CN112050741A - Method for measuring period length of periodic grid array - Google Patents
Method for measuring period length of periodic grid array Download PDFInfo
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Abstract
The invention discloses a measuring method for measuring a periodic grid array in a periodic array structure, which comprises the following steps: acquiring an image of the periodic array structure and acquiring a pixel pitch value of the image; drawing a measurement line covering a plurality of the periodic grid arrays on the image; determining coordinate values and image characteristic values of at least a part of pixels on the measuring line and the slope of the measuring line; calculating the spatial circular frequency of the measuring line by using the coordinate value and the image characteristic value and using a fitting function; calculating the periodic length of the measuring line in the extending direction of the measuring line by using the pixel pitch value and the spatial circle frequency; and calculating an actual period length of the periodic grid array based on the slope of the measurement line and the measurement line period length.
Description
Technical Field
The present invention relates to a measuring method, and more particularly, to a measuring method of a period length of a periodic grid array in a device having a periodic array structure.
Background
In the preceding processing of devices having a periodic array structure, such as surface acoustic wave filter devices, the various feature sizes of the periodic array structure, such as metal interdigital transducers (IDTs), can severely affect the final performance, and must be accurately measured during processing. The period length of the periodic grid array in the periodic array structure is the most important factor influencing the working frequency of the device. At present, the method for measuring the microstructure size such as the periodic grid array period length of the periodic array structure mainly comprises the steps of shooting microscopic images through various microscopes with scales or calibrated microscopes, judging through a machine or manually, selecting certain characteristic positions, and finally comparing the characteristic positions with a preset scale to obtain the required characteristic size. For example, one of the more common measurement methods at present is to take an image of a periodic array structure through various high-precision, calibrated microscopes, and draw a measurement line covering multiple grating periods (e.g., multiple finger periods in a metal interdigital transducer) in the "vertical" direction in analysis software, which can directly take the total length of the measurement line and divide the length by the number of periods to obtain the final finger period length.
Disclosure of Invention
Technical problem to be solved by the invention
However, in the conventional method for measuring the microstructure size of the periodic array structure, the interpretation and selection accuracy of the feature position is not sufficient due to the blurred image boundary, the inaccurate manual identification and the like, so that a large measurement error is generated. For a structure with a periodic grid array, the total length of a plurality of periods is usually selected and measured, and then divided by the number of periods, so as to achieve the effect of reducing errors. However, the method still has the defects of inaccurate interpretation of the positions of the starting characteristic and the ending characteristic, large result caused by array inclination, low operation speed and the like.
The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a method for measuring a cycle length of a periodic grating array, which can quickly and accurately measure a cycle length of a periodic grating array in a device having a periodic array structure.
Means for solving the problemsScheme(s)
In one embodiment of the present invention for solving the above problems, there is provided a measurement method for measuring a periodic grid array in a periodic array structure, including: an image acquisition step of acquiring an image of the periodic array structure and acquiring a pixel pitch value of the image; a measurement line drawing step of drawing a measurement line covering a plurality of the periodic grid arrays on the image; a measurement line parameter determination step of determining coordinate values and image characteristic values of at least a part of pixels on the measurement line, and a slope of the measurement line; a circle frequency calculation step of calculating a spatial circle frequency of the measurement line by using a fitting function using the coordinate value and the image feature value; a measurement line period length calculation step of calculating a measurement line period length in an extending direction of the measurement line using the pixel pitch value and the spatial circle frequency; and an actual period length calculation step of calculating an actual period length of the periodic grating array based on the slope of the measurement line and the measurement line period length.
In other embodiments of the present invention, the measuring method further includes a periodic grid array number calculating step of calculating the grid array number of the periodic grid array covered by the measuring line based on the coordinate values of all the pixels on the measuring line and the period length of the measuring line.
In other embodiments of the present invention, in the measuring method, the measuring line is connected by randomly acquiring two points on the image.
In other embodiments of the present invention, in the measuring method, the measuring lines are connected by randomly acquiring three points on the image.
In another embodiment of the present invention, in the measuring method, among the three points, a first point is set to be located at an arbitrary position near the left or right in the image, and second and third points other than the first point are set to be located at the right or left of the first point, and cover as much of the periodic grid array as possible.
In another embodiment of the present invention, in the measuring method, the measuring lines include a first measuring line and a second measuring line, the first measuring line is obtained by connecting the first point and the second point, the second measuring line is obtained by connecting the first point and the third point, and the actual period length of the periodic grid array is calculated based on a slope of the first measuring line, the period length of the measuring line of the first measuring line, a slope of the second measuring line, and the period length of the measuring line of the second measuring line.
In other embodiments of the present invention, in the measuring method, the fitting function includes a fourier function.
In other embodiments of the present invention, in the measuring method, the actual distance between adjacent pixels in the image is determined according to the calibration, and the measuring line period length in the extending direction of the measuring line is calculated based on the actual distance and the spatial circle frequency.
In another embodiment of the present invention, in the measuring method, the measuring line drawing step, the measuring line parameter determining step, the circle frequency determining step, the measuring line cycle length calculating step, and the actual cycle length calculating step are repeatedly executed a plurality of times, and statistical processing is performed, so that the actual cycle length after calibration is obtained.
In one embodiment, the invention relates to a measurement system for measuring a periodic grid array in a periodic array structure, comprising: a storage section that stores computer instructions; and a control unit that, when executing the computer instructions, causes the system to perform the steps of: an image acquisition step of acquiring an image of the periodic array structure and a pixel pitch value of the image; a measurement line drawing step of drawing a measurement line covering a plurality of the periodic grid arrays on the image; a measurement line parameter determination step of determining coordinate values and image characteristic values of at least a part of pixels on the measurement line, and a slope of the measurement line; a circle frequency calculation step of calculating a spatial circle frequency of the measurement line by using a fitting function using the coordinate value and the image feature value; a measurement line period length calculation step of calculating a measurement line period length in an extending direction of the measurement line using the pixel pitch value and the spatial circle frequency; and an actual period length calculation step of calculating an actual period length of the periodic grating array based on the slope of the measurement line and the measurement line period length.
Effects of the invention
According to the invention, the period length of the periodic grid array can be rapidly and accurately measured.
Further, according to the present invention, when measuring the period length of the periodic grating array, the period length along the normal direction of the fingers of the periodic grating array can be accurately measured even when the period length is inclined, without being affected by the inclination of the fingers or the inclination of the measurement line.
In addition, according to the invention, the period length of the periodic grid array can be measured, and the number of fingers covered by the measuring line segment can be output, so that richer measuring results can be obtained through limited measuring steps.
Drawings
FIG. 1 is a schematic diagram of an interdigital transducer image and sample selection in accordance with one embodiment of the present invention.
Fig. 2 is a flow chart of a measurement method according to an embodiment of the invention.
FIG. 3 is a schematic diagram of an interdigital transducer image and sample selection in accordance with another embodiment of the present invention.
FIG. 4 is a schematic diagram of processing data using a CFTOOL toolkit, according to another embodiment of the present invention.
FIG. 5 is a geometric schematic of a calculation of the period length of an interdigital transducer finger in accordance with another embodiment of the present invention.
Fig. 6 shows calculated interdigital transducer cycle lengths after photographing the same resonator at different angles according to another embodiment of the present invention.
Fig. 7 is a flow chart of a measurement method according to another embodiment of the invention.
Fig. 8 is a block diagram of a measurement system according to yet another embodiment of the present invention.
Detailed Description
Embodiments of the invention may be understood by referring to the exemplary embodiments depicted in the drawings (which are briefly summarized above and discussed in more detail below). The appended drawings, however, illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
< example 1>
Hereinafter, a method of measuring a period length of a periodic grating array according to an embodiment of the present invention will be described with reference to fig. 1 to 2.
In the present embodiment, an interdigital transducer in a surface acoustic wave filter is described as an example of a periodic array structure, but the present invention is not limited thereto, and the measurement method according to the present embodiment can be applied to any device having a periodic array structure, such as a surface acoustic wave resonator, a temperature compensation type surface acoustic wave filter, XSAW, IHP-SAW, or the like. In this embodiment, the terms "interdigital transducer" and "periodic array structure" are used interchangeably, and the terms "finger" and "periodic array" are used interchangeably. In the present embodiment, although Matlab is taken as an example to state that the above-mentioned measuring method is implemented using a program, one skilled in the art will recognize that the measuring method may be implemented using a different programming language or script other than Matlab, and the program may conform to any one of several different programming languages, such as python, Java, C + +, and the like.
In this embodiment, the method for measuring the period length of a periodic grid array begins by acquiring an image of a periodic array structure and acquiring a pixel pitch value of the image. As an example of an image of a periodic array structure, fig. 1 shows a schematic diagram of a piece of interdigital transducer with a scale. The figure is illustrated by an imagesc command, for example of the Matlab program, and is set to set (gca, 'Ydir', 'normal') to keep the x-coordinate of the image of the periodic array of interdigital transducers (i.e. the fingers) increasing from left to right and the y-coordinate of the image of the periodic array of interdigital transducers increasing from bottom to top (when fig. 1 is flipped upside down with respect to the normal). The image may be directly taken with a microscope or the like, or may be obtained from another device through wired or wireless transmission. The finger orientation in fig. 1 is kept as small as possible, for example less than 20 deg., with respect to the coordinate axis X or Y. Fig. 1 shows an example of a case where the finger direction is kept at a small angle to the Y-axis. The line segment labeled "20 μm" in the upper right corner of fig. 2 shows the scale of the figure. The left and right ends of the scale are partially enlarged to obtain pixel coordinates of the left and right ends. The actual pitch sp (i.e., pixel pitch value) between adjacent pixels can be calculated in conjunction with the scale length (20 μm in this embodiment). It should be noted that the case where the pixel pitch value is obtained by a scale in the image is shown here by way of example, but the pixel pitch value may be obtained by other means, such as data on the pixel pitch value transmitted together with the image.
Next, for example, two points are arbitrarily selected on the image to draw a measurement line. In this embodiment, the point on the left side of the arbitrarily selected two points is denoted by a, and the point on the right side is denoted by B. Preferably, the number of fingers covered by the line segment AB connecting the two points A, B is as large as possible (for example, the number of covered fingers is greater than 5). AB is taken as the measurement line for measuring the cycle length.
Then, the coordinate values and image values of the pixels on the measurement line AB, and the slope of AB are determined. For example, first, the pixel coordinate values and RGB values of two points are obtained A, B by the ginput function of Matlab. Although the calculation is performed using the RGB values of the respective points in the present embodiment, the calculation may be performed using other types of image feature values (for example, a gradation value, a Hex color code, an HSL value, and the like). And calculating to obtain the slope of the AB through the pixel coordinate values, and also obtaining the included angle between the AB and the X axis, and recording the included angle between the AB and the X axis as theta. Multiplying the pixel coordinate on the X axis of the point on the AB line (preferably all the points on the AB line, but only part of the points can be selected as required as long as the subsequent fitting requirement is met) by the coefficient (1+ tan)2θ) to perform coordinate transformation and the result is denoted as set x. One of the RGB values along the line AB (the g (green) value is chosen in this example) is stored as set y.
Fitting calculations are then carried out using sets x, y using fitting methods such as least squares fitting, polynomial fitting, fourier fitting, etc. to obtain the spatial circular frequency ω of the metal fingers in the AB direction.
The period length P of the metal fingers in the AB direction can then be calculated using the following equation:
P＝2π/ω*sp (1)
alternatively, the number of fingers N covered by the AB segment can be calculated using the following equation:
N＝(max(x)-min(x))/P (2)
if the actual period length of the finger is denoted as P0, the actual period length P0 can be calculated according to the trigonometric function using the following equation:
P0＝P*sinθ (3)
the actual period length of the finger is thus obtained.
Alternatively, after the actual finger cycle length is obtained, it is determined whether the number n of the obtained actual cycle lengths is sufficient, that is, whether the number n of the actual cycle lengths reaches a threshold n '(the threshold n' is a positive integer of 1 or more, which is the number of samples necessary for the cycle length result to satisfy the expected accuracy). If the number does not reach the threshold n', the obtained actual cycle length is recorded as P0(n), and the step of obtaining the measurement line is returned to obtain a new measurement line again, and the subsequent processing is continued to obtain another actual cycle length P0(n + 1). If the number reaches the threshold value n ', the obtained actual period lengths P0(1) -P0 (n) are subjected to data processing (e.g., averaging, analysis of variance, obtaining an expected value of binomial distribution, etc.) to obtain a more accurate actual period length P0'.
Finally, the desired actual period length P0 and/or the calibrated actual period length P0' of the periodic array are obtained and the method ends.
Fig. 2 is a flowchart of the measurement method according to the present embodiment.
At step S202, an image of the periodic array structure is acquired, and a pixel pitch value (i.e., a distance between nearest neighbor pixels) is acquired.
At step S204, measurement lines AB covering a plurality of array periods are acquired.
At step S206, coordinate values and image characteristic values of at least a part of the pixels on the measurement line AB, and the slope of the measurement line AB are determined.
At step S208, the spatial circular frequency ω of AB is obtained using fitting calculation.
At step S210, the cycle length P in the AB direction is acquired by calculation.
Optionally, at step S212, the number N of array cycles covered by the AB segment is acquired.
At step S214, the actual period length P0 of the periodic array structure is calculated.
Alternatively, at step S216, it is determined whether the number n of the obtained actual cycle lengths P0 reaches a threshold value n '(n' is a positive integer equal to or greater than 1).
If the number n does not reach the threshold value n', the process proceeds to step S218, the obtained actual cycle length is recorded as P0(n), n is set to n +1, and the process returns to S204, a new measurement line is newly acquired, and the subsequent process is continued.
If the number reaches n to the threshold n ', the process proceeds to step S220, and data processing is performed on the obtained actual period lengths P0(1) -P0 (n) to obtain a calibrated actual period length P0'.
Finally, the actual period length P0 and/or the calibrated actual period length P0' of the periodic array are obtained, and the process is ended.
< example 2>
Hereinafter, a method of measuring a period length of a periodic grating array according to another embodiment of the present invention will be described with reference to fig. 3 to 7.
In the present embodiment, although the interdigital transducer in the surface acoustic wave filter is described as an example of the periodic array structure, the method of the present invention is not limited thereto, and can be applied to any device having a periodic array structure, such as a surface acoustic wave resonator, a temperature compensation type surface acoustic wave filter, XSAW, IHP-SAW, or the like. In this embodiment, the terms "interdigital transducer" and "periodic array structure" are used interchangeably, and the terms "finger" and "periodic array" are used interchangeably. In the present embodiment, while Matlab is taken as an example to illustrate the use of a program to implement the above method, those skilled in the art will recognize that the method may be implemented using a different programming language or script other than Matlab, and that the program may conform to any of several different programming languages, such as python, Java, C + +, and the like.
In this embodiment, the method for measuring the period length of a periodic grid array begins by acquiring an image of a periodic array structure and acquiring a pixel pitch value of the image. As an example of a periodic array structure, fig. 3 shows a schematic diagram of a scaled interdigital transducer. Similarly to the above-described embodiment, the figure is illustrated by an imagesc command, for example, of the Matlab program, and is set to set (gca, ' Ydir, ' normal ') to keep the x-coordinate of the image of the periodic array of interdigital transducers (i.e., the fingers) increasing from left to right in turn and the y-coordinate of the image of the periodic array of interdigital transducers increasing from bottom to top in turn (at which time fig. 3 is flipped upside down with respect to the normal case). The image may be directly taken with a microscope or the like, or may be obtained from another device through wired or wireless transmission. The finger orientation in fig. 3 is kept as small as possible, e.g. less than 20, from the coordinate axis X or Y. Fig. 3 shows an example of a case where the finger direction is kept at a small angle to the Y-axis. The line segment labeled "20 μm" in the upper right corner of fig. 3 shows the scale of the figure. The left and right ends of the scale are partially enlarged to obtain pixel coordinates of the left and right ends. The actual pitch sp (i.e., pixel pitch value) between adjacent pixels can be calculated in conjunction with the scale length (20 μm in this embodiment). It should be noted that, here, the case of acquiring the pixel pitch value by the scale in the image is shown only by way of example, but the pixel pitch value may also be acquired by other ways, for example, by acquiring data on the pixel pitch value carried by the image itself.
Next, for example, three points are selected on the image to draw a measurement line. A. B, C the selection rules of the three points are: point a is anywhere to the left of the image, points B and C are to the right of point a, and AB and AC are made to cover as many fingers as possible (e.g., the number of fingers covered is greater than 5). Two lines, AB and AC, are used as measurement lines for measuring the cycle length.
Subsequently, the coordinate values and image values of the pixels on the measurement lines AB, AC and the slopes of AB, AC are determined. For example, first, the ginput function of Matlab is used to obtain A, B, C pixel coordinate values of three points and A, B, C RGB values of three points. Although the calculation using the RGB values of the respective points is exemplified in the present embodiment, the calculation may be performed using other types of image feature values (for example, a gradation value, a Hex color code, an HSL value, and the like). The stronger the spectral components acquired (e.g., spectral components acquired by a microscope), the larger the corresponding RGB values. The slopes of AB and AC can be calculated and obtained through the pixel coordinate values, the included angles between the AB and AC and the X axis can also be obtained, and the included angles between the AB and AC and the X axis are respectively recorded as theta1、θ2. Points along the AB line (preferably all points along the AB line, but may be as desiredSelect some points as long as the subsequent fitting requirement is satisfied) by the coefficient (1+ tan)2θ1) And the result is noted as x 1; multiplying the pixel coordinates on the X axis of the points along the AC line (preferably all the points along the AC line, but only some points can be selected if necessary as long as the subsequent fitting requirement is met) by the coefficient (1+ tan)2θ2) And the result is noted as x 2. One of the RGB values along the line AB (the G (green) value is selected in this example) is stored as y1, and the G value along the line AC is stored as y2 in the same way.
Then, fitting calculation is performed to obtain spatial circular frequencies ω 1, ω 2 of AB, AC. In this embodiment, for example, the fitting calculation is performed using Matlab's cftool kit. Fig. 4 is an interface of Matlab's cftool kit according to an embodiment of the present invention. For example, setting "Xdata" to x1, "Ydata" to y1, "Fourier" is selected at the fitting function (i.e., a Fourier function fit is selected), and the top right most "auto-fit" is selected. The inventors intend to explain that although fitting is performed using a fourier function in the present embodiment, fitting may be performed using another function, for example, least square fitting, polynomial fitting, or the like, and fitting may be performed using another mode, for example, semi-automatic fitting, manual fitting, or the like, although fitting is performed using automatic fitting in the present embodiment. After the calculation, the parameters that are well fitted, for example, the parameters shown in the lower left corner of fig. 3, are obtained. Wherein "w" represents the spatial circular frequency ω 1 of the metal fingers in the AB direction. By the same method, the spatial circular frequency ω 2 of the metal fingers in the AC direction can be obtained by x2, y 2.
The period length P1 of the metal fingers in the AB direction can then be calculated using the following equation:
P1＝2π/ω1*sp (4)
and by the same method, the period length P2 of the metal finger in the AC direction can be calculated by using the following equation:
P2＝2π/ω2*sp (5)
alternatively, the number of fingers N1 covered by the AB segment can be calculated using the following equation:
N1＝(max(x1)-min(x1))/P1 (6)
in the same way, the number of fingers N2 covered by an AC line segment can be obtained using the following equation:
N2＝(max(x2)-min(x2))/P2 (7)
further, the inventors intend to explain that the above-described work interface is only for explaining the method according to the embodiment, and in actual operation, the method may be implemented with a function of matlab using a function such as a "generate code" function provided by cftol, and unnecessary output parts may be deleted, and necessary output may be used as a variable for subsequent operation.
Then, the period length of the periodic grid array is calculated by using a trigonometric function method. Fig. 5 is a geometrical diagram showing calculation of the period length of a periodic grating array (in the present embodiment, the interdigital transducer fingers are taken as an example). The left side of fig. 5 shows the AB direction, the AC direction, the normal to the fingers (the direction in which P0 is located), and the relative position of the fingers (the solid line perpendicular to P0). Here, the actual period of the finger is denoted as P0, the direction in which P0 extends is the normal direction of the finger, and straight lines parallel to each other perpendicular to the normal direction of the finger indicate the direction in which the finger extends. The finger cycle lengths in the three directions are extracted and constitute a ' B ' C ' shown on the right side of fig. 5. Using the cosine theorem, the length of the B 'C' segment can be calculated by the following equation:
L(B’C’)2＝P12+P22-2P1*P2*cos(θ2-θ1) (8)
in addition, the cosine value of ≈ a ' C ' B ' can be calculated by the following equation:
cos(∠A’C’B’)＝[P22+L(B’C’)2-P12]/[2P2*L(B’C’)] (9)
next, after converting the cosine value of ≈ a 'C' B 'to the sine value of ≈ a' C 'B', the actual period length P0 can be calculated by the following equation:
P0＝P2*sin(∠A’C’B’) (10)
alternatively, after the actual finger cycle length is obtained, it is determined whether the number n of the obtained actual cycle lengths is sufficient, that is, whether the number n of the obtained actual cycle lengths reaches a threshold n '(the threshold n' is a positive integer of 1 or more, which is the number of samples necessary for the cycle length result to satisfy the expected accuracy). If the number does not reach the threshold n', the obtained actual cycle length is recorded as P0(n), and the step of obtaining the measurement line is returned to obtain a new measurement line again, and the subsequent processing is continued to obtain another actual cycle length P0(n + 1). If the number reaches the threshold value n ', the obtained actual period lengths P0(1) -P0 (n) are subjected to data processing (e.g., averaging, analysis of variance, obtaining an expected value of binomial distribution, etc.) to obtain a more accurate actual period length P0'.
Finally, the desired actual period length P0 and/or the calibrated actual period length P0' of the periodic array are obtained and the method ends.
Fig. 6 shows the result of processing the period length of the interdigital transducer by using the method after A, B, C three points are randomly selected as required after shooting the same interdigital transducer finger along different angles according to the method of the embodiment. As can be seen from FIG. 6, the actual cycle length results obtained after two measurements are highly consistent, which indicates that the method according to the present invention is not affected by the inclination of the finger and the inclination of the measurement line, and has high accuracy.
Fig. 7 shows a flowchart of the measurement method according to the present embodiment.
At step S702, an image of the periodic array structure is acquired, and a pixel pitch value (i.e., a distance between nearest neighbor pixels) is acquired.
At step S704, two measurement lines AB, AC covering a plurality of array periods are acquired.
At step S706, coordinate values and image characteristic values of at least a part of the pixels on the measurement lines AB, AC, and slopes of the measurement lines AB, AC are determined.
At step S708, the spatial circular frequencies ω 1, ω 2 of AB and AC are obtained using fitting calculation.
At step S710, the cycle lengths P1, P2 in both the AB, AC directions are acquired by calculation.
Optionally, at step S712, the number of cycles N1, N2 covered by AB, AC line segment is acquired.
At step S714, the actual cycle length P0 of the cycle array is calculated.
Alternatively, at step S716, it is determined whether the number n of the obtained actual cycle lengths P0 reaches the threshold value n '(n' is a positive integer equal to or greater than 1).
If the number n does not reach the threshold value n', the process proceeds to step S718, the obtained actual cycle length is recorded as P0(n), n is set to n +1, and the process returns to S704, a new measurement line is acquired again, and the subsequent process is continued.
If the number n reaches the threshold, the process proceeds to step S720, where data processing is performed on the obtained actual period lengths P0(1) -P0 (n) to obtain a calibrated actual period length P0'.
Finally, the actual period length P0 and/or the calibrated actual period length P0' of the periodic array are obtained, ending the process.
In certain embodiments, the operations in the methods in the various embodiments described above may occur simultaneously, substantially simultaneously, or in a different order than shown in the figures. Various operations of the program process and combinations of operations may be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
Although the present invention has been described by taking an interdigital transducer in a surface acoustic wave filter as an example, the present method is not limited thereto, and can be applied to any device having a periodic array structure, such as a surface acoustic wave resonator, a temperature compensated surface acoustic wave filter, XSAW, IHP-SAW, and the like. Although the present invention has been described by taking an example in which 1 or 2 measurement lines are selected for measurement, the present invention is not limited to this, and 3 or more measurement lines may be selected for measurement in the present method.
Although the present invention has been described with an example in which operations such as selecting a measurement line and fitting parameters are performed manually, all or part of the operations may alternatively be automatically performed by a program. In one example, the present invention may be implemented as a program product stored on a computer-readable storage medium for use with a computer system. The program(s) of the program product comprise functions of the embodiments (including the methods described herein). Illustrative computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM machine, flash memory, ROM chips or any type of solid-state non-volatile semiconductor memory) on which information is permanently stored; and (ii) writable storage media (e.g., disk storage or hard disk drives or any type of solid-state random-access semiconductor memory) on which alterable information is stored. Such computer-readable storage media, when carrying computer-readable instructions that direct the functions of the methods described herein, are embodiments of the present invention.
< example 3>
A measurement system 800 for measuring the period length of a periodic grating array according to yet another embodiment of the invention is described below with reference to fig. 8.
A measurement system 800 for making measurements of a periodic grid array in a periodic array structure includes: a storage unit 801 and a control unit 802.
The storage 801 stores computer instructions for execution by the system. The storage is, for example, a computer-readable storage medium, including but not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM machine, flash memory, ROM chips or any type of solid-state non-volatile semiconductor memory) on which information is permanently stored; and (ii) writable storage media (e.g., disk storage or hard disk drives or any type of solid-state random-access semiconductor memory) on which alterable information is stored. For example, the storage unit 801 includes a RAM (Random Access Memory) configured to be able to Read and write data from and to the control unit 802, a ROM (Read Only Memory) configured to be able to Read data from the control unit 802, and the like. The computer instructions are, for example, implemented in hardware, firmware, or software. The computer instructions may be described using any one or more of a variety of programming languages, such as Verilog, VHDL, Matlab, python, Java, C + +, and the like. Further, although the storage 801 is shown as being integrated with the control 802 in one system in the present embodiment, the storage 801 may be separate from the control, for example, the storage 801 may also be a cloud, a remote storage device, a remote server, or the like that communicates with the control 802. The storage unit 801 transmits a computer command to the control unit 802 via wireless communication, wired communication, or the like, or receives a signal such as a feedback signal from the control unit 802.
When the computer instructions are executed, the control unit 802 causes the system to perform the steps of: an image acquisition step of acquiring an image of the periodic array structure and a pixel pitch value of the image; a measurement line drawing step of drawing a measurement line covering a plurality of the periodic grid arrays on the image; a measurement line parameter determination step of determining coordinate values and image characteristic values of at least a part of pixels on the measurement line, and a slope of the measurement line; a circle frequency calculation step of calculating a spatial circle frequency of the measurement line by using a fitting function using the coordinate value and the image feature value; a measurement line period length calculation step of calculating a measurement line period length in an extending direction of the measurement line using the pixel pitch value and the spatial circle frequency; and an actual period length calculation step of calculating an actual period length of the periodic grating array based on the slope of the measurement line and the measurement line period length. The control portion 802 may include, for example, an ASIC (Application Specific Integrated Circuit), an IC (Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), various logic circuits, various Signal processing circuits, and the like.
While certain features of embodiments of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments of the invention.
Claims (10)
1. A measurement method for measuring a periodic grid array in a periodic array structure, comprising:
an image acquisition step of acquiring an image of the periodic array structure and acquiring a pixel pitch value of the image;
a measurement line drawing step of drawing a measurement line covering a plurality of the periodic grid arrays on the image;
a measurement line parameter determination step of determining coordinate values and image characteristic values of at least a part of pixels on the measurement line, and a slope of the measurement line;
a circle frequency calculation step of calculating a spatial circle frequency of the measurement line by using a fitting function using the coordinate value and the image feature value;
a measurement line period length calculation step of calculating a measurement line period length in an extending direction of the measurement line using the pixel pitch value and the spatial circle frequency; and
an actual period length calculation step of calculating an actual period length of the periodic grating based on the slope of the measurement line and the measurement line period length.
2. The measurement method according to claim 1, further comprising a periodic grid array number calculation step of calculating the number of grids of the periodic grid array covered by the measurement line based on the coordinate values of all pixels on the measurement line and the period length of the measurement line.
3. The measurement method according to claim 1 or 2, wherein the measurement lines are connected by randomly acquiring two points on the image.
4. A method of measurement according to claim 1 or 2, wherein the measurement lines are connected by randomly acquiring three points on the image.
5. The measurement method according to claim 4, wherein, of the three points, a first point is set to be located at an arbitrary position near the left or right in the image, and second and third points other than the first point are set to be located at the right or left of the first point, and cover as much of the periodic grid array as possible.
6. The measurement method according to claim 5, wherein the measurement lines include a first measurement line and a second measurement line, the first measurement line is obtained by connecting the first point and the second point, the second measurement line is obtained by connecting the first point and the third point, and the actual cycle length of the periodic grid array is calculated based on a slope of the first measurement line, the cycle length of the measurement line of the first measurement line, a slope of the second measurement line, and the cycle length of the measurement line of the second measurement line.
7. A method of measurement according to claim 1 or 2, wherein the fitting function comprises a fourier function.
8. A method of measurement according to claim 1 or 2, characterized in that the actual distance of adjacent pixels in the image is determined from a scale calibration on the image, and the measurement line period length in the direction of extension of the measurement line is calculated on the basis of the actual distance and the spatial circle frequency.
9. The measurement method according to claim 1 or 2, wherein the measurement line drawing step, the measurement line parameter determination step, the circle frequency determination step, the measurement line cycle length calculation step, and the actual cycle length calculation step are repeatedly performed a plurality of times, and statistical processing is performed, thereby obtaining the actual cycle length after calibration.
10. A measurement system for measuring a periodic grid array in a periodic array structure, comprising:
a storage section that stores computer instructions; and
a control unit that, when executing the computer instructions, causes the system to perform the steps of:
an image acquisition step of acquiring an image of the periodic array structure and a pixel pitch value of the image;
a measurement line drawing step of drawing a measurement line covering a plurality of the periodic grid arrays on the image;
a measurement line parameter determination step of determining coordinate values and image characteristic values of at least a part of pixels on the measurement line, and a slope of the measurement line;
a circle frequency calculation step of calculating a spatial circle frequency of the measurement line by using a fitting function using the coordinate value and the image feature value;
a measurement line period length calculation step of calculating a measurement line period length in an extending direction of the measurement line using the pixel pitch value and the spatial circle frequency; and
an actual period length calculation step of calculating an actual period length of the periodic grating based on the slope of the measurement line and the measurement line period length.
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