Probe type shape measuring sensor, and nc processing equipment and shape measuring method using the sensor

Abstract

A probe head and a laser interferometric displacement meter are provided. The probe head supports a probe that is capable of contacting a workpiece that is free to move in the direction of the workpiece, and drives the probe towards the workpiece. The displacement meter measures the displacement of the probe with a high accuracy without contact. The probe head is also provided with a probe shaft with steps at intermediate portions thereof and air bearings that support the probe shaft on each side of the steps. The air bearings have a high stiffness in the radial direction, and the probe shaft is made to float by using compressed air, thus the resistance of the shaft to sliding is reduced. In addition, another compressed air is supplied to the location of the step and produces a driving force in the direction of the workpiece due to the difference of cross sectional areas on each side of the step, that provides a very small load within a predetermined range. Thereby, the measuring pressure can be adjusted to a constant very small load without reducing the stiffness of the bearings of the probe, and the measuring pressures can be varied freely. Therefore, a sub-micron accuracy of about 0.1 &mgr;m can be obtained, and the equipment can be made compact and is easily applied to on-machine measurements.