CN102128810B - Seawater salinity detection device with prism model capable of refracting for multiple times - Google Patents

Abstract

A seawater salinity detection device with multiple refraction of the prism model, including a host computer, a right-angle prism, and a signal acquisition and processing module. An optical glass perpendicular to the laser exit light path is arranged below the laser and the position sensitive device of the device, and is connected with the The exit light path of the laser forms an acute angle α ₁ and an obtuse angle β ₁ to form a set of two pieces of optical glass of a prism model, and above the right-angle prism, there is an acute angle α ₂ and an obtuse angle β ₂ in the opposite direction to the exit light path of the laser. The optical glass of the prism model; the optical glass and the housing of the device are enclosed into a closed upper reference cavity filled with reference liquid, and the optical glass is enclosed with the housing at the bottom of the device to contain a rectangular prism and be filled with Closed lower reference chamber for reference fluid. The invention has the advantages of simple structure and convenient use. The prism model enlarges the deflection angle of the light to improve resolution, accuracy and anti-interference ability, shortens the length of the instrument, and reduces equipment cost and measurement cost.

Description

Seawater salinity detection device with multiple refraction of prism model

technical field

The invention relates to a seawater salinity detection device, in particular to a seawater salinity detection device with multiple refraction of a prism model, which belongs to the fields of photoelectric sensing and marine environment monitoring.

Background technique

In addition to the conductivity method, seawater salinity detection mainly includes photoelectric detection of seawater salinity using optical refraction, that is, optical refraction seawater salinity detection. The nature of causing the light to shift at the receiving end enables the detection of seawater salinity. At present, for the photoelectric detection of seawater salinity, the representative abroad is the transmissive salinity sensor proposed by Hideyuki Minato and others in Japan, which uses a semiconductor laser as a light source and uses optical fibers to transmit optical signals. Its shortcoming is long-distance transmission The signal process is cumbersome and relatively large in size. Domestically, in 2002, Zhao Yong of Tsinghua University and others proposed an optical fiber sensor system for simultaneous real-time detection of seawater temperature and salinity, and in 2009 it was improved to a photoelectric seawater salinity detection system based on a position sensitive device (PSD). According to the principle experiment research, the resolution of salinity detection is 1.67‰, which is still lower than the requirements for actual use; in 2009, Li Tianze et al. proposed a new type of liquid concentration detection device with double isolation windows for light transmission, the error is about 8%, and the error is also bigger. It can be seen that the detection accuracy of the above methods is relatively low. Comprehensive analysis shows that the optical path of the above detection methods is a parallel plate model, and the detection is performed after the light is refracted once. The existing seawater salinity detection technology by optical refraction method is shown in Fig. 4. In Fig. 5 (expanded view of the optical path in Fig. 4), the measuring liquid between the front and rear two parallel optical glasses can be regarded as a parallel plate, and the incident light The deflection angle when the reference liquid enters the measurement liquid is determined by the refractive index of the reference liquid and the measurement liquid, and the offset on the PSD is determined by the deflection angle and the distance between the front and rear optical lenses. The light in the reference liquid is always Parallel light will not increase the offset of the system. It can be seen that the model only refracts once. Even if multiple parallel optical glasses are installed in the system, the model is still a parallel plate, which cannot effectively increase the deflection angle. Therefore, for To improve the resolution, the optical path must be increased, which will inevitably make the instrument bulky, and increasing the optical path will adversely affect the stability of the system. It can be seen that it is difficult to improve the detection resolution and accuracy of this method.

Contents of the invention

The object of the present invention is to provide a seawater salinity detection device with multiple refraction of the prism model to overcome the deficiency of low detection accuracy of the seawater salinity detection device of the current optical refraction method.

The technical idea of the present invention is: using a prism model with a larger deflection angle relative to the parallel plate model, by arranging a plurality of refraction units, the deflection angle of the device is enlarged to improve detection sensitivity and accuracy, and shorten the optical path, reduce the Reduced instrument size.

A seawater salinity detection device with multiple refraction of a prism model, comprising a right-angle prism arranged at the bottom of the device, and a signal acquisition and processing module arranged in a signal processing cavity at the top of the device and connected to a host computer through a cable, said The signal acquisition and processing module is connected to the laser and the position sensitive device PSD respectively, and the optical glass perpendicular to the laser exit light path is arranged under the laser and the position sensitive device, and the feature is that the above optical glass is sequentially arranged between the right angle prism Two pieces of optical glass forming a group _of prism models with an acute angle α ₁ and an obtuse angle β ₁ with the laser exit light path; An obtuse angle β ₂ forms a group of optical glass with prism models; the optical glass and the housing of the device are enclosed to form a closed upper reference cavity filled with reference liquid, and the optical glass is enclosed with the housing at the bottom of the device to form an inner cavity A closed lower reference chamber containing a rectangular prism and filled with reference liquid; a protective net fixed to the housing is arranged between the upper and lower reference chambers.

In order to further expand the deflection angle of the device to improve detection sensitivity and accuracy, shorten the optical path, and reduce the volume of the instrument, multiple refraction units can be set, and a middle reference cavity can be added between the above-mentioned upper and lower reference cavities , that is, the middle reference cavity consists of two pieces of optical glass that form an obtuse angle β ₁ and an acute angle α ₁ with the laser exit light path from top to bottom, and two pieces of obtuse angle β ₂ with the opposite direction of the laser exit light path from bottom to top and the optical glass at an acute angle α ₂ ; the optical glass and the housing on the side of the device are enclosed to form a closed cavity filled with reference liquid; Body protection net.

In order to achieve an ideal refraction effect, the above-mentioned acute angle α ₁ or α ₂ is within the range of 20-70 degrees, and the above-mentioned obtuse angle β ₁ or β ₂ is within the range of 110-160 degrees; further, the above-mentioned acute angle α ₁ , α ₂ and obtuse angle β ₁ and β ₂ are 45 degrees and 135 degrees respectively so that the two adjacent pieces of optical glass are perpendicular to each other.

The above-mentioned optical glass may be quartz glass, which is corrosion-resistant and pressure-resistant, and is suitable for use in deep-water oceans. Alcohol, glycerin, carbon tetrachloride, and distilled water, whose refractive index is close to that of seawater, can be used as reference liquids. However, research has found that distilled water from a wide range of sources is the most suitable for seawater measurement, so distilled water is the preferred reference liquid.

The portion between the upper and lower reference chambers or between the middle reference chamber and the upper and lower reference chambers will be used as a measurement chamber where seawater will enter.

The measurement process of the present invention is as follows: the light emitted by the laser is vertically incident on the optical glass below it which is perpendicular to the outgoing light path of the laser, passes through the reference liquid in the upper reference cavity, and reaches the second optical glass, that is, the reference liquid and the measurement At the interface of the liquid, refraction occurs due to the difference between the reference liquid and the measurement liquid medium, and then passes through the measurement liquid in the upper measurement chamber, the middle reference chamber, the lower measurement chamber, and the reference liquid in the lower reference chamber to the right-angle prism, and passes through the right-angle prism. After turning, it passes through the lower measurement cavity, the middle reference cavity, the upper measurement cavity, and the upper reference cavity in turn, and then reaches the PSD receiving surface. Calculate the salinity value of the measuring liquid.

Among them, the measurement chamber located between the reference chambers has optical glass above and below the reference chamber, and the optical glass is at a certain angle. Since the density of the measurement liquid (seawater) is higher than that of the reference liquid (distilled water), the measurement chamber forms a prism model, and the light The deflection angle after passing through the measurement cavity is much larger than that of the parallel plate model. Every time the light passes through a prism model, the deflection angle is expanded once, unlike the parallel plate model, even if multiple parallel plate models are set, the deflection angle cannot be significantly enlarged. Therefore, multiple prism models are set, and after multiple refractions, the deflection angle of the light is enlarged, and the offset of the light spot of the outgoing light on the PSD photosensitive surface is increased, thereby improving the resolution of the system.

Obviously, the present invention is simple in structure, easy to use, and easy to carry. The prism model is used to increase the offset of light, significantly improve the resolution of the system, obtain accurate measurement results, save measurement time, and shorten the length of the instrument at the same time. , reducing equipment cost, transportation cost and measurement cost.

Description of drawings

Fig. 1 is a schematic structural view of the present invention with two groups of prism models.

Fig. 2 is a schematic structural view of the model with four groups of prisms of the present invention.

Fig. 3 is a structural schematic diagram of a group of prism models of the present invention.

Fig. 4 is a structural schematic diagram of a seawater salinity detection device of an existing parallel plate model.

FIG. 5 is an expanded view of the optical path in FIG. 4 .

FIG. 6 is an expanded view of the optical path in FIG. 1 .

FIG. 7 is an expanded view of the optical path in FIG. 2 .

Fig. 8 is a schematic diagram of the detection effect of the present invention.

Among them, 1. Signal processing cavity, 2. Upper reference cavity, 3. Middle reference cavity, 4. Lower reference cavity, 5. Cable, 6. Watertight plug, 7. Laser, 8. Position sensitive device, 9. Optical glass, 10. Reference liquid, 11. Measuring liquid, 12. Shell, 13. Protective net, 14. Right-angle prism, 15. Host computer, 16. Signal acquisition and processing module, 17-24. Optical glass, n ₀ , reference liquid Refractive index, n ₁ , the refractive index of the measuring liquid, _ng , the refractive index of the optical glass.

Detailed ways

The prism model of the present invention is shown in FIG. 3 , two pieces of optical glass 17 , 18 forming a certain angle and the measuring liquid 12 in between form a group of prism models.

As shown in Figure 1, the present invention comprises the rectangular prism 14 that is located at the bottom of the device, and the signal acquisition and processing module 16 that is connected with the host computer 15 by cable 5 and is located in the signal processing chamber 1 at the top of the device, the signal The acquisition and processing module 16 is respectively connected with a laser 7 and a position sensitive device 8, and below the laser 7 and the position sensitive device 8 is provided with an optical glass 9 perpendicular to the outgoing light path of the laser 7, which is characterized in that the above optical glass 9 is connected to a rectangular prism Between 14, two pieces of optical glass 17, 18 that form a group of prism models that are in an acute angle α ₁ and an obtuse angle β ₁ with the laser 7 exit light path are provided successively; The opposite direction of laser 7 exit light path is the optical glass 19,20 of acute angle α ₂ and obtuse angle β ₂ that form a group of prism model; The closed upper reference cavity 2 of the liquid 10, the optical glass 18, 19 and the housing 12 at the bottom of the device are enclosed to form a closed lower reference cavity 4 that contains a rectangular prism 14 and is filled with the reference liquid 10; , A protective net 13 fixed to the housing 12 is provided between the lower reference chambers 2 and 4 .

As shown in Figure 2, in order to further expand the deflection angle of the device to improve detection sensitivity and accuracy, shorten the optical path, and reduce the volume of the instrument, multiple refraction units can be set, such as the upper and lower reference cavities 2, There is also a middle reference cavity 3 between 4, that is, the middle reference cavity 3 includes two pieces of optical glass 21, 22 which form an obtuse angle β1 and an acute angle _α1 with the exit light path of the laser 7 from top to bottom, and two pieces of optical glass from bottom to bottom. And the optical glass 23,24 that is obtuse angle β ₂ and acute angle α ₂ with the opposite direction of laser 7 exit light path on the top; A closed cavity; and a protective net 13 fixed to the housing 12 is provided between the middle reference cavity 3 and the upper and lower reference cavities 2, 4; thus, the number of prism models reaches 4 groups.

In order to achieve an ideal refraction effect, the above-mentioned acute angle α ₁ or α ₂ is within the range of 20-70 degrees, and the above-mentioned obtuse angle β ₁ or β ₂ is within the range of 110-160 degrees; further, the above-mentioned acute angle α ₁ , α ₂ and obtuse angle β ₁ , β ₂ are 45 degrees and 135 degrees respectively, so that the two adjacent pieces of optical glass on the left and right are perpendicular to each other, which is convenient for processing and assembly.

The above-mentioned optical glass may be quartz glass; the above-mentioned reference liquid 10 is preferably distilled water.

The solid line in Figure 1 is the optical path when the measurement cavity is the reference liquid. At this time, the measurement liquid and the reference liquid are both reference liquids, and the light is transmitted in the same medium without refraction; the dotted line is the optical path when the measurement cavity is the measurement liquid. , at this time, since the reference liquid and the measuring liquid are not the same medium, refraction occurs; as can be seen from Figures 6 and 7, the refraction offset h _y of the present invention is significantly larger than that of the existing flat plate model.

Example 1

As shown in FIG. 2 , a device with 4 groups of prism models including a signal processing chamber 1 , an upper reference chamber 2 , a middle reference chamber 3 and a lower reference chamber 4 is used. A laser 7, a PSD and a signal acquisition and processing module 16 are arranged in the signal processing chamber 1, wherein the PSD can be welded on the signal acquisition and processing module 16, and is controlled by the signal acquisition and processing module 16 together with the laser 7. The cable 5 is connected with the signal acquisition and processing module 16 in the signal processing cavity 1 through the watertight plug 6, and supplies power to the circuit board and communicates with the host computer 15. All three reference chambers are filled with distilled water as reference solution. The reference chambers and the protective net surround 13 to form an upper measurement chamber and a lower measurement chamber, and the measurement liquid (seawater) enters the two measurement chambers through the protective net. The protective net 13 not only effectively prevents seawater organisms and sundries from entering the measurement chamber, but also blocks most of the external stray light, effectively overcomes the influence of the system by external stray light, and improves the environmental adaptability of the system.

The laser 7 is a semiconductor laser with an output wavelength of 650nm, an exit pupil power of 1mw, and a beam diameter of Φ1mm at 1m. It has the advantages of being suitable for short-range use, small in size, stable in output light intensity, and less affected by the environment. system debugging.

The PSD adopts Japan Hamamatsu S8543 one-dimensional PSD, the size of the photosensitive surface is 0.7×24mm, and the resolution is 0.6um. It has the advantages of high resolution, fast response, low power consumption, and low cost, and is suitable for system use.

The angle between the optical lens and the light emitted by the laser is 45 degrees. When the total length of the device is 600mm, when the seawater salinity in the measurement chamber changes from 0 to 40, the offset of the light spot on the PSD photosensitive surface is 20mm, which is 5.4 of the parallel plate model. times, the resolution of salinity detection can reach 0.0012‰, significantly higher than the existing detection devices.

Figure 8 is the repeatability measurement curve of a certain measurement point of the device. It can be seen from the figure that the measurement repeatability 2σ of the device is better than 0.05‰, and the stability is good.

Claims (9)

1. A seawater salinity detection device with multiple refractions of a prism model, comprising a right-angle prism (14) located at the bottom of the device, and a cable (5) connected to the upper unit in the signal processing cavity (1) at the top of the device The signal acquisition and processing module (16) that machine (15) is connected, described signal acquisition and processing module (16) is connected with laser (7) and position sensitive device (8) respectively, and in laser (7) and position sensitive The first optical glass (9) perpendicular to the outgoing light path of the laser (7) is provided below the device (8), and it is characterized in that between the above-mentioned first optical glass (9) and the right-angle prism (14) are arranged in sequence with the laser ( 7) the exit light path is the second optical glass (17) and the third optical glass (18) that form a group of prism models of acute angle α ₁ and obtuse angle β ₁ ; ) are successively provided with the fourth optical glass (19) and the fifth optical glass (20) that form a group of prism models at an acute angle α ₂ and an obtuse angle β ₂ with the opposite direction of the laser (7) exit light path; The first optical glass (9), the second optical glass (17), the fifth optical glass (20) and the housing (12) of the device are enclosed into a closed upper reference cavity (2) filled with reference liquid (10) , the fourth optical glass (19), the fifth optical glass (20) and the housing (12) at the bottom of the device are enclosed to form a closed lower reference that contains a rectangular prism (14) and is filled with reference liquid (10). Cavity (4); a protective net (13) fixed to the housing (12) is provided between the upper and lower reference cavities (2, 4). 2. The detection device according to claim 1, characterized in that a middle reference chamber (3) is also provided between the above-mentioned upper and lower reference chambers (2, 4), and the middle reference chamber (3) includes two pieces from the top And the sixth optical glass (21) and the seventh optical glass (22) that are in obtuse angle β ₁ and acute angle α ₁ with the exit light path of laser device (7) successively, and two pieces are successively connected with laser device (7) from bottom to top. The eighth optical glass (23) and the ninth optical glass (24) of which the opposite direction of the incident light path forms an obtuse angle β ₂ and an acute angle α ₂ ; the sixth to ninth optical glass (21-24) and the shell on the device side body (12) is enclosed into a closed cavity filled with reference liquid (10); and between the middle reference cavity (3) and the upper and lower reference cavities (2, 4) there are protective net (13). 3. The detection device according to claim 1 or 2, characterized in that said acute angle α ₁ or α ₂ is in the range of 20-70 degrees. 4. The detecting device according to claim 1 or 2, characterized in that said obtuse angle β ₁ or β ₂ is in the range of 110-160 degrees. 5. The detection device according to claim 1 or 2, characterized in that the above-mentioned acute angles α ₁ , α ₂ and obtuse angles β ₁ , β ₂ are 45 degrees and 135 degrees respectively, so that the two adjacent pieces of optical glass on the left and right are perpendicular to each other . 6. The detection device according to claim 1, characterized in that said first to fifth optical glasses (9, 17-20) are quartz glass. 7. The detection device according to claim 1 or 2, characterized in that the reference liquid (10) is distilled water. 8. The detection device according to claim 1 or 2, characterized in that the above-mentioned laser (7) is a semiconductor laser with an output wavelength of 650nm, an exit pupil power of 1mw, and a beam diameter of 1mm at 1m. 9. The detection device according to claim 1, characterized in that the above-mentioned position sensitive device (8) is a one-dimensional PSD of model S8543.

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