3D scanning is a powerful technique to create realistic and detailed 3D models from real objects. However, 3D scanning accuracy can vary depending on several factors that affect the quality and precision of the captured data. In this article, you will learn about the most common factors that affect 3D scanning accuracy and how to avoid or minimize them.
Different types of 3D scanners use different methods to capture the shape, color, and texture of an object. Some of the most common types are laser, structured light, photogrammetry, and contact scanners. Each type has its own advantages and disadvantages, and some are more suitable for certain applications than others. For example, laser scanners are fast and accurate, but they can be affected by ambient light and reflective surfaces. Structured light scanners are more versatile and can scan complex shapes, but they require a controlled environment and calibration. Photogrammetry scanners are cheap and easy to use, but they rely on the quality and quantity of the photos taken. Contact scanners are precise and reliable, but they are slow and can damage delicate objects.
Optics based 3D imaging techniques have been evolved from macro to micro scale resolutions. Stereo vision, time of flight, triangulation based laser scanners, digital fringe projection, interferometry, photogrammetry, etc. are few popular technologies. Greater resolution and high accuracy can be achieved from interferometry, but has drawbacks wrt working condition and object topography. DFP and laser scanning systems are alternatives to achieve high accuracy. DFP systems render good depth and lateral resolution with dense 3D data. Laser scanners are preferable where surface reflectivity and speed of measurements is concern. Evolution of optics and chips has enabled DFP and laser scanner achieve accuracy and resolution close to nano scale.
The most common factors that affect 3D scanning accuracy are resolution, calibration, lighting, surface texture, scanning speed, environmental conditions, geometric complexity, noise, scanner type, post-processing, user expertise, reference markers, and data registration.
In my experience, the most common factors affecting 3D scanning accuracy include the quality of the scanner, environmental lighting conditions, the material and surface properties of the object being scanned (reflective, transparent, or dark surfaces can pose challenges), the size and complexity of the object, and the distance between the scanner and the object. Additionally, operator skills and the scanning software's capabilities are crucial in achieving high accuracy.
The settings of the 3D scanner can also affect the accuracy of the scan. Some of the most important settings are resolution, speed, distance, and angle. Resolution determines how much detail the scanner can capture, but it also affects the file size and processing time. Speed affects how fast the scanner can move and scan the object, but it can also affect the stability and smoothness of the scan. Distance affects how close or far the scanner is from the object, but it can also affect the focus and distortion of the scan. Angle affects how the scanner views the object, but it can also affect the visibility and occlusion of the scan.
The characteristics of the object being scanned can also affect the accuracy of the scan. Some of the most common characteristics are size, shape, color, texture, and material. Size affects how much of the object the scanner can capture in one scan, and how many scans are needed to cover the whole object. Shape affects how complex and curved the object is, and how many features and details it has. Color affects how well the scanner can detect the contrast and boundaries of the object, and how much light it reflects or absorbs. Texture affects how smooth or rough the object is, and how much variation and noise it has. Material affects how rigid or flexible the object is, and how much it deforms or changes during the scan.
Agreed, I would also harp on reflectivity and translucence as being particularly variable material characteristics. I’ve noticed vector anomalies when laser scanning parts such as lenses, aircraft transparencies, and highly polished tooling.
The environmental conditions where the scan takes place can also affect the accuracy of the scan. Some of the most common conditions are lighting, temperature, humidity, and vibration. Lighting affects how much and how evenly the object is illuminated, and how much glare and shadow it creates. Temperature affects how much the object and the scanner expand or contract, and how much thermal noise they generate. Humidity affects how much moisture is in the air, and how much it affects the optical and electrical components of the scanner. Vibration affects how much the object and the scanner move or shake during the scan, and how much blur and error they introduce.
The post-processing steps that are applied to the scan data can also affect the accuracy of the scan. Some of the most common steps are alignment, registration, cleaning, smoothing, and meshing. Alignment involves adjusting the orientation and position of the scan data to match a reference coordinate system. Registration involves combining multiple scan data sets to form a complete and coherent model. Cleaning involves removing unwanted or erroneous data, such as noise, outliers, and artifacts. Smoothing involves reducing the roughness and irregularity of the data, such as spikes, holes, and gaps. Meshing involves converting the data into a polygonal mesh that can be used for rendering and editing.
While each of these things are important (i.e., 3D scanner device, scanning conditions, object characteristics, postprocessing scans), the most important part of accurately 3D scanning objects is your method. Have reasonable expectations, and approach your project with those expectations in mind. First, decipher the scope of your project and use a device that is known to provide the results you will need. Consider the characteristics of your object -- the size, the texture, the background -- and make adjustments to optimize the results of your scan. If it's shiny, make it matte. If it's angular, pass over your object several times from different perspectives. Always clean up your mesh when postprocessing, and expect that it will be messy.