Full-field OCT system based on orthogonal birefringent liquid crystal phase compensation, imaging method and medium

Abstract

The application provides a full-field OCT system based on orthogonal double liquid crystal phase compensation, an imaging method, equipment and a medium, and comprises the following steps: a broadband light source module is used to provide broadband illumination light with a low coherence length; a light splitting module is used to make the broadband illumination light enter a reference arm and a sample arm according to a predetermined proportion; the reference arm is sequentially provided with a first liquid crystal phase modulation component, a first wave plate, a first microscope objective and a fixed reference mirror; the sample arm is sequentially provided with a second liquid crystal phase modulation component, a second wave plate, a second microscope objective and a sample to be measured; a detection module is used to receive an interference signal of the reference arm reflected light and the sample arm backscattered light and to perform photoelectric conversion; and a control module is used to apply a differential driving voltage to the first liquid crystal phase modulation component and the second liquid crystal phase modulation component and to synchronously control a face array camera to collect, so as to solve the problems of stability and defocusing caused by mechanical phase shifting in the FFOCT system and low light energy utilization and dispersion mismatch caused by liquid crystal polarization dependence.

Description

Technical Field

[0001] This invention relates to the field of full-field optical coherence tomography (OCT) technology, and in particular to a full-field OCT system, imaging method, device, and medium based on orthogonal dual liquid crystal phase compensation. Background Technology

[0002] Full-field optical coherence microscopy (FF-OCM) is an advanced three-dimensional imaging technology in the field of optical imaging. It combines the depth penetration capability of optical coherence tomography (OCT) with the advantages of high-resolution microscopy. Based on the principle of low coherence interference, it acquires interference images through an area array camera and performs phase demodulation to obtain a frontal image parallel to the sample surface, eliminating depth-of-field limitations. When paired with a high numerical aperture optical system, it can achieve subcellular (<1μm) lateral resolution while also possessing high axial resolution. It provides an important tool for non-invasive observation of tissue microstructure and function in biomedical research and clinical applications. A conventional FFOCT system mainly consists of a low-coherence light source (such as a halogen lamp or LED), a beam splitter, a reference arm, a sample arm, a cylindrical lens, and an area array camera. In the reference arm, a piezoelectric ceramic (Lead Zirconate Titanate, PZT) drives the reference mirror to move to achieve phase modulation. The phase demodulation methods include the four-step phase shift method and the single-step phase shift method. Dynamic FFOCT (DFFOCT) requires continuous phase modulation.

[0003] Despite the numerous advantages of conventional FFOCT systems, significant technical bottlenecks remain in practical applications. Traditional methods rely on PZT mechanical phase shifting, whose mechanical jitter, hysteresis, and creep characteristics lead to phase shift errors, limiting imaging speed and stability. The shallow depth of field (micrometer-scale) of high numerical aperture objectives makes it prone to defocusing when the PZT drives the reference mirror axially, causing light intensity fluctuations and unstable interference fringe contrast. Liquid crystal variable retarders exhibit polarization dependence; direct use of natural light introduces background noise, while adding polarizers results in a loss of at least 50% of light energy. Under broadband light sources, single-sided liquid crystal device configurations or asymmetrical optical elements in both arms can cause dispersion mismatch, leading to degraded axial resolution and blurred images. These technical issues severely restrict the application of FFOCT systems in high-precision, high-speed, and high-sensitivity imaging scenarios, particularly in the biomedical field where the demands for weak signal detection and clear imaging of deep tissues remain unmet.

[0004] Therefore, there is an urgent need to develop a full-field OCT system based on orthogonal dual liquid crystal phase compensation to solve the stability and defocusing problems caused by mechanical phase shift in the FFOCT system, as well as the technical problems of low light energy utilization and dispersion mismatch caused by liquid crystal polarization dependence. Summary of the Invention

[0005] To overcome the problems existing in related technologies, this disclosure provides a full-field OCT system, imaging method, device and medium based on orthogonal dual liquid crystal phase compensation, so as to solve the technical problems of stability and defocusing caused by mechanical phase shift in the FFOCT system in related technologies, as well as the low light energy utilization and dispersion mismatch caused by liquid crystal polarization dependence.

[0006] This specification provides one or more embodiments of a full-field OCT system based on orthogonal dual liquid crystal phase compensation, including: A broadband light source module is used to provide broadband illumination light with low coherence length, which is collimated by a collimating lens group and output as parallel light. The beam splitting module is a non-polarizing beam splitter used to split the broadband illumination light into reference light and sample light according to a predetermined ratio, which then enter the reference arm and sample arm respectively. The reference arm is arranged in sequence along the direction of reference light propagation, including a first liquid crystal phase modulation component, a first waveplate, a first microscope objective, and a fixed reference mirror. The slow axis direction of the first liquid crystal phase modulation component is a first direction, and the slow axis direction of the first waveplate is a second direction perpendicular to the first direction. The sample arm is arranged sequentially along the sample light propagation direction, including a second liquid crystal phase modulation component, a second waveplate, a second microscope objective, and the sample to be tested. The second liquid crystal phase modulation component has the same material properties and thickness as the first liquid crystal phase modulation component, and the slow axis direction is the second direction. The second waveplate has the same parameters as the first waveplate, and the slow axis direction is the first direction. The detection module, including a tube lens and an area array camera, is used to receive the interference signal between the reflected light from the reference arm and the backscattered light from the sample arm and perform photoelectric conversion. The control module is electrically connected to the first liquid crystal phase modulation component, the second liquid crystal phase modulation component, and the detection module, and is used to apply differential driving voltage to the first liquid crystal phase modulation component and the second liquid crystal phase modulation component and synchronously control the area array camera to acquire data.

[0007] Preferably, the first direction is a horizontal direction and the second direction is a vertical direction; Both the first and second waveplates are 0th-order half-waveplates with a slow axis delay of λ / 2, where λ is the center wavelength of the broadband illumination light.

[0008] Preferably, the first liquid crystal phase modulation component and the second liquid crystal phase modulation component are nematic liquid crystal variable delay devices, and the delay adjustment range is 0~λ; The control module adjusts the delay value within the range of -λ / 2 to λ / 2, making the optical path difference between the two arms adjustable between -λ and λ.

[0009] Preferably, the control module is further configured as follows: A push-pull strategy is used to drive the first liquid crystal phase modulation component and the second liquid crystal phase modulation component; In the initial state, the phase delay generated by the first liquid crystal phase modulation component and the second liquid crystal phase modulation component is equal to the slow axis delay of the first waveplate and the second waveplate.

[0010] Preferably, the first waveplate and the first liquid crystal phase modulation component are optically bonded together as an integral structure, and / or the second waveplate and the second liquid crystal phase modulation component are optically bonded together as an integral structure; The slow axis of the first waveplate is orthogonal to the slow axis of the first liquid crystal phase modulation component, and the slow axis of the second waveplate is orthogonal to the slow axis of the second liquid crystal phase modulation component.

[0011] This specification provides one or more embodiments of a full-field OCT imaging method based on the above system, including the following steps: The control module applies at least one set of differential driving signals to the first liquid crystal phase modulation component and the second liquid crystal phase modulation component, so that the initial phase delay of both is set to a preset value and is consistent with the slow axis delay of the first waveplate and the second waveplate, thereby achieving static optical path balance of the two arms. The broadband illumination light emitted by the broadband light source module is split into reference light and sample light by the beam splitting module, and then enters the reference arm module and the sample arm module respectively. After the reference light is modulated by the first liquid crystal phase modulation component and compensated by the first waveplate, it is irradiated by the first microscope objective and reflected back. The sample light is modulated by the second liquid crystal phase modulation component to modulate the vertical polarization component and compensated by the second waveplate. Then, it is irradiated onto the sample under test through the second microscope objective and backscattered back. The control module adopts a push-pull differential driving strategy to adjust the delay of the first liquid crystal phase modulation component and the second liquid crystal phase modulation component so that the delay of the two components changes in opposite directions, thereby realizing synchronous phase modulation of horizontally polarized light and vertically polarized light. The returned reference light and sample light are combined by the beam splitting module and focused onto the area array camera through the tube lens. The area array camera simultaneously acquires interference images. The control module processes the acquired interference images to obtain high-resolution tomographic images of the sample under test.

[0012] Preferably, the method further includes the following steps: The delay of the first liquid crystal phase modulation component and the second liquid crystal phase modulation component is adjusted by the synchronous control and processing module so that the relative optical path difference between the horizontally polarized light and the vertically polarized light is λ / 2. A DC background image is acquired by an area array camera after complementary interference fringes are canceled. The DC background image is then subtracted from the original interferogram in subsequent image processing to eliminate false noise.

[0013] Preferably, the method further includes the following steps: Based on the average refractive index and imaging depth of the sample, the optical path deviation between the focal plane and the coherent gate is calculated. The delay of the first liquid crystal phase modulation component and the second liquid crystal phase modulation component is adjusted by the synchronous control and processing module to generate an optical path compensation that is equal to and opposite to the optical path deviation, so that the coherent gate coincides with the focal plane.

[0014] This specification provides one or more embodiments of a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement a full-field OCT imaging method as described above.

[0015] This specification provides one or more embodiments of a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the full-field OCT imaging method based on the system described above.

[0016] This disclosure provides a full-field OCT system, imaging method, device, and medium based on orthogonal dual liquid crystal phase compensation. Its advantages lie in the following: a broadband light source module provides broadband illumination light with low coherence length, which is then collimated to output parallel light, laying the foundation for high axial resolution imaging. This adapts to the imaging needs of weak signal samples such as biological tissues and ensures the stability of the signal source for subsequent interferometric imaging. The beam splitting module precisely splits the broadband illumination light into reference light and sample light according to a predetermined ratio using a non-polarized beam splitter, ensuring reasonable energy distribution between the two beams and providing a prerequisite for symmetrical interference between the reference arm and sample arm. It also adapts to the polarization characteristics of natural light, avoiding energy waste in the initial beam splitting stage. The reference arm module uses an orthogonal slow-axis configuration of a first liquid crystal phase modulation component and a first waveplate to selectively modulate the horizontal polarization component in the reference light. Combined with focusing by the first microscope objective and reflection by a fixed reference mirror, it achieves optical path adjustment without mechanical movement, avoiding traditional mechanical phase shifting. To address jitter and defocusing issues, the sample arm is used to achieve static optical path balance. The sample arm module and reference arm are symmetrically structured. The second liquid crystal phase modulation component and the second waveplate are orthogonally positioned on the slow axis to specifically modulate the vertical polarization component in the sample light. Through device parameters consistent with the reference arm and orthogonal polarization design, efficient utilization of fully polarized light is achieved, eliminating dispersion mismatch and ensuring the synchronous interference of the returning light from both arms. The detection module uses a tube lens to focus the interference signal, and the area array camera performs photoelectric conversion, efficiently capturing the interference image of the reference and sample light. This provides clear, high-contrast raw data for subsequent signal processing, ensuring imaging resolution and detection sensitivity. The control module precisely regulates the delay of the two liquid crystal phase modulation components through a differential driving strategy to achieve synchronous phase modulation. Simultaneously, it coordinates the control of the area array camera's acquisition timing, eliminating mechanical errors, improving system response speed and imaging stability, and ensuring synchronous movement of interference fringes and consistent imaging quality. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in one or more embodiments of this specification or in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of a full-field OCT system based on orthogonal dual liquid crystal phase compensation provided for one or more embodiments of this specification; Figure 2 A structural diagram of a full-field OCT system based on orthogonal dual liquid crystal phase compensation provided for one or more embodiments of this specification; Figure 3A schematic diagram of synchronous phase modulation under differential drive provided for one or more embodiments of this specification; Figure 4 A schematic flowchart illustrating a full-field OCT imaging method based on orthogonal dual liquid crystal phase compensation for one or more embodiments of this specification; Figure 5 This is a schematic diagram of the structure of a computer device provided for one or more embodiments of this specification. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions in one or more embodiments of this specification, the technical solutions in one or more embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this specification, and not all of the embodiments. Based on one or more embodiments of this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of this invention.

[0020] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0021] Device Examples According to embodiments of the present invention, a full-field OCT system based on orthogonal dual liquid crystal phase compensation is provided, such as... Figure 1 The diagram shown is a structural schematic of the full-field OCT system based on orthogonal dual-liquid crystal phase compensation provided in this embodiment. The full-field OCT system based on orthogonal dual-liquid crystal phase compensation according to this embodiment includes: The broadband light source module 11 is used to provide broadband illumination light with low coherence length. After being collimated by the collimating lens group, it outputs parallel light and can be an LED light source or a halogen lamp.

[0022] The beam splitter module 12 is a non-polarizing beam splitter placed in the light source optical path. It is used to split the broadband illumination light into reference light and sample light according to a predetermined ratio, which then enter the reference arm and sample arm respectively. The preset ratio can be 50:50.

[0023] The reference arm 13 is arranged in sequence along the direction of reference light propagation, including a first liquid crystal phase modulation component, a first waveplate, a first microscope objective, and a fixed reference mirror. The order of the first liquid crystal phase modulation component and the first waveplate can be interchanged. The slow axis direction of the first liquid crystal phase modulation component is a first direction, which is a horizontal direction (such as the horizontal direction X). The slow axis direction of the first waveplate is a second direction perpendicular to the first direction, which is a vertical direction (such as the vertical direction Y).

[0024] The sample arm 14 is sequentially configured with a second liquid crystal phase modulation component, a second waveplate, a second microscope objective, and the sample to be tested along the sample light propagation direction. The second liquid crystal phase modulation component has the same material properties and thickness as the first liquid crystal phase modulation component, and its slow axis direction is the second direction, orthogonal to the liquid crystal optical axis of the reference arm. The second waveplate has the same parameters as the first waveplate, and its slow axis direction is the first direction, orthogonal to the slow axis of the first waveplate of the reference arm. The first waveplate and the first liquid crystal phase modulation component are optically bonded together as a single unit, and / or the second waveplate and the second liquid crystal phase modulation component are optically bonded together as a single unit.

[0025] like Figure 2 The diagram shown is a structural diagram of the full-field OCT system based on orthogonal dual liquid crystal phase compensation provided in this embodiment.

[0026] The slow axis of the first waveplate is orthogonal to the slow axis of the first liquid crystal phase modulation assembly, and the slow axis of the second waveplate is orthogonal to the slow axis of the second liquid crystal phase modulation assembly. The reference arm liquid crystal modulation horizontal polarization component (E) x ), Sample arm liquid crystal modulation vertical polarization component (E y This allows both orthogonal polarization components in natural light to participate in effective phase modulation, avoiding light energy loss caused by the polarizer and improving light energy utilization and detection sensitivity.

[0027] Among them, the first and second microscope objectives are high numerical aperture (High NA) microscope objectives, and the first and second waveplates are both 0th order half-waveplates with a slow axis retardation of λ / 2, where λ is the center wavelength of the broadband illumination light. A waveplate is connected in series in the reference arm and the sample arm respectively. The waveplate is orthogonal to the optical axis of the liquid crystal. In the initial state, the retardation of the liquid crystal and the waveplate is λ / 2, which ensures that the total phase difference between the horizontally polarized light and the vertically polarized light in the two arms is 0, eliminating static dispersion mismatch, locking the zero optical path difference position, and maximizing the fringe contrast.

[0028] For horizontally polarized light ( E x The slow-axis phase delay of the first liquid crystal in the reference arm is: The fast-axis delay of the first waveplate is 0; the fast-axis delay of the second liquid crystal in the sample arm is 0, and the slow-axis delay of the second waveplate is 0. Thus, the horizontally polarized light in both arms ( E x The total phase difference is Δ = =0.

[0029] For vertically polarized light ( ): Experiencing the fast-axis delay 0 of the first liquid crystal and the slow-axis delay of the first waveplate in the reference arm. ; experiencing the slow axis of the second liquid crystal in the sample arm And the fast axis 0 of the second wave plate. Thus, the vertically polarized light of both arms ( The total phase difference is .

[0030] The detection module 15 includes a tube lens and an area array camera, which is a CMOS or CCD camera, used to receive the interference signal between the reflected light from the reference arm and the backscattered light from the sample arm and perform photoelectric conversion.

[0031] The control module 16 is electrically connected to the first liquid crystal phase modulation component, the second liquid crystal phase modulation component, and the detection module. It is used to apply differential driving voltages to the first and second liquid crystal phase modulation components and synchronously control the area array camera for acquisition. The first and second liquid crystal phase modulation components are nematic liquid crystal variable delay devices with an adjustable delay range of 0 to λ. The control module adjusts the delay change value within the range of -λ / 2 to λ / 2, making the optical path difference between the two arms adjustable between -λ and λ.

[0032] like Figure 3 The diagram shown illustrates synchronous phase modulation under differential drive provided in this embodiment. Specifically, a push-pull strategy is used to drive the first liquid crystal phase modulation component and the second liquid crystal phase modulation component. In the initial state, the phase delay generated by the first liquid crystal phase modulation component and the second liquid crystal phase modulation component is controlled to be equal to the slow axis delay of the first waveplate and the second waveplate. For example, the delay of the first liquid crystal is increased by δ. +δ), the second liquid crystal delay decreases by δ ( -δ), the average value of the first and second liquid crystals is the initial phase, which is the retardation of the first and second waveplates. initial phase =λ / 2, the adjustable range of the delay of the first and second liquid crystals is 0~λ, the maximum value of δ is λ / 2, and the minimum value of δ is... The final optical path difference (OPL) is adjustable between -λ and λ, and the optical path difference between the two polarization states is always equal. This ensures that the initial positions of the interference fringes of the horizontally polarized light and the vertically polarized light coincide and move synchronously during the scanning process, thus achieving blur-free, high-contrast imaging.

[0033] The system provided in this embodiment provides broadband illumination light with low coherence length through a broadband light source module, which is then collimated to output parallel light, laying the foundation for high axial resolution imaging. This adapts to the imaging needs of weak signal samples such as biological tissues and ensures the stability of the signal source for subsequent interferometric imaging. The beam splitting module precisely splits the broadband illumination light into reference light and sample light according to a predetermined ratio using a non-polarized beam splitter, ensuring reasonable energy distribution between the two beams. This provides a prerequisite for symmetrical interference between the reference arm and the sample arm, while also adapting to the polarization characteristics of natural light to avoid wasting light energy in the initial beam splitting stage. The reference arm module uses an orthogonal slow-axis configuration of a first liquid crystal phase modulation component and a first waveplate to specifically modulate the horizontal polarization component in the reference light. Combined with focusing by the first microscope objective and reflection by a fixed reference mirror, it achieves optical path adjustment without mechanical movement, avoiding the jitter and defocusing problems of traditional mechanical phase shifting. It also works with the sample arm to complete... Static optical path balance; the sample arm module has a symmetrical structure with the reference arm, and the second liquid crystal phase modulation component and the second waveplate are set at orthogonal slow axis to specifically modulate the vertical polarization component in the sample light. Through the same device parameters and orthogonal polarization design as the reference arm, the efficient utilization of fully polarized light is achieved, dispersion mismatch is eliminated, and the interference synchronization of the return light from the two arms is ensured; the detection module focuses the interference signal with the tube lens, and completes photoelectric conversion through the area array camera to efficiently capture the interference image of the reference light and the sample light, providing clear and high-contrast raw data for subsequent signal processing, ensuring imaging resolution and detection sensitivity; the control module precisely controls the delay of the two liquid crystal phase modulation components through a differential driving strategy to achieve synchronous phase modulation, and at the same time coordinately controls the acquisition timing of the area array camera to eliminate mechanical errors, improve system response speed and imaging stability, and ensure synchronous movement of interference fringes and consistency of imaging quality.

[0034] Method Implementation Examples According to embodiments of the present invention, a full-field OCT imaging method based on the above-described system is provided, such as... Figure 4 The diagram shown is a flowchart of the full-field OCT imaging method based on the above system provided in this embodiment. The full-field OCT imaging method based on the above system according to this embodiment includes the following steps: S410. At least one set of differential driving signals is applied to the first liquid crystal phase modulation component and the second liquid crystal phase modulation component through the control module, so that the initial phase delay of both is set to a preset value λ / 2, which is consistent with the slow axis delay of the first waveplate and the second waveplate, thereby achieving static optical path balance of the two arms.

[0035] The broadband illumination light emitted by the S420 broadband light source module is split into reference light and sample light by the beam splitter module, and then enters the reference arm module and the sample arm module respectively.

[0036] S430. The reference light, after being modulated by the first liquid crystal phase modulation component and compensated by the first waveplate, is irradiated by the first microscope objective and reflected back.

[0037] S440. After the sample light is modulated by the second liquid crystal phase modulation component to modulate the vertical polarization component and compensated by the second waveplate, it is irradiated onto the sample under test through the second microscope objective and backscattered back.

[0038] The S450 control module adopts a push-pull differential driving strategy to adjust the delay of the first liquid crystal phase modulation component and the second liquid crystal phase modulation component so that the delay of the two components changes in opposite directions, thereby realizing synchronous phase modulation of horizontally polarized light and vertically polarized light.

[0039] S460. The returned reference light and sample light are combined by the beam splitter module and focused onto the area array camera through the tube lens. The area array camera simultaneously acquires interference images.

[0040] S470: The control module processes the acquired interference image to obtain a high-resolution tomographic image of the sample under test.

[0041] It also includes the following steps: The delay of the first liquid crystal phase modulation component and the second liquid crystal phase modulation component is adjusted by the synchronous control and processing module so that the relative optical path difference between the horizontally polarized light and the vertically polarized light is λ / 2.

[0042] A DC background image is acquired by an area array camera after complementary interference fringes are canceled. The DC background image is then subtracted from the original interferogram in subsequent image processing to eliminate false noise.

[0043] It also includes the following steps: Based on the average refractive index and imaging depth of the sample, the optical path deviation between the focal plane and the coherent gate is calculated. The delay of the first liquid crystal phase modulation component and the second liquid crystal phase modulation component is adjusted by the synchronous control and processing module to generate optical path compensation that is equal to and opposite to the optical path deviation, so that the coherent gate coincides with the focal plane.

[0044] The method provided in this embodiment applies a differential driving signal through a control module to ensure that the initial phase delay of the two liquid crystal phase modulation components matches the slow axis delay of the corresponding waveplate, accurately achieving static optical path balance between the reference arm and the sample arm, eliminating initial dispersion mismatch, and laying a stable foundation for subsequent interferometric imaging. The broadband light source is rationally split into reference light and sample light by a beam splitter, ensuring that the energy distribution of the two beams matches the imaging requirements and guaranteeing the stability of the optical path transmission of each arm, providing qualified incident light for polarization modulation and interference. The reference light is specifically modulated for its horizontal polarization component by the first liquid crystal phase modulation component, and then focused and reflected after compensation by the first waveplate, achieving effective modulation and optical path calibration of the horizontally polarized light, avoiding modulation failure caused by polarization dependence. The sample light is specifically modulated for its horizontal polarization component by the second liquid crystal phase modulation component. The gate modulates the vertical polarization component, and after compensation with a second waveplate, it illuminates the sample and acquires backscattered light, making full use of the vertical polarization component in natural light to improve light energy utilization and simultaneously achieve optical path matching of the sample light. The control module adopts a push-pull differential drive, causing the retardation of the two liquid crystals to change in opposite directions, ensuring that the interference fringes of the horizontal and vertical polarized light move synchronously, eliminating dynamic phase deviation, and ensuring the consistency and stability of the interference signal. The combined interference light is focused by a tube lens onto an area array camera, simultaneously acquiring high-quality interference images, providing clear, high-contrast raw data for subsequent image processing, and ensuring imaging resolution. The control module processes the acquired interference images, accurately extracts sample structural information, and finally outputs high-resolution tomographic images, realizing non-invasive and clear imaging of samples such as biological tissues.

[0045] The following specific implementation case further illustrates this point: Example 1: Standard Phase Modulation Mode Based on a 0th Order Half-Wave Plate 1. Device selection: (1) Half-wave plate (HWP): Zero-order half-wave plates are selected for both the first wave plate of the reference arm and the second wave plate of the sample arm. Compared with multi-order wave plates, zero-order wave plates are not sensitive to changes in wavelength and temperature, which can ensure that the dispersion matching is in the best state under broadband light source. From the perspective of cost, polymer true zero-order half-wave plates are preferred.

[0046] First and second liquid crystal adjustable delay units: standard nematic liquid crystal variable delay units are selected, with a maximum phase modulation amount slightly greater than one full wavelength λ.

[0047] 2. Initial State Setting: When the system starts up, the controller applies an initial bias voltage to LC1 and LC2, so that the initial phase delay of both liquid crystal devices is precisely set to half the wavelength (λ / 2). In this state, combined with the effect of the 0th order half-wave plate, the static optical path introduced by the reference arm and the sample arm with respect to horizontally polarized light and vertically polarized light is symmetrical.

[0048] 3. Phase Modulation Process: Imaging is performed using a four-step phase-shifting method. The controller adjusts the driving voltages of LC1 and LC2, causing a slight change in their delay from their initial values. For example, to achieve a phase-shifting step size of π / 2, the delay of LC1 is increased by λ / 8, while the delay of LC2 is decreased by λ / 8 (differential driving). Since the liquid crystal changes its refractive index rather than its physical thickness, the imaging focal point remains absolutely stationary throughout the entire process.

[0049] Example 2: Large Range Adjustment Mode Based on Multi-Wave Liquid Crystal This embodiment is suitable for scenarios that require a wider range of optical path adjustment, such as when it is necessary to compensate for aberrations introduced by a thicker coverslip, or to perform a small-range axial depth scan (A-scan) without moving the reference mirror.

[0050] 1. Component Selection: Half-wave plate: Select a waveplate with a specific large delay, such as an advanced waveplate or quartz waveplate with a delay of 3 wavelengths (3λ). Liquid crystal retarder: Select a multi-wave variable retarder, which has a wide phase modulation range, such as an adjustable range of 0 to 6 wavelengths (0~6λ).

[0051] 2. Working Principle: Due to the significantly increased modulation range of liquid crystals, the system can not only perform minute phase modulation (for image reconstruction), but also introduce optical path differences of several micrometers or even tens of micrometers by drastically changing the driving voltage. This configuration allows the system to electronically control the movement of interference fringes (coherence gates) back and forth in the axial direction without moving any mechanical parts, thus achieving electronic depth tomography scanning.

[0052] Example 3: Compact structure with integrated bonding This embodiment focuses on improving the mechanical stability and optical transmittance of the system, and is suitable for portable FFOCT devices with strict requirements on size and environmental adaptability.

[0053] 1. Device Composition: A polymer true zero-order half-wave plate (HWP) is used. This wave plate is made of a birefringent polymer thin film with an extremely thin thickness (micrometer level). The liquid crystal cell adopts a liquid crystal cell structure based on a glass substrate.

[0054] 2. Manufacturing Process: The polymer true 0-order half-wave plate is directly bonded to the light-transmitting surface of the liquid crystal sheet using optical adhesive. During bonding, the slow axis of the wave plate is strictly aligned to be orthogonal to the slow axis of the liquid crystal sheet.

[0055] 3. Beneficial Effects: Elimination of Fresnel Reflection: The bonding process eliminates the air gap between the waveplate and the liquid crystal panel, reducing the number of reflective surfaces, significantly improving light energy utilization, and reducing stray light within the system. Enhanced Stability: The integrated structure permanently fixes the relative angle between the waveplate and the liquid crystal, preventing angle mismatch due to vibration or thermal expansion and contraction, greatly improving the long-term stability of the system. Compact Structure: The total thickness of this combined device is almost equal to the thickness of a single liquid crystal panel, significantly saving optical path space.

[0056] Example 4: A DC Background Acquisition Method Based on Complementary Interference This embodiment provides a method for acquiring a clean DC background using the unique optical architecture of this invention. In traditional FFOCT, acquiring the background typically requires physically blocking the reference arm, which is cumbersome.

[0057] 1. Principle Explanation: The total light intensity received by the detector in this system is the horizontal polarization interference component (I0). x ) and vertical polarization interference components (I y The incoherent superposition of I. x Located in the bright fringes (constructive interference) and I y When in dark fringes (destructive interference), if the sample is isotropic, the two sets of fringes coincide in spatial position but are opposite in brightness.

[0058] 2. Operating Procedures: The controller adjusts the voltage of the liquid crystal adjustable delay unit 1 and liquid crystal adjustable delay unit 2 so that both produce a delay of 5 / 8λ (or other specific value). At this point, the relative optical path difference between horizontally polarized light and vertically polarized light can be precisely half a wavelength (π) phase difference. For horizontal polarization, the optical path difference between the reference and sample is: +2*5 / 8λ (reference liquid crystal plate) - 2*1 / 2λ (sample 0th order half-wave plate) = 1 / 4λ. For vertical polarization, the optical path difference between the reference and sample is: 2*1 / 2λ (reference 0th order half-wave plate) - 2*5 / 8λ (sample liquid crystal plate) = -1 / 4λ. Thus, the optical path difference between horizontal and vertical polarization is exactly half a wavelength (1 / 2λ), corresponding to a phase of π. In this state, the interference fringes generated by the horizontal polarization component and the interference fringes generated by the vertical polarization component form a complementary black-and-white relationship. Since the camera pixels simultaneously receive these two polarization components within the integration time, the complementary fringes cancel each other out (average) on the detector target surface, making the interference fringes completely invisible in the image acquired by the camera. The image acquired at this time is a DC background image containing the sample reflected light and the reference reflected light.

[0059] 3. Signal Processing: The DC background image is stored. In subsequent phase-shifting imaging calculations, subtracting this DC background from each frame of the original interferogram can greatly eliminate false noise and improve image contrast.

[0060] Example 5: Dynamic Dispersion and Walk-off Compensation for Deep Imaging This embodiment is based on the hardware of Embodiment 2 and solves the problem of "focal plane walk-off" that occurs when high numerical aperture objectives are used to image deep tissues.

[0061] 1. Background: When an FFOCT system focuses deep within a sample, the refractive index of the biological sample (approximately 1.33-1.4) differs from that of air or the immersion liquid. As light propagates within the sample, the actual focusing position (focal plane) separates from the interference position (coherence gate) with equal optical path length. Typically, the focusing plane moves faster than the coherence gate, resulting in blurred images. Figure (a) shows the coherence plane and focal plane coinciding on the sample surface. Figure (b) shows the coherence plane and focal plane separating deep within the sample.

[0062] 2. Compensation steps: (1) Initial alignment: When imaging the sample surface, adjust the optical path difference of the reference sample so that the coherence gate coincides with the focal plane.

[0063] (2) Deep scanning: When the sample is focused to a depth z inside by moving the stage or objective lens, the theoretical optical path deviation Δ between the focal plane and the coherence gate is calculated based on the average refractive index of the sample. OPD .

[0064] (3) Dynamic compensation: Using the multi-wave liquid crystal variable delay device in Example 2, an additional bias voltage is applied to generate a voltage that is similar to Δ OPD Equivalent reverse optical path compensation. By adjusting this larger optical path difference, the coherence gate is "pulled back" to the focal plane position, compensating for the drift phenomenon.

[0065] 3. Effect: This method ensures that the interference signal is always the strongest and the resolution is the highest throughout the entire depth scanning range, effectively extending the imaging penetration depth of the FFOCT system.

[0066] The embodiments of the present invention are device embodiments corresponding to the above method embodiments. The specific operations of each module processing step can be understood with reference to the description of the method embodiments, and will not be repeated here.

[0067] like Figure 5 As shown, the present invention also provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, it implements the full-field OCT imaging method based on the system described in the above embodiments, or when the computer program is executed by a processor, it implements the full-field OCT imaging method based on the system described in the above embodiments.

[0068] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0069] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for apparatus or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The apparatus and system embodiments described above are merely illustrative. 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 modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and the contents not described in detail in the specification of the present invention are known to those skilled in the art.

Claims

1. A full-field OCT system based on orthogonal dual liquid crystal phase compensation, characterized in that, include: A broadband light source module is used to provide broadband illumination light with low coherence length, which is collimated by a collimating lens group and output as parallel light. The beam splitting module is a non-polarizing beam splitter used to split the broadband illumination light into reference light and sample light according to a predetermined ratio, which then enter the reference arm and sample arm respectively. The reference arm is arranged in sequence along the direction of reference light propagation, including a first liquid crystal phase modulation component, a first waveplate, a first microscope objective, and a fixed reference mirror. The slow axis direction of the first liquid crystal phase modulation component is a first direction, and the slow axis direction of the first waveplate is a second direction perpendicular to the first direction. The sample arm is arranged sequentially along the sample light propagation direction, including a second liquid crystal phase modulation component, a second waveplate, a second microscope objective, and the sample to be tested. The second liquid crystal phase modulation component has the same material properties and thickness as the first liquid crystal phase modulation component, and the slow axis direction is the second direction. The second waveplate has the same parameters as the first waveplate, and the slow axis direction is the first direction. The detection module, including a tube lens and an area array camera, is used to receive the interference signal between the reflected light from the reference arm and the backscattered light from the sample arm and perform photoelectric conversion. The control module is electrically connected to the first liquid crystal phase modulation component, the second liquid crystal phase modulation component, and the detection module, and is used to apply differential driving voltage to the first liquid crystal phase modulation component and the second liquid crystal phase modulation component and synchronously control the area array camera to acquire data.

2. The full-field OCT system based on orthogonal dual liquid crystal phase compensation as described in claim 1, characterized in that, The first direction is horizontal, and the second direction is vertical; Both the first and second waveplates are 0th-order half-waveplates with a slow axis delay of λ / 2, where λ is the center wavelength of the broadband illumination light.

3. The full-field OCT system based on orthogonal dual liquid crystal phase compensation as described in claim 1 or 2, characterized in that, The first liquid crystal phase modulation component and the second liquid crystal phase modulation component are nematic liquid crystal variable delay devices, and the delay adjustment range is 0~λ; The control module adjusts the delay value within the range of -λ / 2 to λ / 2, making the optical path difference between the two arms adjustable between -λ and λ.

4. The full-field OCT system based on orthogonal dual liquid crystal phase compensation as described in claim 1, characterized in that, The control module is also configured to: A push-pull strategy is used to drive the first liquid crystal phase modulation component and the second liquid crystal phase modulation component; In the initial state, the phase delay generated by the first liquid crystal phase modulation component and the second liquid crystal phase modulation component is equal to the slow axis delay of the first waveplate and the second waveplate.

5. The full-field OCT system based on orthogonal dual liquid crystal phase compensation as described in claim 1, characterized in that, The first waveplate and the first liquid crystal phase modulation component are optically bonded together as an integral structure, and / or the second waveplate and the second liquid crystal phase modulation component are optically bonded together as an integral structure; The slow axis of the first waveplate is orthogonal to the slow axis of the first liquid crystal phase modulation component, and the slow axis of the second waveplate is orthogonal to the slow axis of the second liquid crystal phase modulation component.

6. A full-field OCT imaging method based on the system described in any one of claims 1-5, characterized in that, Includes the following steps: The control module applies at least one set of differential driving signals to the first liquid crystal phase modulation component and the second liquid crystal phase modulation component, so that the initial phase delay of both is set to a preset value and is consistent with the slow axis delay of the first waveplate and the second waveplate, thereby achieving static optical path balance of the two arms. The broadband illumination light emitted by the broadband light source module is split into reference light and sample light by the beam splitting module, and then enters the reference arm module and the sample arm module respectively. The reference light is modulated by the first liquid crystal phase modulation component to modulate the horizontal polarization component and compensated by the first waveplate. It then shines on the reference mirror through the first microscope objective and is reflected back. The sample light is modulated by the vertical polarization component of the second liquid crystal phase modulation component and compensated by the second waveplate. Then, it is irradiated onto the sample under test through the second microscope objective and backscattered back. The control module adopts a push-pull differential driving strategy to adjust the delay of the first liquid crystal phase modulation component and the second liquid crystal phase modulation component so that the delay of the two components changes in opposite directions, thereby realizing synchronous phase modulation of horizontally polarized light and vertically polarized light. The returned reference light and sample light are combined by the beam splitting module and focused onto the area array camera through the tube lens. The area array camera simultaneously acquires interference images. The control module processes the acquired interference images to obtain high-resolution tomographic images of the sample under test.

7. The full-field OCT imaging method as described in claim 6, characterized in that, It also includes the following steps: The delay of the first liquid crystal phase modulation component and the second liquid crystal phase modulation component is adjusted by the synchronous control and processing module so that the relative optical path difference between the horizontally polarized light and the vertically polarized light is λ / 2. A DC background image is acquired by an area array camera after complementary interference fringes are canceled. The DC background image is then subtracted from the original interferogram in subsequent image processing to eliminate false noise.

8. The full-field OCT imaging method as described in claim 6, characterized in that, It also includes the following steps: Based on the average refractive index and imaging depth of the sample, the optical path deviation between the focal plane and the coherent gate is calculated. The delay of the first liquid crystal phase modulation component and the second liquid crystal phase modulation component is adjusted by the synchronous control and processing module to generate an optical path compensation that is equal to and opposite to the optical path deviation, so that the coherent gate coincides with the focal plane.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the full-field OCT imaging method based on the system described in any one of claims 6 to 8.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the full-field OCT imaging method based on the system described in any one of claims 6 to 8.

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