Steampunk Eye with Varying Lens

Steampunk styled artificial eye whose lens changes shape. A collimated light beam enters the eye from the brass lamp at the left. The path of the light through the eye is shown as a series of sections (bright green). The animation starts with the eye focused at infinity (the beam is focused on the retina at right). As the lens becomes fatter (its curvature increases), so the light beam is focused closer to the lens. In this animation, the curvatures of the lens and cornea, and the relative sizes of the various ocular components, closely match those of a real eye. This is a simulation in which the computer calculates the paths of the rays. The main simplification is the absence of an aqueous and vitreous humour. I have adjusted the refractive index of the lens to take account of that.

This change in lens shape is how the eye accommodates to focus on near and distant objects. When relaxed, the lens has minimum curvature and focuses on infinity. This means that parallel rays (as in this simulation) are brought to a focus on the light sensitive retina. For close objects, whose rays diverge, the lens must become more powerful (its curvature increases).