A compact photoelectric sand measuring instrument based on perpendicular incidence of refractive prism light and a measuring method

Abstract

The application discloses a compact photoelectric sand measuring instrument based on vertical incidence of refractive prism light and a measuring method. The sand measuring instrument comprises a collimated light source, a light path folding module, a photoelectric detection module and a data processing module. The collimated light is vertically incident to the refractive prism, is refracted by the inclined surface and is incident to water at an angle of 45 degrees after the protection glass, horizontal displacement of the light path is realized under limited vertical thickness, all photoelectric devices can be vertically arranged, and the instrument diameter is significantly reduced. The near-range and long-range detectors are vertically installed, the scattering light signals of the same angle but different path lengths are synchronously collected, the water body heterogeneity interference is eliminated, and high and low concentration tests are considered. The data processing module introduces a smoothing gating function and a logarithmic domain scale factor to perform weighted fusion on two signals, and the zero singularity of the logarithmic transformation is eliminated. The application has compact structure, small volume and good application prospect, and is suitable for use in occasions with strict requirements on instrument size.

Description

Technical Field

[0001] This invention belongs to the field of suspended sediment particle concentration detection technology, and in particular, it is a compact photoelectric sand measuring instrument and measurement method based on the perpendicular incidence of light from a refracting prism. Background Technology

[0002] Optical scattering is one of the most widely used methods in the field of suspended sediment concentration measurement. Its basic principle is as follows: a beam of collimated infrared light is shone into the water body through a protective glass. The suspended particles in the water body will scatter the incident light. The detector receives the scattered light signal at a specific angle and processes it to estimate the concentration of suspended particles.

[0003] In traditional designs, two typical backscattering angles are usually used for receiving the light: 90° and 135° backscattering angles. This combination can balance measurement accuracy under different concentration conditions. Although these two angle detection methods can reflect the concentration changes of particles in water to some extent, the measurement results are easily affected by the non-uniformity of particle distribution and density because the scattering points are not completely consistent. More importantly, this optical path arrangement requires a large amount of space.

[0004] To ensure effective detection of scattered light, traditional optical path designs typically require thicker protective glass or increased detector spacing. This layout directly leads to an increase in the overall instrument diameter, making it unsuitable for applications with stringent size and installation requirements. Therefore, existing suspended sediment concentration measuring instruments based on optical scattering methods suffer from significant limitations in terms of structural compactness and miniaturization, becoming a key issue restricting their widespread application. Achieving optical path optimization and instrument miniaturization within limited space conditions would not only improve the device's adaptability to complex aquatic environments but also expand its application scope in hydrological monitoring, water conservancy project management, and other fields. This would provide a more accurate, reliable, and efficient means of measuring sediment concentration for related scientific research and engineering practices, possessing significant engineering importance and practical application value. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a compact photoelectric sand measuring instrument. While ensuring the measurement performance of suspended sediment with high and low concentrations and large range, the instrument diameter is greatly reduced by optimizing the optical and spatial layout, thus achieving a highly integrated miniaturized design.

[0006] The technical solution to achieve the purpose of this invention is: a compact photoelectric sand measuring instrument based on the perpendicular incidence of light from a refracting prism, the sand measuring instrument comprising:

[0007] A collimating light source module is used to emit collimated light signals and incident perpendicularly along a first direction;

[0008] An optical path refraction module is installed on the propagation path of the collimated optical signal to change the direction of light propagation so that the light eventually enters the water body being measured at a preset incident angle.

[0009] The photoelectric detection module includes a first photoelectric detection unit and a second photoelectric detection unit that are independent of each other, and are used to collect backscattered light signals at different depths generated by suspended particles in the water body being tested.

[0010] The data processing module, electrically connected to the photoelectric detection module, is used to perform weighted fusion processing on the two collected scattered light signals to obtain the suspended particle concentration of the water body being tested.

[0011] Furthermore, the first direction is a vertical direction; after the optical path refraction module changes the light path, the light finally enters the water body being measured at an incident angle of 45°.

[0012] Furthermore, the collimating light source module includes an infrared laser light source for emitting infrared collimated laser signals.

[0013] Furthermore, the optical path refractive module includes a refractive prism and a protective glass arranged sequentially along the direction of light propagation;

[0014] The collimated light signal is incident perpendicularly onto the refracting prism, and after being refracted by the inclined surface of the refracting prism, it exits through its bottom and enters the protective glass.

[0015] After passing through the protective glass, the light undergoes a horizontal displacement within the glass and ultimately enters the water body being measured at the preset incident angle.

[0016] Furthermore, the refracting prism has a cylindrical structure with a flat bottom surface and a pre-set oblique angle between the upper side surface and the bottom surface; the refracting prism is made of optical glass with a high refractive index and has a bottom diameter of 8mm.

[0017] Furthermore, the protective glass is a circular glass sheet made of K9 optical glass; the thickness of the protective glass is 8.5mm, and the light refraction angle within the protective glass is 39°.

[0018] Furthermore, the first photoelectric detection unit is a short-range photoelectric detector, which is vertically arranged inside the protective glass; the central vertical line of the short-range photoelectric detector intersects with the light-emitting surface of the light emitted from the bottom of the refracting prism, so as to receive the backscattered light signal of high-concentration suspended sediment; wherein, the standard of high concentration is set according to actual needs.

[0019] The second photoelectric detection unit is a remote photoelectric detector, which is set on the outside of the protective glass and at a preset distance from the protective glass. It is used to receive backscattered light signals from low-concentration suspended sediment. The standard for low concentration is set according to actual needs.

[0020] The scattered light signals collected by the first photoelectric detection unit and the second photoelectric detection unit are both 135° backscattered light signals.

[0021] Furthermore, the placement edge of the near-range photodetector is 1 mm away from the edge of the refractive prism, and the center-to-center distance between the two is at least 7 mm; the horizontal displacement of the light within the protective glass is 7 mm.

[0022] Furthermore, the data processing module performs weighted fusion processing on the two acquired scattered light signals, specifically including:

[0023] Acquire the first scattered light signal collected by the first photoelectric detection unit and the second scattered light signal collected by the second photoelectric detection unit ;

[0024] Introducing the first scattered light signal Smooth gated function for input :

[0025]

[0026] In the formula, As the gate control center, For the width of the transition zone, yes It is a strictly monotonic function with a range of values ​​(0,1).

[0027] Construct peak locking proxy item Using the smoothing gate function For the second scattered light signal Make corrections:

[0028]

[0029] In the formula, To calibrate the peak value, This indicates a peak-locked proxy, denoted as ;

[0030] By adjusting the number field scaling factor and weighting coefficients The final fused observations are calculated and output. :

[0031]

[0032] In the formula, >0 represents the weight of the proxy term of the second photoelectric detection unit. >0 represents the logarithmic scaling factor.

[0033] On the other hand, a measurement method for the aforementioned compact photoelectric sand measuring instrument is provided, the measurement method comprising the following steps:

[0034] Step 1: Use the collimated light source module to emit an infrared collimated laser and incident it onto the refractive prism in a vertical direction;

[0035] Step 2: After the incident light is refracted on the inclined surface of the refracting prism, it exits from the center of the bottom of the prism and then enters the circular protective glass. The angle of refraction of the light inside the circular protective glass is 39°, and it finally enters the water body being tested at an incident angle of 45°.

[0036] Step 3: The first photodetector and the second photodetector are used to receive 135° backscattered light signals at different depths in the water, respectively, wherein the first photodetector outputs a near-field detection signal. The second photodetector outputs a far-field detection signal. ;

[0037] Step 4: The data processing module uses a weighted fusion algorithm to process the near-field detection signal. and far-field detection signals The mixture is then processed to output the concentration of suspended particles in the measured water body.

[0038] Compared with the prior art, the significant advantages of this invention are:

[0039] (1) By introducing a refracting prism in the incident light path, the light source and all photoelectric detection elements can be arranged vertically and flatly. The detection base does not need to be processed with complex oblique holes, which fundamentally reduces the size of the instrument in the diameter direction. It is very suitable for operation in complex underwater working conditions with strict requirements for volume and installation space.

[0040] (2) The present invention innovatively designs both the near-range and long-range photodetectors to receive 135° backscattered light signals. Compared with the drawbacks of traditional designs that use different angles (such as 90° and 135°) resulting in inconsistent spatial positions of scattering points and susceptibility to interference from uneven distribution of mud and sand, this design only changes the spatial path length, perfectly eliminating the measurement error caused by the non-uniform spatial distribution of particles.

[0041] (3) By using reasonable geometric optical path refraction, and with two sets of detectors set at the near and a certain distance of the protective glass respectively, backscattered light signals at different positions can be collected simultaneously. The near-field detector is for high concentration monitoring (short optical path, weak self-absorption), and the far-field detector is for low concentration testing (long optical path, capturing weak scattering). Thus, the measurement needs under different concentration conditions are taken into account within a very small diameter range, and the concentration measurement range is significantly expanded.

[0042] (4) The data processing module introduces a smoothing gating function with near-field signals as input, realizing smooth monotonic fusion of the two signals across several orders of magnitude amplitude, effectively locking the far-field peak decline under high concentration. Simultaneously, the algorithm employs... Instead of directly taking the logarithm, it maintains a linear approximation in the small signal range, completely avoiding the singularity problem of negative infinity that occurs when the traditional logarithmic transform approaches zero, and greatly improving the accuracy of the data and the reliability of the system operation.

[0043] (5) The present invention has a compact structure and the measurement modules work together. It can operate stably under conditions such as limited installation space and complex water environment, and has strong engineering adaptability.

[0044] (6) The present invention has a compact overall design, high integration, and is easy to operate. Its measurement accuracy and data reliability are superior to those of traditional optical scattering sand measuring instruments, and it has good engineering application value and industrialization prospects.

[0045] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0046] Figure 1 One embodiment is a compact photoelectric sand measuring instrument based on the perpendicular incidence of light through a refracting prism.

[0047] Figure 2 This is a response curve of the far-field detector in one embodiment. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0049] It should be noted that if the embodiments of the present invention involve descriptions such as "first" and "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0050] In one embodiment, combined Figure 1 A compact photoelectric sand measuring instrument based on perpendicular incident light from a refracting prism is provided, the sand measuring instrument comprising:

[0051] A collimating light source module is used to emit collimated light signals and incident perpendicularly along a first direction;

[0052] An optical path refraction module is installed on the propagation path of the collimated optical signal to change the direction of light propagation so that the light eventually enters the water body being measured at a preset incident angle.

[0053] The photoelectric detection module includes a first photoelectric detection unit and a second photoelectric detection unit that are independent of each other, and are used to collect backscattered light signals at different depths generated by suspended particles in the water body being tested.

[0054] The data processing module, electrically connected to the photoelectric detection module, is used to perform weighted fusion processing on the two collected scattered light signals to obtain the suspended particle concentration of the water body being tested.

[0055] Furthermore, in one embodiment, the first direction is a vertical direction; after the optical path refraction module changes the light path, the light finally enters the water body being measured at an incident angle of 45°.

[0056] Here, using vertical incident light is the primary prerequisite for achieving lateral space compression within the instrument. Traditional designs often tilt the light source to allow it to enter the water at an angle, resulting in significant spatial redundancy in the instrument's diameter direction.

[0057] Preferably, in some embodiments, the collimating light source module includes an infrared laser light source for emitting infrared collimated laser signals.

[0058] Here, the light source is not limited to infrared lasers (such as 850nm / 940nm LDs). In water monitoring with certain turbidity or specific characteristic particle size, it can be replaced by visible light collimated lasers (such as blue light 450nm, green light 532nm) or high-brightness LED light sources equipped with collimating lens groups.

[0059] Furthermore, in one embodiment, the optical path refractive module includes a refractive prism and a protective glass arranged sequentially along the direction of light propagation;

[0060] The collimated light signal is incident perpendicularly onto the refracting prism, and after being refracted by the inclined surface of the refracting prism, it exits through its bottom and enters the protective glass.

[0061] After passing through the protective glass, the light undergoes a horizontal displacement within the glass and ultimately enters the water body being measured at the preset incident angle.

[0062] Preferably, in some embodiments, the refractive prism has a cylindrical structure with a flat bottom surface and a predetermined oblique angle between the upper side surface and the bottom surface; the refractive prism is made of optical glass with a high refractive index and has a bottom diameter of 8 mm.

[0063] Here, compared to the lateral widening of conventional direct oblique incidence, the 8mm bottom base greatly reduces the instrument diameter occupied by the transmitter.

[0064] Preferably, in some embodiments, the protective glass is a circular glass sheet made of K9 optical glass; the thickness of the protective glass is 8.5 mm, and the light refraction angle within the protective glass is 39°.

[0065] Here, the light path undergoes a first refraction: after the collimated light ray enters the refracting prism in a vertical direction, it undergoes a first refraction on its inclined surface. The refracted light ray exits from the bottom center point of the prism and directly enters the protective glass that is tightly attached below.

[0066] Secondary refraction of light path and entry into water: The protective glass is made of K9 optical glass with a high hardness coefficient and excellent chemical stability. The refraction angle of light inside the protective glass is controlled at 39°. After exiting through the bottom surface of the glass, due to the change in the refractive index of the water, the light finally enters the water at a precise angle of 45°.

[0067] Here, the light ultimately enters the water at a 45° angle, which aligns with the golden geometric angle for the vertically mounted detector above to receive the classic 135° backscattered light. Through the chain of "vertical incidence → prism bevel refraction → protective glass refraction at a 45° exit," the unity of optical angle transformation and spatial compression is achieved.

[0068] Furthermore, in one embodiment, the first photoelectric detection unit is a short-range photoelectric detector, which is vertically disposed inside the protective glass; the central vertical line of the short-range photoelectric detector intersects with the light-emitting surface of the light emitted from the bottom of the refracting prism, so as to receive the backscattered light signal of high-concentration suspended sediment; wherein, the standard of high concentration is set according to actual needs.

[0069] The second photoelectric detection unit is a remote photoelectric detector, which is set on the outside of the protective glass and at a preset distance from the protective glass. It is used to receive backscattered light signals from low-concentration suspended sediment. The standard for low concentration is set according to actual needs.

[0070] The scattered light signals collected by the first photoelectric detection unit and the second photoelectric detection unit are both 135° backscattered light signals.

[0071] Here, the response curve of the far-field photodetector is as follows: Figure 2 As shown by curve ① in the diagram. The near field is generally as follows: Figure 2 As shown in curve ②, the shape of curve ② is related to the placement of the near-field detector, and it may also be the same as the shape of curve ①. In this design, the near-field detector is placed near the light-emitting surface. Due to its proximity to the light-emitting port, the scattering path is extremely short, and the problem of severe light intensity attenuation under high concentration is effectively suppressed. Its response curve shows a monotonically increasing shape with concentration.

[0072] Preferably, in some embodiments, the photodetector is not limited to a PIN photodiode. To obtain higher sensitivity in the far field, the FD detector can be equivalently replaced by an avalanche photodiode (APD) or a silicon photomultiplier tube (SiPM). Furthermore, the number of detectors is not limited to two sets; a third and fourth detector can be redundantly configured along the linear axis to form a multi-point long-range array, enabling more refined segmented inversion.

[0073] Preferably, in some embodiments, the placement edge of the near-field photodetector is 1 mm away from the edge of the refractive prism, and the center-to-center distance between the two is at least 7 mm; the horizontal displacement of the light within the protective glass is 7 mm.

[0074] Here, to effectively measure high concentrations of suspended sediment, the first set of photodetectors (near-range photodetectors, or NDs) is placed vertically inside the protective glass. To ensure that the central perpendicular line of the ND roughly intersects the light-emitting surface of the incident light on the bottom of the protective glass, and to simultaneously meet the mechanical wall thickness requirements for structural processing and packaging, a 1mm assembly gap is left between the mechanical edge of the ND and the mechanical edge of the refractive prism. Since the bottom radius of the prism is 4mm, the distance between the central axis of the prism and the central perpendicular line of the ND is at least 7mm.

[0075] Based on the aforementioned spatial avoidance constraints, to ensure that the light rays emanating from the bottom center of the prism, after undergoing lateral translation through the protective glass, fall precisely on the vertical line directly opposite the ND center, the light rays must achieve a horizontal displacement of 7mm within the protective glass. Based on trigonometric geometric relationships, the theoretical formula for calculating the thickness d of the protective glass is:

[0076]

[0077] It should be noted that, in addition to K9 glass, the circular protective glass can be equivalently replaced with sapphire glass in extremely harsh environments with high friction and severe sand and gravel erosion (such as the high-velocity Yellow River dam mouth). Since the refractive index of sapphire glass is higher than that of K9 glass, its internal refraction angle will be less than 39°. In this case, those skilled in the art can recalculate the thickness d according to the above formula, thus achieving the lateral translation objective of this invention.

[0078] Furthermore, in one embodiment, the data processing module performs weighted fusion processing on the two acquired scattered light signals, specifically including:

[0079] Acquire the first scattered light signal collected by the first photoelectric detection unit and the second scattered light signal collected by the second photoelectric detection unit ;

[0080] Introducing the first scattered light signal Smooth gated function for input :

[0081]

[0082] In the formula, As the gate control center, For the width of the transition zone, yes It is a strictly monotonic function with a range of (0,1); when the water concentration is low... Smaller →0, the fused quantity is mainly output to far-field detection, that is Figure 2 Curve ① in the figure; when the concentration is high, →1, Fusion amount shifts to peak locking agent, i.e., high concentration agent control;

[0083] Construct peak locking proxy item Using the smoothing gate function For the second scattered light signal Make corrections:

[0084]

[0085] In the formula, To calibrate the peak value, Indicates peak-locked proxy;

[0086] By adjusting the number field scaling factor and weighting coefficients The final fused observations are calculated and output. :

[0087]

[0088] In the formula, >0 represents the weight of the proxy term of the second photoelectric detection unit. >0 represents the logarithmic scaling factor.

[0089] Here, the algorithm does not use segmented truncation splicing, but instead employs Sigmoid-based gated fusion. More importantly, the formula uses... Instead of directly taking lnx, a modified architecture is used. This successfully compresses the amplitude, which spans several orders of magnitude and is prone to numerical overflow or truncation errors, into a well-conditional dynamic range. On the other hand, it maintains a linear approximation of the original amplitude in the small signal (low concentration) range, completely avoiding the negative infinity singularity crash problem that is prone to occur when the signal is close to zero in traditional logarithmic transform.

[0090] In one embodiment, a measurement method for the compact photoelectric sand analyzer is provided, the measurement method comprising the following steps:

[0091] Step 1: Use the collimated light source module to emit an infrared collimated laser and incident it onto the refractive prism in a vertical direction;

[0092] Step 2: After the incident light is refracted on the inclined surface of the refracting prism, it exits from the center of the bottom of the prism and then enters the circular protective glass. The angle of refraction of the light inside the circular protective glass is 39°, and it finally enters the water body being tested at an incident angle of 45°.

[0093] Step 3: The first photodetector and the second photodetector are used to receive 135° backscattered light signals at different depths in the water, respectively, wherein the first photodetector outputs a near-field detection signal. The second photodetector outputs a far-field detection signal. ;

[0094] Step 4: The data processing module uses a weighted fusion algorithm to process the near-field detection signal. and far-field detection signals The mixture is then processed to output the concentration of suspended particles in the measured water body.

[0095] In one embodiment, a compact photoelectric sand measurement system based on perpendicular incident light from a refracting prism is provided, the system comprising:

[0096] The first module is used to: emit an infrared collimated laser and incident it perpendicularly onto the refractive prism;

[0097] The second module is used to achieve the following: after the incident light is refracted on the inclined surface of the refracting prism, it exits from the center of the bottom of the prism and then enters the circular protective glass. The angle of refraction of the light in the circular protective glass is 39°, and it finally enters the water body being measured at an incident angle of 45°.

[0098] The third module is used to: receive 135° backscattered light signals at different depths in the water using a first photodetector and a second photodetector, respectively, wherein the first photodetector outputs a near-field detection signal. The second photodetector outputs a far-field detection signal. ;

[0099] The fourth module is used to implement: using a weighted fusion algorithm to process the near-field detection signal. and far-field detection signals The mixture is then processed to output the concentration of suspended particles in the measured water body.

[0100] Specific limitations regarding the compact photoelectric sand measurement system based on the perpendicular incidence of light from a refracting prism can be found in the limitations of the measurement method above, and will not be repeated here. Each module in the aforementioned compact photoelectric sand measurement system based on the perpendicular incidence of light from a refracting prism can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the corresponding operations of each module.

[0101] This invention enables large-range suspended sediment concentration testing within a limited diameter range. It features a compact structure and small size, making it suitable for use in applications with strict requirements on instrument size, and has promising application prospects.

[0102] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention without departing from its spirit and scope should be included within the protection scope of the present invention.

Claims

1. A compact photoelectric sand measuring instrument based on perpendicular incidence of light through a refracting prism, characterized in that, The sand measuring instrument includes: A collimating light source module is used to emit collimated light signals and incident perpendicularly along a first direction; An optical path refraction module is installed on the propagation path of the collimated optical signal to change the direction of light propagation so that the light eventually enters the water body being measured at a preset incident angle. The photoelectric detection module includes a first photoelectric detection unit and a second photoelectric detection unit that are independent of each other, and are used to collect backscattered light signals at different depths generated by suspended particles in the water body being tested. The data processing module, electrically connected to the photoelectric detection module, is used to perform weighted fusion processing on the two collected scattered light signals to obtain the suspended particle concentration of the water body being tested.

2. The compact photoelectric sand measuring instrument based on perpendicular incident light from a refracting prism according to claim 1, characterized in that, The first direction is the vertical direction; after the optical path refraction module changes the light path, the light finally enters the water body being measured at an incident angle of 45°.

3. The compact photoelectric sand measuring instrument based on perpendicular incident light from a refracting prism according to claim 1, characterized in that, The collimated light source module includes an infrared laser light source for emitting infrared collimated laser signals.

4. The compact photoelectric sand measuring instrument based on perpendicular incident light from a refracting prism according to claim 1, characterized in that, The optical path refractive module includes a refractive prism and a protective glass arranged sequentially along the direction of light propagation; The collimated light signal is incident perpendicularly onto the refracting prism, and after being refracted by the inclined surface of the refracting prism, it exits through its bottom and enters the protective glass. After passing through the protective glass, the light undergoes a horizontal displacement within the glass and ultimately enters the water body being measured at the preset incident angle.

5. The compact photoelectric sand measuring instrument based on perpendicular incident light from a refracting prism according to claim 4, characterized in that, The refracting prism has a cylindrical structure with a flat bottom surface and a pre-set angle between the top surface and the bottom surface. The refracting prism is made of optical glass with a high refractive index and has a bottom diameter of 8 mm.

6. The compact photoelectric sand measuring instrument based on perpendicular incident light from a refracting prism according to claim 4, characterized in that, The protective glass is a circular glass sheet made of K9 optical glass; the thickness of the protective glass is 8.5mm, and the light refraction angle within the protective glass is 39°.

7. The compact photoelectric sand measuring instrument based on perpendicular incident light from a refracting prism according to claim 4, characterized in that, The first photoelectric detection unit is a short-range photoelectric detector, which is vertically installed inside the protective glass. The central vertical line of the short-range photoelectric detector intersects with the light-emitting surface of the light emitted from the bottom of the refracting prism to receive the backscattered light signal of high-concentration suspended sediment. The standard for high concentration is set according to actual needs. The second photoelectric detection unit is a remote photoelectric detector, which is set on the outside of the protective glass and at a preset distance from the protective glass. It is used to receive backscattered light signals from low-concentration suspended sediment. The standard for low concentration is set according to actual needs. The scattered light signals collected by the first photoelectric detection unit and the second photoelectric detection unit are both 135° backscattered light signals.

8. The compact photoelectric sand measuring instrument based on perpendicular incident light from a refracting prism according to claim 7, characterized in that, The placement edge of the near-range photodetector is 1 mm away from the edge of the refractive prism, and the center-to-center distance between the two is at least 7 mm; the horizontal displacement of the light within the protective glass is 7 mm.

9. The compact photoelectric sand measuring instrument based on perpendicular incident light from a refracting prism according to claim 1, characterized in that, The data processing module performs weighted fusion processing on the two acquired scattered light signals, specifically including: Acquire the first scattered light signal collected by the first photoelectric detection unit and the second scattered light signal collected by the second photoelectric detection unit ; Introducing the first scattered light signal Smooth gated function for input : ； In the formula, As the gate control center, For the width of the transition zone, yes It is a strictly monotonic function with a range of values ​​(0,1). Construct peak locking proxy item Using the smoothing gate function For the second scattered light signal Make corrections: ； In the formula, To calibrate the peak value, This indicates a peak-locked proxy, denoted as ; By adjusting the number field scaling factor and weighting coefficients The final fused observations are calculated and output. : ； In the formula, >0 represents the weight of the proxy term of the second photoelectric detection unit. >0 represents the logarithmic scaling factor.

10. A measurement method for a compact photoelectric sand measuring instrument, characterized in that, The measurement method is implemented based on the compact photoelectric sand measuring instrument according to any one of claims 1 to 9, and the measurement method includes the following steps: Step 1: Use the collimated light source module to emit an infrared collimated laser and incident it onto the refractive prism in a vertical direction; Step 2: After the incident light is refracted on the inclined surface of the refracting prism, it exits from the center of the bottom of the prism and then enters the circular protective glass. The angle of refraction of the light inside the circular protective glass is 39°, and it finally enters the water body being tested at an incident angle of 45°. Step 3: The first photodetector and the second photodetector are used to receive 135° backscattered light signals at different depths in the water, respectively, wherein the first photodetector outputs a near-field detection signal. The second photodetector outputs a far-field detection signal. ; Step 4: The data processing module uses a weighted fusion algorithm to process the near-field detection signal. and far-field detection signals The mixture is then processed to output the concentration of suspended particles in the measured water body.

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