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Research
Interests
Past Projects
Automatic
sub-pixel registration for a tunable hyperspectral imaging system
Hyperspectral imagery of the surface of the Earth is increasingly being acquired from
aerial platforms. The many bands acquired by typical hyperspectral instruments
are collected either in a push-broom, scanning, or staring fashion. Staring
methods can be used in ground and aerial based applications, and have the
advantage of readily producing coherent images. Staring remote sensing
instruments need some form of co-registration to match band-to-band pixel
locations, because it takes some time for the instrument to acquire images and
save them as the aerial platform moves above the target scene. A well known
method for registration is the Phase Correlation (PC) which may be used to
register images to an accuracy of +/-1
pixel. In this paper we report an enhancement to the PC method that allows for
sub-pixel registration of hyperspectral images. The x-y location at which the
maximum correlation function occurs is fitted with a cubic interpolation to find
the maximum. This method was implemented to recover sub-pixel rotation and
translation accuracy from an airborne hyperspectral imaging instrument, dubbed
the portable hyperspectral tunable imaging system. Results showed that the
approach improves up to 9.5 % of the normalized cross correlation between
wavebands in comparison with the PC method alone.
Interface Development for Real-Time Control of a
Remote Sensing Hyperspectral System
This project was proposed as a senior design project to the Electrical
Engineering Department by the Remote Sensing
(RS) Group from the
U.S. Water Conservation Laboratory in Phoenix,
AZ. A remote/ground sensing package is being updated
to speed up its acquisition rate, (and possibly will be equipped with temperature and humidity
sensors to be used for image calibration). A LabView interface is being
developed to be able to view images from all sensors and modify sensor
parameters. A GPS system
will hopefully be integrated and eventually will be used for autonomous image acquisition,
and waveband-to-waveband registration.
Scene
Statistics Based Calibration of Remote Sensing Instruments
A variety of spaceborne remote sensing instruments
achieve wide-area coverage with only a small number of detectors, by using a
cross-track scanning mechanism and satellite motion to provide extended
coverage. Errors in the detectors' relative calibrations result in stripes
in the images acquired by these instruments. This letter presents a
general approach for equalizing the detector responses, based on scene
statistics. For the case where the detector response functions are
predominantly linear, with a small quadratic component, a complete set of
equations for implementing the statistics-based calibration is also presented.
The resulting algorithm has been tested with application to a few select Earth
scenes from the Moderate Resolution Imaging Spectroradiometer, and the quality
of the resulting calibration functions is discussed. Based on the
mathematical formulation and intuitive reasoning, recommendations are offered
for selecting scenes that are suitable for determining the detectors' relative
calibrations with validity across the full dynamic range of the instrument.
3-D
Hyperspectral Instrument
A novel application of hyperspectral instrumentation
is described here, where a sheet-of-light method, produced by a low power laser
light, is used to compute range measurements, and a hyperspectral instrument is
used to acquire spectral information in the visible and near-infrared range of
the spectrum. This report addresses two problems which in the literature are
generally addressed independently; acquisition and analysis of hyperspectral
images, and acquisition and analysis of range information. The bimodal
instrument described in this report consists of a LCTF-based hyperspectral
system which is used to acquire spectral images in the 450-1100 nm range and a
multi-line laser light used to acquire range measurements of a scene. This
laser light method can be used to acquire fast range measurements as the scene
is partitioned into three sub-ranges therefore reducing the acquisition time by
threefold. The methods used to get calibrated hyperspectral measurements (to
reflectance values) of the proposed 3D hyperspectral instrument, and range
measurements (to mm) are described in this paper. A test case shows the
capabilities of this instrument for producing 3-D hyperspectral imagery of human
skin samples.
Active
optics-based Hyperspectral Image Stabilization
This project was proposed as a senior design project.
The objective of this project is to implement an Active Optics system to
stabilize imagery acquired with a Hyperspectral Imaging instrument. Spectral
images can be acquired by using different instrument configurations. The
instrument at hand consists of a scientific camera coupled with two LCTFs. One
of the LCTFs is responsive in the VIS spectral range which usually is considered
to be between 450 nm - 650 nm, and the other one is responsive in
the NIR range of the spectrum, 700 nm - 1100 nm. The acquisition
process of a hyperspectral image (also referred to as hypercube) consists on
positioning the target object in the FOV. In remote sensing applications (when
the instrument is mounted on an airborne platform) or when the target
object/scene is moving, each spectral image will be shifted with respect to each
other because of this movement. Usually, the images need to be co-registered
and calibrated after the fact so that the data can useful to the image analyst.
The purpose of this project is to use a high frequency active optics system,
like an Fast Steering Mirror (FSM), to implement a real-time registration process.
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