THz Imaging Compressive sensing Hadamard spectroscopy THz Laser DMD Hadamard matrices Experimental model v1.0 Experimental model v2.0 Experimental model v3.0
Experimental model of Hadamard spectroscopy, v 1.0
The experimental model of THz Hadamard spectroscopy, shown in the next images, encompasses the following components:
  • Edinburgh FIR 100 laser as the THz source, operated on the 118.83μm (output power = 150mW), 133.1μm (1mW) or 163μm (36mW) wavelength
  • off-axis parabolic mirrors (from copper and coated with gold), with the reflected focal length f = 250mm
  • dispersive element:
    1. reflective blaze diffraction grating
    2. transmission diffraction grating
    3. prism
  • DMD
  • detector
  • software
Experimental model of CS imaging, v 1.0
The experimental model of THz CS imaging, shown bellow, encompasses all components in the spectroscopy setup minus the dispersive element.
Optical components
Off-axis parabolic mirrors are made to order by Laser Beam Products, UK. These mirrors are made from copper and coated with a layer of gold. Their reflected focal length is f = 250mm. In the present setup, they are used to focus or collimate THz radiation, as can be seen in the simulations above.

The reflective blazed diffraction grating is made from a block of brass and the ruled side is coated with a thin layer (approx. 50nm) of gold (by RF magnetron sputtering, Varian installation). Two gratings with the pitch of 300μm and 400μm respectively, were designed and realized

Microscope image (profile view) of the 400μm pitch grating (5X). Zeiss Axio Imager microscope
Microscope image (top view) of the 400μm pitch grating (10X). Zeiss Axio Imager microscope
1:1 image of the 300μm and 400μm pitch gratings, side by side. Macro photography
Scale of the two gratings (left: 300μm pitch, right: 400μm pitch).
The second dispersive element we tested was a transmission grating, made from a brass frame and a 200μm thick wire wrapped around the frame. The resulting grating pitch is 400μm.

The third dispersive element we tested was a set of three prisms, made from MD polyethylene with prism angle of 60°, 50°, and 40°.

  1. Some of the CAD models in the setup above are used from GrabCAD community
  2. Other CAD models in the above images are from Thorlabs
∴ Facts
Title: Compressive THz Imaging and Hadamard Spectroscopy for Space Applications
Project No: 17/19.11.2012
Project type: CDI STAR Project
Starting date: Nov 2012
Duration: 36 months
Partners: 2
INFLPR - Coordinator
CEO Space Tech - Partner
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