A confocal microscopic imaging system based on a fiber bundle and a fiber rotary joint

Abstract

The application discloses a confocal microscopic imaging system based on a fiber bundle and a fiber rotary joint, and belongs to the technical field of optical microscopic imaging. In order to overcome the low transmission efficiency of excitation light and the poor thermal stability of the existing rotary disc confocal system, the application provides a "fiber direct injection" rotary disc. One end of the polished fiber bundle is connected with an excitation light source through a fiber rotary joint. The other end of the fiber bundle is independently tapered and accurately aligned and filled into each pinhole of the pinhole array rotary disc. After the excitation light is emitted from the fiber, the excitation light directly passes through the pinhole and is focused on the sample by the objective lens without a microlens array. This design enables the excitation light to be directly introduced into the pinhole without loss, improves the excitation light coupling efficiency to more than 90%, reduces heat generation from the source, and thus realizes high excitation efficiency and excellent long-term focal point stability, and is particularly suitable for long-term high-resolution imaging of living samples.

Description

Technical Field

[0001] This invention relates to the field of optical microscopy imaging technology, specifically to a confocal microscopy imaging system, and more particularly to a rotary confocal microscopy imaging system that utilizes fiber bundles and fiber rotation joints to improve the excitation light transmission efficiency and long-term thermal stability from a physical perspective. Background Technology

[0002] Confocal microscopy, with its high resolution and optical slicing capabilities, has become a key tool in fields such as life sciences. Among them, rotating confocal microscopy, with its high-speed parallel imaging characteristics, is particularly suitable for dynamic observation of living samples. However, the performance of this technology has always been limited by a fundamental physical bottleneck—the excitation light cannot be efficiently coupled to the high-speed rotating micron-sized pinhole, resulting in the waste of most of the light energy and overheating of the rotating disk. Both of the existing mainstream turntable technologies have certain inherent efficiency drawbacks: 1. Dual-disk microlens focusing schemes (such as the Yokogawa CSU series and Andor Dragonfly): The core of this scheme involves pre-focusing the excitation light through microlenses on a microlens turntable to a pinhole on a pinhole array turntable. However, this "free-space focusing-coupling" process is limited by diffraction and geometric obstruction. Approximately 60%-70% of the excitation light's energy is lost when passing through the core "microlens-pinhole" rotating coupling module, resulting in an actual transmission efficiency of only about 30%-40% or higher. The best-optimized Andor Dragonfly claims a microlens coupling efficiency of 60%. This inefficiency of the core module lays the foundation for the overall system's low light energy utilization. More seriously, the blocked and absorbed laser energy is converted into heat, causing thermal deformation of the turntable and support structure, leading to image focus drift and affecting the stability of long-term observations. 2. Single-disc wide-field illumination solution (a domestically produced disc confocal product): While this solution simplifies the structure, returning to the design of the Nipkow disc when it was invented, it faces a more severe "fill factor" limitation. Over 98% of the excitation light is directly blocked by the non-light-transmitting area between the pinholes (e.g., a 50µm diameter pinhole with a 250µm spacing), resulting in significant energy waste and generating substantial parasitic heat, making thermal management a more challenging task. In summary, regardless of the specific technical approach described above, the essence is to address the matching problem between static light and rotating microapertures in a free-space optical path. This leads to a significant "free-space optical coupling bottleneck" and its resulting thermal stability challenges, particularly with single-disk solutions. This not only results in the inefficient consumption of expensive laser energy but also forces the system to use high-power lasers and bear the associated risks of thermal drift and phototoxicity, severely limiting the application of this technology in cutting-edge scenarios such as long-duration, high-precision live-body imaging. Summary of the Invention

[0003] (a) Purpose of the invention To completely solve the aforementioned "free-space optical coupling bottleneck" and its resulting system thermal stability problems, this invention aims to provide a confocal imaging system based on an optical fiber bundle and an optical fiber rotary joint. This invention abandons the traditional external illumination approach and adopts a novel turntable design where the optical fiber is directly injected into the pinhole. This design aims to directionally deliver almost all of the excitation light to the sample, thereby theoretically achieving a step-wise increase in excitation efficiency, theoretically exceeding 90%. It also fundamentally reduces ineffective photothermal conversion, significantly improving the system's focal stability during long-term observation, providing a foundation for obtaining ultra-high-speed imaging with higher signal-to-noise ratios, lower phototoxicity, and better stability. Simultaneously, it reduces the power requirements of the light source, lowering the system cost. (II) Technical Solution To achieve the above objectives, the core of the technical solution of this invention is to construct a direct optical path from the laser source to the focal plane of the sample without free space loss, and to actively manage potential thermal effects. The system includes: an excitation source, a beam shaping unit, an excitation filter turntable, a dichroic mirror turntable, an optical fiber rotation joint, a special optical fiber bundle assembly, a pinhole array turntable, an objective lens, an emission filter turntable, a converging lens, an area array detector, a system control unit, an active thermal management module, a focal position detection unit, and a piezoelectric ceramic nanopositioner. Its core innovation lies in the special optical fiber bundle assembly and its connection to other parts of the optical path, as well as the integrated thermal stabilization module. The excitation source is a single-wavelength laser or a combination of multiple-wavelength lasers, with a wavelength range from 350nm to 1550nm. The beam shaping unit consists of multiple lenses and beam homogenizing devices, used to expand, combine, and homogenize the laser output from the laser. The excitation filter turntable includes multiple excitation filters, which are driven by an electric device to achieve rapid switching. The dichroic mirror turntable includes multiple dichroic mirrors, each with a dichroic optical thin film coated on one side and an anti-reflective coating coated on the other side, and is driven by an electric device to achieve rapid switching. The emission filter turntable includes multiple emission filters, which are driven by an electric device to achieve rapid switching. The optical fiber rotating joint is divided into two parts: a static end and a rotating end. The static end is used to stably receive excitation light, and the rotating end is connected to the integrated end of the special optical fiber bundle assembly. The rotating end is driven by an electric device to achieve high-speed rotation, with a maximum speed of 20,000 revolutions per minute. The aforementioned special fiber bundle assembly is composed of multiple integrated optical fibers. One end (the integrated end) is tightly bundled and polished, and seamlessly connected to a static excitation light source via a fiber rotation joint, achieving high reliability of light transmission during rotation. At the other end (the dispersed end), each fiber is independently tapered, with its light-emitting end face precisely matched and filled one-to-one with the pinhole array on the pinhole array turntable in terms of spatial position and diameter. Excitation light emitted from the tapered end of the fiber passes directly through the pinhole and is focused onto the sample by the objective lens, without needing to pass through any microlens array. The area array detector is an sCMOS or EMCCD camera with a frame rate not exceeding 3,000 fps. The motor is a brushless DC motor with an encoder for transmitting the motion status information of the turntable to the system control unit. The motor speed is not less than 15,000 rpm, the motor speed stability is not greater than ±0.1%, the motor dynamic response is less than 1 second (speed accelerates from standstill to 15,000 rpm), and the motor working life MTBF is greater than 20,000 hours. Furthermore, the system also includes an active thermal management device and a closed-loop focus maintenance system. The active thermal management device is located in the critical area of ​​the fiber optic coupling and is used to detect the temperature of this area in real time and maintain the temperature of this area in a suitable and stable state for long-term operation through a cooling device; the closed-loop focus maintenance system includes a focus position detection unit and a piezoelectric ceramic nanopositioner for real-time monitoring and compensation for focus drift. Furthermore, the system can switch between three modes: confocal imaging, wide-field imaging, and extended structured light illumination super-resolution imaging. During operation, the excitation light passes through the beam shaping unit, then sequentially through the excitation filter turntable and the dichroic mirror turntable, and finally is efficiently transmitted to the special fiber bundle assembly via the fiber rotation joint. Each tapered fiber is then directly guided into the pinhole of the aligned pinhole array turntable. This transforms the function of the pinhole from a "selective aperture" to a "light guide," theoretically increasing the transmission efficiency of the excitation light from the source to the pinhole to over 90%. This fundamentally eliminates the limitations of free-space coupling due to diffraction, obstruction, and fill factor, while also eliminating the main heat source at its origin. (III) Beneficial Effects Compared with the prior art, the present invention has the following significant advantages: 1. Fundamental breakthrough and efficiency revolution: It directly bypasses the "free space optical coupling bottleneck" and improves the efficiency of delivering excitation light to the pinhole from a few percent to tens of percent in the existing technology to a theoretical level of over 90%, achieving an order-of-magnitude improvement. 2. Simplified Structure and High-Efficiency Optical Path: The complex microlens array of the traditional dual-rotor design is eliminated, resulting in a simpler optical path. Excitation light travels directly from the optical fiber to the pinhole, ensuring a direct energy transmission path with minimal loss and completely resolving the mismatch problem associated with dual-rotor designs. 3. Fundamentally Improved Thermal Stability: Due to the efficient utilization of excitation light, the ineffective light power that is blocked and absorbed by the pinhole array turntable and converted into heat is reduced by more than 80%. This fundamentally alleviates the thermal deformation and focus drift caused by turntable heating in traditional systems, providing an inherent advantage in thermal stability for long-term, high-precision live imaging. 4. Comprehensive performance gains: At the same laser power, significantly stronger fluorescence signal and signal-to-noise ratio can be obtained, or higher imaging speed and deeper penetration depth can be achieved; to achieve the same imaging quality, the required laser power can be reduced significantly (by more than an order of magnitude). 5. Excellent active system stability: By integrating active thermal management and closed-loop focus maintenance technology, the system can actively suppress residual thermal disturbances and environmental drift, achieve nanometer-level focus locking, and has excellent environmental robustness and ultra-long-term working stability. Attached Figure Description Figure 1 This is an overall block diagram of the system of the present invention. Figure 2 This is a schematic diagram of the optical path structure of the system of the present invention. Figure 3 This is a partially enlarged schematic diagram of a fiber optic rotary joint, a special fiber bundle assembly, and a pinhole array turntable. Figure 4 This is a magnified schematic diagram of a pinhole. Detailed Implementation To make the objectives, technical solutions, and advantages of the present invention clearer, a detailed description is provided below in conjunction with the accompanying drawings and embodiments. The present invention is not limited to the specific details described below. Example: A highly stable rotary confocal microscope based on fiber bundles and fiber optic rotary joints 1. System Overall Architecture and Optical Path Flow Reference Figure 1 and Figure 2 This system adopts a modular design, and its core innovation lies in replacing the traditional free-space illumination optical path with an optical fiber path. The system workflow is as follows: The excitation light output from the excitation source (1) passes through the beam shaping unit (2), then through the excitation filter turntable (3), and directly through the dichroic mirror turntable (4) before being coupled into the static input port of the fiber optic rotary joint (5). This fiber optic rotary joint (5) is the key to realizing continuous, low-loss (typical insertion loss <1.0 dB) transmission of optical signals in the rotating state. Its rotating output end is permanently connected to and precisely aligned with the integrated input end of the special fiber bundle assembly (6). Driven by a motor (7), the entire special fiber bundle assembly (6) rotates in strict synchronization with the pinhole array turntable (8). Each tapered fiber at the dispersed end of the special fiber bundle assembly (6) injects its excitation light directly into a corresponding pinhole on the pinhole array turntable (8). After the excitation light is emitted from the pinhole, it is focused onto the focal plane of the sample by the objective lens (9). The fluorescence generated by the sample upon stimulation is collected by the same objective lens (9), passes through a pinhole (which acts as a spatial filter), enters a special fiber bundle assembly (6) through the dispersion end, passes through the fiber rotation joint (5), and is reflected by the dichroic mirror disk (4) into the fluorescence detection optical path. After passing through the emission filter disk (10) and the converging lens (11), it is clearly imaged on the area array detector (12). The system control unit (13) coordinates the motor drive, laser modulation, and camera exposure to ensure that the image acquisition and scanning positions are synchronized. 2. Technical details of key components 2.1 Fabrication and characteristics of special fiber bundle assembly (6) according to Figure 3 and Figure 4 As shown, this component is the core element of the present invention, and its fabrication involves precision optical processes: Fiber selection and integration: The fiber bundle consists of thousands to tens of thousands of multimode fibers arranged in a regular pattern. All fibers are tightly packed at the integration end, and are ground and polished to form an optical quality end face, with an anti-reflection coating applied to the entire bundle. Distributed-end tapering and positioning: Each fiber at the distributed end undergoes customized tapering to reduce its output diameter to the target size (e.g., 25μm, 50μm) to match the pinhole diameter. After tapering, all fiber output ends are precisely positioned and fixed in a special fixture according to a preset pattern, ensuring that their spatial position maintains micron-level alignment accuracy with the target pinhole array under rotational dynamics. Optical energy transmission efficiency: The transmission loss of a single fiber bundle prepared by the above process can be less than 0.5 dB from the integrated end to the tapered output end. 2.2 Pinhole Array Turntable (8) and Matching Design The pinhole array is formed on optical glass using a laser ablation process, arranged in a multi-column spiral pattern. The spatial arrangement of the fiber bundle's dispersive ends must strictly conform to this spiral equation. The turntable can contain up to 12 complete pinhole arrays covering the entire field of view of the objective lens. The pinhole array turntable is driven by a high-speed motor, rotating synchronously with the rotation of the special fiber bundle assembly. 3. Thermal Management and Focus Stability Enhancement Implementation Plan To address the challenge of thermal drift in microscopic imaging, this invention integrates the following enhancement methods: Active thermal management module (14): An active heat dissipation device, such as an attached thermoelectric cooler, is provided near the housing of the optical fiber rotating joint (5) and the integrated end of the special optical fiber bundle assembly (6). This module is used to actively dissipate the concentrated heat generated at the optical fiber coupling point and prevent it from being conducted to the core imaging optical path. Closed-loop focus maintenance system: This system includes a focus position detection unit (15) and a piezoelectric ceramic nanopositioner (16). The focus position detection unit (15) uses a low-power infrared monitoring beam to detect focus drift in real time by analyzing the spot shift reflected from the sample-cover glass interface (the detection accuracy can reach the nanometer level). The generated error signal is fed back to the system control unit (13), which drives the piezoelectric ceramic nanopositioner (16) of the objective lens (9) to perform real-time displacement compensation, thereby dynamically maintaining a constant focus position. Low thermal expansion mechanical design: The support frame and main optical substrate of the pinhole array turntable (8) are made of materials with low thermal expansion coefficient (such as Invar alloy) to passively suppress the influence of ambient temperature fluctuations. The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A confocal microscopy imaging system based on fiber bundle and fiber rotation joint, comprising an excitation source, a beam shaping unit, an excitation filter turntable, a dichroic mirror turntable, a pinhole array turntable, a fiber rotation joint, a special fiber bundle assembly, an objective lens, a motor, an emission filter turntable, a converging lens, an area array detector, a system control unit, an active thermal management module, a focal position detection unit, and a piezoelectric ceramic nanopositioner; The special fiber bundle assembly consists of thousands to tens of thousands of optical fibers bundled together. One end is an integrated end, where all fiber end faces are coplanarly polished for optical coupling. The other end is a distributed end, where each fiber is independently processed into a tapered shape to form a tapered output end. The spatial distribution of all tapered output ends is consistent with the pinhole array distribution on the pinhole array turntable. Each tapered output end is configured to maintain dynamic alignment with a corresponding pinhole during rotation, allowing excitation light to be directly transmitted from inside the fiber and injected into the pinhole, and then focused onto the sample via the objective lens. The optical fiber rotating joint is divided into two parts: a static end and a rotating end. The static end is connected to the output of the dichroic mirror turntable, and the rotating end is fixedly connected to the integrated end of the special optical fiber bundle assembly and optically aligned. The rotating end is connected to the integrated end of the special optical fiber bundle assembly, and the rotating end is driven by an electric device to achieve high-speed rotation, with a maximum speed of 20,000 revolutions per minute. The excitation source is a single-wavelength laser or a combination of multiple-wavelength lasers, with a wavelength range from 350nm to 1550nm; The beam shaping unit consists of multiple lenses and beam homogenizing devices, and is used to expand, combine and homogenize the laser output from the laser. The excitation filter turntable includes multiple excitation filters, which are driven by an electric device to achieve rapid switching; The dichroic mirror turntable includes multiple dichroic mirrors, each with a dichroic optical thin film coated on one side and an anti-reflective coating coated on the other side, and is driven by an electric device to achieve rapid switching. The emission filter turntable includes multiple emission filters, which are driven by an electric device to achieve rapid switching; The area array detector is an sCMOS or EMCCD camera with a frame rate not exceeding 3,000 fps; The motor is a brushless DC motor equipped with an encoder to transmit the turntable's motion status information to the system control unit. The motor speed is no less than 15,000 rpm, the motor speed stability is no greater than ±0.1%, the motor dynamic response is less than 1 second (acceleration from standstill to 15,000 rpm), and the motor's MTBF is greater than 20,000 hours.

2. The confocal microscopy imaging system based on fiber bundle and fiber rotation joint according to claim 1, characterized in that, It also includes an active thermal management device, which is located near the integrated end of the fiber optic rotary joint and / or the special fiber bundle assembly, for dissipating heat from the parts.

3. The confocal microscopy imaging system based on fiber bundle and fiber rotation joint according to claim 1, characterized in that, It also includes a closed-loop focus maintenance system, which includes a focus position detection unit and a piezoelectric ceramic nanopositioner; the focus position detection unit is used to monitor the position drift of the sample focal plane in real time; the piezoelectric ceramic nanopositioner drives the objective lens or sample stage to perform position compensation based on the monitoring results.

4. The confocal microscopy imaging system according to claim 1, characterized in that, The support structure of the system that supports the pinhole array turntable is made of a material with a low coefficient of thermal expansion.

5. A confocal microscopy imaging system based on an optical fiber bundle and an optical fiber rotation joint according to claim 1, characterized in that, The optical fibers in the special optical fiber bundle assembly are multimode optical fibers, and the number of fibers does not exceed 35,000.

6. A confocal microscopy imaging system based on an optical fiber bundle and an optical fiber rotation joint according to claim 1 or 6, characterized in that, The diameter of the light-emitting surface of the tapered output end is less than or equal to the diameter of the pinhole it is aligned with, which is 20μm-500μm.

7. A confocal microscopy imaging system based on an optical fiber bundle and an optical fiber rotation joint according to claim 1, characterized in that, The pinholes on the pinhole array turntable are arranged in multiple spiral lines, and the tapered output ends of the dispersed end are arranged in a matching spiral pattern accordingly.

8. A confocal microscopy imaging system based on an optical fiber bundle and an optical fiber rotation joint according to claim 1, characterized in that, It also includes a system control unit, which is used to synchronously trigger the exposure of the area array detector according to the real-time rotation phase of the pinhole array turntable, and control the speed of the motor.

9. A confocal microscopy imaging system based on an optical fiber bundle and an optical fiber rotation joint according to claim 1, characterized in that, The system does not include a microlens array located on a pinhole array turntable.

10. A confocal microscopy imaging system based on an optical fiber bundle and an optical fiber rotation joint according to claim 1, characterized in that, The system can switch between three modes: confocal imaging, wide-field imaging, and extended structured light illumination super-resolution imaging.

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