A imaging ellipsometer system is provided including a lens configuration with tunable acoustic gradient index of refraction (“TAG”) lens. The imaging ellipsometer system further includes a light source, a polarizer, a compensator, an analyzer and a camera. Light from the light source passes through the polarizer and is directed toward a workpiece. In various implementations, the compensator is located and configured to elliptically polarize the light either before or after the light is reflected from the workpiece. The lens configuration receives the reflected workpiece light and the TAG lens is controlled to provide a modulation of a focus position. The camera receives workpiece light that passes through the TAG lens and the analyzer during an image exposure and provides a corresponding camera image. An ellipsometry analysis is performed (e.g., to determine at least one of a refraction index, or a thickness of one or more layers of the workpiece, etc.)