The International Space Station (ISS) is an unparalleled laboratory for studying colloidal suspensions in microgravity. The first colloidal experiments on the ISS involved passive observation of suspended particles, and current experiments are now capable of observation under controlled environmental conditions; for example, under heating or under externally applied magnetic or electric fields. Here, we describe the design of a holographic optical tweezers (HOT) module for the ISS, with the goal of giving ISS researchers the ability to actively control 3D arrangements of particles, allowing them to initialize and perform repeatable experiments. We discuss the design’s modifications to the basic HOT module hardware to allow for operation in a high-vibration, microgravity environment. We also discuss the module’s planned particle tracking and routing capabilities, which will enable the module to remotely perform pre-programmed colloidal and biological experiments. The HOT module’s capabilities can be expanded or upgraded through software alone, providing a unique platform for optical trapping researchers to test new tweezing beam configurations and routines in microgravity.
Over the last few years, Boulder Nonlinear Systems (BNS) and North Carolina State University (NCSU) have developed
a new beam steering technique that uses a stack of thin liquid crystal polarization gratings (LCPGs) to efficiently and
non-mechanically steer a beam over a large field-of-regard (FOR) in discrete steps. This technology has been
successfully transferred to BNS through an exclusive license agreement, and a facility has been completed to enable
commercial production of these devices. This paper describes the capabilities enabled by both the LCPGs and the
successful transfer of this technology.
Boulder Nonlinear Systems (BNS) has demonstrated a MWIR step and stare imaging system for AFRL that eliminates
the need for turrets and multiple cameras to scale the performance of available thermal imagers. The demonstration
system non-mechanically switches between fields-of-regard in a Hex-7 pattern to achieve 0.1 milliradian resolution
within a 17.5x17.5 degree field-of-regard. The sub-millisecond shutter switching time and polarization independence
maximizes the imaging integration time and sensitivity. The system uses a 1024x1024 (19.5 micron square pixels) InSb
camera with a 4.5 to 5 micron passband filter. Larger area detectors could be used to obtain larger fields-of-view, or the
system could be scaled to a larger pattern of shutter arrays. The system was developed to provide a cost-effective
method of providing night-vision and thermal imaging capabilities for persistent, high-resolution surveillance
applications with sufficient resolution to track mounted and un-mounted threats. The demo hardware was engineered to
enable near-term field and flight testing.
An analog 128 X 128 spatial light modulator (SLM) has been designed and constructed using liquid crystal on silicon technology. This device is loaded with eight-bit grey-level data in 100 microsecond(s) . Its pixel pitch is 40 micrometers giving an array size of 5.12 X 5.12 mm. Low-voltage ferroelectric liquid crystals are used for the electro-optic modulator. These analog materials have 50 microsecond(s) to 100 microsecond(s) switching times, implying a frame rate of approximately 5 kHz. This paper presents results of the analog SLM and discusses modulation enhancements for improving correlator performance.
This paper details a compact two-dimensional optical correlator based on 128 X 128 ferroelectric liquid crystal spatial light modulators in both the image and filter planes. A complete description of this compact correlator is given. The correlator is fully programmable and performs automatic pattern recognition functions at 500 frames per second. Key design parameters and results of performance analysis are presented.
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