3d scanning: Methods, Applications and Advantages

If we want to capture the shape of any object, we use a 3D scanner. The technique of using a 3d scanner to capture the shape of an object is called 3D scanning. We get a 3-dimensional file of the object after the 3d-scanning.

This 3D file can be saved, edited and even print using 3d printers. There are different methods of 3d scanning based on different principles. each of these methods have their own advantages, limitations and cost differences.

Today with new 3d scanning technology,  in addition to the shape, the color data of the object also can be captured simultaneously. Technically, 3D scanned color surface is called a ‘texture’.

3D scans are compatible with CAD (Computer Aided Design) software and also with 3D printing. With the reverse-engineering process, a 3D scan could yield a lot of information about the object design.

3d scanning has great application in industries like automotive, aeronautics, dental, jewelry making, video gaming, special effects and animation movies. The 3D scanners serve as powerful tools for professionals in various fields above.

Different 3d Scanning Technologies

Different types of 3d scanning methods and the principles they are based on, are as follows:

LASER triangulation 3D scanning technology
Structured light 3D scanning technology
Photogrammetry
Contact-based 3D scanning technology
LASER pulse-based 3D scanning technology

LASER triangulation 3D scanning technology

Works by projecting a laser beam on the surface to be scanned and measures the deformation of the laser rays. This method uses single laser point or a laser line to scan around the object to be scanned. The laser beam is first made to fall on the object and as it reflects off from the 3d scanned object, the change in its trajectory is recorded by a sensor. The change in laser trajectory measured with the application of trigonometric triangulation to it helps the scanning system to calculate the specific angle of deviation. The distance from the object to the scanner gives the angular measure directly. With the knowledge of the distance of the scanner from the object, the scanning hardware can map the surface of the object and thereby record a 3D scan.

Advantages of Laser triangulation 3d scanning

Advantage of this technology is its resolution and accuracy while the disadvantage is it is sensitive to the properties of the surface that it scans. There could be a problem in scanning a very shinny or transparent surfaces.

Structured light 3D scanning technology:

This technology makes use of the pattern of light deformation on an object for understanding its 3-dimensional geometry. The scanners use trigonometric triangulation method instead of LASER. It works by projecting a series of light in linear patterns onto an object. The system then examines edges of each line in the pattern and indirectly calculates the distance from the scanner to the object’s surface. The structured light used generally are of colors white or blue. The light is generated with the use of various types of projectors such as the DLP technology (Digital Light Processing). The projected light ray is generally either in a series pattern or it could be a random dot matrix too.

Advantages of Structured light 3D scanning technology

Advantages of this technology are its

  1. Resolution,
  2. Speed and
  3. This can be used to scan people.

The main disadvantage with the structured lighting 3d scanning is its sensibility to lighting conditions and therefore its difficult to work outside.

Photogrammetry 3D scanning technology (Photography)

Also called as 3D scanning from Photographs. This technology captures the photographs of subjects from different angles. And after that with the use of computational geometry algorithms and computer vision, the captured photographs or 2d images of objects are reconstructed into their 3D form. Photogrammetry is the art or technology of taking measurements from photograph images.

It recovers the exact positions of surface points. Combination of powerful computational geometry algorithms and computer vision are used. Basic principle is to analyze photographs of a static subject captured from different viewpoints. Then, the pixels are automatically detected corresponding to a same physical point. Camera parameters such as focal length and lens distortion are the needed data inputs.

The biggest challenge of this technology is to analyze accurately multiple photos and all the points in them. Very powerful computer is thus required to run these photogrammetry algorithms. Other downsides are

  1. the system is sensitive to the resolution of input photographs and
  2. the time taken to run the complex-nature algorithms

Advantages of Photogrammetry 3D scanning

The main advantages of this scanning technology is its precision, acquisition speed and its capability of reconstructing subjects of various scales that are photographed from the ground or air.

Contact-based 3D scanning technology:

There will be a probe attached the device used for contact based scanting. The deformation of probe when in contact with the object to be scanned gives us the data regarding the surface of the object to be scanned. ‘Digitizing’ is another name for contact-based scanning. In this method of scanning,  object to be scanned is either held stationary or moving depending on the type of device. If the device has a movable probe. then the object is held stationary. If the object is moving, then there will be a stationary probe.  The deforming nature of probe while in contact with different spots on the surface is helping the scanning software to visualize the object 3-dimensionally. Coordinated Measuring Machines (CMM) is a specific configuration of these scanners. This scanning is used mainly for quality control after fabrication or during maintenance operations.

Advantages of Contact based 3d scanning technology

Advantages with this scanning are

  1. its precision and
  2. ability to scan reflective or transparent surfaces

The disadvantages are

  1. its speed and
  2. inability to work on organic and free-form shapes.

LASER pulse-based 3D scanning technology (also known as Time-of-Flight scanners or Lidar)

As the name suggests, this technology is based on the time of flight of a laser beam. The subject is illuminated with a laser first. A sensor, is there to collect the reflected laser beam from the surface of the object to be scanned. The time taken by the laser to travel from the emission point to the reception point at the sensor can give the geometrical information of the object. These scanners hence measure the time interval between emitted laser to hit an object, get reflected and come back. Since the speed of light is known, the time interval can give the exact distance between the the object and the 3D scanner. For more precise measurements, the distances can be measured with millions of laser pulses of pico-second scale (0.000000001 seconds) accuracy.

The laser has to be emitted 360 degrees around a particular point since each measure collects only data of one point. The direction or path of the laser is changed with the help of a mirror or reflective surface that is fixed into the 3D scanner.

Laser pulse and phase shift lasers (which are subcategory of the laser pule scanners) are both incorporated into the Lidar scanners. Along with pulsing the laser, the phase shift lasers is also capable of modulating the power of the laser beam. Therefore, they offer a better performance.

Advantages of LASER pulse-based 3D scanning technology

The great advantage of this type of scanning is that it can scan large objects and large environments. The process is but slow. 

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