METHODS AND APPARATUS FOR MEASURING A FEATURE OF GLASS-BASED SUBSTRATE

An apparatus can comprise an illumination source and at least one wave front sensor that positioned in a first region. A reflector can be positioned in a second region. A measurement plane can be positioned between the first region and the second region. The reflector can be configured to reflect the light. The at least one wave front sensor can be configured to detect the light. Methods of measuring a feature of a glass-based substrate can comprise emitting light from the illumination source. Methods can comprise transmitting the light through a thickness of the glass-based substrate. Method can comprise transmitting the light through a target location of a first major surface of the glass-based substrate. Methods can comprise detecting the light with the at least one wave front sensor and generating a signal based on the detected light.