In the fields of personalized customization, rehabilitation medicine, and sports health, accurately acquiring three-dimensional morphological data of the human foot is crucial. Traditional manual measurement methods are not only inefficient and prone to large errors, but also struggle to capture complex surface details. With the development of digital technology, foot shape 3D scanners have emerged as core tools for modern foot assessment. Among them, optical scanning technology has become the mainstream solution due to its advantages of non-contact operation, high precision, and fast imaging. This article provides an in-depth analysis of the commonly used optical scanning technologies in foot shape 3D scanners and their working principles.
- Basic Principles of Optical 3D Scanning
Optical 3D scanning technology is a process that collects spatial point cloud data and reconstructs a 3D model of an object by utilizing the interaction between light signals and the object’s surface. Its core objective is to obtain the X, Y, and Z coordinate information of every point on the object’s surface. In foot scanning, the system must comprehensively sample the complex foot surfaces—including the arch, toes, and heel contour—within a short time to ensure data completeness and fidelity.
The main optical technologies currently applied in foot scanning include: Structured Light Scanning, Laser Triangulation, and Stereo Vision Photogrammetry. Among these, structured light technology, due to its balance of accuracy and speed, is widely used in commercial and medical-grade foot shape scanning devices.
- Detailed Explanation of Structured Light Scanning Technology
Structured light scanning is currently the most prevalent technical approach in foot shape 3D scanners. Its basic components include: a projection unit, an imaging unit (camera), and a computational processing system.
The workflow is as follows:
Pattern Projection
The system projects a series of known encoded light stripes or grid patterns (such as sinusoidal stripes or Gray codes) onto the foot surface using a DLP or LCD projector. These patterns appear regularly on flat surfaces, but when projected onto the complex foot surface, they deform due to surface height variations.
Image Capture
High-resolution cameras simultaneously capture the deformed light patterns from different angles. Since the relative position and angle between the projector and the camera have been pre-calibrated, the system can analyze the degree of pattern distortion through geometric relationships.
Phase Calculation and 3D Reconstruction
Using the “Phase Shifting” method or multi-frame image comparison, the system calculates the phase difference for each pixel, thereby deriving the depth information (Z-axis) of that point in space. Combined with X and Y plane coordinates, dense 3D point cloud data is generated.
Model Stitching and Optimization
A single scan typically covers only a portion of the foot, so multi-view scanning or a rotating platform is required to achieve 360° coverage. The system automatically registers and stitches multiple point cloud datasets, performs denoising, hole-filling, and smoothing, and finally outputs a complete 3D digital model of the foot.
The advantages of this technology include: fast scanning speed (typically completed within 1–3 seconds), accuracy up to 0.1 mm, and non-contact operation, making it suitable for children, elderly individuals, and postoperative patients.
