Underwater light curtain speed measuring device and measuring method

Abstract

The invention discloses an underwater light curtain speed measurement device and a measurement method, the device comprises a measurement unit and an upper computer, the measurement unit comprises a first measurement assembly and a second measurement assembly, and the first measurement assembly and the second measurement assembly are arranged at an interval along the movement direction of a measured object; each of the first measuring assembly and the second measuring assembly comprises a light emitting module and a light receiving module which are vertically and oppositely arranged, so that a parallel light curtain perpendicular to the movement direction of a measured object is formed; a light inlet of the light receiving module is provided with double-slit structures which are arranged at intervals along the incident direction of the light curtain, so that the parallel laser curtain emitted by the light emitting module corresponding to the light receiving module is received; and the upper computer is in signal connection with the first measurement assembly and the second measurement assembly, so that the speed measurement of the light curtain is realized. Interference of external light is shielded as much as possible through the double-slit design, so that the underwater light curtain measurement precision is effectively improved, and the device can be suitable for various underwater speed measurement scenes and has the advantages of being non-contact, fast in response, small in error and the like.

Description

Technical Field

[0001] The present invention relates to an underwater light curtain speed measurement device and a measurement method, belonging to the technical field of underwater speed measurement equipment. Background Art

[0002] Currently, there are generally the following several methods for measuring the speed of underwater moving objects:

[0003] 1) Using an electromagnetic induction track, that is, fixing multiple electromagnetic induction devices on the track. When a moving object passes over the fixed track, an electrical signal is generated through electromagnetic induction. Record the time between the two signals, and calculate the object's moving speed based on the distance between the electromagnetic induction devices and the recorded time. This method must first magnetize the object before starting the measurement, and the magnetized object is vulnerable to the influence of the measurement device itself;

[0004] 2) Using a speed sensor installed on the object, such as a Doppler velocimeter, etc. This method can measure the speed of the object more accurately and is suitable for larger objects. Since it is a contact measurement, for small objects, the weight and other properties of the sensor itself will affect the speed of the object itself;

[0005] 3) Using non-contact light curtain measurement. Due to its simple structure and low cost, it has gradually become the mainstream speed measurement method. One side of the light curtain is provided with multiple light emitting ends, and the other side has multiple light receiving ends. When the object passes through the light curtain, it blocks the light signal, thereby triggering the timing device to start timing, and stops timing when passing through another light curtain. The measurement is carried out based on the distance between the light curtains and the recorded time.

[0006] Although underwater light curtain measurement has advantages such as non-contact and high precision, and can be applied to various measurement scenarios, if the external light is relatively strong, or the object emits strong light when launched, due to the phenomena of refraction, reflection, scattering, etc. of light that generally exist underwater, it is often very difficult for the light receiving end to only capture the light curtain surface emitted by the light emitting end during actual experiments. Various bright beams of refraction, reflection, and scattering will cause errors in the photoelectric data, making it difficult to accurately capture the final data. Summary of the Invention

[0007] Object of the Invention: Aiming at the problems existing in the prior art, the present invention provides an underwater light curtain speed measurement device and a measurement method, which can effectively shield the interference of external light through a double-slit design, thereby effectively improving the accuracy of underwater light curtain measurement and solving problems such as large measurement errors existing in existing devices.

[0008] Technical solution: To achieve the above object, the present invention provides an underwater light curtain speed measurement device, including a measurement unit and a host computer. The measurement unit includes a first measurement component and a second measurement component, which are arranged at intervals along the moving direction of the object to be measured. Both the first measurement component and the second measurement component include a vertically and oppositely arranged light emission module and a light reception module, thereby forming a parallel light curtain perpendicular to the moving direction of the object to be measured. A double-slit structure is arranged at intervals along the incident direction of the light curtain at the light incident port of the light reception module, thereby receiving the parallel laser light curtain emitted by the corresponding light emission module. The host computer is respectively connected to the first measurement component and the second measurement component by signals, thereby calculating the moving speed of the object to be measured.

[0009] Further, an absorption design is adopted between the double-slit structures to further reduce the measurement error caused by external light entering the slits due to reflection, refraction, etc.

[0010] Specifically, the light emission module includes a laser point light source and an optical lens group. The light emitted by the laser point light source is expanded into a large-size parallel laser beam by the optical lens group, and then forms a parallel laser light curtain through the single-slit structure at the light exit.

[0011] Further, the laser point light source adopts a purple laser with a wavelength of 400nm. Using purple light that is not easily absorbed by water with a wavelength of 400nm as the emitted light can effectively improve the measurement accuracy.

[0012] Specifically, the light reception module includes a plurality of photomultiplier tube arrays, which are spliced to form a photomultiplier tube of m rows × n columns, where n≥3. The photomultiplier tube array is used to receive the parallel laser light curtain passing through the double-slit structure and is connected to the host computer by signals through a data acquisition unit.

[0013] Further, the light reception module further includes a motor drive unit, which is connected to the host computer by signals through a data acquisition unit and is used to realize the displacement drive of the photomultiplier tube array, thereby realizing the alignment adjustment between the photomultiplier tube array and the double-slit structure, and effectively solving the alignment problem between the light emission end and the light reception end of the underwater light curtain.

[0014] Further, both the first measurement component and the second measurement component adopt a sealed waterproof design, and at the same time, they are connected and fixed through a fixed bracket.

[0015] In addition, the present invention also provides a measurement method based on the above underwater light curtain speed measurement device, including the following steps:

[0016] S1. When the object to be measured passes through the first measurement component, the data acquisition unit respectively records the time t 1 、t 2 …tn , and the row positions a of each column of photomultiplier tubes corresponding thereto 1 、a 2 …a n ;

[0017] S2. When the object to be measured passes through the second measurement component, the data acquisition unit respectively records the times t 1 ’、t 2 ’…t n ’ when the object to be measured passes through each column of photomultiplier tubes in sequence, and the row positions b of each column of photomultiplier tubes corresponding thereto 1 、b 2 …b n ;

[0018] S3. According to the data collected by the data acquisition unit, the longitudinal distance traveled by the object to be measured is calculated by the host computer as:

[0019] x 1 =a 1 -b 1 ,

[0020] x 2 =a 2 -b 2 ,

[0021] ……

[0022] x n =a n -b n ,

[0023] The actual distance traveled by the object to be measured is obtained as:

[0024]

[0025] ……

[0026]

[0027] where y is the distance between the first measurement component and the second measurement component, and the moving speed of the object to be measured is obtained as:

[0028]

[0029] ……

[0030]

[0031] Finally, the average speed of the object to be measured is obtained as:

[0032]

[0033] Further, before data calculation, the host computer is first used to screen and process the collected data, specifically including: if the photomultiplier tubes in each column on the same measurement component are not continuously triggered along the moving direction of the object to be measured, it is determined that the corresponding photomultiplier tube data is invalid data.

[0034] Further, during the data calculation process, the host computer is further used to screen and process the collected data, specifically including: if the calculated moving speed is lower than the set threshold, it is determined that the corresponding photomultiplier tube data is invalid data.

[0035] Beneficial effects: Based on the principle of photoelectric speed measurement, the present invention effectively improves the accuracy of underwater light curtain measurement by using the double-slit design at the light inlet to shield the interference of external light as much as possible. It can be applied to various underwater speed measurement scenarios, especially in test scenarios with other light sources during the test process, such as underwater range tests and performance evaluations of artillery systems. In addition, the device has a simple structure, low cost, convenient operation, and high automation degree, and has advantages such as non-contact, fast response, and small error, with strong practicability. Description of the Drawings

[0036] Figure 1 It is a schematic structural diagram of the underwater light curtain speed measurement device in the embodiment of the present invention;

[0037] Figure 2 It is a schematic optical path diagram of the underwater light curtain speed measurement device in the embodiment of the present invention;

[0038] Figure 3 It is a schematic structural diagram of the light emission module in the embodiment of the present invention;

[0039] Figure 4 It is a schematic front structure diagram of the light receiving module in the embodiment of the present invention;

[0040] Figure 5 It is a schematic side structure diagram of the light receiving module in the embodiment of the present invention;

[0041] Figure 6 It is a schematic circuit framework diagram of the underwater light curtain speed measurement device in the embodiment of the present invention;

[0042] Figure 7 It is a schematic measurement principle diagram of the underwater light curtain speed measurement device in the embodiment of the present invention;

[0043] In the figure, it includes: 1. The first measurement component, 2. The second measurement component, 3. The fixed bracket, 4. The host computer, 5. The light emission module, 6. The light receiving module, 7. The object to be measured, 51. The point light source, 52. The optical lens group, 53. The single-slit structure, 61. The photomultiplier tube array, 62. The motor drive unit, 63. The double-slit structure, 631. The first slit structure, 632. The second slit structure. Detailed implementation manners

[0044] The preferred implementation manners of the present invention will be described below in conjunction with the accompanying drawings, so as to more clearly and completely elaborate the technical solution of the present invention.

[0045] In the existing light curtain speed measurement device, it is very difficult for the light receiving end to only capture the light curtain surface emitted by the light emitting end. Various bright light beams of refraction, reflection, and scattering will cause errors in the optoelectronic data, making it difficult to accurately capture the final data. Secondly, the commonly used light curtain surface is easily absorbed by water underwater, resulting in a weak spectral effect during actual experiments, thereby affecting the final data. Finally, the point-to-point emission and reception mode is too costly and complex to maintain, so it is not suitable for the construction of a large target surface measurement system. At the same time, a number of light receiving ends and a number of light emitting ends that are in one-to-one correspondence and calibrated on the shore are easily affected by the underwater environment when hoisted underwater, and it is difficult to ensure the docking accuracy, thus affecting the measurement process.

[0046] An underwater light curtain speed measurement device is provided here, which can effectively solve a series of technical problems existing in the existing light curtain. Refer to Figure 1 , the device mainly includes a measurement unit and a host computer 4. The measurement unit includes a first measurement component 1 and a second measurement component 2, which are arranged at intervals along the movement direction of the object to be measured 7 and are fixedly supported by a fixed bracket 3; both the first measurement component 1 and the second measurement component 2 include a vertically and oppositely arranged light emitting module 5 and a light receiving module 6, thereby forming a parallel light curtain perpendicular to the movement direction of the object to be measured 7; the host computer 4 is electrically connected to the first measurement component 1 and the second measurement component 2 respectively (in addition, wireless communication and other methods can also be used for signal transmission), thereby calculating the movement speed of the object to be measured 7.

[0047] Refer to Figure 2 , Figure 3 , the light emitting module 5 uses a purple laser with a wavelength of 400 nm as a point light source 51, and the light emitted by the point light source 51 is expanded into a large-size parallel laser beam through an optical lens group 52, and then a parallel laser curtain is formed through a single slit structure 53 at the light outlet. In this way, a large-size laser curtain can be obtained through a small number of laser emitters, effectively saving the system cost, simplifying the circuit, improving the system stability and maintainability, and reducing the accuracy requirements for the light source position, which is beneficial to the smooth progress of the measurement process. In addition, using purple light with a wavelength of 400 nm that is not easily absorbed by water as the emitted light can effectively improve the measurement accuracy.

[0048] Refer to Figure 3The purple lasers are arranged at intervals in the vertical direction, and the seamless splicing of parallel laser beams is achieved through the corresponding optical lens group 52. Therefore, the large target surface is expanded according to the test requirements, and the parallel laser beams are spliced ​​into a large-size light curtain, which can be suitable for the construction of a large target surface measurement system.

[0049] Reference Figure 2 , Figure 4 The light receiving module 6 has a double slit structure 63 arranged at intervals along the incident direction of the light curtain, namely a first slit structure 631 and a second slit structure 632, at the light entrance, so as to receive the parallel laser curtain emitted by the corresponding light emitting module 5. Through this double slit design, most of the oblique incident light beams can be shielded to ensure that the light receiving module 6 can accurately capture the parallel laser curtain in the vertical direction during the test.

[0050] Reference Figure 2 Among the external light entering from the first slit structure 631, only a small part of the light beam close to vertical incidence can be received by the light receiving module 6, and most of the remaining light beams will be confined in the space between the double slit structures 63. Even if reflection, refraction, etc. occur, they will be further shielded as much as possible by the second slit structure 632, greatly reducing the interference of external light. Preferably, a light absorption design is further adopted between the double slit structures 63, specifically: light absorbing materials are arranged on the inner wall between the double slit structures 63 to further reduce the measurement error caused by reflection, refraction, etc. after the external light enters the slit.

[0051] Furthermore, the light receiving module 6 includes a plurality of longitudinally spliced ​​photomultiplier tube arrays 61, which are used to receive the parallel laser curtain passing through the double slit structure 63, and are electrically connected to the host computer 4 through the data acquisition unit. Here, an array detector is used to realize light curtain detection. On the one hand, effective data can be screened according to the triggering process of each column of photomultiplier tubes, and underwater invalid interference data can be filtered as much as possible to improve the reliability and accuracy of the data. On the other hand, the average speed of the measured object 7 passing through each column of photomultiplier tubes can be obtained, further improving the measurement accuracy and reducing interference.

[0052] Furthermore, the optical receiving module 6 also includes a motor drive unit 62, which is electrically connected to the host computer 4 through the data acquisition unit, and is used to realize the displacement drive of the photomultiplier tube array 61 perpendicular to the incident direction of the light curtain (which may include lateral and longitudinal adjustments), thereby realizing the alignment adjustment of the photomultiplier tube array 61 and the double slit structure 63, effectively solving the alignment problem of the light emitting end and the light receiving end of the underwater light curtain.

[0053] Exemplarily, the photomultiplier tube array 61 adopts an array detector composed of 4 rows × 4 columns of photomultiplier tubes. Each photomultiplier tube can convert a weak optical signal into an electrical signal. After amplification and conversion, the output signal can be digitally stored in the data acquisition unit and then transmitted to the host computer 4 for processing. The size of each photomultiplier tube is 3mm × 3mm, so the size of each photomultiplier tube array 61 is 12mm × 12mm.

[0054] Referring to Figure 5 , every 4 photomultiplier tube arrays 61 are longitudinally spliced into a group. The electrical signals are collected and processed by a data acquisition unit, and the horizontal drive is performed by a motor drive unit 62, thus simplifying the internal structure of the module, testing efficiently and saving costs at the same time. Taking 16 groups of photomultiplier tube arrays as an example, the height of the optical receiving module 6 can reach 16×48mm, and the width is still 12mm. Therefore, both the single-slit structure 53 and the double-slit structure 63 can be designed to be 800mm high × 15mm wide. The optical emission module 5 can adopt 5 violet lasers, and each violet laser forms a parallel laser beam with a height of 160mm through an optical lens group 52.

[0055] Furthermore, for each group of photomultiplier tube arrays, the data acquisition unit can collect the photoelectric data of each photomultiplier tube array 61 one by one. For example: if the photomultiplier tube can receive the corresponding photoelectric signal, it is recorded as 1, otherwise it is recorded as 0. In this way, each column of photomultiplier tubes can form a hexadecimal data, and each photomultiplier tube array 61 contains 4-bit data, that is, 0x0000~0xFFFF, so as to facilitate the host computer 4 to obtain the corresponding photomultiplier tube status data and position data. In addition, all data acquisition units can be time-aligned with the host computer 4 when starting up, so as to align the time frames of the photoelectric data.

[0056] Referring to Figure 6 , taking 16 groups of photomultiplier tube arrays as an example, every 4 photomultiplier tube arrays 61 form a group of photomultiplier tube arrays. The data acquisition is completed by a data acquisition unit. After the data acquisition of 16 groups of photomultiplier tube arrays is completed, the data is summarized by the first processing chip, and finally uploaded to the host computer 4 for processing through the Ethernet communication protocol. Exemplarily, the data acquisition unit is composed of an amplification conversion, a comparison circuit and a second processing chip. The first processing chip and the second processing chip can adopt the FPGA chip with the model number EP4CE10F17C6N. At the same time, each group of photomultiplier tube arrays is connected to a motor drive unit 62 through the second processing chip to realize the horizontal drive control.

[0057] In addition, to ensure the waterproof and airtight performance, the optical emission module 5 and the optical reception module 6 are respectively and hermetically arranged in the aluminum alloy frame, and then fixed to the fixed bracket 3 through the aluminum alloy frame. Specifically, the aluminum alloy frame can be sealed by means of waterproof glue, watertight joints and positive pressure sealing, etc. At the same time, a highly transparent glass is installed at the slit structure through waterproof glue.

[0058] Refer to Figure 7 , the measurement method of the above underwater light curtain speed measurement device is as follows:

[0059] 1) Before the test, hoist the device onto the moving track of the object to be measured 7, and ensure that the two groups of measurement components are arranged at intervals along the moving direction of the object to be measured 7;

[0060] 2) Power-on initialization: For each group of measurement components, first turn on the optical emission module 5 to emit a parallel laser curtain through the single-slit structure 53, and then collect 16 groups of photomultiplier tube array group data through the data acquisition unit and upload them to the host computer 4, so as to judge whether each photomultiplier tube array group has been aligned with the double-slit structure 63. If all photomultiplier tubes can receive photoelectric data, it is confirmed that the photomultiplier tube array group has been aligned. Otherwise, further judge the positional relationship between the two according to the collected photoelectric data, and realize the horizontal adjustment of the photomultiplier tube array group through the motor drive unit 62 until all photomultiplier tubes can receive photoelectric data;

[0061] 3) Start the test:

[0062] When the object to be measured 7 passes through the first measurement component 1, it will pass through each column of photomultiplier tubes in sequence along the moving direction, and thus record the time t 1 , t 2 , t 3 , t 4 , as well as the row positions a 1 , a 2 , a 3 , a 4 corresponding to each column of photomultiplier tubes;

[0063] When the object to be measured 7 passes through the second measurement component 2, it will also pass through each column of photomultiplier tubes in sequence along the moving direction, and thus record the time t 1 ’, t 2 ’, t 3 ’, t 4 ’, as well as the row positions b 1 , b 2 , b 3 , b 4 corresponding to each column of photomultiplier tubes;

[0064] According to the data collected by the data acquisition unit, the longitudinal distance traveled by the object to be measured can be calculated by the host computer 4 (although the object to be measured is perpendicular to the parallel light curtain emission, there may be a certain longitudinal offset due to its own weight) as:

[0065] x 1 = a 1 - b 1 ,

[0066] x 2 = a 2 - b 2 ,

[0067] x 3 = a 3 - b 3 ,

[0068] x 4 = a 4 - b 4 ,

[0069] Thus, the actual distance traveled by the object to be measured is:

[0070]

[0071] where y is the distance between two sets of measurement components, and the movement speed of the object to be measured is obtained as:

[0072]

[0073] Finally, the average speed of the object to be measured 7 is obtained as:

[0074]

[0075] Of course, in other embodiments, the average speed can also be calculated by calculating the average time and average distance that the object to be measured 7 passes through the first measurement component 1 and the second measurement component 2, which will not be elaborated here.

[0076] It should be noted that during the process of the object to be measured passing by, the light rays incident on the photomultiplier tube will be blocked, causing a change in the photoelectric state of the photomultiplier tube, thereby obtaining the passing time and position of the object to be measured. However, during the test process, not only the object to be measured will block the light rays, but also foreign objects such as plankton or foreign objects driven by the impact force of the object to be measured during the test will block the light rays, resulting in the data of the photomultiplier tube collected not being completely accurate. Therefore, in order to improve the measurement accuracy, it is also necessary to screen and process the collected data, specifically including:

[0077] a. If the photomultiplier tubes in each column on the same measurement component are not continuously triggered along the moving direction of the object to be measured, it is determined that the corresponding photomultiplier tube data is invalid data, thereby excluding isolated or chaotic data points;

[0078] b. If the photomultiplier tubes in each column are continuously triggered, but the calculated moving speed is lower than the set threshold (such as 10 m / s), it is determined that the corresponding photomultiplier tube data is invalid data to further exclude external interference.

[0079] In addition, according to the different sizes of the object to be measured, during the process of the object to be measured passing by, one or more photomultiplier tubes in the same column of photomultiplier tubes may be blocked simultaneously, or one or more photomultiplier tubes in the same row of photomultiplier tubes may be blocked simultaneously. Of course, the discontinuous data points in the row and column positions need to be excluded first, and then fixed points (such as the front end) can be selected based on the principle of unity, and the time when this point passes through each column of photomultiplier tubes and the corresponding row position can be recorded.

[0080] The above specific implementation manners only describe the preferred implementation manners of the present invention, rather than limiting the protection scope of the present invention. Without departing from the design concept and spirit scope of the present invention, various deformations, substitutions, and improvements made by those of ordinary skill in the art to the technical solutions of the present invention according to the written description and drawings provided by the present invention shall fall within the protection scope of the present invention.

Claims

1. An underwater light curtain speed measuring device, characterized in that: It includes a measuring unit and a host computer, wherein the measuring unit includes a first measuring component and a second measuring component, which are arranged at intervals along the moving direction of the object to be measured; the first measuring component and the second measuring component both include a light emitting module and a light receiving module that are arranged vertically and oppositely, thereby forming a parallel light curtain perpendicular to the moving direction of the object to be measured; a double slit structure arranged at intervals along the incident direction of the light curtain is provided at the light inlet of the light receiving module, thereby receiving the parallel light curtain emitted by the corresponding light emitting module; the host computer is respectively connected to the signals of the first measuring component and the second measuring component, thereby calculating the moving speed of the object to be measured.

2. The underwater light curtain speed measuring device according to claim 1, characterized in that: A light absorption design is adopted between the double slit structures.

3. The underwater light curtain speed measuring device according to claim 1, characterized in that: The light emitting module comprises a laser point light source and an optical lens group, wherein the light emitted by the laser point light source is expanded into a parallel laser beam by the optical lens group, and then forms a parallel laser curtain through a single slit structure at a light outlet.

4. The underwater light curtain speed measuring device according to claim 3, characterized in that: The laser point light source adopts a violet laser with a wavelength of 400nm.

5. The underwater light curtain speed measuring device according to claim 1, characterized in that: The light receiving module includes a plurality of photomultiplier tube arrays, which are spliced ​​to form m rows×n columns of photomultiplier tubes, where n≥3. The photomultiplier tube array is used to receive the parallel laser curtain passing through the double slit structure and is connected to the host computer signal through the data acquisition unit.

6. The underwater light curtain speed measuring device according to claim 5, characterized in that: The light receiving module also includes a motor drive unit, which is connected to the host computer signal through the data acquisition unit and is used to realize the displacement drive of the photomultiplier tube array, thereby realizing the alignment adjustment of the photomultiplier tube array and the double slit structure.

7. The underwater light curtain speed measuring device according to claim 1, characterized in that: The first measuring component and the second measuring component both adopt a sealed and waterproof design, and are connected and fixed by a fixing bracket.

8. A measurement method based on the underwater light curtain speed measuring device according to claim 5, characterized in that: The following steps are involved: S1. When the object to be measured passes through the first measuring component, the time t1, t2, ...t2 of each column of photomultiplier tubes is recorded by the data acquisition unit. n , and the corresponding photomultiplier tube row positions a1, a2…a n ; S2. When the object under test passes through the second measuring component, the data acquisition unit records the time t1', t2'...t2 of each column of photomultiplier tubes when the object under test passes through the second measuring component. n ', and the corresponding photomultiplier tube row positions b1, b2...b n ; S3. Based on the data collected by the data acquisition unit, the host computer calculates the longitudinal distance traveled by the object being measured as: x1=a1-b1, x2=a2-b2, …… x n =a n -b n , The actual distance traveled by the measured object is obtained as follows: Where y is the distance between the first measuring component and the second measuring component, and the moving speed of the measured object is obtained as follows: Finally, the average speed of the measured object is:

9. The measuring method according to claim 8, characterized in that: Before data calculation, the collected data is first screened and processed by the host computer, specifically including: if the columns of photomultiplier tubes on the same measurement component are not continuously triggered along the movement direction of the measured object, the corresponding photomultiplier tube data is judged to be invalid data.

10. The measuring method according to claim 8, characterized in that: During the data calculation process, the collected data is further screened and processed by the host computer, specifically including: if the calculated motion speed is lower than the set threshold, the corresponding photomultiplier tube data is judged to be invalid data.

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