In this paper we investigate coded apertures as a function of mask damage, cross talk (on the focal plane arrays), and combinations of the two. We apply a Monte Carlo simulation to extract the probability of the scene reconstruction vs SNR as a performance metric. In addition we calculate the mean time between failures of the system as function damage to the mask.
Coded aperture imaging technology have been utilized [1] for imaging in various space missions primary associated
with X-Ray and Gamma ray sources. The need to extend the coded aperture technique into Visible/IR is pushing the
technology and so geometrical features become smaller [2,3]. As the geometrical feature become smaller, second
order effect such as diffraction become noticeable. The effects are typically isolated in order to improve Signal-to-
Noise Ratio (SNR). In this paper we are exploiting diffraction and interference to use as a coding approach. We
propose a coded aperture transmitter/receiver system capable of hiding information (bits) inside the diffraction nulls.
In designing optical systems in the EO/IR wavelength region for conventional lens are most common and
efficient when low F# and large field of view is desired. Conventional lenses are efficient in meeting
optical response but come at a cost in size and weight and often are complex in nature (aberrations). In
this paper we discuss alternatives to conventional lenses. We examine diffractive optics (DO), and
explore resonating and diffractive periodic metalo-dielectric structures as an alternative lensing. An
oscillator model is employed to interpret these structures, wavefront bending and a design approach is
provided.
Photonic MEMS technology as it pertains to adaptive coded aperture sensing is an emerging technology offering an
increase to imaging performance compared to a fixed system in the EO/IR wavelength region. In this paper we address
the effects of potential manufacturing yield and defects. A 1-d first order optical model is developed in an attempt to
correlate the optical/system performance to the manufacturing defects and yield output. The imager is found to be
extremely robust to both random and correlated failures in the coded aperture, so long as the aperture code is adapted to
the aperture failures.
A new calorimetric absolute power meter has been developed for THz radiation. This broad band THz power meter measures average power at ambient temperature and pressure, does not use a window, and is insensitive to polarization and time structure of THz radiation. The operation of the power meter is based on the calorimetric method: in order to determine the power of a beam of THz radiation, the beam is used to illuminate a highly absorbing surface with known BRDF characteristics until a stable temperature is reached. The power in the incident beam can then be determined by measuring the electric power needed to cause the sample temperature rise. The new power meter was used with laser calorimetry to measure the absorptivity, and thus the emissivity, of aluminum-coated silicon carbide mirror samples produced during the coating qualification run of the Herschel Space Observatory telescope to be launched by the European Space Agency in 2007. The samples were measured at 77 Kelvin to simulate the operating temperature of the telescope in its planned orbit around the second Lagrangian point, L2, of the Earth-Sun system. The absorptivity of both clean and dust-contaminated samples was measured at 70, 118, 184 and 496 mm and found to be in the range 0.2 - 0.8%.
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