This PDF file contains the front matter associated with SPIE Proceedings Volume 12669, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

We use a known optic, a catalog off-axis parabola, as a reference to both model in Zemax and to align while tracking the position of the focus in 3 degrees of freedom (DOF) and the tilt of the auto-reflecting flat in 2 DOF to demonstrate a systematic approach to alignment. The aberrations present at each step of the experimental procedure are monitored using an autostigmatic microscope.

Most optical systems will display signs of axial coma when a single lens is decentered with respect to the others. Optical designers will usually select a sensitive lens as a compensator to correct that misalignment coma during assembly rather than tightening the decenter tolerances to excessively tight values. Recently, a lens design implemented two adjacent compensating lenses to address two errors – axial coma and balancing field performance. During the course of compensating the as-fabricated design, an unusual form of astigmatism was noted that was unexpected and not previously seen in our practice. This atypical astigmatism is hypothesized to be due to the two compensator lenses being decentered with respect to each other and the system optical axis itself. It scales linearly with field angle and is oriented in a specific direction across the field of view. This is opposed to natural field astigmatism, which is rotationally symmetric about the axis and varies quadratically with the field of view. Recent papers discussing linear astigmatism have indicated that it could be a problem with wide FOV optical systems, but we have found that it is evident in even moderate FOV optical systems. Further analysis has shown that this astigmatism arises when the two lenses decenter in opposite directions by roughly equal amounts. This suggests that the method of correction is straightforward in implementation, i.e., move the lenses towards each other. As often happens, orthogonal motion is usually needed as one iterates towards the final solution.

This paper compares two different ways of aligning optical systems using deflectometry: a novel method incorporating the sine condition test and deflectometry, and conventional multi-field points measuring deflectometry. The study aims to provide experimental evidence that the novel method is effective and has advantages over the conventional method. The experiment was carried out using a singlet as the unit-under-test with visible deflectometry composed of a camera and a monitor. In the conventional approach, the camera is moved to multiple field points to measure transmitted wavefront aberrations. For the accurate measurement of the aberrations, accurate knowledge of the camera positions is desired for conventional deflectometry. In the novel approach, the camera is fixed at an on-axis field point, while the monitor is moved to at least two positions in the longitudinal direction. Even if the camera is fixed, the new method can derive the linear behavior of aberrations over the field as it measures pupil mapping error and slope mapping error instead of wavefront error directly. Also, it is insensitive to positional errors in the monitor. This is made possible by discovering the complementary aspects of the sine condition test and deflectometry. We emphasize that the new alignment method is not performing two independent tests separately. The test can be done via one test setup requiring a camera and a monitor equivalent to a deflectometry system. The results demonstrate the benefits of the novel alignment method, which eliminates the need for accurate control of the test instrument movement during the alignment process.

In this paper, we demonstrate two designs of low-cost mirror scanners. The main structures are 3D-printed with PLA (polylactic acid) as the material. A 20 mm  20 mm aluminum-coated silicon chip is attached on the top of the 3Dprinted piece and functions as the mirror. Miniature permanent magnets are installed on the back of the mirror, and the mirror can then be actuated by electromagnets. The umbrella-like scanner achieves resonant optical scan ranges of 4.8 and 4.5 degrees in two orthogonal directions, respectively. On the other hand, the X-shape scanner reaches 12.2 and 4.6 degrees (optical) for the x- and y-scans at the corresponding resonant frequencies (103 Hz and 128 Hz), respectively.

The Jupiter environment presents many unique challenges to the optomechanical design of the Europa Imaging System (EIS) Wide Angle Camera (WAC) for NASA’s Europa Clipper Mission. EIS is designed to address Europa Clipper’s highpriority geology, composition, ice shell and ocean science objectives. The WAC is an F/5.75, 46-mm focal length 8-lens refractive telescope with a 48° x 24° FOV and a 218-μrad IFOV, resulting in 11-m pixel scale from 50-km altitude over a 44-km-wide swath. The 4096 x 2048 x 10 μm sensor and 6-color stripe spectral filters enable two imaging modes, framing for global mapping and plume searches, and time delay integration for color imaging (400-1050 nm) with three-line stereo topography. This paper describes the design, material selection, integration, and testing of the EIS WAC to survive the Jovian environment leading up to Europa Clipper integration in Summer 2022.

Previous work has demonstrated the feasibility of using ultrafast laser generated stress to deform fused silica substrates to a desired flatness in a process called ultrafast laser stress figuring (ULSF). Materials other than fused silica may offer superior optomechanical properties that are more suited to certain applications or environments. In this work we explore the stress generated by focused ultrafast laser pulses in several common optical materials: Corning Ultra Low Expansion (ULE) glass, Corning Eagle XG glass, fused silica, and sapphire. Using a laser polarization state perpendicular to the writing direction, we find that the laser induced stress depends on the energy of the ultrafast laser pulses, the distance between two adjacent focused pulses, and the repetition rate at which the pulses are delivered into the material. Each material explored showcases unique dependence on these parameters. The results from this investigation will be used to characterize the potential equivalent material removal rates that would be theoretically achievable by ultrafast laser stress figuring for commercially available sapphire and Eagle XG substrates.

The alignment of precision optical assemblies can be time-consuming and labor-intensive, particularly for ap- plications that need to maintain performance through harsh environments. To achieve a rugged design, op- tomechanical elements are frequently aligned and locked in place with shims that are ground and lapped to extremely tight tolerances. The grinding and lapping process can take days, weeks, or even months in select instances that require extremely tight tolerances for alignment. In this work, we present an alternative actua- tion and lock approach that can shorten alignment times without sacrificing ruggedness or alignment resolution. The faster optical alignment is achieved with an Adjustable, Re-lockable, Ruggedized, and Kinematic (ARRK) mount principle. Select experiments demonstrate the working principle of an ARRK mount, evaluate ease-of-use, and demonstrate stability through a random vibration environment. Our results suggest ARRK mounting as a promising approach for fast, robust optical mounting in applications that need to withstand vibration.

This study is to design glass windows for soft X-ray mirror cleaning by UV light. The soft X-ray mirror will operate in the synchrotron radiation light source for several months, and the mirror surface will be covered with a carbon layer. Soft X-ray mirror cleaning uses UV light on the mirror surface and adds a little oxygen to the vacuum chamber. The carbon will be cleaned by UV light and oxygen. Thus, mirror cleaning is needed to design narrow and long windows to let the UV light arrive at the mirror. In the mirror mount in the original design, the bolt joint force causes the mirror to break. Therefore, this study cut the mount's four corners to absorb the bolt joint deformation, not to transfer to the window. A 2 mm diameter tin wire seals the window mount and successfully compensating the bolt joint forces caused the vacuum chamber and window mount deformation. The simulation result shows that this design can make success decline by 28% maximum deformation. The window mounting test is also sealing the achieve 5.5 E-11 mbar l/s.

Polygon mirror scanners are widely considered to be a vital factor in high-power laser scanners because of their rapid speed and large scanning area. However, one limitation of the polygon mirror design is that back reflection of the laser damages the laser source. This work will perform a detailed analysis of the scanner head, leading to a design that avoids back reflection. This design produces a scan area with a scanning length of up to 305 mm and a width of 6.6 mm. Moreover, the scanning speed can reach 30.5 m/s. Finally, a paint stripping experiment demonstrated the efficacy of the polygon mirror for potential use in commercial applications.

The development of a new optical device often faces the same challenges, more specifically at the concept validation level where their development risks are very high. It commonly leads to a laboratory proof-of-concept to test the principle usually built with commercially available off-the-shelf components with high degree of adjustments. The level of robustness, the compactness, and the portability of the device are limited by these adjustable mounts. A breadboard prototype is then developed integrating more custom mounts, but it may require substantial optomechanical effort to converge on an improved version. QuickPOZ, a new generation of mounts, has been developed to fill the gap between the concept idea and the first prototype runs. These standard mounts and breadboards are an easy way to build optical breadboards quickly and accurately robust. They can be used in the development process as soon as the proof-of-concept validation, and up to small run prototyping to test the market. These mounts combine the QuickCTR-edge technology to self-center optics and their mounts, with a high robustness level. QuickPOZ mount’s optical performance results are presented and discussed over a wide operating temperature range between -40°C up to 50°C.

We compare the optical performance, alignment sensitivity, and thermal stability of a Non-Uniform Rational B-Spline (NURBS) freeform telescope design to two more conventional design forms with the goal of facilitating acceptance of this new optical surface for aerospace applications. We present the designs of three three-mirror anastigmat (TMA) wide field (4°) telescopes with identical first order optical design parameters. These TMAs consist of a conventional design using off-axis aspheric mirrors, a freeform design using off-axis Zernike polynomial surfaces, and a freeform design using NURBS surfaces. Of the three, the NURBS design gives the best image quality and lowest geometrical design residual. The three designs have similar misalignment sensitivities and sensitivity to thermal soaks, countering a common misconception that freeform designs are more sensitive to misalignment than conventional designs.

We investigated cross-fringe phasing sensor for the piston and tip-tilt correction of multi-aperture optical systems. By careful design of the pupil slit mask pattern, interference fringes generated by aperture segments are multiplexed in a single diffraction pattern and demultiplexed by spatial filtering. Numerical simulation shows that this multiplex-demultiplexing scheme is applicable for measuring high-dynamic range piston error and precise tip-tilt error simultaneously. The feature suggests that this technique is robust and applicable for future satellite missions with a multi-aperture system.

The Structured Laser Beam (SLB) is a pseudo-non-diffracting laser beam that shares many characteristics with a Bessel beam. However, it can theoretically propagate over an unlimited distance while maintaining an extremely low inner core divergence of only 0.01 mrad. This makes it a promising candidate for precise longdistance alignment applications such as the alignment of particle accelerator components at CERN. In this work, a novel method to detect low-order wavefront aberrations induced by an SLB generator, that can affect the referential straightness of the beam, is presented. Our approach is based on the analysis of a single intensity distribution of an SLB. The coefficients of the Zernike polynomials are estimated using artificial intelligence before least-squares fitting is used to refine the result. This approach ensures that the fitting avoids local minima. This method provides a novel way to analyze the optical aberrations induced by the SLB generator and estimate the quality of the beam. Furthermore, it has the potential to be used for the alignment of complex lens systems, where an SLB can serve as a reference optical axis to which the other optical elements can be aligned.

Optical designers are being asked to create designs that will perform over larger ranges of environmental conditions. This trend applies to compact aspheric lenses as well as other lens types. One potential athermalization strategy for compact aspheric lens design is to include at least one glass element in the mix of elements in the design. This is a well-known technique, but it leaves the lens designer with some questions. One might ask, are there some rules of thumb for using a glass element? We discuss that question in this paper and provide some potentially helpful guidance.

Threaded mounts are one of the most common interfaces between optical systems and commercial-off-the-shelf cameras. Popular examples include the established C-mount, as well as the newer TFL-mount which accommodates for larger sensor formats such as the APS-C detector. In all cases, the thread is used to adjust for focus by clocking the optical system with respect to a fixed camera assembly or vice versa. For this reason, the alignment between the datum axis of the optical system and the array detector plane inside the camera depends on both the allowances and tolerances of the thread interface, and on the manufacturing tolerances of the mount components. To highlight how the stack up of these tolerances can affect image quality of an optical system, we first perform an inverse sensitivity analysis to determine the detector alignment specification as a function of system F/#, field of view, and chief ray angle. We then calculate the misalignment contributions of the thread between the optical system and the lock ring that sets the camera axial position for best focus. This optomechanical analysis allows us to determine if thread mounts are appropriate for the specifications of the optical system under consideration and to specify the tolerances of the thread interface when this is the case.

The Giant Magellan Telescope will be a 25.4-m visible and infrared telescope at Las Campanas Observatory in Chile. The initial alignment of this doubly segmented telescope will be challenging, particularly when mapping coordinate systems together. To ease the complications of alignment, a laser tracker network has been developed to accurately determine the coordinate systems of subsystems and tie them into a reference coordinate system to ensure a successful and efficient first photons phase of the telescope. This paper will discuss the simulations that have been run to date of this laser tracker network and our general initial alignment strategy.

We suggest a novel monolithic design for metal mirror mounting to reduce the surface deformation by the assembly stress. The mirror has a duplex layer to suppress the stress transport and a triangle ear structure for assembly. The reflective surface is on a front layer and a back layer consists of the triangle ears. We perform the structural analysis and manufacture the mirrors and measure the z-sag via UA3P to verify the effectiveness of the design. Comparing the two results, we find out that the design can reduce surface deformation by external stress as we expect.

Ground-based astronomical instruments have mass limits to ensure they can operate safely and accurately. Reducing the mass of optomechanical structures relieves mass budget for other components, improving the instrument’s performance. Many industries have adopted generative design (GD) and additive manufacturing (AM; 3D printing) to produce lightweight components. This is yet to be implemented in ground-based astronomical instrumentation; this paper aims to provide insight into the advantages and limitations of this approach. The project studied the Extremely Large Telescope (ELT) Mid-infrared Imager and Spectrograph (METIS) threemirror anastigmat (TMA); comparing the conventional, subtractive machined design with GD-AM designs. The TMA was selected due to its bespoke geometry constrained by an optical path, a conventional design which did not consider mass reduction, the size of the part (615mm × 530mm × 525mm) that necessitated a study of different AM methods, and the operational environment (70K & 10−6 Pa). The study created mass-optimised designs of the TMA using topology optimisation and field-driven design. The performance of these designs was analysed using finite element analysis and optical ray tracing. It was found that GD-AM designs pass the required optical, structural and modal requirements, with a greater than 30% weight reduction when compared to the conventional design. The study investigated wire arc additive manufacturing (WAAM), a viable method of manufacturing components of the TMA’s size. To commence the validation of WAAM for cryogenic environments, samples of WAAM aluminium 5356 were created and studied. The internal and external dimensions of two samples were investigated using X-ray computed tomography and the outgassing rate of two sets of three samples were evaluated to quantify the difference between machined and as-built samples.

Ultrafast Laser Stress Figuring (ULSF) is a new process for shaping thin optics. The stability of ULSF generated stress, at room temperature and at elevated temperatures, is unknown. Exposing laser-figured samples to elevated temperature acts as a proxy for testing long-term stability of ultrafast laser-generated stress. We conducted an isochronal annealing study up to 500 °C, on fused silica wafers, figured with single-Zernike deformation components, measuring their shape after each cycle. We track changes in those deformations, demonstrating that figured samples show small amounts of relaxation under increasing temperature, beginning around 200-300 °C. This suggests ULSF produces stable mirror figuring only up to ~200 °C temperatures. Combined with previous measurements, this suggests ULSF may exhibit long-term stability at room-temperature.

Composites with high elastic modulus, high specific stiffness, and ultra-low coefficient of thermal expansion (ppb/K-level) will likely be necessary for future ultra-stable optomechanical systems, such as space telescopes for high-contrast imaging. Carbon fiber reinforced polymers (CFRP) offer many favorable properties but suffer from instability due to moisture absorption and creep, and currently cannot cost-effectively achieve the 1-5 ppb/K coefficient of thermal expansion (CTE) required. New materials are desired with high elastic modulus, high specific stiffness, and ppb/K-level CTE. This paper presents three composite designs whose CTE is tunable by ablating material from one or more layers after fabrication and CTE metrology. Each composite design contains sapphire facesheets and a core material of fused silica, silicon carbide or Allvar® to achieve zero- and tunable-CTE. Finite element models reveal that each composite design exhibits CTE tunability of 200-800 ppb/K. The specific stiffness of the Sapphire-Allvar® composite design is around 60 GPa/(g/cc), whereas the others have lower specific stiffness < 20 GPa/(g/cc). These designs demonstrate the principle of tunable low- CTE materials that may have promise for future ultra-stable telescopes.

A catadioptric design has been drawn to be used for semiconductor defect inspection in deep UV, which consists of nine lenses and mirrors. The numerical aperture was 0.8 and the whole length was 95 mm. The optical performances of the system were analyzed and the sensitivities of each component were investigated. Two lenses were found most sensitive and those lenses would be applied for the compensator when the system is going to be assembled. In this paper, the analysis results of the catadioptric system are presented, and the assembly plan is discussed.