An ultra-resolution microscopic imaging system based on mask phase modulation
By introducing an optical mask for phase modulation into the microscopic imaging system, the problem of insufficient imaging resolution in the existing technology is solved, and high-resolution microscopic imaging is achieved, which is suitable for rapid, large-area imaging measurement in industrial fields.
Patent Information
- Application Number
- CN202310480281.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-04-28
- Publication Date
- 2025-11-11
- Estimated Expiration
- 2043-04-28
AI Technical Summary
Existing optical microscopy imaging techniques struggle to overcome the diffraction limit, especially when imaging non-fluorescent samples, resulting in insufficient imaging resolution. Furthermore, existing non-fluorescent super-resolution microscopy imaging techniques are deficient in real-time imaging and image quality.
Phase modulation is achieved by using an optical mask. By introducing an optical mask into the microscopic imaging system, a π phase difference is generated between adjacent regions, thereby improving the imaging resolution and breaking through the diffraction limit.
It achieves high-resolution imaging of microscopes, which can clearly distinguish details that were originally indistinguishable, without the need for multiple imaging and image post-processing, and is suitable for rapid, large-area, and high-precision industrial imaging measurements.
Smart Images
Figure CN116520545B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of optical microscopy imaging technology, specifically relating to a super-resolution microscopy imaging system based on mask phase modulation. Background Technology
[0002] Typically, the imaging resolution of an optical microscope is determined by both the numerical aperture of its objective lens and the wavelength of the illumination source. Therefore, the imaging resolution can be improved by shortening the illumination wavelength and increasing the numerical aperture of the objective lens. However, shorter wavelengths mean higher photon energy, leading to greater optical damage to the imaged sample, especially biological samples; and the numerical aperture of the objective lens is determined by both the maximum light-receiving angle of the objective lens and the refractive index of the working medium. Limited by the refractive index of the immersion liquid, it is difficult to further increase the numerical aperture of the objective lens.
[0003] Among existing super-resolution microscopy techniques, fluorescence microscopy, represented by STED, STORM, and PALM, has achieved nanometer-level imaging resolution, greatly promoting the rapid development of biomedicine. However, these techniques are ineffective for non-biological samples that cannot be stained. In non-fluorescence super-resolution microscopy, structured light illumination is the most mature technique. During imaging, the sample is illuminated with structured light of different directions and phases, and the surface morphology is inverted based on the moiré fringes received by the objective lens. Therefore, the imaging process is a multi-frame inversion calculation, making real-time imaging difficult. Point spread function engineering can effectively reduce the size of the diffuse spot, thereby improving imaging resolution. However, while reducing the size of the central bright spot, it also reduces the Strell ratio of the central bright spot, meaning the energy of the side lobes continuously increases, ultimately leading to image blurring and a decrease in imaging quality. Other non-fluorescence super-resolution microscopy techniques also have their own advantages and disadvantages and their own application areas. Summary of the Invention
[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a super-resolution microscopic imaging system based on mask phase modulation. By utilizing the phase modulation function of the optical mask, an additional π phase difference is generated between adjacent grids, thereby enabling the microscope to distinguish adjacent grids that were originally indistinguishable. In other words, the resolution of the microscope is greatly improved and the diffraction limit can be broken.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] A super-resolution microscopy imaging system based on mask phase modulation includes an illumination source 6 for generating monochromatic plane waves, an imaging sample 4 for reflecting the generated monochromatic plane waves, a microscope objective 3 and a tube lens 2 for receiving far-field light intensity, a CCD 1 for imaging, and an optical mask 5 for modulating the phase of each adjacent region disposed between the illumination source 6 and the imaging sample 4.
[0007] The optical mask 5 consists of a substrate 7 and a protrusion 8 connected to the substrate 7, both of which are transparent dielectric materials.
[0008] The relationship between the thickness h of the protrusion 8 of the optical mask 5 and the incident wavelength is: h = λ / 2(n-1), where n is the refractive index of the optical mask 5.
[0009] The protrusions 8 of the optical mask 5 are arranged at periodic intervals, and the feature size of the protrusions 8 is on the order of hundreds of nanometers.
[0010] The resolution of the system is determined by the grid precision of the optical mask 5, that is, the resolution of the imaging system in each direction is equal to the spatial period of the grid in that direction.
[0011] The transparent dielectric material is SiO2, MgF2, or ITO.
[0012] Compared with the prior art, the present invention has the following beneficial effects:
[0013] A mask-based phase modulation super-resolution optical microscopy system is disclosed. Compared to ordinary optical microscopes, the most significant feature of this invention is the introduction of an optical mask. Utilizing the phase modulation function of the optical mask 5, the microscope can achieve higher imaging resolution, which is not limited by the diffraction limit but depends only on the grid precision of the mask. If a high-precision optical mask 5 can be fabricated, the imaging resolution of the optical microscope can be continuously improved.
[0014] Compared to other super-resolution imaging technologies, this invention does not require point-by-point scanning, multiple imaging, or image post-processing. It is also highly compatible with ordinary optical microscopes and can be applied to industrial fields that require large-area, high-precision, and rapid imaging measurements. It features simple operation, low cost, and high efficiency. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the structure of the present invention; wherein: 1, imaging CCD; 2, tube lens; 3, microscope objective; 4, imaging sample; 5, optical mask; 6, illumination source.
[0016] Figure 2The images show the imaging effects of two point light sources with the same amplitude, frequency, polarization, and phase, separated by different distances. Among them: (a) is the imaging effect when the two point light sources are in phase; (b) is the imaging effect when the phase difference between the two point light sources is π / 3; (c) is the imaging effect when the phase difference between the two point light sources is 2π / 3; and (d) is the imaging effect when the phase difference between the two point light sources is π.
[0017] Figure 3 The following diagram illustrates the effect of phase difference on the imaging resolution of point light sources in this invention: (a) shows the imaging effect when the two point light sources are in phase; (b) shows the imaging effect when the phase difference between the two point light sources is π / 3; (c) shows the imaging effect when the phase difference between the two point light sources is 2π / 3; and (d) shows the imaging effect when the phase difference between the two point light sources is π.
[0018] Figure 4 This is a schematic diagram of the structure of the optical mask 5 in this invention; wherein: 7, substrate; 8, protrusion.
[0019] Figure 5 The present invention compares the imaging effects of two point targets with and without a mask; wherein: (a) the imaging target is two circular holes in a metal film; (b) the imaging effect of the imaging target is two circular holes in a metal film; (c) the optical mask 5 with a film thickness difference of λ / 2 between the left and right sides; (d) the imaging effect of using the optical mask 5 in (c) with the imaging target being two circular holes in a metal film; (e) the imaging target is five circular holes in a metal film; (f) the imaging effect of the imaging target being five circular holes in a metal film; (g) the optical mask 5 with a micro-unit size of 400nm*400nm; (h) the imaging effect of using the optical mask 5 in (g) with the imaging target being five circular holes in a metal film.
[0020] Figure 6 The images show a comparison of the imaging effects of a line target with and without a mask in this invention; where: (a) the imaging target is a line structure etched in a metal thin film; (b) the imaging result without using the optical mask 5; (c) the optical mask 5 with a grid length and width of 400nm*400nm; and (d) the imaging result using the optical mask 5.
[0021] Figure 7 The present invention compares the imaging effects of an imaging sample under masks of different sizes, wherein: (a) the imaging target is two oblique lines with gradually changing spacing; (b) the imaging result without using optical mask 5; (c) the imaging effect when using optical mask 5 with a grid length and width of 400nm*400nm; and (d) the imaging effect when using optical mask 5 with a grid length and width of 300nm*300nm. Detailed Implementation
[0022] To make the technical problems solved, technical solutions, and beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and do not limit the present invention; the detailed description is as follows.
[0023] Reference Figure 1 A super-resolution microscopic imaging system based on mask phase modulation, comprising, in sequence:
[0024] Illumination source 6 for generating monochromatic plane waves;
[0025] Optical mask 5 used to modulate the phase of each adjacent region;
[0026] Imaging sample 4 for the monochromatic plane wave generated by reflection;
[0027] Microscope objective 3 and tube lens 2 are used to receive far-field light intensity;
[0028] CCD1 used for imaging.
[0029] The microscope objective 3, the tube lens 2, and the CCD 1 are no different from the devices used in ordinary optical microscopes.
[0030] The optical mask 5 consists of a substrate 7 and a protrusion 8 connected to the substrate 7, both of which are transparent dielectric materials.
[0031] The relationship between the thickness h of the protrusion 8 of the optical mask 5 and the incident wavelength is: h = λ / 2(n-1), where n is the refractive index of the optical mask 5.
[0032] The protrusions 8 of the optical mask 5 are arranged at periodic intervals, and the feature size of the protrusions 8 is on the order of hundreds of nanometers.
[0033] The resolution of the system is determined by the grid precision of the optical mask 5, meaning the resolution of the imaging system in each direction is equal to the spatial period of the grid in that direction. For example, if the grid period in the x-direction is 100 nm, then the imaging resolution limit of the imaging system in the x-direction is 100 nm.
[0034] To explain the super-resolution imaging principle involved in this invention, Figure 2 and Figure 3 The imaging effect of a point light source was simulated. Figure 2In this simulation, we modeled the imaging effects of two point light sources with the same frequency (wavelength λ = 500 nm), amplitude, polarization (electric field vibrating along the X direction), and phase at different distances. (a) shows the positions of the two point light sources; (b) shows the imaging effect when the distance between the two point light sources is 600 nm, where they are clearly distinguishable; (c) shows the imaging effect when the distance is 500 nm, where they are just distinguishable; and (d) shows the imaging effect when the distance is 400 nm, where they are indistinguishable.
[0035] exist Figure 3 In our simulation, we continued to set the spacing between the point light sources to 400 nm, keeping other parameters unchanged, and only modulated the phase difference between the two point light sources. (a) shows the imaging effect when the two point light sources are in phase, and they are indistinguishable; (b) shows the imaging effect when the phase difference between the two point light sources is π / 3, and they are barely distinguishable; (c) shows the imaging effect when the phase difference between the two point light sources is 2π / 3, and they are clearly distinguishable; (d) shows the imaging effect when the phase difference between the two point light sources is π, at which point the two are best distinguishable. Further simulation studies found that when the phase difference between the two point light sources is π, no matter how close they are, the blur spots after imaging can always be distributed.
[0036] Reference Figure 4 The optical mask 5 is a transparent optical film, which is composed of a substrate 7 and a protrusion 8 connected to the substrate 7. Both the substrate 7 and the protrusion 8 are transparent dielectric materials.
[0037] The height of protrusion 8 is λ / 2, determined by the incident wavelength. The surface of the optical mask 5 has a periodic micro / nano structure, namely the substrate 7 and protrusion 8. Each micro-unit has the same size, and the film thickness of any two adjacent micro-units differs by λ / 2. Therefore, when the incident light passes through the mask, the phase difference between two adjacent micro-units is π.
[0038] In this invention, an optical mask 5 is placed over an imaging sample 4. After passing through the optical mask 5, a monochromatic plane wave reaches the imaging sample 4. At this time, the phase difference between any two adjacent micro-units on the sample is π. Two micro-units that were originally inseparable can be separated. Therefore, after covering the optical mask 5, the imaging resolution of the optical microscopy system can be greatly improved.
[0039] To demonstrate the performance of the mask phase modulation super-resolution microscopy system involved in this invention, the following examples will be used for simulation verification.
[0040] Reference Figure 5The imaging targets are two circular holes (a) and five circular holes (e) in the metal film, respectively, with a center-to-center spacing of 400 nm between adjacent holes. Without using an optical mask, the imaging effects are shown in (b) and (f), respectively, where adjacent point targets are indistinguishable (the incident wavelength used in the simulation was 500 nm, and the numerical aperture of the objective lens was 0.9). To distinguish the two point targets shown in (a), we used the mask shown in (c), with a film thickness difference of λ / 2 on the left and right sides. Covering the imaging sample with this mask, we obtained the imaging effect shown in (d), where the two point targets are clearly distinguished. Similarly, for the imaging target shown in (e), we used the mask shown in (g), with a micro-unit length and width of 400 nm * 400 nm. The imaging effect is shown in (h), where adjacent point targets are all distinguished.
[0041] Reference Figure 6 The imaging target is a linear structure etched in a thin metal film, as shown in Figure (a). The linewidth is 100 nm, and the center-to-center distance between adjacent lines is 400 nm. Without using an optical mask, the imaging result is shown in Figure (b), where the three lines cannot be accurately distinguished. If an optical mask with a grid width and length of 400 nm * 400 nm is used, as shown in Figure (c), the imaging effect is shown in Figure (d), where the three lines can be clearly distinguished.
[0042] Reference Figure 7 The imaging target is two diagonal lines with gradually changing spacing, as shown in Figure (a). When imaging directly without a mask, the imaging effect is shown in Figure (b). The upper two diagonal lines are too close together to be distinguishable; while the lower two diagonal lines are too close together to be distinguishable. The imaging resolution of the system can be compared by observing the separation position of the two diagonal lines. Figure (c) shows the imaging effect using an optical mask with a grid size of 400nm*400nm. Comparing it to Figure (b), it can be seen that the two lines are distinguished at a higher position, resulting in higher resolution. If an optical mask with a grid size of 300nm*300nm is used, the imaging effect is shown in Figure (d), further improving the imaging resolution. Therefore, the resolution of the imaging system can be improved by continuously reducing the grid size of the mask.
[0043] This invention attributes imaging resolution to the mesh size of the mask; a finer mesh mask will achieve higher imaging resolution. The specific principle is as follows:
[0044] Whether two point light sources can be distinguished on the image plane depends not only on the spatial distance between them, but also on their frequency, amplitude, polarization, and phase, with phase information being the most sensitive. When the phase difference between the two point light sources is π, the two diffuse spots on the image plane can be separated regardless of their proximity. This can be understood as the two point light sources interfering destructively at the midpoint of the line connecting them, meaning the intensity at that point is always zero. Therefore, there is always a zero point in the light intensity distribution along the line connecting the two diffuse spots. Using this principle, two point targets that would otherwise be inseparable can be separated by placing a mask with an optical path difference of λ / 2 in front of one point target. This transforms the two point targets into two point light sources with a phase difference of π, thus separating them. Similarly, this principle can be extended to other imaging targets, such as line targets, area targets, and even imaging samples of arbitrary images.
[0045] Therefore, the mask-based phase modulation super-resolution microscopy imaging scheme involved in this invention has an imaging resolution that depends only on the fabrication accuracy of the phase mask. The imaging process requires no scanning imaging, no fluorescence staining, and no image post-processing, making it compatible with ordinary optical microscopes. Compared to ordinary optical microscopes, it requires covering the sample surface with a specially designed optical mask, making it suitable for large-area rapid imaging of ultra-precise surfaces. It can be applied to rapid imaging measurements of high-precision, large-area industrial samples, such as surface defect detection in semiconductor chips.
Claims
1. A super-resolution microscopic imaging system based on mask phase modulation, comprising, sequentially arranged, an illumination source (6) for generating monochromatic plane waves, an imaging sample (4) for reflecting the generated monochromatic plane waves, a microscope objective (3) and a tube lens (2) for receiving far-field light intensity, and a CCD (1) for imaging, characterized in that, An optical mask (5) for modulating the phase of each adjacent region is disposed between the illumination source (6) and the imaging sample (4); the optical mask (5) consists of a substrate (7) and protrusions (8) connected to the substrate (7), both the substrate (7) and the protrusions (8) are transparent dielectric materials; the relationship between the thickness h of the protrusions (8) of the optical mask (5) and the incident wavelength is: h=λ / 2(n-1), where n is the refractive index of the optical mask (5); the protrusions (8) of the optical mask (5) are arranged in a periodic interval, and the characteristic size of the protrusion (8) structure is on the order of hundreds of nanometers.
2. The super-resolution microscopy imaging system according to claim 1, characterized in that, The resolution of the system is determined by the grid precision of the optical mask (5), that is, the resolution of the imaging system in each direction is equal to the spatial period of the grid in that direction.
3. The super-resolution microscopy system according to claim 1, characterized in that, The transparent dielectric material is SiO2, MgF2, or ITO.