Noncontact method for sensing thickness and refractive index of intraocular lens implants using a self-calibrating dual-confocal laser caliper

Abstract

We present a fiber-optic dual-confocal laser caliper method for noncontact high-precision sensing and measuring thickness and refractive index of intraocular lens (IOL) implants. The principle of the method is based on sensing and measuring the confocal intensity response of the laser beam reflection from the opposite object surfaces, which provides the advanced feature of having no limitations on the object shape, thickness, and transparency. Using single-mode optical fibers and a 658-nm laser source, the thickness measurement accuracy was assessed to be as high as 5 μm. In addition, refractive index of a transparent object with thickness smaller than the working distance of the focusing lenses can be measured. The thickness and refractive index of a planoconvex IOL were measured with a high accuracy.

Simultaneous measurement of thickness and group refractive index in birefringent crystals

“…The triangulation methods are limited by the spatial resolution of the beam, for example, the minimum deflection angle method, which requires high accuracy of the test prisms and is difficult to process [4]. The differential confocal methods [5,6], which needs to repeatedly search for the differential confocal method in the measurement process needs to repeatedly look for the position of the focusing spot and accurate alignment, measurement of cumbersome cycle time. Optical interference method is widely used because of its fast and high precision measurement ability, among which spectral-domain interferometry method is the most typical.…”