Low error particle counting system and method using reference imaging
The low-error particle counting system using reference imaging solves the counting error problem of traditional particle counters when multiple particles enter simultaneously by utilizing optical paths, gas paths, scattered light collection and signal processing systems. It achieves accurate particle counting and dark counting signal identification, and improves counting efficiency.
Patent Information
- Application Number
- CN202511183905.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-22
- Publication Date
- 2025-11-18
AI Technical Summary
Traditional particle counters generate counting errors when multiple particles enter the detection area simultaneously, and the dark counting signal leads to inaccurate measurements, making it impossible to effectively distinguish between particle signals and dark counting signals.
The low-error particle counting system using reference imaging achieves low-error counting by using a multi-element detector and imaging technology to identify and distinguish between particle signals and dark counting signals through an optical system, a gas path system, a scattered light collection system, and a signal processing system.
It effectively reduces counting errors, improves counting efficiency, and can accurately identify and count different particles that enter the photosensitive area at the same time, reducing the impact of dark counting.
Smart Images
Figure CN120971303A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the field of optical particle counters, in particular to a low-error particle counting system and method using reference imaging. BACKGROUND
[0002] Optical dust particle counters are widely used in various industrial fields such as semiconductors, pharmaceuticals, microelectronics, etc. that have high cleanliness requirements for experiments, production, etc. as the main instrument for clean room particle control and cleanliness measurement.
[0003] In the pharmaceutical field, optical dust particle counters are usually used to continuously monitor the cleanliness of the production environment in pharmaceutical production with strict regulatory requirements for particulate contaminants to prevent particles from harming drug quality and production processes.
[0004] In the high-precision semiconductor industry such as high-quality lithography machine production, semiconductor chip manufacturing, etc., the air cleanliness requirement is extremely high, and particles as low as 0.1 um need to be detected and controlled to avoid problems such as wafer defects and short circuits caused by nanoscale particle pollution. The accuracy of particle concentration measurement by the particle counter is crucial to normal industrial production, especially in the high-precision semiconductor industry.
[0005] Traditional particle counters usually assume that particles entering the detection area are monodisperse (single particles enter the detection area one by one) when multiple particles enter the detection area at the same time. The traditional particle counter counts multiple particles as one large particle due to the simultaneous detection of scattered light generated by multiple particles, resulting in counting errors. Dark counts caused by sensor receiving radiation energy due to high-energy particles from the universe or external radiation also cause counting errors. SUMMARY
[0006] The present application proposes a low-error particle counting system using reference imaging.
[0007] The technical solution for achieving the purpose of the present application is as follows: a low-error particle counting system using reference imaging, comprising: an optical system, an air path, a scattered light collection system, and a signal processing system, the optical system comprising a laser and a first lens, a second lens, an incident diaphragm, and a light trap arranged in sequence on the laser optical axis, the air path comprising an air inlet and an air outlet located on both sides of the laser emitting laser, the center lines of the air inlet and the air outlet being located on the same straight line and perpendicular to the beam waist position of the laser emitting laser, and the intersection area of the air path and the laser forming a photosensitive area;
[0008] The optical axis of the scattering light collection system is perpendicular to the optical axis of the light path system and the center of the gas path, the scattering light collection system comprises a spherical mirror, a third lens, a fourth lens and a multi-element detector, the spherical mirror is located on one side of the photosensitive area and the spherical center of the spherical mirror is located at the center of the photosensitive area, the convex surfaces of the third lens and the fourth lens are oppositely arranged to form an optical system and are arranged on the other side of the photosensitive area, the photosensitive surface of the multi-element detector and the photosensitive area are located on both sides of the optical system and satisfy the object-image conjugate relationship of geometric optics; the signal processing system is used for distinguishing particle sizes and counting particles according to the scattering light collected by the scattering light collection system.
[0009] The application further provides a low-error particle counting method using reference imaging, comprising the following steps:
[0010] Step 1: the light path system emits laser;
[0011] Step 2: the carrier fluid carrying the particles to be measured uniformly passes through the photosensitive area through the gas path;
[0012] Step 3: the scattering light collection system collects and simultaneously images the scattering light of the particles to be measured in multiple angle ranges to two or more detector elements of the multi-element detector, and two or more detector elements corresponding to each region in the photosensitive area are fixed;
[0013] Step 4: the signal output by the detector element of the multi-element detector is distinguished from the particle signal and the dark count signal by the signal processing system, and the number of particles of each particle size entering the photosensitive area at the same time is counted to realize low-error particle counting.
[0014] Compared with the prior art, the application has the following advantages: the application can distinguish the dark count signal and the particle signal, and can process and count different particles entering the photosensitive area at the same time, thereby improving the counting efficiency and effectively reducing the counting error.
[0015] The application will be further described in detail below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS
[0016] Figure 1 It is a schematic diagram of the principle of a low-error particle counting system using reference imaging.
[0017] Figure 2 It is a schematic diagram of the structure of a low-error particle counting system using reference imaging.
[0018] Figure 3 It is a schematic diagram of imaging on the multi-element detector when two particles enter different regions of the photosensitive area at the same time.
[0019] Figure 4 (a) is Figure 3Signal diagram of the output signal of the imaging detector element in the multi-element detector after signal processing system. Figure 4 The middle (b) is Figure 3 Signal diagram of the output signal of the corresponding detector element in the multi-element detector after signal processing system during dark count.
[0020] Figure 5 Signal processing system diagram of the particle counter for reference imaging low error count and signal-to-noise ratio improvement. DETAILED DESCRIPTION
[0021] Please refer to Figure 1 As shown, a low-error particle counting system using reference imaging includes an optical system, a gas path, a scattered light collection system, and a signal processing system. The optical system includes a laser (1), a first lens (2), a second lens (3), an incident diaphragm (4), and a light trap (6) arranged in sequence in the direction of the laser beam emitted by the laser (1), and the centers of each device are located on the laser optical axis.
[0022] The gas path includes an air inlet nozzle (7) and an air outlet nozzle (8) located on both sides of the laser (1) emitting laser, and the center lines of the air inlet nozzle (7) and the air outlet nozzle (8) are located on the same straight line and vertically pass through the waist position of the laser beam emitted by the laser (1). The intersection area of the gas path and the laser forms a photosensitive area (5).
[0023] The optical axis of the scattered light collection system is perpendicular to the optical axis of the optical system and the center line of the gas path, and the scattered light collection system includes a spherical mirror (9), a third lens (10), a fourth lens (11), and a multi-element detector (12). The spherical mirror (9) is located on one side of the photosensitive area (5) and the spherical center of the spherical mirror (9) is located at the center of the photosensitive area (5). The convex surfaces of the third lens (10) and the fourth lens (11) are arranged opposite to each other to form an optical system and are arranged on the other side of the photosensitive area. The photosensitive surface of the multi-element detector (12) is located on both sides of the optical system and satisfies the geometric optical object image conjugate relationship. The third lens (10) and the fourth lens (11) focus the scattered light radiation of a certain angle range on the upper hemisphere of the particle and the scattered light radiation collected by the spherical mirror to different detector elements in the multi-element detector (12).
[0024] The signal processing system is used to distinguish particle size and count particles according to the scattered light collected by the scattered light collection system.
[0025] In further embodiments, the laser is a semiconductor laser or a solid-state laser.
[0026] In further embodiments, the first lens and the second lens are aspherical mirrors and cylindrical mirrors, respectively.
[0027] In further embodiments, the multi-element detector (12) is a one-dimensional or two-dimensional detector array. In which each detector element in the detector array corresponds to a different region in the photosensitive area, and each detector element only receives scattered light from the corresponding photosensitive region. When a particle enters the photosensitive area, the lens group collects the scattered light within a 90-degree range of the upper hemisphere of the particle and images it onto one (and its adjacent) detector element of the detector array, and the hemispherical mirror collects the scattered light within a 90-degree range of the lower hemisphere of the particle and focuses it again through the lens group to image onto the symmetric (and its adjacent) element of the detector element of the upper hemisphere of the particle. The multiple detector elements that are imaged are referred to as an imaging group.
[0028] In further embodiments, the multi-element detector (12) is divided into different regions by the optical system, and each detector element in the multi-element detector (12) corresponds to a different region in the photosensitive area, and each detector element only receives scattered light from the corresponding photosensitive region.
[0029] In further embodiments, the third lens and the fourth lens are aspherical lenses.
[0030] In further embodiments, the spherical mirror is a hemispherical mirror or a semi-ellipsoidal mirror.
[0031] In further embodiments, the signal processing system 13 includes a preamplifier circuit, a subsequent amplification processing circuit, a comparison circuit, or a complex logic device.
[0032] A low-error particle counting method using reference imaging, the method comprising the following steps:
[0033] Step 1: the laser (1) emits laser light, which passes through the first lens (2), the second lens (3), the entrance pupil (4), the photosensitive area (5), and is absorbed by the optical trap (6);
[0034] Step 2: the carrier fluid carrying the particles to be measured is made to pass uniformly through the photosensitive area (5) through the gas path; the particles to be measured undergo light scattering when irradiated by the laser light in the photosensitive area (5);
[0035] Step 3: the spherical mirror and the optical system collect and simultaneously image the scattered light within multiple angular ranges of the particles to be measured onto two or more detector elements in the multi-element detector (12), and each region in the photosensitive area corresponds to two or more imaged detector elements (referred to as an imaging group);
[0036] Step 4: When multiple particles pass through different regions of the photosensitive area at the same time, the scattered light they produce is simultaneously imaged on different imaging groups of the multi-element detector (12), and the output signals of each imaging group are processed by the signal processing system to distinguish particle signals and dark count signals and count the number of particles of each size that entered the photosensitive area simultaneously to achieve low-error particle counting.
[0037] Specifically, when the multi-element detector (12) receives particle scattered light to produce electrical pulse signals, the signals are input to the signal processing system, and the signals of each detector element in the same imaging group at the same time are compared. When only a single detector element in the imaging group outputs a signal with an amplitude greater than the average amplitude of the signals of the other detector elements by a certain threshold range, the dark count signal is identified. When two or more detector elements in the imaging group output signals with amplitudes greater than a particle size threshold and the amplitudes of the signals of each detector element are distributed within a certain threshold range of the average signal amplitude, the particle signal is identified.
[0038] In a specific embodiment, when two particles enter two regions of the photosensitive area at the same time, the imaging on the detector array is shown schematically in Figure 3 The signals output by the detector elements of each imaging group are shown schematically in Figure 4 As shown in Figure 4 (a), because the output signal amplitudes of the two detector elements in imaging groups 3 and 5 differ by a threshold range, two particle signals are correctly identified, as shown in Figure 4 (b), the output signal amplitudes of the two detector elements in imaging group 2 differ by too much and exceed the range threshold, so they are identified as dark counts and are not included in the total number of particles.
[0039] In small particle detection, the amount of scattered light from small particles is very small, making it difficult to improve the signal-to-noise ratio of the output particle signals. In the present application, the output signals of the detector elements in an imaging group can also be combined and processed, i.e., the signals produced by the scattered light in each 90-degree range of the upper and lower hemispheres of a particle can be combined to improve the signal-to-noise ratio of the particle signals. As shown in Figure 5 The signal processing circuit schematic diagram is configured with an electrically implemented reference imaging low-error counting and signal-to-noise ratio improvement.
[0040] For example, the embodiments of the present application use a combination imaging system of a spherical mirror and a lens group in cooperation with a detector array to simultaneously detect multiple particles entering a photosensitive area. For example, in the embodiments of the present application, particle counting and dark counting are distinguished by comparing the signals of two symmetrically imaged detector elements.
[0041] In some embodiments, the carrier fluid carrying the particles to be measured is a liquid or a gas. In some embodiments, preferably, the carrier fluid is air, a macromolecular gas, a high-pressure gas, or ultrapure water. In some embodiments, preferably, the particles to be measured have a cross-sectional diameter greater than or equal to 50 nm.
[0042] In some embodiments, the half-sphere mirror collects the scattered light from a certain angular range of the lower half-sphere of the particle and images it through the above-mentioned lens to the detector elements or their adjacent detector elements on the detector which are symmetric about the center of the detector for the scattered light from the upper half-sphere of the particle.
Claims
1. A low error particle counting system using reference imaging, characterized by, It comprises: An optical path system, a gas path, a scattered light collection system, and a signal processing system. The optical path system comprises a laser (1) and a first lens (2), a second lens (3), an incident diaphragm (4), and a light trap (6) arranged in sequence on the laser light axis. The gas path comprises an air inlet nozzle (7) and an air outlet nozzle (8) located on both sides of the laser (1) emitting laser. The center lines of the air inlet nozzle (7) and the air outlet nozzle (8) are located on the same straight line and vertically pass through the beam waist position of the laser emitted by the laser (1). The intersection area of the gas path and the laser forms a photosensitive area (5). The optical axis of the scattered light collection system is perpendicular to the optical axis of the optical path system and the center of the gas path. The scattered light collection system comprises a spherical mirror (9), a third lens (10), a fourth lens (11), and a multi-element detector (12). The spherical mirror (9) is located on one side of the photosensitive area (5), and the spherical center of the spherical mirror (9) is located at the center of the photosensitive area (5). The convex surfaces of the third lens (10) and the fourth lens (11) are arranged oppositely to form an optical system and are arranged on the other side of the photosensitive area. The light-sensitive surface of the multi-element detector (12) is located on both sides of the optical system and satisfies the geometric optical object-image conjugate relationship. The signal processing system is used to distinguish particle sizes and count particles according to the scattered light collected by the scattered light collection system.
2. A low error particle counting system using reference imaging according to claim 1, wherein, The laser (1) is a semiconductor laser or a solid-state laser.
3. A low error particle counting system using reference imaging of claim 1, wherein, The first lens (2) and the second lens (3) are aspherical mirrors and cylindrical lenses, respectively.
4. A low error particle counting system using reference imaging of claim 1, wherein, The multi-element detector (12) is a one-dimensional or two-dimensional detector array.
5. A low error particle counting system using reference imaging of claim 1, wherein, Each detector element in the multi-element detector (12) corresponds to a different area in the photosensitive area, and each detector element only receives scattered light from the corresponding photosensitive area.
6. A low error particle counting system using reference imaging of claim 1, wherein, The third lens (10) and the fourth lens (11) are aspherical mirrors.
7. A low error particle counting system using reference imaging of claim 1, wherein, The spherical mirror (9) is a hemispherical mirror or a semi-ellipsoidal mirror.
8. The method of low error particle counting system using reference imaging according to any one of claims 1 to 7, characterized in that, It comprises the following steps: Step 1: The optical path system emits laser; Step 2: Make the carrier fluid carrying the particles to be measured pass through the photosensitive area (5) at a constant speed through the gas path; Step 3: The scattered light collection system collects and simultaneously images the scattered light of the particles to be measured in multiple angular ranges to two or more detector elements in the multi-element detector (12), and the two or more detector elements corresponding to each region in the photosensitive area are fixed; Step 4: The detector element output signal of the multi-element detector (12) is processed by the signal processing system to distinguish particle signals and dark count signals and count particle signals to obtain the number of particles of each particle size entering the photosensitive area simultaneously to realize low-error particle counting.