This paper presents a system-level description of the Joint Services Lightweight Standoff Chemical Agent Detector (JSLSCAD). JSLSCAD is a passive Fourier Transform InfraRed (FTIR) based remote sensing system for detecting chemical warfare agents. Unlike predecessor systems, JSLSCAD is capable of operating while on the move to accomplish reconnaissance, surveillance, and contamination avoidance missions. Additionally, the system is designed to meet the needs for application on air and sea as well as ground mobile and fixed site platforms.
The core of the system is a rugged Michelson interferometer with a flexure spring bearing mechanism and bi-directional data acquisition capability. The sensor is interfaced to a small, high performance spatial scanner that provides high-speed, two-axis area coverage. Command, control, and processing electronics have been coupled with real time control software and robust detection/discrimination algorithms. Operator interfaces include local and remote options in addition to interfaces to external communications networks. The modular system design facilitates interfacing to the many platforms targeted for JSLSCAD.
This paper presents the passively aligned Wavesetter (PAWS) locker: a micro-optic subassembly for use as an internal wavelength locker. As the wavelength spacing in dense wavelength division multiplexing (WDM) decreases, the performance demands placed upon source lasers increase. The required wavelength stability has led to the use of external wavelength lockers utilizing air-spaced, thermally stabilized etalons. However, package constraints are forcing the integration of the wavelength locker directly into the laser module. These etalons require active tuning be done during installation of the wavelength locker as well as active temperature control (air-spaced etalons are typically too large for laser packages). A unique locking technique will be introduced that does not require an active alignment or active temperature compensation. Using the principles of phase shifting interferometry, a locking signal is derived without the inherent inflection points present in the signal of an etalon. The theoretical background of PAWS locker will be discussed as well as practical considerations for its implementation. Empirical results will be presented including wavelength accuracy, alignment sensitivity and thermal performance.
Most laser projectors for LADAR systems are limited to small scan angles as they utilize acousto-optic devices, spatial light modulators, or fine-steering mirrors for beam steering. Additionally, the projected beam is usually circular and Gaussian. In order to improve the functionality of such systems, MEMS-based mirrors and diffractive optics may be used. This paper describes Digital Optics Corporation's work in developing and demonstrating a novel LADAR scanning system that incorporates a MEMS scanning mirror coupled with diffractive optical elements in a compact breadboard system. The MedCam MEMS mirror has been demonstrated with a 2D scan mode across large scan angles. The MEMS mirror system is experimentally compared to a Liquid Crystal Spatial Light Modulator based system. The diffractive elements generate spot arrays or other patterns that are more conductive to target detection schemes that an ordinary gaussian beam shape.
Standard laser welding practices are limited by the intensity profile of the beam and spot size. The introduction of Diffractive Optical Elements (DOE) to the welding process allows for new beam shapes that are better suited to the welding process. A particular problem in laser welding is the joining of dissimilar materials. Because these materials have different material properties including different melting temperatures, it is difficult to synchronize the welding process using a single spot. Additionally, significant thermal stresses are introduced by the welding process because of the keyhole weld shape formed by a gaussian beam. By using a power splitting DOE, two spots of unequal intensity distributions may be projected onto each side of the weld joint. This paper discusses the use of DOEs in laser welding and joining of dissimilar materials. Results are presented from the testing of several candidate aerospace materials.
System alignment is often the cost driver in the production of optical system. In order to both miniaturize and reduce production costs, wafer scale integration of active and passive components is required. This integration relies on a host of techniques to align and bond active and passive devices into a monolithic structure. Moreover, this initial packaging is accomplished while the optics and supporting structures are in wafer form, thereby providing parallel fabrication with resultant cost savings. This paper describes the fundamental techniques for producing IMOS from wafer scale substrates. The relative merits of each approach are discussed, along with design concerns for successful application. Two example systems are discussed, each using a different fabrication technique.
Optoelectronic processing provides significant advantages for space applications. These advantages include enhanced processing capability with reduced size, weight and power. Design considerations that are unique to space can have a significant impact on the development schedule. Optoelectronic processors are most efficient at operations that involve correlation, Fourier transforms, or a combination of these functions. Several application areas where these functions are used are presented along with the rationale for using optoelectronics. Two key applications include telecommunications switching and radar processing. Synthetic Aperture Radar (SAR) processing in space is discussed as a specific example.