Guide
What is a laser profilometer?
A laser profilometer projects a straight line of laser light across a part and watches it from an angle with a camera. Because the camera sits off to one side, the line appears to bend wherever the surface rises or falls. That bend is measured and converted into a cross section, thousands of times a second. Move the part or the sensor along, stack the cross sections, and you have a 3D surface.
Also called: laser line scanner, laser profile sensor, 2D/3D laser scanner, 2.5D laser, XZ laser, laser stripe sensor, sheet of light sensor, line profiler, laser triangulation scanner, contour sensor, laser gauge, profile scanner, blue laser scanner, weld seam tracker, 3D snapshot sensor
How it works
The technique is called laser triangulation. The laser, the surface and the camera form a triangle, and the geometry of that triangle turns an apparent shift in the image into a real height. A single point sensor does this with one dot. A profilometer does it with a whole line at once, typically 800 to 3200 points per profile.
What to check before you buy
- Field width at your working distance, not the headline number. The line gets wider the further away you are, and the resolution gets coarser with it.
- X data interval, which is field width divided by point count. This is the smallest feature you can resolve. A 150 micron interval will not see a fine chamfer.
- Z range and standoff. Z range is how much height variation you can capture, standoff is how far the sensor sits from the part.
- Z repeatability, which is how much the same measurement wanders when nothing has changed.
- Scan rate at full profile output. Headline rates are usually quoted on a cropped region of interest. Always ask for the number at the full point count.
- Laser wavelength. Blue at 405 or 450 nm holds a stable reading on hot, red, or organic surfaces where a red laser scatters.
- The software. This is the one most people forget. A configurable measurement toolset lets a technician set up an inspection. An SDK and a point cloud stream means you need a programmer.
Published free, no form. If a supplier will not answer one of these in writing, that is worth knowing before you order.
Common confusion
A laser displacement sensor measures one point and answers questions like how far, how thick, how much runout. A laser profilometer measures a whole line and answers questions about shape: is this weld bead the right height, is this edge formed correctly, is there a dent. If you can describe the measurement as a cross section rather than a single number, you need a profilometer.