What is laser 3D scanning?

To simplify it, laser scanning is a process of capturing precise, three-dimensional information from a real-world object, a group of objects, or an environment, using a laser as a light source. By projecting laser light onto the object, the scanner creates point clouds – millions of precisely measured XYZ points that define the object’s position in space. Some laser scanners allow the option of downloading the model as point clouds, while others automatically convert it into a triangulated mesh, which can then be transformed into a CAD model or a full-colored 3D model if the recording of texture is supported.

A long-range laser scanner being prepared for use on an offshore vessel (Photo courtesy of ASOM)

Unlike the contact-based measuring systems that we reviewed earlier, laser 3D scanners are 100% non-contact and non-destructive active devices that can capture objects made of solid and fragile materials. They can work indoors while some can operate outdoors as well. They can be used in daylight or at night, and can be both stationary and portable. They can be used to scan at a wide range of scales and for a broad range of objects and sites – from very small to very large.

Depending on the application, 3D laser scanners can come as standalone devices – portable, handheld, or stationary and tripod-mounted, for example – or as part of a more complex solution such as robotic arms, mobile or airborne laser scanning systems, and more. On the technological side, there are time of flight, phase shift, and triangulation-based laser scanners.

Let’s take a closer look at the most popular types of laser scanners and how they work.

The first type of laser scanners typically used for long-range data acquisition is Time of Flight (TOF). Such 3D scanners work by the same principle as laser range finders work: a laser pulse is sent out onto an object, while a portion of the pulse is reflected from the object’s surface and returns to the scanner. The distance to the object is calculated by the time of the flight of the pulse, using this formula: Distance = (Speed of Light x Time of Flight) / 2). This distance is then used to calculate a coordinate for the tiny section of the surface hit by the laser beam.

How Time of Flight measurement principle works

Time of flight 3D scanners can capture objects over great distances of up to 1,000 meters away. However, their typical working range is 5-300 meters. While TOF systems can measure over long distances, they have the slowest data caption rates – between hundreds and thousands of points per second.

The accuracy of TOF technology is determined by the system’s ability to accurately measure the time of the returning signal. While accuracy specifications vary across different systems, the typical accuracy for a TOF scanner is 4-10 mm. More recent TOF systems also include an additional RGB caption option, either through an internal camera or an external camera set.

The third type of laser-based scanners operates on the principle of triangulation, where laser light is emitted and returned to a specific location on an image sensor array of an inboard camera. To calculate the distance between the object and the 3D scanner, the system uses trigonometric triangulation because the laser source, the sensor, and the target left on the object form a triangle. The distance between the laser source and the sensor is known very precisely, as is the angle between the laser and the sensor. As the laser light bounces off the scanned object, the system can measure the angle at which it is returning to the sensor, and therefore the distance from the laser source to the object’s surface.

How triangulation measurement principle works

Triangulation-based laser scanners work at much shorter ranges (less than 5 meters) than the time of flight or phase shift scanners due to the small dynamic range of the image sensors and decreased accuracy with range. Most triangulation systems also come with an internal RGB capture option.

Commonly, triangulation-based scanners are most suited for scanning smaller objects ranging in size from 1 cm up to 2-3 meters, depending on the manufacturer. As for the form factor, there are stationary, tripod-mounted triangulation scanners. However, this technology meets the most success when used in portable handheld 3D scanners.

Scanning the undercarriage of a car with short-range laser triangulation 3D scanner

From small mechanical components to massive industrial objects, laser scanners have become an essential technology in the toolkits of professionals involved in product design and development. Once a complicated process that could require days of disassembly, detailed manual measurements, and the painstaking process of examining each part of a product, thanks to laser scanning reverse engineering now takes anywhere from a few minutes for a CAD surface model, to a few hours for a parametric CAD model. The scanners are used to create accurate digital blueprints of parts that have been damaged or deformed, need a redesign but don’t have CAD data available for them. Portable laser scanners with embedded processors are perfect for examining small and medium-sized objects, while medium and long-range devices work best for larger items. Instant creation of CAD models frees up hours if not days of work, which R&D teams can spend on the actual product enhancement.

Capturing a crime scene with laser triangulation 3D scanner

Thanks to their capability of capturing large spaces such as room interiors, buildings, and entire sites, laser scanners are becoming the new go-to solution for the accurate documentation and investigation of crime scenes, and reconstruction of accidents. Unlike traditional evidence collection methods such as photo and video cameras, and measuring tapes, laser scanners allow investigators to capture entire crime scenes in their original state, with precise dimensions for every piece of evidence, be it a body, a footprint, or a bullet hole, and do it all in a matter of minutes.

Portable handheld laser scanners with embedded processors are perfect for capturing standalone items on the go at multiple locations within a day, and can be brought in when higher and more accurate data is needed, e.g. a closer scan of a dead body, a damaged piece of furniture, or close up scan of a footprint left by the criminal. Long-range scanners, on the other hand, are useful for capturing an entire space. By having it placed in the middle of the room where it scans fully automatically, the investigator can engage in other parts of their work, such as talking to witnesses and victims, without a need to control the scanner. The 3D data enables forensic experts to have a fuller and much more detailed picture of a crime scene and build stronger and more decisive cases to present in the courtroom.

Capturing the skull of a triceratops with a handheld short-range laser scanner (Image by David Cano / 3D Printing Colorado)

Archeology is another area where laser scanners have become indispensable tools for 3D documentation of archaeological excavations, be it a single bone of an extinct animal or an entire ancient city. Portable handheld laser scanners with embedded processors come in handy in fieldwork, and allow archeologists complete autonomy in capturing their discoveries. Thanks to the built-in screen, they can see the results of what they scan in real-time, without carrying an additional laptop or tablet at the same time. Long-range terrestrial and airborne laser scanning systems are successfully applied to map topography, excavations planning, and spot archaeological sites that researchers would never be able to see with the naked eye, thus leaving them hidden.

Laser scanners allow archeologists to collect reliable and high-resolution data much quicker than they’d be able to with other methods such as total stations, GPS devices, or photogrammetry, saving them hundreds of hours of labor during an excavation. Thanks to their non-destructive, contactless nature, they can be used to capture fragile and vulnerable historical pieces in their original state. The data collected can be used for archaeological documentation and for creating virtual-reality models, restoration, preservation, and demonstration of archeological discoveries for the public.

Artec Ray can capture large objects with submillimeter accuracy from up to 110 meters away

Artec Ray is a phase-shift long-range laser scanner designed to capture large and very large objects, such as buildings, airplanes, wind turbines, and the like, with submillimeter accuracy. The scanner has an operating range of 110 meters and can capture up to 208,000 points per second by rotating 360 degrees around itself and vertically with a 270-degrees viewing angle. Unlike many long-range scanners, Ray acquires highly accurate and clean data, which makes it usable for reverse engineering and quality inspection purposes. It comes with a tripod and can work autonomously both indoors and outdoors, thanks to a built-in battery, onboard Wi-Fi, and a mobile app that enables remote control of the scanner. The data captured with Artec Ray can complement more dense and feature-rich scan data acquired with Artec’s handheld scanners.