3D Scanners Information
3D Scanners use optical, laser, or other methods to capture 3-dimensional information about objects. The resulting data can be used to reverse engineer an object, measure it, convert it to a digital image, and other applications. 3D scanning is a fast and accurate method of creating 3D scan data, which consists of putting physical measurements onto a computer in an organized manner. The 3D scan data is represented with a scale digital model or a 3D graphical rendering. All of the physical dimensions from the object can be taken once the scan data is on the computer. The information can then be converted to a computer-aided design (CAD) model or a computer-aided engineering (CAE) tool.
Types of 3D scanners
A 3D scanner captures 3D information. There are many types of 3D scanners in order to accommodate the many methods for capturing the information. 3D scanning techniques can be classified as either non-contact methods or contact methods. The methods are typically used independently but can be used in combination to create a more versatile system.
Non-Contact 3D Scanning
Non-contact scanning captures millions of points on the xyz coordinate system very quickly. This information gives the full size and shape of an object faster, and more accurately than a physical part could be measured. This method can detect the entire part, including warpage, reducing the chance of human error. Non-contact scanning can further be classified as active or passive scanners.
Active Scanners- Active scanners emit some kind of radiation or light. The scanner detects the reflection in order to gather information about the object.
Laser Triangulation- This technique uses a laser to project a point or line onto an object and then captures its reflection with a sensor located at a known distance from the laser's source. The reflection angle can be interpreted to give the 3D measurements of the part.
Time of flight- This technique emits a pulse of laser light that is reflected off the object being scanned. A sensor detects the reflection and the speed of the laser light. The time elapsed between the emission and the detection gives the distance to the object. Time of flight scanners can operate over long distances and are suitable for scanning large structures like buildings or geographic features. The disadvantage of this method is the possibility of noise interfering with the light and affecting the accuracy.
Phase shift- This process captures the phase shift in the reflected laser and a standard phase and compares them. Phase shift is similar to time of flight detection, except that the phase of the reflected laser light further refines the distance detection.
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Passive scanners are often inexpensive because they do not emit radiation themselves. They rely on detecting reflected ambient radiation. This can often be done with a digital camera.
Stereoscopic- This system uses two cameras looking at the same object. An analysis is done on the differences between the two images to determine the distance at each point in the images.
Photometric- This system uses a single camera taking many images at varying light conditions. The image formation model is inverted to recover the surface orientation on a pixel level.
Silhouette- This system outlines the object by taking a sequence of images against a well contrasted background.
Contact 3D Scanning
A carriage system with rigid arms in a perpendicular relationship.
An articulated arm with rigid arms and angular sensors.
A combination of the two can be used for mapping large objects with interior cavities or overlapping surfaces.
In general, scanning is better for organic shapes and digitizing is better for geometric shapes. Laser scanning can also be used for larger items (cars, building, and landscape) and for objects that cannot or should not be touched (important/delicate artifacts). Digitizing is frequently used for first article inspection for objects that require precise measurement. However, the two methods can be interchanged when appropriate.
3D Scanner (Wikipedia)
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