Atsushi Shibuya

Separation of scanning error motions for surface profile measurement of aspheric micro lens

In a scanning measurement system for aspheric micro lenses and micro lens moulds, a contact-stylus sensor, which is mounted on an air-bearing linear slide, is employed to spirally scan the surface of the aspheric micro lens mounted on an air-bearing spindle. To remove the influence of the scanning error motions of the spindle and the slide, a ring artefact is attached around the lens and two capacitance-type displacement sensors are set on the two sides of the contact-stylus sensor to scan the surface of the ring artefact. The surface profile of the ring artefact, which serves as the reference for separation of error motions, is measured to be approximately 55 nm by the reversal method. The tilt error motion and the axial error motion of scanning stage are measured to be approximately 0.5 µrad and 10 nm, respectively.

Online Measurement of Micro-Aspheric Surface Profile with Compensation of Scanning Error

A novel scanning probe measurement system has been developed to achieve precise profile measurements of micro-aspheric surfaces. The system consists of a scanning stage (a spindle and a linear slide) and a sensor unit. The sensor unit consists of a ring artifact, two capacitance sensors and a contact-mode displacement sensor. The two capacitance sensors scan the surface of the ring artifact to measure and compensate the error motions of the scanning stage while the contact-mode displacement sensor scans the surface of a micro-aspheric. In this paper, a new contact-mode displacement sensor that has a small contact force of less than 2.3 mN and a stable output has been developed. After investigating the fundamental performance of the contact-mode displacement sensor, the sensor has been applied to the micro-aspheric surface profile measurement system. The effectiveness of the measurement system has been verified by the measurement results.

Method for calibrating system parameters of a multidirectional interferometers system

A multidirectional interferometer system has been proposed and developed to measure the position and orientation of a positioning stage. In this method the system parameters, such as positions of the corner-cube reflectors and directions of the rays in the interferometers, must be determined beforehand. However, it is difficult to find ways to determine the system parameters for each different system with necessary accuracy. This paper proposes a systematic method for calibrating the system parameters when the number of the interferometers is larger than the degrees of freedom of the stage. The method is verified for a two-dimensional stage by both simulation and experiment.

An Air-bearing Displacement Sensor with a Micro-ball Stylus for Profile Measurement of 3D Micro-structured Surfaces

Micro-structured surfaces such as micro-aspheric lenses/lens arrays and micro-gears are getting increasingly important in industries. A lot of micro-structured surfaces have complicated three-dimensional (3D) profiles with short pitches and large amplitudes (high-aspect-ratio). Some of them also have steep surface slopes. It is difficult, however, to use conventional measuring instruments to measure profiles of such 3D micro-structured surfaces. This paper describes a contact-type displacement sensor for profile measurement of 3D micro-structured surfaces. The shaft of the sensor is levitated by air-bearings to reduce the contact force between the sensor and the measured surface. A sharp corn stylus is attached at the end of the sensor shaft. A precision glass micro-ball is glued on the top of the stylus shaft. The diameter of micro-ball is under 50 µm. The displacement sensor is also used to measure the profile of a micro gear with a high-aspect-ratio surface profile.