Jul 7, 2021
Optical Zoom based on Alvarez Freeform Elements
An Alvarez Zoom is an amazing optical system where the optical zoom is provided by a lateral shift of freeform lenses. This blog post explains the main principles of the Alvarez Zoom lens and includes a demonstration of an Alvarez Zoom lens calculation and modelling in Zemax OpticStudio.
Luis Walter Alvarez (June 13, 1911 – September 1, 1988) was an American experimental physicist, inventor, and professor. He was also a 1968 Nobel Prize laureate in Physics.
Variable power lens without undue distortion had been widely perceived as highly desirable and extensively applicable but despite prior art workers’ failure, Alvarez had managed to come up with a variable-power lens and system.
His patent (US3507565A 21.04.1970) has long since expired but DynaOptics has carried on his torch with our freeform lens technology.
What is the Alvarez Zoom lens?
One probably knows how traditional zoom lens works. We have several groups of lens elements in an optical system, which move along the optical axis along predefined trajectories providing a variation of resulting focal length (zoom factor) of the optical system.
In the case of Alvarez Zoom Lens, we have pairs of so-called Alvarez lenses and the lateral shift of these lens elements concerning each other provides a variation of the focal length of the optical system.
The main difference between the conventional zoom lens and Alvarez zoom lens is that conventional system lenses are moving along the optical axis while Alvarez system lenses are moving in a perpendicular direction to the optical axis. Because of this feature, Alvarez zoom can be useful in slim applications like smartphones.
Fig. 1 Conventional Optical Zoom lens (left) and Alvarez Zoom lens (right)
How Alvarez pairs work
To understand how Alvarez zoom works at first, we should look at Alvarez pairs. Each Alvarez lens is a freeform optical element with only one plain of symmetry.
Fig 3. Alvarez pair (picture from www.spiedigitallibrary.org)
As one can see in the picture below, each Alvarez pair represents an optical element with optical power variation. The lateral shift of Alvarez lenses in each pair changes the optical power of the Alvarez pair.
Fig 4. General working principle of an Alvarez lens pair.
Fig 2. General representation of Alvarez Zoom and its comparison with Conventional Optical Zoom
The core of our Alvarez zoom lens is an afocal Galilean system. The first Alvarez pair represents the objective lens of the Galilean system, while the second Alvarez pair represents an eyepiece lens.
To learn more, read the full knowledge base article:
Authors: Ted Churlyaev, Vadim Vlakhko, Li Han Chan (DynaOptics LCC)
Patent US10082652B2“Miniaturized optical zoom lens system”https://patents.google.com/patent/US10082652B2
Paul J. Smilie, Thomas J. Suleski, Brian Dutterer, Jennifer L. Lineberger, Matthew A. Davies,“Design and characterization of an infrared Alvarez lens”. https://www.spiedigitallibrary.org/ContentImages/Journals/OPEGAR/51/1/013006/FigureImages/OE_51_1_013006_f001.png