What is an IMU?

You may have noticed that the Revopoint POP 3, among other things, is packing an inertial measurement unit, commonly shortened to IMU, inside it. So, IMUs aren’t exactly new technology, having been around since the 1940s and even used in the Apollo missions to help guide the rockets. But, like many technologies, they have shrunk to small chip sizes over time, which has helped them spread across a whole gamut of devices, from drones to your phone to even Nintendo Wii controllers.

So let’s look at what’s an IMU and how it helps POP 3 scan better.

What Do IMUs Do?

In a nutshell, IMUs are used to track position, orientation, and velocity. And devices with an IMU typically use this data for navigation as it helps a device know where it is. Or if you’ve ever checked your step count on your phone, this data was likely obtained from the device’s IMU, which recorded the phone’s motion as you walked.

How Does It Work?

Inside the IMU are tiny gyroscopes, accelerometers, and sometimes magnetometers to measure angular attitude, acceleration, and magnetic field, respectively. In POP 3’s case, there are 9 sensors, one of each for each axis, to detect the pitch, roll, and yaw as you move POP 3. Then an algorithm analyzes this data to determine the scanners’ speed and direction.

Gyroscopes

Measures the angular attitude of POP 3. The tiny gyroscopes in an IMU work through small masses vibrating with an equal amount in opposite directions. Then the Coriolis forces acting on the masses determine the angular attitude.

Accelerometer

As the name suggests, this measures the acceleration of a device as you move it. It does it by using something called the Piezoelectric effect, which uses microscopic crystal structures to generate a voltage when they vibrate. And the level of voltage generated indicates the acceleration occurring to the device.

Magnetometer

Otherwise known as an electronic compass, it measures the strength and directions of the Earth’s magnetic field. And are in IMUs to provide a point of reference that the gyroscope and accelerometer use to compare their results against. This helps to prevent the IMU positioning from drifting too much. However, even with the help of a magnetometer, IMUs still sometimes need to be recalibrated to maintain accuracy.

How Does an IMU Help a 3D Scanner?

POP 3’s IMU helps you scan in a few ways. Firstly, it helps to smooth the frame stitching as you scan because now the scanner knows its precise position for each capture frame, making it easier to stitch the frames together accurately by checking their positional data.

Secondly, POP 3 is better at dealing with shaking and being moved too quickly when scanning by hand because it can use the IMU data to work out if it’s in an unexpected position caused by either of these and then delete the faulty frames caused by it.