A 3D scanner turns a real object into a digital model you can edit, print or measure. But how do 3D scanners work, and why do some capture a coffee mug perfectly while others struggle with a shiny car part? It depends on the method they use to measure the surface.
In short, most scanners either project light onto an object and watch how it bends, or they take many photos and let software work out the shape. Each approach has strengths, so let’s look at the main types before you buy.
Structured light scanning
A structured light scanner projects a pattern, such as stripes or a grid, onto the object. One or more cameras watch how the pattern bends over curves and edges. Using that distortion and basic geometry, the scanner calculates the position of thousands of points on the surface.
The payoff is speed and detail. A scan can take seconds, and it captures fine surface features. It’s a popular choice for small and medium objects like figurines, tools and parts. The trade-off is that it can struggle in bright sunlight, since the room light can wash out the pattern.
Laser scanning
Laser scanners project a thin line or dot of laser light and use a camera to measure where it lands. Because the angle between the laser and camera is known, the scanner can work out distance, a method called triangulation. Move the line across the object and you build a complete surface.
Most consumer scanners use low-power lasers, but it’s smart to check the laser class and never stare into the beam. Some devices, such as LiDAR, instead time how long light takes to bounce back, which works better for large spaces like rooms. Laser methods often handle varied surfaces well and can reach good accuracy, though they can be slower than structured light on detailed parts.
Photogrammetry
Photogrammetry needs no special scanner at all. You take dozens or hundreds of overlapping photos from different angles, then software finds matching points across the images and builds a 3D model. A phone camera can do it.
It’s affordable and great for large or outdoor objects and textured surfaces. On the other hand, it takes computer time and patience, and smooth or featureless surfaces are hard because there’s nothing for the software to match.
What can each method capture?
Different tools fit different jobs, so think about your target first.
- Small detailed objects: structured light, for crisp surface detail
- Medium parts and body shapes: structured light or laser handheld scanners
- Large objects and rooms: LiDAR, laser or photogrammetry
- Colorful textured items: photogrammetry and many structured light units capture color
Whatever you pick, expect trouble with shiny, transparent and very dark surfaces, since they reflect or absorb the light in unpredictable ways. A light dusting of scanning spray or powder often fixes that, and most types wipe or wash off (check the product’s directions).
What should you look at when buying?
Resolution and accuracy are the headline specs, but they mean different things. Resolution is how closely spaced the captured points are. Accuracy is how close the model is to reality. Also consider scan area, whether the scanner is handheld or sits on a turntable, software quality and how much computer power it needs.
If you’re just starting out, our guide to the best 3D scanners for beginners explains which features matter. On a tighter budget, see affordable 3D scanners, and if you’ll be scanning away from your desk, check the roundup of portable 3D scanners.
The finished scan is a mesh that often needs cleanup, filling holes and trimming rough edges, before it’s ready for printing. If you’re picking a printer for those models, our comparison of FDM and resin 3D printing may help.
Tips for getting a cleaner scan
Whatever scanner you pick, a few habits make scans better. Scan in even, indirect light, since harsh shadows and bright sun confuse the sensors. Keep the object still, or place it on a turntable with a plain background. Overlap your passes so the software has enough shared points to stitch the pieces together.
It also helps to add temporary markers or place the object on a patterned mat when the shape is simple and smooth, because flat, repeating surfaces can make the scan drift. Take your time on the first few tries. Most people improve quickly once they see how the software reacts.
Frequently asked questions
Can I use my phone as a 3D scanner?
Yes. Photogrammetry apps use your phone’s camera, and some phones also have LiDAR sensors. Results are good for larger shapes, though fine detail is better with a dedicated scanner.
Why does my scanner fail on shiny objects?
Shiny and transparent surfaces bounce light away or let it pass through, so the scanner can’t read them. A thin coat of removable matte scanning spray usually solves it.
Is a 3D scan ready to print right away?
Usually not. Scans typically need cleanup in software to fix holes and noise. Plan on a bit of editing time after each scan.
The bottom line
Structured light is fast and detailed, laser methods are flexible, and photogrammetry is cheap and good for large subjects. Decide what you want to scan, then choose the method that fits. With that in mind, the guides above can help you narrow down a model.