Photonics

Glass Molding Makes High-Quality Aspheres Cost Effective

High-resolution digital imaging, low-light-level biomedical devices, and automotive sensing are just a few of today’s hot technologies demanding both low-cost and high-performance optical systems. Critical in this effort is the mid- and high-volume requirement for aspheric optical components. Unfortunately, CNC polishing methods are expensive and take too long to produce each component, which has pushed precision glass molding to the front of asphere manufacturing technologies.

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New Metals, Optics, Tools, and Processes Focus on Satellite Imaging

Lightweight, aspheric, reflective optical designs commonly are designed and built for demanding space-based remote sensing, targeting systems, and aerial reconnaissance. Traditional designs utilizing low expansion optical glasses steadily are giving way to metals such as aluminum, beryllium, and AlBeMet, and ceramics such as silicon carbide. These materials can be produced in extremely lightweight, yet robust and athermalized, designs by virtue of their superior tensile strength, fracture toughness, and the ability to compose support structures and mirrors from identical materials.

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Thermal Light Valve Brings IR Imaging to the Masses

Technology uses MEMS structure with refractive properties sensitive to thermal radiation and reads out signal with inexpensive laser diode and CMOS sensor. RedShift Systems, Waltham, Massachusetts The desire to “see” in complete darkness or through obscurants such as smoke or fog has driven the development and adoption of thermal imaging technology. Thermal imaging is the translation of a scene’s heat signature — the 8-μm to 14-μm or long-wavelength infrared (LWIR) energy an object emits — into a visible image or data that can be interpreted by a computer.

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Optically Driven Deformable Mirrors

There is no wiring on the back sides of these mirrors. NASA’s Jet Propulsion Laboratory, Pasadena, California Optically driven deformable mirrors may eventually supplant electrically driven deformable mirrors in some adaptive-optics and active-optics applications. Traditionally, the mirror facets in electrically driven deformable mirrors are actuated, variously, by means of piezoelectric, electrostrictive, microelectromechanical, liquid-crystal, or thermal devices. At least one such device must be dedicated to each facet, and there must be at least one wire carrying a control or drive signal to the device. If a deformable mirror comprises many (e.g., thousands) of facets, then wiring becomes a major problem for design, and the problem is compounded in cases of piezoelectric or other actuators for which high drive voltages are required. In contrast, in optically driven mirrors, the wiring problem is eliminated.

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Automatic Alignment of Displacement-Measuring Interferometer

Corrections are derived from fluctuations associated with circular dithering of a laser beam. NASA’s Jet Propulsion Laboratory, Pasadena, California A control system strives to maintain the correct alignment of a laser beam in an interferometer dedicated to measuring the displacement or distance between two fiducial corner-cube reflectors. The correct alignment of the laser beam is parallel to the line between the corner points of the corner-cube reflectors: Any deviation from parallelism changes the length of the optical path between the reflectors, thereby introducing a displacement or distance measurement error.

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Even Illumination From Fiber-Optic-Coupled Laser Diodes

Emerging light beams would be shaped by diffractive fiber-optic tips. Marshall Space Flight Center, Alabama A method of equipping fiber-optic-coupled laser diodes to evenly illuminate specified fields of view has been proposed. The essence of the method is to shape the tips of the optical fibers into suitably designed diffractive optical elements. One of the main benefits afforded by the method would be more nearly complete utilization of the available light.

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Excimer Leverages Litho Lessons for kHz Micromachining

Features developed for lithography light sources are creating a mid-tier excimer laser niche. Coherent, Santa Clara, California Ultraviolet lasers currently are used in a very diverse range of industries and applications. This is because their high-energy photons directly can break inter-atomic bonds in many materials, and the short wavelength enables a high degree of spatial resolution (see Figure 1). Amongst ultraviolet lasers, excimers are unique in their ability to deliver a combination of high pulse energy and high average power. Because of these advantages, excimers are used in applications as diverse as ophthalmic corrective procedures, low-temperature silicon annealing for flat-panel displays, drilling inkjet nozzles, and treating the cylinder liners of diesel engines for greener automobile performance.

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