Total Thickness Variation (TTV)

Products we use every day, and those being developed for the future, create demand for precision parallel optics like wafers, display glass, disk drives, etalons and waveguides.  The variation in thickness of these kinds of optical components, known as Total Thickness Variation or TTV, can be critical to qualify and control precisely.  TTV defines the maximum physical variation in thickness of a parallel window or concentric spherical optic, but can be measured optically.  An optical measurement enables a large area to be measured at a high lateral sampling rate and with extremely small vertical resolution.  

The Verifire MST is ideally suited to qualify TTV of components that require precise control of thickness variation – simultaneous data acquisition of each surface ensures that the surface-to-surface information is maintained in the thickness measurement.  Other optical methods of measurement require multiple individual measurements of each surface, resulting in measurement errors of thickness variation.