Imaging system, optical element, and a catheter or endoscope using the same

An imaging system for imaging an internal cavity, comprising:

• an optical element, comprising
• a single optical body having axial extension and radial extension, for receiving an input beam-front which propagates in the axial direction, and deflecting said input beam front into a series of axially spaced annular projections of light, and
• a plurality of beam-deflecting facets, axially and radially separated with respect to one another, with non-beam-deflecting spaces in between, wherein the beam-deflecting facets are arranged along the optical body and configured to intercept and deflect different annular portions of the input beam-front outwards from the optical body, in a radial direction, to thereby generate from the optical element a series of axially separated annular projections of light;
• and
• an image collection means for collecting light reflected from one or more surfaces of the internal cavity,
• wherein the radial extension of the optical body varies along the axial direction,
• wherein the beam-deflecting facets are arranged at axially successive points along a radial periphery of the optical body,
• wherein the beam-deflecting facets partly delimit the radial periphery of the optical body,
• wherein the beam-deflecting facets form stepped portions in the radial periphery,
• wherein each beam-deflecting facet is arranged to deflect light outwards from the element via a corresponding transmission facet positioned at a radially opposite point on the radial periphery, said point positioned along an optical path through the optical body from the beam-deflecting facet,
• wherein each transmission facet partly delimits the radial periphery of the optical body,
• wherein the deflecting facets reflect light by total internal reflection, and
• wherein for each transmission facet, there is provided, at a radially parallel and axially adjacent point along the radial periphery, a corresponding blocking facet, arranged to reflect rays incident from an axial direction, to prevent said rays being transmitted through the corresponding transmission facet.