CN117270184B - Multimode optical fiber microscopic imaging system and method for breaking through diffraction limit resolution - Google Patents
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Abstract
The multimode optical fiber microscopic imaging system and method for breaking through diffraction limit resolution provided by the invention adopt a multimode optical fiber transmission matrix technical method, light emitted by a laser passes through a reference arm and a signal arm respectively, a spatial light modulator is used for controlling the amplitude and the phase of a light field of an input multimode optical fiber, a camera is used for collecting and storing information related to input and output of the multimode optical fiber, and the multimode optical fiber microscopic imaging method for breaking through diffraction limit resolution comprises the steps that the information of the multimode optical fiber transmission matrix is used, and the output light of the multimode optical fiber can be adjusted to generate an Airy spot with diffraction limit; the optical field phase of the Airy spot is combined with the vortex phase to generate a vortex beam, and the vortex beam is subjected to binarization processing and then uploaded to a spatial light modulator so as to output the vortex spot with zero central intensity at the multimode optical fiber. By performing point-by-point scanning using airy and vortex specks and collecting reflected light, subtracting the two obtained images, an image having a resolution twice the diffraction limit can be obtained.
Description
Technical Field
The invention belongs to the field of endoscope imaging, and particularly relates to a multimode optical fiber microscopic imaging system and method for breaking through diffraction limit resolution.
Background
With the rapid development of modern biomedicine, a precise medical treatment and an efficient diagnosis method are particularly important, and particularly in the development of brain science, a high-efficiency and precise imaging technology is particularly important for deep research on deep tissue structures of the brain.
The multimode optical fiber is used as a light transmission medium, can be used as an optical minimally invasive imaging probe by virtue of the size advantage of a thin hair, and is penetrated into brain tissues or other micro-structure cavities for endoscopic microscopic imaging with high spatial resolution.
Currently, multimode fiber microscopy imaging is mainly based on outputting an airy disk with diffraction limited resolving power at the end face of the multimode fiber, and obtaining an image by scanning the end of the fiber point by point, where the resolving power of the obtained image depends on the size of the airy disk used for scanning, and the size of the airy disk is completely determined by the numerical aperture size of the multimode fiber itself and the wavelength of the light source used. Therefore, in the case where the light source wavelength determination and the numerical aperture of the multimode fiber cannot be increased without limit, the obtained image resolution is limited by the diffraction limit point. For imaging observations of some fine structures, a higher imaging resolution is of paramount importance.
Therefore, how to solve the problem of improving the resolution of multimode optical fiber microscopic imaging, and providing a multimode optical fiber microscopic imaging system and method for breaking through the diffraction limit resolution are technical problems to be solved by those skilled in the art.
Disclosure of Invention
A first object of the present invention is to provide a multimode optical fiber microscopic imaging system that breaks through the diffraction limit resolution, aiming at the problem that the prior art cannot break through the diffraction limit imaging with multimode optical fibers.
For this purpose, the above object of the present invention is achieved by the following technical solutions:
a multimode optical fiber microscopic imaging system breaking through diffraction limit is characterized in that: comprising the steps of (a) a step of,
a light source polarizing beam splitter device: providing a narrow linewidth, monochromatic light source and splitting the light into two paths: a reference arm and a signal arm;
an illumination device of the signal arm providing uniform and collimated, single polarization gaussian beam illumination;
the optical transmission control device in the optical fiber realizes the regulation and control of the amplitude, the phase and the polarization of an optical mode transmitted in the multimode optical fiber;
the light transmission device of the reference arm provides uniform and collimated single-polarization Gaussian beam illumination to interfere with the light of the signal arm;
an optical signal beam expander for expanding the optical signal of the end face of the optical fiber end,
the optical signal beam combining and recording device combines the optical signals of the signal arm and the reference arm, then records,
the optical transmission control device in the optical fiber comprises a multimode optical fiber and a spatial light modulator, wherein the spatial light modulator adjusts the amplitude, the phase and the polarization state of a light beam entering the multimode optical fiber; the optical signal beam combination and recording device records input and output information at two ends of the multimode optical fiber, establishes an optical field corresponding relation between input and output of the multimode optical fiber, and constructs a transmission matrix of the multimode optical fiber according to the optical field corresponding relation;
the system is also provided with a data processing unit which is connected with the spatial light modulator and the optical signal beam combination and recording device, and utilizes the transmission matrix of the multimode optical fiber to precisely regulate and control the amplitude and the phase of the output light of the multimode optical fiber so as to generate diffraction limit Airy spots at the output end of the optical fiber; superposing the generated optical field phase of the Airy spot and the vortex phase to obtain the optical field of the vortex beam, generating the vortex spot with zero central intensity,
and scanning the imaged object point by utilizing the diffraction limit Airy spot and the vortex spot to obtain respective reconstructed images.
The invention can also adopt or combine the following technical proposal when adopting the technical proposal:
as a preferable technical scheme of the invention: the light source polarization beam splitter device comprises
The laser provides a light source, light output by the laser enters the isolator through the first half-wave plate to control the polarization state direction of the light, and the isolator prevents reflected light from returning to the laser;
the first reflecting mirror and the second reflecting mirror form two-dimensional position and coupling angle control for the coupling light beam, and control the subsequent coupling position and direction of the system light beam;
the second half wave plate is used for adjusting the light splitting proportion of the two-arm light paths;
the first lens and the second lens are used for expanding the laser beam;
the beam splitter divides the beam-expanded light into two arms, one arm is reference light, and the other arm is signal light.
As a preferable technical scheme of the invention: the beam splitter is used for splitting the beam-expanded light into two arms, wherein one arm is reference light and accounts for 1%; one arm is signal light and accounts for 99 percent.
As a preferable technical scheme of the invention: in the lighting device of the signal arm, signal light controls the polarization state through a fifth half-wave plate and is coupled into a second polarization maintaining optical fiber through a fifth lens; and the output light of the second polarization maintaining optical fiber is used for illuminating the spatial light modulator after the polarization state is controlled by the sixth half-wave plate and the sixth lens is collimated.
As a preferable technical scheme of the invention: in the optical transmission control device in the optical fiber, the polarization state of the light beam is controlled by the seventh half-wave plate after the signal light is diffracted by the spatial light modulator, and the light beam is coupled into the multimode optical fiber through the seventh lens, the spatial filter, the eighth lens and the first micro-objective lens.
As a preferable technical scheme of the invention: in the optical transmission device of the reference arm, the reference light is controlled in direction by a third reflector, the polarization state direction is controlled by a third half-wave plate, and the reference light is coupled into a first polarization-preserving optical fiber by a third lens; and the fourth lens collimates the output light of the first polarization maintaining optical fiber and controls the output light to enter the optical signal beam combining and recording device through the fourth half-wave plate.
As a preferable technical scheme of the invention: in the optical signal beam expander, the emergent beam from the multimode optical fiber is expanded by the second micro objective lens and the ninth lens;
the optical signal beam combining and recording device comprises a beam combiner and a camera, and the outgoing beam is combined with the reference arm to be finally recorded by the camera after being expanded.
As a preferable technical scheme of the invention: the amplitude and the phase of the output light of the multimode optical fiber are accurately regulated and controlled by utilizing the transmission matrix of the multimode optical fiber, and the output light is uploaded to the spatial light modulator by the data processing unit so as to regulate and control the multimode optical fiber, so that the optical fiber output end generates diffraction limit Airy spots.
As a preferable technical scheme of the invention: the optical field of the vortex beam is subjected to binary transcoding, and the transcoded hologram is uploaded to a spatial light modulator by a data processing unit so as to regulate and control the multimode optical fiber, so that the output end of the optical fiber generates a vortex spot with zero central intensity.
A second object of the present invention is to provide a multimode optical fiber microscopic imaging method that breaks through the diffraction limited resolution.
For this purpose, the above object of the present invention is achieved by the following technical solutions:
a multimode optical fiber microscopic imaging method based on breaking diffraction limit resolution is characterized in that: comprises the steps of,
adjusting the amplitude, phase and polarization state of a light beam entering the multimode optical fiber through a spatial light modulator;
recording input and output information at two ends of the multimode optical fiber, and associating the corresponding relation between the input and the output of the input and the output information to form a multimode optical fiber transmission matrix;
the information in the multimode optical fiber transmission matrix is utilized to regulate and control the amplitude and the phase of the output light of the multimode optical fiber, so that the Airy spot with diffraction limit is output at the output end of the optical fiber;
superposing the optical field phase of the Airy spot with the diffraction limit and the vortex phase to obtain the optical field of the vortex beam, performing binary transcoding on the optical field of the vortex beam, and uploading the transcoded hologram to a spatial light modulator so as to output the vortex spot with zero central intensity at the output end of the optical fiber;
the method comprises the steps of performing point-by-point scanning on an object to be imaged by using an airy disk and a vortex disk with diffraction limit, collecting light reflected by the object to be imaged, and reconstructing an image of the light through the same multimode optical fiber to obtain two images of Img1 and Img2;
according to the relation img1-k·img2=img, where K is an intensity coefficient, img is an image breaking through diffraction limit resolution, and the spatial resolution of an Img image is twice that of an Img1 image obtained by airy spot scanning alone.
The invention has the following beneficial effects: according to the multimode optical fiber microscopic imaging system and method breaking through the diffraction limit, two light spots are generated at the output end of the multimode optical fiber and are scanned, imaged and subtracted respectively, so that the resolution capability twice as high as the diffraction limit can be achieved, the problem that the diffraction limit cannot be broken through by utilizing multimode optical fiber microscopic imaging is solved, a plurality of wavelength light sources and complex system designs are not needed, and the multimode optical fiber microscopic imaging method with a simple data processing mode is provided.
Drawings
FIG. 1 is a schematic diagram of a multimode fiber microimaging system for breaking through diffraction limited resolution in accordance with the present invention;
FIG. 2 is a diagram of a multimode fiber microimaging method and procedure based on breaking through diffraction limited resolution;
FIG. 3 is a comparison of the Airy spot acquisition image with the eddy current subtraction to obtain an image in terms of spatial frequency and contrast;
FIG. 4 is a partial magnified image comparison of an Airy spot obtained image and an image obtained by subtracting eddy currents;
FIG. 5 is a graph showing the comparison of the resolution of the Airy light spot and the two light spots generated at the output end of the multimode fiber of the present invention after subtraction;
in the accompanying drawings: 1-a laser; 2-a first half-wave plate; 3-an isolator; 4-a first mirror; 5-a second mirror; 6-a second half-wave plate; 7-a first lens; 8-a second lens; 9-beam splitters; 10-a fourth half-wave plate; 11-a fifth lens; 12-a second polarization maintaining fiber; 13-a fifth half-wave plate; 14-a sixth lens; 15-a spatial light modulator; 16-a sixth half-wave plate; 17-seventh lens; 18-a spatial filter; 19-eighth lens; 20-a first microscope objective; 21-multimode optical fiber; 22-a third mirror; 23-a third half-wave plate; 24-a third lens; 25-a first polarization maintaining fiber; 26-fourth lens; 27-a fourth half-wave plate; 28-a second microobjective; 29-a ninth lens; 30-beam combiner; 31-camera.
Detailed Description
The invention will be described in further detail with reference to the drawings and specific embodiments.
The invention provides a multimode optical fiber microscopic imaging device and a multimode optical fiber microscopic imaging method for breaking through diffraction limit resolution, which are multimode optical fiber microscopic imaging devices for breaking through diffraction limit, and comprise the following steps:
and a laser configured to provide a light source for the system. The light beam output from the laser is transmitted into the isolator after polarization state control is performed by the first half wave plate. The function of this isolator is to prevent reflected light in the system from returning to the laser.
A first mirror and a second mirror, which function to adjust the coupling position and direction of the light beam.
And the second half wave plate is used for adjusting the light path splitting ratio between the two arms of the system.
A first lens and a second lens which perform beam expansion processing mainly for expanding the laser beam.
A beam splitter configured to split the expanded light into two paths: the beam splitter divides the beam-expanded light into two arms, one arm is the reference light, the other arm is the signal light,
a portion of a reference arm comprising:
a third mirror for beam direction control;
a third half-wave plate for controlling the polarization state;
a third lens coupling the light beam into the first polarization maintaining fiber;
and the fourth lens and the fourth half-wave plate are respectively used for collimating the output light beam of the first polarization-maintaining optical fiber and further controlling the polarization state, and then the light beam is transmitted into the beam combiner.
The reference light is controlled in direction by a third reflector, the polarization state direction is controlled by a third half-wave plate, the reference light is coupled into a first polarization-preserving optical fiber by a third lens, and the output light of the first polarization-preserving optical fiber is collimated by a fourth lens and is controlled to enter a beam combiner by a fourth half-wave plate;
signal arm portion, involving:
a fifth half-wave plate and a fifth lens for polarization state control and coupling the light beam into a second polarization maintaining fiber, respectively;
a sixth lens for collimating the output beam of the second polarization maintaining fiber and irradiating the output beam to the spatial light modulator;
after the light beam passes through the spatial light modulator, the polarization state is controlled by a sixth half-wave plate, and then the light beam passes through a seventh lens, a spatial filter, an eighth lens and a first micro-objective lens and is finally coupled into a multimode optical fiber;
the beam output from the multimode optical fiber is expanded by the second microscope objective and the ninth lens and combined with the beam of the reference arm in the beam combiner, and the combined beam is finally captured and recorded by the camera.
The signal light is controlled to be polarized through a fifth half-wave plate and is coupled into a second polarization maintaining optical fiber through a fifth lens; the output light of the second polarization maintaining optical fiber is used for illuminating the spatial light modulator after the polarization state is controlled by the sixth half-wave plate and the collimation of the sixth lens; the light beam after being diffracted by the spatial light modulator is controlled in polarization state by a seventh half-wave plate, and is coupled into the multimode optical fiber through a seventh lens, a spatial filter, an eighth lens and a first micro-objective lens; the emergent beam from the multimode optical fiber is expanded by the second micro-objective lens and the ninth lens and combined with the reference arm at the beam combiner, and finally recorded by the camera.
On the basis of the device, the invention provides a multimode optical fiber microscopic imaging method capable of breaking through diffraction limit resolution. The method specifically comprises the following steps:
with a spatial light modulator we can adjust the amplitude, phase and polarization state of the beam entering the multimode fiber;
and recording input and output information at two ends of the multimode optical fiber, thereby establishing an optical field corresponding relation between input and output of the multimode optical fiber and constructing a transmission matrix of the multimode optical fiber according to the optical field corresponding relation.
The optical phase and amplitude are precisely controlled by the spatial light modulator to produce a specific pattern, i.e., a plurality of different incident light modes, which are input to the optical fiber. When the optical modes are transmitted through the multimode optical fiber, the optical modes interact in the multimode optical fiber and generate different optical field distributions at the output end of the optical fiber, and the output optical fields are recorded, so that the optical field complex amplitude corresponding relation between the input and the output is accurately established. And constructing a transmission matrix of the multimode optical fiber based on the interrelation between different input modes and different output modes.
By utilizing the information in the transmission matrix, the amplitude and the phase of the output light of the multimode optical fiber can be accurately regulated and controlled, so that diffraction limit Airy spots are generated at the output end of the optical fiber;
and superposing the generated optical field phase of the Airy spot and the vortex phase to obtain an optical field of the vortex beam, performing binarization transcoding on the optical field of the vortex beam, and uploading the transcoded hologram to the spatial light modulator. Thus, vortex spots with zero center strength can be generated at the output end of the optical fiber;
the object to be imaged is scanned point by point using the airy and the vortex speckles. Collecting light reflected by an imaged object, and reconstructing an image of the light through the same multimode optical fiber to obtain two images of Img1 and Img2;
the two images are subtracted from each other according to the relation img1-k·img2=img, and corrected by an appropriate intensity coefficient k, thereby obtaining an image Img that breaks through the diffraction limit resolution. The spatial resolution of this new Img image is twice that of the Img1 image obtained using airy spot scanning alone.
Where the vortex phase is the optical field phase corresponding to a spot with zero center intensity.
As shown in fig. 1, in the multimode optical fiber microscopic imaging device breaking through diffraction limit provided by the invention, a laser 1 is used for providing a light source for a system, light output by the laser 1 enters an isolator 3 through controlling the polarization state direction of the light by a first half-wave plate 2, and the isolator 3 is used for preventing the system light from reflecting into the laser; the first reflecting mirror 4 and the second reflecting mirror 5 are used for controlling the subsequent coupling position and direction of the system light beam, so as to form two-dimensional position and coupling angle control of the coupled light beam; the second half wave plate 6 is used for adjusting the light splitting proportion of the two-arm light paths of the system; the first lens 7 and the second lens 8 are used for expanding the laser beam; the beam splitter 9 is used for splitting the beam-expanded light into two arms, wherein one arm is reference light and the other arm is signal light;
the reference arm light is controlled in direction by a third reflector 22, and the polarization state direction is controlled by a third half-wave plate 23, and is coupled into a first polarization-preserving fiber 25 by a third lens 24; the fourth lens 26 collimates the output light of the first polarization maintaining fiber 25, and the output light enters the beam combiner 30 through the fourth half-wave plate 27;
the polarization state of the signal arm light is controlled by a fifth half wave plate 10 and is coupled into a second polarization maintaining optical fiber 12 by a fifth lens 11; the output light of the second polarization maintaining optical fiber 12 is collimated by the sixth half-wave plate 13 and the sixth lens 14 for illuminating the spatial light modulator 15; the polarization state of the light beam after being diffracted by the spatial light modulator 15 is controlled by the seventh half-wave plate 16, and the light beam is coupled into the multimode optical fiber 21 via the seventh lens 17, the spatial filter 18, the eighth lens 19 and the first micro objective lens 20; the outgoing beam from the multimode optical fiber 21 is expanded by the second microscope objective 28 and the ninth lens 29 and combined with the reference arm at the combiner, and finally recorded by the camera 31.
As shown in fig. 2, the present invention provides a multimode optical fiber microscopic imaging method based on resolution breaking diffraction limit, which changes the amplitude, phase and polarization state of a light beam entering a multimode optical fiber 21 through a spatial light modulator 15, records and associates the input and output information at two ends of the multimode optical fiber 21, thereby forming a multimode optical fiber transmission matrix, and utilizes the information of the transmission matrix to regulate and control the amplitude and phase of the output light of the multimode optical fiber, so as to output airy disk with diffraction limit at the output end of the optical fiber; meanwhile, the light field phase of the generated Airy spot and the vortex phase are overlapped to obtain the light field of the vortex light beam, the vortex light beam light field is subjected to binary transcoding and uploaded to a spatial light modulator, and the vortex spot with zero light field center intensity can be output at the optical fiber output end; the method comprises the steps of performing point-by-point scanning on an imaged object by utilizing airy white and vortex spots respectively, collecting and reconstructing images of light reflected by the imaged object through the same multimode optical fiber, and obtaining an image Img1 and an image Img2 respectively; the two images are subtracted by the relation img1-k.img2=img, and an image Img with the resolution capability breaking through the diffraction limit is finally obtained through the intensity coefficient k, and the spatial resolution capability of the obtained new image Img is twice that of the image Img1 obtained by using the airy spot scanning.
Example 1
As shown in fig. 3, with the multimode fiber microscopic imaging device and method based on breaking diffraction limit resolution provided by the invention, an object to be imaged is placed at the tail end of the multimode fiber 21, and an airy disk and a vortex disk are output at the end face of the multimode fiber 21 and are scanned and imaged respectively, as compared with the image in fig. 3, the image obtained by the method of the invention is more than twice as high as a general diffraction limit point scanning image in terms of resolvable spatial frequency and contrast.
The left image of fig. 3 shows the image obtained from the diffraction limited airy disk, and the numbers "8" and "9" as well as some fine fringes and lattices can be seen. The right image shows the focus image after the eddy current subtraction processing. The edge details at the numbers and fringes are more clear than the left image. The lower graph depicts the upper image contrast versus spatial frequency, with the horizontal axis representing spatial frequency, expressed in cycles per unit distance. The higher the spatial frequency, the less detail in the representative image. Where the vertical axis represents contrast, ranging from 0 to 1, where 1 represents the highest possible contrast, i.e. full black and white contrast, and 0 represents no contrast, i.e. all areas on the image are uniformly bright. The blue curve represents the variation of the contrast of the image obtained by diffraction limited airy disk with spatial frequency. As the spatial frequency increases, the contrast decreases, which indicates that details become indistinguishable.
The orange curve represents the change of the contrast of the image subjected to vortex light subtraction with the spatial frequency, and the curve is positioned above the blue curve, so that the image subjected to vortex light subtraction has higher contrast under the same spatial frequency, and the image subjected to vortex light subtraction has higher image resolution frequency under the same contrast. In addition, fig. 4 shows a comparison of the partial enlarged images.
The left side of fig. 5 shows the airy disk, the vortex disk, and the one-dimensional light field distribution curve after subtraction of the two, respectively, and the right side of fig. 5 shows the direct comparison of the airy disk and the subtracted disk. The size of the one-dimensional light field distribution curve at the half-width position directly reflects the resolution capability of the light spot, and the right side image shows that the half-width of the subtracted light spot is smaller than the half-width of the Airy spot, so that the image reconstruction performed by using the subtracted light spot has higher spatial resolution compared with the image obtained by the Airy spot scanning. The image obtained by the airy spot scanning is an image with a diffraction limit, and therefore, the image reconstruction by the subtracted light spots has a resolution capability of breaking through the diffraction limit.
The above detailed description is intended to illustrate the present invention by way of example only and not to limit the invention to the particular embodiments disclosed, but to limit the invention to the precise embodiments disclosed, and any modifications, equivalents, improvements, etc. that fall within the spirit and scope of the invention as defined by the appended claims.
Claims (9)
1. A multimode optical fiber microscopic imaging system breaking through diffraction limit is characterized in that: comprising the steps of (a) a step of,
a light source polarizing beam splitter device: providing a narrow linewidth, monochromatic light source and splitting the light into two paths: a reference arm and a signal arm;
an illumination device of the signal arm providing uniform and collimated, single polarization gaussian beam illumination;
the optical transmission control device in the optical fiber realizes the regulation and control of the amplitude, the phase and the polarization of an optical mode transmitted in the multimode optical fiber;
the light transmission device of the reference arm provides uniform and collimated single-polarization Gaussian beam illumination to interfere with the light of the signal arm;
an optical signal beam expander for expanding the optical signal of the end face of the optical fiber end,
the optical signal beam combining and recording device combines the optical signals of the signal arm and the reference arm, then records,
the optical transmission control device in the optical fiber comprises a multimode optical fiber and a spatial light modulator, wherein the spatial light modulator adjusts the amplitude, the phase and the polarization state of a light beam entering the multimode optical fiber; the optical signal beam combination and recording device records input and output information at two ends of the multimode optical fiber, establishes an optical field corresponding relation between input and output of the multimode optical fiber, and constructs a transmission matrix of the multimode optical fiber according to the optical field corresponding relation;
the system is also provided with a data processing unit which is connected with the spatial light modulator and the optical signal beam combination and recording device, and utilizes the transmission matrix of the multimode optical fiber to precisely regulate and control the amplitude and the phase of the output light of the multimode optical fiber so as to generate diffraction limit Airy spots at the output end of the optical fiber; superposing the generated optical field phase of the Airy spot and the vortex phase to obtain the optical field of the vortex beam, generating the vortex spot with zero central intensity,
utilizing diffraction limit Airy spot and vortex spot to scan the imaged object point by point to obtain respective reconstructed images;
in the lighting device of the signal arm, signal light controls the polarization state through a fifth half-wave plate and is coupled into a second polarization maintaining optical fiber through a fifth lens; and the output light of the second polarization maintaining optical fiber is used for illuminating the spatial light modulator after the polarization state is controlled by the sixth half-wave plate and the sixth lens is collimated.
2. A diffraction limited-breakthrough multimode fiber microimaging system as in claim 1, wherein: the light source polarization beam splitter device comprises
The laser provides a light source, light output by the laser enters the isolator through the first half-wave plate to control the polarization state direction of the light, and the isolator prevents reflected light from returning to the laser;
the first reflecting mirror and the second reflecting mirror form two-dimensional position and coupling angle control for the coupling light beam, and control the subsequent coupling position and direction of the system light beam;
the second half wave plate is used for adjusting the light splitting proportion of the two-arm light paths;
the first lens and the second lens are used for expanding the laser beam;
the beam splitter divides the beam-expanded light into two arms, one arm is reference light, and the other arm is signal light.
3. A diffraction-limited-breakthrough multimode fiber microimaging system as in claim 2, wherein: the beam splitter (9) is used for splitting the beam-expanded light into two arms, wherein one arm is reference light and accounts for 1%; one arm is signal light and accounts for 99 percent.
4. A diffraction limited-breakthrough multimode fiber microimaging system as in claim 1, wherein: in the optical transmission control device in the optical fiber, the polarization state of the light beam is controlled by the seventh half-wave plate after the signal light is diffracted by the spatial light modulator, and the light beam is coupled into the multimode optical fiber through the seventh lens, the spatial filter, the eighth lens and the first micro-objective lens.
5. A diffraction limited-breakthrough multimode fiber microimaging system as in claim 1, wherein: in the optical transmission device of the reference arm, the reference light is controlled in direction by a third reflector, the polarization state direction is controlled by a third half-wave plate, and the reference light is coupled into a first polarization-preserving optical fiber by a third lens; and the fourth lens collimates the output light of the first polarization maintaining optical fiber and controls the output light to enter the optical signal beam combining and recording device through the fourth half-wave plate.
6. A diffraction limited-breakthrough multimode fiber microimaging system as in claim 1, wherein: in the optical signal beam expander, the emergent beam from the multimode optical fiber is expanded by the second micro objective lens and the ninth lens;
the optical signal beam combining and recording device comprises a beam combiner and a camera, and the outgoing beam is combined with the reference arm to be finally recorded by the camera after being expanded.
7. A diffraction limited-breakthrough multimode fiber microimaging system as in claim 1, wherein: the amplitude and the phase of the output light of the multimode optical fiber are accurately regulated and controlled by utilizing the transmission matrix of the multimode optical fiber, and the output light is uploaded to the spatial light modulator by the data processing unit so as to regulate and control the multimode optical fiber, so that the optical fiber output end generates diffraction limit Airy spots.
8. A diffraction limited-breakthrough multimode fiber microimaging system as in claim 1, wherein: the optical field of the vortex beam is subjected to binary transcoding, and the transcoded hologram is uploaded to a spatial light modulator by a data processing unit so as to regulate and control the multimode optical fiber, so that the output end of the optical fiber generates a vortex spot with zero central intensity.
9. A method for use in a multimode optical fiber microimaging system for breaking diffraction limited in any of claims 1-8, comprising: comprises the steps of,
adjusting the amplitude, phase and polarization state of a light beam entering the multimode optical fiber through a spatial light modulator;
recording input and output information at two ends of the multimode optical fiber, and associating the corresponding relation between the input and the output of the input and the output information to form a multimode optical fiber transmission matrix;
the information in the multimode optical fiber transmission matrix is utilized to regulate and control the amplitude and the phase of the output light of the multimode optical fiber, so that the Airy spot with diffraction limit is output at the output end of the optical fiber;
superposing the optical field phase of the Airy spot with the diffraction limit and the vortex phase to obtain the optical field of the vortex beam, performing binary transcoding on the optical field of the vortex beam, and uploading the transcoded hologram to a spatial light modulator so as to output the vortex spot with zero central intensity at the output end of the optical fiber;
the method comprises the steps of performing point-by-point scanning on an object to be imaged by using an airy disk and a vortex disk with diffraction limit, collecting light reflected by the object to be imaged, and reconstructing an image of the light through the same multimode optical fiber to obtain two images of Img1 and Img2;
according to the relation img1-k·img2=img, where K is an intensity coefficient, img is an image breaking through diffraction limit resolution, and the spatial resolution of an Img image is twice that of an Img1 image obtained by airy spot scanning alone.
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