Opto-Mechanical Eye Models, a Review on Human Vision Applications and Perspectives for Use in Industry.

The purpose of this review is to aggregate technical information on existent optomechanical eye models (OME) described in the literature, for image quality assessment in different applications. Several physical eye models have been reviewed from peer-reviewed papers and patent applications. A typical eye model includes an artificial cornea, an intraocular lens or other lens to simulate the crystalline lens, an aperture as the pupil, and a posterior retinal surface, which may be connected to a light sensor. The interior of the eye model may be filled with a fluid to better emulate physiological conditions. The main focus of this review is the materials and physical characteristics used and the dimensional aspects of the main components including lenses, apertures, chambers, imaging sensors and filling medium. Various devices are described with their applications and technical details, which are systematically tabulated highlighting their main characteristics and applications. The models presented are detailed and discussed individually, and the features of different models are compared when applicable, highlighting strengths and limitations. In the end there is a brief discussion about the potential use of artificial eye models for industrial applications.

Oblique astigmatism and field curvature measured with light-field imaging.

The testing of astigmatism and field curvature of an optical system with light-field imaging is proposed. The method consists in measuring the depth map, obtained with a plenoptic camera, of the image of a test pattern formed by the optical system. To demonstrate the accuracy of the method, the virtual image formed by a plano-convex lens was tested. The resulting depth map was compared with the sagittal and tangential foci distances calculated with the Coddington theory. The proposed method could be applied to the quality testing of ocular optics, including eyeglasses, eyepieces, virtual reality goggles, and augmented reality devices.

Controllable transport mean free path of light in xerogel matrixes embedded with polystyrene spheres.

Xerogel matrices, made by sol-gel techniques, are embedded with polystyrene spheres to promote multiple scattering of light. Varying the concentration of the spheres inside the matrix allows one to adjust the transport mean free path of light inside the material. Coherent backscattering measurements show that a range of transport mean free paths from 90 to 600 nm is easily achieved. The determination of the matrix refractive index permits a direct comparison to multiple scattering and Mie theory. Such tunable diffusive sol-gel derived samples can be further optimized as random laser materials.

Time-resolved pulse propagation in a strongly scattering material.

Light transport in macroporous gallium phosphide, perhaps the strongest nonabsorbing scatterer of visible light, is studied using phase-sensitive femtosecond pulse interferometry. Phase statistics are measured at optical wavelengths in both reflection and transmission and compared with theory. The diffusion constant of light is measured in both reflection and transmission as a function of thickness and compared with theories for diffusive transport and localization. An unusually high energy velocity due to the bicontinuous structure of the porous network is reported. For such strongly scattering samples, we show that surface properties and the effective index of refraction need to be treated carefully.

Anisotropic diffusion of light in a strongly scattering material.

Light transport in a strongly scattering, strongly anisotropic material is studied experimentally using both static and time-resolved techniques. Both the static and the dynamic results are well characterized by a diffusion equation with an anisotropic diffusion tensor and a scalar absorption term. Light diffuses 4.0 times faster along the uniaxial axis of the material compared with diffusion in the orthogonal directions.