Shape measuring method

A shape measuring method using a shape measuring apparatus comprising:

• a light source;
• a periodic pattern applying means for applying, to a light beam from the light source, a periodic pattern having periodicity in a direction perpendicular to an optical axis and displaceable in the direction perpendicular to the optical axis;
• an objective lens configured to irradiate an object to be measured with the light beam to which the periodic pattern is applied;
• a focus drive unit configured to displace a focal point of the objective lens relatively to the object to be measured in a direction parallel to the optical axis;
• a photodetector configured to detect the light beam reflected by the object to be measured;
• a face shape calculation unit configured to calculate, based on amplitude of intensity of the light beam detected by the photodetector, face shape data on the object to be measured;
• and
• a shape analysis unit configured to analyze, from the face shape data calculated by the face shape calculation unit, a shape of the object to be measured,
• the shape measuring method comprising:
• a top surface measuring step of acquiring, by the shape measuring apparatus, face shape data on a top surface of the object to be measured;
• a bottom surface measuring step of acquiring, by the shape measuring apparatus, face shape data on a bottom surface of the object to be measured by transmitting through the top surface of the object to be measured and aligning the focal point of the objective lens on the bottom surface of the object to be measured;
• and
• a shape analyzing step of calculating, based on the top surface shape data acquired in the top surface measuring step and the bottom surface shape data acquired in the bottom surface measuring step, a difference between the top surface shape and the bottom surface shape or shape data on the object to be measured in a thickness direction at an arbitrary position, wherein
• the object to be measured is a light-transmitting object,
• the top surface is a face close to the objective lens, and
• the bottom surface is a face far from the objective lens.