Eva's accuracy

17/04/2013

We don't throw around empty promises here, at Artec. Our technical specifications were not one-time, laboratory achievements. From now on, every Artec Eva 3D Scanner will come with a certificate of accuracy which complies with well-known and respected VDI/VDE standards of testing.

When you purchase a scanner, you are provided with a certificate that vouches that this scanner was factory-tested and achieved, at least, 100 micron point accuracy, as is outlined under VDI/VDE 2634 guidelines.

What have we been up to?

Over the past several years, we have been working on improving the accuracy and repeatability of our hardware. In November of last year, we told you about our temperature adjustment algorithm (more on that further down). It significantly improved accuracy over time/distance, because the scanner data was no longer affected by internal temperatures of the scanner. We have also been working on improving factory calibration procedures, as well as perfecting mutual distortion correction of the camera and projector. 

The testing and the certificate.

Each certificate will show the results of testing for each particular scanner. The reference object (a plane with 5 semi-spheres) is scanned and the screenshots are provided in the certificate itself. You will be able to see that the error in one frame is within the allotted 0.1mm (2 Sigma). This test is performed at a distance of 600mm from the object.

Moreover, work has been done on improving some of the image filtration algorithms. This means that the semi-spheres are better identified and accurately displayed. Each certificate contains measurements between spheres and the radius of each sphere. Only scanners who show less than 0.16 mm error will pass QA (3 Sigma).  

More about temperature control (more geeky info) and the question of accuracy over distance

The fact that Eva comes with an on-board temperature gauge means that we can correct temperature fluctuations through software. Theoretically, and this is true for all scanners on the market, in order to get the most accurate results, you should scan while the internal temperature of the scanner is exactly as it was during factory calibration.

Think about this: just a five degree difference between internal temperature during calibration and while you scan, can cause the camera to shift by up to 30 microns. This, in turn, can lead to an error of up to 0.3mm in each frame. This means on a 1 meter object, you can accumulate a 1.5mm error!

Our goal was to eliminate this error. We don't want our customers to wait until the scanner heats up or cools down. We don't want you to think about this issue at all. Who really knows what the temperature is like inside that thing?

That's why we developed the temperature algorithm mentioned earlier. The software monitors the internal temperature and adjusts the results accordingly, so that the error is significantly reduced. We tested a batch of scanner and found that over one meter, the scanner accumulates no more than 0.3mm (1 Sigma). The reference object which we tested on, was first measured with the help of a CMM with claimed accuracy of 7 microns.

That's the story! Every scanner will come with a certificate of accuracy. You will be able to download it from your account at my.artec3d.com. If you want more info, definitely send us a note. We love hearing from you.

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