Understanding Laser Scanners - 08/09/2020

When complex or large environments need to be documented, laser scanners are a practical and economical solution. Laser scanning – also known as Lidar technology – can provide continuous in-field verification at every stage of a construction project lifecycle, helping predict and prevent errors and enabling significant cost, scrap and time savings.

Traditionally, capturing large environments relied on tools that produced single point measurements, such as tape measures, piano wire, plumb bobs, laser range finders and total stations. While they are familiar tools, they are often time-consuming, often taking days, weeks or months depending on the space. Additionally, traditional tools often produce inconsistencies in measurements from user to user and ultimately data often gets missed, leading to potentially cascading inaccuracies.

Full scope of measurement data

So, how do they accomplish all of that so quickly? The laser scanner emits a beam of infrared laser light onto a rotating mirror that effectively paints the surrounding environment with light. The scanner head rotates, sweeping the laser across the object or area. Objects in the path of the laser reflect the beam back to the scanner, providing the geometry that is interpreted into 3D data. In addition to the distance measurement, laser scanners also capture measurements on the horizontal and vertical planes, providing a full scope of measurement data. 

Laser scanning is used for a wide range of applications. (Image courtesy: FARO)
Laser scanning is used for a wide range of applications. (Image courtesy: FARO)

A laser scanner typically captures data through two kinds of systems.

Time-of-flight systems: Also known as a pulse measurement system, this works by emitting a single pulse of laser light and determining the distance to the end point by measuring the time it takes for the light to be reflected back to a sensor on the scanner.

Phase-shift systems: Similarly, this system also uses an emitted laser light, but in this system, the intensity of the light is modulated with specific waveforms. The reflection of the intensity patterns is displaced by the impact on the surface of the object. Measuring the displacement between the sent out and the received laser signal provides a precise distance calculation. Generally, laser scanners that use phase-shift systems are accurate, fast and provide high-resolution data.

Broad range of applications

A laser scanner produces accurate results in less time and with fewer errors than other, more traditional methods. And in some cases, such as documenting crime and crash scenes, the time saved offers downstream benefits such as being able to open roadways to the public earlier. In applications that require outdoor work, laser scanners can document complex areas where inclement weather is a concern.

Zooming in on Lidar technology

Laser scanners are non-contact devices that capture millions of discrete data points to measure an object or space using laser infrared technology that produces detailed 3D images in minutes. The images comprise millions of 3D data points, known as a point cloud.

Source: FARO.
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Last updated: 20/10/2020