A planar device-based dark-field speckle illumination super-resolution imaging system

Abstract

The application discloses a kind of dark-field speckle illumination super-resolution imaging systems based on planar device, belong to super-resolution dark-field imaging field, the system utilizes 633nm laser light source to emit wavelength 633nm strong coherence light beam, by multimode fiber bundle incidence into planar device, the laser emission incidence into titanium dioxide scattering layer and carries out scattering, incidence into one-dimensional photonic crystal, the one-dimensional photonic crystal filters the speckle with numerical aperture greater than 0.6, passes through the one-dimensional photonic crystal and illuminates sample;The illuminated sample emits scattered light to reach image plane detector and forms the dark-field speckle pattern of sample;By vibrator vibration multimode fiber bundle changes the phase of incident strong coherence light beam, restores different dark-field speckle pattern to obtain high-resolution dark-field image.The application imaging resolution is high, compact structure is easy to integrate, simple operation, without strict alignment process, realizes high contrast super-resolution dark-field imaging and surface wave imaging.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of super-resolution dark-field imaging, and particularly relates to a dark-field speckle illumination super-resolution imaging system based on a planar device. BACKGROUND

[0002] Microscopic imaging technology is the most direct means for people to understand the microcosmic world, and optical microscopic imaging technology directly presents the image of the microcosmic world to our eyes, and is the most intuitive and most commonly used microscopic technology among all the microscopic imaging technologies. Dark-field microscopic imaging technology is a high-contrast, wide-field and label-free imaging technology. It makes the imaging objective lens only collect the scattered light of a sample by obliquely illuminating the sample with illumination light at a large angle, so that the illuminated sample is bright and the background is dark in the presented image. Since the illumination light is not collected by the imaging objective lens, the imaging contrast is much higher than that of a bright-field optical microscope. However, the dark-field imaging microscopic technology has great limitations in practical applications. For example, a traditional dark-field microscope needs to use a special condenser to achieve the oblique incidence of illumination light on the sample, and the condenser has a large volume, which increases the volume of the imaging system. Since the condenser requires high collimation of the incident light beam to achieve the expected uniform illumination effect, the operation complexity of the system is increased. The imaging resolution of the traditional dark-field illumination is limited by the diffraction limit of the imaging system, and super-resolution imaging cannot be achieved, which limits its application. Since the condenser is used to focus the illumination light on the sample, the illumination field of view is small. SUMMARY

[0003] To solve the above technical problems, the application provides a dark-field speckle illumination super-resolution imaging system based on a planar device. After a coherent light beam passes through a titanium dioxide scattering layer, the scattered light interferes with each other to form a speckle pattern. A one-dimensional photonic crystal in the planar device performs angle selection on the propagation wave of the speckle, so as to achieve dark-field speckle illumination at a large angle. The scattered light of the illuminated sample is collected by an imaging system to form a speckle pattern image of the sample. Different speckle patterns are changed by vibration of a vibrator, and the imaging system records different sample speckle patterns. A high-resolution dark-field image is calculated from different speckle patterns by a conjugate gradient algorithm.

[0004] To achieve the above object, the technical scheme adopted by the application is as follows:

[0005] A dark-field speckle illumination super-resolution imaging system based on a planar device, the system comprising: an image plane detector, an imaging tube lens, an imaging objective lens, a planar device, a 633nm laser light source and a vibrator, wherein the planar device comprises a one-dimensional photonic crystal, a titanium dioxide scattering layer and a multi-mode optical fiber bundle stacked in order from top to bottom, and a 300nm-thick gold film.

[0006] The 633nm laser light source emits a strong coherent light beam with a wavelength of 633nm, the strong coherent light beam is incident into a planar device through a multimode fiber bundle, the outgoing laser is incident into a titanium dioxide scattering layer for scattering, the scattered strong coherent light beams interfere with each other to form speckles, the speckles are incident into a one-dimensional photonic crystal, the one-dimensional photonic crystal screens the speckles with a numerical aperture greater than 0.6, the speckles pass through the one-dimensional photonic crystal and illuminate a sample on the one-dimensional photonic crystal, and the scattered light emitted by the illuminated sample is collected by an imaging objective and passes through an imaging tube lens to reach an image plane detector to form a dark field speckle pattern of the sample.

[0007] The phase of the incident strong coherent light beam is changed by vibrating the multimode fiber bundle through a vibrator to obtain multiple different dark field speckle patterns, and the multiple different dark field speckle patterns are recovered by using a conjugate gradient algorithm to obtain a high-resolution dark field image beyond the diffraction limit.

[0008] Further, the 300nm-thick gold film is used to reflect the scattered strong coherent light beam back into the titanium dioxide scattering layer.

[0009] Further, the one-dimensional photonic crystal is composed of SiO2 and Si3N4 nanofilms alternately stacked.

[0010] Further, the numerical aperture of the imaging objective is 0.6, and the magnification is 40 times.

[0011] Further, the titanium dioxide scattering layer is prepared by spin coating titanium dioxide particles with a size of 60nm on a clean cover glass, and the titanium dioxide particles form a film with a thickness of about 2um.

[0012] Further, one end of the multimode fiber bundle is adhered to the surface of the 300nm-thick gold film using an alpha-cyanoacrylic acid ethyl ester.

[0013] The present application has the following advantages:

[0014] 1. High spatial resolution imaging: After the coherent light beam of the present application passes through the titanium dioxide scattering layer, the light beam is scattered at various angles and interferes with each other to form speckles, the one-dimensional photonic crystal regulates the exit angle of the speckles, and dark field speckle illumination can be formed, and high-resolution dark field imaging beyond the diffraction limit can be obtained by recovering through the conjugate gradient algorithm.

[0015] 2. Wide field imaging: The illumination area of the present application is determined by the size of the planar illumination device and the arrangement of the multimode fiber bundle, in theory, the illumination area can be the entire planar illumination device, and wide field imaging can be realized by cooperating with different imaging objectives.

[0016] 3. Simple device: the microscope system of the present application is composed of a normal upright microscope and a planar illuminator and a light source, and the coherent light is directly coupled into the planar illuminator through a multi-mode optical fiber bundle, which is convenient for non-professional operation.

[0017] 4. High integration: the coherent light beam of the present application is transmitted by a multi-mode optical fiber waveguide, and the light beam is not transmitted in free space, and the planar device is a micron-level device, which greatly reduces the volume of the system and realizes integration.

[0018] 5. Multi-functional illumination: due to the band structure of the all-dielectric one-dimensional photonic crystal, the incident 532nm strong coherent light source can realize total internal reflection illumination and realize high-resolution surface imaging. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Fig. 1 is a structural schematic diagram of a dark-field speckle illumination super-resolution imaging system based on a planar device according to the present application;

[0020] Figure 2 Fig. 2 is a schematic diagram of the illumination principle of the planar device according to the present application;

[0021] Figure 3 Fig. 3 is a schematic diagram of the application results of the dark-field speckle illumination super-resolution imaging system based on the planar device according to the present application, wherein a is the average addition result of 200 sample speckle patterns obtained by using the imaging system; b is the result of the dark-field imaging recovered by using a conjugate gradient algorithm; and c is the actual image of the sample observed under an electron microscope.

[0022] REFERENCE NUMERALS:

[0023] 1. Image plane detector; 2. Imaging tube lens; 3. Imaging objective lens; 4. Planar device; 5. 633nm laser light source; 6. Vibrator; 7. One-dimensional photonic crystal; 8. Titanium dioxide scattering layer; 9. Multi-mode optical fiber bundle; 10. 300nm thick gold film. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0025] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0026] As Figure 1As shown in the figure, the plane device-based dark-field speckle illumination super-resolution imaging system of the present application comprises an image plane detector 1, an imaging tube lens 2, an imaging objective lens 3, a plane device 4, a 633nm laser light source 5, and a vibrator 6. Figure 2 As shown in the figure, the plane device 4 comprises a one-dimensional photonic crystal 7 for regulating the exit angle of the speckle, a titanium dioxide scattering layer 8 for scattering the incident light into various angles, a multimode fiber bundle 9 for transmitting the coherent light beam, and a 300nm-thick gold film 10 for improving the light utilization rate. The one end of the multimode fiber bundle 9 is adhered to the upper surface of the 300nm-thick gold film 10 using ethyl α-cyanoacrylate.

[0027] The principle of the technical scheme of the present application is as follows: the strong coherent light beam is transmitted into the plane device 4 through the multimode fiber bundle 9 to form a high-integration illuminator. The titanium dioxide scattering layer 8 in the plane device 4 scatters the incident light into various angles of light, and the scattered lights interfere with each other to form a speckle. The one-dimensional photonic crystal 7 above the plane device 4 is designed to regulate the exit angle of the speckle to form a large-angle dark-field speckle illumination. Only the scattered light information of the illuminated sample is collected by the imaging system to form a dark-field speckle pattern of the sample. The multimode fiber bundle 9 is vibrated by the vibrator 6 to change the phase of the incident light, so that the illumination speckle pattern changes. The imaging system records the speckle patterns of the sample under different dark-field speckle illuminations. The conjugate gradient algorithm is used to restore the images to obtain a dark-field image with high contrast and high resolution.

[0028] Specifically, the 633nm laser light source 5 emits a strong coherent light beam with a wavelength of 633nm. The light beam is transmitted into the plane device 4 through the multimode fiber bundle 9. After being emitted from the multimode fiber bundle 9, the incident light beam is incident on the titanium dioxide scattering layer 8 and scattered into various angles. The scattered lights interfere with each other to form a speckle, which is incident on the one-dimensional photonic crystal 7. The one-dimensional photonic crystal 7 selects the incident speckle angle, and only the light with a numerical aperture greater than 0.6 can pass through the one-dimensional photonic crystal 7. Therefore, a large-angle dark-field speckle can be formed after passing through the one-dimensional photonic crystal 7, and the sample on the one-dimensional photonic crystal 7 is illuminated. The illuminated sample emits scattered light, which is collected by the imaging objective lens 3 with a numerical aperture of 0.6 and sequentially passes through the imaging tube lens 2 to reach the image plane detector 1 to form a dark-field speckle pattern of the sample. The phase of the incident light can be changed by vibrating the multimode fiber bundle 9 through the vibrator 6 to obtain different speckle illumination patterns. The image plane detector 1 sequentially records the corresponding different dark-field speckle patterns of the sample, a total of 200. The 200 dark-field speckle patterns of the sample are restored using the conjugate gradient algorithm to obtain a dark-field image with a resolution exceeding the diffraction limit.

[0029] The 633 nm laser light source 5 is a strong coherent light source. After the incident light is scattered by the titanium dioxide scattering layer 8, the scattered light interferes with each other to form a speckle pattern. After the speckle pattern is incident on the one-dimensional photonic crystal 7, only the light with a numerical aperture greater than 0.6 can pass through the one-dimensional photonic crystal 7 because the one-dimensional photonic crystal 7 can screen the transmittance of the incident light. The light with a numerical aperture less than 0.6 is reflected by the one-dimensional photonic crystal 7 back to the titanium dioxide scattering layer 8 to be scattered again to the one-dimensional photonic crystal 7. The scattered light with a numerical aperture greater than 0.6 interferes with each other on the surface of the one-dimensional photonic crystal 7 to form a dark-field speckle illumination with a large angle. The imaging objective 3 collects the scattered light of the object but not the illumination light, thereby forming a dark-field image. In this embodiment, the numerical aperture of the imaging objective 3 is 0.6 and the magnification is 40 times. The pure scattered light of the sample is collected by the imaging objective 3, reaches the imaging tube lens 2, and is finally recorded on the image plane detector 1.

[0030] The vibrator 6 is a mechanical vibration that can disturb the multimode fiber bundle 9 to change the phase of the transmitted coherent light beam, thereby changing the speckle pattern emitted on the one-dimensional photonic crystal 7. Different speckle patterns are recorded by the image plane detector 1 in turn. The total number of recorded images is 200. The 200 images can be used to recover a high-resolution dark-field image beyond the diffraction limit by using a conjugate gradient algorithm.

[0031] The one-dimensional photonic crystal 7 controls the light flow. By processing the high-low refractive alternating multilayer nanofilm, the transmission and reflection of different wave vectors are controlled to let the light beam with a wave vector greater than a certain value pass through. By changing the refractive index and thickness of each layer, a planar device substrate supporting different wavelengths and different emission angles can be set. The multiple one-dimensional photonic crystals 7 are composed of SiO2 and Si3N4 nanofilms, a total of 15 pairs. The one-dimensional photonic crystal 7 is composed of alternating layers of Si3N4 and SiO2 dielectric, which controls the light beam with a numerical aperture greater than 0.6 to pass through.

[0032] The titanium dioxide scattering layer 8 is prepared by spin coating titanium dioxide particles with a size of 60 nm on a clean cover glass. The titanium dioxide particles form a film about 2 μm thick, so that the incident coherent light is scattered by the titanium dioxide scattering layer 8 to form a speckle pattern incident on the one-dimensional photonic crystal 7.

[0033] The imaging tube lens 2, the air objective 3, the image plane detector 1, and the planar device 4 form a dark-field speckle illumination super-resolution imaging system with a large field of view, and the above-mentioned devices are coaxially arranged.

[0034] As Figure 3As shown, it is the effect of imaging a polystyrene small ball with a diameter of 200 nm by using the planar device-based dark-field speckle illumination super-resolution imaging system of the present application. Wherein, a is the result of average addition of 200 sample speckle maps obtained by using the system, that is, the effect of traditional dark-field imaging, the image has the advantage of high contrast but the disadvantage of low resolution; b is the result of dark-field imaging after the conjugate gradient algorithm is recovered, it can be seen that the spatial positions of two adjacent particles can be clearly distinguished, so the image has the advantage of high resolution; c is the real image of the sample observed under the electron microscope. It can be seen that the distance between two particles is 340 nm. Theoretically, the objective with a numerical aperture of 0.6 can only distinguish 527 nm, so the imaging resolution of the system is improved by 1.5 times.

[0035] In summary, the purpose of the present application is to overcome the shortcomings of low imaging resolution, single illumination function, large volume and high cost of traditional dark-field imaging microscopes, and a planar device-based dark-field speckle illumination super-resolution imaging system is proposed. The system has high imaging resolution, compact structure, simple operation, and does not need strict alignment process, and realizes high-contrast super-resolution dark-field imaging and surface wave imaging.

[0036] The above specific embodiments further illustrate the purpose, technical solutions and advantages of the present application, and it should be understood that the above only describes specific embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A dark field speckle illumination super-resolution imaging system based on a planar device, characterized in that: The system comprises: an image plane detector (1), an imaging tube lens (2), an imaging objective lens (3), a planar device (4), a 633 nm laser light source (5), and a vibrator (6), wherein the planar device (4) comprises a one-dimensional photonic crystal (7), a titanium dioxide scattering layer (8), a multimode optical fiber bundle (9), and a 300 nm thick gold film (10) stacked in sequence from top to bottom; The 633nm laser light source (5) emits a strong coherent light beam with a wavelength of 633nm, and the strong coherent light beam is incident on the planar device (4) through the multimode optical fiber bundle (9). The emitted laser is incident on the titanium dioxide scattering layer (8) for scattering. The scattered strong coherent light beams interfere with each other to form speckles and are incident on the one-dimensional photonic crystal (7). The one-dimensional photonic crystal (7) screens speckles with a numerical aperture greater than 0.6 to pass through the one-dimensional photonic crystal (7) and illuminate the sample on the one-dimensional photonic crystal (7); the scattered light emitted by the illuminated sample is collected by the imaging objective lens (3) and passes through the imaging tube lens (2) to reach the image plane detector (1) to form a dark field speckle pattern of the sample; The phase of the incident strong coherence light beam is changed by vibrating the multimode optical fiber bundle (9) with a vibrator (6) to obtain a plurality of different dark field speckle patterns, and the plurality of different dark field speckle patterns are restored using a conjugate gradient algorithm to obtain a high-resolution dark field image that exceeds the diffraction limit.

2. The dark field speckle illumination super-resolution imaging system based on a planar device according to claim 1, characterized in that: The 300 nm thick gold film (10) is used to reflect the strong coherent light beam scattered to the lower layer back into the titanium dioxide scattering layer (8).

3. The dark field speckle illumination super-resolution imaging system based on a planar device according to claim 1, characterized in that: The one-dimensional photonic crystal (7) is composed of SiO2 and Si3N4 nanofilms stacked alternately.

4. The dark field speckle illumination super-resolution imaging system based on a planar device according to claim 1, characterized in that: The numerical aperture of the imaging objective lens (3) is 0.6, and the magnification is 40 times.

5. The dark field speckle illumination super-resolution imaging system based on a planar device according to claim 1, characterized in that: The titanium dioxide scattering layer (8) is prepared by spin coating titanium dioxide particles with a size of 60 nm on a clean cover glass.

6. The dark field speckle illumination super-resolution imaging system based on a planar device according to claim 1, characterized in that: One end of the multimode optical fiber bundle (9) is randomly adhered to the upper surface of a 300 nm thick gold film (10) using α-ethyl cyanoacrylate.

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