3D scanning is the process of analyzing a real-world object or scene to collect data on its shape and appearance (such as color, texture). The collected data can be used to construct digital 3D models. 3D scanner is an imaging device that collects 3D data. It is based on different imaging technologies including ToF, structured-light and binocular stereo vision.
In the scanning process, lighting is critical for the accuracy of final output. Whether it’s ToF, structured light or active binocular stereo vision, the scanning all starts from light projection. ToF calculates the time span between the light emitted from and reflected back to the camera to get depth information. Structured-light technique is more dependent on the projected light. The structured-light 3D scanner projects light patterns onto the surface of objects, and receives the distorted image to acquire depth information. Active binocular stereo vision also uses the projected light to overcome the stereo matching problem.
In terms of the light source, normally white light, infrared and blue light are adopted. White light is a mixture of all the wavelengths of the visible light spectrum, so it’s safe and has good visibility. Blue light is also visible and features short wavelength and high amounts of energy. It is more interference-resistant than white light, and widely used in 3D scanning. Infrared light has longer wavelength than those of visible light ranging from 700nm to 1mm, and is invisible to human eyes, which has greater anti-interference capability. Revopoint’s handheld 3D scanner Handysense adopts Class 1 invisible infrared light that is safe for the eyes, causing no discomfort especially when scanning human face.
In addition to the projected light, the ambient light affects scanning too. Strong ambient light will interfere with the projected light, thus causing error of the captured data. 3D scanners based on structured-light technology and active binocular stereo vision technology will be more likely to be influenced by strong ambient light, so it is often used indoor without when there isn’t too much strong light.
Light also plays a role when scanning different surfaces, especially those quite sensitive to light. For example, black surface absorbs much of the light; mirror and glass are highly reflective. These surfaces are, to some degree, difficult to scan for most 3D scanners.