Glossary · Processes

3D printing

Structured light (fringe projection)

A scanning method in which a pattern of stripes or dots is projected onto the object. From the distortion of the pattern, the scanner calculates the shape.

Explained in more detail

A projector casts a known pattern onto the object, and one or more cameras see how it bends on the surface. From the angle between projector and camera, the software calculates the distance of each point, a method called triangulation. Because many points are captured at once, structured light is fast and tolerates movement, which is why it is the most common technique in handheld scanners. Blue light is used for fine detail on small objects, while invisible infrared does not dazzle and suits scanning people. Ambient light can interfere.

Where does the term come from?

Structured here means that the light carries a known pattern instead of shining evenly. In measurement technology the method is also called fringe projection.

In practice

• Dark, glossy and transparent surfaces disturb the pattern. A thin, matt scanning spray helps.
• For people, use the infrared mode; it does not dazzle.
• Soft room light or daylight is usually enough; direct sun and harsh lamps cause reflections.
• Many hybrid scanners combine structured light with blue laser lines. Choose the mode according to the object.

Not to be confused

Structured light and laser lines both work with triangulation. Structured light illuminates an area with a pattern. Laser scanners project a few thin lines, which are captured more precisely, but they almost always need markers for this.

Frequently asked questions

Is structured light more accurate than photogrammetry?

As a rule yes, because the scanner knows its pattern and the position of projector and camera exactly. Photogrammetry has to work all of that out from the photos.

Do I need markers with structured light?

Often not, as many scanners orient themselves by the shape and texture of the object. For smooth, uniform parts, markers still help to stitch the individual scans together cleanly.