This document describes a new approach for hyperspectral imaging using wavefront division interference. The approach uses a spatial light modulator placed in the exit pupil of an imaging system to divide the wavefront from each object point into two parts with a variable phase delay. As the phase delay is changed, an interferogram is obtained for each wavelength, allowing the spectrum at each point to be determined. The approach converts a general imaging system into a hyperspectral imaging system with only a minor impact on optical performance. A prototype optical system was built to demonstrate this new wavefront division interference approach to hyperspectral imaging.

1. Hyperspectral Imaging Camera usingWavefront
Division Interference (WDI)
ERAN BAHALUL,1
ASAF BRONFELD,1
SHLOMI EPSHTEIN,2
YORAM SABAN,2
AVI
KARSENTY,1
YOEL ARIELI
1,*
1
Jerusalem College of Technology, Havaad Haleumi 21, Jerusalem 9116001, Israel
2
Ben-Gurion University of the Negev, Beer Sheva 8410501, Israel
*Corresponding author: arieli.yoel@gmail.com
Received XX Month XXXX; revised XX Month, XXXX; accepted XX Month XXXX; posted XX Month XXXX (Doc. ID XXXXX); published XX Month XXXX
A new approach for performing hyperspectral imaging is
introduced. The hyperspectral imaging is based on
Fourier transform spectroscopy, where the interference
is performed by wavefront division interference rather
than amplitude division interference. A variable phase
delay between two parts of the wavefront emanating
from each point of an object is created by a spatial light
modulator (SLM) to obtain variable interference
patterns. The SLM is placed in the exit pupil of an imaging
system, thus enabling conversion of a general imaging
optical system into an imaging hyperspectral optical
system. The physical basis of the new approach is
introduced, and an optical apparatus is built.
OCIS codes: (140.3490) Lasers, distributed-feedback; (060.2420) Fibers,
polarization-maintaining; (060.3735) Fiber Bragg gratings; (060.2370)
Fiber optics sensors.
http://dx.doi.org/10.1364/OL.99.099999
A multispectral or hyperspectral imaging system images an object
and provides the emanating light spectrum from each pixel of the
object. The different wavelengths emitted or reflected from the object
characterize the substance of the examined object, and hence, the
different parts that compose the object can be identified. Multispectral
or hyperspectral imaging provides a 3D data cube of information
regarding the object by combining the two-dimensional image of the
object with its spectral data. Hyperspectral imaging is used in several
domains of applications, such as medical science [1] agriculture [2],
defense [3], astronomy and space surveillance [4], detection [5],
geology [6], and earth observation [7]. Moreover, due to the
continuously growing importance of hyperspectral imaging, complete
reference books have already been published [8], as well as
comparativeinternationalreports[9].
Because hyperspectral imaging provides a 3D data cube of
information, despite the imaging sensor being inherently two-
dimensional, a scanning operation is usually adopted to construct the
3D spectral image data cube. Many methods have been developed to
fulfill this requirement. The early methods include spectral scanning (λ
scan)usinganopticalfilterwheel[10],pushbroomscanningalongone
spatial axis (y axis) of a line spectral image (x–λ image), and
interferometer spectral imaging (such as mechanical scanning Fourier
transform (FT) spectrometry[11]and staticFT). There aresomeother
methods using dynamic tunable filters, such as liquid crystal tunable
filter [12] and acousto-optic tunable filter (AOTF) [13], which do not
involve mechanical scanning motion. Those scanning-based
approaches have a relatively long 3D image acquisition time, making
them only suitable for imaging relatively stable stationary objects. For
applications on time-varying objects or moving scenes, approaches for
acquiring spectral image data in a single image snapshot have been
reported, such as computed-tomography imaging spectrometer (CTIS)
[14]andholographicspectralimagingsystem(HSIS)[15].
In this article, we present a new approach for performing
hyperspectral imaging [16]. The hyperspectral imaging is based on
Fourier transform spectroscopy, where the interference is performed
by wavefront division interference (WDI) rather than amplitude
division interference (ADI). This approach enables the conversion of a
general imaging optical system into an imaging hyperspectral optical
system by introducing a thin SLM in any plane in the imaging system.
This addition of the SLM only slightly diminishes the optical
performanceoftheimaging systemandthus does notrequire a special
opticaldesign.
The basic hyperspectral imaging optical system is shown in Fig. 1.
The light from each point of the object is imaged to the image plane to
form the image. On its path, the light's wavefront originated from each
point is divided by the SLM into two parts, with one part of the
wavefront being delayed relative to the other part. The relative phase
delayθbetweenthetwopartsisgivenby:
2π
θ
λ
= Δ (1)
where λ is the wavelength and Δ is the optical path difference (OPD)
betweenthetwopartsofthewavefront.
When the two parts of the wavefront intersect to obtain the imaged
object’s point, they interfere according to the relative phase delay
between them. As the OPD between the two wavefront's parts is
increased progressively, each wavelength in the object’s light oscillates
between destructive and constructive interference states. The integral
intensity of all wavelengths detected by the detector as a function of
the OPD performs the interferogram at a certain object's point.

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ccurate, and a mo
eveloped.
eferences
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Elder, and W. S. El-
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