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The 3 Types of Smart Sensors For Inline Quality Control

The 3 Types of Smart Sensors For Inline Quality Control

LMI offers 3D smart sensor products based on both laser triangulation and stereo structured light technologies. We have categorized these products into three main sensor types: point profile sensors (1-dimensional, measuring in Z), line profile sensors (2-dimensional, measuring in X and Z), and snapshot sensors (3-dimensional, measuring in X, Y, and Z). Although each type measures the 3rd dimension (or Z axis), some require moving the object to get the other dimension (eg., X or Y). Let’s take a closer look.

Point Profile Sensors 

Profile sensors are the speed demons of the 3D smart sensor family. Using a single laser point, these sensors are able to scan at very high speed (32 kHz). The scan data can be used to 1) inspect displacement in a fast moving process or 2) build a contour or profile along the direction of part travel using built-in buffering logic.

Point profile sensors are typically used to take dimensional and contour feature measurements of parts moving at very high speed in an inline process (such as assembly line), or in closed-loop feedback systems where the sensor is required to generate simple pass/fail decisions based on a single feature or tolerance (e.g. thickness) for the purpose of quality control.



Line Profile Sensors 

As the name implies, line profile sensors project a line of laser light onto an object to measure the contour or profile of the surface. Similar to point profilers, line profilers can buffer many cross-sectional profiles of an object to generate a full 3D point cloud for volumetric or 3D feature inspection.

A line profile sensor can measure the shape of very small (10 mm) to large width objects (1.5m) moving at high speed. In addition, line profilers can simultaneously output calibrated 2D intensity images for use with common 2D imaging libraries for inspection based on surface markings.



Snapshot Sensors 

Snapshot sensors are different from laser-based sensors in that they use blue LED structured light as their projection source. Snapshot sensors leverage stereo camera technology to capture the reflection of sinusoidal patterns projected onto the target surface in order to generate a 3D point cloud. The sensor uses built-in 3D measurement tools to measure volume or specific 3D features. 


Snapshot sensors are ideal for inline inspection applications where the target is momentarily stationary (eg., 100 ms), such as in in robotic inspection or pick and place.

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