Hideo Takino

Shaping of steel mold surface of lens array by electrical discharge machining with single rod electrode.

We propose a method for fabricating a lens array mold by electrical discharge machining (EDM). In this method, the tips of rods are machined individually to form a specific surface, and then a number of the machined rods are arranged to construct an electrode for EDM. The repetition of the EDM process using the electrode enables a number of lens elements to be produced on the mold surface. The effectiveness of our proposed method is demonstrated by shaping a lens array mold made of stainless steel with 16 spherical elements, in which the EDM process with a single rod electrode is repeatedly conducted.

Ion beam planarization of diamond turned surfaces with various roughness profiles

The effectiveness of ion beam planarization (IBP) to reduce surface roughness of diamond turned NiP surfaces was investigated. The surfaces with various spatial wavelengths and depths of turning marks were spray-coated and planarized with broad ion beam. The ion beam planarization was performed at a special angle where the etching rate of photoresist is closely similar to NiP. It is found that the combined process of spray-coating and ion-beam-planarization can effectively reduce the surface roughness of diamond turned NiP. The spatial wavelength and depth of turning marks have limited influence on surface roughness reduction rate. The final surface roughness after ion beam planarization is 30%~40% of the original roughness, irrespective of spatial wavelength and depth of turning marks. Extending planarization time does not alter surface quality after photoresist is etched away. These results show that the IBP is applicable to roughness minimization of diamond turned surfaces.

Smoothing of optical surface corners by abrasive polishing with a plate spring

We propose a new method for polishing the corners of optical surfaces that uses a plate spring as a polishing tool. In this method, a polishing pad is fixed to the tip of a plate spring, which moves back and forth on a workpiece surface. During the polishing, the plate spring is bent while maintaining a constant amount of deflection to generate a stable polishing load. The edge of the plate spring enables the polishing of the corners of the workpiece. We have developed a polishing machine with a plate spring, and we performed polishing experiments on silicon plates to investigate the fundamental characteristics of our proposed method. It was found that the roughness of workpiece surfaces decreases with the progress of polishing and that the areas are polished almost uniformly, demonstrating the effectiveness of our polishing method.