What is not meant to be said is meant to be heard. To answer this question rigorously, one must carefully define and consider the degree of "micro" in the microstructure described in the question.
In academia, microstructures tend to be more "microscopic," with devices (e.g., AAOs, grating moments) on the order of micrometers or even nanometers in size qualifying as microstructures. For these micro- and nanostructures in academia, in addition to the optical measurement devices mentioned above, there are a variety of other measurement devices, such as electron microscopes, atomic force microscopes, etc. (see below), however, these devices are expensive and not visible to the public, and there is not much point in introducing them.
At the same time, compared to academia, the size of the structures involved in industry is often on the order of millimeters, so in this paper, we will only summarize and outline the means of 3D morphological microstructure measurements that are visible and tangible to the industry as well as to the daily life.
Quantum corral image obtained by scanning tunneling electron microscopy. Figure dimensions are 25 nm wide and 16 nm high.
Commonly used 3D form microstructure measurements in industryMacroscopically, 3D scanning is a data collection process. Its purpose is to analyze objects or environments that exist in the real physical world and thus collect data on their shape and possibly even their appearance (e.g., color), among other things. A device that can perform this type of 3D form-factor microstructure measurement or 3D scanning is generically referred to as a 3D scanner or 3D scanner.
Most of the 3D scanners active in industry today rely on optical means and principles, and have already demonstrated many advantages in practical applications, such as industrial computed tomography and structured light 3D scanners that utilize optical detection means to achieve injury-free detection and the ability to build digital 3D models. The 3D data collected is used in a variety of other applications in addition to construction.
For example, the data is widely used by the entertainment industry for the production of movies and video games, including virtual reality technology, augmented reality technology, human motion capture, tamper-proof gesture recognition, industrial design, orthopedics and prosthetics for the disabled, reverse engineering and prototyping, industrial quality control, engineering inspections, and digitization of cultural artifacts such as valuable antique paintings and calligraphy.
The following will be described.
Handheld Laser ScannersHandheld laser scanners create 3D images through a triangulation mechanism as shown in the following diagram: a laser dot or line is projected from the handheld device onto the object to be measured, and a sensor (usually a charge-coupled device or a position-sensitive device) measures the distance from the light source to the surface of the object.
Handheld laser scanners collect data related to an internal coordinate system, so in order to collect data while the scanner is in motion, the position of the scanner must be well defined. A common way to determine the position is through the scanner using a reference feature on the surface being scanned (usually a sticky reflective sheet) or through the use of external tracking methods.
Figure The principle of a laser triangulation sensor.
Structured Light 3D ScannerStructured light technology is undoubtedly one of the hottest optical technologies today, and the best example of it being done in industry is the facial recognition technology used in the iPhone series of cell phones produced by Apple.
Structured light is based on the principle that a narrow band of light is projected onto a three-dimensional shaped surface to produce a line of illumination that is distorted compared to the other viewpoints of the projector and can be used to geometrically reconstruct the shape of the surface (the light portion). A faster and more versatile approach in the field of structured light is to use patterned projections consisting of multiple stripes at a time, as this allows multiple samples to be taken in parallel at the same time, as shown in the figure below.
Figure Stripe pattern recording system with 2 cameras
The stripe pattern observed in a structured light system contains several depth cues. The displacement of any individual stripe can be directly converted to 3D coordinates. This is the intuitive understanding that structured light 3D scanners enable 3D structural measurements.
Figure Structured light scanning a car seat
3D Scanning RadarLidar (short for LIght Detection And Ranging), or 3D laser scanner, is a type of measurement device commonly found on civil engineering sites, which can be used to scan civil engineering buildings, surface rock formations (rock formations, etc., and create 3D models of them.
The radar's laser beam can scan a wide area: the head of the instrument, shown here, can be rotated horizontally by 360 degrees, while the mirrors reflecting the laser beam can be rotated vertically and rapidly. The laser beam emitted by the instrument measures the distance from the center of the instrument to the first target hit by the laser light.
ConclusionThe above describes some of the commonly used 3D scanners in daily life and their principles, in addition to the 3D scanner also has many interesting practical applications, as shown in the figure below.
Digital storage and reproduction of ancient artifactsFigure 3D scanning of a fin whale skeleton in the Slovenian Museum of Natural History (August 2013)
Industrial processingFigure 3D modeling of a Viking belt buckle using a handheld VIUscan 3D laser scanner.
Besides, in China, the Ultra Precision Research Institute of Harbin Institute of Technology, Changchun Institute of Optical Machinery, and Shanghai Institute of Optical Machinery are all leaders in the field of 3D measurement, so if you want to follow up on the latest results in this field, you can search for relevant articles from the above institutes, etc.
It is a good thing that we have a lot of researchers who are interested in the field.