First, a little optics jargon for those not familiar. We refer to zoom lenses, but then we end up assigning three or four definitions to the word "lens". A lens is an single optical piece; usually glass, sometimes plastic, with curves on one or both of its surfaces which combine with the optical characteristics of that piece to change the path of light through the lens. A conventional, single power (that is, not adjustable magnification) rifle scope has a front objective lens, usually a sandwich of more than one lens called an achromatic lens, and a combination of lenses at the back which magnify the image produced by the objective, and some piece of optics to make the image upright (simple telescopes invert the image). A zoom rifle scope, like this Nikon 3-12x42, is a telescope with with a great deal of features built in; lots of glass and lots of moving, very precise parts.
Conventional zoom telescopes like that Nikon work by mechanically moving pieces of the system. As anyone who has used a rifle scope will know, you usually do this by rotating or moving part of the scope (usually the eyepiece end on the ones I've seen). Photographic zooms change their overall physical length. Since rifle scopes tend to be filled with Nitrogen to keep moisture out and prevent fogging, the seals make changing overall length is much more difficult.
Sandia's new rifle scope is called the RAZAR: Rapid Adaptive Zoom for Assault Rifles. The RAZAR uses a totally new system; it changes the shape of the lens instead of moving it, adjusting its focal length and magnification that way. The lenses that are changed are filled with a fluid and the polymer package is compressed or released with an electronic adjustment, changing the focal length to zoom in or out at the push of a button. Instead of needing to remove the scope from their eye and turn the adjustment, the operator pushes one of two buttons. The RAZAR is based on:
Check out the video and notice the targets they test resolution on at around 2:50.
- A polymer lens core has two flexible, hermetically sealed membranes, which encapsulate a polymer fluid. The three-quarter-inch lenses are aligned with glass lenses to complete the optical design.
- A piezoelectric actuator electro-mechanically changes the flex of the lenses, achieving the correct position within 250 milliseconds to an accuracy of 100 nanometers, about 1/100th the thickness of a human hair. These actuators operate the way the muscles of the human eye change the curvature of the eye’s lens to focus far away or up close.
- Variable-focal length system design tools had to be developed from scratch, including analytical expressions and computer models that trace rays of light through optical systems.
Dr. Brett Bagwell was the leader behind this effort, but it relied on others going back over the years. The project started in '05/'06, and involved both Sandia and private contractors. Dr. Bagwell got to show the scope to USOC in 2012.
“The guys picked it up and when they pushed the button and it zoomed, and then instantly it zoomed back out, they were like kids at Christmas. There was this look of astonishment and pleasure,” he said. “That’s very gratifying. Here’s this grizzled veteran looking at me like I’ve just created magic.”The expected battery life is 10,000 focus actuations on a pair of AA batteries. This technology looks like it could be a game changer in the rifle scope world. There isn't a hint in that piece of what this costs, but keep an eye out for it in the coming years.
*When I said, "This invention is a completely new way of creating zoom optics...", that isn't exactly true. Adaptive deformable optics like this have been around for a while, but they haven't been this good and they tended to be more useful for infrared optics, due to the longer wavelength. This is a big improvement.