What is a 3D scanner

Since 3D scanners have become more affordable, 3D scanning has changed the world of custom 3D printing. Once, 3D scanning was only used in military equipment and spacecraft parts production. With desktop and handheld 3D printers available for a few hundred dollars, 3D scanning has found a place in home fun and hobby projects. You can take your 3D printing projects to the next level with a budget 3D scanner. After all, custom 3D printing is a new hot phenomenon. Even minimal 3D scanning is available in smartphones like iPhone 12 Pro and iPhone 13 Pro. This article will discuss 3D scanning, what it is all about, and how to get started with 3D scanning.

What are 3D scanners?
3D scanning converts physical objects into digital 3D models by capturing the object’s shape and geometries. It is a non-destructive, non-contact technology that creates points cloud of data from the surface of an object with the help of laser scanning or other scanning methods. It helps acquire a real object’s exact shape and size as a digital 3D representation. 3D scanning also helps capture details of complex geometries and irregular contours, which are impractical to measure, model, or estimate with traditional methods.

3D scanners for back engineering
3D scanning is not something new. It has been used in the military, aeronautics, and aerospace industries for reverse or back engineering. Reverse engineering is a process of recreating a product or part without its documentation, drawing, or 3D model. 3D scanners have been used to create digital CAD models for parts that need to be reverse-engineered or re-engineered. 3D scanning has been useful in regenerating, optimizing, and modifying parts. Reverse engineering involves three steps. First is acquiring a 3D representation of an object with the help of a 3D scanner. Second, the captured 3D data is converted to a solid 3D model using specialized software. Finally, the model is processed to eliminate artifacts and refined to make it production-ready. Later, it is converted to a suitable format, which can be 3D printed.

As 3D printing has become increasingly popular, 3D scanning has been reinvented to make it more affordable for custom 3D printing. With 3D scanners worth a few hundred dollars, 3D scanning has reached ordinary users, who can utilize the technology to tweak and enhance their regular 3D printing projects. For intermediate to advanced 3D printing users, a 3D scanner is a must-have equipment.

How do 3D scanners work?
First of all, 3D scanners collect data with the help of laser scanning. The object to be 3D scanned is placed on a bed that serves as a spatial reference for the digitizer. With the use of specialized software, the probe of the scanner is moved around the object, capturing the details of the object’s surface. The probe projects a laser beam onto the object’s surface, which is recaptured by two camera sensors. The camera sensors keep track of changing distance and shape of the reflected laser beam along three dimensions as the probe moves around the object.

The result of a 3D scan is a collection of millions of points called a point cloud. The point cloud is a raw 3D representation of the object’s shape. A 3D scanner usually captures up to 750,000 points every second with a high precision of around +/-0.0005 percent.

The point cloud is stored as a computer file. The file is then merged and processed with the help of specialized software to create a digital CAD model. Sometimes, the created CAD model may be compared with a user-designed 3D model to deliver a color map deviation report. The report is a PDF detailing the differences between the scanned and expected CAD models.

Finally, the scanned model is processed and refined to generate a surface model or a solid 3D model per the application. The post-scan processing of the scanned model is usually the subject of the specific use case. There are many different types of 3D scanners based on their technology. Irrespective of the scanning technology, the working of 3D scanners is all the same.

Applications of 3D scanning
3D scanners are no more restricted to spacecraft or military production. 3D scanning is now a technology widely used in several verticals, including home fun and hobby projects. Some of the notable applications of 3D scanners are following.

Hobbyist 3D printing: Handheld and desktop 3D scanners are useful in recreating household items, repairs, miniatures, toys, and other hobby projects.

Dental: 3D scanning is used for custom crown design and bespoke implants to meet our specific requirements of dental patients.

Medical: 3D scanning is used in several medical applications, including orthopedics, plastic surgery, and prosthetics. The scanning is also in use for designing mobility aids and wheelchair accessories. It is also now used to create realistic dummies for medical practice.

Jewelry: 3D scanning is often used for replication, duplication, and repairing antique jewelry. It is also used to digitally store discontinued jewelry designs or modify and improve current designs.

Architecture: 3D scanning is widely used for scanning buildings for repair, surveying, and modeling.

Archeology: 3D scanning is used to digitally conserve heritage objects, artifacts, skeletal remains, and even archeological sites.

Forensics: In forensics, 3D scanning is used to replicate crime scenes and evidence like shoe prints, crime weapons, bullet holes, blood stains, etc.

Reverse engineering: 3D scanning has been widely used for reverse engineering and re-engineering in the fields like automotive, aerospace, and military technology.

3D scanning technologies
3D scanners are often classified based on the scanning technology or method. The broad classes of 3D scanners are following.

Laser triangulation: This is the most widely used 3D scanning technology. In these scanners, a laser beam is projected from a probe to the object’s surface and reflected by a laser sensor that captures laser lines. Based on the reflection angle of the laser sensor, the scanner captures accurate and precise details of the surface and texture of the object using various trigonometric functions. However, the laser triangulation method is useless if the object is transparent or has shiny surfaces.

Structured light scanning: This is the most effective method of 3D scanning and is used by handheld 3D scanners. In this method, a light pattern is projected towards the object, and a pair of camera sensors capture the reflected light. The camera sensors are placed on either side of the projector. These camera sensors measure light patterns from each side and calculate differences at every point in a given field of view. The sensors evaluate how the object deformed the light pattern by triangulating several reference points across different object scans. By repetitive triangulation and comparison, the exact shape and dimensions of the object are derived with the help of specialized software. This method of 3D scanning is most effective and portable. However, the scanning can be affected by the lighting conditions. Therefore, it is often used for specific 3D scanning applications like medical, dental, and archeology.

LiDAR 3D scanning: This type of 3D scanning is used by smartphones like iPhone. In this method, light beams are projected towards the object, then the shape and dimensions of the object are calculated based on the time light takes to reflect. The functioning of LiDAR scanners is identical to time-of-flight scanners that are used to map terrain, buildings, and architectural structures.

Laser pulse scanning: This is also called time-of-flight scanning. In this type of 3D scanning, laser pulses are shot at an object and recollected by a sensor. Based on the time interval between emission and collection of pulses, the geometrical details of the surface of the object are calculated.

Photogrammetric scanning: In this type of 3D scanning, a 3D model of an object is constructed with the help of a collection of 2D photographs of the object. The method uses computer vision and geometric algorithms to create a 3D representation of the surface or object.

Contact-based 3D scanning: In this method, the points on the surface of an object are captured using a mechanical or physical probe.

Types of 3D scanners
Besides the 3D scanning technology, 3D scanners come in various sizes and models. A 3D scanner for scanning jewelry would not be useful for scanning large objects. Similarly, a desktop 3D scanner would not be used for architectural surveys. The 3D scanners are usually identified by their application. The major type of 3D scanners are as follow.

Desktop 3D scanners
Handheld 3D scanners
Jewelry 3D scanners
Terrestrial LiDAR scanners
Metrological 3D scanners
Simultaneous Localization and Mapping (SLAM) scanners
Dental desktop 3D scanners
3D body scanners

How to buy a 3D scanner
Many key considerations must be taken before opting for a particular 3D scanner. First, you need to shortlist 3D scanners based on your use case. Each type of 3D scanner is usually suitable only for a specific application. For example, for custom 3D printing, a desktop or handheld 3D scanner would be required. Contrary to this, a SLAM or iMMS scanner would be required for architectural scanning. A particular use case might narrow down the available options of 3D scanners as many applications can be fulfilled only by industrial 3D scanners.

You may also need to consider the size of the objects to be scanned. For small objects, stationary 3D scanners are best as they provide higher resolution and accuracy. Handheld scanners are suitable for large objects that need to be scanned in outdoor conditions. The handheld scanners may not have the resolution, speed, and accuracy that the stationary scanners offer.

Before taking into account the key features of available models, the next consideration is the budget. The professional 3D scanners are available from a few hundred dollars to tens of thousands. The price ranges from $400 to $200,000 for 3D scanning equipment. For most common uses, we can divide 3D scanners into three price segments—budget 3D scanners (price up to $1000), professional 3D scanners (price between $1000 and $10,000), and industrial 3D scanners (price above $10,000).

The following important factor in buying 3D scanners is their speed. It depends if the scanner is purchased for professional, industrial or personal use. Ideally, a 3D scanner should be fast, with a scanning speed of million points per second and at least 20 FPS. For personal or hobby use, speed can be compromised.

Another critical factor is resolution and accuracy. The accuracy of a 3D scanner is often specified in mm. Budget 3D scanners provide an accuracy of 0.1~0.2mm. Industrial 3D scanners are capable of delivering accuracy up to 0.009 mm. The higher will be the accuracy; the more detailed 3D models can be constructed.

Finally, one should also consider the software support of a 3D scanner. The software capabilities of a 3D scanner can range from barebones 3D scanning to high-level post-processing of 3D models. One more factor critical in choosing a 3D scanner is its connectivity. Most of the desktop 3D scanners use a USB interface to connect to a computer. The professional desktop scanners may also provide connectivity through Bluetooth and WiFi. The handheld 3D scanners are often designed to pair with power banks and smartphones.

Top 3D scanners
Desktop and handheld 3D scanners are available in all price segments. Some of the budget 3D scanners in 2022 include Revopoint POP, Creality CR-Scan 01, Phiz 3D scanner, Matter and Form 3D scanner V2, Structure Sensor Pro, BQ Ciclop, Shining 3D EinScan SE, Artec EVA, Scan Dimension SOL, Shining 3D EinScan SP, iPhone 12/13 Pro, Scantech KSCAN, Shining 3D EinScan Pro 2X Plus, Zeiss T-Scan Hawk, Creaform Goscan Spark, Evatronix EviXscan 3D Quadro+, Zeiss GOM Scan 1, Artec Space Spider, Artec Leo 2022, Faro Freestyle 2, Creaform Academia 20, Polyga Compact S1, Creaform Handyscan 307 Silver, Peel 3D 1, Peel 3D 2, Peel 3D 2S, Artec Eva and Evatronix EviXscan Optima+ M. Some of the professional 3D scanners in 2022 include Shining 3D EinScan H, Shining 3D EinScan HX, Scantech iReal 2E, Scantech SIMSCAN, Creaform Handyscan Black Elite, GOM Scan 1 and GOM ATOS Q.