Water turbidity detection sensor with laser beam expanding assembly

Abstract

The utility model discloses a water turbidity detection sensor with a laser beam expanding assembly. The water turbidity detection sensor comprises an emergent part and a receiving part which are immersed in water, the optical axis of the receiving component is vertical to that of the emitting component; the emergent part comprises a laser light source, a beam expanding lens and an emergent assembly; the output end of the laser light source is sequentially provided with a beam expanding lens and an emergent assembly, the laser light source emits emergent laser, the emergent laser is expanded by the beam expanding lens to form beam expanding laser, the beam expanding laser penetrates through the emergent assembly to form detection laser and is vertically emitted to the water body, and the optical axis of the beam expanding lens is located on the optical axis of the emergent laser; the receiving part comprises a receiver, a receiving lens and a receiving assembly; the optical axis of the receiving lens is perpendicular to the optical axis of the detection laser. The scattered light sequentially passes through the receiving assembly and the receiving lens and then enters the receiver. According to the utility model, the sensitivity of the turbidity meter can be improved, the anti-interference capability is improved, and the measurement precision is ensured.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of sensor, concretely relates to a water quality turbidity detection sensor with laser beam expanding assembly. BACKGROUND

[0002] Water quality turbidity detection is based on the principle of scattered light, if using laser light source to measure water quality turbidity, the particulate matter in water will emit scattered light to all directions when encountering laser beam. There are extreme values in the 45-degree, 90-degree and 135-degree directions with the light beam. The intensity of scattered light is proportional to the concentration of particulate matter. Because the laser beam has very good directivity, unlike other point light sources, the light energy decays with the square of the transmission distance, and in a transparent medium, the energy of the laser beam will not change with the distance during transmission, which brings great convenience to improve the detection sensitivity.

[0003] But because of the bubbles in the water, once the bubbles enter the measurement light path, they will change the transmission characteristics of the laser beam like a micro-lens, which will bring optical interference to the measurement, such as changing the transmission path of part of the light beam, and producing a lot of stray light, resulting in a large measurement error. Unlike other light sources with larger beam angles, a small amount of bubbles in the light path has less impact on the measurement compared to more particulate matter. But the energy of the wide beam light source is not concentrated, and the energy decays with the square of the distance, so the scattered light produced by the particulate matter is weak, and the wide beam is also easy to produce more stray light in the measurement water tank, so the measurement sensitivity is low, and it is difficult to measure the turbidity below 0.1 NTU. Therefore, it is necessary to improve the current laser water quality turbidity detection technology. CONTENT OF THE UTILITY MODEL

[0004] In view of the deficiencies in the prior art, the utility model provides a water quality turbidity detection sensor with a laser beam expanding assembly. The utility model can improve the sensitivity of the turbidimeter while improving the anti-interference ability and ensuring the measurement accuracy.

[0005] The technical scheme adopted by the utility model is:

[0006] The water quality turbidity detection sensor is immersed in the water body, comprising a shell and an exit component and a receiving component arranged inside the shell; the exit component vertically emits detection laser to the water body, and the detection laser forms scattered light after being scattered by the particulate matter in the water body, the receiving component is arranged on one side of the front end of the exit component in the propagation direction of the detection laser, the optical axis of the receiving component is perpendicular to the optical axis of the detection laser, the receiving component receives the scattered light, and the received scattered light is perpendicular to the propagation direction of the detection laser.

[0007] The exit component comprises a laser light source, a beam expander and an exit assembly; the output end of the laser light source is sequentially arranged with the beam expander and the exit assembly, the laser light source emits exit laser, the exit laser is expanded by the beam expander to form expanded laser, the expanded laser passes through the exit assembly to form detection laser and is vertically emitted to the water body, and the optical axis of the beam expander is located on the optical axis of the exit laser.

[0008] The receiving component comprises a receiver, a receiving lens and a receiving assembly; the optical axis of the receiving lens is perpendicular to the propagation direction of the detection laser, and the scattered light enters the receiver after sequentially passing through the receiving assembly and the receiving lens.

[0009] The beam expander adopts a double-convex or flat-convex converging lens; the optical axis of the beam expander coincides with the optical axis of the exit laser, the exit laser fine beam is converged by the beam expander to exit at the focal point of the beam expander to form an expanded laser beam with a certain beam angle, the farther from the focal point, the larger the laser spot of the expanded laser; the beam angle of the expanded laser can be changed by changing the focal length of the beam expander: the shorter the focal length, the larger the beam angle, and the more obvious the beam expanding effect, thereby reducing the influence of small bubbles in the optical path on the measurement result.

[0010] The beam expander preferably adopts a flat-convex converging lens, the optical axis of the flat-convex converging lens coincides with the beam exit optical axis of the laser light source, and the flat side of the flat-convex converging lens is arranged in close contact with the light exit surface of the laser light source.

[0011] The exit assembly comprises an aperture diaphragm, an exit sealing ring, an exit plane mirror and an exit compression ring arranged in sequence in the propagation direction of the expanded laser; the exit compression ring is mounted on the housing, the exit plane mirror is embedded on the exit compression ring, and the exit plane mirror is sealingly connected to the housing through the exit sealing ring. The aperture diaphragm is mounted on the output end of the beam expander.

[0012] The exit sealing ring, the exit plane mirror and the exit compression ring are coaxially arranged and are arranged obliquely relative to the optical axis of the exit laser. Preferably, the angle between the common axis of the exit sealing ring, the exit plane mirror and the exit compression ring and the optical axis of the exit laser is 45 degrees.

[0013] The housing is divided into an exit part containing the exit component and a receiving part containing the receiving component; the exit part and the receiving part are connected through a rigid waterproof part, the rigid waterproof part contains an electric wire, the exit component is electrically connected to the receiving component through the electric wire; the exit part is provided with a waterproof joint, and the water quality turbidity detection sensor is connected to the external power supply and the communication terminal of the single-chip microcomputer through the waterproof joint. The front end surface of the exit part is arranged obliquely relative to the optical axis of the exit laser, and the exit sealing ring, the exit plane mirror and the exit compression ring are mounted on the front end surface of the exit part. Preferably, the angle between the front end surface of the exit part and the optical axis of the exit laser is 45 degrees.

[0014] The receiving component comprises a receiving lens, a receiving sealing ring and a receiving plane mirror arranged in sequence in the propagation direction of the received scattered light, and the receiving lens is a convex lens.

[0015] The exit component further comprises a driving circuit board, and the driving circuit board is provided with a constant current pulse modulation circuit, an optoelectronic signal conversion circuit, an amplification circuit and a single-chip microcomputer; the input end of the laser light source is electrically connected with the current output end of the constant current pulse modulation circuit, the reference output end of the laser light source is electrically connected with the optical signal input end of the optoelectronic signal conversion circuit, the electrical signal output end of the optoelectronic signal conversion circuit is electrically connected with the input end of the amplification circuit, the output end of the amplification circuit is electrically connected with the signal reference end of the constant current pulse modulation circuit, and the modulation end of the constant current pulse modulation circuit is electrically connected with the output end of the single-chip microcomputer.

[0016] The receiving component comprises a signal processing circuit board, and the signal processing circuit board is provided with an optoelectronic conversion circuit, a signal filtering and amplification circuit, an analog-to-digital conversion circuit and a communication circuit; the output end of the receiver is electrically connected with the optical signal input end of the optoelectronic conversion circuit, the electrical signal output end of the optoelectronic conversion circuit is electrically connected with the input end of the signal filtering and amplification circuit, the output end of the signal filtering and amplification circuit is electrically connected with the input end of the analog-to-digital conversion circuit, the output end of the analog-to-digital conversion circuit is electrically connected with the input end of the communication circuit, and the output end of the communication circuit is electrically connected with the terminal of the outside.

[0017] The utility model discloses a beneficial effect is:

[0018] The utility model discloses can improve turbidity appearance sensitivity's while, reduce the influence of small bubble in optical path, improve anti -interference ability, guarantee measurement accuracy. Utilize such optical path, can measure 0.001NTU's turbidity. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is the structure diagram of water quality turbidity detection sensor in the utility model.

[0020] In the drawing: 1, waterproof joint, 2, shell, 3, driving circuit board, 4, laser light source, 5, beam expander lens, 6, aperture diaphragm, 7, exit sealing ring, 8, exit plane mirror, 9, exit compression ring, 10, electric wire, 11, signal processing circuit board, 12, receiver, 13, receiving lens, 14, receiving sealing ring, 15, receiving plane mirror, 16, receiving compression ring. DETAILED DESCRIPTION

[0021] The utility model will be further explained in detail in combination with the drawings and specific embodiment.

[0022] The utility model provides a water quality turbidity detection sensor with laser beam expanding assembly, can measure 0.001NTU turbidity.

[0023] Laser beam has good directionality and concentrated energy, and the scattered light intensity is large when laser beam is incident to water body and meets the particulate matter in water, which can improve the sensitivity of turbidity measurement. However, due to the existence of small bubbles in water, the small bubbles are like a small lens, and the small laser beam will change greatly when meeting the small bubble beam, which not only changes the propagation path of the beam and affects the energy of the laser beam, but also produces a large amount of stray light, which will greatly affect the turbidity measurement and make the measurement result distorted. The laser beam can be considered as a parallel light with a small diameter, and the small parallel laser is changed into a laser with a certain beam angle by using the converging effect of the lens, the beam structure of the laser is changed, the beam is expanded, the energy of the laser beam is too concentrated, but the energy of the outgoing light is not changed. While improving the sensitivity of the turbidimeter, the influence of small bubbles in the optical path is reduced, the anti-interference ability is improved, and the measurement accuracy is ensured. By using such an optical path, the turbidity of 0.001NTU can be measured.

[0024] As shown in Figure 1 The water quality turbidity detection sensor in the utility model is immersed in water body, and includes an outer shell 2 and an outgoing component and a receiving component arranged inside the outer shell 2. The outgoing component vertically emits detection laser to the water body, the detection laser is scattered by the particulate matter in the water body to form scattered light, the receiving component is arranged in front of the outgoing component in the propagation direction of the detection laser, and is used for receiving scattered light in one of the propagation directions, and the received scattered light is perpendicular to the propagation direction (optical axis) of the detection laser.

[0025] The outgoing component includes a laser light source 4, a beam expanding lens 5 and an outgoing assembly. The laser light source 4 is used for emitting outgoing laser, the beam expanding lens 5 is used for expanding the parallel laser beam into a wide beam (the expanded beam laser with a certain beam angle), and the outgoing assembly is used for limiting the stray light generated by the expansion. The output end of the laser light source 4 is sequentially arranged with the beam expanding lens 5 and the outgoing assembly, the laser light source 4 emits outgoing laser, the outgoing laser is expanded into expanded laser by the beam expanding lens 5, the expanded laser passes through the outgoing assembly to form detection laser and is vertically emitted to the water body, the optical axis of the outgoing laser and the detection laser is perpendicular to the horizontal plane, and the optical axis of the beam expanding lens 5 is located on the optical axis of the outgoing laser.

[0026] Preferably, the laser light source 4 emits red and near-infrared laser with wavelength less than 900nm.

[0027] Further, the exit component is mainly composed of an aperture diaphragm 6, an exit sealing ring 7, an exit plane mirror 8 and an exit compression ring 9 arranged in sequence in the propagation direction of the expanded laser. The exit plane mirror 8 is sealedly mounted on the shell through the exit sealing ring 7 and the exit compression ring 9 to prevent water from entering the inside of the shell 2. The exit compression ring 9 is mounted on the shell 2, and the exit plane mirror 8 is embedded on the exit compression ring 9. The exit plane mirror 8 is sealedly connected with the shell 2 through the exit sealing ring 7 to prevent water from entering the inside of the sensor. The expanded laser exits into the water body through the aperture diaphragm 6 and the exit plane mirror 8, and forms scattered light after being scattered by particles in the water.

[0028] Further, the exit optical axis is perpendicular to the horizontal plane, and the exit plane mirror 8 forms a 45-degree angle with the exit optical axis to prevent bubbles in the water from adhering to the glass surface and affecting the measurement.

[0029] Further, the expansion lens 5 can adopt a biconvex or plano-convex converging lens. The optical axis of the expansion lens 5 coincides with the optical axis of the exit laser, and the fine beam of the exit laser converges at the focal point of the expansion lens 5 to form an expanded laser beam with a certain beam angle. The farther away from the focal point of the expansion lens 5, the larger the laser spot of the expanded laser. In a specific implementation, the focal length of the expansion lens 5 can be changed to change the beam angle of the expanded laser: the shorter the focal length, the larger the beam angle, and the more obvious the expansion effect, thereby reducing the influence of small bubbles in the optical path on the measurement result.

[0030] Preferably, the expansion lens 5 adopts a plano-convex converging lens, the optical axis of the plano-convex converging lens coincides with the beam exit optical axis of the laser light source, and the plane side of the plano-convex converging lens is arranged in close contact with the light exit surface of the laser light source 4

[0031] Further, the parallel light of the laser converges at the focal point of the expansion lens 5 to exit as a light beam with a certain angle, and the beam diameter of the expanded laser increases with the increase of the distance from the focal point, thereby realizing the expansion of the laser beam.

[0032] At a position away from the focal point of the expansion lens 5 by a certain distance, the spot diameter of the expanded laser is:

[0033] d0=xtanφ

[0034] In the formula, d0 is the spot diameter of the expanded laser at a position away from the focal point of the expansion lens 5 by a certain distance, x is the distance between the position and the focal point of the expansion lens 5, and tanφ is the beam solid angle;

[0035] In the formula, d is the diameter of the exit laser, and f is the focal length of the lens.

[0036] tanφ=d / f

[0037] In the formula, d is the diameter of the exit laser, and f is the focal length of the lens.

[0038] As an optional embodiment of the utility model, the focal length f of the lens is 15mm, the d diameter of the laser spot is 2mm, the laser beam divergence angle tanφ=(2 / 15) after the laser beam passes through the plano-convex lens, at the distance of the plano-convex lens focal point x=75mm, the diameter d0 of the laser spot is 10mm.

[0039] In the embodiment, the receiving assembly is placed at the distance of 75mm from the plano-convex lens focal point.

[0040] The receiving component includes a receiver 12, a receiving lens 13 and a receiving assembly. The optical axis of the receiving lens 13 is arranged perpendicularly intersecting the optical axis (i.e. the propagation direction) of the detection laser. A bundle of scattered light perpendicular to the optical axis of the detection laser passes through the receiving assembly to remove stray light, and then is imaged to the receiver 12 through the receiving lens 13. After photoelectric signal processing, the turbidity measurement result is output to the outside terminal in the 485 communication mode. In the embodiment, the spot diameter at the intersection point can be determined according to the distance from the intersection point to the plano-convex transmission focal point. The receiving angle of the receiving assembly can be determined according to the size of the laser spot.

[0041] Further, the receiving assembly mainly consists of the receiving lens 13, the receiving sealing ring 14 and the receiving plane mirror 15 arranged in sequence in the propagation direction of the scattered light. The receiving lens 13 is a convex lens, and the optical axis of the receiving lens 13 is perpendicular to the outgoing optical axis.

[0042] Further, the exit component further comprises a driving circuit board 3, and the driving circuit board 3 is provided with a constant current pulse modulation circuit, an optoelectronic signal conversion circuit, an amplification circuit and a single-chip microcomputer. The laser light source 4 is provided with a reference output, the pins of the laser light source 4 are mounted on the driving circuit board 3, the driving circuit of the laser light source 4 is the constant current pulse modulation circuit, the reference output pin of the laser light source 4 is connected to the optoelectronic signal conversion circuit, the reference optoelectronic signal is amplified and then connected to the signal reference end of the constant current pulse modulation circuit to correct the laser constant current driving current and ensure the constant of the output light intensity of the laser light source. The pulse frequency of the modulation signal is controlled by the single-chip microcomputer. The input end of the laser light source 4 is electrically connected to the current output end of the constant current pulse modulation circuit, and the constant current pulse modulation circuit supplies power to the laser light source 4. The reference output end of the laser light source 4 is connected to the optoelectronic signal conversion circuit through the electrical connection with the light signal input end of the optoelectronic signal conversion circuit, the electrical signal output end of the optoelectronic signal conversion circuit is electrically connected to the input end of the amplification circuit, and the output end of the amplification circuit is electrically connected to the signal reference end of the constant current pulse modulation circuit. Specifically, the laser light source 4 inputs the reference light signal to the optoelectronic signal conversion circuit, the optoelectronic signal conversion circuit converts the reference light signal into a reference optoelectronic signal, the reference optoelectronic signal is amplified by the amplification circuit, and then the constant current pulse modulation circuit corrects the output current of the constant current pulse modulation circuit through the signal reference end to ensure the constant of the output light intensity of the laser light source. In addition, the modulation end of the constant current pulse modulation circuit is electrically connected to the output end of the single-chip microcomputer, and the pulse frequency of the modulation signal of the constant current pulse modulation circuit is controlled by the single-chip microcomputer. The single-chip microcomputer is used for controlling the laser pulse modulation circuit, the signal processing circuit and the communication circuit and the like, and calculating the turbidity measurement result.

[0043] The driving circuit board 3 is further provided with a power supply circuit, and the power supply circuit is used for converting a direct current input power into a stable working power required for circuit working. The input end of the power supply circuit is electrically connected to an external power supply, and the output end of the power supply circuit is electrically connected to the input end of the constant current pulse modulation circuit.

[0044] The receiving component comprises a signal processing circuit board 11, and the signal processing circuit board 11 is provided with an optoelectronic conversion circuit, a signal filter amplification circuit, an analog-digital conversion circuit and a communication circuit. The photovoltaic current signal received by the receiver 12 is converted into a voltage signal proportional to the scattering light intensity by the optoelectronic conversion circuit, the signal filter amplification circuit performs high-pass and low-pass filtering and amplification on the signal, and the analog-digital conversion circuit converts the analog signal into a digital signal. The output end of the receiver 12 is electrically connected to the light signal input end of the optoelectronic conversion circuit, the electrical signal output end of the optoelectronic conversion circuit is electrically connected to the input end of the signal filter amplification circuit, the output end of the signal filter amplification circuit is electrically connected to the input end of the analog-digital conversion circuit, the output end of the analog-digital conversion circuit is electrically connected to the input end of the single-chip microcomputer, the output end of the single-chip microcomputer is electrically connected to the input end of the communication circuit, and the output end of the communication circuit is electrically connected to an external terminal communication.

[0045] As an optional implementation of the utility model, the communication circuit adopts 485 circuit.

[0046] The shell 2 can be divided into an emission part containing the emission component and a receiving part containing the receiving component. The emission part and the receiving part are both immersed underwater. The emission part and the receiving part are connected through a rigid waterproof part, the rigid waterproof part contains the electric wire 1, and the driving circuit board 3 and the signal processing circuit board 11 are electrically connected through the electric wire 10. As an optional implementation of the utility model, the end face of the emission part close to one end of the receiving part is 45° relative to the propagation direction of the detection laser, that is, the end face is parallel to the emission plane mirror 8.

[0047] The outer side of the emission part is provided with a waterproof joint 1, and the water quality turbidity detection sensor connects the interface of the power supply circuit and the communication circuit with the external power supply and the external single-chip microcomputer communication terminal through the waterproof joint 1. The waterproof performance of the waterproof joint 1 is IP68.

[0048] The above specific embodiments are used to explain and illustrate the utility model, rather than limit the utility model, and any modification and change made to the utility model within the spirit and protection scope of the claims falls within the protection scope of the utility model.

[0049] The above is only the preferred embodiment of the utility model, so equivalent changes or modifications made to the structure, features and principles described in the utility model patent application scope are included in the utility model patent application scope.

Claims

1. A water quality turbidity detection sensor with a laser beam expander assembly, characterized in that: The water quality turbidity detection sensor is immersed in a water body, comprising a shell (2) and an emitting component and a receiving component arranged inside the shell (2); the emitting component emits detection laser vertically to the water body, and the detection laser forms scattered light after being scattered by particles in the water body; the receiving component is arranged in front of the emitting component in the propagation direction of the detection laser, and the optical axis of the receiving component is perpendicular to the optical axis of the detection laser; The emitting component comprises a laser light source (4), a beam expander lens (5) and an emitting assembly; the output end of the laser light source (4) is sequentially arranged with the beam expander lens (5) and the emitting assembly; the laser light source (4) emits emitting laser, the emitting laser is expanded by the beam expander lens (5) to form expanded laser, and the expanded laser forms detection laser after passing through the emitting assembly and is emitted vertically to the water body; The receiving component comprises a receiver (12), a receiving lens (13) and a receiving assembly; the optical axis of the receiving lens (13) is perpendicular to the optical axis of the detection laser; the scattered light enters the receiver (12) after sequentially passing through the receiving assembly and the receiving lens (13).

2. The water quality turbidity detection sensor with a laser beam expander assembly according to claim 1, characterized in that: The beam expander lens (5) adopts a double-convex or plano-convex converging lens; the optical axis of the beam expander lens (5) coincides with the optical axis of the emitting laser; the emitting laser converges at the focal point of the beam expander lens (5) to form expanded laser with a certain beam angle.

3. The water quality turbidity detection sensor with a laser beam expander assembly according to claim 1, characterized in that: The emitting assembly comprises an aperture diaphragm (6), an emitting sealing ring (7), an emitting plane mirror (8) and an emitting compression ring (9) arranged in the propagation direction of the expanded laser in sequence; the emitting compression ring (9) is mounted on the shell (2); the emitting plane mirror (8) is embedded on the emitting compression ring (9); the emitting plane mirror (8) is sealingly connected with the shell (2) through the emitting sealing ring (7).

4. The water quality turbidity detection sensor with a laser beam expander assembly according to claim 3, characterized in that: The emitting sealing ring (7), the emitting plane mirror (8) and the emitting compression ring (9) are coaxially arranged and are arranged obliquely relative to the optical axis of the emitting laser.

5. The water quality turbidity detection sensor with a laser beam expander assembly according to claim 4, characterized in that: The included angle between the common axis of the emitting sealing ring (7), the emitting plane mirror (8) and the emitting compression ring (9) and the optical axis of the emitting laser is 45 degrees.

6. The water quality turbidity detection sensor with a laser beam expander assembly according to claim 3, characterized in that: The shell (2) is divided into an emitting part accommodating the emitting component and a receiving part accommodating the receiving component; the emitting part and the receiving part are connected through a rigid waterproof part; the waterproof joint (1) is mounted on the emitting part; the front end surface of the emitting part is arranged obliquely relative to the optical axis of the emitting laser; the emitting sealing ring (7), the emitting plane mirror (8) and the emitting compression ring (9) are mounted on the front end surface of the emitting part.

7. The water quality turbidity detection sensor with a laser beam expander assembly of claim 1, wherein: The receiving assembly comprises a receiving lens (13), a receiving sealing ring (14) and a receiving plane mirror (15) arranged in the propagation direction of the received scattered light in sequence; the receiving lens (13) is a convex lens.

8. The water quality turbidity detection sensor with a laser beam expander assembly of claim 1, wherein: The exit component further comprises a driving circuit board (3) provided with a constant current pulse modulation circuit, an optoelectronic signal conversion circuit, an amplification circuit and a single-chip microcomputer; an input end of the laser light source (4) is electrically connected with a current output end of the constant current pulse modulation circuit, a reference output end of the laser light source (4) is electrically connected with a light signal input end of the optoelectronic signal conversion circuit, an electrical signal output end of the optoelectronic signal conversion circuit is electrically connected with an input end of the amplification circuit, an output end of the amplification circuit is electrically connected with a signal reference end of the constant current pulse modulation circuit, and a modulation end of the constant current pulse modulation circuit is electrically connected with the single-chip microcomputer.

9. The water quality turbidity detection sensor with a laser beam expander assembly of claim 1, wherein: The receiving component comprises a signal processing circuit board (11) provided with an optoelectronic conversion circuit, a signal filtering and amplification circuit, an analog-digital conversion circuit and a communication circuit; an output end of the receiver (12) is electrically connected with a light signal input end of the optoelectronic conversion circuit, an electrical signal output end of the optoelectronic conversion circuit is electrically connected with an input end of the signal filtering and amplification circuit, an output end of the signal filtering and amplification circuit is electrically connected with an input end of the analog-digital conversion circuit, an output end of the analog-digital conversion circuit is electrically connected with an input end of the communication circuit, and an output end of the communication circuit is electrically connected with a terminal outside for communication.

Images