How to choose a 3D scanner. Scanning technologies

The 3D scanner market is a very diverse space, with a wide range of products that come in a variety of shapes, sizes, technologies, applications and costs. Each 3D scanner has its own distinctive features, options, advantages and disadvantages in a specific area of ​​application. We will try to help you make the right choice.

3D scanning technologies

Before you decide to buy a 3D scanner, it is important that you have an understanding of what this technology is and how it works. First, a 3D scanner captures (captures) an object or person. Then, it transfers the resulting data to special 3D modeling software, where it can be edited, sent to print, imported into a video game, and so on. After scanning the object, the resulting 3D model can be edited or resized in  CAD applications . After the 3D model is prepared, it can be exported to a file with the .STL extension  . and printed on a 3D printer. This means that everything that we see in our daily life can be scanned and printed, whether it is a small item, such as a piece of jewelry, or a large item, such as a car. There are now many technologies and aspects to consider when purchasing a 3D scanner. Read our article for more information on 3D scanning. 

Photogrammetry

Photogrammetry  predates the computer age: after the invention of cameras, scientists quickly realized that the principle of natural stereo vision can be used in various fields. Using photographs taken from two different positions, they were able to measure and locate the points of objects in three-dimensional space. Experts call this process  "triangulation"... To this day, Photogrammetry is used by surveyors to produce maps with high precision; this has proven especially useful in mountainous areas that are difficult to reach for surveyors or other 3D scanning technologies. Modern computer programs are capable of triangulating entire buildings or small objects the size of a mobile phone. Nowadays, even phones can be turned into portable 3D scanners by simply installing a dedicated app on them. Accuracy is largely due to the quality of the resulting images. The higher the resolution of the photo loaded into the program, the more accurate the data will be. To create a complete model, you need to take many shots, moving around the objects in 15-30 degree increments; repeat this at different heights, especially when 3D scanning complex objects, that is, with many occlusions.

Structured lighting

Such devices  project geometric patterns onto the surface of an object , and cameras at this moment register image distortions. Based on the displacement of the image, the location of each point can be calculated. Since patterns can only be projected from one viewpoint at a time, multiple 3D scans must be combined to form a full 360 ° mesh. Some manufacturers work around this limitation by placing the object on a motorized turntable and automatically gluing the 3D images together. These 3D scanners are very accurate, with a resolution of tens of microns. Unlike 3D laser scanners, this technology is absolutely  safe for people and animals.... The 3D scanning range is limited to a few meters. Structured light technology is used in both stationary and portable 3D scanners.

TOF scan

3D scanners  Time of Flight (TOF) even more technological. They determine the distance to an object by measuring the time it takes for a laser or infrared beam to reflect and return to the 3D scanner. An integral component of this device is the speed of light. The time taken to travel back and forth determines the distance traveled by the light beam. But even powerful TOF scanners have drawbacks, differences in temperature, humidity, and other factors affect the speed of light and hinder the 3D scanner's ability to accurately measure the travel time in both directions. Therefore, their accuracy is relatively low, in the range of centimeters. Most often, such devices are used to scan large objects such as buildings. As with other technologies, it is not possible to create solid meshes in a single scan. TOF scanners, use laser beams, 3D scanned people or animals . 

Triangulation (3D Laser Scanners)

Triangulation  3D scanners, or  3D laser  scanners, are similar to photogrammetry and structured light scanning. They use the same basic geometric principle to locate a point in space. A 3D laser scanner projects a beam onto an object and a camera registers where the laser hits it. Since the angles and measurements of the laser and camera are known, the laser point (or line) can be determined very accurately. These 3D scanners are extremely accurate and have a resolution of tens of microns. On the other hand, their range is limited to just a few meters. Triangulation 3D scanners emitting a laser line are also  capable of scanning moving objects... This technology is not commonly found in portable 3D scanners.

Contact 3D scanners

Contact 3D scanners  physically touch an object that lies on the surface or is attached to some kind of platform that holds it in place. This is usually a slow process as even minor vibrations can distort the scan. Although these 3D scanners produce accurate scans, which are used for example in quality control in mechanical engineering. In this case, the sensors can change or even harm the scanned objects. For this reason, contact 3D scanners are  not used in archeology .

Which 3D scanner technology should you choose?

Choosing the right 3D scanning technology is not easy. There are many criteria to consider before purchasing a device. For example, a single 3D scanner is better suited for architectural purposes, but not suitable for prototyping. You can use an inexpensive office scanner or use an all-in-one portable device. Before examining the 3D scanners on the market, let's take a look at the various aspects that  must be considered . We have compiled a list of the most important characteristics to consider when buying a 3D scanner.

For what purposes is a 3D scanner needed?

The first question you should ask yourself is:  what do you need a 3D scanner for? For example, game developers creating game assets will be interested not only in the high-resolution mesh, but also in the high-quality texture of the object. If so, then  photogrammetry  would be a great solution. Moreover, if you need to print an object from reality on a 3D printer, then he will be interested in accurate measurements of the object. Therefore, a 3D scanner with structured illumination technology is the best choice  You also need to know in advance where the 3D scanning of your objects will take place. If they are relatively small and you can bring them to your office or home, then buy a stationary 3D scanner. If not, you need a portable 3D scanner.

Scanned object type

If you are already thinking of buying a 3D scanner, then most likely you already know what exactly you are going to scan. There is no one-size-fits-all 3D scanner that will be relevant for all areas of use. laser scanner must not be used for 3D scanning of people and animals  , as the laser can damage the eye. Photogrammetry may be suitable for this, but this technique requires the object to be perfectly still. Thus, if you can get great results when scanning your friends or family members, for example, you will have some difficulty when scanning a pet. 3D laser scanners are a great choice if you want to scan large inanimate objects such as buildings or vehicles. If you are interested in reverse engineering , then you need to get a lot of measurement data, so laser or contact 3D scanners are an excellent choice here. However, contact devices, as mentioned above, are not suitable for projects related to archeology and preservation of historical heritage, as this process can damage or even destroy the scanned items. In this case, the best option would be a structured light scanner.

Dimensions and distance to object

Most consumer 3D scanners (structured light) are designed to scan teapot-sized objects at close range. When scanning large objects, you will have to do it in several passes, for example, scanning the object from several sides, and then  "stitching" the model from several parts  into one. The software allows you to do this, but it is quite painstaking work. In general, the larger the scanned object or the further away it is, the more expensive the laser scanner will be. The exception is photogrammetry software, which is usually reasonably priced and produces excellent results.

Object surface requirements

Another factor to consider when buying a 3D scanner is the surface of your object. Both photogrammetry and structured light 3D scanners have serious problems with  reflective and transparent surfaces that cannot be processed and will result in distorted and fragmented meshes. Even the best 3D scanner will not give satisfactory results when scanning poorly fitting surfaces. If you are still interested in these technologies, then this limitation can be overcome by applying a thin layer of opaque varnish to the surface.

Permission

Finally, the most important feature in many applications is  3D scanning accuracy . Contact 3D scanners are extremely accurate, but prices range from $ 30,000 to $ 200,000. Again, you have to ask yourself: what do you want to use the resulting scans for? What kind of permission will be enough to get the job done?

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