Spectral transmission measurement is a non-contact thickness measurement technology based on optical principles. By analyzing the propagation characteristics of light within transparent or translucent objects—such as refraction, absorption, and interference—and combining spectral analysis with geometric calculations, it achieves high-precision thickness detection.

I. Core Principle of the Spectral Opposite-Direction Detection Scheme

1. Optical Path Design: Opposite-facing structure: The emitter (light source) and receiver (spectral sensor) are positioned on opposite sides of the product, with light passing through the product and being captured by the receiver.

2. Absorption Spectrum: A material's absorption rate for specific wavelengths of light correlates with its thickness (e.g., glass absorbs infrared light more intensely as its thickness increases).

II. Technical Steps

1. System Hardware Configuration

• Spectral Receiving Module: Spectrometer or high-resolution CCD/CMOS sensor paired with diffraction grating or prism for spectral separation; focuses transmitted light onto the sensor's sensitive surface.
• Mechanical structure employs a face-to-face bracket to secure the light source and receiving end, ensuring optical axis alignment.

2. Key Algorithm Workflow

• Spectral Acquisition: The emitter transmits multi-wavelength light while the receiver synchronously collects transmitted spectral data.
• Thickness Calculation: Combines calibration data (spectral characteristics of samples with known thickness) with least-squares fitting or machine learning models to estimate actual thickness values.

3. Error Compensation and Optimization

• Ambient Light Interference: Employ dark current correction and background spectrum subtraction techniques.
• Material Refractive Index Variations: Implement real-time temperature compensation or utilize a pre-set multi-material refractive index database.
• Surface Roughness Impact: Reduce scattering noise through multi-angle averaging or polarization filtering.

Application Scenarios

• Glass Product Thickness Inspection

• Film Material Measurement

• Semiconductor Industry