Tsuguo Kohno

High precision optical surface sensor

A noncontact optical surface sensor with <1-nm resolution has been developed. The principle of this high precision optical surface sensor (HIPOSS) is based on the focus detection technique which has been employed in the pickup for optical disks. For focus detection, we chose the critical angle method of total reflection which used the steep reflectivity change around the critical angle. The HIPOSS was designed to increase the sensitivity and to eliminate some errors for nanometer order profilometer use. The size of the HIPOSS optical head is as small as 45 × 30 × 65 mm, so it can be installed side by side with a diamond stylus in the profile measuring instrument. These styli, if we term the HIPOSS an optical stylus, can be interchanged easily to obtain profile data on the same surface by different means, contact and noncontact. The repeatability of going and returning measurements is <1-nm rms, and the difference between HIPOSS and stylus measurements is also below 1-nm rms for most example surfaces. Using the high speed response of the HIPOSS, 3-D profile measurement over the workpiece and in-process measurements for ultraprecise diamond turning are also demonstrated.

In-process measurement and workpiece-referred form accuracy control system (WORFAC): application to cylindrical turning using an ordinary lathe

Abstract High levels of accuracy can be achieved in precision machining through the use of highly accurate machine tool elements and under good machining and environmental conditions. To improve the accuracy and stiffness of the machine tool, we proposed a new method using in-process measurement and confirmed its effectiveness. In this work, this method is applied to cylindrical turning. The following were determined: the effectiveness of simulation for estimating the form accuracy, a new function of the corrective servo by changing the feedback gain, and the effectiveness of the new function for correcting the error. These were confirmed by both simulation and experiment.

In-process measurement and a workpiece-referred form accuracy control system (WORFAC): concept of the method and preliminary experiment

Abstract Precision machining can achieve high levels of accuracy through the use of a highly accurate spindle, straight feed mechanisms, a rigid base and a single-point diamond tool. Research is underway aimed at achieving even higher levels of accuracy by adding computers, interferometers or encoders for practical control. In this report, a control system (workpiece-referred form accuracy control system) is proposed in which the control is based on the workpiece, instead of the conventional approach which achieves the accuracy by increasing that of each mechanical element. This system performs inprocess measurement of the workpiece and uses this information to execute direct control over the machining.

Radial shearing interferometer for in-process measurement of diamond turning

A stable interferometer with two zone plates to measure a concave mirror figure is developed. The principle of the measurement is based on the radial shearing interference in which the measuring wavefront from the entire mirror surface under test is referred to that from the central part. On-machine experiments show that the interferometer is stable and compact enough to be applicable to in-process measurement for diamond turning at about 0.06 ?m p-v accuracy.

Concept and basic study of improvement system of surface roughness, waviness and figure accuracy by WORFAC

Abstract In ultraprecision machining technology, manufacture of more precise and large elements is expected. The author proposed a new system, named workpiece-referred form accuracy control system (WORFAC), and confirmed an effectiveness of this manufacturing method on a waviness improvement. In this report, we propose a new system with WORFAC, which has three control systems; a waviness control system, a figure control system, and a surface roughness control system. So far, basic studies on the figure and surface roughness control systems are carried out. And the possibility of this new system is confirmed.

ACCURACY IMPROVEMENT OF MACHINE TOOL BY WORKPIECE-REFERRED CONTROL; - Simulation of sensor position for plain turning -

Simulation of WORFAC (Workpiece-Referred Form Accuracy control) is an effective method for estimating the formed accuracy made by controlling system. In this study, the simulation is applied to plain turning and the positioning of sensor is investigated.

State and future trend of surface defect inspection.

表面欠陥検査が,産業界の広い分野で必要とされ,個別にさまざまな開発を行いつつ対処しているものの,現状ではまだ不十分な状態にあることが,アンケートの結果などからも明らかである.そこで,現在取り組まねばならない主要な開発課題を列挙すると,次のようになる.(1)表面欠陥に対する大規模な調査,形態の系統的分類,名称の整理,これらを通じての標準化への対応(2)光学的手段を中心に,欠陥検出に対する多様な測定法およびセンサの開発(3)画像情報処理やパターン認識など,生物の高度な機能を参考にしたソフトウェアの開発,エキスパート的判断をするための強力なデータベースの構築これらに加えて,周辺機能として,ズーミング,センサの移動,角度変化などのハードメカニズムの発達も忘れてはならない事項である.以上,一般的または総合的な意味での表面欠陥検査に対する動向を述べた.ただし,実際はむしろ,今まで地道に行われてきたような,狭い領域での個別の対応の積み重ねによって,全体のレベルも向上してゆくように思われる.しかし,産業の発達により,品質管理はますます厳しくなってきている.表面欠陥検査は,その代表的なものであり,このへんで課題や方向を見直し,全体として取り組むべきものについては,英知を結集して問題を解決することも必要であろう.