Analysis of the working principle and measurement accuracy of the plantar scanner

I. Optical Architecture of the Laser Transmission System

Line Laser Array Topology

Using a 650nm red laser diode (Class 2 safety rating), it projects 21 parallel light strips at a 30° fan angle.

Moiré fringe technology compensates for differences in skin transmittance (diabetic foot transmittance is reduced by 12-15%).

Dynamic power adjustment system (adjustable from 0.5mW to 5mW) adapts to varying skin tones and reflectivity.

Optical distortion correction

Built-in fisheye lens distortion parameter library (including compensation solutions for six common arch shapes).

Real-time calibration using a checkerboard calibration method (error <0.03mm/m²).

2D and 3D point cloud reconstruction algorithms

Phase measurement profilometry

Depth information is calculated using laser fringe phase shift (acquired by a single sampling). 2000+ feature points)

Adaptive sampling technology: Point density reaches 8 points/cm² in the arch area and 5 points/cm² in the heel area

Noise filtering mechanism

Motion artifact elimination: Based on IMU sensor data compensation (reducing scanning error by 62% in walking mode)

Hair interference processing: Frequency domain analysis is used to filter out high-frequency noise (effective for patients with excessive hair growth on the dorsum of the feet)

III. Accuracy Verification System

Laboratory benchmark testing: Verified using a NIST-certified standard sphere (50mm diameter ±0.001mm)

Static repeatability error: Arch height measurement standard deviation ≤ 0.12mm (ISO 13485 Standard)

Clinical Consistency Assessment

Compared with traditional plaster casting: Metatarsal joint angle deviation <1.2° (sample size n=300)

Inter-operator reliability: ICC value ≥0.91 (95% confidence interval)

IV. Environmental Adaptability Design

Light Interference Countermeasures

Active Ambient Light Suppression: 50Hz power frequency flicker detection + band-stop filtering

Multispectral Fusion: Combined with a 940nm infrared laser to assist in dark skin measurement

Temperature Compensation System

Laser Temperature Drift Coefficient: ≤0.008%/°C (10-40°C operating range)

Automatic Thermal Expansion Correction: CTE Matching Calibration of the Aluminum Heat Sink