Interferometric waviness detection systems

An interferometer detection system, comprising:

• a beam splitter configured to receive a collimated light signal and split the collimated light signal into a first light signal traveling along a first path and a second light signal traveling along a second path;
• a first mirror configured to receive and reflect the first light signal along the first path;
• a device under test comprising:
• a touch panel disposed on a front surface of the device under test, the touch panel comprising a transparent optical material having a thickness, a flatness and a refractive index across an area thereof;
• a digital display disposed rearward of the touch panel, the digital display comprising a second mirror configured to receive and reflect the second light signal along the second path via the transparent optical material that is located along the second path between the beam splitter and the second mirror;
• and
• a case which encloses the digital display and frames the touch panel;
• and
• a 2D photosensor array configured to receive from the beam splitter the reflected first light signal along the first path merged with the reflected second light signal double passing through the transparent optical material along the second path and generate an interference fringe pattern;
• wherein the beam splitter, first mirror, second mirror and 2D photosensor array are configured and arranged to provide one of a non-sinusoidal interference fringe pattern and a sinusoidal interference fringe pattern,
• the non-sinusoidal interference fringe pattern being provided when a non-uniformity in is present in the transparent optical material, the non-uniformity being found in at least one of the flatness, the thickness and the refractive index of the transparent optical material, the non-sinusoidal interference fringe pattern arising from geometrical variation between a first wavefront of the reflected first light signal along the first path and a second wavefront of the reflected second light signal double passing through the transparent optical material along the second path,
• the sinusoidal interference fringe pattern being provided when the non-uniformity is not present in the transparent optical material, the sinusoidal interference fringe pattern arising from the absence of geometrical variation between the first and second wavefronts.