Proceedings Volume 12215

Optical Modeling and Performance Predictions XII

Mark A. Kahan
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Proceedings Volume 12215

Optical Modeling and Performance Predictions XII

Mark A. Kahan
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Volume Details

Date Published: 3 October 2022
Contents: 7 Sessions, 17 Papers, 13 Presentations
Conference: SPIE Optical Engineering + Applications 2022
Volume Number: 12215

Table of Contents

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Table of Contents

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  • Front Matter: Volume 12215
  • Testing, Piece-Part Characterizations, and Digital Camera System Simulations
  • STOP
  • BRDF, Polarization, and Diffraction Theory
  • Gratings and Metamaterials
  • Sensors and Communication
  • Poster Session
Front Matter: Volume 12215
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Front Matter: Volume 12215
This PDF file contains the front matter associated with SPIE Proceedings Volume 12215 including the Title Page, Copyright information, and Table of Contents.
Testing, Piece-Part Characterizations, and Digital Camera System Simulations
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Impact of higher order surface irregularity on system-level wavefront variation across the field
Charlie Granger, Kaia Williams, Matthew Brophy, et al.
The influence of surface irregularity on optical system wavefront performance is well established, but typically irregularity analysis and specifications are limited to peak-to-valley or 3rd-order Seidel terms. As optical assembly wavefront specifications become tighter, higher order irregularity may need to be considered, particularly for surfaces away from the system pupil. This work presents a case study of an optical system with tightly controlled wavefront Zernike terms across the field. Using as-built diagnostic testing and optical modeling incorporating Fringe Zernike surface irregularity, higher order rotationally symmetric irregularities are determined to be the root-cause of specific wavefront Zernike failure modes. Sensitivity and tolerancing analysis are used to determine the required surface specification and provide feedback to the fabrication process, improving system first-pass yield.
Axially symmetric retarder with radial retardance modulation
M. Jaqueline Pérez-Mota, Oscar G. Rodríguez-Herrera
We present the design of an axially symmetric retarder capable of converting a homogeneously polarized incident beam into a beam with a heterogeneous polarization state via radial retardance modulation. The retarder is a quasi-achromatic, passive optical element, designed to be made out of an isotropic material, which may be used to generate cylindrical vector beams with heterogeneous polarization states varying in the radial and azimuthal directions. The design of the retarder takes into account geometrical and physical optics considerations, which allowed us to develop a computer model that we used to assess its performance. We will present an analysis of the expected performance of the retarder and discuss its capabilities, limitations, and potential applications in polarimetry.
Simulated formation of UV-cured polymer lenses on aqueous substrates
Robert Thompson, Simon Hempel-Costello, Zack Johnson, et al.
We simulate the formation of macroscopic polymer lenses made by depositing a hydrophobic liquid polymer on an aqueous substrate, and explore how changing the hydrophobicity of the polymer affects lens shape. Methods for the fabrication of polymer lenses and the measurement of interfacial tensions between polymer, substrate and air are described. Characteristics of simulated and fabricated lens shapes are compared. Finally we indicate possible obstacles to the use of simulations for predicting properties of polymer lenses made with this technique.
Generating physics-based synthetic data for infrared/electro-optical system analysis and design
Özgür Murat Polat, Yücel Cengiz Özer
For design, testing and optimization of infrared systems, generation of big physics based synthetic data is very important, since it is impossible to collect data with experiments only. In order to create such a big radiometric data, an end-to-end synthetic simulation approach is so useful. For generating radiometric data in imaging chain from object space to the system detector output considering environmental and system effects; the parameter space in rendering pipeline can be scanned throughout imaging chain. Therefore, target, environment, electro-optical/infrared system parameter space and related radiometric data outputs of the sensor construct the big physics based data all together. Also, relative motion between the observed object and the observer is another source of physical data. In this paper, the main components and parameter space of the radiometric data are described and some example complex background scene outputs which are generated with 3D rendering are demonstrated. In addition, results of a laboratory (experimental) validation effort are discussed, which show the validity of the mathematical approach applied in generation of the radiometric data. These laboratory experiments show that when the inputs are correctly defined, the data can be generated very close to real measurements, i.e. physical reality can be synthetically generated at acceptable levels of error.
Digital camera simulations of thin filaments in non-premixed laminar methane-air coflow flames
In this work, the temperature field of a methane-air non-premixed coflow flame obtained via numerical simulation is used to induce radiance emission from the surface of a thin filament directly exposed to the flame. The radiance signal is subsequently processed through a digital camera simulation to generate synthetic radiance photographic images. Results from the theoretical analysis are validated against images captured from a corresponding experiment, where the light emitted by a thin filament in contact with a non-premixed coflow system is obtained using an automated imaging system at selected heights along the axis of the flame.
STOP
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Subspace identification of low-dimensional Structural-Thermal-Optical-Performance (STOP) models of reflective optics
In this paper, we investigate the feasibility of using subspace system identification techniques for estimating transient Structural-Thermal-Optical Performance (STOP) models of reflective optics. As a test case, we use a Newtonian telescope structure. This work is motivated by the need for the development of model-based datadriven techniques for prediction, estimation, and control of thermal effects and thermally-induced wavefront aberrations in optical systems, such as ground and space telescopes, optical instruments operating in harsh environments, optical lithography machines, and optical components of high-power laser systems. We estimate and validate a state-space model of a transient STOP dynamics. First, we model the system in COMSOL Multiphysics. Then, we use LiveLink for MATLAB software module to export the wavefront aberrations data from COMSOL to MATLAB. This data is used to test the subspace identification method that is implemented in Python. One of the main challenges in modeling and estimation of STOP models is that they are inherently large-dimensional. The large-scale nature of STOP models originates from the coupling of optical, thermal, and structural phenomena and physical processes. Our results show that large-dimensional STOP dynamics of the considered optical system can be accurately estimated by low-dimensional state-space models. Due to their lowdimensional nature and state-space forms, these models can effectively be used for the prediction, estimation, and control of thermally-induced wavefront aberrations. The developed MATLAB, COMSOL, and Python codes are available online.
Transient simulation of high-power dynamical-thermoelastic-optical systems
Luzia Hahn, Peter Eberhard
The system performance of high-precision optical systems is highly sensitive to transient mechanical and thermal disturbances. In order to precisely predict a systems operating performance these disturbances need to be modeled, simulated, and analyzed. In this work, a numerical method is presented which allows for the consideration of transient mechanical rigid body motions, mechanical and thermal elastic deformations, and thermally induced refraction index changes in the transient simulation of optical systems operated with lasers.
Tailoring the stiffness of large mirrors to reduce specific optical aberrations
Christopher L. Hopkins
Presented is a method that tailors the geometry of a mirror’s core structure as well as the mounting interface such that a desired set of aberrations is reduced. It will be shown that targeting specific aberrations as opposed to reducing overall surface figure error (SFE) is a valid method to reduce weight or improve performance. Analyzed first is the self-weight deflection of a thin circular plate of uniform thickness continuously supported along its outer edge. The Kirchhoff-Love plate bending equations are related to the radially symmetric Zernike polynomials of piston, defocus, and primary spherical aberration. Next, the mirror’s radial thickness is optimized to eliminate primary and secondary spherical aberrations when the outer edge is simply supported. As an example, the method is demonstrated using a 2-meter diameter aluminum mirror where surface deflections can have an appreciable effect at mid-to-near infrared wavelengths.
BRDF, Polarization, and Diffraction Theory
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Evaluation of microfacet BRDF solar cell model modification using experimental data
Madilynn E. Compean, Todd V. Small
The bidirectional reflectance distribution function (BRDF) describes a material’s property of reflectance by relating incident irradiance to scattered radiance. Microfacet models are a popular class of BRDF, which assumes geometric optics often trading accuracy for computing speed in both scene generation and computer graphics. Another popular class of BRDF is physical optics models that account for wave optics effects; the main drawbacks are complexity and computing power. If a wave optics effect from a material with a known solution can be combined with a microfacet model, perhaps computing speed can be retained while improving accuracy of the model. Based on previous work extending to include out-of-plane measurements and combining a microfacet model with a clear diffraction effect off a solar panel, validation of the model will be conducted using alternative laser sources and solar cell samples. This will be compared to a wave optics model for the novel diffractive feature and physical data to determine validity.
Determining solar cell BRDF model parameters by fitting to high-resolution out-of-plane measurement data
Michael R. Gross, Todd V. Small, Michael A. Marciniak, et al.
For remote sensing purposes the ability to accurately model the light reflecting off of a solar panel is of great interest to the Department of Defense (DoD). The bidirectional reflectance distribution function (BRDF) describes material reflectance by describing how incident irradiance reflects into all possible scatter angles as a function of incident angle. Many such models of BRDF exist each consisting of their own advantages and tradeoffs when describing different kinds of materials. However, a solar panel has unique features that are not featured in any of these previously known models. A previous project at the Air Force Institute of Technology (AFIT)1 created a novel microfacet-like BRDF to model a solar panel with a prominent diffractive feature present which had not been previously modeled. This BRDF was coded into MATLAB and C++ for the purpose of trying to fit measured solar cell BRDF data to the model. This was accomplished by using the lsqcurvefit function in MATLAB which attempts to fit the model parameters, some of which are material parameters, to attempt to match the BRDF to plotted data. Current results have poor accuracy due to the presence of several parameters in each of the four terms in the novel BRDF function. As such further changes to code are needed to improve the fitting accuracy of the lsqcurvefit function.
Simulation of the polarimetric response of a microscopic semitransparent specimen with inner structure
Carlos E. Castañeda-Cuevas, Oscar G. Rodríguez-Herrera
The anomalous diffraction approximation (ADA) is a convenient tool to model scattering by weakly scattering objects with large size parameters. The simplicity of the ADA makes it suitable to model objects with different geometries. However, this approximation is a scalar theory and does not consider polarization effects, which might be relevant in some scattering problems. We propose a modified version of the ADA that includes polarization effects and use it to simulate the polarimetric response of a microscopic, semitransparent object with complex inner structure. Our simulation is used to assess the performance of a polarimetric microscope under development in our group and determine the suitability of polarimetry for the observation of the inner structure of semitransparent microscopic complex objects made out of isotropic media with no intrinsic birefringence.
Experiments supporting the momentum exchange theory description for photon diffraction
Mobley (2018) presented Momentum Exchange Theory (MET) as an alternative picture for photon diffraction, providing comparable predictions to Classical Optical Wave and Boundary Diffraction Wave Theories. MET explains diffraction scattering in terms of momentum transfer probabilities determined by two primary factors: 1) the momentum transfer states of the scattering lattice (aperture); and 2) the distance and location of momentum transfer between the lattice and the scattered photon path. For example, MET was illustrated examining straight edge diffraction where the Fresnel pattern is obtained assuming local maxima in the probability of perpendicular momentum exchange approximated by Δp = ±(2j+1)h/4x, where x is the distance between the photon’s path and the edge, (j = 0, 1, 2, 3…). This study explores diffraction experiments that might discriminate between the predictions of MET and alternative wave theories. This reports preliminary results with novel observations supporting descriptions based upon MET. Experiments examine diffraction of a narrow laser beam by thin aluminum ribbons with a variety of configurations: e.g. diffraction by the edge of an Al ribbon and single-slit diffraction between Al ribbons. Additional fringes are observed in diffraction patterns with a dependence related to Δp = ±(2j+1)h/2L where L is the width of the Al ribbon. Photon scattering exhibits similarities in dependence to multiple-slit diffraction but where the photons only pass through a single slit. Observations suggest the photon scattering probabilities are dependent on the electromagnetic field geometry that determines momentum exchange at the aperture as predicted by MET.
Gratings and Metamaterials
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Spectral emissivity prediction in multi-resonator metamaterials
The ability to design multi-resonant thermal emitters is essential to the advancement of a wide variety of applications, including thermal management and sensing. These fields would greatly benefit from the development of efficient tools for predicting the spectral response of coupled, multi-resonator systems. In this work, we propose a semi-analytical prediction tool based on coupled-mode theory. We demonstrate the accuracy of our method by predicting and optimizing spectral response in a coupled, multi-resonator system based on hBN ribbons. Our approach greatly reduces the computational overhead associated with spectral design tasks in multi-resonator systems in addition to providing valuable physical insights.
Sensors and Communication
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Polymer ring-resonator on a slotted membrane for ultrasound imaging
T. Sahraeibelverdi, H. Veladi, A. Shirazi, et al.
Ring resonators have been vastly considered to address the demand for future needs of smaller miniature array to reach compact and more sensitive ultrasound detectors. In this work we proposed a novel mechanically induced high sensitivity for a ring on an slotted membrane with relatively low-cost polymer material, roll to roll manufacturing ability, and less temperature-sensitivity. The results showing a 50 % sensitivity increase on the most sensitive device structure on simple membrane which has been reported. We also proposed its fabrication method by two-step nano-imprint lithography followed by AFM tip to make the slots on the membrane. This device could add benefits of early diseases detection in ultrasound biomedical imaging. Also, in a combination of an array with other ring resonators can cover larger dynamic range and frequency bandwidth.
Multimodal-capable, multiphoton miniaturized microscope for mice brain imaging
T. Sahraeibelverdi, A. Shirazi, M. Lee, et al.
A multiphoton, multimodal miniaturized microscope for mice brain imaging is developed. The optical design to provide a compact and lightweight probe uses small lenses, of less than 4mm diameter, selected for performance using raytracing software. The microscope is designed to maintain diffraction-limited resolution for imaging reporters GCAMP6 and eYFP or performing near-infra-red reflection confocal microscopy. A Mai-Tai femtosecond laser is used to provide a 920nm pulse laser, an Insight X3 laser to provide a 960nm pulse laser, and a separate 785nm continuous wave (CW) laser to support NIR reflection with optical sectioning capability with a high signal-to-noise ratio. The miniaturized system was tested as a benchtop prototype using a reflection target, green fluorescent protein, and enhanced yellow fluorescent protein. The resolution for all three wavelengths is less than 2μm. A customized parametric resonance electrostatic MEMS scanner provided the beam scanning of 1.8mm in diameter, resulting in a 350μm by 350μm field of view with a numerical aperture of 0.42, at a working distance of about 350μm. A 4μm core single-mode fiber and a photodiode collect the reflection beam in the confocal mode. Two dichroic mirrors out of the probe are used to combine all three beams toward the probe. Two dichroic mirrors are used for two emission wavelength separations.
Poster Session
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Spectral characterization of the RST prism assembly bandpass filters
The Wide-Field instrument (WFI) for the Roman Space Telescope (RST) features an imaging camera that comprises the Wide-Field Channel (WFC) with several bandpass filters, a spectroscopic dispersion unit called the Grism, and a Prism Assembly (PA), which took the place of the descoped Integral-Field Channel (IFC) assembly. The PA system consists of two prism elements made from S-TIH1 glass (P1) and CaF2 substrate (P2) that together will provide slitless low resolution spectroscopy with a spectral resolution R < 70 at all wavelengths, and R < 170 for wavelengths λ < 0.8 μm, across the full field. One key feature of the P1 element is the application of a bandpass coating that operates in the 0.75-1.8 μm spectral region. The extension of the bandpass towards short wavelengths greatly enhances the capabilities of RST for studies of stellar populations that provides additional means of testing in supernova studies. We have used spectroscopic techniques such as a double-beam monochromator and Fourier Transform InfraRed (FTIR) spectroscopy to characterize the spectral performance of the bandpass coatings of the P1 element. The coating technology used to produce these bandpass optical coatings has been demonstrated in the successful mission of the Mars Perseverance Rover in February of 2021.
Convolution as a model of the LED irradiance pattern
Using a digital image of a distribution of light-emitting diodes (LEDs) or multichip LED, we developed a method to simulate its oblique irradiance spatial distribution on a flat target located at short distances (<20mm). This light oblique irradiance pattern is produced when the LEDs plane or target plane is tilted by an arbitrary angle. The method uses convolution operation between the multichip LED and a special kernel which generates the rotation simulation of the target/LED´s plane. We assumed that LED radiant intensity is directly proportional to the digital imagen. Thus, our method does not requires knowledge about LED data sheet and is not restricted for Lambertian emitters. The model provides the irradiation spatial pattern in function of the irradiation distance for a determined rotation angle. The resulting irradiance patterns on the target, using our method, were pretty similar to the obtained on laboratory experiments.