This PDF file contains the front matter associated with SPIE Proceedings Volume 13133, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Measuring the quality of alignment of an assembled compound lens is often necessary. This raises the question of what axis to use as a reference axis for this measurement. We suggest that the reference axis should be the optical axis of the assembled system and that this axis is unique for each assembly.

White balance calibration ensures colorimeter measurement accuracy on a display, but changing of display luminance can cause spectral drift, leading to the need of recalibration. Mimicking a micro-LED or OLED panel and using a colorimeter, we compare color error sources, finding spectral drifts to be a major contributor to the error. This finding highlights the need for high-speed recalibration in mass production.

For a long time robotic arms have proven to be extremely useful tools in production and have started to find more applications in general metrology. Installing a non-contact measurement probe to the end of a robotic arm greatly increases the number of useful measurement configurations, making possible previously impossible measurements, such as scanning the anterior and posterior side of a sample with the same probe and without remounting. Using a robotic arm in metrology applications brings to light movement issues which production use might not ever see. Understanding these issues helps inform the usefulness and accuracy of robotic metrology scans. Separating movement errors from measurement results requires a careful mapping of robotic movements. Comparing programmed robotic movements to a known precision surface provides a method for quantifying movement errors through a scan. We measured the airgap between a low coherence interferometry (LCI) probe mounted to the robotic arm and a precision optical flat. We programmed different movement paths of a 6-axis 946 mm reach robotic arm. The movements ranged from linear to a smooth arcing curvature at near, mid, and far reach locations. Deviations ranged from sub-micron to micron levels from the ideal motion paths. Mapping the measurement locations with minimal positioning errors is essential for our goal of accurate metrology results.

In the long-running SPIE short course “Introduction to Optical Alignment Techniques,” a discussion is included that details the mounting process that was developed to aid in the manufacture, assembly, and alignment of a complex optical relay assembly. The assembly operated over a broad spectral range, and it was deemed necessary to use an all-reflective system to pass the light from the collecting telescope to the imaging subassembly. There could be no obscurations, and a set of five off-axis parabolas (OAPs) were chosen to relay the light over the 57-foot optical path distance. Aligning one OAP can be challenging for most engineers, but aligning five of them was thought to be nearly impossible. An innovative technique was developed that aided in that alignment process, and it was carried over to the accurate fabrication of the OAPs as well as the mounting concepts for holding the OAPs in their correct positions. These same techniques can also be integrated with other conic mirrors which have stigmatic focal points, and with thought, even free-form mirrors. Examples will be given that detail the process for these other mirrors.

Four large zoom lens systems are currently being built for x-ray sources. Radiographic imaging needs require 270 mm x 270 mm square scintillators and the capability to use both 92 x 92 mm and 62 x 62 mm CCD cameras. Each zoom lens system incorporates 11 elements and is designed to be almost telecentric in both image and object space. Each zoom lens system images a thick scintillator emitting light peaking at 435 nm, so special glass types are required for the lens elements. Much larger elliptical pellicles are needed to deflect the scintillator light out of the x-ray path into the zoom lens system.

The optical axis of the imaging system must be colinear with the x-ray axis. Two scintillators are positioned on each of two x-ray axes, for a total of four scintillators and four zoom lens systems. An optional configuration will be shown, enabling two lens systems imaging opposite sides of a single scintillator, for a total of four lenses and two scintillators. Although this configuration has advantages, it could suffer from crosstalk. Care must be taken to analyze the anti-reflection coatings applied to all the elements in the imaging chain, including the CCD array and its vacuum window.

Design of two-color counter-propagating laser alignment systems will be demonstrated, which shows how the best possible resolution can be achieved. Flip mirrors are used to allow six alignment lasers to have access to the optical axis. Monitoring all retro-reflections at two different wavelengths simplify optical alignment. The evolution of our x-ray radiographic systems over the last two decades will be discussed.

Flat-field correction (FFC) is essential for addressing relative illuminance roll-off in optical imaging systems, a calibration process that requires capturing an image of a uniform light source. In imaging systems capable of mimicking or measuring SPH, CYL, AXIS, such as those used for eye prescriptions, the number of images required to collect for FFC increases with each lens adjustment. We propose a numerical method that uses a few core images to synthesize FFC images for various configurations, reducing data requirements substantially. This method was validated on two imaging systems with differing optical alignment quality, achieving relative illuminance falloff of less than 2% with only 5% the amount of the original data.

The adoption of freeform optics by designers and manufacturers has increased in recent years. With the increase of flexibility, a freeform surface can bring a system, it also brings more sensitivities. To effectively control these sensitivities during integration, the tolerancing needs to incorporate the limits of the metrology device for the tolerance operand under test. Understanding a vendor’s manufacturing and metrology capabilities is critical to designing and tolerancing a freeform surface that uses its physical features to aid in integration. Interfacing with a vendor early in the design process may improve manufacturing timelines due to the alignment of the freeform definition with the available metrology. Favorable freeform definitions will be reviewed along with tolerancing and specification recommendations.

Recent advances in a unique, pattern-recognition, electronic autocollimator called the Ultra-stable Wide Field of Regard Electronic Autocollimator (UWFOREA, pronounced “euphoria”) engineered at Leviton Metrology Solutions (LMS) in Boulder, CO are presented. A measurement system using this autocollimator called the Inter-target Differential Electronic Autocollimator (IDEA) is capable of making differential angular measurements between a target flat and a flat base reference mirror with 30 nrad accuracy. This measurement approach largely nullifies environmental influences on angle measurements and makes it possible to test payloads at extreme temperatures in thermal vacuum environments with exquisite accuracy. For shorter focal length versions of UWFOREA, the system can measure over an astounding and unprecedented +/-10° angular range with 1 μrad rms calibrated accuracy. The internal stability of UWFOREA has been demonstrated to be as low as 5 nrad rms with only modest temperature control of about 1 C. Select UWFOREA and IDEA data for critical calibrations for a number of space-flight missions and GSE systems are presented.

The AWE AMTM is a wide field-of-view (WFOV) infrared imaging radiometer designed for use in measuring the P1(2) and P1(4) emission lines of the earths OH layer. From these measurements, the atmospheric temperature is determined and finally images of gravity waves will be produced as the AWE field of view transverses the OH layer. Designed, built, and characterized by Utah State University (USU) and its Space Dynamics Laboratory (SDL), the sensor has been externally mounted to the International Space Station (ISS) looking nadir. Images will be collected and analyzed for a minimum of two years. The optical sensor assembly, also known as the Optomechanical Assembly (OMA), consists of four identical imaging telescopes, each comprised of a fisheye optical assembly, a field lens, and a re-imager optical assembly. The four telescopes share a common filter wheel with four narrow band filters. The 16 lenses in each telescope are coaligned and bonded into five aluminum lens barrels. The detectors were aligned, supported, and thermally compensated via a titanium thermal compensator and custom focus shim attached to the aft end of each telescope. Following assembly, the OMA was environmentally tested including EMI/EMC, vibration, and thermal cycling. Prior to and following each environmental test the point response function of each telescope was measured and compared to verify no degradation of performance had occurred. This paper will present an overview of the optical design, tolerance analysis, lens alignment, detector focusing, and image quality verification testing in vacuum of the OMA.

This paper will present the newly developed high-power laser calibration system and alignment at the National Metrology Institute Thailand (NIMT). The system is composed of a high stability, high-power fiber laser with a wavelength of 1080 nm, as a laser source for calibration. Due to this wavelength is not visible to human eyes, the laser is equipped with a built-in red alignment laser and an automatic shutter that can be used for the routine alignment of the whole optical path. The method of calibration is in direct comparison using 2 beam samplers and 2 monitor power meters, for better accuracy. Two beam expanders are used to adjust the laser beam diameter. The reference power meter for calibration is a thermopile sensor. The optical characterization results of the reference power meter such as power non-linearity and detector surface non-uniformity, to be performed at the National Metrology Institute of Germany (PTB), will also be present.

The TeraByte InfraRed Delivery (TBIRD) system is a 3U payload on a 6U CubeSat launched in May 2022 which has now demonstrated space to ground links of >1 Terabyte (TB) per pass at a max data rate of 200Gbps. As a CubeSat mission, the development of the TBIRD payload was focused on low SWaP and a “rapid prototyping” approach which accepted higher risks to accelerate the schedule and reduce costs. The optomechanical design process followed standard in-house processes to develop a system that would be robust to LEO environmental loads, with a focus on the stability of the transmit (Tx) and receive (Rx) channel performance metrics. The driving requirement of maintaining 20μrad pointing error between the TX and Rx channels forced specific attention to thermal and mechanical load changes over operational conditions, which drove major design decisions. This paper describes some of engineering challenges overcome and approaches used to make TBIRD a successful program, as well as some of the tradeoffs of rapid prototyping precision optical payloads. TBIRD successfully met and exceeded the total downlink requirements listed above, with a bandwidth of 200Gbps and a total downlink of 4.8TB of information in a single pass.

POET is a proposed Canadian Microsatellite mission to detect new, potentially habitable, rocky planets transiting low-mass stars, and to characterize the atmospheres of known transitioning extrasolar planets. The allreflective telescope offers simultaneous imaging in the u-band (300-400 nm), VNIR (400-900 nm) and SWIR (900-1700 nm) through a 20 cm aperture. The optical telescope assembly (OTA) has been designed and build with support from the Space Technology Development Program (STDP) of the Canadian Space Agency. The prototype underwent complete integration and optical properties testing including ensquared energy, Modulation Transfer Function, distortion, and Effective Focal Length measurement. Results show that the design is compliant with expected performances at ambient temperature. A Thermal-Vacuum Chamber campaign over the range of operation temperature has been designed to verify the OTA’s performance from -20 °C to 20°C. This enables the investigation of image quality stability in a sub-set of environmental conditions, increasing the OTA’s Technology Readiness Level. POET is a collaboration between Bishop’s University, Western University, ABB and SFL-UTIAS.

The Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite is a strategic climate continuity mission that will answer new and emerging advanced science questions related to Earth’s changing climate. These science goals are accomplished via PACE’s main optical instrument, a sophisticated spectrograph, the Ocean Color Instrument (OCI) consisting of UV/VIS and VIS/NIR channels each complete with a dichroic, grating, and detector. We will overview the characterization methods used for each component, with respect to its metrology targets, and further discuss how baseline characterization served as a proxy when lines of sight to the optical components’ boresights were lost in later integration steps.

Multi-aperture optical imagers intrigue attention for high-resolution Earth observation optics. One crucial technology in building these optical systems is constructing an on-orbit final alignment method of piston-tip-tilt errors between sub-apertures. We propose using image-based alignment based on the stochastic parallel gradient descent (SPGD) algorithm. We developed a tabletop multi-aperture imaging setup with 37 hexagonal-shaped mirror segments. The piston-tip-tilt state of each segment was controlled by changing the applied voltage to each microelectromechanical systems actuator that supports the mirror segments. The observation targets were a pinhole and extended scenes projected on a display. The experimental results demonstrated the successful aperture synthesis of 37 mirror segments using static and time-varying extended scenes.

Precise alignment in Korsch telescopes is crucial due to the complex design and intricate aspheric primary mirror. Conventional alignment methods using wavefront sensors often encounter difficulties with obstructions from secondary components, leading to potential inaccuracies and suboptimal solutions. This study introduces a novel alignment methodology utilizing laser radar technology and an integrated metrology system to capture the three-dimensional surface profile of the aspheric primary mirror and other components. The methodology includes strategic placement of multiple laser radars and additional laser trackers and autocollimators for comprehensive measurement and continuous monitoring. This approach significantly reduces alignment errors, enhances precision, and accelerates the alignment process. The results show that deviations of main mirrors under varying gravity conditions closely match finite element analysis, validating the robustness of the alignment in zero-gravity environments. The ability to detect and compensate for gravitational effects ensures optimal performance, highlighting the effectiveness of the proposed methodology. This research presents a significant advancement in optical engineering, providing a reliable and efficient alignment technique for complex optical systems.

In this paper, we propose a method for rapid calibration of long effective focal length collimators by the Ronchi test. Long effective focal length collimators were often used to calibrate remote sensing optical payloads or telescopes. In order to accurately verify optical system’s collimation, the effective focal length of the collimator must be at least three times longer than the optical system under test. Traditionally, people usually used interferometer to calibrate collimator. However, this method could accurately detect the collimation of the optical system, but the inspection process was quite complex and required a high-precision 6-axis moving platform to recode the interferometer position. Therefore, we propose a method for rapid calibration of long effective focal length collimators by the Ronchi test. The Ronchi test module was composed of a light source, a Ronchi ruling and a camera. We would use the module to verify the alignment of an optical system with a focal length of 10,500mm and a f-number of approximately 14.3. If the distance between the primary mirror and the secondary mirror would be the same as the ideal optical path, the position of the focal plane didn't change. By measuring changes in focal plane position, collimation could be quickly confirmed and adjusted. According to experiment results, the measurement error of the focal plane of this module is approximately ± 55 um. The collimator of emission angle error less than 1.75E-4 mrad. Form the above experiment results, the module could perform collimation verification at lower cost and faster speed. In the future, we could further reduce the measurement error by adding multi-wavelength light sources, gratings of different period frequencies and analyzing various interference fringe characteristics.

This paper proposes a high-precision collimator calibration method based on the principle of the vernier caliper. Collimators are crucial in the development phase of satellite telescopes, as they generate parallel light beams to adjust the focal plane of the satellite optical system, ensuring that satellites can accurately target and maintain optimal operational performance in orbit. Traditionally, laser interferometry is used to calibrate collimators. Although laser interferometry provides high-precision calibration, it is costly and time-consuming, requiring a precise five-axis motion platform to record the coordinates of the interferometer at specific focal points. Therefore, we propose a method using composite periodic patterns to enhance the accuracy of collimator calibration. We utilize an optical imaging system composed of a lens with an effective focal length of 1000 mm and an image sensor with a pixel size of 3.45 micrometers to calibrate a collimator with a focal length of 10500 mm. By analyzing the periodic patterns captured at different aperture positions of the collimator, we achieve sub-pixel level positioning accuracy. This method improves the measurement accuracy of the collimator, providing a low-cost yet highly accurate calibration solution.

The design verification phase of the FORMOSAT-8 remote sensing satellites program's telescope proto-flight model has been successfully passed the green light, paving the way for the implementation of the telescope as the payload for the multi-satellite remote sensing constellation of FORMOSAT-8, comprising FORMOSAT-8A, FORMOSAT-8B, FORMOSAT-8C, FORMOSAT-8D, FORMOSAT-8E, and FORMOSAT-8F (collectively referred to as FORMOSAT-8X) satellites. This paper presents a comprehensive report on the optical design methodology and the lens centering alignment performance of the corrector lens within the FORMOSAT-8 remote sensing satellites program.