CN114660828B - Aerial display simulation imaging system and method for testing performance of retroreflective material - Google Patents
Aerial display simulation imaging system and method for testing performance of retroreflective material Download PDFInfo
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Abstract
The application discloses a display simulation imaging system, a test method for the performance of a retroreflective material and an optimization method for the structure of the retroreflective material, wherein the aerial display simulation imaging system is used for testing the performance of a retroreflective product made of the retroreflective material and comprises a semi-transparent half mirror, a detector and a display screen, the retroreflective product and the detector are respectively arranged on two sides of the semi-transparent half mirror, an original image displayed on the display screen emits light rays which are reflected by the semi-transparent half mirror and then reach the retroreflective product, the light rays reflected by the retroreflective product are transmitted again by the semi-transparent half mirror and then reach the detector to image on the detector, and the performance of the retroreflective product is judged according to the imaging definition on the detector and/or the luminous flux received by the detector. The application can test and evaluate the performance of the retroreflective material in the design stage, and has important significance for laying foundation for post-manufacturing and system construction.
Description
Technical Field
The application relates to the technical field of medium-free air display, in particular to an air display simulation imaging system based on ray tracing simulation, a test method of the performance of a retroreflective material and an optimization method of a retroreflective material structure.
Background
The medium-free air display is a naked eye 3D image visual system without a carrier, a medium and a screen, can bring 3D experience with the most immersion and reality to the audience, and has wide application prospect in the fields of engineering, scientific research, medical treatment, education, media, video entertainment and the like. Related technologies for realizing medium-free air display include negative refractive index imaging glass technology, ionization technology, multi-lens imaging technology, retroreflective material imaging technology and the like, wherein the retroreflective material imaging technology has better brightness, definition and visible range, lower realization cost and better development prospect.
The retroreflective material is a material capable of returning reflected light rays in a direction close to the opposite direction of incident light rays, and is generally composed of a layer of thin and continuous transparent tiny glass beads or cube corner elements (prisms), wherein the incident light rays are subjected to twice refraction and once reflection in the glass beads or are returned in the opposite direction of the incident direction after being subjected to tertiary reflection in the microprisms to form retroreflection, and a 3D real image can be formed in the air after passing through a specific optical system, so that dielectric-free air display is realized. The retroreflection efficiency is an important performance index of the retroreflection material, the retroreflection efficiency is defined as the ratio of light energy incident on the retroreflection material to reflected light energy, the improvement of the retroreflection efficiency of the retroreflection material means that stray light is less in the imaging process, the definition of the aerial display is improved, the light energy loss after passing through the optical system is less, the brightness of the aerial display is improved, and the performance of the retroreflection material has decisive influence on the imaging effect of the aerial display system. Therefore, how to test and evaluate the performance of the retroreflective material in the design stage has important significance for laying foundation for post-manufacturing and system construction.
The foregoing background is only for the purpose of facilitating an understanding of the principles and concepts of the application and is not necessarily in the prior art to the present application and is not intended to be used as an admission that such background is not entitled to antedate such novelty and creativity by virtue of prior application or that it is already disclosed at the date of filing of this application.
Disclosure of Invention
In order to solve the technical problems, the application provides an air display simulation imaging system based on ray tracing simulation, a test method for the performance of a retroreflective material and an optimization method for the structure of the retroreflective material, which can test and evaluate the performance of the retroreflective material in a design stage and has important significance for laying a foundation for post-manufacturing and system construction.
In order to achieve the above purpose, the present application adopts the following technical scheme:
the application discloses an aerial display simulation imaging system which is used for testing the performance of a retroreflective product made of retroreflective materials, and comprises a semi-transparent half mirror, a detector and a display screen, wherein the retroreflective product and the detector are respectively arranged on two sides of the semi-transparent half mirror, original image emitted light rays displayed on the display screen reach the retroreflective product after being reflected by the semi-transparent half mirror, and the light rays reflected by the retroreflective product reach the detector after being transmitted again by the semi-transparent half mirror so as to image on the detector, and the performance of the retroreflective product is judged according to the imaging definition on the detector and/or the luminous flux received by the detector.
The second aspect of the application discloses a method for testing the performance of a retroreflective material, which comprises the following steps of A1: the performance of retroreflective articles made of retroreflective materials was tested using the above-described aerial display simulated imaging system.
Preferably, in step A1, the sharpness of the image on the detector is analyzed to determine the performance of the retroreflective article using a peak signal-to-noise ratio, where the peak signal-to-noise ratio is expressed as:
where MSE represents the mean square error, MAX, between the original image x displayed on the display screen and the imaging result y on the detector I Representing the maximum pixel value possible in the picture.
Preferably, in step A1, structural similarity is used to analyze the sharpness of the image on the detector to determine the performance of the retroreflective article, where the structural similarity is expressed as:
wherein mu is x Is the mean value, mu, of the original image x displayed on the display screen y Sigma, which is the mean value of the imaging result y on the detector x Standard deviation of original image x, sigma y For the standard deviation of the imaging result y, σ xy C is the covariance between the original image x and the imaging result y 1 And C 2 Is a regularized constant.
Preferably, the test method further comprises step A2: incident light is incident to the retroreflective article at a predetermined angle of incidence, and the retroreflective efficiency of the retroreflective article is determined based on the ratio of the effective incident area to the light passing area of the retroreflective article.
Preferably, step A2 specifically includes:
a21: a retroreflective product made of retroreflective material formed by pyramid arrays is placed in a rectangular coordinate system, the vertex of any one pyramid unit in the retroreflective product is positioned at the origin O of the rectangular coordinate system, and three points on the bottom surface are A, B, C respectively;
a22: symmetrically establishing a virtual pyramid unit with the origin point of the pyramid unit corresponding to the retroreflective article in the step A21, wherein the vertex of the virtual pyramid unit is positioned at the origin point O of a rectangular coordinate system, and three points of the bottom surface are A1, B1 and C1 respectively;
a23: the method comprises the steps of (1) incidence of an incident ray R to a pyramid bottom surface ABC of a pyramid unit at a preset incidence angle, and projection of an integral shape formed by three triangular side surfaces of the pyramid unit to a plane taking the incident ray R as a normal line to obtain a first triangle;
a24: the pyramid unit completes the retroreflection so that the extension line of the incident light ray R passes through the virtual pyramid unit, and the integral shape formed by three triangular side faces of the virtual pyramid unit is projected onto a plane taking the incident light ray R as a normal to obtain a second triangle;
a25: the retroreflective efficiency of the retroreflective article is determined from the ratio of the effective entrance area, which is the area of the overlapping area of the first triangle and the second triangle, to the light passing area of the retroreflective article, which is the area of the first triangle.
Further, the effective incident area and the light passing surface of the retroreflective article are estimated by using a Monte Carlo method respectively.
The third aspect of the application discloses a method for optimizing the structure of a retroreflective material, comprising:
b1: the bottom side length of pyramid units in a retroreflective product made of retroreflective materials formed by pyramid arrays is kept unchanged, retroreflective products made of various retroreflective material structures corresponding to different edge angles are respectively tested by the aerial display simulation imaging system to obtain luminous flux received by the detector when the corresponding retroreflective product is used for imaging, and therefore the optimized edge angles of the pyramid units in the pyramid arrays in the retroreflective material for manufacturing the retroreflective product are obtained.
Preferably, the optimizing method further comprises:
b2: the included angle of edges in pyramid units in the retroreflective product is kept unchanged, retroreflective products made of various retroreflective material structures corresponding to different bottom edge lengths are tested by adopting the testing method step A1, so that the imaging definition on the detector when the corresponding retroreflective product is used for imaging is obtained, and the optimized bottom edge length of the pyramid units in the pyramid array in the retroreflective material for manufacturing the retroreflective product is obtained;
b3: and C, keeping the bottom edge length of the pyramid units in the retroreflective product unchanged, and testing the retroreflective product made of a plurality of retroreflective material structures corresponding to different edge angles by adopting the testing method step A1 to obtain the imaging definition on the detector when the corresponding retroreflective product is used for imaging, so as to obtain the optimized edge angle of the pyramid units in the pyramid array in the retroreflective material for manufacturing the retroreflective product.
Preferably, the optimizing method further comprises:
b4: and (2) making incident light rays enter the retroreflective article at different incident angles, and measuring the corresponding retroreflective efficiency of the retroreflective article according to the test method step A2 so as to obtain the optimized incident angle of the retroreflective article.
Preferably, the optimizing method further comprises:
b5: and C, keeping the side length and the edge included angle of the pyramid bottom edge in the pyramid units in the retroreflective product unchanged, and then respectively measuring the retroreflective efficiency of the retroreflective product by adopting the test method step A2 corresponding to the retroreflective products made of a plurality of retroreflective material structures corresponding to different edge rounded angles so as to obtain the optimized edge rounded angles of the pyramid units in the pyramid array in the retroreflective material for manufacturing the retroreflective product.
Compared with the prior art, the application has the beneficial effects that: the application provides an aerial display simulation imaging system based on ray trace simulation, through which performance test of a retroreflective material can be performed in a virtual environment by using ray trace, a specific corresponding relation exists between a test result and a structural design, and a corresponding change trend of the test result when structural parameters change can be obtained, so that blindness in an iterative optimization process is avoided, and the efficiency of product design is improved.
In a further aspect, it is proposed to use peak signal-to-noise ratio and structural similarity to evaluate imaging performance of retroreflective material, providing a quantitative evaluation index for the effect of retroreflective material in an imaging system; PSNR and SSIM of the retroreflective materials with different structural parameters can be obtained according to an aerial display simulation imaging system, and the change trend of the indexes along with the change of key structural parameters can be observed to obtain the structural optimization direction of the retroreflective materials; the higher the PSNR and SSIM values, the better the imaging performance of the retroreflective material, i.e., the closer the imaged and the better the sharpness to the original image. Furthermore, the principle of geometrical optics is combined with the Monte Carlo method to test the retroreflection efficiency of the retroreflection material, so that the method has the advantages of simplicity, intuitiveness and easiness in operation.
Furthermore, for unavoidable errors or flaws in the processing process of the retroreflective material, the testing method and the optimizing method provided by the application can analyze the influence degree of the errors and find the influence rule of the processing errors on the retroreflective performance, thereby having great significance for guiding the actual production of the retroreflective material and improving the yield of finished products.
Drawings
FIG. 1a is a schematic illustration of an aerial display simulation imaging system based on ray trace simulation in accordance with a preferred embodiment of the present application;
FIG. 1b is a schematic view of light rays emitted from a display screen in the aerial display simulation imaging system of FIG. 1 a;
FIG. 2a is a schematic diagram of pyramid units in retroreflective articles and correspondingly created virtual pyramid units in a rectangular coordinate system;
FIG. 2b is a schematic view showing the projection of the entire shape of three triangular sides of each of the pyramid unit and the virtual pyramid unit of FIG. 2a, after the incident light ray is incident on the pyramid unit, onto a plane normal to the incident light ray;
FIG. 3 is a schematic view of the structural parameters of a pyramid unit in a retroreflective article;
FIG. 4 is a graph of the received light flux from a detector when imaging retroreflective articles made of multiple retroreflective material structures corresponding to different edge angles when light is normally incident to a pyramid array;
FIG. 5a is a PSNR imaged on a detector when a retroreflective article made of a plurality of retroreflective material structures corresponding to different bottom edge lengths is imaged;
FIG. 5b is an imaged SSIM on a detector when a retroreflective article made of a plurality of retroreflective material structures having different bottom edge lengths is imaged;
FIG. 6a is a PSNR imaged on a detector when a retroreflective article made of a plurality of retroreflective material structures corresponding to different edge angles is imaged;
FIG. 6b is an SSIM imaged on a detector when a retroreflective article made of a plurality of retroreflective material structures corresponding to different edge angles is imaged;
FIG. 7 is a graph showing the change in retroreflection efficiency of a corresponding retroreflective article when different angles of incidence are incident to the bottom surface of a cube corner element, with an included edge angle of 90;
FIG. 8a is a schematic cross-sectional view of a retroreflective material formed from an array of pyramids;
FIG. 8b is a top view of a pyramid array of retroreflective material in an ideal state;
FIG. 8c is a top view of a pyramid array of retroreflective material with edge fillets;
FIG. 9a is a graph of illuminance when the radius of the edge fillet is 0% of the bottom side length;
FIG. 9b is a graph of illuminance when the radius of the edge fillet is 1% of the bottom edge length;
FIG. 9c is a graph of illuminance when the radius of the edge fillet is 3% of the bottom side length;
FIG. 9d is a graph of illuminance when the radius of the edge fillet is 5% of the bottom edge length;
FIG. 10 is a graph of the light flux received by a detector when imaging retroreflective articles made from a plurality of retroreflective material structures corresponding to different edge fillet radii.
Detailed Description
The following describes embodiments of the present application in detail. It should be emphasized that the following description is merely exemplary in nature and is in no way intended to limit the scope of the application or its applications.
It will be understood that when an element is referred to as being "mounted" or "disposed" on another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element. In addition, the connection may be for both the fixing action and the circuit/signal communication action.
It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are merely for convenience in describing embodiments of the application and to simplify the description by referring to the figures, rather than to indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be construed as limiting the application.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the embodiments of the present application, the meaning of "plurality" is two or more, unless explicitly defined otherwise.
The traditional retroreflective material research and development path is through design, production, test three links, the traditional test method is too high to process quality, instrument and experimental condition requirement of the sample, the test effect can't feedback and instruct the design of the retroreflective material well, have blindness, in addition, traditional test method can only evaluate the retroreflective efficiency of the retroreflective material, can't carry on the objective evaluation to its imaging performance, can't carry on the quantitative analysis to the error that appears in the manufacturing process too.
The application is based on the realization principle of the imaging technology of the retroreflective material, applies a ray tracing method to carry out imaging simulation on an air display system based on the retroreflective material, combines image quality evaluation indexes and related optical parameters to objectively evaluate imaging effects and performance of the retroreflective material, analyzes influence of processing errors possibly occurring in the processing process on imaging quality, and further optimizes basic structure parameter design of the retroreflective material.
As shown in fig. 1a, a preferred embodiment of the present application discloses an air display simulation imaging system based on ray tracing simulation, which is used for testing the performance of a retroreflective article 10 made of retroreflective material, and comprises a half mirror 20, a detector 30 and a display screen 40, wherein the retroreflective article 10 and the detector 30 are respectively arranged at two sides of the half mirror 20, as shown in fig. 1b, an original image displayed on the display screen 40 emits collimated light, which is reflected by the half mirror 20, to reach the retroreflective article 10, and the light reflected by the retroreflective article 10 is transmitted again by the half mirror 20 and then reaches the detector 30 to image on the detector 30, and the performance of the retroreflective article 10 is determined according to the definition of the image on the detector 30 and/or the luminous flux received by the detector 30.
The aerial display simulation imaging system can be established in optical simulation software, and the light path characteristics of the aerial display simulation imaging system can be further analyzed according to the system structure. In the aerial display simulation imaging system, a picture is displayed through the display screen 40 and corresponds to a "real image", the light is emitted by the display screen 40, the light can be considered to be collimated light during simulation, the collimated light emitted by the "real image" passes through the semi-transparent mirror 20 and then reaches the retroreflective article 10 (for example, can be a retroreflective film), and then the light after being retroreflected by the retroreflective article 10 passes through the semi-transparent mirror 20 again and then reaches the detector 30 for imaging.
The preferred embodiment of the application also discloses a method for testing the performance of the retroreflective material, which comprises the following steps:
a1: the performance of retroreflective articles made of retroreflective materials was tested using the above-described aerial display simulated imaging system.
Specifically, the imaging sharpness of the above-described aerial display imaging system is analyzed in terms of peak signal-to-noise ratio and structural similarity.
The expression of the peak signal-to-noise ratio is shown in the formula (1).
Where MSE represents the original image x (original image displayed on display 40) andmean square error, MAX, between imaging results y (imaging results at detector 30) I The picture is represented (the picture refers to the image in a computer, namely the data format, and does not refer to a certain picture, and the difference between the imaging result and the original picture is mainly represented by MSE, MAX I Taking different constants according to different picture data formats); in this embodiment, if the picture pixel is unit8 data, MAX I 255, MAX if the picture pixel is in float format I 1.
PSNR is the most widely used objective index for evaluating image quality, but the value of PSNR often cannot be completely consistent with the visual quality evaluation of an image by human eyes, and for this reason, structural similarity is also adopted as an auxiliary evaluation means in this embodiment.
Wherein the expression of the structural similarity is shown in the formula (2).
Wherein mu is x Mu, which is the mean value of the original image x y Sigma, the mean value of the imaging result y x Standard deviation of original image x, sigma y For the standard deviation of the imaging result y, σ xy C is the covariance between the original image x and the imaging result y 1 And C 2 To regularize the constants to avoid zero-division, in this embodiment, C 1 ＝[0.01(2 n -1)] 2 ，C 2 ＝[0.03(2 n -1)] 2 N represents that each pixel is represented by an n-bit binary number.
The SSIM ranges between [ -1,1], indicating that the original image x is exactly the same as the imaging result y when ssim=1.
A2: incident light is incident to the retroreflective article at a predetermined incident angle, and the retroreflective efficiency of the retroreflective article is determined based on the ratio of the effective incident area to the light passing area of the retroreflective article.
The step A2 specifically comprises the following steps:
a21: as shown in fig. 2a, a retroreflective article made of retroreflective material formed by using a pyramid array is placed in a rectangular coordinate system O-xyz, and the vertex of any one pyramid unit in the retroreflective article is located at the origin O of the rectangular coordinate system, and three points on the bottom are A, B, C respectively;
a22: symmetrically establishing a virtual pyramid unit by using the corresponding pyramid unit of the retroreflective article in the step A21 as an origin, wherein the vertex of the virtual pyramid unit is positioned at the origin O of a rectangular coordinate system, and three points of the bottom surface are A1, B1 and C1 respectively;
a23: the incident light ray R is incident to the pyramid bottom surface ABC of the pyramid unit at a preset incident angle, the integral shape formed by three triangular side surfaces (OAC, OBC and OAB) of the pyramid unit is projected onto a plane taking the incident light ray R as a normal line to obtain a first triangle ABC, as shown in fig. 2B, wherein the luminous flux in the area of the first triangle ABC is the luminous flux incident to the pyramid unit, the necessary condition for finishing the retroreflection is that primary reflection is finished on all three triangular side surfaces, and the extension line equivalent to the incident light ray R passes through the virtual pyramid unit OA1B1C1 according to the law of reflection;
a24: the pyramid unit completes the retroreflection so that the extension line of the incident ray R passes through the virtual pyramid unit, and the whole shape formed by three triangular side faces (OA 1C1, OB1C1 and OA1B 1) of the virtual pyramid unit is projected onto a plane taking the incident ray R as a normal line to obtain a second triangle a1B1C1;
a25: the retroreflective efficiency of the retroreflective article is determined according to the ratio of the effective incident area to the light passing area of the retroreflective article, wherein the effective incident area is the area of the overlapping area of the first triangle abc and the second triangle a1b1c1, and the light passing area of the retroreflective article is the area of the first triangle abc.
As shown in fig. 2b, the overlapping area of the first triangle abc and the second triangle a1b1c1 is an effective incident area for retroreflection, when light is incident on the retroreflective material, only the light entering the effective area for retroreflection can complete retroreflection, the ratio of the area to the projected area of the triangle can be defined as the retroreflection efficiency of the pyramid unit, the retroreflection efficiency can be estimated by using the monte carlo method, that is, points are uniformly distributed randomly in the projected area, and the ratio of the number of points located in the shadow area to the total number of points can be regarded as the ratio of the areas of the two points.
The preferred embodiment of the application additionally discloses an optimization method of the structure of the retroreflective material, which comprises the following steps:
b1: the method comprises the steps of keeping the side length of the pyramid bottom edge in pyramid units in a retroreflective product made of retroreflective materials formed by adopting a pyramid array to be a first length, respectively testing retroreflective products made of various retroreflective material structures corresponding to different edge angles by adopting an air display simulation imaging system shown in figure 1 to obtain luminous flux received by a detector when the corresponding retroreflective product is used for imaging, so as to obtain the optimized edge angle of the pyramid units in the pyramid array in the retroreflective material for manufacturing the retroreflective product.
The pyramid array is a common structure of retroreflective material, and the incident light rays in the retroreflective effective area are reflected on three sides of the pyramid and then exit reversely along the incident direction, and the rest of the light rays are called scattered light due to insufficient reflection times in the pyramid units. As shown in fig. 3, the structural parameters of the pyramid units in the pyramid array include a bottom side length L, an edge included angle α, and the like, wherein the bottom surface ABC of the pyramid units is a regular triangle, the projection of the vertex O on the bottom surface ABC is located at the geometric center of the bottom surface, the bottom side length ab=bc=ac, and the edge included angle aoc= aob= BOC.
When light is normally incident to the pyramid array, the luminous flux received by the detector is compared when different edge angles are imaged, and the result is shown in fig. 4, and it can be seen from the graph that the imaging performance of the retroreflective material is best when the edge angle is 90 degrees.
B2: the method comprises the steps of (1) testing retroreflective products made of various retroreflective material structures corresponding to different bottom edge lengths respectively by keeping the included angle of edges in pyramid units in retroreflective products unchanged to obtain images with different imaging definition so as to obtain optimized pyramid bottom edge lengths of pyramid units in pyramid arrays in retroreflective materials made of retroreflective products;
in this example, the bottom edge length is set as shown in table 1 while keeping the edge angle at 90 °.
TABLE 1 bottom side Length of pyramid unit
The scale of pyramid arrays with different basic parameters is 4mm multiplied by 4mm, the pyramid arrays are positioned at the same spatial position, the number of trace rays is 300 ten thousand, the evaluation indexes are PSNR and SSIM, and the results are shown in fig. 5a and 5 b. From the simulation results, it can be seen that the smaller the bottom side length of the pyramid units, the higher the imaging definition of the retroreflective article made of retroreflective material.
B3: and C, keeping the side length of the pyramid bottom edge in the pyramid unit in the retroreflective product unchanged, and then testing the retroreflective product made of a plurality of retroreflective material structures corresponding to different edge angles by adopting the testing method of the step A1 to obtain images with different imaging definition so as to obtain the optimized edge angle of the pyramid unit in the pyramid array in the retroreflective material for making the retroreflective product.
In this example, the edge angle is set as shown in Table 2 while keeping the bottom edge length at 100. Mu.m.
Table 2 corner angles of corner cube units
The scale of pyramid arrays with different basic parameters is 4mm multiplied by 4mm, the pyramid arrays are positioned at the same spatial position, the number of trace rays is 300 ten thousand, the evaluation indexes are PSNR and SSIM, and the results are shown in fig. 6a and 6 b. The imaging definition and the imaging brightness are comprehensively considered, and the imaging performance of the retroreflective material is best when the edge included angle is 90 degrees.
The above steps B1 to B3 analyze the influence of the structural parameters of the pyramid units on the imaging effect, and can guide the optimization of the basic structural parameter design of the retroreflective material accordingly.
B4: and (2) making the incident light rays enter the retroreflective article at different incident angles, and measuring the retroreflective efficiency of the retroreflective article according to the test method in the step (A2) so as to obtain the optimized incident angle of the retroreflective article.
In the case where the edge angle is 90 °, the incident angle of the bottom ray incident on the pyramid unit is changed, and the change in retroreflection efficiency is calculated using the monte carlo method, and the result is shown in fig. 7. As can be seen from the figure, the retroreflective efficiency decreases with increasing incidence angle, the retroreflective rate decreases to zero when the incidence angle is greater than 40 degrees, and the retroreflective rate is 30% or more when the incidence angle is less than 25 degrees.
And B4, analyzing the influence of the incident angle of the light on the retroreflection efficiency, and guiding the actual application scene of the retroreflection product accordingly.
B5: and (3) keeping the side length and the edge included angle of the pyramid bottom edge in the pyramid units in the retroreflective product unchanged, and then respectively measuring the retroreflective efficiency of the corresponding retroreflective product by using the test method in the step A2 on retroreflective products made of various retroreflective material structures corresponding to different edge rounded angles so as to obtain the optimized edge included angle of the pyramid units in the pyramid array in the retroreflective material for manufacturing the retroreflective product.
Machining errors may occur in the machining of retroreflective materials, such as machining errors in edge rounding, substrate thickness, etc. may occur in the machining of retroreflective films comprising pyramid arrays. As shown in fig. 8a, a schematic cross-sectional view of a retroreflective material comprising an array of pyramids, in which a processing error of the substrate thickness 100 may exist, as shown in fig. 8b, a top view of the array of pyramids of retroreflective material in an ideal state, and as shown in fig. 8c, a top view of the array of pyramids of retroreflective material with edge rounded corners 200. The degree of influence on the properties of the retroreflective material in the presence of edge rounding is analyzed and evaluated as follows.
Considering that machining may result in edge fillet formation, its effect on retroreflection performance was simulated. The bottom side length of the pyramid is set to be 100 micrometers, the radius of the edge fillet is set to be 1 micrometer, 3 micrometers and 5 micrometers respectively, and simulation results are shown in fig. 9a to 9d, wherein fig. 9a is an illuminance map when the radius of the edge fillet is 0% of the bottom side length, fig. 9b is an illuminance map when the radius of the edge fillet is 1% of the bottom side length, fig. 9c is an illuminance map when the radius of the edge fillet is 3% of the bottom side length, and fig. 9d is an illuminance map when the radius of the edge fillet is 5% of the bottom side length. It can be seen from fig. 9a to 9d that the light incident on the edge fillet area cannot be retroreflected, resulting in loss of light energy, and the larger the fillet radius, the larger the light energy loss, affecting the light flux received by the detector, as shown in fig. 10.
Step B5 analyzes the effect of processing errors on the retroreflective efficiency, and may further optimize the design of the base structure parameters of the retroreflective material accordingly.
In the preferred embodiment of the application, an aerial display simulation imaging system based on a retroreflective material is designed; in the application field of the traditional retroreflective material (such as road traffic sign), the evaluation index of the retroreflective material is mainly retroreflective efficiency, and no direct connection exists between the retroreflective efficiency and imaging definition; the imaging definition is an important index of the air display effect and is closely related to structural parameters of the retroreflective material, so that the retroreflective material is evaluated for the retroreflective material applied to the field of air display imaging, and the structure of the retroreflective material is optimized according to an evaluation result, so that peak signal-to-noise ratio and structural similarity in the field of image processing are further introduced as quantitative evaluation indexes of the definition of the air display imaging quality, and the imaging performance of the retroreflective material can be quantitatively evaluated to guide and improve the imaging effect of an air display system; in addition, the ratio of the effective incident area to the light transmission area of the retroreflective material is used to determine the retroreflective efficiency; and also analyzes machining errors that may occur during machining and controls a reasonable range of machining errors to minimize the impact on the performance of the retroreflective material.
The method for testing and evaluating the retroreflective material based on the ray tracing simulation has the following advantages:
(1) And (5) efficient design. The traditional retroreflection material design method which follows the design, processing and testing flow is very sensitive to the material processing quality, instruments, testing environment and the like, and the testing result cannot guide the design well. According to the preferred embodiment of the application, the performance test of the retroreflective material is carried out in the virtual environment by using the optical trace, the test result has a clear corresponding relation with the structural design, and the corresponding change trend of the test result when the structural parameter is changed can be obtained, so that blindness in the iterative optimization process is avoided, and the efficiency of the product design is improved.
(2) And (5) comprehensively evaluating. The conventional test method of the retroreflective material mainly has the evaluation index of retroreflective efficiency, which is far from enough for aerial display imaging by using the retroreflective material, and the preferred embodiment of the application provides the use of peak signal-to-noise ratio and structural similarity to evaluate the imaging performance of the retroreflective material and provide a quantitative evaluation index for the effect of the retroreflective material in an imaging system. PSNR and SSIM of the retroreflective material with different structural parameters are obtained through simulation, and the change trend of the indexes along with the change of key structural parameters is observed, so that the direction of structural optimization of the retroreflective material can be obtained; the higher the PSNR and SSIM values, the better the imaging performance of the retroreflective material, i.e., the closer the imaged and the better the sharpness to the original image. In addition, the principle of geometrical optics is adopted to test the retroreflection efficiency of the retroreflection material by using the Monte Carlo method, and the method has the advantages of simplicity, intuitiveness and easiness in operation.
(3) And (5) quality control. For unavoidable errors or flaws in the processing process of the retroreflective material, the preferred embodiment of the application can analyze the influence degree of the errors and find the influence rule of the processing errors on the retroreflective performance, thereby having important significance for guiding the actual production of the retroreflective material and improving the yield of finished products.
The background section of the present application may contain background information about the problem or environment of the present application rather than the prior art described by others. Accordingly, inclusion in the background section is not an admission of prior art by the applicant.
The foregoing is a further detailed description of the application in connection with specific/preferred embodiments, and it is not intended that the application be limited to such description. It will be apparent to those skilled in the art that several alternatives or modifications can be made to the described embodiments without departing from the spirit of the application, and these alternatives or modifications should be considered to be within the scope of the application. In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction. Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope as defined by the appended claims.
Claims (7)
1. A method for testing the performance of a retroreflective material, comprising:
step A1: the performance of a retroreflective product made of retroreflective material is tested by adopting an air display simulation imaging system, wherein the air display simulation imaging system is used for testing the performance of the retroreflective product made of retroreflective material and comprises a semi-transparent half mirror, a detector and a display screen, wherein the retroreflective product and the detector are respectively arranged at two sides of the semi-transparent half mirror, an original image displayed on the display screen emits light which is reflected by the semi-transparent half mirror and then reaches the retroreflective product, and the light reflected by the retroreflective product is transmitted by the semi-transparent half mirror again and then reaches the detector so as to be imaged on the detector, and the performance of the retroreflective product is judged according to the imaging definition on the detector and/or the luminous flux received by the detector;
step A2: incident light is incident to the retroreflective article at a preset incident angle, and the retroreflective efficiency of the retroreflective article is determined according to the ratio of the effective incident area to the light passing area of the retroreflective article;
the step A2 specifically includes:
a21: a retroreflective product made of retroreflective material formed by pyramid arrays is placed in a rectangular coordinate system, the vertex of any one pyramid unit in the retroreflective product is positioned at the origin O of the rectangular coordinate system, and three points on the bottom surface are A, B, C respectively;
a22: symmetrically establishing a virtual pyramid unit with the origin point of the pyramid unit corresponding to the retroreflective article in the step A21, wherein the vertex of the virtual pyramid unit is positioned at the origin point O of a rectangular coordinate system, and three points of the bottom surface are A1, B1 and C1 respectively;
a23: the method comprises the steps of (1) incidence of an incident ray R to a pyramid bottom surface ABC of a pyramid unit at a preset incidence angle, and projection of an integral shape formed by three triangular side surfaces of the pyramid unit to a plane taking the incident ray R as a normal line to obtain a first triangle;
a24: the pyramid unit completes the retroreflection so that the extension line of the incident light ray R passes through the virtual pyramid unit, and the integral shape formed by three triangular side faces of the virtual pyramid unit is projected onto a plane taking the incident light ray R as a normal to obtain a second triangle;
a25: the retroreflective efficiency of the retroreflective article is determined from the ratio of the effective entrance area, which is the area of the overlapping area of the first triangle and the second triangle, to the light passing area of the retroreflective article, which is the area of the first triangle.
2. The method of claim 1, wherein the sharpness of the image on the detector is analyzed in step A1 using a peak signal-to-noise ratio to determine the performance of the retroreflective article, wherein the peak signal-to-noise ratio is expressed as:
where MSE represents the mean square error, MAX, between the original image x displayed on the display screen and the imaging result y on the detector I Representing the maximum pixel value possible in the picture.
3. The method of claim 1 or 2, wherein structural similarity is used in step A1 to analyze the sharpness of the image on the detector to determine the performance of the retroreflective article, wherein the structural similarity is expressed as:
wherein mu is x Is the mean value, mu, of the original image x displayed on the display screen y Sigma, which is the mean value of the imaging result y on the detector x Standard deviation of original image x, sigma y For the standard deviation of the imaging result y, σ xy C is the covariance between the original image x and the imaging result y 1 And C 2 Is a regularized constant.
4. The method of claim 1, wherein the effective entrance area and the light-passing surface of the retroreflective article are each estimated using a monte carlo method.
5. A method of optimizing a retroreflective material structure comprising:
b1: the method comprises the steps of (1) keeping the bottom side length of pyramid units in a retroreflective product made of retroreflective materials formed by a pyramid array unchanged, and respectively testing retroreflective products made of various retroreflective material structures corresponding to different edge angles by adopting an aerial display simulation imaging system to obtain luminous fluxes received by a detector when the corresponding retroreflective product is used for imaging so as to obtain optimized edge angles of the pyramid units in the pyramid array in the retroreflective material for manufacturing the retroreflective product; the aerial display simulation imaging system is used for testing the performance of a retroreflective product made of retroreflective materials and comprises a semi-transparent half mirror, a detector and a display screen, wherein the retroreflective product and the detector are respectively arranged on two sides of the semi-transparent half mirror, original image emitted light rays displayed on the display screen reach the retroreflective product after being reflected by the semi-transparent half mirror, and the light rays reflected by the retroreflective product reach the detector after being transmitted by the semi-transparent half mirror again so as to image on the detector, and the performance of the retroreflective product is judged according to the imaging definition on the detector and/or the luminous flux received by the detector;
b4: incident light rays are incident on the retroreflective article at different angles of incidence and the retroreflective efficiency of the corresponding retroreflective article is measured according to the test method of any one of claims 1 to 4 to obtain an optimized angle of incidence of the retroreflective article.
6. The optimization method according to claim 5, further comprising:
b2: maintaining the included angle of edges in pyramid units in the retroreflective article unchanged, and testing retroreflective articles made of various retroreflective material structures corresponding to different bottom edge lengths by the testing method according to any one of claims 1 to 4 to obtain the imaging definition on the detector when the corresponding retroreflective article is used for imaging, so as to obtain the optimized bottom edge length of pyramid units in the pyramid array in retroreflective material for making the retroreflective article;
b3: the bottom side length of pyramid units in the retroreflective article is kept unchanged, retroreflective articles made of a plurality of retroreflective material structures corresponding to different edge angles are tested by the testing method according to any one of claims 1 to 4, respectively, so as to obtain the definition of imaging on the detector when the corresponding retroreflective article is used for imaging, and obtain the optimized edge angle of pyramid units in the pyramid array in the retroreflective material for manufacturing the retroreflective article.
7. The optimization method according to claim 5, further comprising:
b5: and respectively measuring the retroreflection efficiency of the corresponding retroreflection product by adopting the test method of any one of claims 1 to 4 on the retroreflection product made of various retroreflection material structures corresponding to different edge fillets so as to obtain the optimized edge fillets of the pyramid units in the pyramid array in the retroreflection material for manufacturing the retroreflection product.
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