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

在本计画中，我们研究轴棱锥棱镜的三维成像特性及其在长焦深成像系统中的应用。主要取得了以下进展：1）轴棱锥的基础实验我们制作了一个垂直角为160 °的轴棱锥，我们观察到产生了宽度为4 μ m的0阶贝塞尔光束（在中心峰的半峰处）实验结果表明，该激光器具有良好的焦深特性，当准直光束入射到该激光器上时，焦深为52 mm，并从理论和实验上研究了斜入射条件下的光束轮廓。当入射角超过4度时，离轴像差在光斑中占主导地位，中心光斑分裂为四个。从理论分析和计算机模拟两方面验证了该方法的有效性。实验还发现轴棱锥透镜比普通透镜具有更强的抗逗号像差能力。2）轴棱锥光刻系统。利用该系统，我们成功地在光刻胶上画出了宽1.0 μ m、深1.5mm的沟槽。3）轴棱锥波带片的制作我们制作了一个轴棱锥波带片，它相当于轴棱锥棱镜，但由同心等间距光栅制成。用电子束曝光法制作了轴锥波带片。槽之间的距离为4.79妈妈，与钎焊角为7.3度，厚度为0.7妈妈和直径为4毫米。我们实验研究，出射型波带板产生0阶贝塞尔束斑。

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.