Particle field holographic imaging device and image processing method based on dual-color narrow pulse LED illumination

Abstract

The present invention relates to a particle field holographic imaging device and an image processing method based on dual-color narrow pulse LED illumination, the device comprises: a dual-color narrow pulse LED illumination source, a collimating beam expansion lens, a telecentric magnifying lens, a color CMOS camera and a synchronous controller, wherein the dual-color narrow pulse LED illumination source emits a narrow pulse light beam according to a preset time interval, the narrow pulse light beam is converted into a parallel light beam after passing through the collimating beam expansion lens, the parallel light beam irradiates a sampling area to form an interference pattern, and the interference pattern is recorded by the color CMOS camera after passing through the telecentric magnifying lens; the synchronous controller connects the color CMOS camera and the dual-color narrow pulse LED illumination source to control the working sequence of the color CMOS camera and the dual-color narrow pulse LED illumination source. The present invention can obtain a color holographic image, and then realize the synchronous measurement of parameters such as the spatial position, particle size, and movement speed of particles, and obtain the phase state information of the particles.

Description

Technical Field

[0001] The present invention relates to the field of meteorological analysis technology, and is mainly used for on-site measurement of particles such as aerosols, fog droplets and cloud droplets in the atmosphere, and in particular to a particle field holographic imaging device and an image processing method based on dual-color narrow pulse LED illumination. Background Art

[0002] Digital holography is a non-contact measurement technology based on the theory of optical interference. It has many advantages such as fast real-time, non-invasive and full-field measurement. It is widely used in the field measurement of particle fields such as atmospheric aerosols and cloud particles. Existing measurement devices are mainly used to measure parameters such as particle number, particle size and spatial position, and cannot obtain particle velocity and phase information. In addition, in existing digital holographic devices, correlated light sources (lasers) are usually used for recording, and their good coherence makes the measurement optical path very simple. However, fully coherent light will react very sensitively to any tiny defects in the optical path, and strong coherence will also cause speckle noise and high-frequency fringe noise formed by multiple reflections in the components. These noise effects will have an extremely adverse effect on the quality of the hologram. In addition, lasers are expensive, large in size, and more complicated to operate.

[0003] In recent years, partially coherent light holography has gradually gained attention. Studies have shown that the introduction of LED light sources into digital holography can largely eliminate the speckle noise of laser light sources and the parasitic interference noise introduced by optical components, and the reproduction quality of the object light field, including amplitude and phase, has been greatly improved. On the other hand, compared with single-wavelength digital holography, dual-wavelength digital holography uses two wavelengths of light beams to produce two digital holograms at two different wavelengths, and then obtains the wrapped phase diagram of the corresponding wavelength through a numerical reconstruction algorithm, and obtains the wrapped phase difference between the two, and finally obtains the phase distribution of the equivalent wavelength. This phase information can restore the three-dimensional morphology of the object, which is helpful for object identification and classification. Compared with the phase reconstruction of a single-wavelength hologram, the phase obtained by multi-wavelength reconstruction can retain more detailed features of the object, so it has potential applications in particle phase recognition. With the improvement and development of color CCD and CMOS performance, the color crosstalk problem has also been proven to have little effect on the accuracy of the holographic measurement system, making it possible to extract multiple wavelength interference pattern information from a single color hologram. However, traditional dual-wavelength digital holographic microscopy usually requires two lasers with different wavelengths. This method is easily affected by factors such as poor light source stability, external environmental vibration, airflow disturbance, etc., which can generate noise, thereby affecting the accuracy of phase recovery and increasing the cost of the light source.

[0004] It can be seen that digital holography technology is currently mainly used to obtain conventional information such as particle size, shape and position. The potential particle velocity and particle phase measurement capabilities of this technology have not been well utilized and are far from meeting the measurement needs of related fields. Therefore, there is an urgent need for a particle field holographic imaging device and image processing method based on dual-color narrow pulse LED illumination. Summary of the invention

[0005] The purpose of the present invention is to provide a particle field holographic imaging device and an image processing method based on dual-color narrow pulse LED illumination, which can obtain a color holographic image, and then realize the synchronous measurement of parameters such as the spatial position, particle size, and movement speed of the particles, and obtain the phase information of the particles.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A particle field holographic imaging device based on dual-color narrow pulse LED illumination comprises: a dual-color narrow pulse LED illumination source, a collimating beam expansion lens, a telecentric magnifying lens, a color CMOS camera and a synchronous controller, wherein the dual-color narrow pulse LED illumination source emits a narrow pulse light beam at a preset time interval, the narrow pulse light beam is converted into a parallel light beam after passing through the collimating beam expansion lens, the parallel light beam irradiates a sampling area to form an interference pattern, and the interference pattern is recorded by the color CMOS camera after passing through the telecentric magnifying lens;

[0008] The synchronization controller connects the color CMOS camera and the dual-color narrow pulse LED illumination light source, and is used to control the working timing of the color CMOS camera and the dual-color narrow pulse LED illumination light source.

[0009] Optionally, the dual-color narrow pulse LED lighting source is a parabolic structure, one side of which is connected to the light source power supply circuit and the light source signal control circuit, and the other side is sealed with a baffle, and a pinhole is provided at the center of the baffle to improve the coherence of the light source.

[0010] Optionally, the dual-color narrow pulse LED lighting source includes a first LED chip, a second LED chip, and a focusing lens. The first LED chip and the second LED chip are used to emit monochromatic pulse light of different wavelengths, and the focusing lens is used to focus the monochromatic pulse light at the position of the pinhole.

[0011] To further achieve the above object, the present invention also provides an image processing method, which processes an image after acquiring the image through the particle field holographic imaging device based on dual-color narrow pulse LED illumination, comprising:

[0012] placing an imaging device in a cloud particle field;

[0013] When a particle passes through the sampling area, a trigger signal is sent to the color CMOS camera and the dual-color narrow pulse LED illumination light source by using a synchronous controller, the color CMOS camera starts shooting, and the first LED chip and the second LED chip sequentially emit monochromatic pulse light of different wavelengths according to a preset time interval;

[0014] The monochromatic pulse light passes through the pinhole and the collimating beam expanding lens in sequence to form a parallel light beam to illuminate the particles in the sampling area, and the color CMOS camera records the particles through two exposures within a single frame time to obtain a color holographic image;

[0015] Separating and reconstructing the color holographic image to obtain a reconstructed holographic image;

[0016] The motion information and phase information of the particles are acquired based on the reconstructed holographic image, and the processing of the color holographic image is completed.

[0017] Optionally, separating and reconstructing the color holographic image to obtain a reconstructed holographic image includes:

[0018] Using three-primary-color separation digital image processing technology, particle interference images corresponding to two wavelengths are separated from the color holographic image;

[0019] The particle interference image is reconstructed using an angular spectrum method to obtain the reconstructed holographic image.

[0020] Optionally, acquiring the motion information of the particle based on the reconstructed holographic image includes:

[0021] Obtaining the quantity, size, shape and spatial position information of the particles from the reconstructed holographic image;

[0022] The same particles are matched based on the size of the particles. After the matching is completed, the spatial displacement of the particles within the exposure time interval is obtained based on the spatial position of the particles, and the movement speed of the particles is calculated according to the exposure time and the spatial displacement.

[0023] Optionally, acquiring the phase information of the particle based on the reconstructed holographic image includes:

[0024] Obtaining the particle phase distribution corresponding to the two wavelengths from the reconstructed holographic image using a phase unwrapping method, synthesizing the phase distribution to obtain the object light wave phase of the equivalent wavelength;

[0025] The surface distribution of the particle is obtained based on the phase of the object light wave, and the phase state of the particle is obtained by combining the phase distribution and the surface distribution.

[0026] Optionally, the phase distribution is synthesized to obtain the object light wave phase of the equivalent wavelength by:

[0027]

[0028] In the formula, is the object light wave phase, λ1 and are the wavelength of the light beam emitted by the first LED chip and the object light phase recorded by the camera, λ2 and They are respectively the wavelength of the light beam emitted by the second LED chip and the object light phase recorded by the camera.

[0029] Optionally, a method for obtaining the surface distribution of the particle based on the object light wave phase is:

[0030]

[0031] Wherein, φ is the surface distribution of the particle, γ is the equivalent wavelength, γ=λ1λ2 / |λ1-λ2|, n1 is the refractive index distribution of the particle, and n0 is the refractive index distribution of the air medium.

[0032] The beneficial effects of the present invention are:

[0033] The present invention utilizes a two-color narrow pulse LED illumination light source in conjunction with camera timing control to realize single-frame double-exposure or single-frame multi-exposure holographic imaging of moving particles, and can realize synchronous measurement of parameters such as the spatial position, particle size, and movement speed of the particles through imaging; utilizes two-color hologram reconstruction to obtain the phase distribution and surface distribution of the particles, and obtains the phase information of the particles based on the difference in the phase distribution and surface distribution of the particles; not only does it overcome the shortcomings of the existing holographic measurement using laser as the illumination light source, but it also uses LED as the light source, which has low hardware cost, high control accuracy, and strong practicability, and is easy to promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 It is a schematic structural diagram of a particle field holographic imaging device based on dual-color narrow pulse LED illumination according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the structure of a dual-color narrow pulse LED lighting source according to an embodiment of the present invention;

[0037] Figure 3It is a working timing diagram of camera exposure and pulse light source according to an embodiment of the present invention;

[0038] Figure 4 A color hologram separation diagram of an embodiment of the present invention;

[0039] Figure 5 A flow chart of an image processing method according to an embodiment of the present invention;

[0040] Figure 6 The results of the wrapping phase and unwrapping phase of the spherical particles and irregular ice crystal particles according to the embodiment of the present invention are shown;

[0041] Figure 7 A comparison diagram of the wrapping phase and the unwrapping phase of the spherical particles and the irregular ice crystal particles according to an embodiment of the present invention;

[0042] Among them, 1-dual-color narrow pulse LED lighting source; 2-collimating beam expansion lens; 3-sampling area; 4-telecentric magnifying lens; 5-color CMOS camera; 6-synchronous controller; 7-first LED chip; 8-second LED chip; 9-pinhole; 10-focusing lens; 11-light source power supply circuit; 12-light source signal control circuit. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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.

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] This embodiment provides a particle field holographic imaging device based on dual-color narrow pulse LED illumination, such as Figure 1 As shown, it includes: a two-color narrow pulse LED lighting source 1, a collimating beam expanding lens 2, a telecentric magnifying lens 4, a color CMOS camera 5 and a synchronous controller 6.

[0046] A dual-color narrow pulse LED illumination light source 1 emits a narrow pulse beam at a preset time interval. The narrow pulse beam is converted into a parallel beam after passing through a collimating beam expander lens 2. The parallel beam irradiates a sampling area 3 to form an interference pattern. The interference pattern is recorded by a color CMOS camera 5 after passing through a telecentric magnifying lens 4.

[0047] The synchronous controller 6 connects the color CMOS camera 5 and the dual-color narrow pulse LED illumination light source 1 to control the working sequence of the color CMOS camera 5 and the dual-color narrow pulse LED illumination light source 1 .

[0048] like Figure 2 As shown, the two-color narrow pulse LED lighting source 1 is a parabolic structure with a highly reflective inner wall. One side is connected to the light source power supply circuit 11 and the light source signal control circuit 12, and one side is sealed with a stainless steel baffle. There is a pinhole 9 at the center of the stainless steel baffle. The size of the pinhole 9 directly affects the spatial coherence and energy of the point light source. In this embodiment, a pinhole 9 with a diameter of 100 μm is selected, which can be used to limit the light emitting area of ​​the light source and increase the spatial coherence of the light source.

[0049] The two-color narrow pulse LED lighting source 1 has two two-color LED chips inside, and the two-color LED chips emit any two wavelengths of high-power green light, red light and near-infrared light. Here, only the green light with a central wavelength of λ1=525nm and a power of 3W and the red light with a central wavelength of λ2=638nm and a power of 3W are used as examples for explanation. As an embodiment, the first LED chip 7 is a green light chip, and the second LED chip 8 is a red light chip, and the spectral width of both is less than 20nm.

[0050] The synchronous controller 6 connects the dual-color narrow pulse LED illumination light source 1 and the color CMOS camera 5. The synchronous controller 6 sends a trigger signal to the two at the same time, and the color CMOS camera 5 starts to work. The first LED chip 7 starts to illuminate after a delay of Δt1 at the camera triggering time. After a certain time interval Δt2, the second LED chip 8 starts to illuminate. The time interval needs to be set according to the maximum speed and particle size range of the measured particles, and the flash time of the monochromatic pulse light source is controlled within the camera exposure cycle. Figure 3 shown.

[0051] The green light beam and the red light beam successively pass through the pinhole 9 to form a point light source, and then are converted into parallel light beams after passing through the collimating beam expander lens 2. The parallel light beams irradiate the particles in the particle sampling area 3 to form scattered light (i.e., object light). The object light interferes with the unscattered light (i.e., reference light), passes through the telecentric magnifying lens 4, and is recorded by the color CMOS camera 5 to obtain a color holographic image.

[0052] In this embodiment, the color CMOS camera 5 used is a common industrial camera with a resolution of 5120×5120, a pixel size of 4.5 μm×4.5 μm, and a frame rate of 45 fps.

[0053] like Figure 5As shown, this embodiment also provides an image processing method, which processes the image after acquiring the image through the particle field holographic imaging device based on dual-color narrow pulse LED illumination, including:

[0054] placing an imaging device in a cloud particle field;

[0055] When a particle passes through the sampling area 3, a trigger signal is sent to the color CMOS camera 5 and the dual-color narrow pulse LED illumination light source 1 by using the synchronous controller 6, the color CMOS camera 5 starts shooting, and the first LED chip 7 and the second LED chip 8 sequentially emit monochromatic pulse light of different wavelengths according to a preset time interval;

[0056] The monochromatic pulse light passes through the pinhole 9 and the collimating beam expander lens 2 in sequence, forming a parallel light beam to illuminate the particles in the sampling area 3. The color CMOS camera 5 records the moving particles through two exposures within a single frame time to obtain a color holographic image;

[0057] Separating and reconstructing the color holographic image to obtain a reconstructed holographic image;

[0058] The motion information and phase information of the particles are obtained based on the reconstructed holographic image, and the processing of the color holographic image is completed.

[0059] The specific steps include:

[0060] S1. Place the device in a cloud particle field;

[0061] S2 uses the synchronization controller 6 to send a trigger signal to the color CMOS camera 5 and the dual-color narrow pulse LED illumination source 1;

[0062] S3. CMOS camera 5 starts shooting, and first LED chip 7 and second LED chip 8 start lighting up in sequence, emitting green light and red light in sequence;

[0063] S4. The green light and red light pulses emitted by the first LED chip 7 and the second LED chip 8 pass through the pinhole 9 and the collimating beam expander lens 2 in sequence to form parallel light beams to illuminate the moving particles in the sampling area 3, and the color CMOS camera 5 records the color holographic image after two exposures within a single frame time;

[0064] S5. Using the three-primary color separation digital image processing technology, the particle interference images corresponding to the two wavelengths of green light and red light are separated from a single color hologram, such as Figure 4 As shown;

[0065] The color holographic image is read in using the imread function in Matlab software to obtain three-channel images of red (R), green (G) and blue (B), and thus the monochromatic coaxial holograms corresponding to different wavelengths can be obtained. Considering that the CMOS does not respond to the spectral lines of the two wavelengths in the actual imaging process, the response spectrum of the CMOS is corrected and compensated by digital processing in the actual processing. Then, the single-channel holograms are numerically reconstructed using the angular spectrum diffraction formula (1), with a reconstruction distance interval of 50 μm, to obtain the reproduced images at different positions;

[0066] U z (x1,y1)=FFT -1 {FFT[I(x,y)R(x,y)]·H(f x ,f y )} (1)

[0067] In the formula, FFT -1 represents inverse Fourier transform, FFT represents Fourier transform, I(x,y) is the intensity distribution of the monochromatic hologram, R(x,y) is the complex amplitude of the reference light, H(f x ,f y ) is the transfer function of the optical system in the frequency domain, which can be expressed as:

[0068]

[0069] Among them, z is the propagation distance, j represents a complex number, k is the wave number, λ is the emission wavelength corresponding to the monochromatic LED light source, and f x and f y are the spatial frequencies in the x and y directions respectively.

[0070] S6. Reconstruct the two holograms with different wavelengths using the angular spectrum method, and obtain the number, size, shape and spatial position information of the particles from the focused reconstructed images;

[0071] After obtaining the reconstructed images at different positions, the grayscale gradient automatic focusing discrimination method is used to select the focused image corresponding to the corresponding particle from all the reconstructed images. The location of the focused image is the z-axis position of the corresponding particle. The implementation of the grayscale gradient automatic focusing discrimination method is to first calculate the average grayscale value of each particle in different reconstructed images, then calculate the average gradient value of the particle edge, and finally take the arithmetic average of the z-axis position where the minimum average grayscale value is located and the z-axis position where the maximum average gradient of the edge is located as the z-axis position of the particle; from the focused image of the particle, the sobel operator is used to detect the edge of the focused particle, extract the edge of the focused particle, and use the closed operation of expansion and corrosion combined in image morphology to reduce the problem of unclosed particle edges, binarize according to the particle edge information, and extract the particle's centroid position, effective radius and shape information from the binarized image.

[0072] S7. matching the same particles identified in the two images according to the gray value of the particles, obtaining the spatial displacement of the particles within the exposure time interval from the positions of the particles in the two holograms, and calculating the movement speed of the particles according to the exposure time and spatial displacement;

[0073] Since the green hologram and the red hologram image the particles in the sampling area at a certain time interval, by matching the particles identified in the two-color hologram, the spatial displacement of the same particle within the time interval can be obtained, and the three-dimensional movement speed of the particle can be obtained using the spatial displacement and time interval.

[0074] S8. using the phase unwrapping method to obtain the particle phase diagrams corresponding to the two sets of wavelengths respectively, synthesizing the object light wave wrapped phase distributions under the two sets of wavelengths, and obtaining the object light wave phase recorded at the equivalent wavelength;

[0075] In this embodiment, the phase of the object to be measured can be obtained by taking the real part and the imaginary part of the complex amplitude of the holographic reconstructed image object light wave:

[0076]

[0077] The range of formula (3) is limited to (-π, π], which will cause the phase values ​​beyond the range to be truncated, so it is necessary to perform phase unwrapping processing to obtain a continuous phase distribution. In this embodiment, a least squares unwrapping algorithm is used. The algorithm introduces discrete cosine transform (DCT) to solve the discrete Poisson equation, obtains a phase unwrapping solution in the sense of least squares, and finally obtains a truly continuous unwrapped phase. The mathematical model of the unweighted least squares phase unwrapping algorithm is:

[0078]

[0079] Where m and n represent the discrete coordinate positions, M and N are the discrete sizes of the two-dimensional phase, represents the unwrapped phase, Δ is the difference operator, and They represent the wrapped phase gradients of adjacent points in the x and y directions respectively. Formula (4) actually represents the search for an unwrapped phase distribution that is close to the true phase distribution under the condition that the unwrapped phase gradient and the wrapped phase gradient are consistent in the least squares sense.

[0080] In the discrete cosine transform domain (DCT), the exact solution for the unwrapped phase is:

[0081]

[0082] In the formula, Φ m,n and ρ m,n Phase and intermediate variables The solution in the DCT domain, ρ m,n It can be obtained by wrapping phase calculation. The inverse DCT transform of formula (4) can get the phase The solution is also the phase value of the successful unwrapping. The phase of the surface topography function h(x,y,z) of the object to be measured and any point on the surface of the object The relationship between can be calculated based on the optical path difference in the basic principles of optics. The formula is as follows:

[0083]

[0084] In the above formula, n1 is the refractive index distribution of the particle, and n0 is the refractive index distribution of the air medium. The particle phase can be identified from the surface morphology function distribution of the object to be tested.

[0085] The phase synthesis method is to subtract the phase distributions corresponding to the two recorded light waves to calculate the phase difference;

[0086]

[0087] In the formula, is the object light wave phase, λ1 and are the wavelength of the light beam emitted by the first LED chip and the object light phase recorded by the camera, λ2 and They are respectively the wavelength of the light beam emitted by the second LED chip and the object light phase recorded by the camera.

[0088] S9. Use the phase of the object light wave of equivalent wavelength to obtain the surface distribution of the particle, and use the phase distribution and surface distribution information to determine the phase state of the particle.

[0089] The calculation method of surface distribution is:

[0090]

[0091] Wherein, φ is the surface distribution of the particle, γ is the equivalent wavelength, γ=λ1λ2 / |λ1-λ2|, n1 is the refractive index distribution of the particle, and n0 is the refractive index distribution of the air medium.

[0092] like Figure 6 The first column is the simulated holographic images of spherical particles and irregular ice crystal particles. The simulation method of the simulated holographic images is to use Fresnel diffraction integral:

[0093]

[0094] In the formula, the simulated particle is located on the vertical plane (u, v), the recording plane is the (x, y) plane, t(u, v) is the complex amplitude transmission function of the object plane, d is the distance from the object plane to the recording plane, i is the imaginary unit, k = 2π / λ is the wave number, and λ is the wavelength of the light beam. In the numerical implementation process, the convolution method is used:

[0095] U(x,y,d)=IFFT{FFT[t(x,y)]·FFT[h(x,y)]} (10)

[0096] In the above formula, FFT[] represents fast Fourier transform, IFFT[] represents inverse fast Fourier transform, and h(x,y) is the impulse response function of the diffraction system, which is expressed as follows:

[0097]

[0098] The second column is the phase of the object to be measured obtained by taking the real part and the imaginary part of the complex amplitude of the object light wave of the holographic reconstructed image according to formula (3); the third column is the unwrapping phase of spherical particles and irregular particles obtained according to the mathematical model (4) of the unweighted least squares phase unwrapping algorithm.

[0099] Figure 7 To use Figure 6 The displayed phase distribution and unwrapping phase distribution data of spherical particles and irregular ice crystal particles, and the phase distribution and unwrapping phase size change diagram obtained by intercepting along the x=0 position. Among them, the horizontal axis is the pixel point in the y direction, and the vertical axis represents the phase size. It can be seen from the figure that the unwrapping phase distribution of spherical particles has a symmetrical structure, and the unwrapping of irregular ice crystal particles does not have a symmetrical structure. Therefore, the surface distribution of the particles can be obtained from the unwrapping phase distribution of spherical particles and irregular ice crystal particles, and the phase state information of the particles can be obtained based on the surface shape.

[0100] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A particle field holographic imaging device based on dual-color narrow pulse LED illumination, characterized in that: include: A two-color narrow pulse LED lighting source (1), a collimating beam expanding lens (2), a telecentric magnifying lens (4), a color CMOS camera (5) and a synchronous controller (6), wherein the two-color narrow pulse LED lighting source (1) emits a narrow pulse light beam at a preset time interval, the narrow pulse light beam is converted into a parallel light beam after passing through the collimating beam expanding lens (2), the parallel light beam irradiates a sampling area (3) to form an interference pattern, and the interference pattern is recorded by the color CMOS camera (5) after passing through the telecentric magnifying lens (4); The synchronous controller (6) connects the color CMOS camera (5) and the two-color narrow pulse LED illumination light source (1) to control the working sequence of the color CMOS camera (5) and the two-color narrow pulse LED illumination light source (1); The two-color narrow pulse LED lighting light source (1) is a parabolic structure, one side of which is connected to a light source power supply circuit (11) and a light source signal control circuit (12), and the other side is sealed with a baffle, and a pinhole (9) is provided at the center of the baffle to improve the coherence of the light source; The dual-color narrow pulse LED lighting source (1) comprises a first LED chip (7), a second LED chip (8), and a focusing lens (10); the first LED chip (7) and the second LED chip (8) are used to emit monochromatic pulse light of different wavelengths; and the focusing lens (10) is used to focus the monochromatic pulse light at the position of the pinhole (9).

2. An image processing method, which processes images after being acquired by the particle field holographic imaging device based on dual-color narrow pulse LED illumination as claimed in claim 1, characterized in that: include: placing an imaging device in a cloud particle field; When a particle passes through the sampling area (3), a synchronous controller (6) sends a trigger signal to the color CMOS camera (5) and the two-color narrow pulse LED illumination light source (1), the color CMOS camera (5) starts shooting, and the first LED chip (7) and the second LED chip (8) sequentially emit monochromatic pulse light of different wavelengths at preset time intervals; The monochromatic pulse light passes through a pinhole (9) and a collimating beam expander lens (2) in sequence to form a parallel light beam to illuminate the particles in the sampling area (3); the color CMOS camera (5) records the particles through two exposures within a single frame time to obtain a color holographic image; Separating and reconstructing the color holographic image to obtain a reconstructed holographic image; The motion information and phase information of the particles are acquired based on the reconstructed holographic image, and the processing of the color holographic image is completed.

3. The image processing method according to claim 2, characterized in that: Separating and reconstructing the color holographic image to obtain a reconstructed holographic image includes: Using three-primary-color separation digital image processing technology, particle interference images corresponding to two wavelengths are separated from the color holographic image; The particle interference image is reconstructed using an angular spectrum method to obtain the reconstructed holographic image.

4. The image processing method according to claim 2, characterized in that: Acquiring the motion information of the particle based on the reconstructed holographic image comprises: Obtaining the quantity, size, shape and spatial position information of the particles from the reconstructed holographic image; The same particles are matched based on the size of the particles. After the matching is completed, the spatial displacement of the particles within the exposure time interval is obtained based on the spatial position of the particles, and the movement speed of the particles is calculated according to the exposure time and the spatial displacement.

5. The image processing method according to claim 2, characterized in that: Acquiring the phase information of the particle based on the reconstructed holographic image comprises: Obtaining the particle phase distribution corresponding to the two wavelengths from the reconstructed holographic image using a phase unwrapping method, synthesizing the phase distribution to obtain the object light wave phase of the equivalent wavelength; The surface distribution of the particle is obtained based on the phase of the object light wave, and the phase state of the particle is obtained by combining the phase distribution and the surface distribution.

6. The image processing method according to claim 5, characterized in that: The method of synthesizing the phase distribution to obtain the object light wave phase of the equivalent wavelength is: In the formula, is the object light wave phase, λ1 and are the wavelength of the light beam emitted by the first LED chip and the object light phase recorded by the camera, λ2 and They are respectively the wavelength of the light beam emitted by the second LED chip and the object light phase recorded by the camera.

7. The image processing method according to claim 6, characterized in that: The method for obtaining the surface distribution of the particle based on the phase of the object light wave is: Wherein, φ is the surface distribution of the particle, γ is the equivalent wavelength, γ=λ1λ2 / |λ1-λ2|, n1 is the refractive index distribution of the particle, and n0 is the refractive index distribution of the air medium.

Images