U.S. Army weapons officials are testing a sophisticated rifle-scope that let's shooters zoom in and out on near and far targets faster than ever before.
Brett Bagwell, a former Army Special Forces officer, has developed what's known as the Rapid Adaptive Zoom for Assault Rifles, or RAZAR, scope, using a patented active optical zoom system, called "adaptive zoom."
Traditional optical zoom changes magnification by adjusting the positions of the lenses along the optical axis in the same way a 35-mm camera mechanically moves the lenses as you zoom in on or out on a subject.
Adaptive zoom changes the focal lengths of two or more lenses by varying the curvature of the lenses' surfaces to provide optical zoom without changing their overall positions relative to one another. This allows the user to view either a wide-angle image or zoom in on an area of interest with a compact, low-power system, according to a recent Army news release.
"The impetus behind the idea of push-button zoom is you can acquire what you're interested in at low magnification and – without getting lost – zoom in for more clarity," said Bagwell, now an optical engineer with Sandia National Laboratories.
Bagwell began work on RAZAR in 2006 responding to the military's interest in a compact zoom riflescope that could rapidly toggle between magnifications. Early work had been funded by Sandia's Laboratory Directed Research and Development program, the release states.
It took years to meet the military's power usage, speed and accuracy requirements, Bagwell maintains.
"As an engineer, I was impressed with our progress," Bagwell said. "But as an operator, I was constantly dissatisfied. We had to make it smaller. We had to make it lighter. It's got to toggle faster."
Representatives from U.S. Special Operations Command first tested the RAZAR in late 2012 at Camp Atterbury Joint Maneuver Training Center near Edinburgh, Indiana.
"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," Bagwell said.
"There was this look of astonishment and pleasure. That's very gratifying. Here's this grizzled veteran looking at me like I've just created magic."
RAZAR'S adaptive zoom technology -- invented by Sandia optical engineer David Wick – relies on three core technologies.
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.
Adaptive zoom accomplishes true optical zoom -- as opposed to digital zoom -- by changing the focal length of two or more lenses in concert, without the normal mechanical motion, reducing the size and power requirements of the zoom lens, Wick said.
The theory that underlies zoom scopes hadn't changed significantly since the 1960s, until the adaptive zoom technology came along, according to the release. Using adaptive zoom, Sandia's team worked for 18 months to achieve an optical quality of about half a wavelength of light.
Sandia had to perfect the manufacturing process of the lenses so the quality of the prototype could be replicated. When the polymer is sealed, no air bubbles or specks of dust could remain in the lenses or on the surrounding rings, Bagwell said.
Freddie Santiago, who at the time was a doctoral candidate in physics and in Sandia's Student Internship Program, developed the process for making the lenses.
"You have to start from the basics: How do we make the polymer? How do we stretch the polymer and make it an optical surface? We had to understand the process, from mixing the polymer all the way to the final product and we had to do it in a systematic way," Santiago said.
Many of the technologies and designs that make up the riflescope came from mechanical engineers, robotics experts, chemists and other Sandia experts, but Bagwell went outside the labs for the actuator to flex the lenses, seeking help from Dynamic Structures and Materials, LLC, a small business in Franklin, Tennessee.
Matthew Stefanick, who was the company's lead engineer on the project, said the team used an ultrasonic piezo motor to actuate the flex in the lenses. A voltage is applied at an ultrasonic frequency to vibrate and move a rotor and lead screw, which causes the lens to flex.
Stefanick said the decision to use an ultrasonic motor provided a key feature, a "zero-power hold" that maintains the last selected focus, even if the power is lost.
The feature allows users to complete 10,000 actuations on two AA batteries, Bagwell said.
John Heinsohn, project Manager Soldier Weapons called the RAZAR a "monumental achievement."
"This is a leap-ahead technology," Heinsohn said. "What this liquid lens technology allows us to do is take something that could be as big as our current optics and increase the performance – five, 10-fold."
Michael Squire, a former sergeant first class with Special Operations Research Support Element, said the ability to zoom between near and far targets within seconds, without taking his hand off the weapon, is "game-changing."
"The difference that can make, especially with somebody shooting back, could mean life or death," he said.
-- Matthew Cox can be reached at firstname.lastname@example.org