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

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.

Image Distortion, between Unwanted Geometric Aberration and the Tool Used to Improve Observation Equipment Performance

2014 ◽  
Vol 555 ◽  
pp. 751-758 ◽  
Author(s):  
Nicolae Guzulescu ◽  
Cornel Todirică ◽  
Daniel Lăpădat
Keyword(s):  
Optical System ◽  
Measurement Errors ◽  
Optical Measurement ◽  
Image Distortion ◽  
Field Of View ◽  
Optical Systems ◽  
Object Appearance ◽  
And Control ◽  
Measurement And Control ◽  
Equipment Performance

An distortion aberration free optical system forms an orthoscopic image mean that is similar to original object, undeformed. Naturally imply that most optical systems are designed so that the image distortion is minimal, not to cause inconvenience to the user about either the object appearance – when it comes to a camera or camcorder, or the deformities that may cause measurement errors – when it comes to optical measurement and control equipment. However there are situations when distortion is desired to improve some performances of the observation optical system. In this article we present how distortion is used to increase the field of view, and also how distortion is used to optimize the field of view – resolution compromise.

scholarly journals Bed topography and lubrication inferred from surface measurements on fast-flowing ice streams

2003 ◽  
Vol 49 (167) ◽  
pp. 481-490 ◽  
Author(s):  
Throstur Thorsteinsson ◽  
Charles F. Raymond ◽  
G. Hilmar Gudmundsson ◽  
Robert A. Bindschadler ◽  
Paul Vornberger ◽  
...  
Keyword(s):  
Measurement Errors ◽  
Synthetic Data ◽  
Ice Thickness ◽  
West Antarctica ◽  
Horizontal Scale ◽  
Ice Streams ◽  
Bed Topography ◽  
Ice Stream ◽  
Flow Disturbances ◽  
Surface Measurements

AbstractObservations of surface elevation (s) and horizontal velocity components (u and v) are inverted to infer the topography (b) and lubrication (c) at the bed of an ice stream, based on a linearized perturbation theory of the transmission of flow disturbances through the ice thickness. Synthetic data are used to illustrate non-uniqueness in the inversion, but also demonstrate that effects of b and c can be separated when s, u and v are specified, even with added noise to simulate measurement errors. We have analyzed prominent short-horizontal-scale (∼2 km) features in topography and velocity pattern in a local 64 km by 32 km area of the surface of Ice Stream E,West Antarctica. Our preferred interpretation of bed conditions beneath the most prominent features on the surface identifies a deep trough in the basal topography with low lubrication in the base of the trough.

Research on the Online Test Principle and Error Analysis of Aspherical Optical Surfaces

2013 ◽  
Vol 552 ◽  
pp. 434-439
Author(s):  
Da Mu ◽  
Quan Yong Li ◽  
Bo Qi Wu ◽  
Yu Nan Du
Keyword(s):  
High Precision ◽  
Precision Measurement ◽  
Measurement Errors ◽  
Surface Shape ◽  
High Precision Measurement ◽  
Aspherical Surface ◽  
Optical Surfaces ◽  
Advantages And Disadvantages ◽  
Swing Arm ◽  
Key Factor

For tFor t For tFor the imaging advantages of aspheric optical component, it has been widely used in the aviation, aerospace, defense and civilian high-technology. Aspherical surface shape test is a key factor restricted aspheric processing and a complex sophisticated testing techniques. The well known measurement methods are faulty. Each method has advantages and disadvantages; many methods cannot be used for online testing. In this paper，the geometric principle of a swing-arm profilometer as a novel method to measure aspherics is introduced．The deviation between the actual and the ideal of aspherical surface shape is confirmed by the high-precision measurement for the vertical height with a specific path on the aspherical optical surfaces. By adjusting the location of measuring devices to maintain the distance of rotation center to the center of workpiece equal to the length of swing-arm,we can achieve the measurement for the workpiece of different machining tool. The measurement system mainly consists of the lifting and landing system of the high-precision axis,the high-precision level turntable rotary table, the high rigidity measuring arm and the high precision measurement sensors. And the follow-up data processing puts forward a number of error correction models at the same time. The advantages of the measurement method are that the measurement sports is only a simple turning motion .It will be helpful to reduce measurement errors and improve the efficiency of measurement.

Development of Silicon Carbide Substrates for Aerospace Applications

2012 ◽  
Vol 1373 ◽  
Author(s):  
Antonio J. Abdalla ◽  
Álvaro J. Damião ◽  
Elson Campos ◽  
Jerusa G.A. Santana ◽  
Marcelo C. Vicentini ◽  
...  
Keyword(s):  
Organic Material ◽  
Mechanical Tests ◽  
Argon Atmosphere ◽  
Optical Systems ◽  
High Tech ◽  
Laser Confocal Microscopy ◽  
Optical Surfaces ◽  
Aerospace Applications ◽  
Sintering Additive ◽  
National Boundaries

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.

scholarly journals Multifunctional contamination-resistant coatings

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.

scholarly journals Computer Generated Holograms (CGH) for Testing, Alignment and Positioning of Astronomical and Space Mirrors Aspherical Surfaces

2019 ◽  
Vol 215 ◽  
pp. 09002
Author(s):  
Aleksandr Semenov ◽  
Magomed Abdulkadyrov ◽  
Nikolay Dobrikov ◽  
Aleksandr Ignatov ◽  
Vladimir Patrikeev ◽  
...  
Keyword(s):  
High Accuracy ◽  
Optical Systems ◽  
Optical Components ◽  
Aspherical Surface ◽  
Geometrical Center ◽  
Surface Optical ◽  
Computer Generated Holograms

JSC LZOS successfully applies Computer Generated Holograms (CGH) for testing of on- and off-axis surfaces of large-dimensioned optical components for their alignment with respect to interferometer, for defining of aspherical surface optical vertex position with respect to the geometrical center and for optical systems alignment. All this allows producing of large-dimensioned aspherical on- and off-axis astronomical and space mirrors with high accuracy.

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

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.

The possibility of remote sounding of the earth’s resistivity profile

Geophysics ◽  
1983 ◽  
Vol 48 (5) ◽  
pp. 636-638 ◽  
Author(s):  
M. El‐Raey
Keyword(s):  
Continuous Function ◽  
Measurement Errors ◽  
Nonlinear Dependence ◽  
Iterative Technique ◽  
Resistivity Measurements ◽  
Advantages And Disadvantages ◽  
Resistivity Profile ◽  
Remote Sounding ◽  
Resistivity Model ◽  
Surface Measurements

A variety of methods have been developed to solve the general problem of determining underground resistivity from surface measurements using two current electrodes and two collinear potential electrodes (Ghosh, 1971; Parker, 1971; Inman et al, 1973; Inman, 1975; Koefoed, 1979). Nevertheless, problems associated with measurement errors, nonlinearities, and nonuniqueness have not been completely resolved. Recently, a method of interpretation of direct current resistivity measurements, using a linearized Backus and Gilbert technique was advanced by Oldenburg (1978). In this method, the resistivity is assumed to be a continuous function of depth, and an iterative technique is used to construct a resistivity model whose calculated responses agree with observations within a prescribed error. The nonuniqueness of the problem was resolved by determining only averages of resistivity at depth. However, even in this method the nonlinearity of the problem prohibits definitive statements about advantages and disadvantages of any particular electrode configuration until a large variety of resistivity structures have been considered. The main problems are (1) a nonlinear resistivity profile, (2) a nonlinear current penetration, (3) a nonlinear dependence of measurable potential on resistivity, and (4) a nonlinear depth investigation characteristic.

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

2019 ◽  
Vol 8 (3-4) ◽  
pp. 203-215 ◽  
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.

Simulation of segmented mirrors with adaptive optics

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.

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