A device and method for detecting small particles in a liquid

Abstract

The application discloses a device for detecting micro-particles in liquid, which comprises a flow cell, a laser, a scattered light collecting device, a photodetector, a Bragg grating and a first fiber coupler. The scattered light collected by the scattered light collecting device is sent to the fiber Bragg grating through the first fiber coupler. The reflected light of the fiber Bragg grating after receiving the scattered light is sent to the photodetector through the first fiber coupler. By the device, most of the scattered light generated by the liquid can be eliminated, the interference of the scattered light of the liquid on the scattered light signal generated by the particles is reduced, the scattered light signal captured by the photodetector is mainly the light signal generated by the particles, the signal-to-noise ratio of the whole detection device is improved, and the detection capacity of the detection device for detecting micro-particles is enhanced, so that particles with smaller particle size can be detected.

Description

Technical Field

[0001] The present invention relates to the field of equipment for detecting particles in liquid, and in particular to a device and method for detecting tiny particles in liquid. Background Art

[0002] Liquid particle counters are primarily used to detect tiny particle contaminants in liquids. They are crucial in semiconductor process control, used to monitor the cleanliness of ultrapure water and chemical reagents. Light scattering is currently the primary detection method used by liquid particle counters.

[0003] When incident light strikes particles, they interact with the light and generate scattered light. The amount of scattered light is related to the size of the particles. Therefore, the size of the particles can be measured based on the size of the scattered light signal generated by the particles, and the number of particles can be counted.

[0004] Because the tiny particles in the liquid being measured are extremely small, typically less than 1 micron in diameter, the scattered light they generate is also very weak. For liquid particle counters, when incident light strikes the tiny particles, it also strikes the liquid itself, which generates scattered light. This scattered light interferes with the scattered light signal generated by the particles, severely limiting the system's detection capabilities. Summary of the Invention

[0005] The object of the present invention is to provide a device and method for detecting tiny particles in liquid that can remove the interference of the liquid on the detection result.

[0006] To achieve the above-mentioned objectives, the present invention adopts a technical solution: a device for detecting tiny particles in liquid, comprising a flow cell having a liquid channel therein for liquid to pass through, a laser for generating laser light directed toward the liquid channel, a scattered light collection device for collecting scattered light scattered by the flow cell after being irradiated by the laser beam, and a photodetector. The detection device also includes a fiber Bragg grating (FBG) and a first fiber coupler. The reflection wavelength of the FBG is the same as the wavelength emitted by the laser. The FBG, the scattered light collection device, and the photodetector are connected via the first fiber coupler. The scattered light collected by the scattered light collection device is transmitted to the FBG via the first fiber coupler. The light reflected by the FBG after receiving the scattered light is transmitted to the photodetector via the first fiber coupler.

[0007] Preferably, the circulation pool is a cuboid made of a transparent material, and the liquid channel is a through hole provided in the circulation pool along the length direction thereof.

[0008] Further preferably, the liquid channel is a circular hole with a diameter of 0.5-2 mm.

[0009] Further preferably, the laser beam is emitted perpendicularly to the liquid channel into the center of the liquid channel.

[0010] Further preferably, the scattered light collecting device comprises a collecting lens and an optical fiber, and the collecting lens collects the scattered optical fiber to the end of the optical fiber and is collected by the optical fiber.

[0011] Further preferably, the converging lens is glued to the surface of the circulation pool, and the center of the fluid channel of the circulation pool is located at the object plane position of the converging lens.

[0012] Further preferably, the scattered light collecting device is provided with two groups, and the detection device also includes a second optical fiber coupler respectively connecting the two groups of the scattered light collecting devices and the first optical fiber coupler. The scattered light received by the two groups of the scattered light collecting devices is combined through the second optical fiber coupler and then sent into the first optical fiber coupler.

[0013] Further preferably, the two groups of scattered light collecting devices respectively collect light scattered from two opposite sides of the flow cell.

[0014] Preferably, the detection device further comprises a light trap for absorbing light, and the light trap is located in the emission direction of the laser beam after passing through the circulation cell.

[0015] A method for detecting tiny particles in a liquid comprises irradiating the liquid with a laser and collecting scattered light. The collected scattered light is reflected by a fiber Bragg grating having the same reflection wavelength as the laser wavelength, and then a photodetector is used to analyze the reflected light from the fiber Bragg grating. The number and diameter of the particles are calculated based on the reflected light received by the photodetector.

[0016] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0017] Monochromatic light with a wavelength of λ emitted by a laser converges at the detection area of ​​the flow cell, forming a light spot. As the liquid and particles within the flow cell pass through the detection area, they are illuminated by the illumination light and generate scattered light. According to light scattering theory, the wavelength of the scattered light generated by the particles is λ. The scattered light generated by the liquid is divided into three components: the first component has a wavelength of λ, the second component has a wavelength of λ1 (λ1 = λ + Δλ), and the third component has a wavelength of λ2 (λ2 = λ - Δλ). The scattered light is collected by a scattered light collection device and then transmitted through a first fiber coupler to a fiber Bragg grating (FBG), which has a reflection wavelength of λ. Therefore, of the scattered light transmitted into the FBG, only the light with a wavelength of λ is reflected and transmitted through the first fiber coupler to a photodetector, where it is captured. The scattered light with wavelengths λ1 and λ2 generated by the liquid passes through the FBG and is then received by a subsequent optical trap.

[0018] This device eliminates most of the scattered light generated by the liquid, reducing the interference of the liquid scattered light on the scattered light signal generated by the particles. This ensures that the scattered light signal captured by the photodetector is primarily the light signal generated by the particles. This improves the signal-to-noise ratio of the entire detection device and enhances the detection capability of the device for detecting tiny particles, allowing the detection of particles of even smaller sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Attachment Figure 1 Schematic diagram of the principle of the detection device;

[0020] Attachment Figure 2 Schematic side view of the flow cell.

[0021] In the above figures: 1. Laser; 2. Light source focusing lens; 3. Circulation cell; 31. Liquid channel; 4. Photodetector; 5. Fiber Bragg grating; 6. First fiber coupler; 7. Second fiber coupler; 8. Light trap. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to the embodiments shown in the accompanying drawings:

[0023] See attached Figure 1As shown, a device for detecting tiny particles in liquid comprises a flow cell 3 having a liquid channel 31 therein for liquid passage, a laser 1 for generating laser light, a light source focusing lens 2 for focusing light emitted by the laser 1 into the liquid channel 31, a scattered light collection device for collecting scattered light from the flow cell 3 after being irradiated by the laser beam, a photodetector 4, a fiber Bragg grating 5, and a first fiber coupler 6. Furthermore, the device comprises a light-absorbing optical trap 10, located in the direction of exit of the laser beam after passing through the flow cell 3. The reflection wavelength of the fiber Bragg grating 5 is the same as the wavelength emitted by the laser 1. The fiber Bragg grating 5, the scattered light collection device, and the photodetector 4 are connected via the first fiber coupler 6. The scattered light collected by the scattered light collection device is transmitted to the fiber Bragg grating 5 via the first fiber coupler 6. The reflected light from the fiber Bragg grating 5 is then transmitted to the photodetector 4 via the first fiber coupler 6. The scattered light that passes through the fiber Bragg grating 5 is absorbed by another optical trap (not shown).

[0024] In this embodiment, monochromatic light with a wavelength of λ emitted by laser 1 converges at the detection area of ​​flow cell 3, forming a detection spot. As the liquid and particles in flow cell 3 pass through the detection area, they are illuminated by the illumination light, generating scattered light. According to light scattering theory, the wavelength of the scattered light generated by the particles is λ. The scattered light generated by the liquid is divided into three components: the first component has a wavelength of λ, the second component has a wavelength of λ1 (λ1 = λ + Δλ), and the third component has a wavelength of λ2 (λ2 = λ - Δλ). The scattered light is collected by a scattered light collection device and then transmitted through a first fiber coupler 6 to a fiber Bragg grating 5, which has a reflection wavelength of λ. Therefore, of the scattered light transmitted into the fiber Bragg grating 5, only the light with a wavelength of λ is reflected and transmitted through the first fiber coupler 6 to the photodetector 4, where it is captured. The scattered light with wavelengths λ1 and λ2 generated by the liquid passes through the fiber Bragg grating and is captured by subsequent optical traps. Finally, the number and diameter of the particles are calculated using the reflected light received by the photodetector 4. The Bragg grating filters scattered light with wavelengths λ1 and λ2, thereby improving the signal-to-noise ratio of the device of this embodiment and enhancing the detection capability of the detection device for detecting tiny particles, thereby enabling the detection of particles with smaller diameters.

[0025] See attached Figure 1 、 2As shown, in this embodiment, to facilitate the acquisition of scattered light, the flow cell 3 is a rectangular parallelepiped made of a transparent material, and the liquid channel 31 is a through hole provided along the length of the flow cell 3. Specifically, the liquid channel 31 is a circular hole with a diameter of 0.5-2 mm. The laser beam is incident perpendicularly on one surface of the flow cell 3 and perpendicular to the liquid channel 31, entering the center of the liquid channel 31, forming a detection light spot in the liquid channel 31.

[0026] In this embodiment, the scattered light collecting device includes a scattered light collecting lens 8 and an optical fiber 9. The scattered light collecting lens 8 collects the scattered light at the end of the optical fiber 9, where it is collected by the optical fiber 9. Specifically, the scattered light collecting lens 4 is glued to the surface of the flow cell 3, and the center of the fluid channel of the flow cell 3 is located at the object plane of the collecting lens, thereby facilitating the installation of the scattered light collecting lens 4.

[0027] See attached Figure 1 As shown, in this embodiment, to improve the efficiency of scattered light collection, two sets of scattered light collection devices are provided, each of which collects light scattered from two opposite sides of the flow cell 3. The detection device also includes a second fiber optic coupler 7 that connects the two sets of scattered light collection devices to the first fiber optic coupler 6. The scattered light received by the two sets of scattered light collection devices is combined by the second fiber optic coupler 7 and then transmitted to the first fiber optic coupler 6.

[0028] As a result, this device eliminates most of the scattered light generated by the liquid, reducing the interference of the liquid scattered light on the scattered light signal generated by the particles. As a result, the scattered light signal captured by the photodetector 4 is primarily the light signal generated by the particles. This improves the signal-to-noise ratio of the entire detection device and enhances the detection capability of the detection device for tiny particles, allowing the detection of particles of even smaller sizes.

[0029] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A device for detecting microparticles in liquid, comprising a flow cell having a liquid channel therein, a laser for generating laser light directed toward the liquid channel, a scattered light collecting device for collecting light scattered by the flow cell after being irradiated by the laser beam, and a photodetector, characterized in that: The detection device further includes a fiber Bragg grating (FBG) and a first fiber coupler. The reflection wavelength of the fiber Bragg grating is the same as the wavelength emitted by the laser. The fiber Bragg grating, the scattered light collecting device, and the photodetector are connected via the first fiber coupler. The scattered light collected by the scattered light collecting device is sent to the fiber Bragg grating via the first fiber coupler. The reflected light from the fiber Bragg grating after receiving the scattered light is sent to the photodetector via the first fiber coupler. The flow cell is a rectangular parallelepiped made of a transparent material, and the liquid channel is a through hole provided in the flow cell along its length direction. The liquid channel is a circular hole with a diameter of 0.5-2 mm; The scattered light collecting device includes a focusing lens and an optical fiber. The focusing lens focuses the scattered optical fiber to the end of the optical fiber and is collected by the optical fiber. The focusing lens is glued to the surface of the flow cell, and the center of the flow cell fluid channel is located at the object plane position of the focusing lens. The method for detecting tiny particles in liquid using the detection device includes: irradiating the liquid with a laser and collecting scattered light, the collected scattered light is reflected by a fiber Bragg grating having a reflection wavelength identical to the laser wavelength, and then analyzing the reflected light of the fiber Bragg grating using a photodetector, and calculating the number and diameter of the particles using the reflected light received by the photodetector.

2. The device for detecting tiny particles in liquid according to claim 1, characterized in that: The laser beam is incident perpendicularly to the liquid channel and enters the center of the liquid channel.

3. The device for detecting tiny particles in liquid according to claim 1, characterized in that: The scattered light collecting devices are provided with two groups, and the detection device further includes a second optical fiber coupler respectively connecting the two groups of scattered light collecting devices and the first optical fiber coupler. The scattered light received by the two groups of scattered light collecting devices is combined by the second optical fiber coupler and then sent to the first optical fiber coupler.

4. The device for detecting tiny particles in liquid according to claim 3, characterized in that: The two groups of scattered light collecting devices respectively collect light scattered from two opposite sides of the flow cell.

5. The device for detecting tiny particles in liquid according to claim 1, characterized in that: The detection device further comprises a light trap for absorbing light, and the light trap is located in the emission direction of the laser beam after the laser beam passes through the circulation cell.

Images