Edge enhancement imaging system and preparation method

Abstract

The invention relates to an edge enhancement imaging system. The system comprises a point light source; the object side polarization filtering unit is arranged on the light emitting side of the point light source and modulates the light into specific polarized light to irradiate a sample; the imaging unit is arranged on the light emitting side of the object side polarization filtering unit and is used for transmitting the input light field to an imaging surface; the spatial variable polarization modulation element is arranged on a conjugate surface of the point light source relative to the imaging unit and is used for performing spatial variable polarization modulation to obtain a modulated light field; and the image space polarization filtering unit is arranged between the space variable polarization modulation element and the imaging surface and is used for screening the modulated light field to obtain a light field in a specific polarization direction, and the light field in the specific polarization direction forms an edge enhanced imaging light field on the imaging surface. The invention also relates to a preparation method of the edge enhancement imaging system. The device has the advantages that the imaging effect of edge enhancement in any direction or all directions is achieved, a common microscope imaging system can be compatible, phase modulation is achieved through polarization state transformation, and sensitivity to wavelength is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical imaging technology, in particular to an edge-enhanced imaging system and a preparation method. BACKGROUND

[0002] The characteristic information of an object is mostly concentrated at the edge, and the determination of the edge position and the information extraction have important applications in the fields of image recognition, intelligent driving, optical information processing, etc. The edge of an object corresponds to a region with a large amplitude or phase gradient in the mathematical expression of its light field. Usually, spatial filtering technology is used to achieve edge processing by filtering out low-order Fourier components and enhancing high-order Fourier components in an optical 4f system. However, such intensity-type filtering systems often affect the overall imaging intensity, resulting in insufficient efficiency.

[0003] At present, spiral phase contrast imaging is a boundary detection method that can achieve arbitrary direction boundary enhancement without changing the overall light intensity. It is based on a traditional 4f system, and a spiral phase filter is placed on the confocal Fourier plane to obtain edge enhancement effect on the imaging plane. However, this method has obvious defects: the 4f system has a complex optical path, requires multiple lenses to cooperate with filtering, and has strict requirements on the light source, which is not compatible with common microscope imaging systems. At the same time, the traditional spiral phase plate relies on the thickness difference of the filter changing with the angle to introduce the spiral phase, which is highly sensitive to wavelength and only effective for specific wavelengths. SUMMARY

[0004] The technical problem to be solved by the embodiments of the present application is to provide an edge-enhanced imaging system and a preparation method, which do not rely on a traditional 4f system, place a spatial variable polarization modulation element on the conjugate plane of a point light source relative to an imaging unit, and place a polarization filter element in front of the imaging plane to achieve an imaging effect of arbitrary direction or full direction edge enhancement, which is compatible with common microscope imaging systems, the phase modulation is realized by polarization state transformation, and the sensitivity to wavelength is reduced.

[0005] To solve the above technical problems, the present application provides an edge-enhanced imaging system, comprising, a point light source for emitting light rays; an object-side polarization filter unit arranged on the light emitting side of the point light source for modulating the light rays into specific polarized light to irradiate on a sample to form an input light field; an imaging unit arranged on the light emitting side of the object-side polarization filter unit for propagating the input light field to an imaging plane; a spatial variable polarization modulation element arranged on the conjugate plane of the point light source relative to the imaging unit for spatial variable polarization modulation of the input light field to obtain a modulated light field; An image-side polarization filter unit is arranged between the spatially-varying polarization modulation element and the imaging surface, for screening the modulated light field to obtain a specific polarization direction light field, which forms an edge-enhanced imaging light field at the imaging surface.

[0006] In one possible implementation, the imaging unit comprises a lens or an objective or an optical imaging device based on the principle of conjugate imaging.

[0007] In one possible implementation, the object-side polarization filter unit comprises a linear polarizer for modulating the light rays into linearly polarized light, or a wave plate for modulating the light rays into circularly polarized light.

[0008] In one possible implementation, the image-side polarization filter unit comprises the linear polarizer for screening the specific polarization direction light field to perform full-direction or specific-direction edge enhancement.

[0009] In one possible implementation, when the object-side polarization filter unit is the linear polarizer, the image-side polarization filter unit performs specific-direction edge enhancement; and when the object-side polarization filter unit is the wave plate, the image-side polarization filter unit performs full-direction edge enhancement.

[0010] In one possible implementation, the spatially-varying polarization modulation element is a polarization spiral wave plate, the intrinsic polarization state of which varies linearly with the angle, and the Jones matrix of the polarization spiral wave plate varying with the space is , ; wherein, represents the distance of a point on the polarization spiral wave plate to the central axis; represents the circumferential position of the point on the polarization spiral wave plate with the central axis as the reference.

[0011] In one possible implementation, the conjugate condition between the plane where the point light source is located and the plane where the spatially-varying polarization modulation element is located is represented by the following expression, ; wherein, represents the distance of the point light source to the image-side principal plane in the imaging unit; represents the distance of the image-side principal plane in the imaging unit to the spatially-varying polarization modulation element; represents the focal length of the imaging unit.

[0012] In one possible implementation, the conjugate condition of the imaging surface and the object plane where the sample is located is expressed by the following expression, ； wherein, represents the distance from the object plane to the image-side principal plane in the imaging unit; represents the distance from the image-side principal plane in the imaging unit to the imaging surface; represents the focal length of the imaging unit.

[0013] In one possible implementation, the expression of the edge-enhanced imaging light field is, wherein, represents the edge-enhanced imaging light field; represents the radial coordinate of the imaging surface, corresponding to the radius of the spatial position; represents the azimuth angle of the imaging surface, corresponding to the circumferential angle of the spatial position; represents the distance from the image-side principal plane in the imaging unit to the imaging surface; represents the distance from the image-side principal plane in the imaging unit to the spatially-varying polarization modulation element; represents the secondary phase that does not affect the imaging result; represents the input light field; represents the polarization point spread function; represents the angle between the polarization direction of the input light and the x-axis; represents the Jones matrix of the spatially-varying polarization spiral wave plate; represents the Jones vector of the input light.

[0014] In one possible implementation, further comprising a light intensity capturing unit for capturing the edge-enhanced imaging light field filtered by the spatially-varying polarization modulation element, wherein the light intensity capturing unit comprises a charge-coupled device sensor or a complementary metal-oxide-semiconductor sensor.

[0015] Correspondingly, the present application further provides a preparation method of an edge-enhanced imaging system, comprising, providing a point light source for emitting light rays; ​A material side polarization filter unit is provided on the light emitting side of the point light source to modulate the light into a specific polarized light to irradiate on the sample to form an input light field; An imaging unit is provided on the light emitting side of the material side polarization filter unit to propagate the input light field to an imaging plane; A spatial variable polarization modulation element is provided on the conjugate plane of the point light source relative to the imaging unit to spatially modulate the input light field to obtain a modulated light field; An image side polarization filter unit is provided between the spatial variable polarization modulation element and the imaging plane to filter the modulated light field to obtain a specific polarization direction light field, which forms an edge enhanced imaging light field on the imaging plane.

[0016] The present application has the following beneficial effects: The spatial variable polarization modulation element is placed on the conjugate plane of the point light source relative to the imaging unit, and the polarization filter element is placed in front of the imaging plane, which can realize arbitrary direction or omnidirectional edge enhanced imaging effect without relying on the traditional 4f system, and is compatible with common microscope imaging systems. The phase modulation is realized by polarization state transformation, which reduces the sensitivity to wavelength.

[0017] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a schematic diagram of the edge enhanced imaging system of the present application; Figure 2 is a schematic diagram of the spatial variable polarization modulation element of the present application; Figure 3 is a schematic diagram of the input object of the present application; Figure 4 is a point spread function schematic diagram of the present application when the material side input circular polarization and the image side no polarization filtering system; Figure 5 is an imaging result schematic diagram of the present application when the material side input circular polarization and the image side no polarization filtering system; Figure 6 is a point spread function schematic diagram of the present application when the material side input is x direction linear polarization and the image side no polarization filtering system; Figure 7 is an imaging result schematic diagram of the present application when the material side input is x direction linear polarization and the image side no polarization filtering system; Figure 8 is a step diagram of the preparation method of the edge enhanced imaging system of the present application. DETAILED DESCRIPTION

[0019] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0020] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly attached to the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] The present invention provides an edge enhancement imaging system, referring to Figure 1 ,include, Point light source 110, for emitting light; The object-side polarization filter unit 120 is provided on the light-emitting side of the point light source 110 and modulates the light into a specific polarization light and irradiates the light onto the sample to form an input light field; The imaging unit 130 is provided on the light-emitting side of the object-side polarization filter unit 120 and is used to transmit the input light field to the imaging surface 160; The spatially variable polarization modulation element 140 is provided on a conjugate plane of the point light source 110 relative to the imaging unit 130 and is used to perform spatially variable polarization modulation on the input light field to obtain a modulated light field; The image-side polarization filter unit 150 is disposed between the spatially variable polarization modulation element 140 and the imaging plane 160 , and is used to filter the modulated light field to obtain a light field with a specific polarization direction. The light field with the specific polarization direction forms an edge-enhanced imaging light field on the imaging plane 160 .

[0023] Specifically, the present application provides an edge enhancement imaging system, which can be directly integrated into a microscope system without changing the microscope structure, and realizes edge enhancement imaging in a specific direction by applying a spatially-varying polarization modulation element 140 in the optical path. By using a superstructure wave plate whose polarization eigenstate varies linearly with angle, and placing it on the conjugate plane of the point light source 110 with respect to the transmissive imaging unit 130, when the object and the object plane main plane, and the imaging distance and the image plane main plane satisfy the Gaussian imaging relationship, the edge enhancement imaging effect can be obtained in the final imaging without affecting the light intensity.

[0024] In a feasible implementation, the imaging unit 130 includes a lens or an objective lens or an optical imaging device based on the principle of conjugate imaging.

[0025] Specifically, the imaging unit 130 includes a single lens or an objective lens or any optical imaging device based on the principle of conjugate imaging. The optical imaging device based on the principle of conjugate imaging (such as a telecentric lens or an imaging lens group) can be adapted to different types of optical systems, thereby widening the application scenarios of the edge enhancement technology.

[0026] In a feasible implementation, the object-side polarization filter unit 120 includes a linear polarizer that modulates light into linearly polarized light, or a wave plate that modulates light into circularly polarized light; The image-side polarization filter unit 150 includes a linear polarizer for screening light fields in a specific polarization direction to perform edge enhancement in all directions or in a specific direction; When the object-side polarization filter unit 120 is a linear polarizer, the image-side polarization filter unit 150 performs specific direction edge enhancement; When the object-side polarization filter unit 120 is a wave plate, the image-side polarization filter unit 150 performs all-direction edge enhancement.

[0027] Specifically, when the input is circular polarization, the light intensity is concentrated on the edge of the object; when the input is linear polarization, only the edge in a specific direction is enhanced.

[0028] In a feasible implementation, the spatially-varying polarization modulation element 140 is a polarization spiral wave plate, whose eigenpolarization state varies linearly with angle, as shown in Figure 2 , and the Jones matrix of the polarization spiral wave plate varies with space is , ; wherein, represents the distance from a certain point on the polarization spiral wave plate to the central axis; represents the circumferential position of a certain point on the polarization spiral wave plate with the central axis as the reference.

[0029] In one possible implementation, the conjugate condition between the plane where the point light source 110 is located and the plane where the spatially varying polarization modulation element 140 is located is represented by the following expression, ; wherein, represents the distance from the point light source 110 to the image-side principal plane in the imaging unit 130; represents the distance from the image-side principal plane in the imaging unit 130 to the spatially varying polarization modulation element 140; represents the focal length of the imaging unit 130.

[0030] In one possible implementation, the conjugate condition between the imaging plane 160 and the object plane 170 where the sample is located is represented by the following expression, ； wherein, represents the distance from the object plane 170 to the image-side principal plane in the imaging unit 130; represents the distance from the image-side principal plane in the imaging unit 130 to the imaging plane 160; represents the focal length of the imaging unit 130.

[0031] In one possible implementation, when the above conjugate condition relationship is satisfied, the expression of the final output edge-enhanced imaging light field is, ; wherein, represents the edge-enhanced imaging light field; represents the radial coordinate of the imaging plane 160, corresponding to the radius of the spatial position; represents the azimuth angle of the imaging plane 160, corresponding to the circumferential angle of the spatial position; represents the distance from the image-side principal plane in the imaging unit 130 to the imaging plane 160; represents the distance from the image-side principal plane in the imaging unit 130 to the spatially varying polarization modulation element 140; represents the secondary phase that does not affect the imaging result; represents the input light field; represents the polarization point spread function; represents the angle between the input light polarization direction and the x-axis. a Jones matrix representing the spatial variation of the polarization spiral wave plate; a Jones vector representing the input light.

[0032] In one possible implementation, further comprising a light intensity capturing unit for capturing the edge-enhanced imaging light field filtered by the spatially variable polarization modulation element 140, the light intensity capturing unit comprising a charge-coupled device sensor (CCD) or a complementary metal-oxide-semiconductor sensor (CMOS).

[0033] Specifically, the charge-coupled device has a capture efficiency of light photons of over 90%, and can capture a weaker edge-enhanced light field in a weak light environment (such as fluorescence imaging, biological sample observation), avoiding loss of edge information due to insufficient light intensity. For example, in an embodiment, the light intensity is not lost when circularly polarized input, but the sample reflected light can be weak, and the high sensitivity of the CCD can ensure that the edge light intensity distribution is clearly recorded.

[0034] The noise level of the CCD is generally lower than that of the CMOS, and is suitable for scenes with high signal-to-noise ratio requirements (such as medical microscopic diagnosis), and can reduce the interference of noise on edge position positioning, ensuring the accuracy of the edge enhancement effect.

[0035] The complementary metal-oxide-semiconductor can simultaneously process strong and weak light regions, avoiding distortion of the contrast between the high-brightness edge and the dark background in the edge-enhanced light field. For example, when the sample edge light intensity difference is large, the CMOS can effectively preserve the edge details of each region. The power consumption of the CMOS sensor is much lower than that of the CCD, and is suitable for portable devices (such as on-site detection microscopes), and can integrate signal processing circuits, simplify system design, and reduce hardware costs.

[0036] In one embodiment, the point light source 110 is placed at infinity for the experiment, the point light source 110 emits a 532 nm spherical wave to illuminate the sample, and the sample is an English letter N, as shown in FIG. 1B. Since the point light source 110 is located at infinity, according to the above Jones matrix, Figure 3 , is equal to f, and the polarization spiral wave plate is placed at this plane. The distance between the sample and the imaging system object plane is , , and the imaging system focal length is . Therefore, according to the conjugate condition formula, the imaging surface distance from the imaging system image plane is , , so its magnification is about 1.11 times.

[0037] First, calculate the case where the object spiral polarization filtering system is circularly polarized input, and L is According to the expression of the final output imaging plane light field, the point spread function expression is: ; Wherein, is a first-order Bessel function, it can be seen that in addition to the front polarization Jones vector, the point spread function expression is the same as the ordinary spiral phase contrast imaging point spread function, and both have a spiral phase function, so the final imaging effect is the same as the ordinary spiral phase plate based spiral phase contrast imaging. The final result is shown in Figure 4 、 Figure 5 , it can be seen that the light intensity is mainly concentrated on the edge of the object, and the boundary in any direction is highlighted.

[0038] When the object side polarization filtering system is direction linear polarizer, that is, the input light Jones vector expression, is 0.

[0039] ; And in the object side polarization system, the direction linear polarizer is applied, so according to the above formula, the intensity of the point spread function at this time will be different from the previous symmetrical form, showing asymmetric distribution, after convolution with the input light field, the enhancement of the boundary in a specific direction can be realized. The final imaging result is shown in Figure 6 、 Figure 7 , it can be seen that it is consistent with the theory, only the direction boundary is enhanced, and the boundary of the other direction is not highlighted.

[0040] Correspondingly, the application also provides a preparation method of an edge enhancement imaging system, referring to Figure 8 , comprising, Step S100, providing a point light source 110 for emitting light; Step S200, providing an object side polarization filtering unit 120, which is arranged on the light emitting side of the point light source 110, and modulates the light to a specific polarized light to irradiate on the sample to form an input light field; Step S300, providing an imaging unit 130, which is arranged on the light emitting side of the object side polarization filtering unit 120, and is used for propagating the input light field to an imaging plane 160; Step S400, providing a spatial variable polarization modulation element 140, which is arranged on the conjugate plane of the point light source 110 relative to the imaging unit 130, and is used for spatial variable polarization modulation of the input light field to obtain a modulated light field; At step S500, a like-side polarization filter unit 150 is provided between the spatially-varying polarization modulation element 140 and the imaging plane 160, and is configured to filter the modulated light field to obtain a light field with a specific polarization direction. The light field with the specific polarization direction forms an edge-enhanced imaging light field at the imaging plane 160.

[0041] Any combination of the above-described technical features of the embodiments can be made. In order to make the description simple, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not contradict each other, they should be considered as falling within the scope of the present disclosure.

[0042] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all fall within the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. An edge-enhanced imaging system, characterized in that: include, Point light source, used to emit light; An object-side polarization filter unit is provided on the light-emitting side of the point light source, modulating the light into a specific polarized light and irradiating the light onto the sample to form an input light field; An imaging unit, provided on the light-emitting side of the object-side polarization filter unit, for transmitting the input light field to an imaging surface; a spatially variable polarization modulation element, provided on a conjugate plane of the point light source relative to the imaging unit, for performing spatially variable polarization modulation on the input light field to obtain a modulated light field; The image-side polarization filter unit is arranged between the spatially variable polarization modulation element and the imaging plane, and is used to filter the modulated light field to obtain a light field with a specific polarization direction, and the light field with a specific polarization direction forms an edge-enhanced imaging light field on the imaging plane.

2. The edge-enhanced imaging system according to claim 1, wherein: The imaging unit includes a lens, an objective lens, or an optical imaging device based on the conjugate imaging principle.

3. The edge-enhanced imaging system according to claim 1, wherein: The object-side polarization filter unit includes a linear polarizer that modulates the light into linearly polarized light. Or a wave plate that modulates the light into circularly polarized light.

4. The edge-enhanced imaging system according to claim 3, wherein: The image-side polarization filter unit includes the linear polarizer, which is used to filter the light field in the specific polarization direction to perform edge enhancement in all directions or in a specific direction.

5. The edge-enhanced imaging system according to claim 3, wherein: When the object-side polarization filter unit is the linear polarizer, the image-side polarization filter unit performs edge enhancement in a specific direction; When the object-side polarization filter unit is the wave plate, the image-side polarization filter unit performs omnidirectional edge enhancement.

6. The edge-enhanced imaging system according to claim 1, wherein: The spatially variable polarization modulation element is a polarization spiral wave plate, the intrinsic polarization state of the polarization spiral wave plate changes linearly with the angle, and the Jones matrix of the polarization spiral wave plate that changes with space is: , ； in, represents the distance from a certain point on the polarization spiral wave plate to the central axis; It represents the circumferential position of a certain point on the polarization spiral wave plate with the central axis as the reference.

7. The edge-enhanced imaging system according to claim 1, wherein: The conjugate condition of the plane where the point light source is located and the plane where the spatially variable polarization modulation element is located is expressed by the following expression: ； in, represents the distance from the point light source to the principal plane of the image side in the imaging unit; represents the distance from the image-side principal plane in the imaging unit to the spatially variable polarization modulation element; represents the focal length of the imaging unit.

8. The edge-enhanced imaging system according to claim 1, wherein: The conjugate condition between the imaging plane and the object plane where the sample is located is expressed by the following expression: ； in, represents the distance from the object plane to the principal plane of the image side in the imaging unit; represents the distance from the image side principal plane in the imaging unit to the imaging surface; represents the focal length of the imaging unit.

9. The edge-enhanced imaging system according to claim 1, wherein: The expression of the edge-enhanced imaging light field is: ； in, represents the edge-enhanced imaging light field; Represents the radial coordinate of the imaging surface, corresponding to the radius of the spatial position; represents the azimuth angle of the imaging surface, corresponding to the circumferential angle of the spatial position; represents the distance from the image side principal plane in the imaging unit to the imaging surface; represents the distance from the image-side principal plane in the imaging unit to the spatially variable polarization modulation element; Indicates the secondary phase that does not affect the imaging results; represents the input light field; represents the polarization point spread function; represents the angle between the polarization direction of the input light and the x-axis; A Jones matrix representing the spatial variation of the polarization spiral wave plate; represents the Jones vector of the input light.

10. The edge-enhanced imaging system according to claim 1, wherein: It also includes a light intensity capture unit for capturing the edge-enhanced imaging light field filtered by the spatially variable polarization modulation element, and the light intensity capture unit includes a charge coupled device sensor or a complementary metal oxide semiconductor sensor.

11. A method for preparing an edge-enhanced imaging system, characterized in that: include, Provide a point light source for emitting light; Providing an object-side polarization filter unit, which is arranged on the light-emitting side of the point light source, modulating the light into a specific polarized light and irradiating it onto the sample to form an input light field; Providing an imaging unit, which is arranged on the light-emitting side of the object-side polarization filter unit and is used to propagate the input light field to an imaging surface; Providing a spatially variable polarization modulation element, which is arranged on a conjugate plane of the point light source relative to the imaging unit, for performing spatially variable polarization modulation on the input light field to obtain a modulated light field; An image-side polarization filter unit is provided, which is arranged between the spatially variable polarization modulation element and the imaging plane, and is used to filter the modulated light field to obtain a light field with a specific polarization direction, and the light field with a specific polarization direction forms an edge-enhanced imaging light field on the imaging plane.

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