What is 3D scanning? A beginner’s guide

3D scanning refers to the process of capturing a physical subject to represent its geometry accurately in a digital environment. The subject can be any object, person, or even the surrounding environment. 

Just like a camera captures a flat, 2D image, a 3D scanner captures an object’s height, width, depth, and some also capture color. 

3D scanning often acquires millions of data points on real-world objects. Manufacturers can use these data points in many ways, including for additive manufacturing, digital twins, reverse engineering, dimensional analysis, 3D inspection and customization for a specific person or application.  

How does 3D scanning work? 

In general, 3D scanning can be accomplished with contact and non-contact methods. Typically, when we discuss 3D scanning non-contact methods are implied. When the measurements are collected, the information is contained within a set of data points (point cloud or mesh representation) in a three-axis world coordinate system.

This data can then be manipulated in a myriad of programs to create desired outputs for Polygonal Models, CAD, CAE, CFD, FEA, and parametric reverse engineering. 

While there are numerous methods of 3D data acquisition, four of the most popular types of 3D scanning include: 

1. Laser scanning

There are two main types of LASER-based 3D scanning.

Laser triangulation captures an object by measuring the deformation of a laser beam projected onto its surface. One or more laser sources project very small points onto the surface and a camera, or cameras, record the positions of those points.

The angle between the laser line points and a camera is pre-determined, allowing for the 3D triangulation to be calculated. On-the-fly calculations record these points in 3D space as the laser line(s) move across the object's surface. This approach produces accurate, high-resolution scans, and is the most capable when objects are reflective and/or dark and shiny. 

Time of flight is a type of laser scanning that measures how long it takes for a laser beam to reflect back to a sensor. Because the laser light's speed remains constant, the reflection time can be used to calculate the object's distance. With enough of these measurements, a very dense point cloud representation of the object can be created. 

2. Structured light scanning

Structured light scanning generally uses one light projector and multiple cameras. It is similar to laser triangulation, but it measures the deformation of a fringe pattern or grid that is projected over the surface.  

Typically, a blue LED or Laser illuminates a DLP chip to create Fringe Patters. As the pattern shifts across the surface, cameras collect data about the variations in the known pattern and triangulate the distances to create a point cloud. 

Structured light creates dense point clouds with great detail on sharp edges, given the resolution of the on-board cameras often utilized. Daylight levels of ambient light can sometimes pose a challenge for structured light depending on the projection technology employed in the system. 

3. Photogrammetry 

Photogrammetry uses standard to highly modified cameras and special algorithms to create a 3D model from multiple 2D photographs. Photos will be captured from multiple angles, and the software recognizes common reference points in the images, often along with gauge bars for scaling, to fuse all the images into a 3D point cloud. 

The pros of photogrammetry are its speed of capture and the ability to retain color data of the captured points. It is ideal for capturing large-scale objects and landscapes.

The con of this approach is that it depends entirely on the resolution and exposure quality of the photographs used to reconstruct the 3D image, and dark areas can often result in missing data in the point cloud. 

4. Computerized tomography (CT) 

CT scans also start out as 2D X-ray pictures taken at various sections of the object. When all of these  2D slices are combined, a 3D pixel or voxel object is formed. The voxel object includes the external geometry and its internal components, and it's often exported as a .stl or other type of 3D mesh for downstream applications. 

CT scans are widely used in industrial settings to create highly accurate measurements on objects where line-of-sight vision systems cannot see or cannot measure at the required level of accuracy. 

There are numerous advantages to CT in any homogenous part, while the downside is that it's often not applicable to large, highly dense, or certain mixed material parts. 

The 3D scanner market offers many types of devices for a wide range of uses.

Types of 3D scanners 

There are many types of 3D scanners, but we will focus on ones using the modalities described above. Things to note are that long-range scanners are often not for use in shorter ranges and vice versa.  

This doesn't mean you cannot scan smaller objects with long-range scanners and larger objects with short-range scanners, but the procedure may be unwieldy and inefficient. Long-range scanners generally have a focal distance over a few meters to hundreds or thousands of meters, whereas short-range would be less than a couple meters in focal range. 

Portable CMM with laser line probe  

Portable CMMs offer physical hard probing often with a non-contact probing system (scanner) attached. The hard probe is either at the end of an articulated arm or is somehow optically tracked by another device with cameras and or a laser. The non-contact probe (scanner) can be attached to the end of an arm or could be tracked by a separate optical tracker system. 

Tracked systems are most often used for larger working volumes, up to several cubic meters, whereas arm-based systems are used for smaller volumes measuring under a cubic meter.

Having a mixture of contact probing for deep and blind features and scanning for all line-of-sight, or organically shaped, areas is often highly versatile.  

Handheld laser scanner 

These are small portable devices that use laser triangulation, often with more than one laser to scan an area very quickly.

You often need to place small round target stickers on the part so the scanner can track where it collects data. This can take some time upfront but can be advantageous in many ways during the scanning process. 

Handheld structured light scanner 

These scanners are similar to handheld laser scanners in size. They are ideal for quick, accurate 3D scans that include texture (color) of medium-sized objects such as a human torso or a wheel. The safety of the light source is helpful for scanning people, and these scanners work with objects that are reflective.  

Fixed structured light scanner 

These devices may be tripod-mounted systems capable of scanning a wide range of objects from very small parts to an entire car. They may also be desktop systems that hold smaller, more complex objects in place for scanning. 

LIDAR  

LIDAR (or laser imaging, detection and ranging) uses laser radar to detect details on small objects, resulting in high-resolution 3D images. Instead of measuring the angle of a deformed laser beam, it measures how long it takes a laser beam to bounce off an object and return. LIDAR also has large-scale applications for mapmaking in surveying, geography and forestry. 

Non-contact data capture is now easier than ever with the broad range of 3D Scanners available

Applications of 3D scanning 

Industries began the shift to digital work relatively recently, but virtually all design and engineering tasks are now done this way. This is why 3D scanning is so vital to so many industries — because it allows physical objects to enter the digital realm with a high degree of accuracy. Examples of 3D scanning are numerous, including: 

Manufacturing 

3D scanning enables engineers to scan existing products to  

• Make iterative improvements 
• Reverse engineer legacy parts that lack CAD models 
• Create a mesh for 3D printing from an existing object without taking the time to create a model from scratch 
• Perform detailed quality control checks on manufactured parts 
• Collect detailed data for finite element analysis (FEA) and computational fluid dynamics (CFD) 
• Recreate accurate CNC cutter paths to remanufacture older parts 

Architecture, engineering, and construction 

AEC firms frequently use 3D scanning to capture the existing (as-built) conditions of a structure prior to a remodel, create project estimates without a site visit, share in-process project updates with stakeholders, perform remote structural inspections, and create a digital twin of a building for facilities management. 

Healthcare 

3D scanning in healthcare allows the creation of products that fit the human body precisely. This could be anything from crowns and bridges in dentistry to custom orthotics and prosthetics that fit better and weigh less, functional cages for custom medical implants, custom-made face masks for people with burn injuries and custom wheelchairs. 

3D body scans also allow healthcare professionals to monitor changes in body measurements over time as well as quickly collect accurate pre-op and post-op patient data.  

Entertainment 

In movies, video games and virtual reality environments, 3D scanning is often used to create hyper-realistic graphics, life-like digital characters, and intricately detailed objects.  

Start exploring 3D scanning 

3D scanning quickly bridges the gap between the physical and digital worlds, creating highly accurate models of real-world objects. It is becoming increasingly critical in manufacturing at various stages in a product’s lifecycle. 

Learn more about Oqton’s 3D scanning solutions or if you have any further questions, please do not hesitate to contact us.