Updated July 2020.

Most visual imaging applications require a well-focused image at a range of distances. Traditionally, good focus at multiple depths required either using large lenses with a suitable depth of field, mechanically-driven zoom, or auto-focus lenses.

More recently, tunable lenses have been introduced to the market, and these have many advantages compared to traditional ones. They are smaller, faster, and more compact than traditional autofocus designs. Tunable lenses are also increasingly used in machine vision products, handheld devices, and microscopy applications.

In previous projects, Optics For Hire designed optical systems that integrate tunable lenses. In the most recent one, tunable lenses were installed in the barcode reading device. There are several approaches to consider when searching for a tunable lens, including electro-optical, electro-mechanical, and acousto-optical techniques. Below, we present three of the best-known approaches and explain how they work.

1.) Varioptic (owned by Corning) produces electro-optical tunable lenses (Figure 1) based on the electro-wetting principle. Lenses are liquid, and the unit consists of a sealed cell containing two liquids with different refractive indices. By applying an electric field, the curvature radius of the meniscus between the two fluids changes, resulting in a change in the lens focal length.