Non-contact three-dimensional scanning has become increasingly popular lately in the industry, particularly in projects related to Research & Development of new products.
There are two main categories of 3D scanners that have prevailed in the market: laser scanners and structured light scanners. In each category, there are plenty of brands and models that practically cover all kinds of 3D scanning needs. The capabilities, applications, and cost of the 3D scanners vary considerably.
So what are the criteria according to which you should choose the right 3D scanner for your own needs?
In addition to your budget, it's also of crucial importance that you know the application (or applications) for which you want to implement three-dimensional scanning and the actual needs of your application in regards to the required accuracy, speed, safety, lighting conditions and finally whether the object to be scanned is moving or not.
Below, we examine all of the above criteria one by one and we compare the two categories of three-dimensional scanners (laser and structured light) for each of these criteria.
Structured light scanner technology achieves significantly higher accuracy than laser technology. Laser scanners scan the object only once as the laser beam passes over the illuminated object. In particular, they are based on a point that spans into a line, which then scans an entire field. In other words, the scan is executed stretching a one-dimensional line into a two-dimensional region.For this reason, the laser scanner accuracy levels are not so satisfactory. Instead, structured light scanners scan the subject many times, with patterns that change in width and phase. In this way, they evaluate in an excessive way the shape of the object during each scan and because of the repeatability of the readings, they achieve much greater accuracy.
Given that, if your scans are intended for professional use and your application requirements are high, a structured light scanner is a more secure choice.
2. Object Motion Considerations
Laser line triangulation is the optimal solution when the object to be scanned is in motion.
Another factor that you should consider is whether the object to be scanned is in motion or stationary at the point of inspection.If the object to be scanned is on the move, then the laser scanner is the right type of scanner in your case. As the object moves beyond the field of view of the scanner, laser scanners have the ability to collect a series of partial scans from the laser beam. Then, three-dimensional smart sensors with built-in software perform the automated assembly of these scans in a complete three-dimensional digital model of the surface of the object.
Structured light is the best choice when the object is stationary at the inspection point.
However, if the object to be scanned is stationary, structured light scanners excel because they take a sequence of images through different patterns of lights projected onto the surface of the subject.In this way, they create a complete three-dimensional point cloud of the geometry of the subject (whereas in case the object moves during the data acquisition process, errors may occur in the results).
As a conclusion, if you plan to capture an object while on the move (for example, a tool or machine while working), your only choice is a laser scanner.
Time is money especially in our times where technological developments are running at a dizzying pace. Therefore, the speed of scanning is a criterion that cannot be ignored while choosing a three-dimensional scanner. Generally one could sustain that laser scanners have an inherent advantage in terms of speed because they only do one single sweep in contrast to the structured light scanners that do multiple. However, the speed of structured light scanners has improved a lot over the years. With the help of advanced built-in cameras and faster processors, they can now complete a scan with over 1,000,000 points in less than a second!
Therefore, in terms of speed, it cannot be claimed that one type of scanner is superior to the other. Nevertheless, it is important to check the speed in the technical specifications of the model you are interested in buying.
4. Lighting conditions
An additional factor that you have to consider before selecting a 3D scanner is the lighting conditions under which the scanning will take place. Lighting in the working environment may vary significantly and is not subject to control. This may dramatically affect the performance of the three-dimensional scanner's sensors, resulting in incorrect data (and subsequently measurements) or possibly no data at all. In case you plan to scan indoors, you can do so equally well with both a laser scanner and a structured light scanning.
Instead, when it comes to outdoor scans, things are different. In particular, in outdoor lighting conditions, laser scanners excel because they have the advantage of projecting a very specific and narrow wavelength and thus effectively eliminate ambient light. Of course, you should keep in mind that if lighting conditions are difficult (or intense), the results of laser scanning may be relatively noisy and inaccurate. On the other hand, structured light scanners are limited by the light intensity of the bulb and the level of contrast of the projector. Thus, even in office environments or industrial environments (although their use is generally not a problem), the projector and the sensors should be properly adjusted so that the results are optimal.
Safety is an important factor that no one can ignore. In the case of structured light scanners, there is absolutely no reason to worry since they mostly use LED illumination with white or blue light. Consequently, they do not present any safety issues. Laser scanners on the other hand, due to their ability - as mentioned above - to focus light intensity and energy in a very small space, present an inherent safety issue mainly for the eyes, depending on the class in which they are categorized. Higher laser power improves the performance of the scanner in environmental lighting (with shorter exposure time and higher speed scans), however, this increases safety concerns. Indeed, some of the lasers used in 3D scanners today have been found unsuitable for the eyes.
Having said that, in case you intend to use the 3d scanner for human-scanning applications, keep in mind that there are laser systems specifically designed for this purpose (such as body and face scanning) and evaluated for their safety.
The cost of three-dimensional scanners available in the market varies greatly and depends on various criteria, such as their accuracy, incorporation of technological innovations, aesthetics and more. Regardless of the technology implemented (laser or structured light), as the levels of quality, accuracy and reliability of the three-dimensional scanner increase, the cost of the purchase increases as well. However, today, three-dimensional scanning technology has matured enough to make 3D scanners affordable even for professional applications.
In any case, good knowledge of your real needs in combination with the available options in the market will help you make the best value for money choice.
Laser scanners are the right choice when the subject is on the move or when the scan has to be performed in external lighting conditions. Instead, structured light scanners are superior in precision and safety, while the latest models have improved significantly in speed.
No one can claim that one technology is superior to the other. Both technologies have advantages and evolve continuously to eliminate or reduce their weaknesses. The choice of the appropriate type of 3D scanner depends on the needs and requirements of the application for which it is intended.
In Columbo Engineering, we can help you choose the right three-dimensional scanner according to your application and its requirements. Alternatively, if your application does not justify the investment on a 3D Scanner, we can perform the three-dimensional scanning for you and provide you with the required files and reports.