UV Visible Fiber Spectrometer

Spectral instruments are an important component of optical instruments. They are basic equipment that applies optical principles to measure, analyze, and process the structure and composition of substances. They have the advantages of high analysis accuracy, large measurement range, and fast speed. Ordinary spectrometers can only detect visible light wavelengths of 400-800nm, while in some special fields, it is necessary to detect ultraviolet light wavelengths of 200-400nm.

At present, most micro UV spectrometers on the market use back thinning or coated CCD as the photosensitive element, which is relatively expensive. Therefore, this article proposes a design scheme of applying a cost-effective CMOS sensor chip to UV visible spectrometers. The system uses optical fibers as the light guide element, and performs spectral processing through gratings. The processed light beam is parallel projected onto the surface of the sensor, and then converted into electrical signals. After A/D conversion, signal storage and transmission in the circuit part, the data is uploaded to the upper computer for spectral image display and analysis design. In order to obtain a uniform monochromatic and high-resolution parallel light beam for the sensor photosensitive element, a set of optical systems with reasonable structure and size needs to be built.

Finally, the article verified through experimental comparison that the micro UV visible fiber spectrometer designed using this scheme has good UV sensitivity, with a spectral range of 200nm to 400nm and a resolution of up to 2.0nm.

Application Principle

During testing，Connect the fiber optic spectrometer to the computer（USB port）And power on，Open the software corresponding to the instrument，openDeuterium halogen lampoflight source，Deuterium halideThe composite light emitted by the lamp passes through the fiber optic cable and reaches the optical path length of 1 through the fiber optic probe0Mm open flow pool，The partially absorbed light is then reflected by the coating mirror and transmitted through the optical fiber to reach the slit andflatSurface grating monochromator，fromCMOS sensorConvert optical signals into corresponding electrical signals，After further processing by the core data chip，Convert electrical signals into digital signals and display them on a computer. The spectrometer selected for this instrument has a wavelength range of 200-400nm，The wavelength accuracy is±0.3nm，The wavelength reproducibility is ± 0.1nm（Wavelength temperature drift 0.4nm/10 ℃）.

Samples and testing methods

This test sample consists of five types of test samples:

Calcium chloride, chloride&potassium, sodium bromide, sodium iodide, sodium chloride solution (100ppm, 200ppm, 500ppm, 800ppm, 1200ppm, 2000ppm, 3000ppm, 5000ppm, 8000ppm, 10000ppm)

Adopting Opu Tiancheng (Xiamen) Optoelectronics Co., LtdThe ATP2002 ultraviolet visible micro fiber spectrometer produced.

Test conditions: Integration time of 7 ms, average frequency of 5 times, scanning range of 180-420nm, room temperature.

Test results and analysis

4.1 Comparison chart of absorbance between 100-10000ppm calcium chloride solution

4.2 Comparison chart of absorbance of 100-10000ppm chloride&potassium solution

4.3 Comparison of absorbance of sodium bromide solution at 100-10000ppm

4.4 Comparison of absorbance of sodium iodide solution at 100-10000ppm

4.5 Comparison chart of absorbance of sodium chloride solution at 100-10000ppm

4.6 Horizontal comparison data of absorbance of five samples

4.6.1 100ppm absorbance comparison chart

4.6.2 1200ppm absorbance comparison chart

4.6.3 2000ppm absorbance comparison chart

4.6.4 Comparison chart of 10000ppm absorbance

Conclusion

This article introduces the basic principle of spectrophotometry, and verifies through relevant experiments that the spectrometer has good measurement accuracy and stability, providing a large amount of raw data for testing the absorbance of solutions using fiber optic spectrometers. This spectrometer can be widely used for detecting the absorbance of solutions.