Satoshi Kiyono

Angle measurement based on the internal-reflection effect: a new method

We describe a new method of angle measurement that is based on the internal-reflection effect at an air-glass boundary. The method uses a differential detection scheme to largely reduce the inherent nonlinearity of the reflectance versus the angle of incidence in internal reflection. With nonlinearity reduced, the displacement of the angle of incidence can be determined accurately by measuring the reflectance. The resolution and measurement range are determined by the initial angle of incidence, the polarization state of the light, and the number of reflections. Compared with interferometers and autocollimators, this method has the advantage of a simple sensor design for applications ranging from a wide measurement range to extremely high resolution. Other advantages are compact size, simple structure, and low cost. A theoretical analysis of the method and some experimental results of a prototype sensor are presented. The possible applications of the method are also discussed.

Precision measurement of cylinder straightness using a scanning multi-probe system

This paper describes a scanning multi-probe system for measuring straightness profiles of cylinder workpieces. The system consists of two probe-units, each having three displacement probes. The two probe-units, which are placed on the two sides of the test cylinder, are moved by a scanning stage to scan the two opposed straightness profiles of the cylinder simultaneously. A differential output calculated from the probe outputs in each probe-unit cancels the influence of error motions of the scanning stage, and a double integration of the differential output gives the straightness profile. It is verified that the difference between the unknown zero-values of the probes in each probe-unit (zero-difference) will introduce a parabolic error term in the profile evaluation result, which is the largest error source for straightness measurement of long cylinders. To make zero-adjustment accurately, the cylinder is rotated 180° and scanned by the probe-units again after the first scanning. The zero-differences of the probe-units, as well as the straightness profiles of the cylinder, can be accurately evaluated from the output data of the two measurements. The effectiveness of this method is confirmed by theoretical analysis and experimental results. An improved method, which can measure the variation of the zero-difference during the scanning, is also presented.

A New Multiprobe Method of Roundness Measurements

This paper presents a new multiprobe method for roundness measurements called the mixed method. In this method, displacements at two points on a cylindrical workpiece and an angle at one of the two points are simultaneously monitored by two probes. The differential output of the probes cancels the effect of the spindle error, and deconvolving the differential data yields the correct roundness error. The mixed method is compared to the traditional 3-point method with respect to the transfer function and resolution. Unlike the 3-point method, the mixed method can completely separate the roundness error and the spindle error, and can measure high-frequency components regardless of the probe distance. Resolution can also be improved throughout the entire frequency domain by increasing angular separation of the probes. An optical sensor specifically suited to the mixed method is designed and used to make roundness measurements. A fiber coupler and single-mode fibers are used in the sensor to divide a light beam from a laser diode into two beams, resulting in a compact sensor with good thermal drift characteristics. The displacement meter of the sensor is based on the imaging system principle and has a resolution of 0.1 μm. The angle meter is based on the principle of autocollimation and has a resolution of 0.5 in. A measurement system is constructed to realize measurements of roundness by using the optical sensor. Experimental results confirming the effectiveness of the mixed method for roundness measurements are also presented in this paper.

High accuracy profile measurement of a machined surface by the combined method

The combined method, which combines the generalized 2-point method with the inclination method, has been developed to measure profiles that include high-frequency components whose spatial wavelengths are shorter than the probe interval. It is suitable for measuring discontinuous profiles that include step-wise variations and abrupt changes. In this paper, we discuss the influences of the setting error of the probe interval, and the positioning error of sampling when we use the combined method to measure a step-wise profile. Results of theoretical analyses show that these errors cause the same kind of evaluation errors in the profile measured with the combined method, and large profile evaluation errors are caused by the edge part of a step-wise profile. The value of the profile evaluation error is concerned with the aperture size of the displacement probe and the height of the step-wise profile. The influence of the gain errors of the probe is also investigated. An automatic selection method that can select the standard area properly and quickly is developed to improve the accuracy of the combined method. A machined surface with a step-wise profile is measured by using two capacitance-type displacement probes. Experimental results that confirm the effectiveness of the combined method are also presented.

Profile measurement of machined surface with a new differential method

Abstract This article presents a new differential method for surface profile measurement called the combined method. This method, which combines the generalized two-point method with the inclination method, is developed to measure profiles that include high-frequency components whose spatial wavelengths are shorter than the distance between the probes. Differential methods, such as the generalized two-point method and the inclination method, have been used to measure profiles under on-machine conditions. The inclination method can determine relative heights rigoursly among discrete points whose interval is equal to the probe interval. Even though the correctness of the relative heights is not influenced by high-frequency components in the profile, the method cannot provide information about points not included in the data group. On the other hand, the generalized two-point method can measure relatively smooth surfaces accurately with a sampling period as short as necessary. The proposed combined method features the advantages of both methods and is capable of rigorously expressing the relative heights of sampled points with a period shorter than the probe interval. Experimental results confirming the effectiveness of the combined method are also presented in this article.

Precision Measurement of Two-Axis Positions and Tilt Motions Using a Surface Encoder

Abstract A prototype surface encoder consisting of a sinusoidal angle grid and a two-dimensional slope sensor is developed for two-axis position measurement. The angle grid has a three dimensional micro-structured surface, which is a superposition of periodic sinusoidal waves in the X- and Y-directions with spatial wavelengths of 150 μn and amplitudes of 100 nm over an area of up to 150 mm in diameter. The laser-based slope sensor is used to read local slope profiles of the grid surface. The X- and Y-positions together with tilt motions about the X-, Y- and Z-axes can be detected with resolutions of 0.1 μm and 1 arc-second through scanning a multi-spot laser beam across the grid surface at a constant speed.

High-accuracy roundness measurement by a new error separation method

Abstract This paper presents a new error separation method for accurate roundness measurement called the orthogonal mixed method. This method uses the information of one displacement probe and one angle probe to separate roundness error from spindle error. This method was developed from the mixed method, which uses the information of two displacement probes and one angle probe to carry out the error separation. In the present paper, the relationship between the characteristics of the mixed method and the probe arrangement is analyzed. Well-balanced harmonic response of the mixed method is verified to be obtainable for the case where the angular distance between the displacement probe and the angle probe is set at 90°. This orthogonal mixed method also had the simplest probe arrangement, because it requires only one displacement probe and one angle probe to realize the error separation. Optical probes were used to construct an experimental measurement system that employs the orthogonal mixed method. The displacement probe and the angle probe both use the principle of the critical angle method of total reflection, and they have stabilities of 1 nm and 0.01 in., respectively. The measurement results show that roundness measurement can be performed with a repeatability on the order of several nanometers.

Precision Measurement of Multi-Degree-of-Freedom Spindle Errors Using Two-dimensional Slope Sensors

Abstract A measuring system consisting of three two-dimensional surface slope sensors is developed for spindle error and roundness measurement. The sensors, which are in the same XY-plane perpendicular to the spindle axis (Z), are placed around a cylindrical workpiece mounted in the spindle. The workpiece out-of-roundness and the X- and Y-directional components of the spindle radial error motion can be separated from each other using the radial direction outputs of sensors. On the other hand, the two-directional components of the spindle angular error motion can be obtained accurately from the angular direction outputs of sensors. Experiments of spindle error and roundness measurement were carried out.

Development of an optical probe for profile measurement of mirror surfaces

An optical probe for profile measurement of mirror surfaces is developed. This probe, consisting of a displacement meter and an angle meter, can detect the displacement and surface slope at one point simultaneously. Both the displacement meter and the angle meter of the probe employ position-sensing detectors (PSDs) as detecting devices. An optical fiber output is used as the light source so that the probe is made compact and has good characteristics. To eliminate influences of light disturbance the light intensity of the light source is modulated by a sine wave of 20 kHz, and only the position signal is removed from signals obtained from the PSDs. Calibration results show that the displacement meter and the angle meter can measure larger than ±500?m and ±60 arcmin with good linearity, respectively. Estimating from the SNR of the system, the displacement resolution and angle resolution are ±10 nm and ±0.1 arcsec, respectively.

On-machine roundness measurement of cylindrical workpieces by the combined three-point method

In this paper, we describe a new differential method for on-machine roundness measurement of cylindrical workpieces, which is called the combined three-point method. This method combines the advantages of the generalized three-point method and the sequential three-point method and can accurately measure roundness profiles including stepwise variations. In the combined three-point method, some data points in the roundness profile evaluated by the generalized three-point method are chosen as the reference points of the standard area and used to determine the relationships among the data groups of the sequential three-point method. An interpolation technique is employed in the data processing of the generalized three-point method to improve the accuracy of the standard area. Theoretical analyses and computer simulations confirming the feasibility of the combined three-point method are shown in this paper. A roundness measurement system using three capacitance-type displacement probes is constructed. The measurement system and the experimental results are also presented.