Systematic design of a well corrected broadband refractive lens system is described. We approach the design solution beginning from an appropriate starting point that is the Lister-Petzval form with two positive groups separated by an airspace. By identifying the limiting aberrations at each phase, additional lens elements such as an image side field flattener and a quasi-concentric meniscus lens are added. We also methodically consider the performance improvement with the conversion of the quasi-concentric meniscus into a bi-aspherical element. The impact of the biaspherical element on aberration correction potential of this lens form, along with glass considerations for effective color correction are detailed.
The development and performance verification of a cooled long wave infrared (LWIR) imager optics for a high resolution 10μμm pitch detector is described for the next generation optronics mast systems (OMS). The optical system features a Field of View (FOV) changing re-imager architecture, offering high definition imagery over a 3x magnification range under harsh environmental and built-in conditions, characteristic of submarine periscope applications. Details concerning optical design philosophy and evolution of the system from low (320x256) to high resolution (1024x768) detectors are discussed. The optical system includes a steerable de-scanner plate that enables motion blur compensation in a fast azimuth scan mode of the system for panoramic image acquisition. A conceptual framework simulates the complete imaging path taking into account a combination of relative illumination, distortion and relative boresight error across the FOV's of the system. Systematic limitations of the achievable optical performance due to metrology assisted alignment processes are analyzed with ray-trace modelling. Optical performance metrics of as-built systems from the OMS family are studied from a predictive modelling perspective to qualitatively understand their dominant error modalities. These are used to recommend actions to maximize achievable as-built optical performance for the system under development.
Within the scope of the FALCON project Mynaric Lasercom GmbH, in collaboration with Facebook Inc., has built two laser terminals for optical communications: One airborne terminal MLT-70-ATG and one optical ground station GS-200. Both terminals are designed to establish communications between the stratosphere and ground. The athermalized design of the MLT-70-ATG, its efficient temperature management system and an optimized dynamic behavior for high-altitude platforms qualify Mynaric’s system to be easily integrated into carriers that fly up to tens of kilometers. The GS-200 achieves and sustains fast and reliable free-space data transfer links between the airborne segment and ground. It is designed for outdoor operations and is mounted on a stationary stable platform. A flight campaign executed by both companies has demonstrated a 10 Gbps bidirectional error-free link between the airborne laser communication terminal and the optical ground station in a representative scenario. The optical link was acquired successfully in a few seconds and both terminals maintained a steady link. Limitations in the line of sight between the communication partners, due to the flight patterns followed by the aircraft, triggered reacquisitions that were handled by the terminals autonomously. Bidirectional data transmission with maximum data throughput has been achieved. Even for strong fluctuation conditions, which were experienced during ground-to-ground tests, the link was error-free thanks to the coding in the Laser Ethernet Transceiver (LET). The LET converts the user data to a proprietary format. The systems could recover successfully outages up to 10 milliseconds. The coding and synchronization schemes have been optimized for overcoming the inherent spurious effects of the free-space optical communication channel.