The core technology of online spectrometers covers the entire chain of dispersion elements, focusing imaging systems, detectors, and signal processing systems. Each link works together to achieve high-precision spectral analysis. The specific breakdown is as follows:
1. Dispersion element: the cornerstone of spectral separation
Dispersion element is the core component of spectrometer, which decomposes composite light into monochromatic light through the principle of light dispersion. Common types include:
Grating: Using the principle of diffraction, different wavelengths of light are deflected at different angles through periodic structures to achieve wavelength separation. Its advantages lie in high resolution, uniform dispersion, and suitability for the ultraviolet to near-infrared bands. But it needs to be combined with a filter to eliminate the interference of stray light in multi-level spectra.
Prism: Dispersion is based on the difference in refractive index of light of different wavelengths, with stronger dispersion ability for short wavelength light. It has a simple structure and low cost, but it suffers from nonlinear dispersion and uneven dispersion, and is usually used in the visible light band.
PGP (Prism Grating Prism) combination: using a grating as the core and combining it with a prism to achieve linear dispersion, but the production cost is high and the system volume is large.
2. Focusing imaging system: precise transmission of optical signals
The dispersed monochromatic light needs to be focused onto the detector image plane through a focusing imaging system (such as a lens group). The system needs to meet the requirements of wide-angle, large aperture, and wideband, and eliminate color difference to achieve planar imaging, ensuring clear separation of spectral lines. For example, the ICP spectrometer uses a mid step grating combined with prism cross dispersion to balance light flux and resolution.
3. Detector: Conversion of optical signals to electrical signals
The detector needs to have high sensitivity, low noise, and fast response characteristics:
CCD (Charge Coupled Device): Suitable for wideband detection, high-resolution spectral acquisition is achieved through surface or linear array structures. For example, the VeritySD1024G spectrometer uses TEC cooled CCD to reduce dark current noise and improve signal-to-noise ratio.
Photodiode array: used for high-speed detection scenarios, such as LIBS spectrometers that require element analysis to be completed in milliseconds, with high requirements for detector response speed.
4. Signal processing system: data optimization and output
After amplification and filtering, electrical signals are converted into digital signals, and algorithms are used to eliminate noise and correct wavelength drift, ultimately generating spectral images or data. For example, a spectrometer establishes a working curve through standard samples to achieve quantitative analysis of element content.