We have recently constructed and tested a gas cloud imager which demonstrates the rst-ever video-rate detection (15 frames/sec) of gas leaks using an uncooled LWIR detector array. Laboratory and outdoor measurements, taken in collaboration with BP Products North America Inc. and IES Inc., show detection sensitivities comparable to existing cooled systems for detecting hydrocarbon gases. Gases imaged for these experiments include methane, propane, propylene, ethane, ethylene, butane, and iso-butylene, but any gases with absorption features in the LWIR band could potentially be detected, such as sarin and other toxic gases. These results show that practical continuous monitoring of gas leaks with uncooled imaging sensors is now possible.
The snapshot advantage is a large increase in light collection efficiency available to high-dimensional measurement systems that avoid filtering and scanning. After discussing this advantage in the context of imaging spectrometry, where the greatest effort towards developing snapshot systems has been made, we describe the types of measurements where it is applicable. We then generalize it to the larger context of high-dimensional measurements, where the advantage increases geometrically with measurement dimensionality.
The gas cloud imager (GCI) is a passive uncooled multispectral camera capable of unprecedented sensitivity for
analyzing hydrocarbon gas mixtures in a scene. The GCI is currently finishing its final stages of development,
and promises to obtain a 220×220 image of gas concentrations at 30 frames/sec, allowing for real-time display in
a compact instrument without moving parts. We summarize measurement approach and discuss the advantages
of the GCI instrument design against conventional instruments.
This paper presents the Image Mapping Spectrometry a new snapshot hyperspectral imaging platform for variety of
applications. These applications span from remote sensing and surveillance use to life cell microscopy implementations
and medical diagnostics. The IMS replaces the camera in a digital imaging system, allowing one to add parallel spectrum
acquisition capability and to maximize the signal collection (> 80%). As such the IMS allows obtaining full spectral
information in the image scene instantaneously at real time imaging rates. Presented implemention provides 350x350x48
datacube (x,y,λ) and spectral sampling of 2 to 6 nm in visible spectral range but is easily expandable to larger cube
dimensions and other spectral ranges. The operation of the IMS is based on redirecting image zones through the use of a
custom-fabricated optical element known as an image mapper. The image mapper is a complex custom optical
component comprised of high quality, thin mirror facets with unique 2D tilts. These mirror facets reorganize the original
image onto a single large format CCD sensor to create optically "dark" regions between adjacent image lines. The full
spectrum from each image line is subsequently dispersed into the void regions on the CCD camera. This mapping
method provides a one-to-one correspondence between each voxel in the datacube and pixel on the CCD camera
requiring only a simple and fast remapping algorithm. This paper provides fundamentals of IMS operations and
describes an example design. Preliminary imaging results for gas detection acquired at 3 frames / second, for
350x350x48 data cubes are being presented. Real time unmixing of spectral signatures is also being discussed. Finally
paper draws perspective of future directions and system potential for infrared imaging.
Hyperspectral imaging has tremendous potential to detect important molecular biomarkers of early cancer based on their unique spectral signatures. Several drawbacks have limited its use for in vivo screening applications: most notably the poor temporal and spatial resolution, high expense, and low optical throughput of existing hyperspectral imagers. We present the development of a new real-time hyperspectral endoscope (called the image mapping spectroscopy endoscope) based on an image mapping technique capable of addressing these challenges. The parallel high throughput nature of this technique enables the device to operate at frame rates of 5.2 frames per second while collecting a (x, y, λ) datacube of 350 × 350 × 48. We have successfully imaged tissue in vivo, resolving a vasculature pattern of the lower lip while simultaneously detecting oxy-hemoglobin.
A snapshot high-sampling Image Mapping Spectrometer (IMS) is developed for hyperspectral microscopy, measuring
datacube of dimensions 285x285x60 (x, y, λ). Microscopy IMS is designed to work at the Nyquist sampling limit to
realize high resolution imaging. The spatial resolution is ~0.45μm with FOV ~130μm. The spectral working range is
500-700nm with ~8.3nm average spectral resolution. Preliminary tests have been implemented on its imaging
performances.
To reduce the number of invasive tissue biopsies and needle aspirations performed during cancer screenings, endomicroscopes
can be used to image tissue in vivo. However, when optical fiber bundles are used to transmit the image,
the resolution of such systems is limited by undersampling due to the spacing of the bundle's individual fibers for a
given field of view. We propose a method to increase the sampling of an optical biopsy system and thereby improve the
system's resolution. The method involves taking several images, shifting the object and fiber bundle slightly relative to
each other from one image to the next. Multiple shifting patterns were evaluated to determine which provided the
greatest increase in resolution. The shifted images are later realigned and recombined by a custom algorithm. By
combining four shifted images of a USAF resolution target, we were able to measure an improvement in the resolution of
the system from approximately 3.9 μm to 2.2 μm. When tested on cultured cells, a visible increase in detail was
detectable. This technique can provide the basis for improving the diagnostic abilities of optical biopsy systems.
Hyperspectral imaging has tremendous potential to detect important molecular biomarkers of early cancer based on their
unique spectral signatures. Several drawbacks have limited their use for in vivo screening applications: most notably
their poor temporal and spatial resolution, high expense, and low optical throughput. We present the development of a
new real-time hyperspectral endoscope (called the IMS Endoscope) based on an image mapping technique which makes
it capable of addressing these challenges. The parallel, high throughput nature of this technique enables the device to
operate at frame rates of 3-10 fps while collecting a 3D (x, y, λ) datacube of 350 x 350 x 48.
A 7-mm OD, NA = 1 water immersion injection-molded plastic endoscope objective has been fabricated for a laser scanning fiber confocal reflectance microscope (FCRM) system specifically designed for in vivo detection of cervical and oral pre-cancers. Injection-molded optics was selected for the ability to incorporate aspheric surfaces into the optical design and its high volume capabilities. Our goal is high performance disposable endoscope probes. This objective has been built and tested as a stand-alone optical system, a Strehl ratio greater than 0.6 has been obtained. One of the limiting factors of optical performance is believed to be flow-induced birefringence. We have investigated different configurations for birefringence visualization and believe the circular polariscope is most useful for inspection of injection-molded plastic optics. In an effort to decrease birefringence effects, two experiments were conducted. They included: (1) annealing of the optics after fabrication and (2) modifying the injection molding prameters (packing pressures, injection rates, and hold time). While the second technique showed improvement, the annealing process could not improve quality without physically warping the lenses. Therefore, to effectively reduce flow-induced birefringence, molding conditions have to be carefully selected. These parameters are strongly connected to the physical part geometry. Both optical design and fabrication technology have to be considered together to deliver low birefringence while maintaining the required manufacturing tolerances. In this paper we present some of our current results that illustrate how flow-induced birefringence can degrade high performance injection-molded plastic optical systems.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.