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CN-121347388-B - Optical window pollution self-immunity water transparency detector

CN121347388BCN 121347388 BCN121347388 BCN 121347388BCN-121347388-B

Abstract

The invention discloses an optical window pollution self-immunity water transparency detector in the technical field of environmental monitoring and water analysis, which comprises a light source, a first reflecting mirror, a spectroscope, a sample cell, a second reflecting mirror and a third reflecting mirror, wherein the first reflecting mirror reflects light of the light source to the spectroscope, the spectroscope divides the light into transmitted light and reflected light, the transmitted light passes through the sample cell and is converged on a transmission-end photoelectric detector by the second reflecting mirror, the reflected light is converged on a reference-end photoelectric detector by the third reflecting mirror, and the water transparency can be calculated according to the light intensity of the transmission-end photoelectric detector and the reference-end photoelectric detector. The invention dynamically counteracts errors caused by optical window pollution, light source fluctuation and detector drift by a double-ratio real-time compensation algorithm of double-light-path signals and pollution errors of the clean and pollution windows, can ensure measurement accuracy without a physical cleaning device, can monitor the variation trend of the light intensity ratio, and actively senses the pollution degree of the optical window.

Inventors

  • ZHOU XUEFEI
  • Shen Guxuan
  • ZHANG YALEI
  • LIU TONGCAI
  • CHEN JIABIN
  • An Beiya

Assignees

  • 同济大学

Dates

Publication Date
20260508
Application Date
20251020

Claims (8)

  1. 1. An optical window pollution self-immunity water transparency detector which is characterized in that: the detector comprises a light source (1), a first reflecting mirror (2), a spectroscope (3), a sample cell (4), a transmission end photoelectric detector (5), a reference end photoelectric detector (6), a modulation driving circuit (7), a transmission signal conditioning circuit (8), a reference signal conditioning circuit (9), a second reflecting mirror (10), a third reflecting mirror (11) and a processing display unit; The light source (1), the first reflecting mirror (2), the spectroscope (3), the sample cell (4), the transmission end photoelectric detector (5) and the second reflecting mirror (10) form a perspective light path together, the modulation driving circuit (7) generates sine modulation signals with specific frequency, and drives the light source (1) to emit modulated light, and the modulated light is reflected by the first reflecting mirror (2) to form parallel light, which is called incident light, and the incident light irradiates the spectroscope (3); the spectroscope (3) is of a planar structure, after the incident light irradiates the spectroscope (3), a part of the incident light is transmitted from the spectroscope (3), and the rest of the incident light is reflected by the spectroscope (3); The sample cell (4) is made of an optical transparent corrosion-resistant material, the area of the sample cell (4) irradiated by incident light is called an optical window, the incident light irradiates on the optical window and penetrates through the sample cell (4) to be called transmitted light, the transmitted light irradiates on a second reflecting mirror (10), the second reflecting mirror (10) reflects the transmitted light to a transmission-end photoelectric detector (5), and the transmission signal conditioning circuit (8) is connected with the transmission-end photoelectric detector (5) to convert an optical signal received by the transmission-end photoelectric detector (5) into an electric signal; The spectroscope (3), the reference end photoelectric detector (6) and the third reflecting mirror (11) form a reflecting light path together; the incident light is reflected by the spectroscope (3) to form reflected light, the reflected light irradiates on the third reflecting mirror (11), the third reflecting mirror (11) reflects the reflected light to the reference end photoelectric detector (6), and the reference signal conditioning circuit (9) converts an optical signal on the reference end photoelectric detector (6) into an electric signal; The processing display unit comprises a signal acquisition module and a microprocessor, wherein the signal acquisition module is connected with a transmission signal conditioning circuit (8) and a reference signal conditioning circuit (9) and is used for converting electric signals of the transmission signal conditioning circuit (8) and the reference signal conditioning circuit (9) from analog quantities to digital quantities, which are respectively called transmission end signals and reference end signals; The detection method comprises the following steps: S1, injecting a pure water sample into a sample tank (4) in a clean state of an optical window, recording and storing a transmission end signal I_measure and a reference end signal I_ref at the moment by a processing display unit, and calculating a reference ratio R_clean=I_measure/I_ref; S2, injecting a water sample to be detected into the sample tank (4), and acquiring a transmission signal value I_measure and a reference signal value I_ref in real time by the processing display unit; s3, calculating the ratio R=I_measure/I_ref of the transmission signal and the reference signal, comparing the ratio R=I_measure/I_ref with a clean reference ratio, compensating the pollution error of the optical window in real time, and outputting the corrected water body transmissivity T_water=R/R_clean; S4, calculating an SDD value of the water body according to the T_water and the built-in transmissivity and Szechwan disk depth calibration model, and if the R value continuously drops to a preset threshold value, sending out an alarm for recalibrating or disassembling the cleaning sample tank by the processing display unit.
  2. 2. The optical window pollution self-immunity water transparency detector according to claim 1, wherein: the first reflecting mirror (2), the second reflecting mirror (10) and the third reflecting mirror (11) are parabolic reflecting mirrors, the light source is arranged at the focus of the first reflecting mirror (2), the transmission end photoelectric detector (5) is arranged at the focus of the second reflecting mirror (10), and the reference end photoelectric detector (6) is arranged at the focus of the third reflecting mirror (11).
  3. 3. The optical window pollution self-immunity water transparency detector according to claim 2, wherein: The first reflecting mirror (2), the second reflecting mirror (10) and the third reflecting mirror (11) are made of aluminum alloy, and the reflecting surface is plated with an enhanced high-reflection protective film applicable to near infrared wave bands.
  4. 4. The optical window pollution self-immunity water transparency detector according to claim 1, wherein: The light source (1) is a near infrared LED lamp set, and the wavelength is 840-910 nm; The number of the near infrared LED lamp groups is 6-10; the near infrared LED lamp group is arranged in the detachable quartz sleeve.
  5. 5. The optical window pollution self-immunity water transparency detector according to claim 1, wherein the transmittance of the spectroscope is 50% -70%.
  6. 6. An optical window pollution self-immune water transparency detector according to claim 1, wherein the material of the sample cell (4) is fused silica or borosilicate glass.
  7. 7. The optical window pollution self-immunity water transparency detector according to claim 1, wherein: The transmission-end photoelectric detector (5) and the reference-end photoelectric detector (6) are silicon photodiodes, namely Si Photodiode.
  8. 8. The optical window pollution self-immunity water transparency detector according to claim 1, wherein the transmission light path is perpendicular to the reflection light path.

Description

Optical window pollution self-immunity water transparency detector Technical Field The invention relates to the technical field of environmental monitoring and water analysis, in particular to a water transparency detector for optical window pollution self-immunity. Background The water transparency is one of important visual indexes for evaluating the quality of water, and is widely applied to water quality monitoring and evaluating works of water bodies such as rivers, lakes, reservoirs, offshore and the like. The traditional measuring method such as the Saiki disk method is simple, but is greatly influenced by human judgment and illumination conditions, has low efficiency, can not realize online continuous monitoring, and is difficult to meet the requirements of a modern water quality monitoring network on data real-time performance and continuity. To cope with this demand, existing on-line optical transparency instruments have been developed, which mostly employ a direct light path structure, and back calculate transparency by measuring the attenuation degree of light after passing through a water sample. The instrument is gradually applied to the scenes of river length management, water source safety early warning, sewage treatment plant water outlet monitoring, aquaculture water quality monitoring, intelligent environment-friendly Internet of things and the like. However, in the long-term and unattended deployment process of the instrument in the scene, a common and serious technical challenge is faced, namely, the optical window of the instrument is inevitably polluted by microorganism adhesion, algae breeding, sediment deposition, oil stain adhesion and the like, so that the light transmittance of the window is continuously reduced, the measurement signal is seriously drifted, and huge measurement errors are generated. Meanwhile, the acquisition efficiency of the original optical signals is reduced, so that the detection range of the instrument is affected. At present, the main solutions of the problem of pollution to an optical window in the industry comprise two types, namely, relying on frequent manual cleaning and maintenance, which bring about huge workload and high operation and maintenance cost and cause interruption of monitoring data, and adopting active cleaning devices such as mechanical scraping, ultrasonic cleaning or chemical cleaning, which obviously increase the complexity, cost power consumption and failure rate of the system. In the aspect of optical compensation technology, there are schemes adopting a dual-optical-path design in the prior art, in an attempt to compensate the influence of factors such as light source fluctuation through a reference optical path. However, these conventional dual-path compensation schemes have significant limitations in that they generally compensate for aging or fluctuations in the light source itself, and cannot effectively attenuate the common path due to contamination of the optical window. Since the transmission light path and the reference light path are often affected to different extents when the optical window is contaminated, resulting in a considerable compromise of the compensation effect. In addition, the schemes lack real-time diagnosis capability on pollution degree, and early warning prompt maintenance cannot be performed before signal distortion, and periodic manual intervention is still needed. Therefore, developing an on-line transparency detector which can immune or automatically compensate window pollution effect from measurement principle and has high reliability, low maintenance and long period stability has become an urgent technical problem for breaking through the application bottleneck of industry and promoting the development of water quality monitoring technology. Disclosure of Invention Aiming at the problems in the prior art, the invention provides an optical window pollution self-immunity water transparency detector, which is characterized in that a double-light-path structure is constructed by adopting three parabolic reflectors for the first time, one light path is used for transmitting a sample, the other light path is used for reference, and the water transparency can be calculated by measuring the light intensity of the two light paths. The technical scheme of the invention is as follows: the utility model provides a water transparency detector of optics window pollution autoimmunity, includes light source 1, first speculum 2, spectroscope 3, sample cell 4, transmission end photoelectric detector 5, reference end photoelectric detector 6, modulation drive circuit 7, transmission signal conditioning circuit 8, reference signal conditioning circuit 9, second speculum 10, third speculum 11, processing display element; The light source 1, the first reflecting mirror 2, the spectroscope 3, the sample cell 4, the transmission end photoelectric detector 5 and the second reflecting mirror 10 form a perspective light path