Large depth of field microscope based on bessel spot projection, imaging method thereof and shooting encryption method

Abstract

The application provides a large-depth-of-field microscope based on Bessel spot projection, an imaging method thereof and a shooting encryption method thereof, and relates to the technical field of imaging. The application reconstructs a full-focus image by using the unique non-diffraction characteristic of the Bessel beam. Without mechanical scanning or frequent focusing, a clear image of the whole field can be obtained through a single acquisition process and cooperation of calculation reconstruction, and the application is particularly suitable for detection in a vibrating environment or real-time observation of fast-moving microscopic objects. In addition, the application combines a secret key, a HASH function and a spatial light modulator, and uses the generated Bessel speckle as an encryption key. In the projection process, a random phase determined by the secret key is introduced, so that the original image collected is physically blurred and appears as a speckle pattern. It is ensured that only a legitimate receiver holding a correct secret key can restore the projected pattern through simulation, and then a clear image is restored by using a frequency domain deconvolution algorithm, so that the security of sensitive data such as medical data is improved.

Description

Technical Field

[0001] This invention relates to the field of imaging technology, and in particular to a large depth-of-field microscope based on Bessel spot projection, its imaging method, and its image encryption method. Background Technology

[0002] Optical microscopes play a crucial role in biomedical detection, industrial microscopic inspection, and three-dimensional topography measurement. However, traditional optical microscopic imaging systems are limited by the optical diffraction limit, and generally suffer from the physical drawback of insufficient depth of field.

[0003] In existing technologies, traditional microscopes can only achieve clear imaging near the focal plane. For samples with significant surface undulations and three-dimensional structures (such as thick biological tissues, microstructured devices, or rough metal fractures), severe blurring occurs in the out-of-focus areas, leading to loss of detail. To obtain a clear image across the entire field, existing technologies typically require mechanical scanning or frequent manual / automatic focusing (i.e., Z-axis stacking imaging), involving capturing multiple images at different heights and then fusing them in post-processing. This approach has significant drawbacks:

[0004] Slow imaging speed: Due to the limited speed of mechanical structure movement, it is difficult to capture the dynamic process of microscopic objects.

[0005] High operational complexity: requires precise Z-axis movement control, increasing system maintenance and operating costs.

[0006] Insufficient data security: Especially in the field of medical microscopic imaging, image acquisition and encryption are usually separate. The original images are at risk of being illegally intercepted during storage and transmission. There is a lack of an effective means to achieve encryption from the physical acquisition level.

[0007] A large depth-of-field microscope based on Bessel beam projection is an innovative imaging system that breaks through the traditional optical diffraction limit. This technology utilizes the unique non-diffraction properties of the Bessel beam, combining structured light projection with computational imaging algorithms to successfully solve the pain points of traditional microscopes, such as short depth of field and the need for frequent focusing. Its core advantage lies in the fact that regardless of whether the object being measured is within the physical focal plane of the microscope, as long as the object is within the coverage area (diffraction-free region) of the Bessel beam, the system can reconstruct a fully clear, high-resolution image through algorithms. Summary of the Invention

[0008] Purpose of the invention: To provide a large depth-of-field microscope based on Bessel spot projection, its imaging method and its image encryption method, so as to solve the above-mentioned problems existing in the prior art.

[0009] To achieve the above objectives, a first aspect of the present invention provides a large depth-of-field microscope based on Bessel spot projection, comprising: A projection system for generating a Bessel beam with non-diffraction characteristics and using the Bessel beam to project a Bessel pattern onto the surface of the object being measured. An imaging system is used to acquire images of the object under test, including a first image without the application of the Bezier pattern projection. and the second image when the Bezier pattern projection is applied. ; Calculation module, used to calculate based on the first image Second image And perform frequency domain deconvolution operation on the known Bezier pattern t to reconstruct a fully focused, clear image f of the object under test.

[0010] Preferably, the projection system includes: A light source used to emit a coherent beam of light; A wavefront modulation device is used to phase modulate the coherent beam to generate a modulated beam carrying a composite phase. An objective lens is used to project the modulated beam onto the surface of the object being measured.

[0011] Preferably, the wavefront modulation device is a spatial light modulator loaded with a composite phase map, the composite phase map including an axial-cone phase for generating a Bessel beam. and random phase used to introduce random interference .

[0012] Based on the large depth-of-field microscope disclosed in the first aspect, the second aspect of the present invention discloses its imaging method, comprising the following steps: Step S1: Generate a Bessel beam and modulate it into a preset Bessel pattern t, then project it onto the surface of the object under test, ensuring that the object under test is within the non-diffraction range of the Bessel beam; Step S2: Acquire two original images of the object under test using the imaging system, namely the first image without projection. And the second image with projection ; Step S3: Transfer the first image The second image and the Bezier pattern t input calculation module; Step S4: The calculation module executes the frequency domain reconstruction algorithm and outputs a fully focused, clear image f.

[0013] Preferably, the frequency domain reconstruction algorithm in step S4 specifically includes: processing the first image... Second image Performing Fourier transforms on the Bessel pattern t and the corresponding frequency domain distribution yields the corresponding frequency domain distribution. , and ; A system of equations is constructed based on the complete frequency domain distribution, and the frequency domain solution of the clear image is obtained by solving it. ; For the frequency domain solution Perform inverse Fourier transform to obtain a fully focused, sharp image. .

[0014] Preferably, the frequency domain solution Solve using the following formula: .

[0015] Preferably, the object under test is located outside the physical focal plane of the imaging system, and the first image and the second image All images were out of focus and blurred during the acquisition process.

[0016] A third aspect of the present invention discloses a method for image encryption during imaging using the large depth-of-field microscope. Specifically, the generation process of the Bezier pattern t in step S1 includes: Obtain the initial key and use a hash function to convert the key into a binary sequence; Determine the random phase based on the numerical mapping result generated from the binary sequence. ; The random phase Phase with preset shaft cone Superposition yields a composite phase map. ; Using the composite phase diagram A spatial light modulator is modulated to generate a Bessel speckle pattern as an encryption pattern, referred to as the Bessel pattern t.

[0017] Preferably, the random phase The determination rule is as follows: based on whether the HASH function value is 0 or 1, the corresponding random phase is determined to be 0 or π respectively.

[0018] Preferably, in step S4, the receiver must input the initial key that is consistent with the encryption end in order to reconstruct the Bezier pattern t consistent with the projection through simulation calculation; otherwise, the fully focused clear image f cannot be recovered.

[0019] This invention achieves a dual improvement in imaging performance and security by combining the physical properties of Bessel beams with frequency domain computational imaging algorithms. Specific beneficial effects are as follows: (1) This invention utilizes the unique non-diffraction characteristics of the Bessel beam, which maintains the shape and size of the light spot during propagation and has a very large depth of focus. As long as the object under test is within the non-diffraction range of the Bessel beam, even if the surface undulations of the object exceed the physical depth of field of the microscope objective, the system can still capture a clear and stable modulation signal, thereby reconstructing a fully focused image.

[0020] (2) This invention does not require complex Z-axis mechanical scanning or frequent focusing. It can obtain a clear image of the entire field through a single acquisition process (taking two photos, one with projection and one without projection) and calculation reconstruction. Since the mechanical movement is eliminated, the imaging speed is greatly improved, making it particularly suitable for detection in vibration environments or real-time observation of fast-moving microscopic objects.

[0021] (3) This invention combines a key, a hash function, and a spatial light modulator (SLM) to generate a Bessel speckle pattern that is not only a modulation signal for imaging but also an encryption key. By introducing a random phase determined by the key during the projection process, the acquired original image is physically represented as a blurred speckle pattern. This mechanism ensures that only a legitimate recipient with the correct key can reconstruct the projected pattern through simulation and then use a frequency domain deconvolution algorithm to recover a clear image, greatly improving the security of sensitive data such as medical data.

[0022] (4) The computational imaging model of this invention, based on solving equations in the frequency domain, can effectively eliminate defocus blur and accurately restore the texture and details of the object surface. Compared with traditional microscopes, this invention produces more uniform imaging quality and higher detail reproduction when processing three-dimensional rough surfaces or thick tissue samples. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the large depth-of-field microscope system based on Bezier spot projection in the embodiment.

[0024] Figure 2 This is a schematic diagram of the medical microscopic image acquisition encryption system in the embodiment.

[0025] The meanings of the labels in the figures are as follows: laser 100, collimating lens 200, conical lens 300, microscope system 400, camera 401, field lens 402, objective lens 403, polarizer 500, spatial light modulator 600. Detailed Implementation

[0026] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0027] This invention provides a large depth-of-field microscope based on Bessel beam projection, its imaging method, and an integrated method for image acquisition and encryption. It aims to solve the problems of limited depth of field and frequent focusing required in traditional microscopic imaging systems by combining the non-diffraction characteristics of Bessel beams with computational imaging algorithms, and on this basis, achieve a deep fusion of image acquisition and encryption. To enable those skilled in the art to better understand the invention, the specific embodiments are described in detail below.

[0028] Example 1 This embodiment provides a large depth-of-field microscope based on Bessel spot projection. The microscope system 400 consists of a projection system, an imaging system, and a computing module. The projection system generates a Bessel beam with non-diffraction characteristics and uses the Bessel beam to form a specific Bessel pattern projection on the surface of the object under test. The imaging system is responsible for image acquisition; it is configured to capture and acquire original images of the object under test under different projection states, specifically including a first image without Bessel pattern projection. and the second image when applying Bezier pattern projection. In this process, the computing module, as the logical hub of the entire system, pre-stores or can generate known Bézier patterns in real time. And based on the first image acquired Second image Frequency domain deconvolution is performed to reconstruct a fully focused, sharp image of the object under test at the algorithm level. .

[0029] Furthermore, the projection system begins with a high-quality light source configured to emit a coherent beam, typically a laser source with high spatial coherence. The initial output beam is usually a Gaussian beam with high central intensity and weaker edges. To ensure this coherent beam is compatible with subsequent modulation stages, a beam expander and collimator is incorporated into the optical path to amplify and collimate the narrow beam, ensuring it completely covers the effective aperture of the subsequent modulation device. Next, the collimated beam enters the wavefront modulation device, crucial for generating the Bessel beam. This device precisely phase-modulates the coherent beam, producing a modulated beam carrying a specific composite phase. In practical applications, since most wavefront modulation devices are extremely sensitive to the polarization state of light, a polarization control element, such as a polarizer 500 or a waveplate, is required after beam expansion and collimation but before wavefront modulation. This polarization control adjusts the laser beam to linearly polarized light aligned with the alignment of the liquid crystal molecules within the modulation device. Finally, the phase-modulated beam is projected onto the surface of the object under test through objective lens 403. At this time, due to the distribution characteristics of the modulated beam with the zero-order Bessel function, it forms a non-diffraction range, i.e., depth of focus, within a specific distance behind the objective lens 403, so that the Bessel spot pattern projected on the object surface maintains its shape and size unchanged over a large longitudinal range.

[0030] Regarding the implementation details of the wavefront modulation device, this embodiment employs a spatial light modulator 600 (SLM) loaded with a composite phase map. This spatial light modulator 600 can change the phase of reflected or transmitted light at the pixel-level scale based on a grayscale image input from a computer. Specifically, the composite phase map... It is composed of two parts of phase information superimposed: the first part is the fundamental phase used to generate the Bessel beam, namely the axial-cone phase. The first part is used to converge light rays towards the central axis, thereby producing the physical property of a long focal depth; the second part is used to introduce random phase for random interference. Its function is to disrupt the originally regular wavefront, transforming the smooth Bessel spot into a Bessel speckle pattern with random statistical characteristics through random interference. When a coherent beam illuminates a spatial light modulator 600 loaded with this composite phase pattern, the emitted light wavefront exhibits both a conical tendency to converge toward the axis and random phase fluctuations, thereby forming the Bessel pattern required by this invention. .

[0031] Figure 1 The exhibit showcases the construction of the 400 large depth-of-field microscope system based on Bezier spot projection. (According to the attached...) Figure 1 As shown, the large depth-of-field microscope system 400 mainly consists of a projection illumination optical path, a microscope system 400 body, and an imaging receiver.

[0032] A laser 100 is provided at the beginning of the projection illumination optical path to emit a coherent Gaussian beam. In order to adapt the beam to the subsequent wavefront transformation, the Gaussian beam is then expanded and collimated by a collimating lens 200. Based on this, the collimated parallel beam is incident perpendicularly on the flat side of a conical lens 300 (i.e., an axonoconical lens).

[0033] When light passes through the conical surface of the conical lens 300, it is refracted and, due to constructive interference, forms a Bessel beam with a zero-order Bessel function distribution over a distance behind the lens. This Bessel beam exhibits the characteristics of a bright spot at the center surrounded by concentric rings, and possesses extremely high depth of focus and no diffraction properties.

[0034] The generated Bessel beam enters the microscope system 400. Inside the microscope system 400, a beam splitter (B / S) is provided. The Bessel beam, after being reflected by the B / S, passes through the microscope objective 403 and is projected onto the surface of the object under test. At this time, the object under test is placed within the Bessel beam non-interference zone. It is worth noting that, as... Figure 1 As shown, even if the object being measured is outside the traditional depth of field of a microscopic imaging system, its surface can still be clearly modulated with a Bessel beam pattern because it is still within the coverage area of ​​the Bessel beam.

[0035] The light signal reflected by the object under test is collected by the objective lens 403, passes through the B / S beam splitter, and enters the field lens 402. The field lens 402 converges the light signal carrying the object information and modulation pattern onto the photosensitive surface of the top camera 401, and the camera 401 completes the acquisition and recording of the original image.

[0036] Example 2 This embodiment details an imaging method based on the aforementioned large depth-of-field microscope. This method achieves sharp reconstruction of defocused objects through the deep collaboration of physical modulation and digital computation. In step S1, the system first generates a Bezier beam and modulates it into a preset Bezier pattern. The pattern is then projected onto the surface of the object being measured. It is crucial to ensure that the object is within the non-diffraction range of the Bessel beam. Due to the unique non-diffraction properties of the Bessel beam, even if the surface of the object has significant undulations, or if the object itself is outside the physical depth of field of the microscope objective 403, the projected Bessel pattern onto its surface will still be within the non-diffraction range. It can still maintain a clear structure, thus providing a stable and reliable modulation signal for subsequent algorithm reconstruction.

[0037] After the physical projection of the light field is completed, the process proceeds to step S2, the image acquisition stage. Using the imaging system, two raw images are acquired sequentially without changing the position of the object being measured. The first image is a defocused image taken without projection. Because the object being measured is outside the depth of field of the microscope, the image exhibits a noticeable blurring characteristic in its optical performance. The second image is a modulated defocused image taken under Bezier pattern projection. Because of the overlay of clear Bézier pattern information, this image contains composite information of object features and modulation patterns. It is worth noting that, for human visual observation, the first image... Second image All of them appear as unrecognizable, blurry images.

[0038] In step S3, the system acquires the first image. Second image and known Bezier patterns A unified input calculation module is used. Based on this, step S4 involves the calculation module executing the core frequency domain reconstruction algorithm. The theoretical basis of this algorithm lies in the convolution model of the optical system: the first image before projection... It can be described as an ideally focused image. With system point spread function Convolution, i.e. The second image when projected It is a focused image With Bezier pattern The sum of these and the point spread function The result of convolution, i.e. .

[0039] Specifically, the frequency domain reconstruction algorithm executed by the calculation module is as follows: First, for the first image... Second image and Bezier pattern Performing Fourier transforms on each, according to the convolution theorem, the convolution operation in the spatial domain is transformed into a multiplication operation in the frequency domain, thus obtaining the corresponding frequency domain distribution. and Next, by performing algebraic operations on these two frequency domain equations, the unknown point spread function frequency domain term can be eliminated. This allows us to construct an equation for solving the frequency domain distribution of a sharp image. From this, we can obtain the frequency domain solution for the sharp image. The formula is: Finally, the obtained frequency domain solution... By performing an inverse Fourier transform, a fully focused, clear image of the object in the spatial domain can be obtained. The significant advantage of this computational imaging method is that it does not rely on mechanical focusing or Z-axis stacking scanning. It only requires a single acquisition (two images) to eliminate defocus blur at the algorithm level, greatly improving imaging speed and adaptability to complex samples.

[0040] Example 3 Figure 2 This demonstrates the structure of a medical microscopic image acquisition encryption system. (According to the attached...) Figure 2 In conjunction with encryption algorithm logic, the system introduces a digital spatial wavefront modulation module on the basic large depth-of-field microscopic architecture, realizing the integration of shooting and encryption.

[0041] A key input interface is provided at the system control end. This key, after being processed by a HASH function, generates a binary sequence used to generate control signals for logical modulation of the spatial light modulator 600 (SLM). At the optical path end, the Gaussian beam emitted by the laser 100, after passing through the collimating lens 200, first passes through a polarizer 500. The polarizer 500 adjusts the laser light to linearly polarized light to match the polarization sensitivity characteristics of the subsequent liquid crystal SLM.

[0042] A linearly polarized beam illuminates an SLM (Self-Modified Array). The SLM is loaded with a computer-generated composite phase map, which includes an axial-cone phase used to generate the Bessel properties and a random phase determined by the key. After reflection modulation by the SLM, the beam is converted into a Bessel beam carrying encrypted information. Here, the Bessel beam exhibits a controlled Bessel speckle structure, the spatial distribution of which is uniquely determined by the key.

[0043] The Bessel beam carrying encrypted information enters the microscope system 400, is deflected by the beam splitter B / S, and is projected onto the surface of the medical sample via the objective lens 403. For example... Figure 2 As shown, the system is intentionally configured to place the medical sample within the Bessel beam interference-free zone, but far from the conventional depth of field range of the microscope objective 403. This arrangement ensures that the sample image exhibits severe defocus blur before computational reconstruction.

[0044] The sample reflected light, modulated with Bessel speckle, passes through objective lens 403 again, through the B / S (bulk bottom and spherical) lens, and is imaged onto camera 401 by field lens 402. At this point, both the first image g1 and the second image g2 captured by camera 401 are defocused and speckle-modulated secure images. Only with the correct key known can the same projection pattern be obtained through simulation, and a clear sample image be reconstructed using the computational module.

[0045] This embodiment further expands the application of the above imaging method in the fields of medicine and sensitive image protection, disclosing an integrated imaging and encryption method. This method combines the generation process of Bezier spots with modern cryptographic mechanisms. In generating Bezier patterns... During the process, the system acquires an initial key. This key is converted into a binary sequence using a hash function. Based on the value of each bit (0 or 1) in this binary sequence, a random phase is determined according to a preset mapping rule. For example, when the hash function outputs a value of 0, the corresponding pixel phase is set to 0; when the output value is 1, the corresponding phase is set to π. This random phase generated by the key... It possesses extremely high information entropy. This random phase is compared with a fixed axis-cone phase. The layers are superimposed to generate the final composite phase map. This modulates the spatial light modulator 600, thereby generating Bezier speckle patterns as encryption patterns in physical space.

[0046] The formula for calculating the composite phase diagram is as follows:

[0047] In the formula, It is the axial-cone phase, used to generate Bessel beams. Or simplified to conical phase , where r is the radial distance. Its function is to converge light rays towards the central axis, creating a long depth of focus. The random phase is used to generate speckle, and its generation method is to generate a uniformly distributed random number matrix in the interval (0, 2π).

[0048] Calculated The grayscale image is loaded onto the SLM. A laser illuminates the SLM, and the SLM changes the phase of the reflected (or transmitted) light according to the grayscale value of each pixel. At this point, the outgoing light wavefront exhibits both a conical convergence tendency and random fluctuations, which is known as Bezier speckle.

[0049] Under this encryption system, the first image Second image The images themselves constitute encrypted, secure images because they are visually blurry and exhibit disordered speckle modulation. For an authorized recipient, the correct initial key must be present. By inputting this key into the same hash function and algorithm model, the recipient can locally simulate and calculate a Bezier pattern that is completely identical to the one captured by the camera. Frequency domain distribution Only when accurate Only then can a clear image be reconstructed using the aforementioned frequency domain deconvolution formula. For unauthorized individuals who have not obtained the key, since they cannot know the distribution pattern of the random phase, they are unable to simulate the correct projection pattern. This completely blocks the possibility of recovering valid information from a blurry image from a mathematical logic perspective.

[0050] In summary, this invention solves the defocusing problem in microscopic imaging by leveraging the long depth-of-field physical characteristics of Bessel beams, and cleverly utilizes the projection pattern as a key to achieve simultaneous imaging and encryption at the physical level. Whether for rapid imaging of thick tissue sections in biomedicine, observation of fine structures with varying elevations in industrial testing, or even the simultaneous imaging and encryption protection of sensitive medical data, this invention demonstrates significant technical advantages and application prospects.

[0051] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A large depth-of-field microscope based on Bezier spot projection, characterized in that, include: A projection system for generating a Bessel beam with non-diffraction characteristics and using the Bessel beam to project a Bessel pattern onto the surface of the object being measured. An imaging system for acquiring images of the object under test, including a first image without the application of the Bezier pattern projection. and the second image when the Bezier pattern projection is applied. ; Calculation module, used to calculate based on the first image Second image And perform frequency domain deconvolution operation on the known Bezier pattern t to reconstruct a fully focused, clear image f of the object under test.

2. A large depth-of-field microscope based on Bezier spot projection according to claim 1, characterized in that, The projection system includes: A light source used to emit a coherent beam of light; A wavefront modulation device is used to phase modulate the coherent beam to generate a modulated beam carrying a composite phase. An objective lens is used to project the modulated beam onto the surface of the object being measured.

3. A large depth-of-field microscope based on Bezier spot projection according to claim 2, characterized in that, The wavefront modulation device is a spatial light modulator loaded with a composite phase map, which includes an axial-cone phase for generating a Bessel beam. and random phase used to introduce random interference .

4. An imaging method based on the large depth-of-field microscope according to claim 1, characterized in that, The steps include the following: Step S1: Generate a Bessel beam and modulate it into a preset Bessel pattern t, then project it onto the surface of the object under test, ensuring that the object under test is within the non-diffraction range of the Bessel beam; Step S2: Acquire two original images of the object under test using the imaging system, namely the first image without projection. And the second image with projection ; Step S3: Transfer the first image Second image and the Bezier pattern t input calculation module; Step S4: The calculation module executes the frequency domain reconstruction algorithm and outputs a fully focused, clear image f.

5. The imaging method according to claim 4, characterized in that, The frequency domain reconstruction algorithm in step S4 specifically includes: for the first image Second image Performing Fourier transforms on the Bessel pattern t and the corresponding frequency domain distribution yields the corresponding frequency domain distribution. , and ; A system of equations is constructed based on the complete frequency domain distribution, and the frequency domain solution of the clear image is obtained by solving it. ; For the frequency domain solution Perform an inverse Fourier transform to obtain a fully focused, sharp image. .

6. The imaging method according to claim 5, characterized in that, The frequency domain solution Solve using the following formula: 。 7. The imaging method according to claim 4, characterized in that, The object under test is located outside the physical focal plane of the imaging system, and the first image and the second image All images were out of focus and blurred during the acquisition process.

8. A method for encrypting images based on the imaging method of claim 4, characterized in that, The process of generating the Bezier pattern t in step S1 includes: Obtain the initial key and use a hash function to convert the key into a binary sequence; Determine the random phase based on the numerical mapping result generated from the binary sequence. ; The random phase Phase with preset shaft cone Superposition yields a composite phase map. ; Using the composite phase diagram A spatial light modulator is modulated to generate a Bessel speckle pattern as an encryption pattern, referred to as the Bessel pattern t.

9. The method for encrypting images according to claim 8, characterized in that, The random phase The determination rule is as follows: based on whether the HASH function value is 0 or 1, the corresponding random phase is determined to be 0 or π respectively.

10. The method for encrypting images according to claim 8, characterized in that, In step S4, the receiver must input the initial key that is consistent with the encryption end in order to reconstruct the Bezier pattern t consistent with the projection through simulation calculation; otherwise, the fully focused clear image f cannot be recovered.

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