You might be asking yourself should I buy a 3D scanner that uses targets? Or maybe you’re evaluating the pros and cons of 3D scanners that utilize targets. We offer both technologies at TriMech and understand the benefits of each. In this article, we will cover why targets are necessary for some scanners and not others, and tips for using targets to make the process quick and easy.
What are 3D Scanning Targets?
Targets are small markers that are applied or located within a scanner’s field of view to help with data registration. The actual target is the smaller white or silver (retroreflective) circle within the black background, which provides a high contrast, making each target easy for the scanner to see.
Targets are used for several reasons, but the main reason is tracking. Tracking is the scanner’s ability to calculate the relative movement of the scanner and subject, but they’re also used for defining geometry and speeding up the alignment of scan data. They are available in different sizes, depending on the resolution and field of view of your scanner.
Without tracking, scanning software wouldn’t know where each new chunk of data should go. The scanner needs to see at least three targets at a time to track movement, but additional targets allow the software to check the calculation. For stationary scanners like the Zeiss Atos Q and GOM Scan 1, targets are used to link each scan frame and transform the data. For laser handhelds like the T Scan Hawk II, the targets on or near the subject are used to triangulate the position of the scanner as it moves relative to the sample.
Targets can also be used to define geometry in the scanning scene. One common implementation of this is deleting background data. When scanning with an automated turntable, ZEISS Inspect Optical 3D will detect the targets on the top of the turntable and use them to define a plane. This plane can be shifted up or down as needed to eliminate the turntable. When handheld, with the T Scan Hawk II, operators typically carry a small card with a few targets on it. When prompted, the card can be added to the scene, defining a plane. Data below this plane is automatically deleted.
Finally, targets can be used to speed up the alignment of scan data. When scanning, we are often required to position the part in multiple orientations to capture all the surfaces of the part. By placing a few targets in areas of the part that are captured in all positions, those targets can tell the scanning software how to re-orient data to match the first position. While this can also be simulated by the operator manually selecting overlapping points on the data, target alignment is automated and speeds up the scanning process.
How do you 3D Scan without Targets?
Some scanners, like those from Artec, including the popular Leo wireless handheld 3D scanner, do not require targets. Artec scanners instead use a combination of captured geometry and greyscale color to track across the subject. This is created for objects with many features but struggles with simple or repetitive samples.
For example, a plywood sheet scans easily – the woodgrain has enough color variation for the scanner to track. A complex carving is easy because the geometry is unique across the part. However, a metal tube can be difficult, because no matter how much you move, the geometry and color that the scanner sees remain the same. For this type of part, we recommend adding complexity to the scene. This can be as simple as creating unique marks, like the $ sign on the part with a whiteboard marker since it’s easy to remove.
5 Ways to Ease the Pain of Targets
When we’re discussing 3D scanning and applying targets, we often hear remarks such as “I hate those stupid dots!”. These concerns usually stem from the time spent installing and removing the markers from the object. We have 5 solutions for you to make using scanning targets quick and easy.
If your scanner requires targets, you can save time and money by using these tips:
1. TARGET CLUSTERS: Try these reusable target clusters that are filled with targets. For example, Aesub “Dices” are prisms that have targets visible from five sides, with a magnetic or threaded base. These prisms allow you to quickly stick 10 targets at a time on a part and remove them just as easily. Zeiss makes a similar product, their Magnetic Reference Pillar Set, which contains both long and round prisms. Both shapes contain magnets, their manual turntable is steel to quickly attach the pillars to.
2. TARGET NET: To cover a large area quickly, consider a target net. With 300 targets on a 1.5m x 2m Aesub Target Net, you can prepare things like automotive body panels in seconds. Each node in the net has a magnet and a target.
3. HOMEMADE TARGETS: Alternately, make your own! Target artifacts can easily be 3D printed, allowing customization for your specific needs. Recently, we took a trip to a hardware store and bought some metal strips. At 4’ long, and covered in targets, we can now place targets along the part in just a few seconds.
4. TARGET JIGS: Target frames or custom jigs – for repetitive scanning jobs, like production quality control, where you scan the same part many times, target frames and jigs are a huge timesaver. Target frames are modular kits that allow you to build a box around your part, covered in targets, through which you scan. For an even more permanent solution, a printed fixture allows parts to be dropped in and scanned. These jigs can be detected by software for quicker processing, too!
5. MAGNETIC TARGETS: Use reusable magnetic targets – magnetic targets are a great time-saver for scanning steel parts. They apply quickly and can be removed more easily than adhesive targets. There is also less risk of leaving residue or damaging delicate painted parts.
Still have questions?
Using one of these devices will help reduce the time spent on setup and breakdown during the scanning process. We hope that you found this article helpful. If you would like to speak to someone on our scanning team to talk through which scanning technology works the best for your parts? We offer free scanning consultations and product demos. Click here to learn more about our 3D Scanners.