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31 Jul 2006
A piezoelectric motor developed in the US is proving its worth as optical zoom and autofocus modules continue to shrink in size.
A miniature linear motor developed in the US is shaping up to be a big hit with camera phone makers as the industry switches from fixed optics to moving lenses. Based on a vibrating nut and threaded rod, New Scale Technologies' compact mechanism allows engineers to shrink optical zoom modules into a 10 x 10 x 20 mm sized package.
"Our greatest challenge is keeping up with the market's demand for smaller and smaller components," New Scale president David Henderson told optics.org. "In the past two years, we have reduced the motor's diameter by a factor of five and its length by a factor of three."
Today, the motor measures just 1.55 x 1.55 x 6.00 mm and has a resolution of 0.50 µm and a stroke of 10 mm. Dubbed SQUIGGLE, the unit can be driven at speeds of up to 5 mm/sec and suits battery operation. According to the firm, the motor's simple design helps to eliminate around 90 percent of parts found in a classic camera mechanism, such as gears, cams, barrels and levers.
At the heart of the motor is a miniature nut that surrounds a threaded rod. Four piezoelectric plates, arranged in pairs, intermittently bend the nut and cause the rod to advance and retract within the device. Plates can be driven by either sinusoidal or square waveforms (40-200 kHz). Applying a positive 90 degree phase shift between the pairs of plates produces forward movement and a negative 90 degree phase shift drives the rod in the opposite direction.
As Henderson revealed, the rapid pace of miniaturization has put pressure on the small firm's resources. Fortunately, the struggle could prove to be extremely profitable for the company, which was only founded in 2002.
"Our newest and smallest motor is at the right size for some very high-volume applications," explained Henderson. "The need for auto focus and optical zoom in cell phone cameras has created a new market for 1 billion motors per year."
Autofocus camera modules measuring 8.5 x 8.5 x 6.1 mm and equipped with 2 megapixel sensors are due to be introduced this year and optical zoom modules are set to follow soon after.
Author
James Tyrrell is News Editor on Optics.org and Opto & Laser Europe magazine.
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