Biologically inspired optical surfaces for miniaturized optical systems

ABSTRACTPayload and high-tech are important characteristics when the goals are aerospace applications. The development of the technologies associated to these applications has interests that transcend national boundaries and are of strategic importance to the nations. Ultra lightweight mirrors, supports and structures for optical systems are important part of this subject. This paper reports the development of SiC substrates, obtained by pressing, to be applied on embedded precision reflective optics. Different SiC granulometries, having YAG as sintering additive, were processed by: ball milling, drying and deagglomeration, sift, uniaxial and isostatic pressing, and, finally, argon atmosphere sintering at 1900°C. Different porosities were obtained according to the amount of organic material added. Into one side of the samples pellets of organic material were introduced to generate voids to reduce the weight of samples as a whole. The substrates were grinding and polished, looking for a SiC surface having low porosity, as porosity is directly related to light scattering that should be avoided on optical surfaces. Laser surface treatments were applied (using or not SiC barbotine) as a method to improve the surface quality. The samples were characterized by optical and laser confocal microscopy, roughness measurements and mechanical tests. The results are very promissory for future applications.

Download Full-text

Multifunctional contamination-resistant coatings

EPJ Web of Conferences ◽

10.1051/epjconf/201921502002 ◽

2019 ◽

Vol 215 ◽

pp. 02002

Author(s):

Nadja Felde ◽

Anne Gärtner ◽

Stefan Schwinde ◽

Sven Schröder

Keyword(s):

Thin Film ◽

Surface Roughness ◽

Light Scattering ◽

Structural Design ◽

Optical Quality ◽

Optical Systems ◽

Optical Losses ◽

High Optical Quality ◽

Optical Surfaces ◽

Laser Stability

Surface contaminations can critically affect the performance of optical surfaces, in particular with respect to light scattering, optical losses, and laser stability. Thus, avoiding contaminations and reducing contamination-induced effects is of particular interest in the manufacturing of optical systems. By combining a specific thin film design with a tailored structural design, contamination-resistant coatings with a high optical quality can be realized. Most important is the balance of self-cleaningand light scattering-relevant surface roughness components.

Download Full-text

The Manufacturing of a Multi-surface Monolithic Telescope with Freeform Surfaces

EPJ Web of Conferences ◽

10.1051/epjconf/201921506004 ◽

2019 ◽

Vol 215 ◽

pp. 06004

Author(s):

Todd Blalock ◽

Brian Myer ◽

Brittany Cox ◽

Jessica Nelson

Keyword(s):

Mechanical Stability ◽

Optical Systems ◽

Optical Performance ◽

Freeform Surfaces ◽

Optical Surfaces ◽

Spherical Surfaces

Monolithic multi-surface telescopes combined with freeform optical surfaces provide improvements in optical performance in a smaller footprint as compared to systems with spherical surfaces, while providing superior mechanical stability to traditional telescope assemblies. Three different monolithic telescope concepts, in different configurations and optical performance were produced as proof of concepts. The results of the telescopes are presented as well as the unique manufacturing and testing challenges to produce these monolithic optical systems.

Download Full-text

Biologically Inspired Optical Systems

Biomimetics ◽

10.1201/9781420037715.ch11 ◽

2005 ◽

pp. 291-308 ◽

Cited By ~ 1

Author(s):

Luke Lee ◽

Robert Szema

Keyword(s):

Optical Systems ◽

Biologically Inspired

Download Full-text

Development of a metrology technique suitable for in situ measurement and corrective manufacturing of freeform optics

Advanced Optical Technologies ◽

10.1515/aot-2018-0072 ◽

2019 ◽

Vol 8 (3-4) ◽

pp. 203-215 ◽

Cited By ~ 4

Author(s):

Dali Ramu Burada ◽

Kamal K. Pant ◽

Vinod Mishra ◽

Mohamed Bichra ◽

Gufran Sayeed Khan ◽

...

Keyword(s):

Degrees Of Freedom ◽

Tool Path ◽

Optical Systems ◽

Optical Fabrication ◽

Optical Surfaces ◽

Rotationally Symmetric ◽

Freeform Optics ◽

Slow Tool Servo ◽

Metrology System

Abstract The applications of freeform optical surfaces in modern optical systems are providing unique solutions over rotationally symmetric surfaces. These surfaces offer higher degrees of freedom to the designer to enhance the high-end performance of the optical system. The precise metrology of freeform optics is one of the major bottlenecks for its use in imaging applications. Modern optical fabrication methods (i.e. fast or slow tool servo configuration) are, in principle, capable to meet the challenges to generate complex freeform surfaces if supported by precise metrology feedback for error compensation. In the present work, we have developed a Shack-Hartmann sensor-based metrology technique that can be used for quantitative in situ measurement of freeform optics. The sensor head is used to measure freeform optics in the reflection mode by following the CNC tool path in the offline mode. The measurements are used as feedback for corrective machining. Quantitative analysis is also performed to estimate the error budget of the metrology system. Further, the proposed in situ metrology scheme is validated by measuring freeform surface using a coherence correlation interferometric optical profiler.

Download Full-text

Simulation of segmented mirrors with adaptive optics

Advanced Optical Technologies ◽

10.1515/aot-2018-0063 ◽

2019 ◽

Vol 8 (2) ◽

pp. 119-127

Author(s):

Johannes Störkle ◽

Luzia Hahn ◽

Peter Eberhard

Keyword(s):

Adaptive Optics ◽

Optical Systems ◽

Optical Aberrations ◽

Optical Surfaces ◽

Atmospheric Disturbances ◽

Simulation Based ◽

Segmented Mirror ◽

Multidisciplinary Simulation ◽

And Control ◽

Optical Unit

Abstract This work deals with the simulation-based investigation and control of optical systems that are mechanically influenced. Here, the focus is on the dynamic-optical modeling of vibration-sensitive, segmented mirror systems, which are used, for example, in large astronomic telescopes. Furthermore, an adaptive optical unit usually compensates for the optical aberrations due to atmospheric disturbances. In practice, these aberrations are detected and corrected within a few seconds using deformable mirrors. However, to further improve the performance of these optical systems, dynamic disturbances in the mechanics, i.e. small movements and deformations of the optical surfaces, must also be taken into account. For the investigation of such cases, multidisciplinary simulation methods are developed and presented.

Download Full-text

An assessment of approximating aspheres with more easily manufactured surfaces

Journal of Synchrotron Radiation ◽

10.1107/s0909049597018633 ◽

1998 ◽

Vol 5 (3) ◽

pp. 814-816 ◽

Cited By ~ 1

Author(s):

Malcolm R. Howells ◽

Joel Anspach ◽

John Bender

Keyword(s):

Surface Roughness ◽

Synchrotron Radiation ◽

System Performance ◽

Three Dimensional ◽

Lower Surface ◽

Optical Systems ◽

Conic Sections ◽

Optical Surfaces ◽

Elliptical Cylinders ◽

Surface Figure

In designing optical systems for synchrotron radiation, one is often led to conclude that optimal performance can be obtained from optical surfaces described by conic sections of revolution, usually paraboloids and ellipsoids. The resulting design can lead to prescriptions for three-dimensional optical surfaces that are difficult to fabricate accurately. Under some circumstances satisfactory system performance can be achieved through the use of more easily manufactured surfaces such as cylinders, cones, bent cones, toroids and elliptical cylinders. These surfaces often have the additional benefits of scalability to large aperture, lower surface roughness and improved surface figure accuracy. In this paper we explore some of the conditions under which these more easily manufactured surfaces can be utilized without sacrificing performance.

Download Full-text

Biologically Inspired Optical Systems

Biomimetics ◽

10.1201/9780849331633.ch11 ◽

2005 ◽

pp. 291-308 ◽

Cited By ~ 1

Author(s):

Luke Lee ◽

Robert Szema

Keyword(s):

Optical Systems ◽

Biologically Inspired

Download Full-text

Imperfections of Scalar Approximation in Calibration of Computer-Generated Holograms for Optical Surface Measurements

Applied Sciences ◽

10.3390/app11156897 ◽

2021 ◽

Vol 11 (15) ◽

pp. 6897

Author(s):

Yingying Bai ◽

Zhiyu Zhang ◽

Ruoqiu Wang ◽

Tianbao Chen ◽

Xu Wang ◽

...

Keyword(s):

Measurement Errors ◽

Grating Period ◽

Optical Systems ◽

Practical Significance ◽

Etching Depth ◽

Rigorous Evaluation ◽

Optical Surfaces ◽

Scalar Approximation ◽

Surface Measurements ◽

Computer Generated Holograms

Computer-generated hologram (CGH) null correctors are used as accuracy standards for interferometric measurements of optical surfaces and optical systems. Diffractive optics calibrators (DOCs) have been developed to evaluate the phase tolerance of CGHs based on scalar approximation by measuring variations in duty cycle and etching depth. However, if the grating period of a CGH < 5 λ, the scalar approximation is not accurate for phase analysis and reconstruction. In this study, the measurement errors of DOCs with small-period CGHs were investigated and experimentally verified. Results show that the imperfections of scalar approximation in CGHs cannot be ignored and the development of rigorous evaluation methods to improve the measurement accuracy of CGHs is of great practical significance.

Download Full-text

Atomic Resolution in Crystal Aperture Stem

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100179932 ◽

1990 ◽

Vol 48 (1) ◽

pp. 236-237

Author(s):

J T Fourie

Keyword(s):

Optical System ◽

Spherical Aberration ◽

Three Dimensional ◽

Transmission Function ◽

Optical Systems ◽

Bragg Angle ◽

Electron Optical System ◽

Intimate Contact ◽

Diffraction Effects ◽

Design Aspect

The attempts at improvement of electron optical systems to date, have largely been directed towards the design aspect of magnetic lenses and towards the establishment of ideal lens combinations. In the present work the emphasis has been placed on the utilization of a unique three-dimensional crystal objective aperture within a standard electron optical system with the aim to reduce the spherical aberration without introducing diffraction effects. A brief summary of this work together with a description of results obtained recently, will be given.The concept of utilizing a crystal as aperture in an electron optical system was introduced by Fourie who employed a {111} crystal foil as a collector aperture, by mounting the sample directly on top of the foil and in intimate contact with the foil. In the present work the sample was mounted on the bottom of the foil so that the crystal would function as an objective or probe forming aperture. The transmission function of such a crystal aperture depends on the thickness, t, and the orientation of the foil. The expression for calculating the transmission function was derived by Hashimoto, Howie and Whelan on the basis of the electron equivalent of the Borrmann anomalous absorption effect in crystals. In Fig. 1 the functions for a g220 diffraction vector and t = 0.53 and 1.0 μm are shown. Here n= Θ‒ΘB, where Θ is the angle between the incident ray and the (hkl) planes, and ΘB is the Bragg angle.

Download Full-text