Methods and apparatus for measuring a feature of glass-based substrate

A method of measuring a feature of a glass-based substrate comprising:

• transmitting light through a thickness of the glass-based substrate towards a first major surface of the glass-based substrate and through a target location of the first major surface of the glass-based substrate, the thickness defined between the first major surface and a second major surface;
• detecting the light transmitted through the target location using at least one wave front sensor;
• generating a first signal with the at least one wave front sensor based on the detected light;
• moving the glass-based substrate in a direction transverse to the thickness of the glass-based substrate before the transmitting the light through the thickness;
• moving the glass-based substrate in the direction transverse to the thickness of the glass-based substrate after the detecting the light transmitted through the target location using the at least one wave front sensor;
• splitting the light transmitted through the target location into a plurality of beams comprising a first beam and a second beam;
• and
• changing a magnification of the first beam,
• wherein detecting the transmitted light using the at least one wave front sensor comprises:
• detecting the first beam with a first wave front sensor of the at least one wave front sensor;
• and
• detecting the second beam with a second wave front sensor of the at least one wave front sensor, and
• wherein a measurement time defined between an end of the moving the glass-based substrate before the transmitting the light through the thickness and a beginning of the moving the glass-based substrate after the detecting the light transmitted through the target location using the at least one wave front sensor is about 100 milliseconds or less.