Periodic liquid drop high-speed imaging device and method

Abstract

The invention discloses a device and a method for high-speed imaging of periodic liquid drops, and the device comprises a liquid drop generator which is used for generating a periodic stable liquid drop sequence; an imaging lens of the imaging unit images the image of the liquid drop to a common camera, the camera converts a received optical signal into an electric signal, and a computer processes the electric signal to obtain the image of the liquid drop and displays the image; the lighting unit comprises a stroboscopic light source and a light source controller, the stroboscopic light source is used for lighting the liquid drops, and the light source controller controls the stroboscopic light source; and the signal generator outputs a signal to synchronously control the stroboscopic frequency of the stroboscopic light source and the frame rate of the camera. Based on the mathematical relationship between the frame rate of the camera and the time interval of the two adjacent frames of images, the high-speed imaging of the periodic liquid drops is realized by adjusting the frame rate of the common camera, the problems of complex structure, high price, small field of view and low space and time resolution of the high-speed imaging device of the periodic liquid drops are solved, and the high-speed imaging device of the periodic liquid drops is suitable for high-speed imaging of the periodic liquid drops. The cost and the space of the periodic liquid drop high-speed imaging device are saved, and the image quality is improved.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and particularly to a device and method for high-speed imaging of periodic droplets. By combining the synchronous control technology of an ordinary camera and a stroboscopic light source, and utilizing the periodic characteristics of droplet motion, high-resolution imaging of high-speed moving droplets is achieved, which is particularly suitable for scenarios that require precise observation of the droplet formation process in fields such as semiconductor manufacturing, biomedicine, and micro-optics. Background Art

[0002] Uniform droplet ejection technology is an emerging technology that can precisely control droplet size, spacing, and frequency, and has a wide range of applications in fields such as semiconductors, biomedicine, and micro-optics. However, the implementation of this technology relies on multiple disciplines such as materials science, electronic technology, and mechanical engineering. The core difficulty lies in generating a stable periodic droplet sequence and observing it with high precision. The stability of the droplet flow is affected by various factors, such as the performance of piezoelectric elements, the design of the nozzle structure, and the control of disturbance waveforms, and a large number of experiments and precise imaging are required to optimize the parameters.

[0003] Traditional high-speed imaging technologies usually rely on high-speed cameras. Although such cameras can capture high-speed moving targets, they have disadvantages such as large volume, high cost, limited field of view, and low spatial resolution. The ultra-high frame rate of high-speed cameras is often achieved by increasing the pixel size or turning off some pixel units, resulting in a significant reduction in the imaging field of view and resolution under the same chip size and lens configuration. In addition, high-speed cameras are expensive, which limits their popular application in droplet observation.

[0004] In the prior art, the comparative document JP2024124481A discloses a droplet observation device and a droplet observation scheme, which are mainly used in an inkjet printing device. The controller controls the droplet generating device and the light source to take pictures of droplets at different times. However, its design purpose is for the droplet observation of inkjet printing devices and is not optimized for the imaging requirements of high-speed moving droplets. This technology does not involve the problem of high-speed imaging of periodic droplets, nor does it propose a specific solution to solve the problems of image blurring and trailing. Another patent document CN113978121A focuses on judging the atomization effect through droplet size parameters and also does not solve the imaging problem of high-speed periodic droplets. These technologies are difficult to meet the requirements of high-speed droplet imaging for time resolution and image clarity in practical applications.

[0005] Therefore, there is an urgent need for a low-cost, high-resolution technical solution suitable for high-speed imaging of periodic droplets to overcome the limitations of existing high-speed cameras and traditional imaging methods. Summary of the Invention

[0006] To overcome the deficiencies of the above-mentioned existing technologies, the present invention provides a device and method for high-speed imaging of periodic droplets. By combining the synchronous control of an ordinary camera and a stroboscopic light source and based on the periodic characteristics of droplet motion, it solves the problems of complex structure, high cost, small field of view, low spatial and temporal resolution of the high-speed imaging device for periodic droplets based on a high-speed camera, saves the cost and space of the high-speed imaging device for periodic droplets, and improves the image quality.

[0007] The principle of the present invention is that the droplet generator 101 generates a stable droplet sequence with a time period of T along a certain ejection direction. When the camera frame rate f satisfies 1 / f = n·T, that is, the camera takes a frame of image every nT time. Assuming the droplet 108 has moved for n periods and the movement time is nT, because the stable droplet sequence has periodicity, therefore, after nT, the droplet at the same position is the droplet 109. Although the droplet 108 has moved a distance of n droplet spacings, the entire droplet sequence appears relatively stationary in the image. At this time, it can be considered that the states of the droplet 108 and the droplet 109 are the same and they are the same droplet. When the camera frame rate f satisfies 1 / f ≠ n·T, because of the periodicity of the droplet sequence, it can still be considered that the droplet 108 and the droplet 109 are the same droplet, but at this time the positions of the droplet 108 and the droplet 109 do not coincide. That is, the droplet 109 is the state of the droplet 108 after moving for time t, and t is the time resolution of the imaging device. For a stable droplet sequence with a fixed frequency, different t values can be obtained by adjusting the frequency f, and high-speed imaging of droplets can be achieved by adjusting the t value.

[0008] The technical solution of the present invention is as follows;

[0009] A device for high-speed imaging of periodic droplets, characterized by comprising:

[0010] A droplet generator for generating a stable droplet sequence with a period of T;

[0011] An imaging unit, including an imaging lens, an ordinary camera, and a computer. The imaging lens focuses the droplet image onto the ordinary camera, and the computer is used to process and display the image;

[0012] A lighting unit, including a stroboscopic light source and a light source controller. The stroboscopic light source is used for droplet illumination, and the light source controller controls the stroboscopic parameters;

[0013] A signal generator for outputting a synchronous signal with a frequency of f to control the frame rate of the ordinary camera to be synchronized with the flash frequency of the stroboscopic light source.

[0014] Further, the frame rate of the ordinary camera is less than 100fps and supports the external trigger mode.

[0015] Further, the stroboscopic light source is an LED or a pulsed laser light source, and the single flash time is less than the single exposure time of the ordinary camera.

[0016] Further, the frequency f of the synchronization signal output by the signal generator and the droplet period T satisfy the relational expression: 1 / f = n·T + t, where n is the number of periods, 0 < t < T, and t is the time interval between two adjacent frames of images, that is, the time resolution of the imaging system.

[0017] The present invention also provides a method for high-speed imaging of periodic droplets, which is characterized by including the following steps:

[0018] S1: Generate a stable droplet sequence with a period of T through a droplet generator;

[0019] S2: Set the exposure parameters of the ordinary camera and enable the external trigger mode;

[0020] S3: Configure the flash parameters of the stroboscopic light source and enable the external trigger mode;

[0021] S4: Output a synchronization signal through the signal generator to synchronize the frame rate of the ordinary camera with the flash frequency of the stroboscopic light source;

[0022] S5: Adjust the signal frequency f so that 1 / f = n·T + t to achieve high-speed imaging of the droplet motion sequence, where t is the time resolution.

[0023] Further, the ejection direction of the droplet sequence is the gravity direction, the horizontal direction, or any spatial direction.

[0024] Further, the generation method of the droplet sequence is on-demand ejection or continuous ejection.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] The present invention adopts a droplet imaging device based on an ordinary camera, combines the mathematical relationship between the camera frame rate and the time interval between two adjacent frames of images, and obtains a method for high-speed images of a periodic droplet sequence by adjusting the frame rate of the camera, realizing high-speed imaging of the periodic droplet sequence, effectively reducing the volume of the imaging device based on a high-speed camera, and reducing its cost. The high-speed imaging device based on the periodic droplet high-speed imaging method proposed by the present invention has the advantages of low cost, small volume, large field of view, high spatial and time resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of Embodiment 1 of the device for high-speed imaging of periodic droplets of the present invention;

[0028] Figure 2 It is a schematic principle diagram of the method for high-speed imaging of periodic droplets of the present invention;

[0029] Figure 3 This is a flowchart of the periodic droplet high-speed imaging method of the present invention;

[0030] Figure 4 This is a schematic diagram of a droplet generator;

[0031] Figure 5 This is a relationship curve between the time interval of two adjacent frames of images and the frequency of the output signal of the signal generator;

[0032] Figure 6 This is a high-speed image of a sequence of ethylene glycol droplets captured by the droplet high-speed imaging device and method proposed based on the present invention. Detailed implementation manners

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] Embodiment 1. Periodic droplet high-speed imaging device based on an ordinary camera

[0035] Please refer to Figure 1 , Figure 1 This is a schematic structural diagram of Embodiment 1 of the device for periodic droplet high-speed imaging of the present invention. As shown in the figure, it includes:

[0036] A droplet generator 101, which is used to generate a periodic and stable sequence of droplets, and the period time T of the droplets is adjustable. The droplet generator 101 can operate in a vacuum environment 201 or an atmospheric environment 202, and the droplet material can be a metal such as tin 203, a liquid such as water 204, or a gas such as Xe 205, as Figure 4 shown.

[0037] An imaging unit, which includes an imaging lens 102, an ordinary camera 103, and a computer 107. Among them, the imaging lens 102 is used to focus the optical signal of the droplets onto the camera sensor. The ordinary camera 103, in this embodiment, an ordinary industrial camera with a frame rate lower than 100 fps is used, with a target surface size of 1 inch, a pixel size of 3.45 μm, a resolution of 4096×2160, and it supports an external trigger mode. The computer 107 is used to receive the electrical signal output by the camera, process and display the droplet image.

[0038] A lighting unit, which includes a stroboscopic light source 104 and a light source controller 105. Among them, the stroboscopic light source 104 in this embodiment uses an LED or a pulsed laser (such as a wavelength of 532 nm), and the single stroboscopic time is shorter than the camera exposure time (such as 10 ns). The light source controller 105 is used to adjust the stroboscopic frequency and the single flash time, and supports external trigger synchronization.

[0039] The synchronous control unit includes a signal generator 106 for outputting a synchronous signal with a frequency f to control the camera frame rate and the flash frequency of the stroboscopic light source, ensuring strict synchronization between the two.

[0040] This embodiment provides a high-speed imaging method based on the above device, and the specific process is as Figure 3 shown, including the following steps:

[0041] S1: Droplet sequence generation:

[0042] The droplet generator 101 generates a droplet sequence with a uniform size and a stable frequency and a period of T, such as metal tin droplets. The diameter of the tin droplets is 20 μm to 80 μm, the speed is 5 m / s to 100 m / s, and the droplet spacing is 100 μm to 1 mm. The movement direction of the droplets refers to the ejection direction of the droplets in the droplet generator 101. The movement of the droplets can be a movement 206 in the same direction as the gravity direction, a movement 207 in the horizontal direction, or a movement 208 in any ejection direction. The generation method of the stable droplet sequence can be on-demand jetting or continuous jetting based on Rayleigh jet breakup.

[0043] S2: Camera parameter setting: Turn on the ordinary camera 103, set the exposure time, and switch to the external trigger mode.

[0044] Specifically, the type of the camera 103 is an ordinary camera, its frame rate is less than 100 fps, the camera 103 has an external trigger function and can be controlled by the signal generator 106. At the same time, parameters such as the frame rate, exposure time, and gain of the camera 103 are adjustable. An imaging lens 102 is installed on the camera 103. The imaging lens 102 images the droplets onto the camera 103. The camera 103 converts the received optical signal into an electrical signal. The camera 103 is connected to the computer 107. The camera 103 transmits the signal to the computer 107. The computer 107 processes the signal to obtain the image of the droplets and displays it. Preferably, the target size of the camera 103 is 1", the pixel size is 3.45 μm, the resolution is 4096×2160, the maximum frame rate is 32 fps, and the exposure time is 1 μs to 10 s. The working distance of the imaging lens 102 is 160 mm, the object-side resolution is 6 μm, the maximum image-side field of view is 1.1", and the magnification is 0.9.

[0045] S3: Stroboscopic light source adjustment: Turn on the stroboscopic light source 104 and the light source controller 105, set the single flash time, and switch to the external trigger mode.

[0046] Specifically, the stroboscopic light source 104 is used for illuminating the droplets. The light source of the stroboscopic light source 104 can be an LED or a laser. The shape of the stroboscopic light source 104 can be circular, rectangular, annular, etc. The type of the stroboscopic light source 104 can be a collimated parallel light source or a focused linear light source, etc. The stroboscopic frequency and the time of each stroboscopic flash of the stroboscopic light source 104 are adjustable. The light source controller 105 has an external trigger function and can be controlled by the signal generator 106. The light source controller 105 controls the stroboscopic frequency and the time of each stroboscopic flash of the stroboscopic light source 104. Preferably, the light source of the stroboscopic light source 104 is a pulsed laser of 532 nm, the pulse frequency is 0 - 100 Hz, and the duration of each pulse is 10 ns.

[0047] S4: Synchronous signal control: The signal generator 106 outputs a synchronous signal with a frequency f to make the frame rate of the ordinary camera strictly match the stroboscopic frequency of the stroboscopic light source, ensuring that the ordinary camera is exposed only at the moment when the droplets are illuminated.

[0048] Specifically, the signal generator 106 is connected to the camera 103 and the light source controller 105. The signal generator 106 has a synchronous function and is used to output a signal with a frequency f to synchronously control the frame rate of the camera 103 and the stroboscopic frequency of the stroboscopic light source 104. The output waveform of the signal generator 106 can be a sine wave, a square wave, a triangular wave, etc. Preferably, the frequency range of the signal output by the signal generator 106 is 0 - 10 MHz.

[0049] S5: High-speed imaging: By adjusting the frequency f of the output signal of the signal generator, such that 1 / f - n·T = t, (0 < t < T, n = 0, 1, 2...), where n is the number of cycles and t is the time interval between two adjacent frames, i.e., the time resolution, droplet motion sequence images with different time resolutions can be obtained, as Figure 6 shown.

[0050] Specifically, the signal generator 106 can synchronously control the frame rate of the camera 103 and the stroboscopic frequency of the stroboscopic light source 104. Preferably, the droplet generator 101 generates a periodic ethylene glycol droplet sequence with a period time T = 20 μs. The target size of the camera 103 is 1", the pixel size is 3.45 μm, the maximum frame rate is 32 fps, the image field of view of the imaging lens 102 in the image space is 1.1", the magnification is 0.9, and the object space resolution is 6 μm. At this time, the diagonal size of the object space field of view of the droplet high-speed imaging device proposed by the present invention is 16 mm, and the spatial resolution of the imaging device is 6 μm. Figure 5It is a relationship curve between the time interval t between two adjacent frames of images and the frequency f of the signal output by the signal generator 106, i.e., the frame rate of the camera 103, when T = 20 μs. When f = 20.04 Hz, t = 0.1996 μs, it can be considered that the droplet high-speed imaging device takes a droplet image every 0.1996 μs, that is, the time resolution of the imaging device is 0.1996 μs, and the frame rate converted is about 5010020 fps. When f = 20.55 Hz, t = 1.8 μs, it can be considered that the droplet high-speed imaging device takes a droplet image every 1.8 μs, that is, the time resolution of the imaging device is 1.8 μs, and the frame rate converted is about 555555 fps. When f = 20.79 Hz, t = 0.0481 μs, it can be considered that the droplet high-speed imaging device takes a droplet image every 0.0481 μs, that is, the time resolution of the imaging device is 0.0481 μs, and the frame rate converted is about 20790020 fps. Figure 6 It is a high-speed image of an ethylene glycol droplet sequence with a period T = 20 μs taken by the droplet high-speed imaging device and method proposed based on the present invention. The frame rate f of the camera is 20.04 Hz. At this time, the time resolution t of the droplet high-speed imaging device is 0.1996 μs. In order to make the movement of the displayed droplets more obvious, 5 images are selected for display. Therefore, it is easy to understand that the time interval between two adjacent images displayed at this time is much larger than the time resolution t of the droplet high-speed imaging device. Figure 6 The display is for better illustrating this embodiment.

[0051] In this embodiment, the frame rate of the ordinary camera, the stroboscopic frequency of the stroboscopic light source, and the frequency of the signal output by the signal generator are the same. The single stroboscopic time of the stroboscopic light source is less than the single exposure time of the ordinary camera. The ordinary camera only takes images during the stroboscopic time of the stroboscopic light source. By controlling the stroboscopic time of the stroboscopic light source, the imaging time of the ordinary camera is controlled, achieving short-time imaging of the ordinary camera, that is, high-speed imaging, and solving the problems of overlapping blur and trailing phenomena that occur when the ordinary camera is used for high-speed droplet imaging. The specific application scenario of high-speed imaging of periodically moving droplets is realized by using an ordinary camera, solving the disadvantages of large size, heavy weight, and high price of high-speed cameras. Moreover, the ultra-high frame rate of high-speed cameras needs to be achieved by increasing the size of a single pixel and turning off pixel units. In the case of the same chip size and the same imaging lens, the field of view provided by the imaging device based on the high-speed camera is smaller and the spatial resolution is lower, thus limiting its comprehensive observation ability in droplet observation. In this embodiment, an ordinary camera is used to replace the high-speed camera, greatly reducing the equipment cost. Based on the mathematical relationship between the frame rate of the camera and the time interval between adjacent two frames of images, by adjusting the frame rate of the camera, high-speed imaging of a periodic droplet sequence is achieved, effectively reducing the volume of the high-speed imaging device based on the high-speed camera and lowering its cost. The droplet high-speed imaging device based on the periodic droplet high-speed imaging method proposed in the present invention has significant advantages such as low cost, small volume, large field of view, high spatial and temporal resolution, etc.

[0052] The parts not elaborated in detail in the present invention belong to the well-known technologies in the art.

[0053] As mentioned above, only some specific embodiments of the present invention are described, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. An apparatus for high-speed imaging of periodic droplets, characterized in that, Comprising: A droplet generator for generating a stable sequence of droplets with a period of T; An imaging unit including an imaging lens, an ordinary camera, and a computer, where the imaging lens focuses the droplet image onto the ordinary camera, and the computer is used to process and display the image; An illumination unit including a stroboscopic light source and a light source controller, where the stroboscopic light source is used for droplet illumination, and the light source controller controls the stroboscopic parameters; A signal generator for outputting a synchronization signal with a frequency of f to control the frame rate of the ordinary camera to be synchronized with the flash frequency of the stroboscopic light source.

2. The device for high-speed imaging of periodic droplets according to claim 1, characterized in that, The frame rate of the ordinary camera is less than 100 fps and supports the external trigger mode.

3. The device for high-speed imaging of periodic droplets according to claim 2, characterized in that, The stroboscopic light source is an LED or a pulsed laser light source, and the single flash time is less than the single exposure time of the ordinary camera.

4. The device for high-speed imaging of periodic droplets according to claim 1, characterized in that, The synchronization signal frequency f output by the signal generator and the droplet period T satisfy the relationship: 1 / f = n·T + t, where n is the number of periods, 0 < t < T, and t is the time interval between two adjacent frames, that is, the time resolution of the imaging system.

5. A method for high-speed imaging of periodic droplets, characterized in that Including the following steps: S1: Generate a stable sequence of droplets with a period of T through the droplet generator; S2: Set the exposure parameters of the ordinary camera and enable the external trigger mode; S3: Configure the flash parameters of the stroboscopic light source and enable the external trigger mode; S4: Output a synchronization signal through the signal generator to synchronize the frame rate of the ordinary camera with the flash frequency of the stroboscopic light source; S5: Adjust the signal frequency f to make 1 / f = n·T + t to achieve high-speed imaging of the droplet motion sequence, where t is the time resolution.

6. The method for high-speed imaging of periodic droplets according to claim 5, characterized in that, The ejection direction of the droplet sequence is the gravitational direction, the horizontal direction, or any spatial direction.

7. The method for high-speed imaging of periodic droplets according to claim 5, characterized in that The generation method of the droplet sequence is on-demand ejection or continuous ejection.

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