Axicon Devices for long depth-of-focus scanning imaging system

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In this project, we investigated the 3D imaging-characteristics of axicon prism and its applicability to long depth-of-focus imaging systems. The progresses we made as follows.1) Fundamental experiments using axicon prismsWe made an axicon prism with the vertical angle of 160 degree, diameter of 10 mm. We observed 0th order Bessel-Beam was generated with the width of 4 mum (at half maximum of the central peak) when a collimated beam was incident on it. The depth on focus was 52 mm. We also studied the beam profile experimentally as well as theoretically for the condition of oblique illumination. As the angle incident on the axicon exceeds 4 degree, off-axial aberration is more dominant in the spot ; the central spot splits into four. From the theoretical analysis as well as computer simulation, we verified that the spot split was made with even-orders of aberration. It was also found that an axicon is stronger against comma-aberration than an ordinary lens.2) Photo-lithography system with an axicon.We built a Photo-lithography system using axicon. With this system, we succeeded to draw grooves of 1.0 mum width and 1.5 mm depth on photoresist.3) Fabrication of Axicon zone plateWe made an axicon zone-plate, which is equivalent to an axicon prism but made of concentric grating of equal pitch. Axicon zone plate was drawn by means of electron-beam lithography. The distance between grooves was 4.79 mum, with the braze angle of 7.3 degree, thickness of 0.7 mum and diameter of 4 mm. We examined experimentally that exicon-zone plate produced 0th-order Bessel-Beam spot.