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Monochromator refers to an instrument that separates monochromatic light with an extremely narrow wavelength range from a beam of electromagnetic radiation. According to the dispersive element, monochromators can be divided into prism monochromators and grating monochromators. Among them, a grating spectrometer is an instrument that uses a grating as the optical element to obtain monochromatic light through grating diffraction. For transmission and absorption spectra, the intensity of the monochromatic light separated by a grating spectrometer is usually relatively weak, so the actual measurement signal is easily submerged in external noise, making it difficult to measure accurately with conventional methods. However, a spectral measurement system built with a lock-in amplifier and a chopper modulator only measures the light intensity at the modulation frequency, thus avoiding the influence of other external noise and enabling high-precision detection of weak light. The figure below shows an actual spectral measurement platform built with the OE series lock-in amplifier and chopper:
Diagram of spectral measurement (F: SSI OE3001optical chopper G: grating spectrometer B: photoelectric probe
D: praseodymium rubidium glass samples C: sample box E: bromine tungsten light source H: computer)
After the light emitted by the light source is modulated by the OE3001 chopper, it becomes light carrying specific frequency information. The modulated light then passes through a grating spectrometer and is converted into monochromatic light. When this monochromatic light irradiates the sample, the sample absorbs light of specific wavelengths according to its structural characteristics. The remaining light strikes Probe B and is converted into an electrical signal, whose weak intensity is detected by a lock-in amplifier. The figure below presents the actual setup of the spectral measurement system:
In actual measurement, a computer controls the grating spectrometer to perform scanning, and corresponding measurement data are read from the lock-in amplifier to obtain a complete spectrum.The OE series lock-in amplifiers are compatible with monochromators and supporting spectral measurement software of mainstream brands including Zolix and Beijing Beiguang Century. Common software such as ZolixScan and GMCS can be directly matched to build a high-precision weak light measurement system.The figure below shows the actual measurement results of a mercury lamp:
