CN112258628A - Imaging system and method based on grating phase contrast - Google Patents
Imaging system and method based on grating phase contrast Download PDFInfo
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- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/42—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect
- G02B27/4205—Diffraction optics, i.e. systems including a diffractive element being designed for providing a diffractive effect having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant
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Abstract
The invention provides an imaging system and method based on grating phase contrast, which relate to the field and comprise the following steps: light source means for emitting partially coherent light; collimating means for converting the partially coherent light into collimated light; the sample is placed above the grating component, collimated light is sequentially irradiated on the sample by a plurality of irradiation angles to form refracted light rays respectively, and the refracted light rays are processed by the grating component to form light signals with variable intensity; an image detector for receiving the optical signals to form a phase contrast image of the sample corresponding to each illumination angle; and the three-dimensional reconstruction system is used for performing three-dimensional reconstruction according to each phase contrast image to obtain a three-dimensional image of the sample. The method has the advantages of having the characteristics of large visual field and high resolution of lensless imaging, reducing the complexity of the system, reducing the complexity of operation and the volume of imaging equipment, further improving the integration level of the equipment, and better promoting the practicability of the lensless phase recovery system.
Description
Technical Field
The invention relates to the technical field of phase recovery, in particular to an imaging system and method based on grating phase contrast.
Background
Phase recovery is an important issue in the field of optical measurement and imaging technology. In certain fields, such as optical measurements, material physics, adaptive optics, X-ray diffraction optics, electron microscopy, biomedical imaging, most samples belong to phase objects. Such objects have a uniform amplitude transmission distribution, but a non-uniform spatial distribution of refractive index or thickness, so that the phase object has a small change in the amplitude of the light wave and a very large change in the phase. Human eyes or other optical detectors can only determine the amplitude change of an object and cannot determine the phase change of the object, so that the phase object cannot be seen, namely, the parts with different thicknesses or refractive indexes in the phase object cannot be distinguished. Therefore, it is important to acquire phase information in these fields.
Since it is very difficult to directly measure the phase distribution of the optical wave field, it is very easy to measure the amplitude or intensity of the optical wave field. Therefore, the process of recovering the phase from the intensity distribution can be regarded as a mathematically inverse problem, i.e., a phase recovery problem. Non-interference based phase recovery methods can be broadly divided into two broad categories, namely iterative and direct methods.
An iterative method: the iterative algorithm-based phase restoration method was first proposed in 1972 by Gerchberg et al in the study of the phase restoration problem of electron microscopes, and is called GS (Gerchberg-Saxton) algorithm. The method indicates that when the light intensity distribution of the light wave field to be measured on the image plane and the far field diffraction plane is known, the light field wave front phase can be solved in a diffraction calculation iteration mode. The proposal of the GS algorithm has an innovative meaning, but has a plurality of problems. These problems are inherent in solving the inverse problem, such as the existence and uniqueness of the solution. On the other hand, the algorithm is caused by the iterative algorithm itself, for example, the algorithm is slowed down in convergence speed after the first few iterations, even falls into stagnation, and falls into a local (non-global) minimum value.
The direct method comprises the following steps: the light intensity transmission equation was first derived by Teague in 1983 using helmholtz's equation under paraxial approximation. TIE is a second-order elliptic partial differential equation that clarifies the quantitative relationship between the amount of change in light intensity in the direction parallel to the optical axis and the phase of the light wave in the plane perpendicular to the optical axis. The method is different from an iterative phase recovery algorithm and has the great characteristic that the traditional diffraction calculation formula is not used for iteratively recovering the phase, and the phase information is directly obtained by numerically solving a light intensity transmission equation under the condition that the light intensity distribution (direct measurement) on a plane to be solved and the light intensity axial differential (obtained by collecting defocused light intensity and carrying out numerical difference estimation), so that any iterative solution process is not needed.
At present, most phase recovery researches at home and abroad are carried out on a microscope system. However, the inherent contradiction of the difficulty of obtaining high resolution of a microscope system with a large field of view limits its further practical application. The lens-free imaging technology has the characteristics of large visual field and high resolution, but the operation is complicated and the algorithm complexity is high aiming at the lens-free phase recovery technology at present, so that the lens-free imaging technology is difficult to be widely applied in practice.
Disclosure of Invention
To solve the problems in the prior art, the present invention provides an imaging system based on grating phase contrast, comprising:
a light source device for emitting partially coherent light;
the collimating device is arranged at the light ray exit port of the light source device and is used for converting the partially coherent light into collimated light;
the grating assembly is arranged below the collimating device, a sample is placed above the grating assembly, collimated light is sequentially irradiated on the sample by a plurality of irradiation angles to form refracted light rays respectively, and the refracted light rays are processed by the grating assembly to form optical signals with variable intensity;
an image detector disposed below the grating assembly for receiving the optical signals to form a phase contrast image of the sample corresponding to each of the illumination angles;
and the three-dimensional reconstruction system is connected with the image detector and is used for carrying out three-dimensional reconstruction according to each phase contrast image to obtain a three-dimensional image of the sample.
Preferably, the three-dimensional reconstruction system includes:
a first processing unit, configured to extract light intensity values of pixels in each phase contrast image, and calculate a first ratio between the light intensity values of the pixels in an even-numbered row and the light intensity values of the pixels in an odd-numbered row;
the second processing unit is connected with the first processing unit and used for obtaining the corresponding incident angle of the refraction light incident to the grating component according to the first ratio;
and the reconstruction unit is connected with the second processing unit and is used for performing three-dimensional reconstruction according to each incident angle to obtain a three-dimensional image of the sample.
Preferably, the three-dimensional reconstruction system further comprises a preprocessing unit connected to the second processing unit, the preprocessing unit comprising:
the image acquisition module is used for acquiring a reference image which is acquired by the image detector and corresponds to each illumination angle, wherein the collimated light is directly illuminated on the grating assembly by a plurality of preset illumination angles when the sample is not placed above the grating assembly;
the image processing module is connected with the image acquisition module and used for respectively extracting the light intensity values of all the pixel points in each reference image and calculating a second ratio between the light intensity values of the pixel points positioned in an even row and the light intensity values of the pixel points positioned in an odd row;
the data storage module is respectively connected with the image acquisition module and the image processing module and is used for establishing and storing a corresponding relation curve between the irradiation angle and the corresponding second ratio;
and the second processing unit matches the corresponding first ratio in each phase contrast image in the corresponding relation curve to obtain the corresponding irradiation angle as the incident angle.
Preferably, the grating assembly is integrated above the image detector.
Preferably, the image detector is an area array detector including a plurality of pixels.
Preferably, the grating assembly includes a first grating and a second grating, and the first grating and the second grating are perpendicular to each other.
Preferably, a range of a pitch between the first grating and the second grating is [400 nm, 600 nm ].
Preferably, the first grating and the second grating are made of a metal material, and the thickness of the metal material ranges from [100 nanometers to 300 nanometers ].
Preferably, the period of the first grating has a value range of [400 nm, 600 nm ], and the period of the second grating has a value range of [800 nm, 1000 nm ].
Preferably, the collimated light is tilted at different angles along the X-axis or Y-axis of the image detector to form the illumination angle.
Preferably, the value range of the irradiation angle is [ -90 degrees, 90 degrees ].
An imaging method based on grating phase contrast is applied to the imaging system based on grating phase contrast, and comprises the following steps:
step S1, emitting partial coherent light;
step S2, converting the partially coherent light into collimated light;
step S3, the collimated light is irradiated on the sample placed on the grating component by a plurality of irradiation angles to respectively form refracted light rays, and the refracted light rays are processed by the grating component to form light signals with variable intensity;
step S4, receiving the optical signals to form a phase contrast image of the sample corresponding to each illumination angle;
and step S5, performing three-dimensional reconstruction according to each phase contrast image to obtain a three-dimensional image of the sample.
Preferably, the step S5 includes:
step S51, extracting the light intensity value of each pixel point in each phase contrast image respectively, and calculating a first ratio between the light intensity value of the pixel point positioned on the even-numbered line and the light intensity value of the pixel point positioned on the odd-numbered line;
step S52, according to each first ratio, the corresponding incident angle of the refraction light to the grating component is obtained through processing;
and step S53, performing three-dimensional reconstruction according to each incident angle to obtain a three-dimensional image of the sample.
Preferably, before executing the step S52, a preprocessing process is further included, including:
step A1, when the sample is not placed above the grating assembly, the collimated light is directly irradiated on the grating assembly by a plurality of preset irradiation angles, and the reference image corresponding to each irradiation angle is acquired by the image detector;
step A2, extracting the light intensity value of each pixel point in each reference image respectively, and calculating a second ratio between the light intensity value of the pixel point positioned on the even-numbered line and the light intensity value of the pixel point positioned on the odd-numbered line;
step A3, establishing a corresponding relation curve between the irradiation angle and the corresponding second ratio and storing the corresponding relation curve;
in the step S52, the corresponding irradiation angle is obtained as the incident angle by matching the corresponding first ratio in each phase contrast image with the corresponding relationship curve.
The technical scheme has the following advantages or beneficial effects: the grating component is combined with the image detector, so that the imaging system has the characteristics of large field of view and high resolution without lens imaging, the complexity of the system is reduced, the complexity of operation and the volume of imaging equipment are reduced, the integration level of the equipment is further improved, and the practicability of the lens-free phase recovery system can be better promoted.
Drawings
FIG. 1 is a schematic diagram of a grating-based phase contrast imaging system according to a preferred embodiment of the present invention;
FIG. 2 is a schematic diagram of an imaging system based on grating phase contrast in accordance with a preferred embodiment of the present invention;
FIG. 3 is a diagram illustrating a corresponding relationship curve according to a preferred embodiment of the present invention;
FIG. 4 is a reference image recorded by the image detector when no sample is placed in the preferred embodiment of the present invention;
FIG. 5 is a phase contrast image recorded by an image detector after a sample is placed in accordance with a preferred embodiment of the present invention;
FIG. 6 is a diagram illustrating a three-dimensional reconstruction result according to a preferred embodiment of the present invention;
FIG. 7 is a schematic diagram of a grating assembly according to a preferred embodiment of the present invention;
FIG. 8 is a flow chart illustrating an imaging method based on grating phase contrast according to a preferred embodiment of the present invention;
FIG. 9 is a schematic diagram illustrating a process of three-dimensional reconstruction based on phase contrast images according to a preferred embodiment of the present invention;
FIG. 10 is a flow chart illustrating a pre-treatment process according to a preferred embodiment of the present invention.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. The present invention is not limited to the embodiment, and other embodiments may be included in the scope of the present invention as long as the gist of the present invention is satisfied.
In accordance with the above-mentioned problems in the prior art, there is provided in a preferred embodiment of the present invention an imaging system based on grating phase contrast, as shown in fig. 1 and 2, comprising:
a light source device 1 for emitting partially coherent light;
the collimating device 2 is arranged at a light ray exit port of the light source device 1 and is used for converting the partially coherent light into collimated light;
the grating component 3 is arranged below the collimating device 2, a sample 4 is placed above the grating component 3, collimated light is sequentially irradiated on the sample 4 by a plurality of irradiation angles to form refracted light rays respectively, and the refracted light rays are processed by the grating component 3 to form optical signals with variable intensity;
an image detector 5 disposed below the grating assembly 3 for receiving the optical signal to form a phase contrast image of the sample 4 corresponding to each illumination angle;
and the three-dimensional reconstruction system 6 is connected with the image detector 5 and is used for carrying out three-dimensional reconstruction according to each phase contrast image to obtain a three-dimensional image of the sample.
In particular, in the imaging field, in order to obtain a large field of view on the premise of high resolution, a commonly used technical means is image splicing, but in order to do so, precise mechanical movement and complex algorithm calculation are required, which is not only time-consuming but also low in precision. To further address this issue, lensless imaging is a trend. In the present embodiment, by combining the grating assembly 3 and the image detector 5, it is possible to apply the lens-less imaging technology in the field of phase contrast imaging.
In a preferred embodiment, the light source device 1 may be an LED light source, the collimator device 2 and the light source device 1 may be integrally provided, and the irradiation directions of the light source device 1 and the collimator device 2 may be adjusted in synchronization when adjusting the irradiation angle of the collimated light. Part of coherent light generated by the light source device 1 is converted into collimated light through the collimator, the collimated light is parallel light, when the parallel light irradiates a sample 4 and penetrates through the sample, physical phenomena such as absorption, scattering, refraction and the like can occur, refracted emergent light carries material information in a specific spatial position, through arranging the grating component 3 between the sample 4 and the image detector 5, the emergent light can generate phase change information through the grating component 3, the appearance of the phase change information is represented as light intensity change, namely, the emergent light can form an optical signal with changed intensity after passing through the grating component 3, the optical signal with changed intensity contains refraction angle information of the refracted light, and finally, the image detector 5 receives the optical signal with the phase change information and records the optical signal to form a phase contrast image. Since the phase contrast image includes phase change information generated by the collimated light irradiating the sample 4, the three-dimensional reconstruction system 6 can perform three-dimensional reconstruction on the phase distribution inside the sample 4 according to the phase contrast images of different irradiation angles, thereby obtaining a three-dimensional image of the sample 4. The whole imaging system has the characteristics of large visual field and high resolution of lensless imaging, reduces the complexity of the system, only needs to adjust the irradiation angle, saves complex operation, and can better promote the practicability of the lensless phase recovery system.
In a preferred embodiment, the plurality of illumination angles includes at least three illumination angles, which may be an illumination angle perpendicular to the surface of the image detector 5 and an illumination angle shifted by 10 degrees to the left or right from the perpendicular illumination angle, so that the image detector 5 records three phase contrast images corresponding to the three illumination angles.
As a preferred embodiment, the three-dimensional reconstruction system 6 comprises:
a first processing unit 61, configured to extract light intensity values of pixels in each phase contrast image, and calculate a first ratio between the light intensity values of the pixels in the even-numbered rows and the light intensity values of the pixels in the odd-numbered rows;
the second processing unit 62 is connected to the first processing unit 61 and is configured to obtain an incident angle at which the corresponding refracted light beam enters the grating assembly 3 according to each first ratio;
and the reconstruction unit 63 is connected with the second processing unit 62 and is used for performing three-dimensional reconstruction according to each incident angle to obtain a three-dimensional image of the sample.
In a preferred embodiment, when the sample 4 is irradiated with collimated light at a perpendicular irradiation angle, for example, at a perpendicular irradiation angle to the surface of the image detector 5, the refractive index or thickness of the inside of the sample is non-uniform, which changes the wave surface perpendicular to the collimated light, and the propagation direction of the collimated light is coincident with the normal of the wave surface inside the sample 4. The second processing unit 62 preferably recovers the angle of the light refracted at different points after passing through the sample by using the established corresponding relationship curve between the incident angle and the ratio, and further recovers the wavefront after passing through the sample, so that the wavefront can recover the refractive index distribution and the three-dimensional structure inside the sample. For a detailed process of recovering the internal refractive index distribution and three-dimensional structure of a sample from a wavefront, refer to this document: "Boundary-aspect-free phase with the transport of interest for the applications chromatography" (Optics express, Vol.22, No. 15, p.18310, p.18324, 2014).
In a preferred embodiment, the three-dimensional reconstruction system 6 further comprises a preprocessing unit 64 connected to the second processing unit 62, the preprocessing unit 64 comprising:
an image obtaining module 641, configured to obtain a reference image corresponding to each illumination angle acquired by the image detector, where collimated light is directly illuminated on the grating assembly at a plurality of predetermined illumination angles when no sample is placed above the grating assembly;
the image processing module 642 is connected to the image obtaining module 641 and configured to extract the light intensity values of the pixels in each reference image, and calculate a second ratio between the light intensity values of the pixels in the even-numbered rows and the light intensity values of the pixels in the odd-numbered rows;
a data storage module 643, respectively connected to the image obtaining module 641 and the image processing module 642, configured to establish and store a corresponding relationship curve between the illumination angle and the corresponding second ratio;
the second processing unit 62 matches the corresponding first ratio in each phase contrast image with the corresponding relationship curve to obtain a corresponding irradiation angle as an incident angle.
In a preferred embodiment, as shown in fig. 3, the circles on the correspondence curve represent the second ratio corresponding to each illumination angle, and the predetermined plurality of illumination angles may be illumination at intervals of 5 degrees within a range of [ -90 degrees, 90 degrees ] along the X-axis or Y-axis of the image detector 5. Since no sample is placed above the grating assembly, the collimated light is directly incident to the grating assembly and forms a reference image with specific light intensity variation, as shown in fig. 4, the predetermined plurality of irradiation angles are the incident angles to the grating assembly. After the sample is placed, the simplest way to extract a quantitative refraction angle signal is to establish a linear relationship between the light intensity and the refraction angle of the sample. For this purpose, parallel light is irradiated on the grating assembly at different angles before the sample is placed, so as to obtain a linear relationship between the different irradiation angles and the light intensity variation, after the sample is placed, the parallel light is irradiated on the sample, the sample generates positive or negative refraction angles in the horizontal direction and the vertical direction, and light rays with different refraction angles correspond to different intensities on the image detector, so as to obtain a refraction contrast image of the sample along the horizontal direction and a refraction contrast image along the vertical direction, so as to form a phase contrast image of the sample, as shown in fig. 5. Based on a corresponding relationship curve of the ratio of the incident angle measured without the sample to the light intensity recorded by the pixels in the even rows and the light intensity recorded by the pixels in the odd rows of the image detector and the phase contrast images of different irradiation angles with the sample, the structure of the sample can be three-dimensionally reconstructed, as shown in fig. 6, which is a result schematic of the three-dimensional reconstruction based on the phase contrast images shown in fig. 5 and the corresponding relationship curve shown in fig. 3.
Further, as can be seen from fig. 3, the corresponding relationship curve between the incident angle and the corresponding ratio is not monotonous, and in the actual measurement process, the irradiation angle of the incident light needs to be changed, and an additional phase is introduced, so as to uniquely determine the corresponding relationship between the first ratio and the incident angle. The detailed derivation of the introduced phase can be found in Fourier Ptychographicimaging (p22-27, ISBN:9781681742724) of Zhengyuan' Authority.
As a preferred embodiment, the grating assembly 3 is integrated above the image detector 5.
In a preferred embodiment, the image detector 5 is an area array detector including a plurality of pixels.
As a preferred embodiment, as shown in fig. 7, the grating assembly 3 includes a first grating 31 and a second grating 32, and the first grating 31 and the second grating 32 are perpendicular to each other.
Specifically, in this embodiment, the area array detector has a plurality of pixels arranged perpendicular to each other, and in order to ensure that the image detector 5 can accurately image, the structure of the grating assembly 3 needs to be consistent with the pixel distribution of the image detector 5, and therefore, the first grating 31 and the second grating 32 need to be arranged perpendicular to each other, and the perpendicular relationship is spatially perpendicular to each other, that is, the first grating 31 and the second grating 32 are distributed on two planes parallel to each other, as a preferred embodiment, the range of the pitch between the first grating 31 and the second grating 32 is [400 nm, 600 nm ].
As a preferred embodiment, the first grating 31 and the second grating 32 are made of a metal material, the thickness of the metal material has a value in the range of [100 nm, 300 nm ], and the metal material may be copper.
In a preferred embodiment, the period of the first grating 31 has a value in the range of [400 nm, 600 nm ], and the period of the second grating 32 has a value in the range of [800 nm, 1000 nm ].
In a preferred embodiment, the collimated light is tilted at different angles along the X-axis or Y-axis of the image detector 5 to form the illumination angle, thereby facilitating accurate tissue structure information of the sample.
In a preferred embodiment, the irradiation angle is in the range of [ -90 degrees, 90 degrees ].
An imaging method based on grating phase contrast is applied to the imaging system based on grating phase contrast, as shown in fig. 8, and includes:
step S1, emitting partial coherent light;
step S2, converting the partially coherent light into collimated light;
step S3, the collimated light is irradiated on the sample on the grating component by a plurality of irradiation angles to form refraction light respectively, and the refraction light is processed by the grating component to form light signals with variable intensity;
step S4, receiving the optical signal to form a phase contrast image corresponding to each illumination angle of the sample;
and step S5, performing three-dimensional reconstruction according to each phase contrast image to obtain a three-dimensional image of the sample.
As a preferred embodiment, as shown in fig. 9, step S4 includes:
step S51, extracting the light intensity value of each pixel point in each phase contrast image respectively, and calculating a first ratio between the light intensity value of the pixel point positioned on the even-numbered line and the light intensity value of the pixel point positioned on the odd-numbered line;
step S52, processing according to each first ratio to obtain the incident angle of the corresponding refracted ray;
and step S53, performing three-dimensional reconstruction according to each incident angle to obtain a three-dimensional image of the sample.
As a preferred embodiment, before executing step S52, a preprocessing process is further included, as shown in fig. 10, including:
step A1, when a sample is not placed above the grating component, collimated light is directly irradiated on the grating component by a plurality of preset irradiation angles, and an image detector acquires a reference image corresponding to each irradiation angle;
step A2, extracting the light intensity values of the pixel points in each reference image respectively, and calculating a second ratio between the light intensity values of the pixel points in the even-numbered rows and the light intensity values of the pixel points in the odd-numbered rows;
step A3, establishing a corresponding relation curve between the irradiation angle and the corresponding second ratio and storing the curve;
in step S52, the corresponding irradiation angle is obtained as the incident angle by matching the corresponding first ratio in each phase contrast image with the corresponding correspondence curve.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.
Claims (14)
1. An imaging system based on grating phase contrast, comprising:
a light source device for emitting partially coherent light;
the collimating device is arranged at the light ray exit port of the light source device and is used for converting the partially coherent light into collimated light;
the grating assembly is arranged below the collimating device, a sample is placed above the grating assembly, collimated light is sequentially irradiated on the sample by a plurality of irradiation angles to form refracted light rays respectively, and the refracted light rays are processed by the grating assembly to form optical signals with variable intensity;
an image detector disposed below the grating assembly for receiving the optical signals to form a phase contrast image of the sample at each of the illumination angles;
and the three-dimensional reconstruction system is connected with the image detector and is used for carrying out three-dimensional reconstruction according to each phase contrast image to obtain a three-dimensional image of the sample.
2. The grating phase contrast based imaging system of claim 1, wherein the three-dimensional reconstruction system comprises:
a first processing unit, configured to extract light intensity values of pixels in each phase contrast image, and calculate a first ratio between the light intensity values of the pixels in an even-numbered row and the light intensity values of the pixels in an odd-numbered row;
the second processing unit is connected with the first processing unit and used for obtaining the corresponding incident angle of the refraction light to the grating component according to the first ratio processing;
and the reconstruction unit is connected with the second processing unit and is used for performing three-dimensional reconstruction according to each incident angle to obtain a three-dimensional image of the sample.
3. The grating phase contrast based imaging system of claim 2, wherein the three-dimensional reconstruction system further comprises a pre-processing unit coupled to the second processing unit, the pre-processing unit comprising:
the image acquisition module is used for acquiring a reference image which is acquired by the image detector and corresponds to each illumination angle, wherein the collimated light is directly illuminated on the grating assembly by a plurality of preset illumination angles when the sample is not placed above the grating assembly;
the image processing module is connected with the image acquisition module and used for respectively extracting the light intensity values of all the pixel points in each reference image and calculating a second ratio between the light intensity values of the pixel points positioned in an even row and the light intensity values of the pixel points positioned in an odd row;
the data storage module is respectively connected with the image acquisition module and the image processing module and is used for establishing and storing a corresponding relation curve between the irradiation angle and the corresponding second ratio;
and the second processing unit matches the corresponding first ratio in each phase contrast image in the corresponding relation curve to obtain the corresponding irradiation angle as the incident angle.
4. The grating phase contrast based imaging system of claim 1, wherein the grating assembly is integrated over the image detector.
5. The grating phase contrast based imaging system of claim 1, wherein the image detector is an area array detector comprising a plurality of pixels.
6. The grating phase contrast based imaging system of claim 5, wherein the grating assembly comprises a first grating and a second grating, the first grating and the second grating being orthogonal to each other.
7. The grating phase contrast based imaging system of claim 6, wherein a pitch between the first grating and the second grating ranges from [400 nanometers, 600 nanometers ].
8. The grating phase contrast based imaging system of claim 6, wherein the first grating and the second grating are made of a metallic material having a thickness in a range of [100 nanometers, 300 nanometers ].
9. The grating phase contrast based imaging system of claim 6, wherein the period of the first grating ranges from [400 nm, 600 nm ], and the period of the second grating ranges from [800 nm, 1000 nm ].
10. The grating phase contrast based imaging system of claim 1 or 3, wherein the collimated light is tilted at different angles along an X-axis or a Y-axis of the image detector to form the illumination angle.
11. The grating phase contrast based imaging system of claim 10, wherein the illumination angle is in a range of [ -90 degrees, 90 degrees ].
12. An imaging method based on grating phase contrast, which is applied to the imaging system based on grating phase contrast according to any one of claims 1 to 11, and comprises the following steps:
step S1, emitting partial coherent light;
step S2, converting the partially coherent light into collimated light;
step S3, the collimated light is irradiated on the sample placed on the grating component by a plurality of irradiation angles to respectively form refracted light rays, and the refracted light rays are processed by the grating component to form light signals with variable intensity;
step S4, receiving the optical signals to form a phase contrast image of the sample corresponding to each illumination angle;
and step S5, performing three-dimensional reconstruction according to each phase contrast image to obtain a three-dimensional image of the sample.
13. The grating phase contrast based imaging method according to claim 12, wherein the step S5 comprises:
step S51, extracting the light intensity value of each pixel point in each phase contrast image respectively, and calculating a first ratio between the light intensity value of the pixel point positioned on the even-numbered line and the light intensity value of the pixel point positioned on the odd-numbered line;
step S52, according to each first ratio, the corresponding incident angle of the refraction light to the grating component is obtained through processing;
and step S53, performing three-dimensional reconstruction according to each incident angle to obtain a three-dimensional image of the sample.
14. The grating phase contrast based imaging method of claim 13, further comprising a preprocessing process before performing the step S52, comprising:
step A1, when the sample is not placed above the grating assembly, the collimated light is directly irradiated on the grating assembly by a plurality of preset irradiation angles, and the reference image corresponding to each irradiation angle is acquired by the image detector;
step A2, extracting the light intensity value of each pixel point in each reference image respectively, and calculating a second ratio between the light intensity value of the pixel point positioned on the even-numbered line and the light intensity value of the pixel point positioned on the odd-numbered line;
step A3, establishing a corresponding relation curve between the irradiation angle and the corresponding second ratio and storing the corresponding relation curve;
in the step S52, the corresponding irradiation angle is obtained as the incident angle by matching the corresponding first ratio in each phase contrast image with the corresponding relationship curve.
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