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Small mirrors, major advances

The micromirrors may be tiny, but they will have great significance for the future. Photo: Karolina Milenko / SINTEF.

SINTEF is developing tiny steerable mirrors that can be used for everything from taking accurate 3D images of Mars, to wireless charging and LiDAR applications in autonomous vehicles. The micromirrors are very small, but their future significance will be enormous.

Researchers at SINTEF are developing small, mobile mirrors made of silicon – the same material that we use to make for example solar cells and microprocessors in our computers.

We recently used a micromirror to take accurate 3D images as part of a project for the European Space Agency (ESA), which needs a compact and very accurate 3D camera for use on Mars. We used the mirror to create a variety of different patterns using a laser beam. By decoding changes in the patterns, we captured 3D information to an accuracy of less than 0.1 mm, or slightly greater than the width of a human hair.

Micromirrors to Mars 

Factors such as size, weight, speed, robustness and energy consumption are key to the use of micromirrors in space. Size and weight matter because it is very expensive to send anything to Mars. Speed is key because it is vital to take 3D images rapidly in order to guide sample collection in real time or observe objects in motion.

The mirrors can be moved with the aid of piezoelectric materials, which trigger movement when a voltage is applied. Since movement is integrated into the mirror elements, no external motors are required, making them more durable and able to withstand more stress. Moreover the mirrors have extremely low energy consumption and have a small footprint.

Low energy consumption makes our technology highly competitive. This is important because in space you can’t just plug your device into the mains. Such considerations are also important in other sectors. For example, autonomous drones fitted with sensors also have to operate for long periods before recharging their batteries.

Micromirrors with multiple applications 

There is a link between the size of micromirrors and how fast and how much they can move. Increasing one of these parameters normally means a reduction in the other. At SINTEF we make mirrors across most of this parameter space, including fast and rigid mirrors with resonance frequencies of about 10 kHz, as well as those with large deflections and lower resonance frequencies of a couple of hundred hertz.

We are also looking into other micromirror applications. One example is their use in wireless optical communications, where they are used accurately to guide laser beams that enable high-speed optical communication without the need for a costly optical fibre infrastructure. Another is their use in laser-based wireless charging. Here, micromirrors are used to focus the beam onto the target device that requires charging, such as a wireless sensor. Charging commences when the beam establishes contact.

Micromirrors have many other exciting applications for future technologies. For example, they are important components of LiDAR systems. LiDAR is an optical remote measurement technique used to obtain rapid measurements of the location of, and distance to, physical objects such as autonomous vehicles. They may also be important components of low-energy projectors such as those used in augmented reality (AR) and virtual reality (VR) headsets.

Contact us if you have any questions about how you can use micromirrors in your business.

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