One of the advantages of using Gocator 3D smart sensors is the ability to produce 2D intensity images that measure the amount of light reflected by an object. Intensity (or greyscale) images are generated as a byproduct of the laser triangulation process and prove highly useful for applications where visual defects need to be identified, such as barcodes or surface markings.
Laser Triangulation, Gaussian Curves and Centroids
The most common method of 3D point generation used in laser triangulation is to project a laser line onto the surface of an object. The reflection of the laser light is used to form a 2D image where the laser line –– now distorted by the object shape –– crosses the columns of a receiving camera. Each column presents a Gaussian-like shape representing the laser line width, from which a centroid is extracted and transformed into a depth (Z) measurement.
The Gaussian Curve and Intensity Information
In addition to extracting the depth (Z) position, the intensity of the Gaussian curve can also be extracted to build a pre-calibrated 2D greyscale intensity profile. As laser line profiles are collected to form a 3D surface of an object, a complete 2D greyscale (intensity) image is also created simultaneously.
Enabling “Acquire Intensity” in Gocator’s Scan Mode
In Gocator, an 8-bit intensity value is output for each range value along the laser line. Gocator applies the same coordinate system and resampling logic to the intensity values as with ranges.
Intensity image output is enabled by checking the Acquire Intensity checkbox in the Scan Mode panel. When this option is enabled, an intensity value will be produced for each laser profile point.
Select "Acquire Intensity" in Gocator's Scan Mode to Generate a 2D Intensity Image.
2 for 1! Height Map and Intensity Map
When intensity output is selected, two datasets from one analysis are generated –– both a height map and an intensity map. The height map is an image wherein the pixel values represent depth (Z), and the intensity map is an image wherein the corresponding pixel values represent the intensity of reflected laser light. This is similar to how 2D images are formed by a line scan camera and external LED light source.
Having both images allows for more robust 3D measurement and inspection. For example, features in a 2D image (such as an edge or surface pattern location) can be used as references to measure a height related feature. Or similarly, finding a height related feature can give the location for finding and decoding a 2D barcode.
The benefit of a 2D intensity image is that it is calibrated in real world units. Pixels map directly to real-world dimensions so all lens distortions are already removed.