A lightweight imaging probe and imaging device with a superlens

Abstract

This application provides a lightweight imaging probe and imaging device using a superlens, relating to the field of nonlinear optical imaging. By employing a split structure, a miniaturized imaging probe is achieved. During imaging, the imaging probe can be fixedly connected to the object being imaged. Excitation light is used to induce nonlinear optical effects within the object, thereby acquiring optical signals reflecting the internal structure of the object. Specifically, this application ensures that the laser is precisely focused on a specific position within the object corresponding to the scanning angle through a coordinated optical path design of the scanning galvanometer, scanning lens, and objective lens. This effectively triggers nonlinear optical effects while ensuring efficient acquisition of optical signals, thus providing a reliable technical foundation for high-resolution internal imaging. Furthermore, this application uses a superlens structure to construct the objective lens, avoiding the weight and weight associated with traditional optical objectives, thereby achieving a lightweight imaging probe, reducing the impact on the object being imaged, and obtaining more accurate images.

Description

Technical Field

[0001] This application relates to the field of nonlinear optical depth imaging technology, specifically to a lightweight imaging probe and imaging device using a superlens. Background Technology

[0002] Nonlinear optical depth imaging is a technique that utilizes nonlinear optical effects to achieve deep, high-resolution three-dimensional imaging. It overcomes the limitations of traditional linear optical imaging in terms of penetration depth and resolution by leveraging nonlinear phenomena generated by the interaction between light and matter (such as two-photon absorption and second harmonic generation).

[0003] In nonlinear optical depth imaging, high-intensity (usually pulsed) lasers are often used to cause the sample to simultaneously absorb two or more low-energy photons (such as near-infrared light) to excite fluorescence or generate signals. This nonlinear process only occurs in a region with a very small focal point, thus inherently possessing optical slicing capabilities, enabling three-dimensional imaging without the need for a confocal pinhole.

[0004] Near-infrared excitation light scatters less than visible light, allowing it to penetrate deeper into scattering media such as biological tissues. Meanwhile, signals generated by nonlinear excitation (such as fluorescence) typically have shorter wavelengths, which can be effectively separated from the excitation light, reducing background noise and thus achieving greater imaging depth.

[0005] For example, nonlinear optical depth imaging can include second harmonic generation (SHG), third harmonic generation (THG), two-photon excited fluorescence (TPEF), three-photon excited fluorescence (3PEF), and coherent anti-Stokes Raman scattering (CARS).

[0006] In practical applications, imaging devices with nonlinear optical effects often rely on large-scale equipment due to their complex internal optical paths. Therefore, how to achieve nonlinear optical depth imaging with good imaging results using miniature devices is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present application provides an imaging device that achieves probe miniaturization through a separate design of the probe and the host, thereby solving the above-mentioned technical problems.

[0008] In a first aspect, this application provides an imaging probe applied to an imaging device based on nonlinear optical imaging. The imaging probe includes a housing and a depth imaging device based on nonlinear optics. One end of the housing is provided with a first port for fixed connection to the object under test. The depth imaging device includes a laser source and a scanning galvanometer, a scanning lens, and an objective lens arranged sequentially along the laser optical path, wherein the objective lens includes at least one superlens structure. The laser emitted from the laser source passes sequentially through the scanning galvanometer, the scanning lens, and the objective lens, and is focused through the first port onto a scanning position corresponding to the scanning angle of the scanning galvanometer at the internal focal plane of the object under test, thereby triggering a nonlinear optical effect. The optical signal generated by the nonlinear optical effect is acquired through the first port and transmitted to the detector.

[0009] Secondly, this application provides an imaging device based on nonlinear optical imaging, comprising the imaging probe, laser, and detector described in the first aspect. The laser generates and transmits laser light to the imaging probe. The detector detects the optical signals acquired by the imaging probe.

[0010] The imaging probe and imaging device provided in this application achieve a miniaturized imaging probe through a split structure. During imaging, the imaging probe can be fixedly connected to the object being imaged. By exciting light within the object to induce a nonlinear optical effect, optical signals reflecting the internal structure of the object are acquired to detect its internal condition. Specifically, this application ensures that the laser is precisely focused on a specific position within the object corresponding to the scanning angle through a coordinated optical path design of the scanning galvanometer, scanning lens, and objective lens. This effectively triggers the nonlinear optical effect while guaranteeing efficient acquisition of optical signals, thus providing a reliable technical foundation for high-resolution internal imaging. Furthermore, this application uses a superlens structure to construct the objective lens, avoiding the weight associated with traditional optical objectives, thereby achieving a lightweight imaging probe, reducing the impact on the object being imaged, and ultimately obtaining more accurate images. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 These are application scenario diagrams of imaging devices provided in some embodiments of this application.

[0013] Figure 2 This is a schematic diagram of the structure of an imaging probe provided in some embodiments of this application.

[0014] Figure 3 These are schematic diagrams illustrating single-layer and double-layer superlenses at different scanning angles according to some embodiments of this application.

[0015] Figure 4 This is another schematic diagram of the structure of the imaging probe provided in some embodiments of this application.

[0016] Figure 5 This is an exemplary flowchart of a method for manufacturing a superlens structure that takes into account the range of assembly errors, provided in some embodiments of this application.

[0017] Figure 6 This is an exemplary flowchart of a method for configuring a desired transfer function provided in some embodiments of this application. Detailed Implementation

[0018] As mentioned earlier, nonlinear optical depth imaging often relies on excitation light to trigger nonlinear optical phenomena, thereby obtaining the corresponding optical signals. For example, second harmonic generation (SHG) is a second-order multiphoton phenomenon where two photons of the same frequency interact with a nonlinear material and merge into a new photon with twice the frequency. Another example is three-photon excited fluorescence (3PEF), which requires three photons to be excited simultaneously to generate a fluorescence signal.

[0019] To further illustrate the practical application of miniaturized devices for nonlinear optical depth imaging, this application provides a schematic diagram of an imaging device's application scenario. Figure 1 ).in, Figure 1 The application scenario shown reflects the process of optical brain imaging of mice by imaging devices.

[0020] like Figure 1 As shown, the application scenario of the imaging device may include imaging device 10 and imaging object 20.

[0021] The imaging device 10 is the main body for performing nonlinear optical imaging (e.g., the imaging device 10 can be configured as a multiphoton microscope), which can release excitation light to trigger multiphoton effects (such as multiphoton fluorescence effects) inside the imaging object 20, thereby acquiring the optical signal of the imaging object 20 after being excited by the excitation light and generating a fluorescence image of the imaging object 20.

[0022] For example, the imaging device 10 can focus multiple photons of the excitation light onto a point at the target focal depth inside the imaging object 20 based on the principle of nonlinear optical imaging to obtain the fluorescence signal at that point. Then, by changing the focus position at the target focal depth through scanning technology to perform planar scanning, the fluorescence signals at various locations inside the imaging object 20 at the target focal depth can be obtained to determine the fluorescence image.

[0023] The imaging object 20 can refer to an object that needs to be nonlinearly optically imaged. For example, the imaging object 20 can be an ex vivo sample, a live sample, etc. For example, the imaging object 20 in this application can be an imaging object such as a mouse, rabbit, bird, non-human primate rhesus monkey, marmoset, etc. The imaging object 20 can generally be used to image the internal structure (brain nerves, spinal nerves, etc.) of the imaging object.

[0024] like Figure 1 As shown, Figure 1 The imaging subject 20 can be a mouse, specifically, the mouse brain can be subjected to nonlinear optical imaging. The imaging device 10 can be fixedly connected to the brain of the imaging subject 20, which can move freely. The imaging device 10 can periodically scan the subject during its free movement to acquire optical signals at various locations within a specific focal plane of the brain, thereby determining a temporal optical image of that location. The acquired optical images generally include neural synapses at that location. Alternatively, the imaging subject 20 can also be a bat, allowing for bat brain imaging.

[0025] It should be noted that before the imaging object 20 is fixedly connected to the imaging device 10, the imaging object 20 can be adapted. For example, the skin at the fixed connection point between the imaging object 20 and the imaging device 10 can be prepared. Another example is for... Figure 1 The mouse shown can have a cranial window created in its brain during fixation to improve imaging. Alternatively, a fluorescent probe can be injected into the imaging subject 20 beforehand to enable multiphoton fluorescence imaging based on the probe.

[0026] As a miniaturized front imaging device, the imaging device 10 provided in this specification can be set up in a split manner, thereby further including an imaging probe 100 and an imaging host 200, wherein the imaging probe 100 and the imaging host 200 can be connected for communication based on an optoelectronic composite cable 300.

[0027] The imaging probe 100 can be a device for releasing excitation light and detecting optical signals. Specifically, the imaging probe 100 can convert the laser generated by the laser source into excitation light focused on the focal plane and possessing scanning capability through optical components. In some embodiments, the imaging probe 100 can be a contact imaging probe.

[0028] The imaging host 200 may be a collection of devices that cannot be integrated into the imaging probe 100. Specifically, it can be used to provide laser light and perform imaging based on optical signals. The imaging host 200 generally includes a laser and a detector. The laser is used to generate and transmit laser light to the imaging probe 100, and the detector is used to detect the optical signals acquired by the imaging probe 100.

[0029] The optoelectronic composite cable 300 can be a communication cable between the imaging probe 100 and the imaging host 200, used to realize the data transmission of optical and electrical signals between the imaging host 200 and the imaging probe 100. Specifically, the optoelectronic composite cable 300 can transmit the excitation light generated by the imaging host 200 to the inside of the imaging probe 100, and transmit the optical signals collected by the imaging probe 100 to the imaging host 200 to form an optical image.

[0030] However, in practical applications, the optical path within the imaging probe 100 is often constructed using traditional optical components (such as lenses). For example, the objective lens within the imaging probe 100 is often constructed using lenses. Due to the stringent requirements for image quality, field of view, and off-axis aberration of the imaging probe 100 itself, the objective lens in the imaging probe 100 often employs a lens group composed of multiple gradient index (GRIN) lenses. While such lenses can meet certain image quality requirements, they are relatively heavy and long, and the lens group itself also has relatively strict alignment requirements.

[0031] To ensure the imaging quality of miniature two-photon microscopes (m2PMs) and minimize their interference with animal behavior, the equipment needs to be very lightweight. However, the objective lenses, which are composed of the aforementioned lenses, are relatively heavy, resulting in the imaging probe typically weighing more than 2 grams (in reality, it is often greater than 2 grams, such as 2.6 grams, 4 grams, etc.).

[0032] To reduce the weight of the imaging probe, this application employs a metalen structure to construct the objective lens. A metalen is a planar optical lens based on metasurface technology. It precisely controls the phase, amplitude, and polarization of light waves by designing and arranging a large number of subwavelength nanostructure units on a two-dimensional plane, thereby achieving focusing and imaging functions similar to traditional curved lenses.

[0033] In a superlens, various cells (also called superatomic or subwavelength structural units) are formed, serving as the basic functional units constituting the superlens. A cell is typically a nanostructure (such as a nanopillar, nanofin, or pore) smaller than the operating wavelength, arranged periodically or quasi-periodically on a plane. Each cell, through its specific geometry, size, material, and orientation, generates precise phase, amplitude, or polarization modulation of the incident light, thereby collectively achieving the overall optical function of the superlens.

[0034] By designing the arrangement of superlens cells, a superlens that meets the requirements of an objective lens can be designed to serve as the objective lens for an imaging probe. Under the same other structures, the superlens can significantly reduce the weight of the imaging probe. Actual testing shows that the imaging probe provided in this application weighs far less than the imaging probe of a traditional optical device architecture. Specifically, its weight can be 1.36 grams (first-generation device) or 1.06 grams (second-generation device).

[0035] In practical applications, based on the ultra-lightweight design brought about by the aforementioned superlens, the optimized imaging probe can minimize the inertial effect during free movement, so as to ensure the stability and robustness of the imaging probe in free-moving animals, and provide high-fidelity group recordings for related research (such as behavioral neuroscience).

[0036] Exemplary imaging probe: To further illustrate the imaging device capable of simultaneous excitation of multiple wavelengths provided in this application, this application also provides a schematic block diagram of the internal structure of the imaging device ( Figure 2 This is to illustrate the transmission of photoelectric signals (especially lasers of various wavelengths) within the imaging device.

[0037] Figure 2 This is a schematic diagram of an imaging probe according to some embodiments of this application. For example... Figure 2 As shown, this imaging probe 100 aims to solve the trade-off between weight, size, and optical performance in traditional imaging probes. It achieves ultra-lightweight, large-field-of-view nonlinear optical imaging through the design of the probe's housing and depth imaging device. The following is combined with... Figure 2 This embodiment will be described in detail below.

[0038] like Figure 2 As shown, the imaging probe 100 of this application may include a housing 110 and a depth imaging device 120. This imaging probe 100 is used in an imaging device based on nonlinear optical imaging. The imaging probe 100 is a front-end detection unit for a nonlinear optical imaging device.

[0039] The housing 110 is a mechanical structure used to encapsulate and protect the internal optical components. It should have sufficient mechanical strength and stability to withstand vibrations and impacts during animal activity, thereby maintaining the relative position of the optical components. In some embodiments, the housing 110 may be a miniature support made of aluminum alloy; in other embodiments, the housing 110 may be a lightweight structure made of polyetheretherketone (PEEK) material.

[0040] One end of the housing 110 is provided with a first port 111 for fixed connection with the object under test, so as to achieve a stable connection between the imaging probe 100 and the object under test and ensure accurate positioning of the imaging optical path. The first port 111 is an opening structure on the housing 110 for establishing an optical connection with the object under test. It should have an appropriate size and shape to fit well with the surface of the object under test, thereby ensuring efficient transmission of excitation light and collection light. In some embodiments, the first port 111 can be a circular opening with a diameter of 1-2 mm; in other embodiments, the first port 111 can be a rectangular opening that matches the size of the cranial window.

[0041] The object to be tested refers to a biological tissue or organ that needs to be imaged and observed, used to establish a stable connection with the first port 111 to achieve efficient transmission of optical signals through this connection, thereby supporting continuous imaging of the target area. In some embodiments, the object to be tested may be the cerebral cortex of a mouse; in other embodiments, the object to be tested may be a specific brain region of a bat.

[0042] The depth imaging device 120 is a system unit integrating multiple optical components to achieve deep tissue imaging. It provides sufficient optical slicing capability and has a reasonable weight-to-volume ratio to operate stably under free movement conditions, thereby enabling long-term observation of neural activity. The depth imaging device 120 includes a laser source 121 and a scanning galvanometer 122, a scanning lens 123, and an objective lens 124 arranged sequentially along the laser optical path, wherein the objective lens 124 includes at least one superlens structure.

[0043] Laser source 121 is an optical device that provides laser light, such as a combination of optical fiber and collimator, with its other end connected to a laser to provide laser pulses of appropriate wavelength and power to effectively excite fluorescence signals in the target region, thereby achieving high signal-to-noise ratio imaging. For example, laser source 121 may be an optical assembly including an optical fiber and collimator connected to a femtosecond laser with a wavelength of 920 nm.

[0044] To accommodate the laser, a second port 112 is formed on the other side of the housing 110. The second port 112 is used to receive the laser source 121 (optical fiber). In some embodiments, the second port 112 can be used to connect an optical fiber transmission system to introduce the laser generated by the laser into the imaging probe 100.

[0045] The scanning galvanometer 122 is a microelectromechanical system (MEMS) used to control the scanning direction of the laser beam, providing a sufficiently large scanning angle and high scanning frequency to achieve a large field of view and high frame rate imaging, thereby capturing rapid neural activity. For example, the scanning galvanometer 122 can be a MEMS with an optical scanning angle of ±12°. Furthermore, it should be noted that the actual angle of the scanning galvanometer 122 can be configured as needed, and can be either 45° as shown in the figure, or an angle between 20° and 30°, to improve scanning quality.

[0046] The scanning lens 123 is an optical component used to convert the deflection angle of the scanning galvanometer 122 into a spatial position, and to accurately convert the scanning angle into a linear displacement to form a uniform scanning field, thereby achieving consistent imaging quality within the field of view.

[0047] Objective 124 is an optical component used to focus excitation light and collect fluorescence signals. It should have a high numerical aperture and a large field of view to achieve high-resolution imaging while maintaining a lightweight design, thereby supporting the observation of deep neural networks. In some embodiments, objective 124 may be a simple structure comprising a single superlens. In other embodiments, objective 124 may be a composite structure comprising multiple superlenses. The superlens structure is a planar optical element that utilizes subwavelength structural units to achieve phase modulation, providing sufficient phase control range and high transmittance to achieve efficient beam focusing and aberration correction, thereby supporting high-quality imaging. In some embodiments, the superlens structure may be based on a titanium dioxide (TiO2) metasurface.

[0048] Based on the aforementioned design, the laser emitted by the laser source 121 needs to be focused through the first port 111 onto the scanning position corresponding to the scanning angle of the scanning galvanometer at the internal focal plane of the object under test, after the coordinated action of the scanning galvanometer 122, scanning lens 123, and objective lens 124, thereby triggering a nonlinear optical effect. There is a definite geometric relationship between the scanning position of the internal focal plane and the scanning angle of the scanning galvanometer; that is, for a given scanning angle, the laser can be focused onto a specific scanning position on the focal plane, thus achieving scanning within the target area by controlling the scanning angle.

[0049] Nonlinear optical effects are optical phenomena that occur in matter under strong light fields, where the relationship between the light intensity and the optical signal is not linear. These effects are used to generate sufficient signal intensity to achieve high signal-to-noise ratio imaging in deep tissues, thereby supporting the accurate detection of neural activity. To generate these nonlinear optical effects, a laser beam with high coherence and directionality should possess appropriate wavelength and pulse characteristics to effectively excite target fluorescent molecules and produce nonlinear optical effects, thus enabling deep tissue imaging. For example, in the two-photon effect, the laser could be a pulsed laser with a wavelength of 920 nm.

[0050] During the aforementioned scanning process, the scanning galvanometer 122 is used to control the laser beam scanning path, providing a sufficiently large scanning range and high scanning speed to achieve a large field of view and high frame rate imaging, thereby capturing rapidly changing neural activity. The scanning lens 123 is used to convert the scanning angle into spatial position, accurately converting the angular displacement of the scanning galvanometer 122 into spatial displacement to form a uniform scanning field, thereby achieving consistent imaging quality within the field of view. The objective lens 124 is used to focus the laser beam and collect signals; it should have a high numerical aperture and a large working distance to achieve high-resolution imaging while maintaining a lightweight design, thus supporting the observation of deep neural activity.

[0051] The aforementioned nonlinear optical effect generates an optical signal, which can be acquired and transmitted to the detector via the first port 111 (e.g., via a fluorescent fiber 130). (The fluorescent fiber 130 can also be directly replaced by a detector (e.g., a SiPM), thus allowing the optical signal to directly enter the detector at the imaging probe.) The optical signal is related to the aforementioned nonlinear optical effect; for example, for multiphoton effects, the optical signal can be a fluorescence signal in the wavelength range of 500-560 nm.

[0052] Based on this optical signal, the detector can capture the optical signal and convert it into an electrical signal, thereby achieving high signal-to-noise ratio imaging. In some embodiments, the detector may be a photomultiplier tube; in other embodiments, the detector may be a single-photon avalanche diode.

[0053] In the aforementioned optical path, objective lens 124 can be implemented using a metalens structure. This metalens structure can be based on the desired optical response of objective lens 124 itself (see details...). Figure 5 , 6 (Related description) configuration, instead of traditional lens groups, reducing weight.

[0054] Therefore, based on the design of the imaging probe 100 described above, it can effectively solve the contradiction between weight, size, and optical performance faced by traditional imaging probe systems. Specifically, a first port 111 is provided at one end of the housing 110 to achieve a stable connection with the object under test, ensuring accurate positioning of the imaging optical path; through the coordinated action of the laser source 121, scanning galvanometer 122, scanning lens 123, and objective lens 124 in the depth imaging device 120, precise focusing of the laser on the focal plane inside the object under test is achieved; the optical signal generated by the nonlinear optical effect is collected through the first port 111 and transmitted to the detector, completing the entire imaging process.

[0055] In actual fabrication, based on the aforementioned objective lens constructed from a superlens, the imaging probe achieved an ultra-lightweight design of 1.06g. Simultaneously, through appropriate cellular design, the field of view can be expanded to 350×330μm. ²Furthermore, it extends the imaging depth to 210 μm, significantly improving imaging quality and practicality, and providing a reliable tool for neuroscience research on freely moving animals.

[0056] This application identifies that traditional single-layer objective lens designs in imaging probes suffer from limited field of view and insufficient aberration correction capabilities. This is because a single superlens must simultaneously achieve beam collimation and focusing, making it impossible to maintain both high resolution and low aberrations under large field-of-view conditions. Particularly when the system needs to cover a large field of view (>300 μm), the resolution at the edges significantly decreases, affecting the accurate observation of large-scale neural activity. These problems limit the application scope of imaging probes in behavioral neuroscience.

[0057] To further illustrate this point, this application also provides a schematic diagram of single-layer and double-layer superlenses under different scanning angles ( Figure 3 ).

[0058] Figure 3 The diagram illustrates the light spots formed at the focal plane (SIP) by a single-layer superlens (MO being the superlens objective) and a double-layer superlens at different incident angles. For example... Figure 3 As shown, based on the complex mechanism of a single-layer superlens, the edge of the light spot formed by it has obvious noise, while the double-layer superlens designed by decoupling its mechanism has better optical performance.

[0059] To further illustrate this point, this application also provides an imaging probe equipped with a double-layered superlens. Figure 4 ).like Figure 4 As shown, the objective lens 124 also includes a first superlens 1241 and a second superlens 1242.

[0060] To achieve better aberration correction and beam control, objective lens 124 employs a composite structure of a first superlens 1241 and a second superlens 1242 arranged sequentially along the laser beam path to decouple the beam collimation and focusing functions. The first superlens 1241, located on the incident side of objective lens 124, pre-compensates the laser to collimate the laser wavefront at the internal focal plane, thereby improving image quality. The second superlens 1242 achieves final focusing of the laser to form a high-quality spot at the internal focal plane, thus supporting high-resolution imaging.

[0061] In some embodiments, a first superlens 1241 is disposed on the incident side of a second superlens 1242, and its surface phase structure is configured based on the object under test for pre-compensation of the laser to ensure the formation of a collimated wavefront at the internal focal plane. The incident side refers to the side from which the light enters the optical system, ensuring proper guidance of the light path to achieve the desired optical function and support high-quality imaging. The surface phase structure is a microstructure on the surface of the superlens used to regulate the phase distribution, providing precise phase control to achieve the desired beam modulation function, thereby optimizing image quality. Pre-compensation involves pre-correcting the phase of the laser beam before it enters the target region, effectively correcting phase distortion introduced by the object under test to form a collimated wavefront at the internal focal plane, thereby improving image quality. Pre-compensation is generally wavefront shaping based on the refractive index of the object under test. For example, the phase structure of the first superlens 1241 is optimized for specific cranial window thickness and brain tissue characteristics, enabling the laser to form a collimated wavefront at the internal focal plane, thus significantly improving image quality.

[0062] Based on the aforementioned logic, the decoupling of beam collimation and focusing functions can be achieved. In practical design, the maximum phase gradient of the imaging probe can be reduced (from 1596 π mm in a single-layer design). -1 Reduced to 992.6 π mm -1 This significantly relaxed design and manufacturing restrictions.

[0063] In imaging probes, wavefront distortion often occurs when the laser beam enters the objective lens 124 due to matching issues between optical components in the optical path. This is particularly problematic when using a double-layer metalens structure; if the beam characteristics of the first metalens 1241 and the second metalens 1242 are mismatched, aberration accumulation can occur, affecting image quality. Traditional designs struggle to simultaneously optimize beam matching between the two metalenses, a problem that becomes more pronounced at large scanning angles. These issues limit the system's imaging performance under wide field-of-view conditions.

[0064] In some embodiments, the surface phase structure of the first superlens 1241 can be configured based on the aperture surface of the second superlens 1242 to keep the laser beam parallel within the aperture surface of the second superlens 1242. Specifically, the phase distribution of the first superlens 1241 is optimized for the aperture characteristics of the second superlens 1242, so that the laser beam forms parallel light within the aperture surface of the second superlens 1242, effectively avoiding beam distortion. That is, the surface phase structure of the first superlens 1241 is also configured based on the aperture surface of the second superlens 1242 to adjust the laser beam into parallel light within the aperture surface of the second superlens 1242.

[0065] The surface phase structure is a microstructure on the surface of the superlens used to regulate the phase distribution, providing precise phase control to achieve the required beam modulation function and thus optimize image quality. The aperture surface is the effective area on the optical element through which the beam passes; it should have appropriate size and shape to support the required beam characteristics and thus optimize image quality. Parallel light is light in which all rays in the beam are parallel to each other; it should have a sufficiently small divergence angle to maintain a uniform energy distribution within the aperture surface of the second superlens 1242, thereby supporting high-quality imaging.

[0066] To further reduce the weight of the scanning lens, the aforementioned scanning lens can also be implemented based on superlens technology. A scanning superlens is a planar optical element that utilizes superlens technology to achieve scanning functionality, providing a sufficient scanning angle and uniform energy distribution to achieve consistent imaging quality across a large field of view, thereby supporting high-quality observation of neural activity. For example, in an imaging probe, the scanning superlens can be a superlens with a focal length of 2.7 mm.

[0067] In some embodiments, in addition to the aforementioned modulation of the scanning angle, the scanning superlens can also be used to adjust the laser beam passing through the scanning galvanometer so that the laser forms an energy-uniform planar image plane before entering the objective lens. The planar image plane is a plane with a uniform energy distribution formed after the laser beam passes through the scanning lens. It should have a uniform energy distribution and appropriate curvature to maintain stable imaging quality throughout the scanning range, thereby achieving high-quality observation of neural activity. This planar image plane can be used as the design reference for the desired output light field of the scanning lens.

[0068] The scanning lens based on the aforementioned superlens structure enables the imaging probe to maintain an RMS spot radius of less than 4 μm across the entire scanning angle range (±12°), with the MTF cutoff frequency approaching the diffraction limit. This allows the system to achieve a large field of view with a diameter of 490 μm, while maintaining a lateral resolution of 1.17 μm at the center and an edge resolution uniformity of over 80%, significantly improving imaging quality.

[0069] Based on the above design, the imaging probe provided in this application weighs only 1.06g, meeting the weight requirements for imaging freely moving animals. Simultaneously, in terms of imaging performance, it achieves uniform, high-quality imaging across the entire 490μm field of view, with a lateral resolution of 1.17μm at the center, an axial resolution of 19.85μm, and edge resolution maintained at over 80% of the center value, extending the imaging depth to 210μm. The RMS spot radius is reduced by >90%.

[0070] In imaging probes, the movement of freely moving animals causes vibrations and impacts to the head assembly, making it difficult to maintain the assembly precision of traditional optical systems. This leads to optical path shifts and decreased image quality. Particularly in long-term experiments, even minute assembly errors accumulate, severely affecting the stability and reliability of imaging. These problems limit the system's long-term stable imaging capability under free-movement conditions, impacting long-term observation of neural activity.

[0071] To ensure the stability of the system within the assembly tolerance range, the objective lens 124 and the scanning lens 123 are designed based on the assembly tolerance of the limiting structure, so that the system can maintain a high-quality laser optical path within the allowable assembly error range.

[0072] In imaging probes, traditional optical systems struggle to maintain stable optical path performance due to minute errors in manufacturing and assembly processes. Especially after repeated disassembly and reassembly, assembly errors can lead to optical path shifts and decreased image quality, affecting experimental repeatability and long-term stability. These issues limit the system's application in multi-day experiments, making it difficult for researchers to track long-term changes in neuronal activity. This application addresses this by designing the assembly tolerance of the objective lens 124 and scanning lens 123 based on a limiting structure, enabling the system to maintain a high-quality laser optical path within permissible assembly error ranges. Specifically, the optical element design considers the impact of assembly tolerances, ensuring stable imaging performance even after repeated disassembly and reassembly. Furthermore, even with the aforementioned limiting structure, shifts can still occur in practical applications due to the autonomous movement of the imaging object. To overcome assembly errors and shifts in the limiting structure, the aforementioned superlens structure can be configured as a shift-insensitive superlens, as detailed later. Figure 5 And its related descriptions.

[0073] In some embodiments, the surface phase structure of the aforementioned superlens structure is constructed based on a polarization-insensitive dielectric cell array. Polarization insensitivity refers to the optical element's insensitivity to the polarization state of incident light, maintaining consistent optical performance. That is, the dielectric cell array can maintain stable optical performance under different polarization states, enabling reliable imaging under free-moving conditions and avoiding signal fluctuations caused by polarization changes. In practical implementation, polarization insensitivity can be achieved through symmetrical structures, special material properties, or practical testing.

[0074] The aforementioned polarization insensitivity is primarily used to improve the robustness of superlenses. Specifically, in miniature two-photon microscopes, free movement causes changes in the polarization state of the laser in the optical fiber, thus affecting image quality. Traditional superlenses are typically polarization-sensitive; when the polarization state changes, the image quality deteriorates significantly. Furthermore, the transmission efficiency of optical signals is also limited, affecting the signal-to-noise ratio. These problems make it difficult to obtain stable, high-quality images of neural activity under free-movement conditions, limiting the system's application in behavioral neuroscience. However, the surface phase structure constructed using a polarization-insensitive dielectric cell array solves the problems of polarization sensitivity and signal transmission efficiency. Specifically, the special positional design of the objective lens ensures efficient transmission of optical signals; the polarization-insensitive dielectric cell array enables the system to maintain stable image quality under free-movement conditions, avoiding signal fluctuations caused by polarization changes.

[0075] Exemplary method for manufacturing a superlens: As mentioned above, superlenses, as a novel optical element, exhibit great application potential in miniature imaging devices due to their ultra-thin, lightweight, and high-performance characteristics. However, existing superlens structures suffer from significant reductions in edge resolution and limited effective field of view in practical applications, resulting in insufficient performance in scenarios requiring large field of view and high resolution, such as imaging of freely behaving animals.

[0076] In practical applications, the aforementioned superlens, designed based on a polarization-insensitive cell library, primarily eliminates the impact of cable bending during the imaging process. However, when the imaging probe is positioned on the imaging object, the movement of the object itself can also affect the superlens's performance.

[0077] The following section explains the impact of the imaging object on the superlens, based on the specific mechanism of the superlens: As previously described, a superlens is a planar optical element composed of subwavelength nanostructures. It is generally used to achieve precise phase modulation of the light field, should have high transmittance and low aberrations, and should be fabricated using semiconductor processes. In some embodiments, titanium dioxide can be used to fabricate the superlens; however, this application does not limit the use of other feasible materials (such as silicon nitride (Si3N4)).

[0078] The lens group used to construct a traditional objective lens is often an optical system composed of multiple traditional refractive lens elements. It is generally used to achieve specific optical functions, such as focusing and imaging, and should have good aberration correction capabilities.

[0079] In this application, the light field is a physical quantity describing the propagation state of light waves in space, including characteristics such as amplitude, phase, and polarization. It can be used to describe the objects that need to be adjusted in the aforementioned superlenses and lens groups. It is generally used to accurately describe the propagation characteristics of light waves and can be used to analyze and design optical systems. In some embodiments, the light field can be a plane wave; in other embodiments, it can be a spherical wave.

[0080] Superlenses and lens groups modulate the light field differently. A superlens modulates the input light field through phase modulation to create the desired output light field. A lens group modulates the input light field through refraction.

[0081] When the same input light field illuminates both a superlens and a lens group, both produce the same output light field. This is because the superlens simulates the optical function of a traditional lens group through phase modulation of its subwavelength structure. The single-layer structure of the superlens gives it the advantages of being ultrathin, lightweight, and easy to integrate, making it particularly suitable for miniaturized optical systems.

[0082] However, considering the different optical principles, superlenses often require a relatively stable operating position. If there is any offset, its mechanism of action on the light field may change, thus severely degrading its modulation performance.

[0083] Specifically, a superlens consists of a large number of subwavelength nanostructures (called cells). Each cell achieves a specific phase delay through specific geometric parameters (such as height, width, and shape). When light passes through these nanostructures, light at different locations receives different phase delays, thus forming the desired wavefront. However, when the superlens is misaligned in application, the cells may mismatch with the light field, thus failing to achieve its intended imaging effect.

[0084] To avoid this, superlenses can be formed on limiting structures in applications, which constrain the superlens's position during imaging. However, when using freely behaving animals as imaging subjects, considering the animal's autonomous movement, even with the aforementioned limiting structures, displacement can easily occur, thus affecting image quality.

[0085] When a superlens is used in an imaging device that requires imaging of free-behaving animals (such as the aforementioned imaging probe), the assembly error of the superlens itself, combined with the free movement of the animal, makes the superlens's offset uncontrollable. Due to its high NA characteristic, this will significantly affect the imaging effect (such as a loss of more than 50% in lateral resolution at the edge and a limited effective field of view), and may not be able to meet the imaging needs of free-behaving animals.

[0086] This application finds that traditional superlens designs only consider the optical performance at an ideal position, without taking into account errors such as lateral eccentricity, axial spacing, pitch and yaw angles that exist during actual assembly. This means that certain redundancy in traditional superlens designs may not meet actual imaging requirements, especially the imaging requirements of high-NA systems on moving objects.

[0087] To address this technical problem, this application determines the desired transfer function based on the expected optical function of the superlens in the imaging device, and performs offset sampling within the assembly error range (including lateral eccentricity range, axial spacing range, pitch range, and yaw angle range) to determine multiple perturbation positions, verifying that the phase modulation structure satisfies the desired transfer function under all perturbation positions. This design method ensures that the superlens maintains high optical performance under actual assembly conditions.

[0088] To further illustrate this design method, this application presents an exemplary flowchart of a superlens structure manufacturing method that takes into account the range of assembly errors. Figure 5 ).

[0089] Figure 5 The superlens structure manufacturing method P500 shown can be used to design and manufacture the superlens structure in the aforementioned imaging probe. For example... Figure 5 As shown, P500 may include the following sub-steps: S510. Determine the expected transfer function of the superlens structure to the input light field based on the expected optical function of the superlens structure in the imaging device.

[0090] S520. Determine the target phase modulation structure that satisfies the desired transfer function from the cell library based on multiple perturbation positions.

[0091] S530, a superlens structure is fabricated using semiconductor technology based on the target phase modulation structure.

[0092] In S510, the desired optical function is generally characterized by quantifiable optical parameters that represent the performance requirements of the imaging system for the superlens structure. For example, in an imaging device that requires imaging of freely behaving animals, when the superlens structure is used as the objective lens, the desired optical function may include achieving a high numerical aperture of NA=0.48 and a center lateral resolution of 1.17 μm. The input light field can reflect the light field entering the superlens structure, and the aforementioned desired optical function can also be characterized as a mapping condition (also denoted as the desired optical response) from the input light field to the desired output light field (i.e., the desired output light field), so that the superlens structure constructed based on this desired optical function can achieve the corresponding function.

[0093] In practical applications, the aforementioned desired optical functions can be configured according to the actual needs of the superlens structure. For example, in the aforementioned optical path, if the superlens structure needs to transmit both laser light and optical signals, then its desired optical functions include the processing requirements of the laser light and the transmission requirements of the optical signals. That is, when executing the aforementioned S510, at least two desired optical responses in at least two transmission optical paths of the superlens structure can be determined. The desired optical responses correspond one-to-one with the transmission optical paths, including the input optical field and desired transfer function in the corresponding transmission optical path.

[0094] In some embodiments, considering the potential joint requirements (such as polarization state, transmittance, etc.) of optical paths in different directions, the multi-path joint constraints of the superlens structure can be determined based on at least two desired optical responses. These multi-path joint constraints (such as transmittance) are used to screen the geometry within the cell library. In practical applications, a superlens objective constructed based on these constraints can achieve a 94.7% transmittance at 920 nm and a 74.2% transmittance at 560 nm.

[0095] Specifically, in practical applications, the aforementioned expected transfer function includes a first expected transfer function in the laser optical path and a second expected transfer function in the fluorescence optical path. The first expected transfer function corresponds to the input light field of the scanning image plane of the nonlinear optical imaging device, and reflects the focal plane requirements of the nonlinear optical imaging device within the imaging object. The second expected transfer function corresponds to the input light field of the optical signal at the focal position within the focal plane based on nonlinear optical effects, and reflects the detector's requirements for acquiring the optical signal.

[0096] In some embodiments, considering that the nonlinear optical depth imaging performed in this application is affected by interference from the imaging medium, compensation for the imaging medium can be introduced in advance during constraint to cancel out the interference and form a stable focal plane. That is, when performing the aforementioned S510, the actual input light field of the superlens structure in the imaging device and the desired output light field in the imaging medium can be determined first. Then, the desired transfer function is determined based on the imaging medium and the desired output light field. The desired transfer function reflects the output light field under conditions consistent with the input light field medium, including medium compensation for the output light field based on the imaging medium.

[0097] In addition, the aforementioned Figure 5 The designed superlens structure can be a coupling of one or more superlens structures. For example, when the superlens structure refers to both a scanning lens and an objective lens, its input light field is the output of the scanning galvanometer, and the desired output light field is the focal position within the focal plane corresponding to each input light field. As another example, when the superlens structure refers to an objective lens, the aforementioned scanning lens can modulate the output of the scanning galvanometer, so that the input light field of the superlens structure is input at different angles.

[0098] In the aforementioned S520, the perturbation positioning can reflect the assembly error of the superlens structure on the limiting structure and the dynamic error of the limiting structure as it moves with the imaging object. However, from an overall perspective, the assembly error of the limiting structure has already limited the range of the dynamic error of the limiting structure as it moves with the imaging object. Therefore, the perturbation positioning in this application is constructed based on the assembly error. This assembly error can include the range of lateral eccentricity, the range of axial spacing, the range of pitch, and the range of yaw angle.

[0099] For example, in some embodiments, the limiting structure may have a lateral eccentricity range of ±5μm, an axial spacing range of ±0.01mm, a pitch range, and a yaw angle range of ±0.02°.

[0100] Based on the aforementioned assembly errors, multiple perturbation positions can be determined within the range of assembly errors to reflect the assembly status of the superlens structure under different conditions. Based on these perturbation positions, the phase modulation structure (i.e., the target phase modulation structure) that can still satisfy the desired transfer function under different perturbation positions can be determined from the cell library.

[0101] In practice, this process can be iterative. First, an intermediate phase modulation structure satisfying the desired transfer function at the reference position can be determined from the cell library. Then, multiple test transfer functions of the intermediate phase modulation structure with respect to the input optical field under the multiple perturbation positions can be determined.

[0102] For the aforementioned transfer function to be verified, the intermediate phase modulation structure can be updated based on the transfer function to be verified if the transfer function to be verified does not match the expected transfer function. Alternatively, the intermediate phase modulation structure can be used as the target phase modulation structure if the transfer function to be verified matches the expected transfer function. This allows for iterative determination of the target phase modulation structure.

[0103] As mentioned above, the perturbation positions are constructed based on assembly errors, thus the assembly errors of the superlens structure within the corresponding limiting structure can be determined during testing. Then, offset sampling is performed within each error range of the assembly errors to determine the multiple perturbation positions.

[0104] In some embodiments, considering that subsequent processing techniques may also have certain errors, processing errors can be accommodated in the aforementioned design process. That is, multiple phase modulation structures to be tested can be determined based on the intermediate phase modulation structure and the processing errors. Then, the to-be-tested transfer function of the candidate phase modulation structure among the multiple to-be-tested phase modulation structures under the candidate positions among the multiple perturbation positions is determined, thereby determining multiple to-be-tested transfer functions.

[0105] In the aforementioned S530, the target phase modulation structure determined in S520 can serve as a layout, thereby enabling the fabrication of a superlens structure using semiconductor technology. For example, cells in the layout can be formed through an etching process on a semiconductor substrate (such as a titanium dioxide substrate or a titanium dioxide epitaxial layer based on a conventional substrate). The cell height can be 1500 nm.

[0106] In practical applications, this application can decouple the superlens based on this design method, so that it can realize the overall desired function within the range supported by the cell. To further illustrate this process, this application also provides an exemplary flowchart of a method for configuring the desired transfer function (…). Figure 6 ).

[0107] like Figure 6 As shown, process P600 may include the following steps: S610. Determine the actual input light field and the actual desired transfer function of the superlens structure in the imaging device.

[0108] S620. In response to the fact that the modulation bandwidth of the superlens structure does not meet the actual expected transfer function, the superlens structure is adjusted to a superlens structure group containing at least two superlenses based on the modulation bandwidth, so that the overall modulation bandwidth of the superlens structure group covers the actual expected transfer function.

[0109] S630. Based on the number of superlenses in the superlens structure group, at least one relay transfer function is determined between the actual input light field and the actual desired transfer function.

[0110] S640. Determine the input light field and desired transfer function of each superlens in the superlens structure group based on the actual input light field, the actual desired transfer function, and at least one relay transfer function.

[0111] In the aforementioned S610, the actual expected transfer function reflects the optical function that the superlens needs to achieve under real working conditions. It is used to describe the actual imaging requirements, including the requirements for changes in the input and output light fields, and other imaging parameter requirements (such as field of view, resolution, and depth requirements). The actual input light field can refer to the characteristics of the light field received by the superlens under real working conditions, and is used to reflect the actual working conditions (i.e., the actual input of its light field).

[0112] In the aforementioned S610, the actual desired transfer function and the actual input optical field can be determined based on the actual operating conditions of the superlens structure. See the relevant content on page 500 above for details.

[0113] In the aforementioned S620, the modulation bandwidth refers to the combined capability of the phase modulation range and accuracy achievable by the superlens structure, reflecting its phase modulation capability. Specifically, it can be characterized by various optical indicators. When its optical indicators meet the device requirements, the superlens structure can be considered to have the corresponding adjustment capability to achieve the modulation bandwidth required for that scenario.

[0114] When implementing the aforementioned S620, the design can be based on existing parameters, and its optical performance can be determined through implementation to see if it meets the requirements (e.g., ...). Figure 4 (This allows us to) determine whether the bandwidth is being adjusted.

[0115] When the modulation bandwidth does not meet the actual expected transfer function, it indicates that a single superlens structure cannot match the actual expected transfer function, and the actual expected transfer function should be split.

[0116] Based on the aforementioned S620, the aforementioned S630 can realize the decomposition of the actual desired transfer function, which can be achieved through a relay transfer function. Here, the relay transfer function refers to the intermediate optical function used to connect the various layers of the superlens in the design of a multilayer superlens structure. At the design level, it should simplify the design of each layer while maintaining overall optical performance to achieve high resolution and a large field of view imaging.

[0117] In the aforementioned superlens structure, the modulation of the input light field can be decoupled from the modulation of the output light field, so that the relay transfer function is a light field distribution of a specific shape that is parallel light or other light field that is easy to modulate by the subsequent superlens structure.

[0118] In some embodiments, the relay transfer function can also be determined based on aberrations, and the aberrations that the actual expected transfer function needs to adjust are split so that each relay transfer function only needs to adjust one class of aberration.

[0119] Specifically, in the aforementioned imaging probe, the superlens structure of the scanning lens is responsible for optical path compression to form a parallel incident light field. The first superlens objective (i.e., the upstream superlens) is responsible for aberration correction. The second superlens objective is used for phase modulation to achieve beam focusing and imaging functions, thereby realizing the desired transfer function overall.

[0120] Therefore, based on the aforementioned decomposition, in the aforementioned S640, the entire design task can be divided into multiple design tasks based on the actual input light field, the actual desired transfer function, and at least one relay transfer function, thereby simplifying the settings based on the input light field and desired transfer function of the superlens. For example, when the superlens structure is split into two, the input light field after the first superlens structure upstream of the optical path can be the actual input light field, and the desired transfer function is the mapping from the actual input light field to the relay transfer function. The input light field of the second superlens structure is the relay transfer function.

[0121] All the above-mentioned optional technical solutions can be combined in any way to form the optional embodiments of this application, and will not be described in detail here. For example, the superlens structure of the aforementioned scanning lens can be separated and combined with the aforementioned double superlens structure of the objective lens to meet practical requirements.

[0122] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0123] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0124] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0125] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0126] It should be noted that in the description of this application, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0127] It should be noted that, in this application, "miniaturization" means that the multiphoton microscopy system has little impact on the activity of the observed living organism during observation. For example, when the multiphoton microscopy system is fixed on the living organism to be observed, the living organism can still move freely.

[0128] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications or equivalent substitutions made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An imaging probe, characterized in that, The imaging probe is used in an imaging device based on nonlinear optical imaging, and the imaging probe includes a housing and a depth imaging device based on nonlinear optics. One end of the housing is provided with a first port for fixed connection with the object to be tested; The depth imaging device includes a laser source and a scanning galvanometer, a scanning lens and an objective lens arranged sequentially along the laser optical path, wherein the objective lens includes at least one superlens structure. The laser emitted by the laser source passes sequentially through the scanning galvanometer, the scanning lens, and the objective lens, and is focused through the first port onto the scanning position corresponding to the scanning angle of the scanning galvanometer at the internal focal plane of the object under test, thereby triggering a nonlinear optical effect; The optical signal generated by the nonlinear optical effect is collected through the first port and transmitted to the detector.

2. The imaging probe according to claim 1, characterized in that, The objective lens includes a first superlens and a second superlens arranged sequentially along the laser optical path.

3. The imaging probe according to claim 1, characterized in that, The scanning lens is a scanning superlens, used to adjust the laser light passing through the scanning galvanometer so that the laser light forms an energy-equilibrium planar image before entering the objective lens.

4. The imaging probe according to claim 1, characterized in that, The scanning lens is a scanning superlens, and the objective lens includes a first superlens and a second superlens arranged sequentially along the laser optical path.

5. The imaging probe according to claim 2 or 4, characterized in that, The first superlens is disposed on the incident side of the second superlens; the surface phase structure of the first superlens is configured based on the object under test and is used to pre-compensate the laser to collimate the wavefront of the laser at the internal focal plane.

6. The imaging probe according to claim 5, characterized in that, The objective lens is positioned at the first port, and the optical signal is collected and transmitted to the detector through the first and second superlenses in the objective lens. The surface phase structures of the first and second superlenses are constructed based on a polarization-insensitive dielectric cell array to transmit the optical signal.

7. The imaging probe according to claim 5, characterized in that, The surface phase structure of the first superlens is also based on the aperture surface configuration of the second superlens to adjust the laser light into parallel light within the aperture surface of the second superlens.

8. The imaging probe according to claim 1, characterized in that, The depth imaging device includes a limiting structure arranged along the laser optical path for assembling the objective lens and the scanning lens.

9. The imaging probe according to claim 8, characterized in that, The objective lens and the scanning lens are designed with assembly tolerance based on the limiting structure to maintain the laser optical path.

10. An imaging device based on nonlinear optical imaging, characterized in that, The imaging device includes: The imaging probe according to any one of claims 1 to 9; A laser for generating and transmitting laser light to the imaging probe; and A detector is used to detect the optical signals acquired by the imaging probe.

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