What instrument is used to measure the center thickness of a lens?

The lens caliper is the appropriate instrument for measuring the center thickness of a lens. This tool is specifically designed to provide accurate measurements of the thickness of lenses at various points, including the center. The design of a lens caliper allows for precise placement on the lens, enabling the measurement of thickness with minimal error, which is crucial for ensuring proper fit and optical performance in eyewear.

A micrometer, while capable of measuring small distances with great accuracy, is typically used in manufacturing settings for various applications, not specifically tailored for optical lenses. A lensometer, on the other hand, is primarily used to measure the prescription of spectacles or to verify the power of lenses, rather than their thickness. An optical bench is a versatile setup used for various optical experiments and testing but does not directly measure lens thickness. Therefore, the lens caliper is uniquely suited for this measurement task, ensuring accurate data relevant to the lens's optical characteristics and fitting.