Module Overview

Geometrical Optics

This module prepares the student for the later subjects studied within the Ophthalmic Optics and Ophthalmic Dispensing programmes by providing a strong theoretical and practical foundation in the principles of geometrical optics and ray tracing techniques. The principles governing thin and thick lenses will be explored, and image formation by lens systems will be discussed. Principles of focal power and focal lengths of lenses and lens systems will be outlined and discussed in relation to optical systems and the eye. Optical aberrations will be discussed in relation to the eye and optical instruments.

Module Code

PHYS 1811

ECTS Credits


*Curricular information is subject to change

Introduction to light and the rectilinear propagation of light and shadows. New Cartesian sign convention. Pinhole effect and refractive correction and examination. Laws of reflection, concave and convex spherical mirrors, focal lengths and powers. Purkinje images in visual science. Laws of refraction, relative and absolute refractive index, critical angle, refraction at plane and curved surfaces. Refraction by prisms. Newton’s equations.  Focal lengths and focal powers. Depth of field and depth of focus related to bifocals, multifocal lenses and eye examination routine. Thin lens optics: thin lenses in air and other media, thin lens formulae, cardinal points, vertex powers and vertex focal lengths, transverse and angular magnification. Unwanted prismatic effect of lenses and its importance in visual science. Equivalent powers and cardinal points of thin lens systems Thick lens optics: thick lenses theory,  surfaced power and thickness, thick lenses in air and other media. Equivalent powers, and cardinal points of thick lens systems. Vertex powers and effective power and refractive correction. Stops: aperture and field stops, entrance and exit pupils, image brightness.  Aberrations: theoretical considerations of aberrations in lenses and lens systems, 1st and 3rd order paraxial theory, monochromatic aberrations, methods of reducing monochromatic aberrations, the Petzval surface. Chromatic aberration: aberrations in positive and negative lenses, elimination of chromatic aberration, achromatic doublet. Distortion and coma. Fraunhofer lines, separated achromatic doublets. Optical instruments: principles of ophthalmic and optical instruments, field of view and magnification, introduction to ophthalmic lenses, Fresnel lenses. Basic optics of the eye using the Gullstands’ No 1 schematic eye and Gullstands’ No 2 simplified schematic eye models and related thick lens calculations in geometrical optics. Basic optics of ametropia and refractive correction using thick lens theory.

Methods include lectures, laboratory practical work, discussion in class and laboratories; problem-solving exercises within class and homework; applets and web based video; computer-based calculations, modelling and ray tracing techniques; text books and programme notes provided on the virtual learning environment; self-directed learning.

Module Content & Assessment
Assessment Breakdown %
Formal Examination20
Other Assessment(s)80