the trade-offs and the novel solutions proposed for building ERIS.
Cumhuriyet Science Journal, 2018
Optics express, 2021
We present simulations and an experimental investigation of binodal astigmatism in nodal aberrati... more We present simulations and an experimental investigation of binodal astigmatism in nodal aberration theory (NAT) for a customized, high-precision Cassegrain telescope system. The telescope system utilizes a five-axis, piezo-actuated flexural mechanism to introduce secondary mirror misalignments and generate aberrations intentionally. The induced aberrations are measured interferometrically and quantified for a grid of field points on the telescope system's image plane. For this purpose, a coma-free pivot point of the secondary mirror was simulated for isolating the binodal astigmatism field response. The separation of the nodes is proportional to the introduced misalignments. A simulation of Fringe Zernike coma and binodal astigmatism was generated using a real ray trace model of the optical system and analyzed to compare to the experimental results. A statistical analysis of the measurements was performed to show the experimental results' accuracy and stability. The experim...
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II, 2016
Applied Optics, 2016
We describe the design of a thermal refocusing method for spaceborne high-resolution imagers wher... more We describe the design of a thermal refocusing method for spaceborne high-resolution imagers where Korsch optical design is usually implemented. The secondary mirror is made of aluminum, a high thermal expansion coefficient material, instead of conventional zero-expansion glass ceramics. In this way, the radius of the curvature can be controlled by means of temperature change of the mirror. Change in the radius of curvature also changes the effective focal length of the camera which is used for compensation of the defocus that occurred in space. We show that the 30 μm despace of the secondary mirror in the optical system can be compensated by an ∼10°C temperature change of the mirror while the image quality is maintained.
2015 7th International Conference on Recent Advances in Space Technologies (RAST), 2015
ABSTRACT
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II