This work demonstrates the use of adaptive polymer lenses (APLs) for short-wavelength infrared (SWIR) applications. First, we present a push-button adaptive optical zoom system for variable magnification with a SWIR focal plane array. We then present a push-button, variable divergence, SWIR laser system for pointing and illumination. Last, we outline a system that combines the two: an SWIR adaptive zoom coupled with an APL-enhanced designator/illuminator. The result would allow a user to toggle between different fields of view (magnification), while optimizing illumination (beam divergence) for each field of view. This could be critical for situational awareness and target identification/designation in tactical applications.
For the passed several years, the Naval Research Laboratory (NRL) has
been investigating the use of Carbon Fiber Reinforced Polymer (CFRP)
material in the construction of a telescope assembly including the optical
components. The NRL, Sandia National Laboratories (SNL), and
Composite Mirror Applications, Inc. (CMA) have jointly assembled a
prototype telescope and achieved “first light” images with a CFRP 0.4 m
aperture telescope. CFRP offers several advantages over traditional
materials such as creating structures that are lightweight and low
coefficient of thermal expansion and conductivity. The telescope’s
primary and secondary mirrors are not made from glass, but CFRP, as
well. The entire telescope weighs approximately 10 kg while a typical
telescope of this size would weigh quite a bit more. We present the
achievement of “first light” with this telescope demonstrating the imaging
capabilities of this prototype and the optical surface quality of the mirrors
with images taken during a day’s quiescent periods.
Iris recognition utilizes distinct patterns found in the human iris to perform identification. Image acquisition is a critical first step toward successful operation of iris recognition systems. However, the quality of iris images required by standard iris recognition algorithms puts stringent constraints on the imaging systems, which results in a constrained capture volume. We have incorporated adaptive optical elements to expand the capture volume of a 3-m stand-off iris recognition system.
Thin-shelled composite mirrors have been recently proposed as both deformable
mirrors for aberration correction and as variable radius-of-curvature mirrors for
adaptive optical zoom. The requirements on actuation far surpass those for other
MEMS or micro-machined deformable mirrors. We will discuss recent progress
on developing the actuation for these mirrors, as well as potential applications.
Iris recognition utilizes distinct patterns found in the human iris to perform identification. Image acquisition is a critical
first step towards successful operation of iris recognition systems. However, the quality of iris images required by
standard iris recognition algorithms puts hard constraints on the imaging optical systems which have resulted in
demonstrated systems to date requiring a relatively short subject stand-off distance. In this paper, we study long-range
iris recognition at distances as large as 200 meters, and determine conditions the imaging system must satisfy for
identification at longer stand-off distances.
An all reflective Shack Hartmann style wavefront sensor has been developed using a Sandia National
Laboratory segmented Micro-Electro-Mechanical (MEM) deformable mirror. This wavefront sensor is
presently being explored for use with adaptive optics systems at the Naval Prototype Optical Interferometer
and other experimental adaptive systems within the Naval Research Laboratory. The 61 MEM mirror
segments are constructed in a hexagonal array and each segment can be constructed with either flat or
optically powered surfaces. The later allows each mirror segment to bring its subaperture of light to a focus
on an imaging array, creating an array of spots similar to a Shack Hartmann. Each mirror segment has tip,
tilt and piston functionality to control the position of the focused spot such that measurement of the applied
voltage can be used to drive a deformable mirror. As the system is reflective and each segment is
controllable, this wavefront sensor avoids the light loss associated with refractive optics and has larger
dynamic range than traditional Shack Hartmann wavefront sensors. This wavefront sensor can detect large
magnitude aberrations up to and beyond where the focused spots overlap, due to the ability to dither each
focused spot. Previous publications reported on this novel new technique and the electrical specifications,
while this paper reports on experiments and analysis of the open-loop performance, including repeatability
and linearity measurements. The suitability of using the MEM deformable mirror as a high dynamic range
reflective wavefront sensor will be discussed and compared to current wavefront sensors and future work
will be discussed.
Deployment costs of large aperture systems in space or near-space are directly related to the weight of the system. In
order to minimize the weight of conventional primary mirrors and simultaneously achieve an agile system that is capable
of a wider field-of-view (FOV) and true optical zoom without macroscopic moving parts, we are proposing a
revolutionary alternative to conventional zoom systems where moving lenses/mirrors and gimbals are replaced with
lightweight carbon fiber reinforced polymer (CFRP) variable radius-of-curvature mirrors (VRMs) and MEMS
deformable mirrors (DMs). CFRP and MEMS DMs can provide a variable effective focal length, generating the
flexibility in system magnification that is normally accomplished with mechanical motion. By adjusting the actuation of
the CFRP VRM and MEMS DM in concert, the focal lengths of these adjustable elements, and thus the magnification of
the whole system, can be changed without macroscopic moving parts on a millisecond time scale. In addition, adding
optical tilt and higher order aberration correction will allow us to image off-axis, providing additional flexibility.
Sandia National Laboratories, the Naval Research Laboratory, Narrascape, Inc., and Composite Mirror Applications,
Inc. are at the forefront of active optics research, leading the development of active systems for foveated imaging, active
optical zoom, phase diversity, and actively enhanced multi-spectral imaging. Integrating active elements into an
imaging system can simultaneously reduce the size and weight of the system, while increasing capability and flexibility.
In this paper, we present recent progress in developing active optical (aka nonmechanical) zoom and MEMS based
foveated imaging for active imaging with a focus on the operationally responsive space application.
The development of sensors that are compact, lighter weight, and adaptive is critical for the success of future military initiatives. Space-based systems need the flexibility of a wide FOV for surveillance while simultaneously maintaining high-resolution for threat identification and tracking from a single, nonmechanical imaging system. In order to meet these stringent requirements, the military needs revolutionary alternatives to conventional imaging systems.
We will present recent progress in active optical (aka nonmechanical) zoom for space applications. Active optical zoom uses multiple active optics elements to change the magnification of the imaging system. In order to optically vary the magnification of an imaging system, continuous mechanical zoom systems require multiple optical elements and use fine mechanical motion to precisely adjust the separations between individual or groups of elements. By incorporating active elements into the optical design, we have designed, demonstrated, and patented imaging systems that are capable of variable optical magnification with no macroscopic moving parts.
Liquid crystal spatial light modulators, lenses, and bandpass filters are becoming increasingly capable as material and electronics development continues to improve device performance and reduce fabrication costs. These devices are being utilized in a number of imaging applications in order to improve the performance and flexibility of the system while simultaneously reducing the size and weight compared to a conventional lens. We will present recent progress at Sandia National Laboratories in developing foveated imaging, active optical (aka nonmechanical) zoom, and enhanced multi-spectral imaging systems using liquid crystal devices.
Unique liquid crystal (LC) spatial light modulators (SLM) are being developed for foveated imaging systems that provide wide field-of-view (FOV) coverage (±60° in azimuth and elevation) without requiring gimbals or other mechanical scanners. Recently, a transmissive-SLM- based system operating in the visible (532 nm) has been demonstrated. The LC SLM development is addressing implementation issues through the development of high figure-of-merit (FoM) LC materials and transmissive high-resolution SLMs. Transmissive SLM operation allows the foveated imaging configuration to be very compact using a very simple lens system. The reduction in the size, weight and cost of the imaging optics and in data acquisition/processing hardware makes the foveated approach attractive for small platforms such as unmanned airborne vehicles (UAVs) or missile seekers.
Binary Laser Direct-Write (LDW) raster-scan technology for UV exposure of photosensitive materials has been used for single or multiple-pass exposure applications. Gray-scale LDW can be applied to manufacture of 3-D optical structures, but the system requirements are substantially different, since edge slopes and surface departures must be controlled to within fractions of a wavelength.. In this paper, we explore the differences between binary and gray-scale raster imaging applied to micro-optic fabrication, and compare the system model with a prototype high-speed, gray-scale LDW tool that was developed from a Laser Direct Imaging tool originally designed for binary applications.