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NASA NTRS2003

Investigation of Space Interferometer Control Using Imaging Sensor Output Feedback

Numerous space interferometry missions are planned for the next decade to verify different enabling technologies towards very-long-baseline interferometry to achieve high-resolution imaging and high-precision measurements. These objectives will require coordinated formations of spacecraft separately carrying optical elements comprising the interferometer. High-precision sensing and control of the spacecraft and the interferometer-component payloads are necessary to deliver sub-wavelength accuracy to achieve the scientific objectives. For these missions, the primary scientific product of interferometer measurements may be the only source of data available at the precision required to maintain the spacecraft and interferometer-component formation. A concept is studied for detecting the interferometer's optical configuration errors based on information extracted from the interferometer sensor output. It enables precision control of the optical components, and, in cases of space interferometers requiring formation flight of spacecraft that comprise the elements of a distributed instrument, it enables the control of the formation-flying vehicles because independent navigation or ranging sensors cannot deliver the high-precision metrology over the entire required geometry. Since the concept can act on the quality of the interferometer output directly, it can detect errors outside the capability of traditional metrology instruments, and provide the means needed to augment the traditional instrumentation to enable enhanced performance. Specific analyses performed in this study include the application of signal-processing and image-processing techniques to solve the problems of interferometer aperture baseline control, interferometer pointing, and orientation of multiple interferometer aperture pairs.

Leitner, Jesse A.↗

NASA NTRS2018

Infrared Computer-Generated Holograms: Design and Application for the WFIRST Grism Using Wavelength-Tuning Interferometry

Interferometers using computer-generated holograms (CGHs) have become the industry standard to accurately measure aspheric optics. The CGH is a diffractive optical element that can create a phase or amplitude distribution and can be manufactured with low uncertainty using modern lithographic techniques. However, these CGHs have conventionally been used with visible light and piezo-shifting interferometers. Testing the performance of transmissive optics in the infrared requires infrared CGHs and an infrared interferometer. Such an instrument is used in this investigation, which introduces its phase shift via wavelength-tuning. A procedure on how to design and manufacture infrared CGHs and how these were successfully used to model and measure the Wide-Field Infrared Survey Telescope grism elements is provided. Additionally, the paper provides a parametric model, simulation results, and calculations of the errors and measurements that come about when interferometers introduce a phase variation via wavelength-tuning interferometry to measure precision aspheres.

Communication↗

DOE OSTI2025

Nonlinear analog processing with anisotropic nonlinear films

Digital signal processing is the cornerstone of several modern-day technologies, yet in multiple applications it faces critical bottlenecks related to memory and speed constraints. Thanks to recent advances in metasurface design and fabrication, light-based analog computing has emerged as a viable option to partially replace or augment digital approaches. Several light-based analog computing functionalities have been demonstrated using patterned flat optical elements, with great opportunities for integration in compact nanophotonic systems. So far, however, the available operations have been restricted to the linear regime, limiting the impact of this technology to a compactification of Fourier optics systems. In this paper, we introduce nonlinear operations to the field of metasurface-based analog optical processing, demonstrating that nonlinear optical phenomena, combined with nonlocality in flat optics, can be leveraged to synthesize kernels beyond linear Fourier optics, paving the way to a broad range of new opportunities. As a practical demonstration, we report the experimental synthesis of a class of nonlinear operations that can be used to realize broadband, polarization-selective analog-domain edge detection.

analog image processing↗

NASA NTRS1986

Diffraction-limited performance of grazing incidence optical systems

Diffraction effects of X-ray optical systems are often (justifiably) ignored due to the small wavelength of the X-ray radiation. However, the extremely large obscuration ratio inherent to grazing incidence optical systems produces a profound degradation of the diffraction image over that produced by a moderately obscured aperture of the same diameter. The contradictory requirements of large collecting area and relatively short length of optical elements has tended to result in proposed designs containing many concentric shells with increasingly higher obscuration ratios. In this paper it is shown that diffraction effects in such systems can significantly affect the achievable optical performance at the low energy (long wavelength) end of the intended operating spectral range. Parametric diffraction-limited performance predictions for both imaging and spectrographic applications will be presented and compared to AXAF performance goals and/or BBXRT fabrication techniques.

Harvey, James E.↗

DOE OSTI2021

Imaging system and method for enhanced visualization of near surface vascular structures

A sub-dermal structure visualization system and method is disclosed. The system may use an illumination module including: a near-infrared (NIR) light source adapted to substantially uniformly illuminate an imaged area including sub-dermal regions thereof with NIR light; and a first optical system including at least one optical element for controlling at least one of spectral and polarization properties of the NIR light prior to illuminating the imaged area. An imaging module rejects unwanted signals from an imaged area while passing desired optical signals that are to be received by an image acquisition module. The desired optical signals can comprise a vein visualization signal to assist in visualizing a vascular structure below a skin layer of a patient.

Demos, Stavros G.↗

NASA NTRS1984

Optical flip-flops and sequential logic circuits using a liquid crystal light valve

This paper is concerned with the application of optics to digital computing. A Hughes liquid crystal light valve is used as an active optical element where a weak light beam can control a strong light beam with either a positive or negative gain characteristic. With this device as the central element the ability to produce bistable states from which different types of flip-flop can be implemented is demonstrated. In this paper, some general comments are first presented on digital computing as applied to optics. This is followed by a discussion of optical implementation of various types of flip-flop. These flip-flops are then used in the design of optical equivalents to a few simple sequential circuits such as shift registers and accumulators. As a typical sequential machine, a schematic layout for an optical binary temporal integrator is presented. Finally, a suggested experimental configuration for an optical master-slave flip-flop array is given.

Fatehi, M. T.↗

NASA NTRS2011

Development of Multi-Beam Long Trace Profiler

In order to fulfill the angular resolution requirements and make the performance goals for future NASA missions feasible, it is crucial to develop instruments capable of fast and precise figure metrology of x-ray optical elements for further correction of the surface errors. The Long Trace Profilometer (LTP) is an instrument widely used for measuring the surface figure of grazing incidence X-ray mirrors. In the case of replicated optics designed for x-ray astronomy applications, such as mirrors and the corresponding mandrels have a cylindrical shape and their tangential profile is parabolic or hyperbolic. Modern LTPs have sub-microradian accuracy, but the measuring speed is very low, because the profilometer measures surface figure point by point using a single laser beam. The measurement rate can be significantly improved by replacing the single optical beam with multiple beams. The goal of this study is to demonstrate the viability of multi-beam metrology as a way of significantly improving the quality and affordability of replicated x-ray optics. The multi-beam LTP would allow one- and two-dimensional scanning with sub-microradian resolution and a measurement rate of about ten times faster compared to the current LTP. The design details of the instrument's optical layout and the status of optical tests will be presented.

Kilaru, Kiranmayee↗

NASA NTRSDate not supplied

Preliminary Design of a Deployable Optical Space Array Based on a Thickened Origami Flasher Pattern

Performance of space-based optics could be greatly enhanced by using deployable origami-based arrays, which can offer a large aperture size relative to their stowed volume when compared to traditional technology, thus improving imaging quality. In this work, we select, develop, and adapt the origami flasher pattern to serve as the foundation for a deployable array that shows promise for meeting stringent optical requirements. We apply a novel thickness accommodation technique, outline an approach for implementing the technique, improve stability by adjusting geometric characteristics of the pattern, and create an array of frames for housing optical elements in a co-planar configuration. Problems of non-rigid foldability in the flasher pattern are addressed. A prototype is created and tested. We find that the deployable flasher shows promise as an optical array. By following the guidelines in this work, more efficient and powerful optical arrays can be developed.

Jared Hunter↗

NASA NTRS1989

Environmental testing of a diode-laser-pumped Nd:YAG laser and a set of diode-laser-arrays

Results of the environmental test of a compact, rigid and lightweight diode-laser-pumped Nd:YAG laser module are discussed. All optical elements are bonded onto the module using space applicable epoxy, and two 200 mW diode laser arrays for pump sources are used to achieve 126 mW of CW output with about 7 percent electrical-to-optical conversion efficiency. This laser assembly and a set of 20 semiconductor diode laser arrays were environmentally tested by being subjected to vibrational and thermal conditions similar to those experienced during launch of the Space Shuttle, and both performed well. Nevertheless, some damage to the laser front facet in diode lasers was observed. Significant degradation was observed only on lasers which performed poorly in the life test. Improvements in the reliability of the Nd:YAG laser are suggested.

Hemmati, H.↗

NASA NTRS1992

Effect of process conditions and chemical composition on the microstructure and properties of chemically vapor deposited SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x)

Subatmospheric pressure CVD processes have been developed to produce theoretically dense, highly pure, void-free and large area bulk materials, SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x). These materials are used for optical elements, such as mirrors, lenses and windows, over a wide spectral range from the VUV to the IR. We discuss the effect of CVD process conditions on the microstructure and properties of these materials, with emphasis on optical performance. In addition, we discuss the effect of chemical composition on the properties of the composite material ZnS(x)Se(1-x). We first present a general overview of the bulk CVD process and the relationship between process conditions, such as temperature, pressure, reactant gas concentration and growth rate, and the microstructure, morphology and properties of CVD-grown materials. Then we discuss specific results for CVD-grown SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x).

Pickering, Michael A.↗

NASA NTRS2011

General Tool for Evaluating High-Contrast Coronagraphic Telescope Performance Error Budgets

The Coronagraph Performance Error Budget (CPEB) tool automates many of the key steps required to evaluate the scattered starlight contrast in the dark hole of a space-based coronagraph. The tool uses a Code V prescription of the optical train, and uses MATLAB programs to call ray-trace code that generates linear beam-walk and aberration sensitivity matrices for motions of the optical elements and line-of-sight pointing, with and without controlled fine-steering mirrors (FSMs). The sensitivity matrices are imported by macros into Excel 2007, where the error budget is evaluated. The user specifies the particular optics of interest, and chooses the quality of each optic from a predefined set of PSDs. The spreadsheet creates a nominal set of thermal and jitter motions, and combines that with the sensitivity matrices to generate an error budget for the system. CPEB also contains a combination of form and ActiveX controls with Visual Basic for Applications code to allow for user interaction in which the user can perform trade studies such as changing engineering requirements, and identifying and isolating stringent requirements. It contains summary tables and graphics that can be instantly used for reporting results in view graphs. The entire process to obtain a coronagraphic telescope performance error budget has been automated into three stages: conversion of optical prescription from Zemax or Code V to MACOS (in-house optical modeling and analysis tool), a linear models process, and an error budget tool process. The first process was improved by developing a MATLAB package based on the Class Constructor Method with a number of user-defined functions that allow the user to modify the MACOS optical prescription. The second process was modified by creating a MATLAB package that contains user-defined functions that automate the process. The user interfaces with the process by utilizing an initialization file where the user defines the parameters of the linear model computations. Other than this, the process is fully automated. The third process was developed based on the Terrestrial Planet Finder coronagraph Error Budget Tool, but was fully automated by using VBA code, form, and ActiveX controls.

Marchen, Luis F.↗

NASA NTRS2012

NASA Tech Briefs, May 2012

Topics covered include: An "Inefficient Fin" Non-Dimensional Parameter to Measure Gas Temperatures Efficiently; On-Wafer Measurement of a Multi-Stage MMIC Amplifier with 10 dB of Gain at 475 GHz; Software to Control and Monitor Gas Streams; Miniaturized Laser Heterodyne Radiometer (LHR) for Measurements of Greenhouse Gases in the Atmospheric Column; Anomaly Detection in Test Equipment via Sliding Mode Observers; Absolute Position of Targets Measured Through a Chamber Window Using Lidar Metrology Systems; Goldstone Solar System Radar Waveform Generator; Fast and Adaptive Lossless Onboard Hyperspectral Data Compression System; Iridium Interfacial Stack - IrIS; Downsampling Photodetector Array with Windowing; Optical Phase Recovery and Locking in a PPM Laser Communication Link; High-Speed Edge-Detecting Line Scan Smart Camera; Optical Communications Channel Combiner; Development of Thermal Infrared Sensor to Supplement Operational Land Imager; Amplitude-Stabilized Oscillator for a Capacitance-Probe Electrometer; Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data; Histogrammatic Method for Determining Relative Abundance of Input Gas Pulse; Predictive Sea State Estimation for Automated Ride Control and Handling - PSSEARCH; LEGION: Lightweight Expandable Group of Independently Operating Nodes; Real-Time Projection to Verify Plan Success During Execution; Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data; Web-Based Customizable Viewer for Mars Network Overflight Opportunities; Fabrication of a Cryogenic Terahertz Emitter for Bolometer Focal Plane Calibrations; Fabrication of an Absorber-Coupled MKID Detector; Graphene Transparent Conductive Electrodes for Next- Generation Microshutter Arrays; Method of Bonding Optical Elements with Near-Zero Displacement; Free-Mass and Interface Configurations of Hammering Mechanisms; Wavefront Compensation Segmented Mirror Sensing and Control; Long-Life, Lightweight, Multi-Roller Traction Drives for Planetary Vehicle Surface Exploration; Reliable Optical Pump Architecture for Highly Coherent Lasers Used in Space Metrology Applications; Electrochemical Ultracapacitors Using Graphitic Nanostacks; Improved Whole-Blood-Staining Device; Monitoring Location and Angular Orientation of a Pill; Molecular Technique to Reduce PCR Bias for Deeper Understanding of Microbial Diversity; Laser Ablation Electrodynamic Ion Funnel for In Situ Mass Spectrometry on Mars; High-Altitude MMIC Sounding Radiometer for the Global Hawk Unmanned Aerial Vehicle; PRTs and Their Bonding for Long-Duration, Extreme-Temperature Environments; Mid- and Long-IR Broadband Quantum Well Photodetector; 3D Display Using Conjugated Multiband Bandpass Filters; Real-Time, Non-Intrusive Detection of Liquid Nitrogen in Liquid Oxygen at High Pressure and High Flow; Method to Enhance the Operation of an Optical Inspection Instrument Using Spatial Light Modulators; Dual-Compartment Inflatable Suitlock; Large-Strain Transparent Magnetoactive Polymer Nanocomposites; Thermodynamic Vent System for an On-Orbit Cryogenic Reaction Control Engine; Time Distribution Using SpaceWire in the SCaN Testbed on ISS; and Techniques for Solution- Assisted Optical Contacting.

Source record↗

NASA NTRS1992

A dual purpose optical truss laser metrology system for a space-based far-IR segmented telescope: Figure maintenance and pointing control

To obtain imaging performance as for monolithic mirrors, large segmented reflectors used for astronomy must be actively aligned and pointed to extreme levels of precision. A system concept for a dual purpose optical truss laser metrology system is described which is used for both figure and alignment maintenance and telescope pointing. A two-stage figure active control approach was developed for several proposed spaceborne far infrared segmented telescopes, one of which is the 10-20 meters Large Deployable Reflector (LDR). The first active control stage, the figure initialization control system, aligns the optical elements (i.e., the primary segments, secondary and focal plane assembly) based on images obtained. The second stage, the figure maintenance control system, maintains the alignment between re-initializations using measurements provided by laser interferometers arranged in an optical truss configuration. It measures the relative positions and alignments of the telescope segments so that a controller can reposition them appropriately. The application of this optical truss for figure maintenance control is the subject of the first part of this paper. The second portion of this paper discusses the application of the optical truss to telescope pointing. Here, the laser metrology system is used to transfer pointing information from an external fine guidance sensor (FGS) to the telescope optical boresight as defined by the primary mirror, secondary mirror, and focal plane assembly. Thus, any alignment variations between the two boresights can be observed and accounted for.

Lau, Kenneth↗

NASA NTRS1992

Diode pumped, regenerative Nd:YAG ring amplifier for space application

The study reviews the research and development of a prototype laser used to study one possible method of short-pulse production and amplification, in particular, a pulsed Nd:YAG ring laser pumped by laser diode arrays and injected seeded by a 100-ps source. The diode array pumped, regenerative amplifier consists of only five optical elements, two mirrors, one thin film polarizer, one Nd:YAG crystal, and one pockels cell. The pockels cell performed both as a Q-switch and a cavity dumper for amplified pulse ejection through the thin film polarizer. The total optical efficiency was low principally due to the low gain provided by the 2-bar pumped laser head. After comparison with a computer model, a real seed threshold of about 10 exp -15 J was achieved because only about 0.1 percent of the injected energy mode-matched with the ring.

Coyle, D. B.↗

NASA NTRS1994

Inter-comparison of Wildfire and High-resolution Interferometer Sounder (HIS) data from STORM-FEST: An investigation of wildfire spectral channel discrepancies

This simultaneous collection of HIS spectral measurements aboard the ER-2 during STORM-FEST provided a means to explore calibration problems in the infrared bands of the Wildfire instrument. Large discrepancies in brightness temperatures were noted in Wildfire bands designed to sample the 'wings' of the strong ozone absorption band centered at 9.6 microns, where the atmospheric transmittance changes rapidly with wavelength. Examination of interchannel relationships in Wildfire data and subsequent comparison to Wildfire data synthesized from the HIS measurements suggests that a wavelength shift in the channel spectral response from those determined in the laboratory may have occurred. Based on comparisons from several flights, this spectral shift has been empirically determined to be about 0.15 micron. It is speculated that this problem resulted from a slight misalignment of the spectrometer grating or other optical elements, or was a result of extreme range in temperatures experienced by the instrument throughout the course of an ER-2 flight. A consequence of this temperature fluctuation may be a change in a position of the grating in the optical path and could result in the variations in channel spectral response during flight. These findings for Wildfire may have significant bearing on future use of the MAS because of the similarities to the original Wildfire configuration.

Jedlovec, G. J.↗

NASA NTRS2012

Variable Sampling Mapping

The performance of an optical system (for example, a telescope) is limited by the misalignments and manufacturing imperfections of the optical elements in the system. The impact of these misalignments and imperfections can be quantified by the phase variations imparted on light traveling through the system. Phase retrieval is a methodology for determining these variations. Phase retrieval uses images taken with the optical system and using a light source of known shape and characteristics. Unlike interferometric methods, which require an optical reference for comparison, and unlike Shack-Hartmann wavefront sensors that require special optical hardware at the optical system's exit pupil, phase retrieval is an in situ, image-based method for determining the phase variations of light at the system s exit pupil. Phase retrieval can be used both as an optical metrology tool (during fabrication of optical surfaces and assembly of optical systems) and as a sensor used in active, closed-loop control of an optical system, to optimize performance. One class of phase-retrieval algorithms is the iterative transform algorithm (ITA). ITAs estimate the phase variations by iteratively enforcing known constraints in the exit pupil and at the detector, determined from modeled or measured data. The Variable Sampling Mapping (VSM) technique is a new method for enforcing these constraints in ITAs. VSM is an open framework for addressing a wide range of issues that have previously been considered detrimental to high-accuracy phase retrieval, including undersampled images, broadband illumination, images taken at or near best focus, chromatic aberrations, jitter or vibration of the optical system or detector, and dead or noisy detector pixels. The VSM is a model-to-data mapping procedure. In VSM, fully sampled electric fields at multiple wavelengths are modeled inside the phase-retrieval algorithm, and then these fields are mapped to intensities on the light detector, using the properties of the detector and optical system, for comparison with measured data. Ultimately, this model-to-data mapping procedure enables a more robust and accurate way of incorporating the exit-pupil and image detector constraints, which are fundamental to the general class of ITA phase retrieval algorithms.

Smith, Jeffrey, S.↗

NASA NTRS1973

Plume mass flow and optical damage distributions for an MMH/N2O4 RCS thruster

The data obtained from two recent experiments conducted in a continuing series of experiments at the Lewis Research Center into the contamination characteristics of a 5-pound thrust MMH/N2O4 engine are presented. The primary objectives of these experiments were to establish the angular distribution of condensible exhaust products within the plume and the corresponding optical damage angular distribution of transmitting optical elements attributable to this contaminant. The plume mass flow distribution was measured by five quartz crystal microbalances (QCM's) located at the engine axis evaluation. The fifth QCM was located above the engine and 15 deg behind the nozzle exit plane. The optical damage was determined by ex-situ transmittance measurements for the wavelength range from 0.2 to 0.6 microns on 2.54 cm diameter fused silica discs also located at engine centerline elevation. Both the mass deposition and optical damage angular distributions followed the expected trend of decreasing deposition and damage as the angle between sensor or sample and the nozzle axis increased. A simple plume gas flow equation predicted the deposition distribution reasonably well for angles of up to 55 degrees. The optical damage measurements also indicated significant effects at large angles.

Spisz, E. W.↗

NASA NTRS1991

Astrometry using the Hubble Space Telescope fine guidance sensors

Plans for the use of the three fine guidance sensors (FGSs) of the NASA Hubble Space Telescope for direct astrometric observations are reviewed. Topics addressed include the optical elements and detectors of the FGSs, the basic and astrometric operating modes of the FGSs, spacecraft pointing control during astrometric observations, and the astrometric data-reduction software provided to HST users. Particular attention is given to the calibration procedures for optical-field angle distortion, the plate scale, filter-wedge errors, lateral color effects, secular changes, velocity aberration, and transfer function. Also discussed are the steps being taken to verify the HST orbit. It is pointed out that the performance of the interferometric FGSs should not be affected by the focusing problems of the main HST instrument.

Duncombe, Raynor L.↗