Shape measuring apparatus and method for manufacturing target object to be coated

A shape measuring apparatus configured to measure a shape of a target object by applying white light to the target object and using reflected light from the target object, the shape measuring apparatus comprising:

• a light source configured to output the white light;
• a two-beam interference objective lens configured to divide the white light into two light beams, apply one of the two light beams to the target object and the other light beam to a reference surface, and cause interference between the reflected light from the target object and reflected light from the reference surface to output interference light;
• an imaging plane configured to obtain an image of the interference light output from the two-beam interference objective lens;
• an observation optical system comprising at least one optical element configured to redirect and guide the white light output from the light source to a surface of the target object through the two-beam interference objective lens and to guide the reflected light from the surface to the imaging plane after the reflected light has passed through the two-beam interference objective lens;
• a Z stage configured to move the two-beam interference objective lens relative to the target object;
• and
• a control computer configured to operate an imaging device comprising the imaging plane to obtain a plurality of images while operating the Z stage to change a distance between the target object and the two-beam interference objective lens in an optical axis direction of the two-beam interference objective lens, and configured to measure the shape of the target object using the plurality of images,
• the control device computer being further configured to
• for each unit region in the plurality of images, calculate, as a focus position of the unit region, a position of the two-beam interference objective lens at which a luminance-based evaluation value is maximized over the plurality of images, and measure the shape of the target object based on the focus position of each unit region in the plurality of images,
• use, as the evaluation value, a luminance of each unit region in the plurality of images as well as a value correlated with a difference between the luminance of the unit region and luminances of a plurality of unit regions adjacent to the unit region,
• use the luminance as the evaluation value when a maximum value of the luminance of each unit region in the plurality of images is greater than a threshold value, and
• use the value correlated with the difference as the evaluation value when the maximum value is smaller than the threshold value.