A wide-band sagnac snapshot full-polarization imaging system and endoscope

Abstract

The application belongs to the technical field of polarization imaging, and relates to a wide-band Sagnac snapshot full-polarization imaging system and an endoscope. The system comprises a first non-polarized light beam splitter and a second MDCPSI system arranged at intervals on a first optical axis, a first MDCPSI system and a first non-polarized light beam splitter arranged at intervals on a second optical axis perpendicular to the first optical axis, a first plane mirror and a second MDCPSI system arranged at intervals on a third optical axis, a first plane mirror, a second non-polarized light beam splitter, a polarimeter and a detector arranged at intervals on a fourth optical axis parallel to the second optical axis in sequence, the detector and a processor are electrically connected, a second plane mirror and a first MDCPSI system arranged at intervals on a fifth optical axis parallel to the first optical axis in sequence, and a second plane mirror and a second non-polarized light beam splitter arranged at intervals on a sixth optical axis parallel to the third optical axis. The application can provide a high-resolution, low-noise full-polarization image, and provides a new scheme for real-time polarization imaging in surgical operations.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polarization imaging, and particularly relates to a wide-band Sagnac snapshot full-polarization imaging system and an endoscope. BACKGROUND

[0002] In surgical operations, real-time high-precision imaging technology is crucial for doctors to perform delicate operations. Traditional microscopic imaging methods, such as optical transmission imaging, fluorescence imaging, and confocal microscope imaging, have been widely used in surgical operations. However, these technologies still have some significant shortcomings. During the operation, reflection and glare phenomena often affect the visual experience of doctors, especially in high-brightness areas. Reflection interference often makes doctors unable to clearly observe the details of the tissue structure, which not only affects the doctor's judgment of the lesion but also may increase the risk of surgery. Another common problem is edge blur and low contrast. Traditional imaging methods often have difficulty distinguishing details when dealing with complex tissue structures, especially in soft tissue, small lesions, or microvascular areas. The contrast in the image is low, and the differences between tissues cannot be accurately reflected. In addition, the influence of blood flow is also a major challenge in surgical microscope imaging. Blood flow often leads to a decrease in imaging quality, especially in the area around blood vessels. Traditional optical imaging methods cannot effectively distinguish blood from surrounding tissues, making it difficult for doctors to clearly observe the blood flow area and its relative relationship with the surrounding tissues.

[0003] To solve the above problems, polarization imaging technology, as an advanced imaging means, is introduced into clinical application to provide more image information in areas where traditional imaging technology cannot clearly display. Especially in improving image contrast, reducing reflection interference, and distinguishing tissue structure, traditional MDCPSI systems and other polarization imaging technologies can effectively eliminate the influence of reflection, enhance edge resolution, and have higher accuracy in observing dynamic tissues or blood flow areas. In polarization imaging technology, channel modulation type polarization imaging technology has become a research hotspot in recent years due to its high spatial resolution, no need for moving parts, compact structure, and other advantages. This technology can simultaneously acquire full Stokes parameters and is suitable for imaging dynamic targets.

[0004] However, the introduction of wide-band light imaging brings new challenges to channel modulation type polarization imaging technology. In wide-band imaging, the interference effect of light can cause serious interference fringe aliasing phenomenon, making it impossible to correctly restore polarization information and affecting the accuracy of imaging. Due to this effect, traditional polarization imaging technology can only use quasi-monochromatic light for imaging, thereby limiting its application in wide-band conditions. In addition, in a weak light environment, due to insufficient light energy and low signal-to-noise ratio, the application of channel modulation type polarization imaging systems is significantly limited, affecting their clinical applicability in surgical operations. SUMMARY

[0005] Therefore, the application provides a wide-band Sagnac snapshot full-polarization imaging system and an endoscope to solve the above technical problems.

[0006] The technical scheme of the application is as follows:

[0007] A wide-band Sagnac snapshot full-polarization imaging system comprises a first non-polarized light beam splitter, a first MDCPSI system, a second MDCPSI system, a first plane mirror, a second plane mirror, a second non-polarized light beam splitter, a polarimeter, a detector, and a processor, wherein the detector and the processor are electrically connected, the first non-polarized light beam splitter and the second MDCPSI system are arranged at intervals on a first optical axis, the first MDCPSI system and the first non-polarized light beam splitter are arranged at intervals on a second optical axis perpendicular to the first optical axis, the first plane mirror and the second MDCPSI system are arranged at intervals on a third optical axis, the third optical axis is perpendicular to the second optical axis and the first optical axis, the first plane mirror, the second non-polarized light beam splitter, the polarimeter, and the detector are arranged at intervals in sequence on a fourth optical axis, the fourth optical axis is parallel to the second optical axis, the second plane mirror and the first MDCPSI system are arranged at intervals on a fifth optical axis parallel to the first optical axis, and the second plane mirror and the second non-polarized light beam splitter are arranged at intervals on a sixth optical axis parallel to the third optical axis.

[0008] The incident light is divided into two beams of identical light waves after passing through the first non-polarized light beam splitter and The light waves and are respectively split by the first MDCPSI system and the second MDCPSI system, and then are respectively adjusted by the first plane mirror and the second plane mirror to change the propagation direction, and are respectively transmitted and reflected by the second non-polarized light beam splitter, and finally reach the detector to form an image after passing through the polarimeter, and the processor extracts the polarization interference information.

[0009] Further, the first plane mirror is arranged at an angle of 45° between the third optical axis and the fourth optical axis, and the second plane mirror 5 is arranged at an angle of 90° between the first plane mirror 4.

[0010] Further, the first MDCPSI system and the second MDCPSI system have the same structure.

[0011] Further, the first MDCPSI system comprises a third plane mirror and a polarization beam splitter arranged in sequence and spaced apart on a seventh optical axis, the polarization beam splitter is provided with a compensating plate, the compensating plate is arranged close to the third plane mirror, a fourth plane mirror and the polarization beam splitter are arranged spaced apart on an eighth optical axis perpendicular to the seventh optical axis, and the fourth plane mirror is located on a side away from the compensating plate, the first blazed grating and the second blazed grating are arranged reversely and spaced apart and located on an optical path between the fourth plane mirror and the third plane mirror, the first blazed grating is close to the fourth plane mirror, and the seventh optical axis is coaxially arranged with the fifth optical axis, and the eighth optical axis is coaxially arranged with the second optical axis.

[0012] Further, the polarization beam splitter comprises a flat plate beam splitter and a narrow-band beam splitter film arranged in sequence, the compensating plate is arranged close to the narrow-band beam splitter film, and the material and thickness of the compensating plate are the same as those of the flat plate beam splitter.

[0013] Further, the distance from the polarization beam splitter to the fourth plane mirror and the third plane mirror is the same.

[0014] Further, the geometric centers of the first non-polarized light beam splitter, the second non-polarized light beam splitter, the polarization beam splitter in the first MDCPSI system, the polarization beam splitter in the second MDCPSI system, the first plane mirror and the second plane mirror are located at the vertices of the same cube.

[0015] Further, the polarization beam splitter, the fourth plane mirror and the third plane mirror are arranged obliquely and meet the following relationships with the seventh optical axis and the eighth optical axis respectively:

[0016] ,

[0017] ,

[0018] Wherein, ɑ is the included angle between the polarization beam splitter and the seventh optical axis, the unit is °, β is the included angle between the polarization beam splitter and the eighth optical axis, the unit is °, γ is the included angle between the fourth plane mirror and the eighth optical axis, the unit is °, φ is the included angle between the third plane mirror and the seventh optical axis, the unit is °, and δ is the grating blaze angle of the first blazed grating 24 and the second blazed grating, the unit is °.

[0019] Further, the δ is 20°-25°.

[0020] An endoscope comprising a wide-band Sagnac snapshot full-polarization imaging system as described above.

[0021] Compared with the prior art, the wide-band Sagnac snapshot full-polarization imaging system and endoscope provided by the application can realize wide-band full-polarization detection by combining two MDCPSI structures to divide incident light into four different position shearing beams, and finally converging on a focal plane array to form interference fringes about full Stokes parameters, the whole system combines the advantages of Sagnac interferometer and grating structure, can realize real-time acquisition of complete two-dimensional Stokes parameters in a wide frequency band, effectively compensates the interference effect caused by wide-band imaging, improves the imaging quality, and meets the demand of real-time and accurate observation in surgical operation. Unlike traditional polarization imaging technology, the system can efficiently and real-timely acquire full-polarization information without any moving electric control components or microarray elements. The Sagnac structure in parallel form is adopted in the structural design, which not only overcomes the problem of small light throughput, but also improves the imaging quality, so that it can provide high-resolution and low-noise images, thereby effectively supporting the observation and analysis of dynamic targets in surgical operation, not only promoting the application range of polarization imaging technology, but also providing a new solution for the imaging technology of surgical microscopes, which can real-timely and non-destructively acquire complete polarization information in surgical operation, provide more accurate image reference for doctors, improve the operation precision and safety, has strong practicability, and is worth promoting. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a whole structure diagram of the application.

[0023] Figure 2 It is a local structure diagram in the application.

[0024] Figure 3 It is a polarization state of incident light.

[0025] Figure 4 It is an interference pattern on the BSCPSI focal plane array.

[0026] Figure 5 It is a spectrum diagram after Fourier transform of the interference pattern.

[0027] Figure 6 It is a three-dimensional perspective after Fourier transform of the interference pattern.

[0028] Figure 7 It is an image of the target , , and reconstructed. DETAILED DESCRIPTION

[0029] In surgical operations, real-time high-precision imaging technology is crucial for doctors to perform delicate operations. Traditional microscopic imaging methods, such as optical transmission imaging, fluorescence imaging, and confocal microscope imaging, have been widely used in surgical operations, but these technologies still have some significant shortcomings. During the operation, reflection and glare phenomena often affect the visual experience of doctors, especially in high-brightness areas, where reflected light interference often makes doctors unable to clearly observe the details of tissue structures, which not only affects doctors' judgment of lesions but also may increase the risk of surgery. Another common problem is edge blurring and low contrast, traditional imaging methods often have difficulty distinguishing details when dealing with complex tissue structures, especially in soft tissue, small lesions, or microvascular areas, where the contrast in the image is low and cannot accurately reflect the differences between tissues. In addition, the influence of blood flow is also a major challenge in surgical microscope imaging, blood flow often leads to a decrease in imaging quality, especially in the area around blood vessels, traditional optical imaging methods cannot effectively distinguish blood from surrounding tissues, making it difficult for doctors to clearly observe the blood flow area and its relative relationship with the surrounding tissues.

[0030] To solve these problems, there is an urgent need for a new imaging technology that can reduce the interference of reflection and glare, improve image contrast, clearly display details, and adapt to the dynamic target imaging needs in surgical operations. Polarization imaging technology, as an advanced imaging method, can provide more image information in areas where traditional imaging technology cannot clearly display, especially in improving image contrast, reducing reflected light interference, and distinguishing tissue structures. Polarization imaging technology can effectively eliminate the effects of reflection, while enhancing edge resolution, and has higher accuracy for observing dynamic tissues or blood flow areas.

[0031] Polarization imaging technology can be roughly divided into two categories: time-series polarization imaging technology and snapshot polarization imaging technology. Time-series polarization imaging technology includes rotating polarizer type and liquid crystal electric control type technology, which has simple principles, high detection precision, and can provide accurate image data. However, these technologies need to rely on the movement of electrically controlled or mechanical components to achieve polarization analysis, which makes them unable to perform real-time imaging on dynamic targets. In surgical operations, doctors often need to quickly and real-time obtain images, and traditional time-series polarization imaging technology cannot meet this demand due to the electrically controlled components or mechanical components within the system. Therefore, time-series polarization imaging is limited in surgical operations.

[0032] Compared with the time sequence type technology, the snapshot type polarization imaging technology has a more compact structure, can capture the polarization information of the target in real time, and is suitable for dynamic target imaging. The snapshot type polarization imaging technology includes a split-amplitude type, a split-aperture type, a split-focal plane type and a channel modulation type and the like. Although the split-amplitude type technology can provide higher polarization information accuracy, it has a large structure, needs multiple detectors, and has a high cost, is suitable for a large-aperture device, and is not suitable for a portable surgical microscope; the split-aperture type technology needs to be assembled with a large target surface detector, can provide a larger detection area, but has a relatively complex structure, a large device, and is difficult to install and debug, and is not suitable for surgical equipment with strict requirements on volume and weight.

[0033] Although the split-focal plane type technology can realize full focal plane imaging, the current commercial chip can only detect linear polarization information, and has not yet been able to effectively obtain complete full polarization information, which is still a major challenge faced by the technology. Despite this, in recent years, the channel modulation type polarization imaging technology has become a research hotspot due to its high spatial resolution, no need for moving parts, compact structure and the like. The technology can simultaneously obtain full Stokes parameters, and is suitable for imaging dynamic targets. However, when wide-band light imaging is used, the channel modulation type polarization imaging technology is easily affected by the serious interference fringe aliasing phenomenon, leading to incorrect recovery of the polarization information, which makes the technology only be able to use quasi-monochromatic light for imaging, and cannot process the interference effect caused by wide-band imaging. In a weak light environment, due to insufficient light energy and low signal-to-noise ratio, the application of the channel modulation type polarization imaging system is significantly limited.

[0034] The present application provides a wide-band Sagnac snapshot type full polarization imaging system and an endoscope, which attempts to combine the diffraction module with the channel modulation type polarization imaging system in the interference + diffraction compensation idea, so as to effectively compensate the interference effect caused by wide-band imaging, so as to solve the technical problems in the wide-band imaging described above. In order for those skilled in the art to better understand the technical solutions of the present application and to implement them, the technical solutions in the present application will be described clearly and thoroughly below in conjunction with the drawings.

[0035] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0036] In addition, it needs to be further pointed out that in the description of the embodiments of the application, unless otherwise specified, " / " means or, for example, A / B can mean A or B: "and / or" in the text is only a description of the relationship between the associated objects, which means that there can be three relationships, for example, A and / or B, which can mean: A exists alone, A and B exist together, and B exists alone, and in addition, in the description of the embodiments of the application, "multiple" means two or more than two.

[0037] The terms "first", "second", "third", "fourth" are only for descriptive purposes and cannot be understood as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second", "third", "fourth" can explicitly or implicitly include one or more of the features, and in the description of the application, unless otherwise specified, "multiple" means at least two, for example, two, three, etc., unless otherwise explicitly specified.

[0038] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0039] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through an intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0040] It should be noted that when an element is referred to as "fixed to" or "provided to" another element, it can be directly on another element or there can be a middle element. When an element is considered to be "connected" to another element, it can be directly connected to another element or there can be a middle element. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used in the present application are only for illustrative purposes and do not represent the only implementation.

[0041] Example 1

[0042] The application provides a broadband snapshot complete polarized Sagnac interferometer (BSCPSI), which combines two MDCPSI structures to divide incident light into four different position shearing beams, and finally converges on a focal plane array to form interference fringes about full Stokes parameters, realizes broadband full polarization detection, and combines the advantages of a Sagnac interferometer and a grating structure, can realize real-time acquisition of complete two-dimensional Stokes parameters in a wide frequency band, effectively compensates the interference effect caused by broadband imaging, improves imaging quality, and meets the demand for real-time and accurate observation in surgery.

[0043] The structural diagram of the BSCPSI system is shown in Figure 1 The BSCPSI system comprises a first non-polarized light beam splitter 1, a second non-polarized light beam splitter 6, a first MDCPSI system 2, a second MDCPSI system 3, a first plane mirror 4, a second plane mirror 5, a polarimeter 7, a detector 8 and a processor 9.

[0044] The detector 8 comprises a lens and a focal plane array (FPA), the lens is arranged close to the polarimeter 7, and the detector 8 and the processor 9 are electrically connected.

[0045] The first non-polarized light beam splitter 1 and the second MDCPSI system 3 are arranged on a first optical axis at intervals, the first MDCPSI system 2 and the first non-polarized light beam splitter 1 are arranged on a second optical axis at intervals, the second optical axis is perpendicular to the first optical axis, the first plane mirror 4 and the second MDCPSI system 3 are arranged on a third optical axis at intervals, the third optical axis is perpendicular to the second optical axis and the first optical axis, the first plane mirror 4, the second non-polarized light beam splitter 6, the polarimeter 7 and the detector 8 are arranged on a fourth optical axis at intervals, the fourth optical axis is parallel to the second optical axis and perpendicular to the second optical axis and the third optical axis, the second plane mirror 5 and the first MDCPSI system 2 are arranged on a fifth optical axis at intervals, the fifth optical axis is parallel to the first optical axis, the second plane mirror 5 and the second non-polarized light beam splitter 6 are arranged on a sixth optical axis at intervals, the sixth optical axis is parallel to the third optical axis, the first plane mirror 4 and the second plane mirror 5 are arranged at an angle, the angle between the first plane mirror 4 and the third optical axis and the fourth optical axis is 45°, and the angle between the second plane mirror 5 and the first plane mirror 4 is 90°.

[0046] Specifically, as shown in Figure 2As shown, the MDCPSI system, i.e., a modified dispersion compensation sagnac interferometer (MDCPSI), the first MDCPSI system 2 and the second MDCPSI system 3 used in the present application have the same structure, and the structure and working principle of the first MDCPSI system 2 are described as an example.

[0047] The structure of the first MDCPSI system 2 includes the third plane mirror 26 and the polarization beam splitter 22 arranged at intervals on the seventh optical axis, the polarization beam splitter 22 is provided with a compensation plate 21, and the compensation plate 21 is arranged close to the third plane mirror 26. The fourth plane mirror 23 and the polarization beam splitter 22 are arranged at intervals on the eighth optical axis perpendicular to the seventh optical axis, and the fourth plane mirror 23 is located on the side away from the compensation plate 21. The first blazed grating 24 and the second blazed grating 25 are reversely arranged and located on the optical path between the fourth plane mirror 23 and the third plane mirror 26, and the first blazed grating 24 is close to the fourth plane mirror 23. The seventh optical axis is coaxially arranged with the fifth optical axis, and the eighth optical axis is coaxially arranged with the second optical axis.

[0048] Specifically, the first blazed grating 24 and the second blazed grating 25 are reversely arranged, that is, the groove directions of the first blazed grating 24 and the second blazed grating 25 are opposite, that is, the blazed directions are opposite.

[0049] Specifically, the first blazed grating 24 and the second blazed grating 25 are reversely arranged, that is, the groove directions of the first blazed grating 24 and the second blazed grating 25 are opposite, that is, the blazed directions are opposite.

[0050] Specifically, in actual work, after the light is incident on the polarization beam splitter 22, it is divided into two beams of light orthogonal to each other in the vibration direction: the transmitted p-polarized light and the reflected s-polarized light. Among them, the p-polarized light is reflected by the fourth plane mirror 23 and then diffracted to the first order by the first blazed grating 24, and then the diffraction angle is eliminated after passing through the reversely and parallelly arranged second blazed grating 25, at this time the light is parallel to the transmission direction before being incident on the first blazed grating 24, and then it is reflected by the third plane mirror 26 and then transmitted through the polarization beam splitter 22 to exit, and the exit point has a certain deviation from the center, and the deviation size is , wherein is a constant related to the system structure parameters. Similarly, the s-polarized light passes through the third plane mirror 26, the second blazed grating 25, the first blazed grating 24 and the fourth plane mirror 23 in turn, and is finally reflected by the polarization beam splitter 22, and the distance of the exit light from the center is , and the distance between the two beams of exit light is the shear amount, which is proportional to the wavelength.

[0051] The present application makes the offset and shear of the two polarized lights proportional to the wavelength by precise diffraction control and optical path difference compensation, and compensates the optical path difference caused by the difference in film thickness by the compensation plate, thereby ensuring the accuracy of the system in high-precision optical measurement.

[0052] It should be noted that the p-polarized light transmitted by the polarization beam splitter 22 and the s-polarized light reflected by the polarization beam splitter 22 need to have the same optical path difference, that is, the distance between the polarization beam splitter 22 and the fourth plane mirror 23 and the third plane mirror 26 is equal. The polarization beam splitter 22 comprises a flat beam splitter and a narrow-band beam splitter film arranged in sequence, but since the manufacturing process of the polarization beam splitter 22 is to coat the narrow-band beam splitter film on one side of the flat beam splitter, the transmitted light will travel a distance more than the reflected light, and this distance is a nonlinear relationship with the wavelength, which cannot be adjusted by adjusting the length of the two arms to compensate. In the design of the device, we can place a compensation plate 21 with the same material and thickness as the flat beam splitter on the other side of the polarization beam splitter 22 to compensate, forming a laminated structure of the flat beam splitter, the narrow-band beam splitter film and the compensation plate 21, so that the optical path difference of the two beams after beam splitting remains the same. Specifically, the compensation plate 21 is a glass substrate.

[0053] The polarization beam splitter 22, the fourth plane mirror 23 and the third plane mirror 26 are all inclinedly arranged, and they respectively meet the following relationships with the seventh optical axis and the eighth optical axis:

[0054] (1)

[0055] (2)

[0056] Wherein, ɑ is the included angle between the polarization beam splitter 22 and the seventh optical axis, with the unit of °, β is the included angle between the polarization beam splitter 22 and the eighth optical axis, with the unit of °, γ is the included angle between the fourth plane mirror 23 and the eighth optical axis, with the unit of °, φ is the included angle between the third plane mirror 26 and the seventh optical axis, with the unit of °, and δ is the grating blaze angle of the first and second blazed gratings 24 and 25, with the unit of °.

[0057] Further specifically, δ is 20°-25°, and preferably δ is 22.5°, to ensure that the light is perpendicular to the first and second blazed gratings 24 and 25.

[0058] Specifically, in order to ensure the optical path difference of the BSCPSI system on the focal plane array, the geometric centers of the first non-polarized light beam splitter 1, the second non-polarized light beam splitter 6, the polarization beam splitter 22 in the first MDCPSI system 2, the polarization beam splitter 22 in the second MDCPSI system 3, the first plane mirror 4 and the second plane mirror 5 are located at the vertices of the same cube.

[0059] The MDCPSI system can only realize linear polarization imaging, the circular polarization information of the artificial target is relatively strong, the full polarization information has a longer transmission distance, and the application range of full polarization imaging is wider in the process of target detection and identification. Two beams of light can at most modulate three Stokes vectors, and more beams of light are needed to participate in interference to modulate all Stokes vectors. Therefore, the BSCPSI system provided in the application combines two MDCPSI structures, divides the incident light into four different position shearing beams, converges on the focal plane array after the polarizer 7 and the lens, forms interference fringes about full Stokes parameters, and realizes wide-band full polarization detection.

[0060] The specific working principle of the BSCPSI system is as follows:

[0061] The incident light of the target is divided into two beams of identical light waves after the first non-polarized light beam splitter 1 and The light waves and are respectively transmitted and reflected by the second non-polarized light beam splitter 6 after being divided and propagated by the first MDCPSI system 2 and the second MDCPSI system 3, and are finally transmitted by the polarizer 7 and reach the detector 8, and are focused on the focal plane array by the lens of the detector 8.

[0062] In order to ensure accurate focusing and uniform distribution of light, a front-mounted telescope system 10 is arranged on the incident light side of the first non-polarized light beam splitter 1, the front-mounted telescope system 10 includes an objective lens, a field stop and a collimating lens arranged in sequence and located on the same optical axis, and the light beams from the auxiliary mirror are collected, the field is limited and collimated through the objective lens, the field stop and the collimating lens, so that the light rays enter the main optical system in a uniform and aberration-free state, and the front-mounted telescope system 10 needs to be closely attached to the front end of the microscope and installed coaxially with the optical axis to ensure clear and stable imaging. Specifically, the objective lens is used to ensure that the image obtained from the surgical area maintains high resolution and low distortion, accurately captures the details of the tissue, the field stop is used to control the size of the field of view and adjust the amount of light entering the front-mounted telescope system 10, which avoids the influence of too bright or too dark light on image quality, and the collimating lens is used to arrange the light rays into parallel light beams, so that the subsequent optical elements can accurately receive the light from the surgical area, and the divergence of the light is avoided, thereby ensuring the clarity of the image.

[0063] In use, the light is focused by the objective lens and enters the front telescope system 10, and then the field diaphragm controls the field size and adjusts the amount of light entering the front telescope system 10. Finally, the light is collimated by the collimating lens and then enters the first non-polarized light beam splitter 1, and is divided into two beams of identical light waves I A With I B . Wherein, I A The light beams enter the main body structure of the second MDCPSI system 3 and are separated into two beams in the x direction; I B The light beams enter the main body structure of the first MDCPSI system 2 and are also separated into two beams in the y direction. Subsequently, the two beams of light from the second MDCPSI system 3 are adjusted by the first plane mirror 4, and the two beams of light from the first MDCPSI system 2 are adjusted by the second plane mirror 5. The four beams of light obtained through the above separation and adjustment are recombined at the second non-polarized light beam splitter 6. The recombined light beams are then polarized modulated by the polarizer 7 at an angle of 45° with respect to the -y axis, and are focused by the lens to the focal plane array FPA to form an image, thereby realizing the simultaneous acquisition of multi-channel polarization interference information. Finally, the processor 9 completes the extraction and analysis of the multi-channel polarization interference information.

[0064] The shear amount generated by the Sagnac wide-band linear polarization imaging structure is:

[0065] (3)

[0066] Wherein, is the shear amount generated by the Sagnac wide-band linear polarization imaging structure, is the wavelength of the incident light, is a constant, The value of is related to the parameters of the designed Sagnac wide-band linear polarization imaging structure.

[0067] By introducing the first blazed grating 24 and the second blazed grating 25, the dispersion of the carrier frequency in the PSI structure can be compensated, and Figure 2 As shown in the expanded MDCPSI, the p-polarized light propagates from left to right, and the s-polarized light propagates from right to left. After the light passes through the first blazed grating 24, it is diffracted to the first order, and then passes through the second blazed grating 25 with the same structure to eliminate the diffraction angle. At this time, the light is parallel to the original transmission direction.

[0068] After the above BSCPSI system processing, the incident light is divided into four modulated coherent light beams by the system. The four coherent light beams emitted by the BSCPSI system are distributed in a cross shape on the xoy plane, which is the same as the distribution of the shear beams generated by the Savart plate polarization interference imaging system. The BSCPSI system is in the x axis and yThe shear amounts in the axial direction are:

[0069] (4)

[0070] where, and are the shear amounts in the axial direction and x axial direction of the BSCPSI system, y is the lateral shear amount of the MDCPSI subsystem, is the diffraction order, m is the wavelength of the incident light, is the grating period, and L is the distance between the first blazed grating 24 and the second blazed grating 25 in each MDCPSI subsystem. d

[0071] The interference light intensity on the focal plane array can be expressed as:

[0072] (5)

[0073] where, is the interference light intensity on the focal plane array of the BSCPSI system, is the electric field vector in the x direction, is the electric field vector in the y direction, , , and are the cumulative phases of the four beams of light reaching the focal plane array.

[0074] The optical path lengths of the four beams of outgoing light before reaching the lens are the same, so the cumulative phase can be expressed as:

[0075] (6)

[0076] where, , , and are the cumulative phases of the four beams of light reaching the focal plane array, denotes the imaging focal length, m is the diffraction order, d is the grating period, and L is the distance between the first blazed grating 24 and the second blazed grating 25 in each MDCPSI subsystem, x i , y i are the image plane coordinates, respectively.

[0077] Only considering the diffraction of the blazed grating to the first order, let m = 1, according to the phase factor, the light intensity formula on the focal plane array is calculated as:​

[0078] (7)

[0079] where, is the intensity of the interference light on the focal plane array at x i ，y i the intensity of the interference light at , , , is the Stokes vector, x i and y i is the spatial position of the image coordinate point, denotes the carrier frequency of the interference fringes:

[0080] (8)

[0081] Using we obtain

[0082] (9)

[0083] where, is the intensity of the interference light on the focal plane array at x i ，y i the intensity of the interference light at , , , is the Stokes vector, x i and y i is the spatial position of the image coordinate point, denotes the carrier frequency of the interference fringes, denotes the argument (phase angle) of the complex .

[0084] The focal plane array intensity formula of the MDCPSI can be expressed as: (10)

[0085] where, is the MDCPSI intensity on the focal plane array, , and is the Stokes parameter, denotes the imaging focal length, d is the grating period, denotes the distance between the two blazed gratings, The coordinates of the image plane are given. The carrier frequency is independent of the wavelength, which indicates that the BSCPSI is a dispersion-free system like the MDCPSI, and can realize wide-band imaging.

[0086] From the comparison of equations (10) and (7), it can be seen that the MDCPSI system can only modulate three Stokes parameters, while the BSCPSI system can modulate all four Stokes parameters with different carrier frequencies, thereby realizing full-polarization information detection.

[0087] The Fourier transform of equation (9) can be obtained as: (11)

[0088] wherein, is the Fourier transform form of the interference light intensity on the focal plane array of the BSCPSI system, is the Fourier transform form of the Stokes vector, denotes the spatial frequency, denotes the carrier frequency of the interference fringes.

[0089] As can be seen from equation (11), the frequency domain corresponding to the intensity interference pattern of the BSCPSI contains seven parts, which are concentrated at , , , , By selecting appropriate filters to select the required channels, and then performing inverse Fourier transform, the target full polarization information can be demodulated.

[0090] (12)

[0091] wherein, , , , is the Stokes vector, is the Fourier transform form of the Stokes vector, denotes the carrier frequency of the interference fringes, is the inverse Fourier transform, is the real part of the complex number, is the imaginary part of the complex number.

[0092] Next, the ability of the BSCPSI system to obtain full polarization information is numerically simulated by MATLAB, and the Stokes parameters of the incident light are set as As shown in Figure 3 .

[0093] According to equation (7), the interference pattern on the focal plane array of the BSCPSI can be calculated as shown in Figure 4 , The axis and The interference fringes with light and shade are all in the axial direction.

[0094] The Fourier transform is performed on the interference figure, and the obtained spectrum diagram is as shown in Figure 5 The three-dimensional perspective view is as shown in Figure 6 From the figure, it can be clearly seen that there are 7 spectrum peak values. The central position is S 0 channel, the -45 degree direction is S 1 channel, and the up, down, left and right four peak values are S 23 Channel.

[0095] According to the carrier frequency selected by the theoretical calculation, a rectangular filter is used to intercept each channel information and frequency shift to the central position for inverse Fourier transform, and the target image is reconstructed as , , , As shown in Figure 7 .

[0096] In addition, it needs to be pointed out that the wide-band Sagnac snapshot full-polarization imaging system provided in the application can be applied to an endoscope, so as to significantly improve the image clarity.

[0097] The wide-band Sagnac snapshot full-polarization imaging system and endoscope provided by the application can combine two MDCPSI structures, divide the incident light into four different position shear beams, finally converge on the focusing plane array, form interference fringes about full Stokes parameters, realize wide-band full-polarization detection, effectively improve the image contrast, reduce the interference of reflected light, especially in the area where the blood flow has a greater influence, greatly improve the image observation ability, ensure the image clarity, and have strong practicability and are worth promoting.

[0098] The above disclosure is only the preferred specific embodiment of the application, but the embodiments of the application are not limited thereto, and any changes that can be thought of by those skilled in the art should fall within the protection scope of the application.

Claims

1. A broadband Sagnac snapshot full-polarimetric imaging system, characterized in that, The application relates to a polarization interference spectrum imaging system, which comprises a first unpolarized light beam splitter (1), a first MDCPSI system (2), a second MDCPSI system (3), a first plane mirror (4), a second plane mirror (5), a second unpolarized light beam splitter (6), a polarizer (7), a detector (8) and a processor (9), wherein the detector (8) and the processor (9) are electrically connected, the first unpolarized light beam splitter (1) and the second MDCPSI system (3) are arranged on a first optical axis at intervals, the first MDCPSI system (2) and the first unpolarized light beam splitter (1) are arranged on a second optical axis perpendicular to the first optical axis at intervals, the first plane mirror (4) and the second MDCPSI system (3) are arranged on a third optical axis at intervals, the third optical axis is perpendicular to the second optical axis and the first optical axis, the first plane mirror (4), the second unpolarized light beam splitter (6), the polarizer (7) and the detector (8) are arranged on a fourth optical axis at intervals in sequence, the fourth optical axis is parallel to the second optical axis, the second plane mirror (5) and the first MDCPSI system (2) are arranged on a fifth optical axis parallel to the first optical axis at intervals, and the second plane mirror (5) and the second unpolarized light beam splitter (6) are arranged on a sixth optical axis parallel to the third optical axis at intervals. The incident light is divided into two beams of identical light waves after passing through the first non-polarized light beam splitter (1) and The light waves and are respectively split by the first MDCPSI system (2) and the second MDCPSI system (3), and then are respectively transmitted and reflected by the second non-polarized light beam splitter (6) after the light paths are adjusted by the first plane mirror (4) and the second plane mirror (5) and the propagation directions are changed, and finally are imaged on the detector (8) through the polarizer (7), and the processor (9) completes extraction of the polarization interference information.

2. The wideband Sagnac snapshot full-polarimetric imaging system according to claim 1, characterized in that, The first plane mirror (4) is arranged obliquely and the included angle between the third optical axis and the fourth optical axis is 45 degrees, and the second plane mirror (5) is arranged obliquely and the included angle between the first plane mirror (4) and the second plane mirror (5) is 90 degrees.

3. The wideband Sagnac snapshot full-polarimetric imaging system according to claim 1, wherein, The first MDCPSI system (2) and the second MDCPSI system (3) have the same structure.

4. The wideband Sagnac snapshot full-polarimetric imaging system according to claim 3, characterized in that, The first MDCPSI system (2) comprises a third plane mirror (26) and a polarization beam splitter (22) arranged on a seventh optical axis at intervals, one side of the polarization beam splitter (22) is provided with a compensation plate (21), the compensation plate (21) is arranged close to the third plane mirror (26), a fourth plane mirror (23) and the polarization beam splitter (22) are arranged on an eighth optical axis perpendicular to the seventh optical axis at intervals, the fourth plane mirror (23) is located on the side away from the compensation plate (21), a first blazed grating (24) and a second blazed grating (25) are arranged reversely at intervals and located on the light path between the fourth plane mirror (23) and the third plane mirror (26), the first blazed grating (24) is close to the fourth plane mirror (23), the seventh optical axis is coaxially arranged with the fifth optical axis, and the eighth optical axis is coaxially arranged with the second optical axis.

5. The wideband Sagnac snapshot full-polarimetric imaging system according to claim 4, characterized in that, The polarization beam splitter (22) comprises a flat plate beam splitter and a narrow-band beam splitting film arranged in sequence, the compensation plate (21) is arranged close to the narrow-band beam splitting film, and the material and thickness of the compensation plate (21) are the same as those of the flat plate beam splitter.

6. The wideband Sagnac snapshot full-polarimetric imaging system according to claim 5, wherein, The distance between the polarization beam splitter (22) and the fourth plane mirror (23) and the third plane mirror (26) is the same.

7. The wideband Sagnac snapshot full-polarimetric imaging system according to claim 6, characterized in that, Geometric centers of the first unpolarized light beam splitter (1), the second unpolarized light beam splitter (6), the polarization beam splitter (22) in the first MDCPSI system (2), the polarization beam splitter (22) in the second MDCPSI system (3), the first plane mirror (4) and the second plane mirror (5) are located at the vertex of the same cube.

8. The wideband Sagnac snapshot full-polarimetric imaging system according to claim 7, characterized in that, The polarization beam splitter (22), the fourth plane mirror (23) and the third plane mirror (26) are arranged obliquely, and respectively meet the following relationships with the seventh optical axis and the eighth optical axis: ， ， Wherein, ɑ is an angle between the polarization beam splitter (22) and the seventh optical axis, and the unit is °, β is an angle between the polarization beam splitter (22) and the eighth optical axis, and the unit is °, γ is an angle between the fourth plane mirror (23) and the eighth optical axis, and the unit is °, φ is an angle between the third plane mirror (26) and the seventh optical axis, and the unit is °, and δ is a grating blaze angle of the first blazed grating (24) and the second blazed grating (25), and the unit is °.

9. The wideband Sagnac snapshot full-polarimetric imaging system according to claim 8, characterized in that, The δ is 20°-25°.

10. An endoscope characterized by comprising: The wide-band Sagnac snapshot full-polarization imaging system comprises the wide-band Sagnac snapshot full-polarization imaging system according to any one of claims 1-9.

Images