What Is a Spectroradiometer?

Spectrometer, also called spectrometer, is widely known as direct reading spectrometer. A device for measuring the intensity of spectral lines at different wavelength positions with photodetectors such as photomultiplier tubes. It consists of an entrance slit, a dispersion system, an imaging system, and one or more exit slits. The dispersive element is used to separate the electromagnetic radiation of the radiation source into the required wavelength or wavelength region, and the intensity is measured at the selected wavelength (or scanning a certain band). Divided into two types of monochromator and polychromator.

Spectroscope is the decomposition of light with complex components into

According to modern

A typical spectrometer consists of an optical platform and a detection system. It includes the following main sections:

1. Incident slit: The object point of the spectrometer imaging system is formed under the illumination of incident light.

2. Collimation element: Make the light from the slit become parallel light. The collimating element may be an independent lens, a mirror, or a direct integration on a dispersive element, such as a concave grating in a concave grating spectrometer.

3. Dispersion element: Gratings are usually used to disperse optical signals into multiple beams in space according to wavelength.

4. Focusing element: Focuses the dispersed beam to form a series of images of the entrance slit on the focal plane, where each image point corresponds to a specific wavelength.

5. Detector array: placed on the focal plane and used to measure the light intensity of each wavelength image point. The detector array may be a CCD array or another kind of light detector array.

There are many types of spectrometers and many classification methods. According to the principle of decomposition spectrum used in spectrometers, they can be divided into two categories: classic spectrometers and new spectrometers. The classic spectrometer is an instrument based on the principle of spatial dispersion (spectroscopy); the new spectrometer is an instrument based on the modulation principle, so it is also called a modulation spectrometer. ^[1]

Spectrometers are widely used in agriculture, astronomy, automotive, biology, chemistry, coating, colorimetry, environmental testing, thin film industry, food, printing, papermaking, Raman spectroscopy, semiconductor industry, composition testing, color mixing and matching, biology It is widely used in medical applications, fluorescence measurement, gem composition detection, oxygen concentration sensor, vacuum chamber coating process monitoring, film thickness measurement, LED measurement, emission spectrum measurement, UV / visible absorption spectrum measurement, and color measurement. ^[3]

The spectrometer's transmittance or its efficiency can be measured with an auxiliary monochromator device. There are no difficulties in achieving these measurements in visible and near UV. The transmittance of the second monochromator is determined in this way by measuring the luminous flux passing through the first monochromator, followed by measuring the luminous flux passing through the two monochromators.

Absolute measurement requires knowing the absolute transmittance of the monochromator: for relative measurement, the transmittance can be measured in relative units at various wavelengths. These measurements of vacuum ultraviolet have considerable experimental difficulties, so auxiliary monochromators are usually used. The efficiency of the diffraction grating is measured separately at various incident angles. Calibration difficulties have been successfully avoided in many experimental steps.

The relationship between grating efficiency and wavelength, incident angle, coating thickness, coating material, and other factors has been studied. All these measurements indicate that in many cases the energy loss is very significant and the efficiency of the grating is less than 1%, and different parts of the grating may have significantly different efficiencies.