Embodiments of the present disclosure are directed toward a system and method to calibrate calipers of a downhole tool. Specifically, a calibration tool includes a substantially cylindrical calibration ring. The calibration tool also includes a finger coupled to the calibration ring. The finger is configured to engage with the downhole tool such that the calibration ring is mounted to the downhole tool and is coaxial with a tool axis of the downhole tool.

An optical test system and corresponding method disclosed herein provides highly accurate test data for both sides of a lens simultaneously and efficiently to analyze the surface topography and/or geometric parameters of a lens or lens system. More particularly, the optical test system and corresponding method moves the lens in test plane to align a plurality of points of a test pattern on a lens surface with a vertical axis while probes aligned with the vertical axis and on opposing sides of the lens simultaneously collect wavelength-specific data for both lens surfaces. The optical test system uses the collected wavelength-specific data to produce a surface topography and/or the associated lens geometric parameters for each lens surface.