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OASIS (Orbiting Astronomical Satellite for Investigating Stellar Systems) is a space-based observatory with a 14 m diameter inflatable primary antenna that will perform high spectral resolution observations at terahertz frequencies. The large inflatable aperture, non-traditional surface configuration, and the double layered membrane structure afford unique challenges to the modeling and testing of the primary antenna. A 1-meter prototype of the primary antenna (A1) was built to validate our technical approach. A laser radar coordinate measuring system was adopted to measure the shape of A1. In addition, deflectometry was performed to monitor the stability of A1 during the radar measurement. Test cases pertaining to specific operational conditions expected for the 14 m OASIS primary were explored. The measured data were then compared to the Fichter model and Finite-element Analyzer for Inflatable Membranes (FAIM).

Applications of digital micromirror device for lidar are overviewed. A large Lagrange invariant value makes DMD as one of the attractive beam steering transmitter and receiver solutions for a time-of-flight lidar, especially with its an extended angular throw by synchronized pulsed laser illumination.

SALTUS (Single Aperture Large Telescope for Universe Studies) is a mid/far-infrared telescope concept utilizing a 20-m scale inflatable mirror antenna. The light-weight mirror utilizes a membrane architecture that has been developed and characterized specifically for space-based applications. The telescope's end-to-end optical design and optimization process unleashes the unprecedented photon collecting power of a large space aperture. A series of inflatable mirror prototypes have been designed, manufactured, and tested. These tests confirmed the optical performance of the apertures under space-like conditions. This paradigm changing approach will allow the realization of a new generation of space telescopes far larger than can be achieved utilizing conventional technologies.

A concept of Texas Instrument (TI)-Phase-only Spatial Light Modulator (PLM) is reported which utilizing the dynamic piston motion of PLM pixels to form a discretized blazed grating. By fully manipulating the piston motion of pixels and increasing the available discretization level of the quasi-blazed grating, the Diffraction Efficiency (DE) can achieve close to 99%, which qualifies PLM an ideal candidate for beam steering functionality combining with its MEMS based high refresh rate and large aperture. The DE of the discretized blazed grating is proven to have 86% with 633 nm monochromatic light incident at 25° with 16 discretization levels and 2𝜋 round-trip phase modulation by RCWA algorithm. Furthermore, additional factors which lead to the degradation of diffraction efficiency is also analyzed.

Inflatable membrane primary optics for space telescopes are a smart approach in the context of saving flight payload weight and volume. The Orbiting Astronomical Satellite for Investigating Stellar systems (OASIS) adopted the membrane architecture for primary optics (primary antenna, A1) to have 20 meter diameter collection area with operation bands at the terahertz frequency. The membrane is made of Kapton or Mylar film with an aluminized surface, and the balloon (transparent surface + aluminized surface) is inflated to work as the convex mirror. In order to leverage the carrying volume advantage of inflatable optics, it must be folded during launch and deployed in orbit. The thin membrane film can crumple easily when it is folded, and it should be ironed out when the telescope is deployed for observation. We studied the microroughness and mid-to-high spatial frequency characteristics of the membrane via optical metrology to evaluate the surface properties. Because it is not of traditional shape and material, it is impossible to test with an offthe- shelf interferometer and profilometer. Moreover, the defect spatial frequency of interest is a few hundred microns to millimeters range, so the measurable field and dynamic range need to be in range of a few centimeters with microns resolution. To meet those requirements for metrology, we developed a flexible optics testbed utilizing deflectometry. The microroughness and mid-to-high frequency properties are measured with a white light interferometer and proposed methodology. The test results show that the candidate membrane is suitable for OASIS and this reliable test will guide the further design study of A1 assembly and optical system error budget.

Deformable reflector technology has mainly been used for observations at visible and infrared wavelengths but has yet to be utilized for terahertz wavefront correction. We present an actuator for deformable reflectors that overcomes challenges particular to this wavelength such as a millimeter-scale stroke requirement. Bending moment actuators are used in both the radial and tangential directions to correct low-order wavefront aberrations. Strong and flexible materials such as Delrin are used for the reflector material. Such a deformable antenna can be used to correct wavefronts on future large radio antennae such as the Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS). This antenna uses a 20-meter thin membrane as its primary radio wave collector. A deformable reflector may be added to this system to allow for looser tolerances on the primary antenna shape and correct for wavefront errors inherent in an inflatable optic. To predict the wavefront errors that may be expected when using this type of thin membrane primary reflector, TVAC (Thermal Vacuum Chamber) test methods are also presented in these proceedings.

The Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS) is a 20-meter class proposed space terahertz observatory supported by an inflatable membrane architecture. To measure 150 mm and 1m models of the A1 reflective membrane antenna, two deflectometry configurations were designed. The smaller assembly and its corresponding deflectometer were simulated, built in our laboratory, and produce a reconstructable signal for clocked measurements of the highly-sloped pneumatic surface. We use non-sequential raytracing simulation to bound the maximum contributions of all shape errors and suggest the N-Rotations algorithm to remove the remaining radially asymmetric errors. Then, the 1m prototype assembly was tested inside a thermal vacuum chamber (TVAC). Differential deflectometry measurements tracked the 1m surface shape changes as it was subjected to a variety of environmental setpoints, cycled between three inflation gases, and also during controlled puncture. We summarize our development and results for absolute measurements as well as from TVAC testing.

The Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS) is a 17 meter class space observatory concept that will perform heterodyne and high spectral resolution observations at terahertz wavelength ranging from 81 to 659 micrometers to observe the transition of water and its isotopologues and other molecular species[1]. The baseline design, in particular with an inflatable primary antenna achieves orders of magnitude larger photon collection area >120 m2 and diffraction limited performance at field of view (FOV) of +/- 0.05 deg with a simple tip/tilt scanner and over 0.2 degrees with an advanced scanning field lens design. The THz observatory with such an inflatable primary system involves an interesting challenge in optical design. The surface shape of the inflatable primary antenna, known as Hencky surface, induces 4th or higher order deformation of reflector surface which is corrected by following 3-mirror correction optics, with a power arrangement which is similar to Offner’s null corrector optics. The same optical architecture is also applicable for more parabola like inflatable antenna shape. The diffraction limited intermediate image field is scanned by a mirror tip-tilt scanner, alternatively for a larger FOV scanning a field lens, refractive or reflective, rigidly connected to the scanning mirror is employed. The design with thin reflective field lens or all refractive design increases overall photon throughput while accommodating broad band spectral range. Along with the 1st and 3rd order optical design procedure, in this presentation, We address challenges in optical design of such a large and inflatable antenna based photon collection system in THz astronomy, including correction of aberration from a membrane antenna, and relay optics to match mode field of antenna to that of THz heterodyne detectors.

Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS) is a mission concept being developed in preparation for the 2021 MidEX Announcement of Opportunity. This paper describes the key features of the OASIS architecture as they are currently understood. OASIS’s choice of a large inflatable primary reflector results in large collection areas at very high mass efficiency enabling the science mission. We describe the spacecraft bus, based on Northrop Grumman’s LEOstar-2, and the receiver, a heritage design based on the GUSTO balloon heterodyne system. We also discuss the observing strategy and pointing requirements from its planned L1 location. Particular emphasis is placed on challenges to the design, such as momentum management, balancing consumable mass allocations, thermal management, and testing.

The uninflated shape configurations of parabolic and spherical membrane mirrors were calculated by solving the inverse problem, i.e., given the design inflation pressure, the membrane material and geometric properties, what must be the initial uninflated shape such that on inflation to the design pressure, the exact desired surface of revolution is obtained. The resulting first order nonlinear differential equation was numerically integrated using the boundary conditions. The initial uninflated shape was then subjected to a forward transformation using FAIM, a proprietary geometric nonlinear membrane finite element code. FAIM has been validated against exact analytical solutions for both small and extremely large deformations that are up to eight orders of magnitude larger compared with the starting undeflected shape. Simulations reveal that to fabricate a very accurate and precise inflated membrane mirror relative to the design parameters, one must not only accurately measure and input the moduli in both meridional and hoop directions but an accurately measured Poisson’s ratio as well. The code was used to guide the membrane mirror design. For very small aperture diameters, the initial uninflated shape may be fabricated by thermo-forming the membrane. For aperture diameters exceeding one meter however, the membrane mirror is built with discrete gores that are joined together with tapes at the seams. This provided the impetus to write a companion computer code FLATE, to calculate the gore shapes using a slight modification of the solution to the inverse transformation equation to account for the presence of the seam tapes. After the gores were determined, the resulting final inflated shape was calculated and verified using FAIM. Sensitivity analyses can now be carried out to determine the resulting surface shape as a function of the different sources of error: gore width, gore length, perimeter attachment uncertainties, thermal effects, variation of material properties over the membrane continuum and inflation pressure changes. The code has been shown to be more robust than equivalent commercial analytical packages in so far as membrane, cable and space-frame element combinations are concerned. In particular, the analytical and finite element codes were used in the preliminary assessment of a membrane optic for the OASIS Mission (Orbiting Astronomical Satellite for Investigating Stellar Systems) [1]. The OASIS is a 20-meter class space observatory operating at high spectral resolution in the terahertz frequencies. Over its nominal 2-year mission it will probe conditions and search for biogenic molecules on hundreds of protoplanetary disks and other solar system objects.

The recently reported “Angular Spatial Light Modulator” (ASLM) light engine, using pulsed illumination synchronized to a Digital Micromirror Device (DMD), shows significant promise to enhance pixel counts of Near-to-Eye Displays (NED) without increasing package volume, but requires an uncommon illumination driver. We present a field effect transistor based constant-current driver that is fast, compact, and scalable to RGB illumination. The digital-to-analog convertor modulates intensity on-the-fly for illumination-based multiplexing. The driver outputs 100 ns pulses, up to 24 kHz repetition rate. The circuit is demonstrated for two laser diodes and for two LEDs in an ASLM-enhanced pixel count display.

Desirable fields-of-view, angular resolutions, and form factors of near-to-eye AR/VR/MR displays require order-ofmagnitude increases in pixel count and pixel density of spatial light modulators (SLM). We present an in-plane angularspatial light modulation technique to increase the independent output display pixels of a DMD by three orders of magnitude to achieve gigapixel output from a sub-megapixel device. Pulsed illumination synchronized to a DMD’s micromirror actuation realizes pixel-implemented and diffraction-based angular modulation, and fine source array control increases angular selectivity. The gigapixel output is demonstrated in a 1440-perspective display, each perspective having the DMD’s full native XGA resolution, across a 43.9°×1.8° FOV viewing angle. 8-bit multi-perspective videos at 30 FPS are demonstrated, and pixel-implemented multi-focal-plane image generation is realized. Implications for near-to-eye displays are discussed.

A holographic lidar concept established on the Digital Micromirror Mirror (DMD)-based hybrid light modulation is reported, which multiplexes coarse-steering by sawtooth phase modulation and fine-steering by binary amplitude modulation. The hybrid steering is achieved by overlaying displayed Computer-Generated Holograms (CGHs) with a sawtooth blazed grating phase mask, which the blaze angle programmed by synchronized short-pulse illumination of transitioning micromirrors creating the CGHs. The steering principle is demonstrated as a 2D beam steering scheme with a 532 nm visible pulse laser, and implemented into a 905 nm lidar system with a 44° field-of-view, 0.9°×0.4° angular resolution, 7.8 FPS video frame rate, and 1 m detection distance.

We introduce our recent work on the occlusion-capable near-to-eye display. Our implementation uses only a single digital micromirror device (DMD) both for the real scene masking and virtual image display. The real scene imaging onto the DMD and the mixed scene projection toward the eye are achieved using a single optics of polarization-based double-path configuration. These single DMD and the shared optics feature contributes to the reduction of the overall system volume. In the presentation, we explain the principle and introduces our recent experimental results demonstrating 60Hz display of color virtual images with per-pixel occlusion in over 90% maximum occlusion ratio.

Diffractive beam steering by Digital Micromirror Device enables an efficient way to simultaneously manipulate light both in the spatial and angular domain by spatial and time multiplexing while keeping large area and angular throw product. Long-term stability and susceptibility of beam and image steering rely on how synchronization of ns laser pulse and transition of micromirrors is maintained over time and through variation of device temperature. The long-term performance of the beam steering is evaluated by monitoring diffraction efficiency over 350 hrs. with a 360 Hz repetition rate. Also, diffraction efficiency was monitored while increasing the temperature of the mirror array from 45 to 75 degrees C. Over the period, stable beam steering was observed. A decrease in diffraction efficiency under high temperature was observed. We confirmed readjusting synchronization timing recovered the diffraction efficiency to the level of room temperature. The experimental results show a stable operation of diffractive beam steering by DMD is feasible for the long term, and even under variation of temperature by adaptively adjusting synchronization timing of laser pulse to starting timing of DMD mirror transition.

Orders-of-magnitude increases are desired in the pixel count and density of spatial light modulators (SLMs) for next-gen displays. We present in-plane and simultaneous angular-spatial light modulation by a micro electro mechanical system (MEMS)-based SLM, a digital micromirror device (DMD), to generate gigapixel output by time and angular multiplexing. Pulsed illumination synchronized to the micromirror actuation achieves pixel-implemented and diffraction-based angular modulation, and source multiplexing increases angular selectivity. We demonstrate 1440-perspective image output across a 43.9 ∘ × 1.8 ∘ FOV, 8-bit multi-perspective videos at 30 FPS, and multi-focal-plane image generation. We discuss scalability to terapixels and implications for near-to-eye displays.

Digital Micromirror Device (DMD) is a commercial and mass-produced Micro Electromechanical System (MEMS) spatial light modulator (SLM) consisting of millions of mirrors that spatially modulate lights by switching it between on and off states. Between the on- and off-states, transitional states exist where micromirror changes tilt angle. We report a method to control the transitional time of the mirror array by controlling the pressure of the ambient air. The increased air pressure to 100 psi increases mirrors transitional time by 20%. We also address the possibility of controlling the transitional time electrically.

The ODS has been held as part of SPIE Optics + Photonics since 2014. Formerly, the scope of ODS was optical data storage, but since 2018, it has been extended to industrial optical devices and systems. The new scope includes emerging industrial domains such as automotive, IoT, big data, healthcare, security, etc. We are pleased that the number of papers is increasing in the last three years, and that their areas are expanding from traditional optical data storage to various industrial optical devices and systems. This means that the new scope of ODS has been recognized by optics research and development community in industry. We hope that all of you will enjoy this conference and help make it more attractive in the future.

The ability of space telescopes to see into nascent protostellar systems and even further into our universe is driven by the size of their deployable light collection area. While large monolithic mirrors typically weigh tons, inflatable membrane mirrors present a scalable, ultralightweight alternative. Leveraging decades of advances in adaptive optics technology, the possibility of a well-corrected 20 meter-class space observatory such as the Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS) is strikingly feasible. However, with great aperture size, comes great metrology requirements. Membrane reflectors are characteristically structured as one transparent and one metallized polymer membrane sealed around a steel tensioning ring. The inflated surface does not naturally conform to a known or prescribed conic but an approximate Hencky surface. Furthermore, multiple internal reflections and polarization interactions between the dielectric and metal layers disturb coherent light that probes it. A non-contact, full-aperture testing method is needed and further, one that can test highly varying membranes after thermoforming too. We present our method in obtaining the absolute shape of thermally formed, inflatable reflectors for space telescopes. Our work measures a 1-meter prototype of the OASIS primary inflatable mirror. Evolving from laser distance scanning to photogrammetry to deflectometry, our survey of metrology techniques for inflatable membrane optics is discussed.

Occlusion of a real scene by displayed virtual images mitigates incorrect depth cues and enhances image visibility in augmented reality applications. In this Letter, we propose a novel optical scheme for the occlusion-capable optical-see-through near-eye display. The proposed scheme uses only a single spatial light modulator, as the real-scene mask and virtual image display simultaneously. A polarization-based double-pass configuration is also combined, enabling a compact implementation. The proposed scheme is verified by optical experiments which demonstrate a 60 Hz red-green-blue video display with a 4-bit depth for each color channel and per-pixel dynamic occlusion of a 90.6% maximum occlusion ratio.

Imaging distant objects with increasing spatial resolution is instrumental towards furthering space exploration abilities. Telescopic imaging of exoplanets and other objects requires mirrors with large surfaces which when used at terahertz frequencies can further capture object chemistry, mass structure and dynamics. Membrane mirrors could lead to a dramatic scale up in size of telescope mirrors deployed on orbit. Large membrane reflectors built in the past have had a primary challenge of uncontrolled inflation dynamics and surface shape. A major contribution to such inaccuracies has been attributed to manufacturing techniques employed. The surface shape attained by a tensioned membrane has been described as an oblate spheroid or Hencky surface. Traditionally built out of smaller gore units, membrane mirrors tend to attain faceted final shapes that deviate from the intended. They have unreliable and unrepeatable final surface shapes. This makes the design of corrective optics difficult. Further, complex assembly jigs are required for the precise manufacture of such membrane units. A repeatable and scalable manufacturing method is required to harness the advantages offered by membrane reflectors. Our present work is focused on thermally formed membrane reflectors. This involves heating a whole flat membrane close to its glass-transition region followed by pressurization at a constant fixed temperature. The intent is to induce plastic deformation of the membrane causing a retention of induced curvature when cooled down. This method eliminates breaking down the membrane structure into smaller gore units and can be scaled over to vast membrane sizes. An experimental set-up has been designed and built to thermally form a 1-meter diameter Mylar membrane reflector and conduct shape measurement on its surface. We present development efforts in the design, manufacture and surface shape measurement of thermally formed reflectors. The results are being used to validate thermo-structural simulations conducted on the expected membrane surface behavior. Further analysis is underway to understand optimal circumferential stress distributions to improve the reliability of obtained membrane shapes. Our work contributes towards an understanding of key design variables in the development of tensioned thermally formed membrane reflectors that can provide a potential pathway towards dramatic scale up in size of such mirrors.

The “Angular Spatial Light Modulator” (ASLM) utilizes digital micromirror device (DMD) as a binary patterned programmable blazed grating to increase number of output pixels of a DMD by merging geometric and diffractive optical capabilities of the DMD. We demonstrate series of capabilities of the ASLM for beam and pattern steering. In particular, a single-chip beam steering lidar, an extended FOV display, a light-field projector, and a multi-view display which can be implemented into AR/VR systems. We also present our metrology results of wavefront distortion of DMD while micro mirrors are transitioning over between on and off states.

A single Digital Micromirror Device with a single illumination source projects multiple, independent patterns into corresponding directions across a nearly-doubled angular extent by time multiplexing and by nanosecond illumination pulse synchronization for a binary patterned programmable blazed grating. The resulting “Angular Spatial Light Modulator” (ASLM) system nearly-doubles the etendue of a DMD-type SLM and creates a multiplication factor for the output pixel count and effective pixel density. We demonstrate an extended FOV display, a light-field projector, and a multi-view display which can be implemented into AR/VR systems. We present an implementation update using the DLP7000 DMD, increasing output pixel count by and effective pixel density orders-of-magnitude beyond traditional SLM systems while achieving an extended field-of-view and/or eye-box size due to the increased etendue.

We use convolutional neural networks to recover images optically down-sampled by 6.7 × using coherent aperture synthesis over a 16 camera array. Where conventional ptychography relies on scanning and oversampling, here we apply decompressive neural estimation to recover full resolution image from a single snapshot, although as shown in simulation multiple snapshots can be used to improve signal-to-noise ratio (SNR). In place training on experimental measurements eliminates the need to directly calibrate the measurement system. We also present simulations of diverse array camera sampling strategies to explore how snapshot compressive systems might be optimized.

Small pixel pitch with a large array size is highly anticipated for solid-state lidar transmitter and receiver. We demonstrate 2D beam steering with reduced effective pixel pitch by harnessing transitional state of the mirror array.