Phase boundary detection system based on vortex light scanning

Abstract

The invention discloses a phase boundary detection system based on vortex light scanning, which comprises a light source module, an infinite imaging module and an imaging processing module, and is characterized in that focused vortex light is generated through a spiral phase plate to scan a sample, and then an infinite optical module is used for imaging a sample scanning point; the infinite optical system is provided with a spiral phase plate with the number opposite to the topological kernel number of incident light of a light source, an imaging processing module weakens a phase uniform region and strengthens a phase change region, an imaging result shows that the light intensity of a phase boundary is obviously higher than that of the phase uniform region, and the technical effect of strengthening the phase boundary is achieved. And the technical scheme has no influence on the imaging resolution.

Description

Technical Field

[0001] The invention relates to the technical field of optical imaging, and in particular to a phase boundary detection system based on vortex light scanning. Background Art

[0002] The detection, research and extraction of object edge feature information include the use of post-image processing methods or direct detection of object edges during the imaging process. Most of these methods place filters on the Fourier plane of the optical system to filter out or change specific Fourier components of the image to highlight the image boundary.

[0003] The most widely used method for edge detection based on spatial filtering is spiral phase contrast imaging, which was proposed by Jeffrey A. Davis et al. in the paper Image processing with the radial Hilbert transform: theory and experiments in 2000. The method is to place a spiral phase plate on the confocal Fourier surface of the 4f system. At this time, the areas with large changes in phase or intensity gradient on the imaging surface will be highlighted, but the uniform areas will be extinct. The final imaging effect is the highlighting of the image edge. In addition, the imaging quality is prone to uneven levels due to the limitations of system parameters and the high precision requirements of optical components, and the imaging resolution is not high. Summary of the invention

[0004] The embodiment of the present application provides a phase boundary detection system based on vortex light scanning, thereby achieving the imaging technical effect of phase boundary enhancement processing and phase uniformity weakening processing without affecting the imaging resolution.

[0005] The embodiment of the present application provides a phase boundary detection system based on vortex light scanning, comprising: A light source module, which uses a spiral phase plate to generate focused vortex light for the sample; An infinite imaging module, which uses the infinite imaging principle to image the sample, wherein the infinite imaging module comprises a spiral phase plate with a topological core opposite to that of the spiral phase plate of the light source module; The imaging processing module uses filters to weaken the light waves in the phase-uniform area and strengthen the light waves in the phase-varying area and capture and record the intensity; The rear focal plane of the light source module coincides with the front focal plane of the infinite imaging module, and the filter of the imaging processing module is placed on the rear focal plane of the infinite imaging module.

[0006] Preferably, the light source module is specifically composed of a focusing lens and a topological core number of The spiral phase plate.

[0007] Preferably, the infinite imaging system comprises two lenses or two objective lenses, and the topological core number between the two lenses or the two objective lenses is - Spiral phase plate.

[0008] Preferably, the imaging processing system comprises a filtering system of a centrally opaque 0th order filter and an intensity capturing system.

[0009] Preferably, the radius of the opaque area in the center of the 0th order filter is obtained by calculating the radius of the imaging surface light spot in the absence of a sample.

[0010] A technical solution provided in the embodiments of the present application has at least the following technical effects or advantages: 1. The present invention generates focused vortex light through a spiral phase plate to scan the sample, and then uses an infinite optical system to image the sample scanning point. The infinite optical system is provided with a spiral phase plate with a topological nucleus opposite to that of the incident light of the light source. The imaging processing module weakens the phase uniform area and strengthens the phase change area. The imaging results show that the light intensity at the phase boundary is significantly higher than the light intensity at the phase uniform point, thereby achieving the technical effect of strengthening the phase boundary. Moreover, this technical solution has no effect on the imaging resolution.

[0011] 2. In the technical solution provided by the present invention, there is no strict requirement for the distance setting of the two objective lenses or two lenses in the infinite imaging module. The entire technical solution involves fewer optical elements and a simple setting, has low operation requirements and is simple to operate, and has wide practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of the phase boundary detection system; Figure 2 Schematic diagram of the annular focused light field of the light source module scanning the sample; Figure 3 Figure 3 a is a schematic diagram of the light field distribution when scanning to the imaging surface with uniform phase. Figure 3 b is a schematic diagram of the light field distribution at the phase boundary on the imaging surface; Figure 4 Schematic diagram of a binary phase-type periodic grating; Figure 5 Figure 5 a is for Figure 4 The final imaging effect of the sample scanning along the dotted line. Figure 5 bFor Figure 4 Normalized intensity distribution of the sample scanned along the dashed line; Figure 6 Schematic diagram of imaging for a circular phase object; 1- spiral phase plate; 2- focusing lens; 3- sample surface; 4- first lens; 5- spiral phase plate; 6- second lens; 7- central opaque 0th order filter (i.e. imaging surface); 8- photodetector CCD. DETAILED DESCRIPTION

[0014] The embodiment of the present application provides a phase boundary detection system based on vortex light scanning, thereby achieving the imaging technical effect of phase boundary enhancement processing and phase uniformity weakening processing without affecting the imaging resolution.

[0015] The technical solution in the embodiment of the present application is to achieve the above technical effects, and the overall idea is as follows: The phase boundary detection system includes: a light source module, an infinite imaging module and an imaging processing module along the optical axis from the object side to the image side. The light source module includes a focusing lens and a topological core number of The spiral phase plate, the sample is located at the back focal plane of the focusing lens, the infinite imaging module contains two lenses, and there is a topological core number between the two lenses. The spiral phase plate of the infinite imaging module is provided, the front focal plane of the first lens of the infinite imaging module coincides with the rear focal plane of the light source module, the imaging processing module comprises a center opaque 0-order filter and an intensity detection system, the center opaque 0-order filter is arranged on the rear focal plane of the second lens of the infinite imaging module, and can weaken the light waves in the phase uniform area and strengthen the light waves in the phase change area, the intensity detection system detects and records the different intensities in the phase uniform area and the phase change area, and the final imaging result shows that the intensity at the phase boundary will be significantly higher than that at the uniform point, that is, the light intensity at the edge of the imaging surface object will be significantly higher than that at the uniform point, so that the edge detection can be realized, and the system provided by the present invention has no effect on the imaging resolution.

[0016] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods. Embodiment 1

[0017] The light source module includes a focal length of The focusing lens 1 and the number of topological cores are Spiral phase plate 2.

[0018] Infinity imaging module, including focal length The first lens 4, 1 topological core number The spiral phase plate 5 and the focal length are The second lens 6.

[0019] The imaging processing module includes a central light-proof 0-order filter 7 and a photodetector CCD 8.

[0020] Please refer to Figure 1 and Figure 2 The phase boundary detection system is divided into the following topological cores along the optical axis from the object side to the image side: The spiral phase plate 2, the focal length is The focusing lens 1, the sample surface 3, and the focal length are The first lens 4, topological core number The spiral phase plate 5, the focal length is The second lens 6, the center opaque 0-order filter 7 (i.e., the imaging surface), and the photodetector CCD 8.

[0021] Among them, the sample plane 3 has a focal length of The back focal plane of focusing lens 1 has a focal length of The front focal plane of the first lens 4 coincides with the sample plane 3 .

[0022] The focal length is The rear focal plane of the second lens 6 coincides with the imaging plane.

[0023] The size of the opaque area in the center of the filter is adjusted by calculating the radius of the imaging spot in the absence of a sample. In this embodiment, the radius is circular area.

[0024] The specific phase boundary detection imaging operation is: First, the Gaussian light emitted by the laser is expanded and becomes a nearly plane wave Gaussian beam. The spiral phase plate 2 and the focal length are The beam waist radius after focusing by focusing lens 1 is for The ring-shaped spot is used to scan the sample. At this time, two situations will occur: (1) Please refer to Figure 3 a. If the annular light field falls in the area where the sample transmission phase or amplitude is uniform, the spiral wavefront of the beam It will not be destroyed, but will only impose a phase or weaken its intensity. Therefore, the number of topological nuclei in the infinite imaging module is After the spiral phase plate 5, the spiral phase will be offset and turned into a plane wave or a near-plane Gaussian light again. According to the principle of Fourier optics, most of the light intensity on the final imaging surface will be located at the origin and its vicinity, and at this time it will be filtered out by the 0th order filter 7 in the filtering system, and the photodetector CCD 8 cannot respond to it.

[0025] (2) Please refer to Figure 3b. If the annular light field falls in the region where the sample transmission phase or amplitude has a change, the object will scatter the light at the focus, and the spiral wavefront will be destroyed and become a complex wavefront. Then, the number of topological cores in the infinite imaging module is After the spiral phase plate 5, it cannot be restored to a plane wave or a nearly plane Gaussian light. At this time, in addition to the 0th-order Fourier component, there are also high-order components. Therefore, in addition to the light intensity distribution at the origin, there will be irregular distribution in other areas on the imaging surface. Most of the light intensity after passing through the 0th-order filter 7 on the imaging surface is not distributed at the origin. At this time, the intensity obtained by the photodetector CCD 8 will be much higher than the intensity when scanning to a uniform area.

[0026] The light intensity at the phase boundary of the final imaging surface will be significantly higher than the uniform point, that is, the light intensity at the edge of the sample will be significantly higher than other places, thereby achieving edge detection.

[0027] A sample of a binary periodic grating structure was selected for edge detection experiments.

[0028] A binary periodic grating structure sample is a typical phase-type object, and its transmission function can be expressed as:

[0029] Please refer to Figure 4 and Figure 5 ,in is the period, here is We scan along the dotted line. Figure 5 a is the imaging effect, Figure 5 b is the normalized intensity. It can be clearly seen that the phase change of the two-dimensional periodic grating is the intensity peak, while the light intensity at the uniform point is significantly suppressed, which clearly reflects the periodic information of the binary grating. Ordinary confocal scanning imaging can hardly distinguish the periodic boundary of the binary grating.

[0030] The system can detect any structure and any direction of the boundary. Please refer to Figure 6 , taking the circular structure as an example, its transmission function is expressed as:

[0031] in is the pupil function, is the radius of the central phase change area, the simulation results are as follows Figure 6 As shown, for boundaries in any direction, the scanning imaging system of vortex light can achieve the same degree of imaging.

Claims

1. A phase boundary detection system based on vortex light scanning, comprising: A light source module, which uses a spiral phase plate to generate focused vortex light for the sample; An infinite imaging module, which uses the infinite imaging principle to image the sample, wherein the infinite imaging module comprises a spiral phase plate with a topological core opposite to that of the spiral phase plate of the light source module; The imaging processing module uses filters to weaken the light waves in the phase-uniform area and strengthen the light waves in the phase-varying area, and then captures and records the intensity. The rear focal plane of the light source module coincides with the front focal plane of the infinite imaging module, namely, the sample plane; the filter of the imaging processing module is arranged on the rear focal plane plane of the infinite imaging module, namely, the imaging plane.

2. The system according to claim 1, characterized in that The light source module is specifically composed of a focusing lens and a topological core number of The spiral phase plate.

3. The system according to claim 2, characterized in that The infinite imaging system includes two lenses or two objective lenses, and the topological core number between the two lenses or the two objective lenses is - Spiral phase plate.

4. The system according to claim 1, characterized in that The imaging processing system includes a filtering system of a central light-proof 0-order filter and an intensity capture system.

5. The system according to claim 4, characterized in that The radius of the opaque area in the center of the 0th order filter is obtained by calculating the radius of the imaging surface light spot in the absence of a sample.

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