Kwon Su Chon

Wear inspection of a single-crystal diamond tool used in electroless nickel turning

Abstract. Single-point diamond turning is a useful optical fabrication method for simultaneously obtaining a smooth surface and generating an accurate shape. Generally, a single-crystal diamond tool has been used in the single-point diamond turning method and a degree of the wear on the diamond tool is unavoidable. Tool wear causes the degradation of the surface quality, surface roughness, and shape accuracy of the workpiece. Inspection of tool wear is important in improving the surface quality. A single-crystal diamond tool used in electroless nickel turning was inspected by a laser scanning microscope and a scanning probe microscope. Regular grooves were observed on the flank face of the diamond tool, and the pitch interval was the same as the feed rate. The worn distance was obtained by measuring the clearance angle and the groove length on the flank face of the worn diamond tool. The worn distance of the diamond tool was 1.7 μm after machining electroless nickel for a 3.18 km cutting distance. The worn distance could also be obtained using the worn width on the flank face and the nose radius and was 2.05 μm, which was very close to 1.7 μm. Two methods based on the wear measurement of the flank face will be new methods to measure the worn distance of the single-crystal diamond tool.

Usefulness of a Small-Field Digital Mammographic Imaging System Using Parabolic Polycapillary Optics as a Diagnostic Imaging Tool: a Preliminary Study

Objective To evaluate the efficacy for spatial resolution and radiation dose of a small-field digital mammographic imaging system using parabolic polycapillary optics. Materials and Methods We developed a small-field digital mammographic imaging system composed of a CCD (charge coupled device) detector and an X-ray source coupled with parabolic polycapillary optics. The spatial resolution and radiation dose according to various filters were evaluated for a small-field digital mammographic imaging system. The images of a test standard phantom and breast cancer tissue sample were obtained. Results The small-field digital mammographic imaging system had spatial resolutions of 12 lp/mm with molybdenum and rhodium filters with a 25-µm thickness. With a thicker molybdenum filter (100 µm thick), the system had a higher spatial resolution of 11 lp/mm and contrast of 0.48. The radiation dose for a rhodium filter with a 25-µm thickness was 0.13 mGy within a 10-mm-diameter local field. A larger field image greater than 10 mm in diameter could be obtained by scanning an object. On the small-field mammographic imaging system, microcalcifications of breast cancer tissue were clearly observed. Conclusion A small-field digital mammographic imaging system with parabolic polycapillary optics may be a useful diagnostic tool for providing high-resolution imaging with a low radiation dose for examination of local volumes of breast tissue.

Precise measurement of inner diameter of mono-capillary optic using X-ray imaging technique

BACKGROUND Mono-capillary optics have been applied to increase the performance of X-ray instruments. However, performance of a mono-capillary optic strongly depends on the shape accuracy, which is determined by the diameters of the inner hollow of the capillary along the axial direction. OBJECTIVE To precisely determine the inner diameter of the capillary optic used in X-ray imaging technique, which aims to replace the conventional method using a visible microscope. METHODS High spatial resolution X-ray images of the mono-capillary optic were obtained by a synchrotron radiation beamline. The inner diameter of the mono-capillary optic was measured and analyzed by the pixel values of the X-ray image. RESULT Edge enhancement effect was quite useful in determining the inner diameter, and the accuracy of the diameter determination was less than 1.32 μm. Many images obtained by scanning the mono-capillary optic along the axial direction were combined, and the axial profile, consisting of diameters along the axial direction, was obtained from the combined image. The X-ray imaging method could provide an accurate measurement with slope error of±19 μrad. CONCLUSIONS Applying X-ray imaging technique to determine the inner diameter of a mono-capillary optic can contribute to increasing fabrication accuracy of the mono-capillary optic through a feedback process between the fabrication and measurement of its diameter.