Image edge extraction device based on ultrahigh-order guided mode

Abstract

The invention provides an image edge extraction device based on an ultrahigh-order guided mode. The image edge extraction device based on the ultrahigh-order guided mode comprises a laser source, a lens group, an image to be detected, an optical differentiator and a signal receiver, the laser source is used for emitting and outputting a light beam which carries amplitude optical information of an image after passing through the to-be-measured image; the lens group is used for assisting optical information transmission; the optical differentiator is a double-sided metal coated waveguide, an incident light beam is incident to the optical differentiator at a small angle and then excites an ultra-high-order guided mode, the critical condition of a space coupling mode theory is met by controlling the space transmission leakage rate of the ultra-high-order guided mode and the loss rate of a material, and first-order differential operation of an input light field is achieved; the signal receiver is used for receiving the edge information of the to-be-detected image processed by the optical differentiator; compared with a device for realizing optical differential operation through surface plasmon, the image edge extraction device based on the optical differentiator can realize multi-angle and dual-polarization edge information extraction, has higher resolution, provides a mode for high-speed parallel processing of image edge information, and has important application prospects in the technical field of microscopic imaging.

Description

Technical Field

[0001] The present invention relates to the technical field of optical information processing, and in particular to an image edge extraction device based on ultra-high-order guided modes. Background Art

[0002] As a basic mathematical operation, differential operation has important application value in various scientific fields. Especially in image processing, differential operation can realize edge extraction of image, thereby obtaining key geometric structure information in the image, which is an important prerequisite for subsequent target recognition, feature classification or data compression. The spatial distribution of light field is essentially the natural expression of image information. Therefore, spatial light field differential operation will play an important role in future optical computing or edge computing.

[0003] Optical differential operations have the advantages of low power consumption and high-speed parallel processing. They can efficiently extract discontinuities in brightness, color or other properties of objects, which makes optical differential operations very attractive in edge detection. So far, researchers have successfully proposed many optical differentiators. Traditional optical differentiators use the Fourier transform characteristics of lenses to use two lenses to form a 4f system to select appropriate spatial filters on their spectrum planes for light field differential operations. However, the lens is large in size and occupies a large space, which is not conducive to device integration and market mass production needs. With the rapid development of micro-nano processing technology, designing lightweight and small optical devices that can be mass-produced has become a future trend. According to literature research, in 2017, Zhejiang University published a paper on spatial optical differential computing based on surface plasmons [Nature Communications] (Plasmonic computing of spatial differentiation). By customizing the thickness of the metal layer to meet the critical conditions of the spatial coupled mode theory, the spatial spectral transfer function and the wave vector are made consistent. It is proportional to the light, realizing one-dimensional differential operation. However, the differentiator needs to use a prism (which is large in size), and the excitation mode (TM mode) and the incident angle are fixed, which is not conducive to the flexible adjustment of optical differential calculation.

[0004] In summary, in view of the problems existing in the above-mentioned prior art, there is an urgent need for a new high-performance optical differentiator which is flexible in regulation, simple in manufacturing, easy in integration, and suitable for the needs of large-scale production in the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 A schematic diagram of the working principle of an image edge extraction device based on ultra-high-order guided modes provided by an embodiment of the present invention;

[0006] Figure 2A schematic diagram of the structure of an ultra-high-order guided mode optical differentiator provided by an embodiment of the present invention;

[0007] Figure 3 A diagram of an image edge extraction device based on ultra-high-order guided modes provided by an embodiment of the present invention;

[0008] Figure 4 The reflection spectrum and spatial spectrum transfer function of the TM mode and TE mode on the double-sided metal-clad waveguide provided in the embodiment of the present invention;

[0009] Figure 5 A schematic diagram comparing the spatial spectrum transfer functions based on surface plasmons and ultra-high-order guided mode differentiators provided in an embodiment of the present invention;

[0010] Figure 6 Providing an edge detection result diagram of an image to be tested for an embodiment of the present invention; Summary of the invention

[0011] Based on the above description, the present invention provides an image edge extraction device of an ultra-high-order guided mode to solve the problems in the prior art that the optical differentiator is difficult to integrate, the incident polarization state is fixed, and the incident angle cannot be switched.

[0012] The technical solution of the present invention to solve the above technical problems is as follows:

[0013] The present invention provides an ultra-high-order guided mode image edge extraction device, comprising: a laser source, a lens group, an image to be measured, an optical differentiator and a signal receiver;

[0014] The laser source is used to emit an output light beam, and the light beam carries the amplitude optical information of the image after passing through the image to be measured;

[0015] The lens group is used to assist in the transmission of optical information of the image;

[0016] The optical differentiator is used for differential operation processing of optical information of the image to be measured, and retains the required edge information;

[0017] The signal receiver is used to receive and analyze edge information of the image to be tested;

[0018] On the basis of the above technical solution, the present invention is further limited.

[0019] Furthermore, the far-field divergence angle of the laser source should be less than 1.7 MRAD.

[0020] Furthermore, the optical differentiator is a double-sided metal-clad waveguide structure, and its composition structure is noble metal-transparent medium-noble metal.

[0021] Furthermore, the noble metals are used as a coupling layer and a substrate layer, respectively, with thicknesses of 30-50 nm and 300-500 nm.

[0022] Furthermore, the transparent medium has a thickness of sub-millimeter order (0.1 mm to 0.5 mm).

[0023] Furthermore, the double-sided metal-clad waveguide structure is used to transmit the incident light beam at a relatively small angle (2-10 o )The incident excites the ultra-high-order guided mode and reflects.

[0024] Furthermore, the double-sided metal-clad waveguide structure can adjust the coupling layer thickness parameter to meet the critical condition of the spatial coupled mode theory, that is, the spatial leakage rate ( ) and the loss rate in the material ( ) is approximately equal to ( ).

[0025] Furthermore, after the incident light beam is reflected by the double-sided metal-clad waveguide, the spatial spectrum transfer function ( ( )) and wave vector Linear distribution.

[0026] Furthermore, the incident angle of the light beam on the double-sided metal-clad waveguide is It is selective and can realize optical differential operations at multiple angles, and it can be realized when the incident light beam is polarized in TM mode or TE mode.

[0027] Compared with the prior art, the technical solution of this application has the following beneficial technical effects:

[0028] Compared with the prior art, the optical differentiator provided by the present invention uses a double-sided metal-clad waveguide as a differentiator, does not require a large prism, and can excite ultra-high-order guided modes at a small angle of incidence. By designing the material parameters of the metal coupling layer and the transparent medium to meet the critical conditions of the spatial coupling mode theory, one-dimensional optical differential operations can be achieved. It is worth noting that the optical differentiator of the present invention can be achieved under both TM mode and TE mode incidence and the incident angle can be switched. The present invention provides a method for high-speed parallel processing of image edge information, which has important application prospects in the field of microscopic imaging technology. DETAILED DESCRIPTION

[0029] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described in the present application. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0030] like Figure 1 The figure shows an embodiment of an image edge extraction device based on ultra-high-order guided modes. The entire system includes and is arranged in the following order: an optical information carrying system, an optical information imaging auxiliary system, an optical differentiator, and an image information analysis system.

[0031] The optical information carrying system includes a laser source and an image to be measured. The laser outputs continuous monochromatic laser light to illuminate the image to be measured. At this time, the light beam will carry the amplitude optical information of the image, and then pass through the optical information transmission auxiliary system composed of two lenses and then be incident on the optical differentiator. Here, the optical differentiator is a double-sided metal-clad waveguide. Finally, the light beam passes through the image information analysis system so that the edge information of the image is captured. Here, the image information analysis system is a charge coupled device (CCD).

[0032] The spatial light differentiator system is a double-sided metal-clad waveguide structure. By changing the physical parameters of the noble metal coupling layer and the transparent medium layer, such as thickness and material, it can satisfy the critical coupling condition of the spatial coupled mode theory, that is, when the incident light beam is incident at a small angle, it will excite the ultra-high-order guided mode. Here, the incident angle is not unique, and the spatial propagation leakage rate ( ) and material loss rate ( ) are approximately equal. The transfer function of the ultra-high-order guided mode optical differentiator near this spatial frequency is linear, that is, ,here To satisfy the incident angle of phase wave vector matching, is the phase change of the incident light beam after reflection in the double-sided metal-clad waveguide.

[0033] like Figure 2 The figure shows the edge device of the ultra-high-order guided mode image. For the sake of simplicity, the following parameters and materials are used as examples for explanation. The laser beam generated by the 632.8 nm continuous laser carries the cross-section cell image of the cotton stem. At this time, the beam carries the amplitude optical information of the cotton stem cells. After being transmitted through two lenses, it is incident on the double-sided metal-clad waveguide at a small angle through a reflector to excite the ultra-high-order guided mode. After meeting the theoretical critical conditions of the spatial coupling mode, the optical information of the image is differentiated, and the edge information of the image is retained. Finally, it is reflected by the reflector and transmitted through two lenses for optical information transmission and received by the CCD.

[0034] Figure 3The schematic diagram of the structure of an optical differentiator based on ultra-high-order guided mode resonance is shown in FIG. In this embodiment, a double-sided metal-clad waveguide composed of noble metal-transparent medium-noble metal is used to excite ultra-high-order guided modes. Specifically, the upper metal is a coupling layer (gold) with a thickness of 40 nm, the dielectric layer is a LiNbO3 crystal with a thickness of 0.3 mm, and the lower metal is a substrate layer (gold) with a thickness of about 350 nm.

[0035] Figure 4 (a, b) and (c, d) are the reflectivity and spatial spectral transfer function images of the double-sided metal-clad waveguide with the incident beam in TE mode and TM mode. It is obvious that the reflectivity has multiple resonance peaks in the range of 2 to 10 degrees, which means that light differential operations can be performed at multiple incident angles. At the same time, the spatial spectral transfer function selects the resonance peak corresponding to the black dotted box in the reflectivity image for experimental verification. The results show that the spatial spectral transfer function and the wave vector Proportional, very satisfying , which can realize one-dimensional optical differential operation. This scheme has no restrictions on the incident light beam in TM mode and TE mode, both of which can realize differential operation, and can realize multi-incident angle switching.

[0036] Figure 5 The images of the spatial spectral transfer functions of the differentiators based on surface plasmon and ultra-high-order guided modes are shown in Figure 2. The results show that the slope of the spatial spectral transfer function of the differentiator based on ultra-high-order guided modes is greater than that of the differentiator based on surface plasmon, indicating that the differentiator based on ultra-high-order guided modes has higher resolution when applied to image edge detection.

[0037] Figure 6 This is an example of using the above device to perform one-dimensional, first-order differential processing on the light field to achieve image edge extraction. The experimental results are very close to the theoretical results, thus proving the feasibility of the light differential device.

[0038] In the description of this specification, the description with reference to the terms "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An image edge extraction device based on ultra-high-order guided modes, characterized in that: include: Laser source, lens group, image to be measured, light differentiator and signal receiver; The laser source is used to emit an output light beam, and the light beam carries the amplitude optical information of the image after passing through the image to be measured; The lens group is used to assist in the transmission of optical information of the image; The optical differentiator is used for differential operation processing of the amplitude optical information of the image to be measured, and retains the required edge information; The signal receiver is used to receive edge information of the image to be measured extracted by the optical differentiator.

2. The image edge extraction device based on ultra-high-order guided modes according to claim 1, characterized in that: The components are arranged in the following order: laser source, lens group, image to be measured, light differentiator and signal receiver.

3. The image edge extraction device based on ultra-high-order guided modes according to claim 1, characterized in that: The far-field divergence angle of the laser source should be less than 1.7 MRAD.

4. The image edge extraction device based on ultra-high-order guided modes according to claim 1, characterized in that: The optical differentiator is a double-sided metal-clad waveguide structure, and its composition structure is noble metal-transparent medium-noble metal.

5. The optical differentiator according to claim 4, characterized in that: The noble metal layers are used as coupling layers and substrate layers, respectively, and have thicknesses of 30-50 nm and 300-500 nm.

6. The optical differentiator according to claim 4, characterized in that: The medium layer is a transparent medium with a thickness of sub-millimeter order (0.1 mm to 0.5 mm).

7. The optical differentiator according to claim 4, characterized in that: The double-sided metal-clad waveguide structure is used for incident light beams at a small angle (2-10 o )After the incident light, it excites the ultra-high-order guided mode and reflects, and satisfies the critical conditions of the spatial coupled mode theory to realize the differential operation of the incident light field.

8. The critical condition according to claim 7, characterized in that: The leakage rate of space during the transmission of ultra-high-order guided modes ( ) and the loss rate in the material ( ) is approximately equal to( ).

9. The critical condition according to claim 7, characterized in that: Spatial spectral transfer function ( ( )) and wave vector It is linearly distributed, that is , here To satisfy the incident angle of phase wave vector matching, is the phase change of the incident light beam after reflection in the double-sided metal-clad waveguide.

10. The spatial spectrum transfer function according to claim 9, characterized in that: Angle of incidence It is selective and can realize optical differential operation at multiple incident angles, and it can be realized when the incident light beam is in TM mode or TE mode.

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