Structured Light 3D Scanning

With the release of the Artec Eva professional scanner, this is a great opportunity to talk about some of the exciting aspects of structured light 3D scanning technology and its benefits.

3D scanning technology

3D models are becoming one of the most versatile and useful types of data in our digital world. They can be used for modeling, visualization, analysis, production, documentation, and many other tasks. A 3D scanner allows you to create a virtual copy of a real object – its “digital twin“.

Typically, the 3D scanning process consists of the following steps:

• The scanner collects data in the form of points, which consist of XYZ coordinates and, if this option is available, color information.
• The scanner software converts the data into a point cloud.
• The program connects points, creating a polygonal mesh.

There are four main data collection methods:

• Photogrammetry. The software combines many photographs of an object taken from different angles and determines the coordinates using triangulation.
• Laser. The scanner emits a laser beam. The beam is reflected from the object and returned to the sensor, which determines the distance to the surface. Laser scanners are powerful tools, but they tend to be quite expensive.
• KIM. Coordinate measuring machines use a probe that contacts the surface of the element to obtain accurate measurements.
• Structured light 3d scanning. The projector emits light patterns (patterns) that deform when reflected from an object. Then one or more cameras recognize the 3D geometry using triangulation algorithms.

Now let’s talk about the advantages of a structured illumination scanner.

Structured Light 3D Scanning and the Importance of Digital Metrology

With the digitalization of manufacturing and metrological processes,structured light 3d scanner is based on structured illumination are becoming more common. The projection strip technology they use is ideal for high-precision scanning at short distances and recognizing small features.

The wide projection area allows such scanners to register more than 2 million measurements per second with an accuracy of several microns, and the high output resolution of the three-dimensional grid allows them to fully reproduce the geometry of the object. The capabilities of structured light 3D scanning largely depend on the following aspects:

• light source (white or blue light; DLP, LCD or laser);
• pattern type (stripes, grids, etc.);
• characteristics and configuration of cameras;
• software.

Different combinations of these factors provide a wide range of possibilities for solving various problems.

So why are structured illumination 3D scanners in such high demand? The answer lies in metrology. Metrological processes associated with quality control and reverse engineering in production have become an important aspect of technical standards. For decades, analog precision instruments such as calipers, micrometers, gauges, magnifying glasses, etc. have been used for these processes. But only experienced specialists can use such tools, working with them is slow, and they can be applied to objects of far from any geometry.

However, any structured light 3D scanning device combines the functions of all these tools and creates complex digital geometry in an instant, without even touching the part. In addition, many industries are robotizing the scanning process within closed production cycles. 

3D scanning of a small part

Areas where 3D scanners of this category are most in demand:

• aerospace industry;
• military-industrial complex;
• automotive industry;
• the medicine;
• entertainment;
• archaeological documentation and research.

Now let’s focus on two main areas of application of metrology: quality control and reverse engineering.

Structured Illumination 3D Scanners in Quality Control

According to ISO 9000, quality control is “the part of the quality assurance package aimed at meeting quality requirements”. The concept itself dates back to the 1920s. Then tightening legislation, increasing requirements for accuracy and competition forced manufacturers to look for ways to optimize their verification processes and ensure repeatability. But today the situation is even more complicated – the development, implementation and maintenance of modern quality control processes require significant time and financial costs. There are even specialized outsourcing centers with modern equipment that deal only with this task.

Luckily for us, measurement technology is evolving at an incredibly fast pace. Important to this process are structured-illumination 3D scanners, which take fast measurements with exceptional accuracy. But perhaps the biggest advantage of these devices is that a company can easily integrate them into digital workflows in-house.

Specialized software products allow you to analyze and compare geometry using color maps. The comparison process includes matching the scanned geometry to the nominal CAD model, and creating numerical and visual representations of local deviations across the entire geometry of the part. With data management and visualization software tools, engineers can make quick and efficient decisions about geometric dimensions and tolerances, and easily communicate the resulting data.

Scanners using this technology are ideal not only for quality control, but also for reverse engineering. In essence, the process of reverse engineering is to get the design features and parameters of the finished product – in other words, we need to get the input data from the output.

What is reverse engineering for? Digitizing obsolete parts, examining existing designs to incorporate the data into their own designs, studying the effectiveness of parts and the causes of their failure – all this brings great benefits to engineers.

Comparison with other technologies

To better understand what part of the 3D scanning tasks can be solved by a scanner based on structured illumination, let’s make some comparisons.

Terrestrial 3D laser scanners are ideal for measuring large objects and landscapes (geodesic works, construction, etc.). Unlike structured illumination systems, laser scanners, especially time-of-flight scanners, can record kilometer distances outdoors even in low light. The former operate over much shorter distances, but are faster and more accurate, more affordable, and more suitable for small to medium-sized sites with complex features.

Photogrammetry can provide exceptionally accurate results both indoors and outdoors regardless of distance. However, its results depend on a number of factors, such as camera resolution, post-processing computing resources, lighting, or surface texture. But more importantly, for the correct application of technology, experienced and highly qualified specialists are needed. If you need fast and efficient real-time data logging and don’t want to spend a lot of time learning the technology, then a structured light 3D scanner is obviously the way to go.

Finally, contact measurements. There is no denying that coordinate measuring machines have had a huge impact on modern quality control technology. These machines are incredibly precise and highly automated. However, contact measurements are not suitable for soft, elastic, or very small items. The operation of the CMM is highly dependent on the installation of the part. There is also always a risk of damage to the probe or scan object. Structured light scanners, in contrast, don’t even touch the part.

CMMs measure objects pointwise, so they work for a long time. Structured light can scan an entire area in a second. As a result, the density of point clouds obtained using CMM is much less. Shiny, smooth, transparent, and dark matte surfaces are generally problematic for non-contact scanners. Perhaps this is where the most serious advantage of contact scanners over non-contact scanners lies. Fortunately, this problem can be solved by sticking position marks or applying a matting spray. However, new generation portable laser devices work with the most difficult surfaces even without marks.