CN118548951B - Micro-flow measurement method and device suitable for droplet jitter - Google Patents

Abstract

The present invention provides a micro-flow measurement method and device suitable for droplet jitter, the method comprising: respectively identifying the droplet contour in images of the droplet outlet collected from multiple directions to obtain position information of the droplet edge points, wherein the image is an image of the droplet before it leaves the outlet; calculating the volume of the droplet according to the position information of the droplet edge points for the images in each direction; and calculating the flow rate according to the droplet volume calculated from the images in multiple directions over a period of time.

Description

Micro-flow measurement method and device suitable for droplet jitter

Technical Field

The present invention relates to the field of flow measurement, and in particular to a micro-flow measurement method and device suitable for droplet jitter.

Background Art

As the demand for products in industries such as semiconductor manufacturing, medical chemicals, and bioengineering continues to move toward precision and micro-quantity, The measurement of micro-flow of fluids has gradually become the basic condition for chip-based products, such as microfluidic chips, micro-dispensing, drug injection, insulin pumps, etc. However, due to the lag in the research of micro-flow measurement related technologies, the research and development process in frontier basic science, chip manufacturing and other fields has been seriously restricted.

At present, the methods of liquid flow measurement can be divided into two categories: contact and non-contact. Common contact measurement methods include float type, differential pressure type, volumetric type, turbine type, etc., but these methods are difficult to measure small flow (for example, less than 1 ). The non-contact measurement method is the ultrasonic Doppler method, which has a wide range of applications. However, it is difficult to perform effective measurement because the intensity of the scattered spectrum in the liquid at a small flow rate is very weak.

Moreover, in actual measurement scenarios, the droplet usually shakes at the outlet, which may also affect the measurement results when using existing measurement technologies.

Summary of the invention

In view of this, the present invention provides a micro-flow measurement method suitable for droplet jitter, comprising:

Respectively identifying the contours of the droplets in the images of the droplet outlet collected from multiple directions to obtain the position information of the edge points of the droplets, wherein the images are images of the droplets before they leave the outlet;

Calculating the volume of the droplet according to the position information of the edge point of the droplet for the image in each orientation;

The flow rate is calculated based on the droplet volume calculated from the images at multiple positions over a period of time.

Optionally, identifying a droplet contour in the image comprises:

Determine a minimum circumscribed rectangular area of the droplet in the image, wherein a horizontal side of the minimum circumscribed rectangular area is parallel to a horizontal axis of an image coordinate system, and a vertical side of the minimum circumscribed rectangular area is parallel to a vertical axis of the image coordinate system;

A droplet contour is identified in the minimum circumscribed rectangular area.

Optionally, calculating the volume of the droplet according to the position information of the edge point of the droplet includes:

Dividing the droplet in the image into a plurality of micro-elements along the vertical axis, and determining the horizontal axis coordinates of the two side edges of each micro-element according to the position information of the edge points of the droplet;

The volume of the droplet is calculated according to the horizontal axis coordinates of the two side edges of each micro-element and the height of the micro-element.

Optionally, the volume of the droplet is calculated using the following method: :

,

in represents the minimum circumscribed rectangular area, express The vertical axis coordinate on the top of express The vertical axis coordinate below, is the horizontal coordinate of the edge of one side corresponding to the vertical axis i, is the horizontal coordinate of the edge on the other side of the vertical axis i, is the height of the microelement.

Optionally, the height of the micro-element is equal to the pixel size of the image.

Optionally, the flow rate is calculated using :

,

in, , , Respectively representing the droplet volumes corresponding to the images at three positions at the same time; Indicates the image acquisition time; Indicates the image acquisition frame interval.

Optionally, acquiring an image at the droplet outlet includes:

storing multiple frames of images at the droplet outlet of the image acquisition device in the first queue in sequence;

The areas of liquid droplets in the images are determined based on the adjacent frame images in the first queue, and the images with liquid droplets squeezed out are screened out and stored in the second queue, and the remaining images in the first queue are deleted.

Optionally, judging the area of the liquid droplets in the image according to the adjacent frame images in the first queue to filter out the image with the liquid droplets squeezed out includes:

Calculate the droplet area difference in adjacent frame images ,in , Respectively represent the two consecutive frames before and after, Indicates The droplet area in the frame image, Indicates The droplet area in the frame image;

Determine the droplet area difference Is it greater than 0? When it is greater than 0, the corresponding two frames of images are determined to be images with droplet extrusion.

Correspondingly, the present invention provides a liquid micro-flow measurement device, characterized in that it includes: a processor and a memory connected to the processor; wherein the memory stores instructions that can be executed by the processor, and the instructions are executed by the processor so that the processor executes the above-mentioned micro-flow measurement method suitable for droplet jitter.

The present invention also provides a liquid micro-flow measurement system, comprising:

A plurality of image acquisition devices, used for acquiring images at the droplet outlet from different directions;

A computing device for use in the above-mentioned micro-flow measurement method applicable to droplet jitter.

According to the micro-flow measurement method and equipment suitable for droplet jitter provided in the present application, the image at the droplet outlet is identified to obtain the contour position information of the droplet in the image, the volume of the droplet is calculated based on the position information in the image, and the flow information is obtained based on the change in the droplet volume in the multi-directional image. The calculation method based on computer vision can overcome the influence of the droplet jitter phenomenon on the flow measurement, realize accurate measurement of the tiny flow of the liquid, and meet the needs of on-site in-situ detection.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a flow chart of a liquid micro-flow measurement method in an embodiment of the present invention;

FIG2 is a schematic diagram of a measurement scenario in an embodiment of the present invention;

FIG. 3 is a schematic diagram of the droplet volume measurement principle in an embodiment of the present invention.

DETAILED DESCRIPTION

The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

As shown in Figure 1, an embodiment of the present invention provides a liquid micro-flow measurement method, which obtains liquid flow information based on computer vision technology. The method can be executed by an electronic device such as a computer or a server, and includes the following operations:

S1, respectively identify the droplet contour in the image of the droplet outlet collected from multiple directions, and obtain the position information of the droplet edge point. The image is an image of the droplet before it leaves the outlet. Specifically, the application scenario of this solution is that the liquid is slowly squeezed vertically downward from the outlet of the needle-shaped (tubular) channel, and multiple image acquisition devices collect images horizontally toward the outlet. Referring to the schematic diagrams shown in Figures 2 and 3, the three image acquisition devices collect droplet images in three-dimensional space from different directions to obtain droplet images in the XY plane.

In this embodiment, the droplet is squeezed out of the outlet but does not leave the outlet. Due to the jitter phenomenon, the droplet is offset and appears asymmetrical and irregular in the image. The areas on both sides of the vertical center line (X axis) of the droplet outlet are different, and both sides of the bottom of the droplet may be on the same side of the center line.

This solution continuously acquires images during the liquid extrusion process. As the liquid is extruded, the volume of the droplet increases, and the area of the droplet region in the image will increase.

S2, for images in various directions, the volume of the droplet is calculated according to the position information of the edge point of the droplet. Since the image acquisition device acquires images horizontally toward the outlet, the obtained image is a two-dimensional image of the XY plane in FIG3 (the projection of the droplet in space on the XY plane). The droplet contour can be segmented from the image by an image segmentation algorithm, such as a neural network model or a machine vision algorithm, and the coordinate value of each point on the contour in the XY coordinate system is the position information of the edge point of the droplet.

Although the shape of the droplet in the two-dimensional image is irregular, the droplet in space is sliced horizontally, and the resulting slices can be regarded as approximately perfect circles. The horizontal lines in the droplet area in Figure 3 represent tangent lines. Corresponding to the three-dimensional space, each slice can be regarded as approximately perfect circles, except that the centers of the circles are not on the same straight line.

The distance between the two sides of each tangent line in the image is the diameter of the corresponding circular slice. If the diameter of the droplet at each location is known, the volume of the entire droplet can be calculated.

S3, calculate the flow rate based on the droplet volume calculated from the images in multiple directions within a period of time. This step calculates the flow rate within a period of time by the change in the droplet volume within a period of time. In this embodiment, since the droplet shape is asymmetric, the droplet volumes calculated from images in different directions are not equal. In order to accurately obtain the flow rate, it is necessary to combine the volume calculated from the images in multiple directions to calculate the flow rate. There are many specific ways to combine. As an example, the flow rate is calculated using the following method :

,

in, , , Respectively represent the droplet volumes corresponding to the images in three directions at the same moment; Indicates the image acquisition time; Indicates the image acquisition frame interval.

The above algorithm is a calculation method provided for the three image acquisition devices of the embodiments shown in Figures 2 and 3, that is, images in three directions. In other embodiments, images in more or fewer directions may also be used, and the above algorithm may be adjusted accordingly.

According to the micro-flow measurement method suitable for droplet jitter provided by an embodiment of the present invention, the image at the droplet outlet is identified to obtain the contour position information of the droplet in the image, the volume of the droplet is calculated based on the position information in the image, and the flow information is obtained based on the change of the droplet volume in the multi-directional image. The calculation method based on computer vision can overcome the influence of the droplet jitter phenomenon on the flow measurement, realize accurate measurement of the tiny flow of the liquid, and meet the needs of on-site in-situ detection.

As shown in FIG2 , in order to ensure that the image acquisition devices in each direction capture images synchronously, when the droplet starts to flow, the pulse signal is started. (time ), the synchronous trigger controller receives the transmission signal , trigger signal after delay , and (time ), the image acquisition device receives the corresponding signal to trigger the image acquisition device to collect data, thereby obtaining morphological images of the droplets at different angles at the same moment, thereby improving the accuracy of subsequent image data processing and calculation.

As a preferred embodiment, in step S1, the following method is specifically adopted to recognize the droplet contour for an image in one orientation:

The minimum circumscribed rectangular area of the droplet is determined in the image, and the horizontal side of the minimum circumscribed rectangular area is parallel to the horizontal axis of the image coordinate system, and the vertical side is parallel to the vertical axis of the image coordinate system. Specifically, such a parallel relationship can be ensured from the hardware environment, or adjusted to such a parallel relationship from the perspective of image processing.

The droplet contour is identified in the minimum bounding rectangle area.

Firstly, extracting the minimum circumscribed rectangular area from the image can remove most of the background to improve the efficiency and accuracy of droplet contour recognition; the parallel relationship between the edges of the minimum circumscribed rectangular area and the coordinate axis ensures that the slice corresponding to the horizontal tangent is a perfect circle, thereby improving the accuracy of volume calculation.

As a preferred embodiment, in step S2, the volume of the droplet is calculated for an image in one orientation in the following manner:

The droplet in the image is divided into multiple micro-elements along the vertical axis, and the horizontal axis coordinates of the two side edges of each micro-element are determined according to the position information of the edge points of the droplet. The droplet is cut into multiple slices in the horizontal direction, and each slice actually has a certain thickness. Corresponding to the two-dimensional image, the horizontal lines shown in Figure 3 are micro-elements, and these micro-elements have a certain height. For example, the height of the micro-element can be equal to the pixel size of the image.

The volume of the droplet is calculated based on the horizontal axis coordinates of the two side edges of each microelement and the height of the microelement. In this embodiment, the microelements in the image are regarded as the projections of a cylinder on a two-dimensional plane, the distance between the left and right ends of the microelement is the diameter of the cylinder, and the height of the microelement is the height of the cylinder. The volume of the cylinder can be calculated based on the diameter and height of the cylinder, so the sum of the volumes of the cylinders is the volume of the entire droplet.

The minimum bounding rectangle area in Figure 3 The position of the upper left corner point R ₀ is (x ₀ , y _r ), and the position of the lower left corner point R _n is (x _n , y _r ). By traversing the volumes of the disks corresponding to all infinitesimal elements in the interval [x ₀ , x _n ], the volume of the entire droplet can be obtained.

Furthermore, the volume of the droplet can be calculated as follows: :

,

represents the droplet volume calculated for the image of the Nth image acquisition device, where represents the minimum enclosing rectangular area, express The vertical axis coordinate on the top of express The vertical axis coordinate below, corresponds to the vertical axis i (in Figure 3 ), corresponds to the vertical axis i (in Figure 3 ), is the height of the microelement.

As shown in FIG. 2 , in one embodiment, step S1 includes the following operations:

S11, storing multiple frames of images at the droplet outlet of the image acquisition device in the first queue in sequence;

S12, judging the droplet area in the image according to the adjacent frame images in the first queue, filtering out the images with droplet extrusion and storing them in the second queue, and deleting the remaining images in the first queue. Step S11 and step S12 are synchronously executed by independent threads respectively, the first thread is used to store images in the first queue _Q1 [n], and the second thread is used to judge the images and store the qualified images in the second queue _Q2 [n], so as to improve the processing efficiency.

Step S12 can be specifically judged in the following manner:

Calculate the droplet area difference in adjacent frame images ,in , Respectively represent the two consecutive frames before and after, Indicates The droplet area in the frame image, Indicates The droplet area in the frame image;

Determine the droplet area difference Is it greater than 0? When it is greater than 0, the corresponding two frames of images are determined to be images with droplet extrusion.

The above preferred solution makes a real-time judgment on whether liquid is squeezed out of the pipe outlet, ensuring that when there are effective droplets at the pipe outlet, the visual information of its morphological changes is collected from multiple angles, and real-time processing and calculation are performed. This method enables images with droplets to be collected and subsequently calculated faster and more accurately, and avoids collecting too many useless images when droplets have not yet flowed out, thereby improving measurement efficiency.

It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

The present invention is described with reference to the flowcharts and/or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each process and/or box in the flowchart and/or block diagram, as well as the combination of the processes and/or boxes in the flowchart and/or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate a device for implementing the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device that implements the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

These computer program instructions may also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims (5)

1. A micro-flow measurement method suitable for droplet jitter, characterized by comprising: When the droplet starts to flow, at time Start pulse signal , the synchronous trigger controller receives the transmission signal , after a delay at time Trigger signal , and , the image acquisition device receives the corresponding signal for acquisition, and obtains the image of the droplet outlet collected from multiple directions; Respectively identifying the contour of the droplet in the image of the droplet outlet collected from multiple directions to obtain the position information of the edge point of the droplet, wherein the image is an image of the droplet before it leaves the outlet, identifying the contour of the droplet in the image includes determining the minimum circumscribed rectangular area of the droplet in the image, wherein the horizontal side of the minimum circumscribed rectangular area is parallel to the horizontal axis of the image coordinate system and the vertical side is parallel to the vertical axis of the image coordinate system, and identifying the contour of the droplet in the minimum circumscribed rectangular area; The volume of the droplet is calculated according to the position information of the edge point of the droplet for the image at the same time in all directions, including dividing the droplet in the image into a plurality of micro-elements along the vertical axis, determining the horizontal axis coordinates of the two side edges of each micro-element according to the position information of the edge point of the droplet, and calculating the volume of the droplet according to the horizontal axis coordinates of the two side edges of each micro-element and the height of the micro-element. : , in represents the minimum circumscribed rectangular area, express The vertical axis coordinate on the top of express The vertical axis coordinate below, is the horizontal coordinate of the edge of one side corresponding to the vertical axis i, is the horizontal coordinate of the edge on the other side of the vertical axis i, is the height of the micro-element, and the height of the micro-element is equal to the pixel size of the image; Calculate the flow rate based on the droplet volume calculated from the images at multiple locations over a period of time : , in, , , Respectively representing the droplet volumes corresponding to the images at three positions at the same time; Indicates the image acquisition time; Indicates the image acquisition frame interval. 2. The method according to claim 1, characterized in that acquiring an image at a droplet outlet comprises: storing multiple frames of images at the droplet outlet of the image acquisition device in the first queue in sequence; The areas of liquid droplets in the images are determined based on the adjacent frame images in the first queue, and the images with liquid droplets squeezed out are screened out and stored in the second queue, and the remaining images in the first queue are deleted. 3. The method according to claim 2, characterized in that the step of judging the droplet area in the image based on the adjacent frame images in the first queue and selecting the image with droplet extrusion comprises: Calculate the droplet area difference in adjacent frame images ,in , Respectively represent the two consecutive frames before and after, Indicates The droplet area in the frame image, Indicates The droplet area in the frame image; Determine the droplet area difference Is it greater than 0? When it is greater than 0, the corresponding two frames of images are determined to be images with droplet extrusion. 4. A liquid micro-flow measurement device, characterized in that it includes: a processor and a memory connected to the processor; wherein the memory stores instructions that can be executed by the processor, and the instructions are executed by the processor so that the processor executes the micro-flow measurement method suitable for droplet jitter as described in any one of claims 1-3. 5. A liquid micro-flow measurement system, comprising: A plurality of image acquisition devices, used for acquiring images at the droplet outlet from different directions; A computing device, used to execute the micro-flow measurement method applicable to droplet jitter as described in any one of claims 1-3.