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Understanding Technology: How Do 3D Scanners Work?

Laser scanning technology allows you to create a digital model of virtually anything.

3D scanning technology is emerging as a crucial aspect of engineering design and simulation, but how can a simple sensor develop an accurate 3D model?

3D scanners can be used to generate CAD models of rooms, parts, components, and even people. For many companies, 3D scanners have become as essential to their business as their engineering software is. Any device with an image or light sensor and some positioning technologies can be used as a 3D scanner.

What do 3D scanners do?

These devices, often phones or tablets, essentially measure the objects in the world around it using lasers or images to generate highly dense point clouds or polygon meshes that can be transformed into a CAD compatible file. Theoretically, it sounds simple – just point your camera or sensor around the room, and the 3D file is generated – however, there is a reason that this technology is only starting to grow within the industry, so let’s get into the technical aspects of what makes it possible.

Processing power is key to what makes modern 3D scanners possible. For most of the modern technology age, we have had the ability, or rather, the knowledge to create 3D scanners. The problem has always been that the amount of processing power needed to generate highly accurate and dense point clouds of the physical world exceeded what was feasible.

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In recent times, we are seeing a greater emergence of this technology because now you hold all of the processing technology right in your pocket. There are currently many mobile apps that can transform your device into a 3D scanner; a quick Google search will yield plenty of resources.

For more complex engineering applications, dedicated machines are typically required to use lasers and precise global positioning. Within these intricacies, there are different types of 3D scanners for different applications: Short Range, Mid Range, and Long Range. 

Short-range laser scanning technology

Short-range laser scanners typically encompass a depth of field less than one meter. Normally, they use laser triangulation systems that involve a source and a sensor. In other words, the source is placed at a known location and the sensor in another known location. The source then shoots a laser at the observed object, and the sensor receives the light at a known point.

Using some simple geometry, a point in a 3D lattice can be generated. Repeat this process, and a complex point cloud can be generated. Another short-range laser system that uses triangulation is known as a structured light scanner. Instead of shooting one laser after another at the object and observing the reflection location, these scanners use a series of linear light patterns to develop a map of the object. By observing how the linear light paths deflect around the object, the software can triangulate a point cloud scan.

Mid and long-range laser scanning

Mid and long-range scanning systems need slightly different laser imaging technology to function. They normally utilize a laser-pulse based system known as time-of-flight scanners. These systems use intensely accurate measurement systems to record the time of flight for a laser to hit an object and return down to the picosecond.

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Through the use of 360˚ rotating mirrors, these systems can quickly and easily develop highly accurate models of the object. Another slight variant to these time of flight systems uses phase-shift technology. Without getting into too much of the nitty-gritty physics, these systems modulate the power and amplitude of the laser wave and monitor phase change to develop more accurate 3D scans.

Understanding Technology: How Do 3D Scanners Work?
Source: Vanessaezekowitz/Wikimedia

Laser scanners will likely always be more accurate than image sensor scanners that are currently available on mobile platforms. However, for many applications, like building surveying and architectural modeling, these image sensors can accomplish the scanning job to the necessary degrees of precision.

3D scanning in construction

3D scanning technologies are also proving useful outside of simple product development. In fact, in many ways, 3D scanning in construction applications has risen to the forefront of usage cases for this new technology. 

Take a look at this video below about one 3D scanner that works for construction applications.

3D measurement in existing buildings can provide highly accurate point clouds for planning and construction. For example, if you needed to design a duct-work system throughout an existing building, a 3D scan of the building would allow you to design that system in CAD with ease. The old alternative would've been sifting through blueprints or going to the site and measuring actual dimensions.

General contractors can also use laser scanning to make sure that the final construction project measures up to the original plans to a high degree of accuracy. By taking a scan of a completed building, the resultant model can be easily cross-referenced with the initial CAD design.

The key metric to note here is that 3D scanning can be done throughout various phases of a construction project. Roughly 15% of every construction project is reworking things that were built wrong. This may surprise anyone, but it's fairly typical considering the vast scope these projects encompass.

3D scanning throughout the entire process allows general contractors to verify construction accuracy during the building phase, preventing roughly 1 to 3% of the reworking process. 

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While that may not sound significant, those numbers are in reference to the overall construction task. So, 1 to 3% of a multi-million dollar construction project is a significant sum of money – it makes laser scanning and the costs associated quickly worth it. 

Integrated with simulation software, 3D scanning can develop simulational models of the actual component, rather than the CAD design. As these scanning technologies continue to grow, we will likely see their deeper integration into engineering operations, possibly helping to play into IoT technologies and real-time dimensional feedback.

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