In this work, we present the methods of fabrication and characterization of biconvex spherical and aspherical lenses with 25 and 50 mm diameters that have been created via additive technology using a Formlabs Form 3 stereolithography 3D printer. After the prototypes are postprocessed, fabrication errors ≤ 2.47 % for the radius of curvature, the optical power, and the focal length are obtained. We show eye fundus images captured with an indirect ophthalmoscope using the printed biconvex aspherical prototypes, proving the functionality of both the fabricated lenses and the proposed method, which is fast and low-cost.

In this paper, the use of four flat-null-screens forming a quadrangular prism setup is employed as a target for an experimental corneal topographer. Topographic maps of three reflective calibration spheres with different radii of curvature: 7.70 mm, 9.42 mm, and 6.20 mm, and the corneal surface evaluation of a volunteer subject are presented. The experimental setup is based on the null-screen method. Zonal reconstruction of the surface shape of the human cornea is obtained by numerical integration of the normal vectors. The corresponding elevation map was found fitting an spherical model to the recovered data. The differences obtained in radius of curvature were 0.02% or less for the calibration spheres, and the cornea under test showed a difference of 1.39% (0.6 diopters) compared to the value obtained with ORBSCAN topographer.

This work presents a compact refractometric system based on In-Line Digital Holography (ILDH) for the non-invasive characterization of transparent media, encompassing both liquids and high-refractive-index optical glasses. The core of the system is a cost-effective, lensless setup in which a 532 nm laser source and a microscope objective generate a divergent spherical wavefront that illuminates a 10 μm aluminum particle. The resulting diffraction pattern, modulated by samples in the optical path, is recorded by a CMOS sensor. The refractive index of the sample is determined by numerically locating the axial position of the particle-reconstructed image, which directly corresponds to the optical path difference introduced by the test medium. The optimal reconstruction plane is objectively located using an autofocus algorithm based on the Kurtosis metric, which identifies the sharpest image. The system successfully characterizes media across a broad refractive index range from 1.33 to 1.78, yielding linear calibration curves for both liquid and solid samples. The instrument achieves an axial reconstruction resolution of 30 μm and a refractive index precision of ±0.01 RIU. This ILDH approach offers a highly portable, cost-effective, and non-contact solution for refractive index measurement, demonstrating significant potential for industrial quality control and high-throughput point-of-care applications.

To design and implement a prototype Shack-Hartmann wavefront sensor, a zonal and a modal algorithm were programmed and tested with a simulation in MATLAB. Once both algorithms were validated, they were implemented in the prototype. To test it in an experimental environment, we used a deformable mirror to replicate ocular aberration profiles and measured them with the sensor, fitting the obtained data to Zernike polynomials. The calculated wavefronts were described with metrics like PV and RMS to determine the fidelity of the sensor with each algorithm. On average, Zernike fitting increased the peak-to-valley (PV) value by approximately 3% while reducing the root mean square (RMS) error by 3%. In contrast, trapezoidal integration decreased the PV value by about 2% but increased the RMS error by approximately 10%.