business profile curve a smooth upward
Warren Clark tracks the history of interferometry specialist 4D Technology
T
he roots of 4D Technology can be traced back to 2000, when the company 4D Vision Technology was formed in Irvine, California, as a spin-off from Metrolaser.
4D’s primary goal at the time was to commercialise dynamic interferometry technology. Founder and president James Millerd says: ‘We had developed a technique that allowed us to make interferometric measurements in one shot. It was a technique, we felt, that would enable us to expand the market for interferometry.’ Interferometry techniques had previously
required both the instrument and the object to be isolated from vibration. 4D’s new technology removed the need for vibration isolation – and, moreover, it later created a product that could take a measurement from an object that was intentionally moving, such as an active optic or spinning hard drive. Proof that 4D was aiming high came with the identity of its first major customer – NASA. ‘They were looking at a large space telescope mirror,’ recalls Millerd. ‘At the time it was a feasibility programme, but it eventually became part of the James Webb Space Telescope. They had a very specific requirement in that they wanted to take the interferometric measurements in a vacuum chamber. This was a very difficult thing to do, with a long stand-off and lots of vibration. Our technology was a really good match for what they wanted to do, so we developed our first system specifically for NASA.’ The transition from 4D Vision Technology to
4D technology’s dynamic interferometers provide vibration insensitive measurement of optical surface roughness, form and shape. left to right: nanoCam sq Dynamic profiler, fizCam 2000 Dynamic short Coherence interferometer, phaseCam 6000 Dynamic interferometer
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4D Technology began in 2002, when Millerd met up with Dr Jim Wyatt and Dr John Hayes, the founders of metrology specialists WYKO, which they had recently sold to Veeco Instruments. ‘At the time, Jim was Dean of the College of Optical Sciences at the University of Arizona, and he and John were interested in getting back into the metrology business,’ says Millerd. ‘They saw the benefits of what we were trying to do, so they set up 4D Technology in Tucson, Arizona, and immediately acquired our California operation, which we moved to Arizona.
eleCtro optiCs l March 2011 James Millerd
‘It was a great move for us, as we immediately had all their expertise close at hand, and they had experience in developing commercial systems. One of the first things we did under the new arrangement was develop supporting software from the ground up, using some of the former WYKO team.’ 4D’s earliest products were based on a holographic grating, which split the beam into various components. ‘This technology worked fine,’ said Millerd, ‘but it had limitations, particularly when used with broadband light.’ In 2004, the company introduced a new method – pixellated phasemask technology. This used micropolariser filters over a CCD camera. ‘This had several advantages for us,’ says Millerd, ‘not least of which was reducing the size of the overall assembly from around 10cm down to a matter of a millimetre or so. It also allowed us to work with a number of different light sources, and subsequently begin work on a new range of products.’
In traditional interferometry, a series of images is taken very quickly, with a small phase shift in between each image in order to make a quantitative measurement. ‘Our concept was to acquire all this data in a single shot,’ says Millerd. ‘Originally, with our holographic grating solution, we divided up one image into four images on a single sensor. We now use our pixellated concept, which provides spatially multiplexed data.’ The advent of the pixellated technology led to the launch of several new product variations, including aperture sizes ranging from 300mm down to sub-millimetre, and wavelengths from blue to infrared. The size and shape of the object being measured dictates the choice of model required.
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