JP2019041197A - Test chart, test chart generation device, measuring device, test chart generation method, and program - Google Patents

Abstract

To improve measurement accuracy in a device for measuring feeling of resolution by using a test chart.SOLUTION: A test chart generation device comprises a random number generation part and an arrangement part. In the test chart generation device comprising the random number generation part and the arrangement part, the random number generation part generates a random number in association with each of plural long and narrow graphics. In the test chart generation device, the arrangement part determines an angle with respect to one predetermined direction out of the length direction and width direction of each of the graphics on the basis of a random number corresponding to the graphic and arranges the angle.SELECTED DRAWING: Figure 1

Description

  The present technology relates to a test chart, a test chart generation device, a measurement device, a processing method therefor, and a program for causing a computer to execute the method. Specifically, the present invention relates to a test chart for measuring the resolution of an image, a test chart generating device, a measuring device, a processing method in these, and a program for causing a computer to execute the method.

  Conventionally, various types of test charts have been used to evaluate the performance of imaging devices and display devices. For example, the sense of resolution of image data captured by the imaging device can be measured using a test chart. Here, the “resolution feeling” means the fineness of an image felt by humans, and can be expressed by, for example, the high contrast of a portion having a high spatial frequency. However, the measured resolution may deviate from the resolution of the image data. The low contrast parts such as trees and turf are apt to be crushed in detail by signal processing such as noise reduction processing, while the pattern in the test chart has very high contrast, and the signal processing can separate the pattern from noise. This is because it is easy. Trees and turf are patterns that are almost random, but the pattern of the test chart is linear, and the fact that the shaping process by direction detection is easy in signal processing is also a reason for the deviation. As a test chart for measuring a sense of resolution, for example, a chart in which a plurality of circles having different brightness and size are arranged has been proposed (for example, see Non-Patent Document 1).

Robert C Sumner et al., "The Effects of misregistration on the dead leaves crosscorrelation texture blur analysis", IQSP-257, 2017 IS & T International Symposium on Electronic Imaging (2017)

  In the above-described conventional technology, the measurement device can measure the resolution of the image data by Fourier-analyzing the image data of the test chart imaged by the imaging device. However, in order to obtain a smooth measurement result using this test chart, a large measurement area is required, and the contrast near the center of the test chart is low, so that the autofocus function may not focus. Even in an imaging device that tends to lose detail, a constant frequency characteristic appears due to a high frequency component included in an edge portion of a circle having a high contrast and a large diameter. Thereby, even if it is an imaging device which images image data with a bad resolution, a part of measurement result becomes favorable. As described above, the above-described conventional technique has a problem that the measurement accuracy of resolution is low.

  The present technology has been created in view of such a situation, and an object thereof is to improve measurement accuracy in an apparatus that measures a sense of resolution using a test chart.

  The present technology has been made to solve the above-described problems, and the first side of the present technology is that a plurality of elongated figures each having an irregular arrangement angle are arranged in a predetermined region, and the predetermined It is a test chart for measuring the statistic which shows the degree of variation of the pixel value of the area. This brings about the effect that the resolution can be measured with high measurement accuracy.

  Further, in the first aspect, the plurality of graphics includes a plurality of first graphics having a predetermined length and a plurality of second graphics having a length different from the predetermined length, and the predetermined region has a predetermined value with respect to a predetermined value. A first measurement region for measuring the statistic corresponding to a first spatial frequency, which is a ratio of widths of the plurality of first graphics, and widths of the plurality of first graphics with respect to a predetermined value; A second measurement region for measuring the statistic corresponding to a second spatial frequency that is a ratio of the plurality of first figures, wherein the plurality of first figures are arranged in the first measurement region, The second graphic may be arranged in the second measurement region. This brings about the effect that the degree of variation in pixel values is measured for each spatial frequency.

  In addition, the first aspect may further include a reference region in which a specific graphic having an area substantially coincident with the total area of the plurality of first graphics is arranged. This brings about the effect | action that the measured value of a measurement area | region can be normalized.

  The first side surface further includes a flat region without a pattern, and the first measurement region includes the plurality of first graphics arranged on the same background as the flat region, and the second measurement is performed. In the region, the plurality of second graphics may be arranged on the same background as the flat region. This brings about the effect that errors due to noise can be corrected.

  In the first aspect, the first measurement area includes a first bright measurement area in which the luminance of the background is higher than a predetermined luminance, and a first dark measurement area in which the luminance of the background is lower than the predetermined luminance. And the second measurement region may include a second bright measurement region in which the background luminance is higher than the predetermined luminance and a second dark measurement region in which the background luminance is lower than the predetermined luminance. This brings about the effect that the resolution according to the luminance is measured.

  Further, in the first aspect, the plurality of figures include a bright figure having a higher luminance than the background and a dark figure having a lower luminance than the background, and the number and shape of each of the bright figure and the dark figure. May be substantially the same. This brings about the effect that the average luminance of the measurement area substantially matches the background.

  Further, in the first aspect, each of the plurality of figures having the same luminance may not be overlapped with each other, and the distance between the sides may be arranged at a position away from a predetermined distance. This brings about the effect | action that the dispersion | variation in the spatial frequency of a measurement area | region is suppressed.

  In the first aspect, each of the plurality of figures may be an elongated rectangular shape. This brings about the effect that the resolution of the test chart in which the rectangles are arranged is measured.

  In the first aspect, each shape of the plurality of figures may be an oval shape. As a result, the resolution of the test chart in which the oval is arranged is measured.

  In addition, according to a second aspect of the present technology, a test chart generation device including a graphic generation unit configured to disperse a position and an angle for each of a plurality of elongated figures, a test chart generation method, and the method A program for causing a computer to execute. As a result, a test chart in which a plurality of elongated figures each having an irregular arrangement angle is arranged is generated.

  In addition, according to a third aspect of the present technology, a plurality of elongated figures each having an irregular angle are arranged in a predetermined area, and a statistic indicating the degree of variation in pixel values in the predetermined area is measured. A measurement unit that measures the statistics for image data obtained by imaging a test chart for output and outputs the measurement values, and a spatial frequency that is a ratio of each width of the plurality of figures to a predetermined value and the measurement value And an output unit that outputs the data in association with each other. As a result, the spatial frequency and the corresponding measurement value are output.

  Further, in the third aspect, the plurality of graphics includes a plurality of first graphics having a predetermined length and a plurality of second graphics having a length different from the predetermined length, and the predetermined region has a predetermined value with respect to a predetermined value. A first measurement region for measuring the statistic corresponding to a first spatial frequency, which is a ratio of widths of the plurality of first graphics, and widths of the plurality of first graphics with respect to a predetermined value; A second measurement region for measuring the statistic corresponding to a second spatial frequency that is a ratio of the plurality of first figures, wherein the plurality of first figures are arranged in the first measurement region, The second graphic is disposed in the second measurement region, the measurement unit measures the statistics for each of the first and second measurement regions, and the output unit includes the first and second measurement regions. Spatial frequency and each of the first and second measurement regions It may be output in association with each other value. As a result, the spatial frequency and the corresponding measurement value are output for each of the first and second measurement regions.

  The third aspect further includes a normalization unit that normalizes the measurement values of the first and second measurement regions with reference to a predetermined reference value, and the test chart includes the plurality of test charts. A reference area in which a specific figure having an area substantially coincident with the total area of the first figure is arranged, the measurement unit further measures the statistic of the reference area, and the normalization unit The measured value of the area may be normalized as the predetermined reference value. As a result, the measurement value is normalized.

  Further, in the third aspect, the image processing apparatus further includes a correction unit that corrects an error generated in the measurement value due to noise generated in the image data, and the test chart further includes a flat region without a pattern, In the first measurement area, the plurality of first figures are arranged on the same background as the flat area, and in the first measurement area, the plurality of second figures on the same background as the flat area. The measurement unit may further measure the statistic of the flat region, and the correction unit may correct the error based on the measurement value of the flat region. As a result, the error of the measurement value is corrected.

  According to the present technology, it is possible to achieve an excellent effect that measurement accuracy can be improved in an apparatus that measures a sense of resolution using a test chart. Note that the effects described here are not necessarily limited, and may be any of the effects described in the present disclosure.

It is a block diagram showing an example of 1 composition of a test chart generating device in a 1st embodiment of this art. It is a figure showing an example of a test chart in a 1st embodiment of this art. It is an example of the enlarged view of the measurement patch in 1st Embodiment of this technique. It is a figure for demonstrating the arrangement | positioning method of the rectangle in 1st Embodiment of this technique. It is a figure showing an example of a setting parameter in a 1st embodiment of this art. It is a flowchart which shows an example of the test chart production | generation process in 1st Embodiment of this technique. It is a block diagram showing an example of 1 composition of a measuring device in a 1st embodiment of this art. It is a graph which shows an example of the number of pixels for every brightness in a 1st embodiment of this art. It is a graph which shows an example of the characteristic of a feeling of resolution in a 1st embodiment of this art. It is a graph which shows an example of the characteristic of a feeling of resolution for every imaging device in a 1st embodiment of this art. 3 is a flowchart illustrating an example of a resolution characteristic analysis process according to the first embodiment of the present technology. It is a figure showing an example of a figure in a modification of a 1st embodiment of this art. It is a figure showing an example of a test chart in a 2nd embodiment of this art. 12 is a flowchart illustrating an example of resolution characteristic analysis processing according to the second embodiment of the present technology. 10 is a flowchart illustrating an example of a sense of resolution measurement process according to the second embodiment of the present technology.

Hereinafter, modes for carrying out the present technology (hereinafter referred to as embodiments) will be described. The description will be made in the following order.
1. First embodiment (example of arranging a plurality of elongated rectangles)
2. Second embodiment (example in which a plurality of elongated rectangles are arranged for each luminance region)

<1. First Embodiment>
[Configuration example of test chart generator]
FIG. 1 is a block diagram illustrating a configuration example of the test chart generation device 100 according to the first embodiment of the present technology. The test chart generation device 100 is a device for generating a test chart, and includes a random number generation unit 110, an arrangement unit 120, a memory 140, and a test chart output unit 130. As the test chart generation device 100, for example, an information processing device such as a personal computer or a tablet terminal is assumed.

  Here, the “test chart” means the pattern itself used for measuring the resolution. The image data for displaying or printing the test chart is hereinafter referred to as “test chart image”, and the sheet on which the test chart is printed is referred to as “test chart sheet”. The charts do not necessarily have to be a reflection type, and may be a transmission type film, for example.

  The placement unit 120 places a plurality of elongated figures in each of a plurality of regions of a predetermined shape (such as a rectangle) in the test chart. Hereinafter, each of the areas is referred to as a “patch”. The shapes of the figures arranged in the patch are the same, and the aspect ratio is a value other than 1: 1. For example, a rectangle is used as the shape of the figure to be arranged. This figure is hereinafter referred to as “rectangle”.

  In addition, the placement unit 120 reads setting parameters in which the number of rectangles to be placed, the length of the rectangles, and the like are set from the memory 140 via the signal line 129, and the random number generation unit 110 sends a signal line 119 for each of the plurality of rectangles. Receive random numbers via. This random number includes a random number d for determining an angle in the length direction of the rectangle with respect to a predetermined direction (such as a horizontal direction) and a random number (x, y) for determining coordinates to be arranged. For example, an integer value in the range of “1” to “360” is set as the random number d. A random number representing a horizontal coordinate is set for x, and a random number representing a vertical coordinate is set for y. When the number of rectangles to be arranged is N (N is an integer), N random numbers d and N sets of random numbers (x, y) are generated. Here, the “length direction” means the direction of an axis parallel to the long side of the rectangle. Further, the “position” of the rectangle indicates the position of the representative point (for example, the center) of the rectangle in the test chart. In the present embodiment, when generating a rectangle, the random number generator 110 is used as a means for generating concentration to avoid concentration in a specific direction or arrangement position, but the purpose of avoiding concentration in a specific direction or arrangement position is achieved. Any means that can be used may be generated by other means, or may be generated and arranged artificially, and is not limited to the random number generator 110.

  The placement unit 120 determines the position and the angle in the length direction based on a random number corresponding to the rectangle, and places it in the patch. Thereby, the angle at which the rectangle is arranged becomes irregular (in other words, random). The arrangement unit 120 generates a test chart image by the rectangular arrangement and stores the test chart image in the memory 140. The random number generation unit 110 and the arrangement unit 120 are an example of a graphic generation unit described in the claims.

  The random number generation unit 110 generates a random number for each of the plurality of rectangles and supplies the random number to the arrangement unit 120. The random number generation unit 110 generates a random number using, for example, a linear congruential method or a linear feedback shift register.

  The memory 140 holds setting parameters and test chart images. The test chart output unit 130 reads a test chart image from the memory 140 via the signal line 149 and outputs it to a printing device or a display device.

  Note that the test chart output unit 130 may have a printing function and print a test chart image on paper. The test chart output unit 130 may have a display function and display a test chart image.

[Example of test chart]
FIG. 2 is a diagram illustrating an example of a test chart 500 according to the first embodiment of the present technology. In the test chart 500, a DC (Direct Current) patch 501, measurement patches 511 to 520, and a flat patch 502 are arranged. Each patch has the same shape and area.

  Each of the measurement patches 511 to 520 is a patch to be measured. In these measurement patches, a plurality of strip-shaped elongated rectangles are arranged. These rectangles are roughly classified into rectangles having higher luminance than the background (hereinafter referred to as “bright rectangles”) and rectangles having luminance lower than the background (hereinafter referred to as “dark rectangles”). The bright rectangle is an example of a bright figure described in the claims, and the dark figure is an example of the dark figure described in the claims.

  Further, the total number of rectangles (bright rectangles and dark rectangles) and the length of the long sides are different for each measurement patch, and the number of bright rectangles and the number of dark rectangles in each patch are approximately the same. In addition, the total area of the rectangles of the measurement patches is adjusted so as to substantially match. Therefore, the longer the long side, the larger the individual area of the rectangle, so a smaller number of rectangles are arranged. For example, the long side of the rectangular shape of the measurement patch 511 is the longest and the number is the smallest. Further, the long side of the rectangular shape of the measurement patch 520 is the shortest and the number is the largest. Here, “substantially match” means that two values to be compared are the same, or even within a certain allowable value even if there is a difference between them. The measurement patch 511 is an example of the first measurement region described in the claims, and the measurement patch 512 is an example of the second measurement region described in the claims.

  The DC patch 501 is a patch used when normalizing the measurement value of the measurement patch. Specific figures 503 and 504 are arranged on the DC patch 501. The figure 503 has the same luminance as the dark rectangle, and its area substantially matches the total area of the dark rectangle in the measurement patch 511. The graphic 504 has the same luminance as the bright rectangle, and its area substantially matches the total area of the bright rectangle in the measurement patch 511. The shapes of these figures 503 and 504 are, for example, square. The DC patch 501 is an example of a reference area described in the claims.

  The flat patch 502 is a patch used to correct a measurement value error caused by noise. The flat patch 502 has no pattern and is only the background. The flat patch 502 is an example of a flat region described in the claims.

  Although the number of measurement patches is 10, the number of measurement patches is not limited to 10. The number of measurement patches and the position of the patch in the test chart are determined according to the Nyquist frequency and the imaging range of the imaging device to be measured. In addition, although the DC patch 501 is disposed, the DC patch 501 may be disposed when the necessity for normalization is insufficient, such as when image processing in the imaging apparatus is stopped and measurement is performed. In addition, although the flat patch 502 is arranged, the flat patch 502 may be arranged when the necessity for error correction is low, such as when the influence of noise is small.

  FIG. 3 is an example of an enlarged view of the measurement patch 511 according to the first embodiment of the present technology. In the measurement patch 511, a plurality of bright rectangles 531 and the same number of dark rectangles 532 as the bright rectangles 531 are arranged. In the measurement patch 511, the rectangular shape, aspect ratio, and long side length are set to be the same. In addition, the brightness of each of the plurality of bright rectangles 531 is the same, and the brightness of each of the plurality of dark rectangles 532 is also the same. The measurement patches 512 to 520 are different from the measurement patch 511 in the size and number of rectangles.

  By making the number of bright rectangles and dark rectangles the same in each measurement patch, the average luminance of those measurement patches can be made substantially the same as the background. Since the resolution may vary depending on the luminance (brightness), the measurement accuracy can be improved by aligning the overall luminance of each patch to the same level as the background. If there is no need to align the overall luminance with the background, only one of a light rectangle and a dark rectangle can be arranged on the background.

Here, the spatial frequency for each patch is defined as follows. That is, when the short side length (that is, the width) of the rectangle is W and the height of the measurement patch 511 is H, the spatial frequency f of the measurement patch 511 is obtained by the following equation.
f = H / W
In the above equation, the unit of the spatial frequency f is, for example, Cycle / mm or LP / PH, and the unit of the width W and the height H is, for example, millimeter (mm). However, when defining the normal resolution, the definition of the unit of resolution in the industry is defined based on the short side of the captured image as a spatial frequency by convention. (Evaluation Image height), the converted spatial frequency when the entire screen of the captured image is evaluated is EIH / H times. For this reason, the test chart needs to be able to accurately measure the dimension H of each measurement patch, and therefore a marker that can be explicitly observed and measured may be further arranged.

  The rectangular width W of each of the measurement patches 511 to 520 is different, and the height H may be unified for each individual measurement patch in order to facilitate the measurement procedure and unit conversion. f takes a different value. By analyzing an image obtained by capturing a patch of each spatial frequency f, the resolution of the image can be measured. Thus, since the measurement patch is divided for each spatial frequency, the measurement result of the relatively high frequency component does not affect the measurement result of the relatively low frequency component, and the measurement accuracy can be improved. In contrast, in a test chart in which a plurality of circles of different sizes are arranged, high-frequency components are included at the edge of the large circle. It will decline. The spatial frequency of the measurement patch 511 is an example of the first spatial frequency described in the claims, and the spatial frequency of the measurement patch 512 is an example of the second spatial frequency described in the claims. is there.

  Each of the measurement patches can be freely arranged according to the optical characteristics of the imaging device. For example, in general, when the autofocus function is used, the focusing accuracy near the center of the test chart is higher than the surroundings. For this reason, for example, by placing a patch having a relatively low spatial frequency near the center, it is possible to ensure focusing.

  FIG. 4 is a diagram for describing a rectangular arrangement method according to the first embodiment of the present technology. In the figure, a is a diagram showing a measurement patch 511 in which a bright rectangle 531 is arranged, and b in the figure is a diagram showing a measurement patch 511 in which a dark rectangle 532 is further arranged. C in the figure is a diagram showing the measurement patch 511 in which the bright rectangle 533 is further arranged, and d in the figure is a diagram showing the measurement patch 511 in which the position of the bright rectangle 533 is changed.

  As illustrated in a in FIG. 4, the test chart generation device 100 first determines the position of the bright rectangle 531 and the angle in the length direction with respect to a predetermined direction (such as the horizontal direction) at random and arranges the measurement chart 511. To do. Next, the test chart generation device 100 determines the position of the dark rectangle 532 and the angle in the length direction at random and arranges them on the measurement patch 511 as illustrated in FIG. Subsequently, the test chart generation device 100 randomly determines the position of the bright rectangle 533 and the angle in the length direction and arranges them on the measurement patch 511 as illustrated in c in FIG. In addition, although the test chart generation apparatus 100 determines the angle of the length direction with respect to a predetermined direction at random, you may determine the angle of the width direction with respect to a predetermined direction at random instead.

  Here, it is assumed that adjacent bright rectangles do not overlap and that the distance between the sides is more than a predetermined distance. It is assumed that the dark rectangles also do not overlap and the distance between the sides must be more than a predetermined distance. Note that the dark rectangle and the light rectangle may overlap each other, and the distance between the sides may be within a predetermined distance.

  The dotted line c in FIG. 4 indicates the boundary of the proximity region within a predetermined distance from the long and short sides of the bright rectangle. Since a part of the bright rectangle 533 overlaps with the adjacent region, the distance between the sides of the bright rectangle 531 and the bright rectangle 533 is within a predetermined distance. Therefore, the test chart generation device 100 changes the position of the bright rectangle 533 so that it does not overlap with the adjacent region of the bright rectangle 531 as illustrated by d in FIG.

  Here, if the rectangles are randomly arranged without changing the arrangement, bright rectangles and dark rectangles may be concentrated in one place. There is a risk that the spatial frequency is lower than that of the surrounding area, and the spatial frequency varies in the measurement patch, resulting in a decrease in measurement accuracy. Therefore, in the test chart generation device 100, as illustrated in FIG. 4, the position is adjusted so that bright rectangles and dark rectangles do not concentrate in one place. Thereby, it is possible to suppress the variation of the spatial frequency in the measurement patch and improve the measurement accuracy.

  Also, if the angles in the length direction of the rectangles are aligned in the same direction without randomization, the sense of resolution can be measured only for the spatial frequency in the direction perpendicular to the length direction. Therefore, in the test chart generating device 100, the angles in the length direction are arranged at random.

  FIG. 5 is a diagram illustrating an example of setting parameters according to the first embodiment of the present technology. This setting parameter includes “length” and “number of rectangles” for each “patch identifier”. The “patch identifier” is information for identifying each of the measurement patches 511 to 520. “Length” indicates the length of the long side of the rectangle in the measurement patch. “Rectangle number” indicates the total number of light rectangles and dark rectangles arranged in the measurement patch.

  For example, a patch identifier “P1” is assigned to the measurement patch 511. In association with the “P1”, the length “L1” and the number of rectangles “N1” are set. In association with each of “P2” to “P10”, lengths “L2” to “L10” and the numbers of rectangles “N2” to “N10” are set. The length “L1” is set to the maximum value from “L1” to “L10”, and the rectangle number “N1” is set to the minimum value from “N1” to “N10”. After the patch identifier “P2”, a larger number of rectangles are set as the length is shorter. For example, the minimum value is set for the length “L10”, and the maximum value is set for the number of rectangles “N10”.

[Operation of test chart generator]
FIG. 6 is a flowchart illustrating an example of a test chart generation process according to the first embodiment of the present technology. This test chart generation process is started, for example, when a predetermined application for generating a test chart is executed.

  The test chart generation apparatus 100 arranges figures 503 and 504 in the DC patch of the background-only test chart. Then, the test chart generation device 100 selects the first measurement patch, refers to the setting parameter, and acquires the corresponding length and the number N of rectangles (step S901). Next, the test chart generation device 100 randomly determines the position of the bright rectangle and the angle in the length direction for the selected measurement patch (step S902).

  Then, the test chart generation device 100 determines whether or not at least a part of the arranged bright rectangles is within the proximity region of other bright rectangles (step S903). If it is within the proximity area (step S903: Yes), the test chart generation device 100 changes the position of the bright rectangle to a position that does not overlap the proximity area (step 904).

  When it is outside the proximity region (step S903: No), or after step S904, the test chart generation device 100 randomly determines the position of the dark rectangle and the angle in the length direction (step S905).

  Then, the test chart generation device 100 determines whether or not at least a part of the arranged dark rectangle is within the proximity region of another dark rectangle (step S906). If it is within the proximity area (step S906: Yes), the test chart generating device 100 changes the position of the dark rectangle to a position that does not overlap the proximity area (step 907).

  If it is outside the proximity region (step S906: No), or after step S907, the test chart generation device 100 determines whether the number of rectangles in the patch has reached the number (N) corresponding to the measurement patch being arranged. Is determined (step S908).

  When the number of rectangles has reached N (step S908: Yes), the test chart generating device 100 determines whether or not the arrangement of rectangles has been completed for all of the measurement patches (step S909). When the arrangement has not been completed (step S909: No), the test chart generation device 100 selects the next measurement patch to be arranged, refers to the setting parameter, and acquires the corresponding length and the number N of rectangles. (Step S910).

  When the number of rectangles has not reached N (step S908: No), or after step S910, the test chart generating device 100 repeatedly executes step S902 and subsequent steps. When the arrangement is completed (step S909: Yes), the test chart generation device 100 ends the test chart generation process.

[Configuration example of measuring device]
FIG. 7 is a block diagram illustrating a configuration example of the measuring apparatus 300 according to the first embodiment of the present technology. The measuring apparatus 300 is an apparatus for measuring the resolution of image data captured by the imaging apparatus 200, and is connected to the imaging apparatus 200 by wire or wirelessly. As the measuring apparatus 300, for example, an information processing apparatus such as a personal computer or a tablet terminal is assumed. The measurement apparatus 300 includes a measurement unit 310, a correction unit 320, a storage unit 330, a normalization unit 340, and a measurement result output unit 350.

  The imaging device 200 captures a test chart sheet. The test chart sheet is provided at a position away from the imaging device 200 such that the entire test chart can be seen. The imaging apparatus 200 captures image data by focusing on a test chart sheet using an AF (Auto Focus) function or the like. Then, the imaging apparatus 200 supplies the captured image data to the measurement unit 310 via the signal line 209. This image data includes a plurality of pixels arranged in a two-dimensional grid. In addition, although the imaging device 200 is imaging the test chart paper, it can also image the test chart image displayed on the display device instead.

上式において、ｎは、パッチ内の画素数を示す。ｘ_ｉは、パッチ内のｉ番目の画素の画素値（例えば、輝度値）を示す。ｘ_ＡＶＧは、パッチ内の画素値の平均値を示す。 The measurement unit 310 measures, for each patch, a statistic that represents the degree of variation in pixel values of pixels in the patch. As the statistic, for example, the standard deviation s is calculated by the following equation. Note that the statistical quantity to be measured is not limited to the standard deviation s as long as it represents the degree of variation. For example, the measurement unit 310 may calculate the variance instead of the standard deviation s.

In the above formula, n indicates the number of pixels in the patch. x _i represents the pixel value (for example, luminance value) of the i-th pixel in the patch. x _AVG represents an average value of the pixel values in the patch.

  If the number of measurement patches is 10, the total number of patches is 12 including DC patches and flat patches. In this case, 12 standard deviations s are calculated. The measurement unit 310 supplies the standard deviation s to the correction unit 320 via the signal line 319.

The correction unit 320 corrects an error that occurs in the measurement value (standard deviation) of the measurement patch due to noise in the image data, using the measurement value of the flat patch. For example, the correction unit 320 performs correction using the following equation.
s _x '= (s _x ² -s _n ² ) ^1/2
In the above equation, s _x ′ is the standard deviation of the measurement patch after correction, and s _x is the standard deviation of the measurement patch before correction. s _n is the standard deviation of the flat patch.

The correction unit 320 supplies each of the corrected standard deviation s _x ′ and the standard deviation s _DC of the DC patch to the normalization unit 340 via the signal line 329.

The normalization unit 340 normalizes each standard deviation s _x ′ of the measurement patch with reference to the standard deviation s _DC of the DC patch. For example, the standard deviation s _x ′ is normalized by the following equation. The normalization unit 340 outputs each of the normalized standard deviations to the measurement result output unit 350 via the signal line 349.
s _norm = s _x '/ s _DC
In the above equation, s _norm is a standard deviation after normalization.

  Even if the optical characteristics of the optical system of the imaging apparatus 200 are the same, the absolute value of the standard deviation varies if the internal image processing is different. However, normalization can reduce the influence of the fluctuation and evaluate the resolution.

  The storage unit 330 stores data such as frequency information indicating the spatial frequency of each measurement patch.

  The measurement result output unit 350 outputs the spatial frequency and the standard deviation measurement value in association with each measurement patch. The measurement result output unit 350 reads the frequency information from the storage unit 330 via the signal line 339 and receives the normalized standard deviation from the normalization unit 340. Then, the measurement result output unit 350 associates the spatial frequency with the standard deviation, and outputs the result to a display device or the like in the form of a graph or the like indicating the relationship. The measurement result output unit 350 is an example of an output unit described in the claims.

  FIG. 8 is a graph illustrating an example of the number of pixels for each luminance according to the first embodiment of the present technology. In the figure, the vertical axis indicates the number of pixels, and the horizontal axis indicates luminance. The luminance of the dark rectangle is x1, the luminance of the background is x2, and the luminance of the bright rectangle is x3. In a certain measurement patch, the number of pixels of luminance x2 is n1. Since the number of dark rectangles and the number of bright rectangles are the same, the number of pixels with luminance x1 and the number of pixels with luminance x3 are both n2. A standard deviation is calculated from this statistical data.

  FIG. 9 is a graph illustrating an example of resolution characteristics in the first embodiment of the present technology. In the figure, the vertical axis indicates the standard deviation after normalization, and the horizontal axis indicates the spatial frequency of the measurement patch. The solid line indicates the locus when error correction and normalization are performed, and the alternate long and short dash line indicates the locus when normalized without error correction.

  It is assumed that the spatial frequencies of the measurement patches 511 to 520 are f1 to f10 and the standard deviations of s1 to s10 are measured. In general, in a portion having a low contrast, as the spatial frequency increases, the detail is lost due to signal processing and the standard deviation tends to decrease. As a result, there may be a discrepancy between the resolution of the image data and the resolution. Here, “resolution” indicates the density of pixels in the image data. However, an imaging device with a small standard deviation reduction in a high frequency band can be evaluated as having little divergence and good resolution characteristics. The standard deviation near the center of the trajectory is larger than both ends and has a peak, but the standard deviation near the center is large due to image processing such as sharpness processing in the imaging apparatus 200.

  Further, when noise occurs in image data due to various factors such as dark current, an error occurs in the measured value of standard deviation. This noise is often in a granular form close to a circle, and is different in shape from an elongated rectangle. Therefore, the influence of noise on the measured value is almost the same regardless of the spatial frequency, and even if noise occurs, the shape of the trajectory hardly changes.

  On the other hand, when a test chart with multiple circles of different brightness and size is imaged and Fourier-analyzed, the relatively small circle and noise are similar, so the frequency is higher than the error in the low frequency band. Band error is greater. As a result, the shape of the trajectory indicating the Fourier analysis result changes greatly.

  In this way, by using a test chart in which elongated rectangles are arranged, the influence of noise can be reduced and the measurement accuracy of resolution can be improved compared to the case of using a test chart in which circles are arranged.

  FIG. 10 is a graph illustrating an example of resolution characteristics for each imaging device according to the first embodiment of the present technology. In the figure, the vertical axis indicates the standard deviation after normalization, and the horizontal axis indicates the spatial frequency. The solid line indicates the trajectory of the imaging apparatus having the best resolution characteristic, and the dotted line indicates the trajectory of the imaging apparatus having the second best resolution characteristic. An alternate long and short dash line indicates a trajectory of the imaging apparatus having the worst resolution characteristics. As illustrated in the figure, in an imaging apparatus with good resolution characteristics, the standard deviation is unlikely to decrease in the high frequency band.

  FIG. 11 is a flowchart illustrating an example of resolution characteristic analysis processing according to the first embodiment of the present technology. This resolution characteristic analysis process is started, for example, when a predetermined application for measuring the resolution is executed.

  The measuring apparatus 300 measures the standard deviation for each patch (step S951). Then, the measurement apparatus 300 corrects an error in the measurement value of the measurement patch due to noise by using the measurement value of the flat patch (step S952). The measuring apparatus 300 normalizes the standard deviation based on the measured value of the DC patch (step S953), and generates and outputs a graph plotting the standard deviation for each spatial frequency (step S954). After step S954, the measuring apparatus 300 ends the resolution characteristic analysis process. When measuring the resolution of a plurality of imaging devices, steps S951 to S954 are executed for each imaging device.

  As described above, in the first embodiment of the present technology, the test chart generation device 100 generates a test chart in which a plurality of elongated rectangles are arranged. Therefore, the measurement device 300 generates image data obtained by imaging the test chart. The sense of resolution can be accurately measured by analysis.

[Modification]
In the first embodiment described above, the test chart generation device 100 arranges a rectangle, but the shape of the figure is not limited to a rectangle as long as the figure is an elongated figure. The test chart generation device 100 according to the modification of the first embodiment is different from the first embodiment in that a graphic other than a rectangle is arranged.

  FIG. 12 is a diagram illustrating an example of a graphic in the modified example of the first embodiment of the present technology. The test chart generating apparatus 100 can arrange a rounded rectangle that is a rounded rectangle, as illustrated in a and b in FIG. The test chart generating apparatus 100 can also arrange an ellipse as illustrated in c in FIG. An elongated closed curve, such as a rounded rectangle or ellipse, is called an “oval”. The “length direction” of the oval means the direction of the major axis of the oval. Note that the shape of the figure is not limited to a rectangular shape or an oval shape as long as the shape is an elongated shape whose aspect ratio does not correspond to 1: 1. For example, it may be a polygon such as an elongated octagon or an elongated hexagon.

  As described above, in the modified example of the first embodiment of the present technology, the test chart generation device 100 generates the test chart in which the oval is arranged, and thus the measurement device 300 uses the image data obtained by imaging the test chart. The sense of resolution can be accurately measured by analysis.

<2. Second Embodiment>
In the first embodiment described above, the background brightness of the patch is constant. However, assuming that the background brightness fluctuates, there is a possibility that the resolution differs for each brightness. . For example, when the sensitivity of the solid-state imaging device in the imaging apparatus 200 is relatively low, image data may become unclear due to insufficient light quantity when a low-brightness test chart sheet is imaged. For this reason, in the first embodiment in which the luminance of the background is constant, it is not possible to evaluate the characteristic of resolution when the luminance is changed. In order to obtain the resolution characteristic according to the luminance, for example, a plurality of backgrounds having different luminances may be used in the test chart. The test chart of the second embodiment is different from the first embodiment in that a plurality of backgrounds having different luminances are provided.

  FIG. 13 is a diagram illustrating an example of a test chart 550 according to the second embodiment of the present technology. The test chart 550 is provided with four areas having different background brightness. Hereinafter, an area having the same background luminance is referred to as a “luminance area”. Each of the four luminance regions is divided into three blocks. That is, the number of blocks is twelve. These blocks are referred to as blocks 551 to 562.

  An area composed of the blocks 551, 552 and 553 corresponds to the luminance area A, and an area composed of the blocks 554, 555 and 556 corresponds to the luminance area B. A region composed of the blocks 557, 558 and 559 corresponds to the luminance region C, and a region composed of the blocks 560, 561 and 562 corresponds to the luminance region D.

  In the block 551, patches similar to the DC patch 501, the measurement patch 511, the measurement patch 512, and the measurement patch 513 in the first embodiment are arranged. In the block 552, patches similar to the measurement patches 514, 515, 516, and 517 in the first embodiment are arranged. In the block 553, patches similar to the measurement patch 518, measurement patch 519, measurement patch 520, and flat patch 502 in the first embodiment are arranged. The configurations of the luminance regions B, C, and D are the same as those of the luminance region A except that the background luminance is different. The measurement area in the block 551 is an example of the dark measurement area described in the claims, and the measurement area in the block 554 is an example of the bright measurement area described in the claims.

  Although four luminance areas are arranged, the number of luminance areas is not limited to four as long as the number is two or more.

  FIG. 14 is a flowchart illustrating an example of resolution characteristic analysis processing according to the second embodiment of the present technology. The measuring apparatus 300 selects one of the luminance regions (Step S961), and executes a resolution measurement process for measuring the resolution (Step S970). Then, the measuring apparatus 300 determines whether or not all luminance areas have been measured (step S962). When all the luminance regions are not measured (step S962: No), the measuring apparatus 300 repeatedly executes step S961 and subsequent steps. On the other hand, when all the luminance regions are measured (step S962: Yes), the measuring apparatus 300 ends the resolution characteristic analysis process.

  FIG. 15 is a flowchart illustrating an example of a resolution measurement process according to the second embodiment of the present technology. The measuring apparatus 300 measures the standard deviation for each patch (step S971). Then, the measuring apparatus 300 corrects an error due to noise based on the measured value of the flat patch (step S972). The measuring apparatus 300 normalizes the standard deviation based on the measured value of the DC patch (step S973), and generates and outputs a graph in which the standard deviation is plotted for each spatial frequency (step S974). After step S974, the measuring apparatus 300 ends the resolution characteristic analysis process. As a result, a graph is generated for each of the luminance regions A, B, C, and D.

  As described above, in the second embodiment of the present technology, since the test chart generation device 100 generates a test chart including a plurality of luminance regions having different background luminances, the measurement device 300 performs resolution according to the luminance. The characteristic of feeling can be measured.

  The above-described embodiment shows an example for embodying the present technology, and the matters in the embodiment and the invention-specific matters in the claims have a corresponding relationship. Similarly, the invention specific matter in the claims and the matter in the embodiment of the present technology having the same name as this have a corresponding relationship. However, the present technology is not limited to the embodiment, and can be embodied by making various modifications to the embodiment without departing from the gist thereof.

  Further, the processing procedure described in the above embodiment may be regarded as a method having a series of these procedures, and a program for causing a computer to execute these series of procedures or a recording medium storing the program. You may catch it. As this recording medium, for example, a CD (Compact Disc), an MD (MiniDisc), a DVD (Digital Versatile Disc), a memory card, a Blu-ray disc (Blu-ray (registered trademark) Disc), or the like can be used.

  In addition, the effect described in this specification is an illustration to the last, Comprising: It does not limit and there may exist another effect.

In addition, this technique can also take the following structures.
(1) A test chart for measuring a statistic indicating a degree of variation in pixel values of a predetermined area in which a plurality of elongated figures each having an irregular angle are arranged in a predetermined area.
(2) The plurality of figures include a plurality of first figures having a predetermined length and a plurality of second figures having a length different from the predetermined length,
The predetermined area includes a first measurement area for measuring the statistic corresponding to a first spatial frequency that is a ratio of a width of each of the plurality of first figures to a predetermined value, and the predetermined area A second measurement region for measuring the statistic corresponding to a second spatial frequency that is a ratio of the widths of the plurality of first figures,
The plurality of first figures are arranged in the first measurement region,
The test chart according to (1), wherein the plurality of second graphics are arranged in the second measurement region.
(3) The test chart according to (2), further including a reference region in which a specific figure having an area substantially matching the total area of the plurality of first figures is arranged.
(4) further including a flat area without a pattern,
In the first measurement region, the plurality of first figures are arranged on the same background as the flat region,
The test chart according to (2) or (3), wherein the plurality of second graphics are arranged on the same background as the flat region in the second measurement region.
(5) The first measurement region includes a first bright measurement region in which the luminance of the background is higher than a predetermined luminance, and a first dark measurement region in which the luminance of the background is lower than the predetermined luminance,
The second measurement area includes the second bright measurement area in which the luminance of the background is higher than the predetermined luminance and the second dark measurement area in which the luminance of the background is lower than the predetermined luminance. The test chart according to any one of 4).
(6) The plurality of figures include a bright figure having a higher brightness than the background and a dark figure having a lower brightness than the background,
The test chart according to any one of (1) to (5), wherein the number and shape of each of the bright graphic and the dark graphic are substantially the same.
(7) Any one of (1) to (6), wherein each of the plurality of graphics having the same luminance is not overlapped with each other and a distance between the sides is separated from a predetermined distance. Test chart described in.
(8) The test chart according to any one of (1) to (7), wherein each of the plurality of figures is an elongated rectangular shape.
(9) The test chart according to any one of (1) to (7), wherein each of the plurality of figures has an oval shape.
(10) A test chart generation device including a graphic generation unit that disperses and arranges positions and angles for a plurality of elongated figures.
(11) A plurality of elongated figures each having an irregular angle are arranged in a predetermined area, and a test chart for measuring a statistic indicating the degree of variation in pixel values in the predetermined area is imaged A measurement unit that measures the statistic for image data and outputs it as a measurement value;
A measurement apparatus comprising: an output unit that outputs a spatial frequency that is a ratio of a width of each of the plurality of figures to a predetermined value and the measurement value in association with each other.
(12) The plurality of figures include a plurality of first figures having a predetermined length and a plurality of second figures having a length different from the predetermined length,
The predetermined area includes a first measurement area for measuring the statistic corresponding to a first spatial frequency that is a ratio of a width of each of the plurality of first figures to a predetermined value, and the predetermined area A second measurement region for measuring the statistic corresponding to a second spatial frequency that is a ratio of the widths of the plurality of first figures,
The plurality of first figures are arranged in the first measurement region,
The plurality of second figures are arranged in the second measurement region,
The measurement unit measures the statistics for each of the first and second measurement regions;
The measurement device according to (11), wherein the output unit outputs the first and second spatial frequencies and the measurement values of the first and second measurement regions in association with each other.
(13) further comprising a normalization unit that normalizes each measurement value of the first and second measurement regions with reference to a predetermined reference value;
The test chart further includes a reference region in which a specific figure having an area substantially matching the total area of the plurality of first figures is arranged,
The measurement unit further measures the statistic of the reference region;
The measurement apparatus according to (12), wherein the normalization unit normalizes the measurement value of the reference region as the predetermined reference value.
(14) The image processing apparatus further includes a correction unit that corrects an error generated in the measurement value due to noise generated in the image data.
The test chart further includes a flat region without a pattern,
In the first measurement region, the plurality of first figures are arranged on the same background as the flat region,
In the first measurement region, the plurality of second figures are arranged on the same background as the flat region,
The measurement unit further measures the statistics of the flat region;
The measuring device according to (12) or (13), wherein the correction unit corrects the error based on the measurement value of the flat region.
(15) A test chart generation method including a graphic generation procedure for disposing positions and angles in a distributed manner for each of a plurality of elongated figures.
(16) A figure generation procedure for disposing and arranging positions and angles for each of a plurality of elongated figures,
A program that causes a computer to execute.

DESCRIPTION OF SYMBOLS 100 Test chart production | generation apparatus 110 Random number generation part 120 Arrangement | positioning part 130 Test chart output part 140 Memory 200 Imaging device 300 Measurement apparatus 310 Measurement part 320 Correction | amendment part 330 Memory | storage part 340 Normalization part 350 Measurement result output part

Claims (16)

  A test chart for measuring a statistic indicating a degree of variation in pixel values of a predetermined region in which a plurality of elongated figures each having an irregular angle are arranged in a predetermined region. The plurality of figures include a plurality of first figures having a predetermined length and a plurality of second figures having a length different from the predetermined length,
The predetermined area includes a first measurement area for measuring the statistic corresponding to a first spatial frequency that is a ratio of a width of each of the plurality of first figures to a predetermined value, and the predetermined area A second measurement region for measuring the statistic corresponding to a second spatial frequency that is a ratio of the widths of the plurality of first figures,
The plurality of first figures are arranged in the first measurement region,
The test chart according to claim 1, wherein the plurality of second graphics are arranged in the second measurement region. The test chart according to claim 2, further comprising a reference region in which a specific graphic having an area substantially coinciding with a total area of the plurality of first graphics is arranged. It further includes a flat area without a pattern,
In the first measurement region, the plurality of first figures are arranged on the same background as the flat region,
The test chart according to claim 2, wherein the plurality of second figures are arranged in the second measurement area on the same background as the flat area. The first measurement region includes a first bright measurement region in which the luminance of the background is higher than a predetermined luminance, and a first dark measurement region in which the luminance of the background is lower than the predetermined luminance,
5. The test according to claim 4, wherein the second measurement region includes a second bright measurement region in which the luminance of the background is higher than the predetermined luminance, and a second dark measurement region in which the luminance of the background is lower than the predetermined luminance. chart. The plurality of figures include a bright figure having a higher brightness than the background and a dark figure having a lower brightness than the background,
The test chart according to claim 4, wherein the number and shape of each of the bright graphic and the dark graphic are substantially the same. 2. The test chart according to claim 1, wherein each of the plurality of figures having the same luminance does not overlap each other, and the distance between the sides is arranged at a position separated from a predetermined distance. The test chart according to claim 1, wherein each of the plurality of figures is an elongated rectangular shape. The test chart according to claim 1, wherein each of the plurality of figures has an oval shape. Graphic generation unit that distributes positions and angles for each of a plurality of elongated figures

A test chart generating apparatus comprising: Image data obtained by imaging a test chart for measuring a statistic indicating a degree of variation in pixel values of a predetermined area in which a plurality of elongated figures each having an irregular angle are arranged in a predetermined area A measurement unit that measures the statistic and outputs it as a measurement value;
A measurement apparatus comprising: an output unit that outputs a spatial frequency that is a ratio of a width of each of the plurality of figures to a predetermined value and the measurement value in association with each other. The plurality of figures include a plurality of first figures having a predetermined length and a plurality of second figures having a length different from the predetermined length,
The predetermined area includes a first measurement area for measuring the statistic corresponding to a first spatial frequency that is a ratio of a width of each of the plurality of first figures to a predetermined value, and the predetermined area A second measurement region for measuring the statistic corresponding to a second spatial frequency that is a ratio of the widths of the plurality of first figures,
The plurality of first figures are arranged in the first measurement region,
The plurality of second figures are arranged in the second measurement region,
The measurement unit measures the statistics for each of the first and second measurement regions;
The measurement apparatus according to claim 11, wherein the output unit outputs the first and second spatial frequencies and the measured values of the first and second measurement regions in association with each other. A normalization unit for normalizing each measurement value of the first and second measurement regions with reference to a predetermined reference value;
The test chart further includes a reference region in which a specific figure having an area substantially matching the total area of the plurality of first figures is arranged,
The measurement unit further measures the statistic of the reference region;
The measurement apparatus according to claim 12, wherein the normalization unit normalizes the measurement value of the reference region as the predetermined reference value. A correction unit for correcting an error generated in the measurement value due to noise generated in the image data;
The test chart further includes a flat region without a pattern,
In the first measurement region, the plurality of first figures are arranged on the same background as the flat region,
In the first measurement region, the plurality of second figures are arranged on the same background as the flat region,
The measurement unit further measures the statistics of the flat region;
The measurement apparatus according to claim 12, wherein the correction unit corrects the error based on the measurement value of the flat region. A test chart generation method comprising a graphic generation procedure for disposing and arranging positions and angles for each of a plurality of elongated figures. A figure generation procedure for arranging a position and an angle for each of a plurality of elongated figures,
A program that causes a computer to execute.

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