Offset amount calibrating method and surface profile measuring machine

An offset amount calibrating method for a surface profile 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 jig that has a surface being provided with a calibration pattern with a level difference;
• measuring the calibration pattern of the calibration jig by the contact-type detector to obtain a first reference position of the calibration pattern;
• capturing an image of the calibration pattern of the calibration jig by the image probe to obtain a second reference position of the calibration pattern;
• and
• calculating a difference between the first reference position and the second reference position to obtain the offset amount.