Offset amount calibrating method and surface texture measuring machine

An offset amount calibrating method for a surface texture measuring machine including:

• a stage on which an object is mounted;
• a contact-type detector being provided with a stylus that is brought into contact with a surface of the object;
• an image probe that captures an image of the surface of the object;
• a relative movement mechanism that relatively moves the stage against the contact-type detector and the image probe and moves the contact-type detector and the image probe against the stage;
• and a controller that controls an operation of the relative movement mechanism and executes processing on measurement data obtained by the contact-type detector and image data obtained by the image probe, the method obtaining an offset amount between the contact-type detector and the image probe, the method comprising:
• setting on the stage a calibration chart that includes not less than two non-parallel linewidth patterns being disposed relative to a reference position of the calibration chart and each having a known width and a level difference;
• capturing an image of the linewidth patterns of the calibration chart by the image probe to obtain the reference position of the calibration chart;
• measuring at least two of the linewidth patterns of the calibration chart by the contact-type detector to obtain the reference position of the calibration chart;
• and
• calculating a difference between the reference position obtained by using the image probe and the reference position obtained by using the contact-type detector to obtain the offset amount.