Holographic focimetry: Towards dioptric and prismatic power evaluation in ophthalmic solutions

A novel concept of focimeter based on digital in-line holography is proposed and experimentally validated for the measurement of both dioptric and prismatic powers in ophthalmic lenses. The former is achieved through the variation in lateral magnification under Gaborʹs regime and the latter by evaluating lateral shifts, both within the diffraction pattern of a test reticle. In contrast with previous designs, the new proposed approach does not require axial displacements, imaging conditions or double-path configurations. It only requires a diffraction pattern on the digital sensor, which is modified in either scale or lateral shift (or both) by the lens under test in comparison with a reference configuration without lens. The proposed concept offers an accurate, compact, and innovative approach to measure two basic parameters (dioptric power and prismatic effect) in ophthalmic solutions for refractive error compensation. Experiments considering the characterization of different lenses successfully validate the first steps of the holographic focimeter towards ophthalmic lens characterization.