A method and device for evaluating the stealth characteristics of a columnar grating

Abstract

The application discloses an evaluation method and an evaluation device for the stealth property of a columnar grating. The evaluation method comprises the following steps: firstly, calculating the theoretical critical stealth object distance of an object to be observed through a columnar grating with preset grating attribute parameters according to a theoretical critical stealth object distance formula of the columnar grating; secondly, changing the position of the object to be observed within a preset object distance range and acquiring images formed after the object to be observed passes through the columnar grating with the preset grating attribute parameters in real time; and finally, performing similarity analysis on the images formed after the object to be observed passes through the columnar grating with the preset grating attribute parameters and standard images to evaluate the stealth property of the columnar grating with the preset grating attribute parameters. The stealth property of the columnar grating with the preset grating attribute parameters can be evaluated clearly, accurately, quickly and intuitively by using the method, and the method has good experimental demonstration effect and measurement function, and has important guiding significance for designing and manufacturing the columnar grating with good optical stealth effect.

Description

Technical Field

[0001] The present invention relates to the field of optical stealth imaging technology, and in particular to a method and apparatus for evaluating stealth characteristics using a cylindrical grating. Background Technology

[0002] Lattice gratings are widely used in the printed display industry and professional applications of electronic displays due to their simple structure, manufacturing process, and readily available materials. Currently, however, there is no mature technology for using lattice gratings to achieve object invisibility. Although lattice gratings have seen some development in the field of visual displays, and methods for achieving "digital invisibility" using lattice gratings exist, these methods rely on computer assistance and are not physical methods; their implementation is subject to certain conditions and difficulties. Summary of the Invention

[0003] This invention provides a method and apparatus for evaluating the stealth properties of objects using columnar gratings, which has strong guiding significance for achieving object stealth through relatively simple physical methods using columnar gratings.

[0004] In a first aspect, embodiments of the present invention provide a method for evaluating stealth properties using a cylindrical grating, comprising:

[0005] Based on the theoretical critical invisible distance formula of the cylindrical grating, the theoretical critical invisible distance of the object to be observed through the cylindrical grating with preset grating attribute parameters is calculated.

[0006] The position of the object to be observed is changed within a preset object distance range, and the image formed by the object to be observed after passing through the cylindrical grating with the preset grating attribute parameters is acquired in real time; wherein, the preset object distance range includes the theoretical critical invisibility object distance of the cylindrical grating with the preset grating attribute parameters.

[0007] The similarity analysis is performed between the image formed by passing the object to be observed through the cylindrical grating with the preset grating attribute parameters and the standard image to evaluate the stealth characteristics of the cylindrical grating with the preset grating attribute parameters.

[0008] Optionally, the theoretical critical invisibility distance formula for the cylindrical grating with preset grating attribute parameters is: Where r is the radius of curvature of the cylindrical grating with the preset grating attribute parameters, n0 is the refractive index of the cylindrical grating with the preset grating attribute parameters, l is the linear dimension of the cylindrical grating with the preset grating attribute parameters, d is the width of the object to be observed in the first direction, d' is the human eye resolution, and the first direction is the array arrangement direction of the cylindrical grating with the preset grating attribute parameters.

[0009] Before calculating the theoretical critical invisibility distance of the object to be observed through the cylindrical grating with preset grating attribute parameters, according to the theoretical critical invisibility distance formula of the cylindrical grating, the following steps are also included:

[0010] The ratio m of the width of the light spot formed by the object to be observed through the cylindrical grating with the preset grating attribute parameters in the first direction to the width of the object to be observed in the first direction is determined.

[0011] Optionally, determining the ratio m of the width of the light spot formed in the first direction by the object to be observed after passing through the cylindrical grating with the preset grating attribute parameters to the width of the object to be observed in the first direction includes:

[0012] In an optical physics field simulation, the ratio m of the light spot with a preset energy ratio formed after the object to be observed passes through the cylindrical grating with the preset grating attribute parameters to the width of the object to be observed in the first direction is determined.

[0013] Optionally, the preset energy ratio is greater than or equal to 86.5%.

[0014] Optionally, a similarity analysis is performed between the image formed by the object to be observed passing through the cylindrical grating with the preset grating attribute parameters and a standard image to evaluate the stealth properties of the cylindrical grating with the preset grating attribute parameters, including:

[0015] When the similarity between the image formed after the observed object passes through the cylindrical grating with the preset grating attribute parameters and the standard image meets the preset similarity range, it is determined that the theoretical critical invisible distance is reasonable.

[0016] Optionally, a similarity analysis is performed between the image formed by the object to be observed passing through the cylindrical grating with the preset grating attribute parameters and a standard image to evaluate the stealth properties of the cylindrical grating with the preset grating attribute parameters, including:

[0017] Based on the similarity analysis between the image formed by the object under observation after passing through the cylindrical grating with the preset grating attribute parameters and the standard image, the actual critical invisibility distance for the object under observation to become completely invisible after passing through the cylindrical grating with the preset grating attribute parameters is determined.

[0018] Secondly, embodiments of the present invention also provide a device for evaluating stealth characteristics using a columnar grating, comprising:

[0019] The object to be observed;

[0020] A columnar grating with preset grating attribute parameters;

[0021] A camera module is located on the side of the cylindrical grating with preset grating attribute parameters away from the object to be observed. The camera module is used to acquire, in real time, an image formed by the object to be observed passing through the cylindrical grating with preset grating attribute parameters when the position of the object to be observed is changed within a preset object distance range; wherein, the preset object distance range includes the theoretical critical invisibility distance of the cylindrical grating with preset grating attribute parameters.

[0022] A computer module is used to perform similarity analysis between the image formed by the object to be observed passing through the cylindrical grating with the preset grating attribute parameters and a standard image, and to evaluate the stealth characteristics of the cylindrical grating with the preset grating attribute parameters.

[0023] Optionally, it also includes a stepper motor module for automatically adjusting the relative position between the object to be observed and the cylindrical grating with the preset grating attribute parameters.

[0024] Optionally, it also includes a background whiteboard, which is located on the side of the object to be observed away from the columnar grating with the preset grating attribute parameters.

[0025] Optionally, the system also includes a base, which comprises a fixing and adjustment unit and a scale line unit. The fixing and adjustment unit is used to fix and / or adjust the positions of the object to be observed, the cylindrical grating with preset grating attribute parameters, and the camera module. The scale line unit is used to measure the distance between the object to be observed, the cylindrical grating with preset grating attribute parameters, and the camera module.

[0026] This invention provides a method and apparatus for evaluating the stealth characteristics of a cylindrical grating. The method first calculates the theoretical critical stealth distance of an object under observation through a cylindrical grating with preset grating attribute parameters, based on the theoretical critical stealth distance formula for the cylindrical grating. Then, it changes the position of the object under observation within a preset distance range and acquires images of the object through the cylindrical grating with preset grating attribute parameters in real time. The preset distance range includes the theoretical critical stealth distance of the cylindrical grating with preset grating attribute parameters. Finally, it performs a similarity analysis between the image of the object under observation through the cylindrical grating with preset grating attribute parameters and a standard image to evaluate the stealth characteristics of the cylindrical grating with preset grating attribute parameters. Using the above method, the similarity analysis between the image formed by the object under observation passing through the cylindrical grating with preset grating attribute parameters and the standard image can be performed. This allows for a clear, accurate, fast, and intuitive evaluation of the invisibility characteristics of the cylindrical grating with preset grating attribute parameters. Furthermore, it enables real-time observation of the invisibility phenomenon of the image formed by the object under observation passing through the cylindrical grating with preset grating attribute parameters. This method has good experimental demonstration effects and measurement functions, and is of great guiding significance for the design and manufacture of cylindrical gratings with good optical invisibility effects. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of a stealth characteristic evaluation device using a columnar grating provided in an embodiment of the present invention;

[0029] Figure 2 This is a flowchart illustrating a method for evaluating the stealth properties of a columnar grating according to an embodiment of the present invention.

[0030] Figure 3 This is a flowchart illustrating another method for evaluating the stealth properties of columnar gratings provided in an embodiment of the present invention.

[0031] Figure 4 This is a schematic diagram of the optical path of a stealth characteristic evaluation device using a columnar grating provided in an embodiment of the present invention;

[0032] Figure 5 This is a flowchart illustrating another method for evaluating the stealth properties of a columnar grating provided in an embodiment of the present invention.

[0033] Figure 6 This is a flowchart illustrating another method for evaluating the stealth properties of a columnar grating provided in an embodiment of the present invention. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0035] The terminology used in the embodiments of this invention is for the purpose of describing specific embodiments only and is not intended to limit the invention. It should be noted that directional terms such as "upper," "lower," "left," and "right" described in the embodiments of this invention are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of this invention. Furthermore, in the context, it should be understood that when referring to an element being formed "on" or "below" another element, it can be formed not only directly on or below the other element, but also indirectly on or below it through intermediate elements. The terms "first," "second," etc., are used for descriptive purposes only and do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] The term "comprising" and its variations as used in this invention are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment".

[0037] It should be noted that the concepts of "first" and "second" mentioned in this invention are only used to distinguish the corresponding contents and are not used to limit the order or interdependence.

[0038] It should be noted that the terms "a" and "a plurality of" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0039] Figure 1 This is a schematic diagram of a stealth characteristic evaluation device using a columnar grating provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the evaluation device includes: an object to be observed 10; a cylindrical grating 20 with preset grating attribute parameters; a camera module 30, located on the side of the cylindrical grating 20 away from the object to be observed 10, and the camera module 30 is used to acquire images of the object to be observed 10 after passing through the cylindrical grating 20 with preset grating attribute parameters in real time when the position of the object to be observed 10 is changed within a preset object distance range; wherein, the preset object distance range includes the theoretical critical invisibility distance of the cylindrical grating 20 with preset grating attribute parameters; a computer module ( Figure 1 (Not shown in the image, the computer module can perform image analysis and processing operations, and the location of the computer module is not limited), used to perform similarity analysis between the image formed after the object to be observed 10 passes through the cylindrical grating 20 with preset grating attribute parameters and the standard image, and to evaluate the stealth characteristics of the cylindrical grating 20 with preset grating attribute parameters.

[0040] Specifically, the object to be observed 10 can be a rectangular regular planar object. The projected area of ​​the object to be observed 10 on the plane containing the cylindrical grating 20 with preset grating attribute parameters is smaller than the projected area of ​​the cylindrical grating 20 with preset grating attribute parameters. For example, the object to be observed 10 can be a rectangular regular planar object of 20cm*4cm, the color of the object to be observed 10 can be green, and the material of the object to be observed 10 can be rigid cardboard. In the simulation of the optical physical field, the object to be observed 10 can be set as a light source, the light intensity of the object to be observed 10 follows a cosine distribution, and the light exitance of the object to be observed 10 is a constant value.

[0041] A cylindrical grating 20 with preset grating attribute parameters is located on the light path of the emitted light from the object 10. The surface of the cylindrical grating 20 with preset grating attribute parameters closer to the object 10 is planar, while the surface of the cylindrical grating 20 with preset grating attribute parameters farther from the object 10 is cylindrical. The surface of the cylindrical grating 20 with preset grating attribute parameters farther from the object 10 has curvature, and it changes the propagation direction of the light path only in one direction. The grating attribute parameters of the cylindrical grating 20 with preset grating attribute parameters include radius of curvature, refractive index, linear dimensions, and focal length. These grating attribute parameters can be preset, and the stealth characteristics of the cylindrical grating 20 with preset grating attribute parameters can be evaluated subsequently. For example, the cylindrical grating 20 with preset grating attribute parameters includes a plurality of sequentially arranged grating units to form a cylindrical lens array. The linear dimension of the cylindrical grating 20 with preset grating attribute parameters is less than or equal to twice the radius of curvature. The thickness of the cylindrical grating 20 with preset grating attribute parameters is the focal length. The thickness of the cylindrical grating 20 with preset grating attribute parameters can be 3 mm. The length of the cylindrical grating 20 with preset grating attribute parameters can be 50 cm. The width of the cylindrical grating 20 with preset grating attribute parameters can be 50 cm. The linear dimension range of the cylindrical grating 20 with preset grating attribute parameters can be 0.05 mm to 1.7 mm. This linear dimension range is much larger than the visible light wavelength range of 380 nm to 780 nm. It should be noted that diffraction only occurs when the linear dimension of the obstacle (or hole) is close to the wavelength of the light wave. Therefore, diffraction is not considered at the cylindrical grating 20 with preset grating attribute parameters in this embodiment of the invention, and only paraxial rays are considered based on geometric optics. In the simulation of the optical physical field, the spatial frequency of the cylindrical grating 20 with preset grating property parameters can be 30.24 LPI, the material can be PET, and the refractive index can be 1.65.

[0042] The camera module 30 is located on the side of the cylindrical grating 20 with preset grating attribute parameters away from the object 10 to be observed. The camera module 30 includes a camera 31 and a display screen 32. The camera 31 can capture the image formed after the object 10 to be observed passes through the cylindrical grating 20 with preset grating attribute parameters. The display screen 32 can display and record the image formed after the object 10 to be observed passes through the cylindrical grating 20 with preset grating attribute parameters, so as to facilitate the subsequent evaluation of the stealth characteristics of the cylindrical grating 20 with preset grating attribute parameters.

[0043] Optionally, continue to refer to Figure 1 The evaluation device also includes a stepper motor module 40 for automatically adjusting the relative position between the object to be observed 10 and the cylindrical grating 20 with preset grating attribute parameters.

[0044] Specifically, the evaluation device also includes a stepper motor module 40, which can automatically adjust the relative position between the object to be observed 10 and the cylindrical grating 20 with preset grating attribute parameters. For example, the stepper motor module 40 can adjust the position of the cylindrical grating 20 with preset grating attribute parameters so that the object to be observed 10 is located near the theoretical critical invisible object distance of the cylindrical grating 20 with preset grating attribute parameters.

[0045] Optionally, continue to refer to Figure 1 The evaluation device also includes a background whiteboard. Figure 1 (Not shown in the image), the background whiteboard is located on the side of the object to be observed 10 away from the columnar grating 20 with preset grating attribute parameters.

[0046] Specifically, the evaluation device also includes a background white board, which is located on the side of the object to be observed 10 away from the cylindrical grating 20 with preset grating attribute parameters. The projected area of ​​the background white board on the plane where the cylindrical grating 20 with preset grating attribute parameters is located is larger than the projected area of ​​the object to be observed 10. The background white board can provide better stealth experimental results for the evaluation process of the stealth characteristics of the cylindrical grating 20 with preset grating attribute parameters.

[0047] Optionally, continue to refer to Figure 1 The evaluation device also includes a base 50, which includes a fixing and adjustment unit 51 and a scale line unit 52. The fixing and adjustment unit 51 is used to fix and / or adjust the positions of the object to be observed 10, the cylindrical grating 20 with preset grating attribute parameters, and the camera module 30. The scale line unit 52 is used to measure the distance between the object to be observed 10, the cylindrical grating 20 with preset grating attribute parameters, and the camera module 30.

[0048] Specifically, the evaluation device also includes a base 50, on which the object to be observed 10, the cylindrical grating 20 with preset grating attribute parameters, the camera module 30, and the white background board are all located. A stepper motor module 40 is located on one side of the base 50. The base 50 includes a fixing and adjustment unit 51 and a scale line unit 52. The fixing and adjustment unit 51 can fix and / or adjust the positions (including horizontal and / or vertical positions) of the object to be observed 10, the cylindrical grating 20 with preset grating attribute parameters, and the camera module 30. The scale line unit 52 can measure the distance between the object to be observed 10, the cylindrical grating 20 with preset grating attribute parameters, and the camera module 30, thereby obtaining the object distance and / or critical invisible object distance of the object to be observed 10 through the cylindrical grating 20 with preset grating attribute parameters. The evaluation device used in this embodiment of the invention has a simple structure and low cost.

[0049] Figure 2 This is a flowchart illustrating a method for evaluating the stealth characteristics of a columnar grating according to an embodiment of the present invention. This embodiment is applicable to application scenarios that evaluate the stealth characteristics of a columnar grating with preset grating attribute parameters. The evaluation method can be executed by a device for evaluating the stealth characteristics of a columnar grating, which can be implemented in software and / or hardware. Figure 2 As shown, the evaluation method includes:

[0050] S110. Calculate the theoretical critical invisible distance of the object to be observed through the cylindrical grating with preset grating attribute parameters, based on the theoretical critical invisible distance formula of the cylindrical grating.

[0051] Among them, continue to refer to Figure 1 The grating attribute parameters can be radius of curvature, refractive index, linear dimensions, and focal length, etc. The preset grating attribute parameters are the grating attribute parameters of the cylindrical grating 20 with preset grating attribute parameters set in advance. Specifically, according to the theoretical critical invisibility distance formula of the cylindrical grating, under the constraints of the preset grating attribute parameters, the theoretical critical invisibility distance value of the object to be observed 10 through the cylindrical grating 20 with preset grating attribute parameters is calculated. For cylindrical gratings 20 with different preset grating attribute parameters, the calculated theoretical critical invisibility distance value is different. It should be noted that since the invisibility effect of the cylindrical grating 20 with preset grating attribute parameters is a process that gradually changes with the object distance, the magnitude of the theoretical critical invisibility distance is used to measure the invisibility effect of the cylindrical grating 20 with preset grating attribute parameters on the object to be observed 10.

[0052] S120. Change the position of the object to be observed within the preset object distance range, and acquire the image formed by the object to be observed after passing through the cylindrical grating with preset grating attribute parameters in real time; wherein, the preset object distance range includes the theoretical critical invisible object distance of the cylindrical grating with preset grating attribute parameters.

[0053] Specifically, please refer to Figure 1 The camera module 30 can acquire images formed by the object 10 passing through the cylindrical grating 20 with preset grating attribute parameters in real time when the relative position between the object 10 and the cylindrical grating 20 with preset grating attribute parameters is changed within a preset object distance range. The preset object distance range includes the theoretical critical invisibility distance of the cylindrical grating 20 with preset grating attribute parameters; that is, the object 10 moves near the theoretical critical invisibility distance of the cylindrical grating 20 with preset grating attribute parameters. For example, the object 10 can change its position within a movement range of 0.8 times to 1.2 times the theoretical critical invisibility distance of the cylindrical grating 20 with preset grating attribute parameters. Simultaneously, the camera module 30 acquires images formed by the object 10 passing through the cylindrical grating 20 with preset grating attribute parameters in real time. Furthermore, by gradually moving the object 10 from a position of 0.8 times the theoretical critical invisibility distance to a position of 1.2 times the theoretical critical invisibility distance, better image observation and contrast effects are achieved.

[0054] S130. Perform similarity analysis between the image formed by passing the object to be observed through a cylindrical grating with preset grating attribute parameters and a standard image to evaluate the stealth characteristics of the cylindrical grating with preset grating attribute parameters.

[0055] Specifically, please refer to Figure 1 The computer module 40 can perform image analysis and processing operations. The computer module 40 can import the image formed by the observed object 10 passing through the cylindrical grating 20 with preset grating attribute parameters according to the image algorithm programming, and perform similarity analysis between the image formed by the observed object 10 passing through the cylindrical grating 20 with preset grating attribute parameters and the standard image. The similarity value between the image formed by the observed object 10 passing through the cylindrical grating 20 with preset grating attribute parameters and the standard image is output, thereby evaluating the stealth characteristics of the cylindrical grating 20 with preset grating attribute parameters.

[0056] The technical solution in this embodiment of the invention first calculates the theoretical critical invisibility distance of the object to be observed through a cylindrical grating with preset grating attribute parameters, based on the theoretical critical invisibility distance formula of the cylindrical grating; then, the position of the object to be observed is changed within the preset distance range, and the image formed after the object to be observed passes through the cylindrical grating with preset grating attribute parameters is acquired in real time; wherein, the preset distance range includes the theoretical critical invisibility distance of the cylindrical grating with preset grating attribute parameters; finally, a similarity analysis is performed between the image formed after the object to be observed passes through the cylindrical grating with preset grating attribute parameters and a standard image to evaluate the invisibility characteristics of the cylindrical grating with preset grating attribute parameters. Using the above method, the similarity analysis between the image formed by the object under observation passing through the cylindrical grating with preset grating attribute parameters and the standard image can be performed. This allows for a clear, accurate, fast, and intuitive evaluation of the invisibility characteristics of the cylindrical grating with preset grating attribute parameters. Furthermore, it enables real-time observation of the invisibility phenomenon of the image formed by the object under observation passing through the cylindrical grating with preset grating attribute parameters. This method has good experimental demonstration effects and measurement functions, and is of great guiding significance for the design and manufacture of cylindrical gratings with good optical invisibility effects.

[0057] Figure 3 This is a flowchart illustrating another method for evaluating the stealth characteristics of a cylindrical grating provided in this embodiment of the invention. This embodiment is an optimization based on the above embodiment. Optionally, the theoretical critical stealth distance formula for the cylindrical grating with preset grating attribute parameters is: Where r is the radius of curvature of the cylindrical grating with preset grating attribute parameters, n0 is the refractive index of the cylindrical grating with preset grating attribute parameters, l is the linear dimension of the cylindrical grating with preset grating attribute parameters, d is the width of the object to be observed in the first direction, d' is the human eye resolution, and the first direction is the array arrangement direction of the cylindrical grating with preset grating attribute parameters.

[0058] Before calculating the theoretical critical invisibility distance of the object to be observed through the cylindrical grating with preset grating attribute parameters, according to the theoretical critical invisibility distance formula of the cylindrical grating, the following steps are also included:

[0059] Determine the ratio m between the width of the light spot formed by the object being observed through a cylindrical grating with preset grating attribute parameters in the first direction and the width of the object being observed in the first direction.

[0060] For details not covered in this embodiment, please refer to the above embodiments. Figure 3 As shown, the evaluation method includes:

[0061] S210. Determine the ratio m of the width of the light spot formed by the object to be observed in the first direction after passing through the cylindrical grating with preset grating attribute parameters to the width of the object to be observed in the first direction.

[0062] Optionally, determining the ratio m of the width of the light spot formed by the object being observed through a cylindrical grating with preset grating attribute parameters in the first direction to the width of the object being observed in the first direction includes: simulating in an optical physical field to determine the ratio m of the light spot with a preset energy ratio formed by the object being observed through a cylindrical grating with preset grating attribute parameters to the width of the object being observed in the first direction. Further, the preset energy ratio is greater than or equal to 86.5%.

[0063] Specifically, in the optical physical field simulation, the ratio *m* of the light spot with a preset energy ratio formed after the observed object passes through a cylindrical grating with preset grating attribute parameters to the width *m* of the observed object in the first direction is determined. This determines the light exitance distribution of the observed object after passing through the cylindrical grating with preset grating attribute parameters. For example, simulation software such as Zemax, CodeV, Matlab, Python, and COMSOL can be used. Based on the definition of the beam waist of a Gaussian beam, the light spot with the preset energy ratio formed after the observed object passes through the cylindrical grating with preset grating attribute parameters corresponds to the maximum light exitance of the observed object. If the light spot at this point has a preset energy ratio of 86.5%, it means that the light spot formed after the observed object passes through the cylindrical grating with preset grating attribute parameters contains the vast majority of the energy. The radius of curvature r, refractive index n0, linear dimension l, the width d of the observed object in the first direction, and the human eye resolution d' in the theoretical critical invisibility distance formula for the cylindrical grating with preset grating attribute parameters are all obtainable from the evaluation device. It is only necessary to simulate in the optical physical field to obtain the ratio m of the width m of the light spot formed after the observed object passes through the cylindrical grating with preset grating attribute parameters in the first direction to the width m of the observed object in the first direction. Substituting all these parameter values ​​into the theoretical critical invisibility distance formula for the cylindrical grating with preset grating attribute parameters, the value of the theoretical critical invisibility distance p0 can be obtained.

[0064] also, Figure 4 This is a schematic diagram of the optical path of a stealth characteristic evaluation device using a columnar grating provided in an embodiment of the present invention, as shown below. Figure 4 As shown, the theoretical critical invisible object distance formula for a cylindrical grating with preset grating attribute parameters is: The derivation process of the theoretical critical stealth distance formula is as follows:

[0065] Using vertex O1 of the planar imaging, the object to be observed undergoes planar refraction imaging. Then, using vertex O2 of the spherical imaging, the object to be observed undergoes single concave spherical refraction imaging. The object-image formulas for single spherical refraction are written twice. The total magnification formula for the two imaging processes of the object by the cylindrical grating with preset grating attribute parameters is calculated as follows: Among them, k1 is the magnification of plane refraction imaging, k2 is the magnification of single concave spherical refraction imaging, r is the radius of curvature of the cylindrical grating with preset grating property parameters, n0 is the refractive index of the cylindrical grating with preset grating property parameters, and p1 is the object distance of the plane imaging of the cylindrical grating with preset grating property parameters.

[0066] It should be noted that according to the sign rule of geometric optics and the geometric size of the lens (generally r << p1), it can be obtained that k < 0 and |k| << 1. Therefore, the entire imaging system always forms an inverted and reduced real image.

[0067] According to the Rayleigh criterion, considering the average value of the visible light wavelength (λ ≈ 550 nm) and the pupil diameter (D ≈ 3 mm), the best feature that the human eye can resolve at the near point of vision (L ≈ 25 cm) is Furthermore, it can be obtained that when the cylindrical grating with preset grating property parameters images a point object, when the object distance is small, the absolute value of the magnification is large, the imaging width is large, and the imaging will overlap; as the object distance increases, the image shrinks, changing from overlap to non - overlap, that is, the image separates. Due to the crosstalk effect between adjacent grating units of the cylindrical grating with preset grating property parameters, the light energy distribution of the imaging needs to be considered.

[0068] At the spot of the maximum luminous emittance of the object to be observed, most of the energy is contained, corresponding to the spot with a preset energy ratio greater than or equal to 86.5% formed after the object to be observed passes through the cylindrical grating with preset grating property parameters. When the spots formed after the object to be observed passes through the cylindrical grating with preset grating property parameters are separated, the images formed are separated far enough. At this time, the width of the spot formed after the object to be observed passes through the cylindrical grating with preset grating property parameters in the first direction is m times the width d of the object to be observed in the first direction.

[0069] Therefore, the derivation of the theoretical critical invisibility object distance formula is based on the critical conditions for the cylindrical grating with preset grating property parameters to make the object to be observed invisible: 1) When the spots with a preset energy ratio greater than or equal to 86.5% formed after the object to be observed passes through the cylindrical grating with preset grating property parameters are just separated, it is considered that a series of reduced images formed by the object to be observed are separated far enough; 2) The width of the spot with a preset energy ratio greater than or equal to 86.5% formed after the object to be observed passes through the cylindrical grating with preset grating property parameters in the first direction is less than the resolution of the human eye d' = 0.056 mm.

[0070] According to the above two critical conditions and the total magnification formula of the object to be observed's two - time imaging, it can be obtained that: kd < d' & mkd < (1 + k)l, that is, the theoretical critical invisibility object distance formula of the cylindrical grating with preset grating property parameters can be obtained as

[0071] S220. Calculate the theoretical critical invisible distance of the object to be observed through the cylindrical grating with preset grating attribute parameters, based on the theoretical critical invisible distance formula of the cylindrical grating.

[0072] S230. Change the position of the object to be observed within a preset object distance range, and acquire in real time the image formed by the object to be observed after passing through the cylindrical grating with preset grating attribute parameters; wherein, the preset object distance range includes the theoretical critical invisible object distance of the cylindrical grating with preset grating attribute parameters.

[0073] S240. Perform similarity analysis between the image formed by passing the object to be observed through a cylindrical grating with preset grating attribute parameters and a standard image to evaluate the stealth characteristics of the cylindrical grating with preset grating attribute parameters.

[0074] The technical solution in this embodiment of the invention details that, before calculating the theoretical critical invisible distance of an object through a cylindrical grating with preset grating attribute parameters based on the theoretical critical invisible distance formula of the cylindrical grating, it further includes: determining the ratio *m* of the width of the light spot formed after the object passes through the cylindrical grating with preset grating attribute parameters in the first direction to the width of the object in the first direction. Using the above method, a theoretical critical invisible distance formula for a cylindrical grating with preset grating attribute parameters is proposed as follows: The evaluation device provides the values ​​of each parameter in the theoretical critical invisibility distance formula. The ratio m of the width of the light spot formed by the object being observed through the cylindrical grating with preset grating attribute parameters in the first direction to the width of the object being observed in the first direction is obtained through simulation in the optical physical field. This facilitates the clear, accurate, fast and intuitive calculation of the theoretical critical invisibility distance value of the cylindrical grating with preset grating attribute parameters, which is of great guiding significance for the design and manufacture of cylindrical gratings with good optical invisibility effect.

[0075] Figure 5 This is a flowchart illustrating another method for evaluating the stealth properties of a cylindrical grating provided in this embodiment of the invention. This embodiment is an optimization based on the above embodiment. Optionally, a similarity analysis is performed between the image formed after the object to be observed passes through a cylindrical grating with preset grating attribute parameters and a standard image to evaluate the stealth properties of the cylindrical grating with preset grating attribute parameters, including:

[0076] When the similarity between the image formed after the observed object passes through a cylindrical grating with preset grating attribute parameters and the standard image meets the preset similarity range, it is determined that the theoretical critical invisible distance is reasonable.

[0077] For details not covered in this embodiment, please refer to the above embodiments. Figure 5 As shown, the evaluation method includes:

[0078] S310. Calculate the theoretical critical invisible distance of the object to be observed through the cylindrical grating with preset grating attribute parameters, based on the theoretical critical invisible distance formula of the cylindrical grating.

[0079] S320. Change the position of the object to be observed within the preset object distance range, and acquire the image formed by the object to be observed after passing through the cylindrical grating with preset grating attribute parameters in real time; wherein, the preset object distance range includes the theoretical critical invisible object distance of the cylindrical grating with preset grating attribute parameters.

[0080] S330. When the similarity between the image formed after the object to be observed passes through a cylindrical grating with preset grating attribute parameters and the standard image meets the preset similarity range, it is determined that the theoretical critical invisible distance is reasonable.

[0081] The preset similarity range is determined based on the similarity between the image formed by the observed object passing through a cylindrical grating with preset grating attribute parameters and a standard image. For example, the preset similarity range can be 0.41-0.65. Specifically, a similarity analysis is performed between the image formed by the observed object passing through the cylindrical grating with preset grating attribute parameters and the standard image. When the similarity between the image formed by the observed object passing through the cylindrical grating with preset grating attribute parameters and the standard image meets the preset similarity range, it can be determined that the theoretical critical invisibility distance is reasonable. That is, under the limitation of the theoretical critical invisibility distance of the cylindrical grating with preset grating attribute parameters, the similarity between the image formed by the observed object passing through the cylindrical grating with preset grating attribute parameters and the standard image is high. Similarly, the invisibility experiment effect of other observed objects passing through cylindrical gratings with preset grating attribute parameters can also be determined.

[0082] The technical solution in this embodiment of the invention first calculates the theoretical critical invisibility distance of the object to be observed through a cylindrical grating with preset grating attribute parameters, based on the theoretical critical invisibility distance formula of the cylindrical grating. Then, within the preset distance range, the position of the object to be observed is changed, and the image formed after the object passes through the cylindrical grating with preset grating attribute parameters is acquired in real time. The preset distance range includes the theoretical critical invisibility distance of the cylindrical grating with preset grating attribute parameters. Finally, when the similarity between the image formed after the object passes through the cylindrical grating with preset grating attribute parameters and the standard image meets a preset similarity range, the theoretical critical invisibility distance is deemed reasonable. Using this method, within a preset similarity range, the reasonableness of the theoretical critical invisibility distance value calculated according to the theoretical critical invisibility distance formula of the cylindrical grating with preset grating attribute parameters can be determined, which helps to further verify the invisibility experimental effect of the theoretical critical invisibility distance formula of the cylindrical grating with preset grating attribute parameters.

[0083] Figure 6This is a flowchart illustrating another method for evaluating the stealth properties of a cylindrical grating provided in this embodiment of the invention. This embodiment is an optimization based on the above embodiment. Optionally, a similarity analysis is performed between the image formed after the object to be observed passes through a cylindrical grating with preset grating attribute parameters and a standard image to evaluate the stealth properties of the cylindrical grating with preset grating attribute parameters, including:

[0084] Based on the similarity analysis between the image formed by the object under observation after passing through a cylindrical grating with preset grating attribute parameters and a standard image, the actual critical invisibility distance for the object under observation to become completely invisible after passing through a cylindrical grating with preset grating attribute parameters is determined.

[0085] For details not covered in this embodiment, please refer to the above embodiments. Figure 6 As shown, the evaluation method includes:

[0086] S410. Calculate the theoretical critical invisible distance of the object to be observed through the cylindrical grating with preset grating attribute parameters, based on the theoretical critical invisible distance formula of the cylindrical grating.

[0087] S420. Change the position of the object to be observed within a preset object distance range, and acquire in real time the image formed by the object to be observed after passing through the cylindrical grating with preset grating attribute parameters; wherein, the preset object distance range includes the theoretical critical invisible object distance of the cylindrical grating with preset grating attribute parameters.

[0088] S430. Based on the similarity analysis between the image formed by the object to be observed after passing through the cylindrical grating with preset grating attribute parameters and the standard image, determine the actual critical invisibility distance at which the object to be observed becomes completely invisible after passing through the cylindrical grating with preset grating attribute parameters.

[0089] It should be noted that there is a certain error between the theoretical critical invisibility distance and the actual critical invisibility distance of the cylindrical grating with preset grating attribute parameters. The theoretical critical invisibility distance and the actual critical invisibility distance may not be the same. Based on the theoretical critical invisibility distance of the cylindrical grating with preset grating attribute parameters, the range of the actual critical invisibility distance can be determined first. Then, the actual critical invisibility distance of the cylindrical grating with preset grating attribute parameters can be further accurately determined based on similarity analysis. Specifically, within the preset distance range, the relative position between the object to be observed and the cylindrical grating with preset grating attribute parameters is changed, and the image formed after the object to be observed passes through the cylindrical grating with preset grating attribute parameters is acquired in real time. A similarity analysis is also performed in real time between the image formed after the object to be observed passes through the cylindrical grating with preset grating attribute parameters and a standard image. Based on the numerical results of the similarity analysis between the image formed after the object to be observed passes through the cylindrical grating with preset grating attribute parameters and the standard image, the actual critical invisibility distance at which the object to be observed becomes completely invisible after passing through the cylindrical grating with preset grating attribute parameters can be determined.

[0090] The technical solution in this embodiment of the invention first calculates the theoretical critical invisibility distance of the object to be observed through a cylindrical grating with preset grating attribute parameters based on the theoretical critical invisibility distance formula of the cylindrical grating. Then, the position of the object to be observed is changed within the preset distance range, and the image formed after the object to be observed passes through the cylindrical grating with preset grating attribute parameters is acquired in real time. The preset distance range includes the theoretical critical invisibility distance of the cylindrical grating with preset grating attribute parameters. Finally, based on the similarity analysis between the image formed after the object to be observed passes through the cylindrical grating with preset grating attribute parameters and the standard image, the actual critical invisibility distance at which the object to be observed becomes completely invisible after passing through the cylindrical grating with preset grating attribute parameters is determined. Using the above method, under the constraint of the theoretical critical invisibility distance, the actual critical invisibility distance value after the observed object becomes completely invisible after passing through a cylindrical grating with preset grating attribute parameters is re-determined. This is beneficial for accurately determining the actual critical invisibility distance of the cylindrical grating with preset grating attribute parameters. It allows for a clear, accurate, fast, and intuitive evaluation of the invisibility characteristics of the cylindrical grating with preset grating attribute parameters, avoiding errors in the evaluation of the invisibility characteristics of the cylindrical grating with preset grating attribute parameters due to the difference between the theoretical and actual critical invisibility distances. This has important guiding significance for the design and manufacture of cylindrical gratings with better optical invisibility effects.

[0091] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A method for evaluating the hidden properties of a columnar grating, characterized by, The application comprises the following steps: According to the theoretical critical cloaked object distance formula of the columnar grating, the theoretical critical cloaked object distance of the columnar grating with the preset grating attribute parameters through which the object to be observed passes is calculated; The position of the object to be observed is changed within a preset object distance range, and the image formed after the object to be observed passes through the columnar grating with the preset grating attribute parameters is acquired in real time; wherein the preset object distance range includes the theoretical critical cloaked object distance of the columnar grating with the preset grating attribute parameters; The image formed after the object to be observed passes through the columnar grating with the preset grating attribute parameters is subjected to similarity analysis with a standard image, and the cloaking characteristics of the columnar grating with the preset grating attribute parameters are evaluated; A theoretical critical cloaking distance formula of a columnar grating with the preset grating property parameters is ; wherein r is a curvature radius of the columnar grating with the preset grating property parameters, n0 is a refractive index of the columnar grating with the preset grating property parameters, l is a line degree of the columnar grating with the preset grating property parameters, d is a width of an object to be observed in a first direction, d' is a human eye resolution, and the first direction is an array arrangement direction of the columnar grating with the preset grating property parameters. Before the step of calculating the theoretical critical cloaked object distance of the columnar grating with the preset grating attribute parameters through which the object to be observed passes according to the theoretical critical cloaked object distance formula of the columnar grating, the following step is further included: The ratio m of the width of the light spot formed after the object to be observed passes through the columnar grating with the preset grating attribute parameters to the width of the object to be observed in the first direction is determined; The ratio m of the width of the light spot formed after the object to be observed passes through the columnar grating with the preset grating attribute parameters to the width of the object to be observed in the first direction is determined, which includes the following steps: In the optical physics field, the ratio m of the preset energy ratio of the light spot formed after the object to be observed passes through the columnar grating with the preset grating attribute parameters to the width of the object to be observed in the first direction is determined.

2. The evaluation method according to claim 1, characterized in that The preset energy ratio is greater than or equal to 86.5%.

3. The evaluation method according to claim 1, characterized in that The image formed after the object to be observed passes through the columnar grating with the preset grating attribute parameters is subjected to similarity analysis with a standard image, and the cloaking characteristics of the columnar grating with the preset grating attribute parameters are evaluated, which includes the following steps: When the similarity of the image formed after the object to be observed passes through the columnar grating with the preset grating attribute parameters and the standard image meets the preset similarity range, it is determined that the theoretical critical cloaked object distance is reasonable.

4. The evaluation method according to claim 1, characterized in that The image formed after the object to be observed passes through the columnar grating with the preset grating attribute parameters is subjected to similarity analysis with a standard image, and the cloaking characteristics of the columnar grating with the preset grating attribute parameters are evaluated, which includes the following steps: According to the similarity analysis of the image formed after the object to be observed passes through the columnar grating with the preset grating attribute parameters and the standard image, the actual critical cloaked object distance at which the object to be observed is completely cloaked after passing through the columnar grating with the preset grating attribute parameters is determined.

5. An apparatus for evaluating the hidden characteristics of an object using the moire properties of a columnar grating, characterized by, The evaluation device for performing the cloaking characteristic evaluation method of the columnar grating as claimed in any one of claims 1-4 comprises: An object to be observed; A columnar grating with preset grating attribute parameters; A camera module, which is located on the side of the columnar grating with the preset grating attribute parameters away from the object to be observed, and is used to acquire the image formed after the object to be observed passes through the columnar grating with the preset grating attribute parameters in real time when the position of the object to be observed is changed within a preset object distance range; wherein the preset object distance range includes the theoretical critical cloaked object distance of the columnar grating with the preset grating attribute parameters. A computer module is configured to perform similarity analysis between an image formed by the object to be observed after passing through the columnar grating with the preset grating attribute parameter and a standard image, and to evaluate the invisible characteristics of the columnar grating with the preset grating attribute parameter.

6. The evaluation device according to claim 5, characterized in that A stepper motor module is further included to automatically adjust the relative position between the object to be observed and the columnar grating with the preset grating attribute parameter.

7. The evaluation device according to claim 5, characterized in that A background whiteboard is further included, which is located on the side of the object to be observed away from the columnar grating with the preset grating attribute parameter.

8. The evaluation device according to claim 5, characterized in that A base is further included, which comprises a fixing and adjusting unit and a scale line unit, wherein the fixing and adjusting unit is configured to fix and / or adjust the positions of the object to be observed, the columnar grating with the preset grating attribute parameter, and the camera module, and the scale line unit is configured to measure the distance between the object to be observed, the columnar grating with the preset grating attribute parameter, and the camera module.

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