Handheld 3D scanner light sources: laser lines vs structured light vs infrared

December 19, 2022

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Handheld 3D scanners typically fall into one of three categories: laser, structured light, or infrared. But what are the main differences between these technologies?

Introduction

Handheld 3D scanners are suitable for a wide range of applications. Due to their portability and versatility, these compact devices can be used to scan a diverse array of objects, such as vehicles, outdoor archeological sites, and even people.

Because handheld scanners have so many potential uses, the 3D capture and metrology market is now packed with different options for buyers. Models range from entry-level to professional, and buyers can often find scanners with features tailored to their own field of work. And the handheld aspect doesn’t mean a compromise on quality either: many portable scanners can outperform the static or desktop equivalent.

Importantly though, not all handheld 3D scanners work in the same way. In fact, the light source technology of scanners can be completely different from one model to the next. Some scanners use laser lines to capture 3D data, others use structured light projections, and a small number of products use invisible infrared light to overcome specific scanning challenges.

This article looks at the differences between three major types of active, non-contact scanning technologies for handheld 3D scanners, discussing some of the most significant advantages, disadvantages, and applications of each one.

Handheld laser 3D scanners

Example products: FreeScan UE, FreeScan UE Pro

Laser 3D scanning uses a technique called triangulation. Such scanners shine a laser light (typically red or blue) at the scanned object, making a laser dot on the surface of the object, while a camera or sensor — positioned at a fixed distance from the laser emitter — captures the location of the laser dot. The camera, emitter, and laser dot form a triangle.

The laser dot will appear at a different area of the camera’s field of view depending on how far the surface of the scanned object is from the laser emitter. The scanner can calculate this distance based on the relative position and angle of the laser emitter and camera, and once sufficient scan data has been captured, the entire surface geometry of the scanned object can be determined.

With handheld laser scanners, the scanner must also be able to establish its own location (since it is constantly being moved by the operator). This can be achieved using an internal or external tracking system.

Laser scanners such as Shining 3D’s industrial-grade FreeScan UE Pro are often favored over other technologies due to their usability in a range of environments and on objects with a range of surface textures. This is because laser lines are brighter than structured light projections.

Advantages:

– Laser lines are brighter than structured light, making laser scanners better for scanning in bright environments, including outdoors

– Better than structured light at capturing dark or reflective surfaces

Disadvantages:

– Typically cannot capture color, unless they are hybrid scanners

– More expensive than other technologies

Common applications:

– Reverse engineering

Industrial maintenance and repair

– Quality control

– Scientific research

– Outdoor scanning in fields like architecture, archeology, and natural sciences

Handheld structured light 3D scanners

Example products: EinScan Pro HD, EinScan Pro 2X 2020

Structured light 3D scanning works in a different way to laser scanning. With this scanning technology, the device projects narrow bands of light onto the surface of the scanned object. These bands are typically sets of parallel lines or other patterns.

As with other types of scanning technology, structured light scanning uses one or more cameras located a short distance from the light source. The role of the camera is to capture the projected light patterns as they hit the surface of the scanned object: the camera lens will see the sets of lines as deformed (stretched, widened, bent, closer or further apart, etc.) depending on the shape of the object’s surface. Using a sequence of calculations, the scanner can use the deformed lines of light to work out the location, size, and shape of the scanned object.

The light source for a structured light scanner will usually shine white light or blue LED light, as this kind of light can be controlled to a high level of accuracy. Structured light scanners generally do not have tracking systems, but instead use markers on the scanned object which help the scanning software recognize where the different snapshots overlap.

Structured light handheld 3D scanners are highly versatile, and some models — like Shining 3D’s EinScan Pro HD — are able to offer color scanning, which opens up a number of possibilities. However, structured light scanners are not recommended for use in bright environments, as the camera will struggle to recognize the bands of light if there are other light sources present.

Advantages:

– Capture can be faster than other scanning technologies

– Hardware is less expensive than other technologies

– Picks up minimal noise, increasing scan accuracy

Disadvantages:

– Poor at scanning objects in bright environments

– Poor at capturing shiny or dark surfaces

Common applications:

– Reverse engineering

– Quality control

– Scanning artworks and sculptures

– Forensic analysis

– Capture for VR/gaming

– Scanning colored objects

Handheld infrared 3D scanners

Example products: EinScan H

A less common but still important type of light source for 3D scanners is infrared light. Invisible to the naked eye, infrared light is a kind of electromagnetic radiation with wavelengths that are longer than those of visible light.

Infrared scanners typically work in a similar manner to structured light scanners. However, the projected light is not visible to the naked eye, and a different type of camera must be used to capture the infrared light as it hits the scanned object. Although typically slower and less accurate than visible light scanning, infrared light scanning provides a few important benefits over other technologies.

One of the most common applications of infrared scanning is for human body scanning, which is common in areas like healthcare diagnostics, VR capture, and fashion. Because infrared light is not visible to the naked eye, it can be used to scan faces without causing eye discomfort. Furthermore, it does not cause reflections on shiny surfaces, making it suitable for scanning complex textures like hair.

Infrared 3D scanning is more niche than laser scanning and structured light scanning, with fewer products available on the market.

Advantages:

– Safe and comfortable for scanning human bodies, as no bright light that can harm vision

– No interference from reflections or other light sources

– Good at scanning shiny or dark surfaces

Disadvantages:

– Less accurate than other technologies for general scanning

Applications:

– Human body scanning

– Scanning shiny or dark surfaces such as automotive exteriors

Handheld hybrid 3D scanners

Example products: EinScan H (structured light + infrared), EinScan HX (structured light + laser)

Some of the most powerful handheld 3D scanners on the market combine multiple light sources in one device. This allows the user to easily mitigate the shortcomings of one type of light source.

An example of a hybrid scanner is Shining 3D’s EinScan H, which combines structured light and infrared scanning capabilities. The hybrid scanner is targeted at users who will need to scan both human faces (using the eye-safe infrared scanning mode) and a variety of other objects (which can be captured in better resolution using structured light projection).

Some 3D scanners, such as the EinScan HX, combine structured light and laser scanning. Although the laser scanning capabilities are not as comprehensive as those of an independent laser scanner (such as the FreeScan UE), the hybrid setup enables users to combine the benefits of the two technologies, such as the capture of colored surfaces with the structured light hardware and the capture of shiny surfaces with the laser hardware.

One of the major benefits of hybrid scanners like the FreeScan UE is the ability to combine data from disparate scanning technologies into the same point cloud by quickly switching between scan modes.

Advantages:

– Combines advantages from multiple technologies

– Highly versatile

Disadvantages:

– Learning curve may be steeper

– May cost more than scanners with single light source

Applications:

– Scanning objects with a variety of different features and surfaces

Key considerations

Each of the three scanning light sources discussed here offers its own set of advantages, and each can be capable of capturing professional-quality scans.

With that in mind, it can be difficult to choose between the different technologies when buying a handheld 3D scanner. On the whole, there is a good deal of overlap between the capabilities of laser scanners and structured light scanners. Both use an active light source and cameras to capture scan data, and both are capable of achieving high-resolution scans under the right conditions. On the whole, these technologies have more in common than, for example, coordinate measuring machines and photogrammetry systems.

That being said, there are differences between the types of scanners discussed here. Professionals who plan to use their handheld scanner in a range of indoor and outdoor environments may favor laser scanners, while those who want the ability to obtain detailed scans of small objects in a controlled environment may be better off with a structured light scanner. These models also tend to be less expensive than laser scanners. As we have mentioned, infrared light scanners occupy a smaller territory in the handheld scanning landscape, but certainly have their uses too.

Users planning to deploy their 3D scanner for a wide range of tasks may, of course, favor hybrid scanners, as these tend to offer the widest range of potential applications due to their combination of different technologies.

 

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