CN103149158B - A kind of biprism water quality monitoring optical fiber sensing system - Google Patents

Abstract

A double prism water quality monitoring optical fiber sensing system includes two parts: an optical probe 20 and a monitoring unit 10. The optical probe includes a collimator 22, rectangular prisms 23 and 24, a converging lens 25 and the like. The monitoring unit is composed of a light source 11 , a spectrometer 14 and a computer 15 . The light emitted by the light source is strobed by the 1×N optical switch 12, transmitted to the probe along the optical fiber 31, transformed into a thin parallel beam by the collimator, reflected and translated between the double prism structures, so that the probe light penetrates between the prisms four times The water body to be measured is finally coupled to the optical fiber 32 by the converging lens 25, and then transmitted to the spectrometer and computer through the selected 1×N optical switch 13 to complete the time-sharing distributed detection. The bottom surfaces of the two isosceles right-angled prisms are parallel, and the right-angled edges are perpendicular to each other. The detection signal is analyzed by a spectrometer and a computer, and the water quality characteristics are characterized according to the spectral characteristics of the water. The optical fiber sensing system uses micro-probes for distributed real-time online monitoring of water quality, with instant early warning and high detection sensitivity.

Description

A double prism water quality monitoring fiber optic sensor system

technical field

The invention relates to a water quality monitoring optical fiber sensing system, in particular to a micro-probe that uses a double prism reflecting pool to increase the effective optical path, uses optical fiber sensing to realize the transmission of monitoring signals, and detects the spectral characteristics of water quality for real-time on-line analysis The invention relates to a multi-point distributed monitoring sensor network for water quality status, which belongs to the field of test instruments.

Background technique

Today's society vigorously advocates sustainable development and green environmental protection, but unreasonable human activities lead to changes in the physical and chemical characteristics of water bodies, resulting in deterioration of water quality, serious pollution of the ecological environment, and direct harm to people's lives and health. Therefore, the monitoring of water pollution is an important aspect of environmental protection. Among them, the degree of water pollution has a certain relationship with its spectral characteristics: if the water contains more trace impurities such as suspended particles, organic macromolecules, or heavy metal ions, it will absorb and scatter light, making the original transparent and colorless water Produce turbidity. The more serious the water pollution, the lower the light transmittance. The light transmittance of sewage is related to the content, composition, size, shape and absorption, reflection and scattering characteristics of the surface of the impurities in the water. These factors will significantly change the water quality. The transmittance spectral characteristics. At present, the spectral methods for detecting water quality include scattering method, transmission method, etc., and the ratio method combining the two. Generally, the detection beam is modulated and then irradiated into the water body to be tested in the sample pool, and then the photoelectric detector is used to detect the corresponding Light scattering or transmission output signals, this method can realize the water quality detection in the laboratory environment, but it is not suitable for the online real-time monitoring of water quality. The invention adopts an optical fiber double prism combination system: the double prism can increase the effective distance between light and water, improve detection sensitivity, and the optical fiber can realize on-line long-distance transmission processing of on-site real-time sensing signals. The structure essentially monitors water quality by using spectroscopy, and characterizes water quality characteristics through the absorption and scattering of light by impurities in the water.

Contents of the invention

The purpose of the present invention is to provide a real-time online optical fiber sensing and detection system for water quality in view of the characteristics that most existing water quality detectors cannot monitor in real time and have low detection sensitivity.

The present invention adopts following technical scheme:

The optical fiber sensing system for double prism water quality monitoring includes two parts, a probe and a monitoring unit, which are connected by optical fiber.

The probe includes a launching fiber interface, a collimator, a first right-angle prism, a second right-angle prism, a converging lens, and a receiving fiber interface. The collimator converts the light transmitted by the optical fiber into thin parallel light as the detection beam, passes through the water body to be measured, and hits the first prism. After being reflected and translated by the first prism, it returns along the direction parallel to the original incident direction. After passing through the measured water body again, and being reflected and translated by the second prism, it returns along the direction parallel to the original incident direction again, and passes through the measured water body for the third time, and finally is reflected and translated by the first prism, and passes through the measured water body for the fourth time. The water body is measured, and the light beam is sent to the converging lens, and then transmitted to the receiving optical fiber that is bundled with the emitting optical fiber.

The prisms are all isosceles right-angle prisms, the right-angle edges are perpendicular to each other, and the two bottom surfaces are parallel. The distance between the two bottom surfaces is adjustable and uniformly determined to be the same value according to the actual monitoring requirements of the water area to be measured. The bottom of the first right-angle prism faces the interface of the launching fiber to ensure that the light emitted by the launching fiber hits the bottom of the first prism vertically, and the shape and size of the bottom of the second prism should be able to cover the lower half of the first prism to ensure the integrity of the reflection area .

The transmitting fiber interface of the probe, the collimator, the first right-angle prism, the second right-angle prism, the converging lens, the receiving fiber interface and other components are fully adjusted and fixed and packaged as one. The bracket material can not only fix the optical element, but also withstand a certain water pressure and adapt to the environment of the water body to be measured. A thin glass baffle with high transmittance to the probe light is attached to the bottom of the two prisms to isolate the water body from the probe optics. The bracket material between the two glass baffles has enough vacancies to ensure that water can freely flow through the space between the two glass baffles and ensure that the position of the internal optical components is fixed and the optical path is smooth in terms of structural strength. Two surfaces are vacant, or only four prisms are reserved, or only one side of the bracket material is reserved, as long as the bracket material is sufficient to ensure the smooth flow of the internal light path. The transmitting fiber interface and the receiving fiber interface adopt standard and common fiber interfaces. The size of the two interfaces determines the minimum size of the probe, thus also determines the minimum size of the two rectangular prisms. That is, the size of the standard fiber optic interface determines the miniaturization of the probe.

The front end of the transmitting fiber interface is equipped with a collimating mirror to transform the light into a thin parallel beam; the front end of the receiving fiber interface is equipped with a converging lens to ensure that the detection light is fully received. The distance between the central axis of the collimator and the converging lens is twice the vertical distance between the central axis of the collimator and the right-angled edge of the second prism. Therefore, after the size and installation position of the two prisms are determined, the position of the collimator will determine the entire reflected light path.

After all the probes are respectively connected with the transmitting optical fiber and the receiving optical fiber, they are put into each monitoring point of the water area to be measured. The detection beam passes through the measured water body four times in total, which effectively increases the distance between the light and the water.

The monitoring unit includes a light source, two 1×N optical switch arrays, a fiber optic spectrometer and a computer for signal processing.

The light source adopts a high-power wide-spectrum light source or a tuned laser, which can scan water quality with multiple bands in one measurement, and can more comprehensively analyze and characterize water quality characteristics. Since the probe is directly put into the water, there is a certain depth, and the interference of natural light can be ignored, so the wide spectrum can include the visible light band.

1×N optical switches are all controlled by the computer, and only one transmission light and the corresponding receiving light signal are connected each time, that is, all the light emitted by the light source is input into one transmission fiber only, and only one probe detection signal is processed at a time . This quasi-distributed time-sharing monitoring system can not only ensure the intensity of the detection light, but also facilitate the demodulation of the detection signal. The 1×N optical switches can be cascaded in corresponding multi-stages at the transmitting end and the receiving end to increase the monitoring optical path.

The signal conditioning unit adopts a fiber optic spectrometer, and its internal main components include: long-pass absorption filter, collimator, grating, focusing mirror, photodetector, etc. The optical fiber spectrometer completes the photoelectric conversion and demodulation of the detection light, and displays the detection results on the computer connected to it, and uses the relevant spectral analysis software on the computer to analyze and process the signal, so as to obtain the water quality monitoring results, which are correlated by the computer. Device storage, printing, alarm, etc.

The present invention has the following advantages: ① The present invention uses optical fiber to transmit light to realize online long-distance transmission processing of on-site real-time sensing signals, which is conducive to arranging multi-point monitoring to form a sensor network, real-time online monitoring of a water area, and real-time early warning , to ensure water safety. ②The sensor head of the present invention has been packaged into a micro-probe with an interface reserved, adjustable and replaceable, plug and play for easy installation, and can be directly put into the water body to be measured for on-site real-time monitoring. ③ The present invention uses two right-angle prisms to make the detection light pass through the measured water body 4 times in a limited space, which increases the distance between light and water and is beneficial to the miniaturization of the probe. The spectral characteristics of water are detected, and the effects of water on light scattering and absorption are considered at the same time, which improves the detection sensitivity, reduces the detection threshold of water pollution, and broadens the detection range.

Description of drawings

Fig. 1 is a schematic diagram of the system sensing principle of the present invention. In the figure: 10-monitoring unit: 11-light source; 12 and 13-1×N optical switches; 14-fiber optic spectrometer; 15-computer. 20 - Probe. 31-launch fiber; 32-receive fiber.

Fig. 2 is an enlarged view of taking out one monitoring optical path in Fig. 1, mainly illustrating the probe part, 20-probe: 21-launch fiber interface; 22-collimator; 23-the first right-angle prism; 24-the second right-angle prism; 25-converging lens; 26-receiving optical fiber interface. The other components are the same as in Figure 1.

Figure 3 is a distribution diagram of the internal components of the probe.

Fig. 4 is a schematic diagram of the spatial positions of two rectangular prisms in the probe.

Figure 5 is a left side view of the position of the two rectangular prisms inside the probe.

Figure 6 is a top view of the positions of the two rectangular prisms inside the probe.

detailed description

Fig. 1 is a principle schematic diagram of a double prism water quality monitoring optical fiber sensing system provided by the present invention. It mainly includes two parts, a monitoring unit 10 and a probe 20 , which are connected by a transmitting optical fiber 31 and a receiving optical fiber 32 . The monitoring unit 10 includes a light source 11 , a transmitting 1×N optical switch 12 , a receiving 1×N optical switch 13 , a fiber optic spectrometer 14 , and a computer 15 .

FIG. 2 is a diagram of the probe: the probe 20 includes a transmitting fiber interface 21 , a collimator 22 , a first right-angle prism 23 , a second right-angle prism 24 , a converging lens 25 , and a receiving fiber interface 26 .

When the system is working, the monitoring unit 10 is in the monitoring center, and the probe 20 is directly put into the water area to be measured and arranged at multiple monitoring points. The light emitted by the light source 11 is selected by a 1×N optical switch 12 controlled by the computer, and transmitted to the probe 20 along the emitting optical fiber 31 of the path. In the probe 20, the light interacts with the water, and the probe light modulated by the water is transmitted to the fiber optic spectrometer 14 along the receiving optical fiber 32 and the 1×N optical switch 13 gated by the computer. The optical fiber spectrometer 14 completes the photoelectric conversion and demodulation of the detection light, and transmits the detection signal to the computer 15 connected thereto. The computer 15 analyzes and processes the signal to obtain the water quality monitoring result.

Fig. 3 is a working principle diagram of the probe 20: the receiving optical fiber interface 21 is connected to the emitting optical fiber 31, the collimator 22 converts the light into thin parallel light and emits it to the area of the water body to be detected, and then the detection light hits the first rectangular prism 23, After being reflected and translated by the first prism 23, it returns along the direction parallel to the original incident direction, passes through the detected water body area again, and is reflected and translated by the second prism 24, then returns along the direction parallel to the original incident direction again, and passes through the detected water body area again. Pass through the detected water body area three times, and finally pass the first prism 23 to translate, reflect, and pass through the detected water body area for the fourth time, and transmit the light beam to the converging lens 25 and transmit it to the Monitoring unit 10. The optical fiber spectrometer 14 and the computer 15 of the monitoring unit 10 analyze and process the detection light to realize real-time online multi-point distributed monitoring of water quality.

The first right-angle prism 23 and the second right-angle prism 24 of the probe 20 adopt a material with a wider light transmission band and higher light transmittance. If necessary, the bottom surfaces of the two right-angle prisms can be plated with an anti-reflection film in relevant wave bands to reduce the prism surface reflection.

In the technical solution of the present invention, optical fibers are used to transmit light over a long distance, and multiple probes are directly put into water. The degree of pollution of the water body is different, and the trace impurities are different. The spectrum of the emitted light is different from the original emitted light. The system records, demodulates and analyzes in real time, and can conduct real-time online multi-point distributed monitoring of water quality.

The light source 10 adopts a high-power wide-spectrum light source or a tuned laser, which can scan water quality with multiple bands in one measurement, and can more comprehensively analyze and characterize water quality characteristics. Since the probe is directly put into the water, there is a certain depth, and the interference of natural light can be ignored, so the wide spectrum can include the visible light band. The 1×N optical switches 12 and 13 enable only one optical path to be selected for each detection, which can ensure the intensity of the detection light and is also beneficial to demodulate the detection signal. The 1×N optical switches can be cascaded in corresponding multi-stages at the transmitting end and the receiving end to increase the monitoring optical path.

The signal conditioning part of this system adopts the combination of fiber optic spectrometer 14 and computer 15, and directly uses the fiber optic spectrometer 14 to demodulate the detection signal and then input it into the computer 15. Using the standard curve of the corresponding relationship between the spectrum and water pollution previously calibrated, the current measured water body can be analyzed. Real-time online multi-point distributed monitoring of pollution degree.

This system uses a right-angle prism reflection system to increase the detection optical path, which is conducive to improving the sensing sensitivity and reducing the detection threshold, while ensuring the miniature design requirements of the optical probe, better monitoring the water quality with low pollution levels, and ensuring water quality, especially for drinking water and Breeding water is safe.

Claims (1)

1. A double prism water quality monitoring optical fiber sensing system, including two parts: a miniature optical probe (20) and a monitoring unit (10). The miniature optical probe includes a launch fiber interface (21), a collimator (22), a first right angle The prism (23), the second rectangular prism (24), the converging lens (25) and the receiving fiber interface (26); the transmitting fiber interface (21) and the receiving fiber interface (26) are packaged side by side at the same end of the probe; the monitoring unit includes a light source (11), 1×N optical switches (12) and (13), spectrometer (14), computer (15), constitute a time-sharing distributed detection system, and the system shares a set of light source and signal conditioning equipment; isosceles right-angle prism Bottoms are parallel, the right-angled edges are perpendicular to each other, and the distance between the two prism bottoms can be adjusted; the shape and size of the bottom of the second right-angled prism (24) will cover the lower half of the first right-angled prism (23), and the first right-angled prism (23) can The beam direction moves between the prisms, that is, the distance between A ₁ B ₁ C ₁ D ₁ and A ₂ B ₂ C ₂ D ₂ on the bottom surface is adjustable; spectrometers and computers are used to analyze the outgoing signals that pass through the measured water body 4 times.