  We report a simple single-pixel imaging system with a low mean squared error
in the entire terahertz frequency region (3-13 THz) that employs a thin
metallic ring with a series of directly perforated random masks and a subpixel
mask digitization technique. This imaging system produces high pixel resolution
reconstructed images, up to 1200 x 1200 pixels, and imaging area of 32 mm x 32
mm. It can be extended to develop advanced imaging systems in the
near-ultraviolet to terahertz region.
