JPH05159057A - Measuring instrument for moving object - Google Patents

Abstract

PURPOSE:To remove the influence of noise and to measure the accurate position of a centroid by obtaining the time sequence of the centroid of the moving object and judging the centroid from a distance between adjacent centroids. CONSTITUTION:An object extraction means 1 extracts the object from a picture and a centroid calculation means 2 calculates the centroid of the object. An inter-centroid distance calculation means 3 calculates the distance of the adjacent centroids. A centroid judgement means 4 judges whether the centroid calculated afterward from the calculated distance of the centroids is the accurate centroid of the object or not and not the centroid of the object which is mistakenly obtained by noise. The centroid judgement means 4 sets it to be the centroid when the distance of the adjacent centroids is smaller than a prescribed judgement value. The moving speed of the object changes. Since the centroid is calculated at a prescribed interval, the distance between the adjacent centroids becomes large when speed is large. Thus, the accurate centroid can be judged by setting the judgement value to be a value corresponding to moving speed by considering the distance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position measuring device for a moving object.

[0002]

2. Description of the Related Art In recent years, image processing apparatuses for processing images captured by a camera such as automatic inspection, unmanned monitoring, and motion analysis are becoming popular. Extract the desired object from the image, position the object,
You can capture information such as size and color. As a result, the image processing apparatus can reduce the work manually performed, can realize the work that the person cannot enter, and can catch the phenomenon that the human cannot recognize. It is attracting attention as a non-contact sensor that plays a role.

FIG. 2 is a block diagram of a conventional system for measuring the position of a dynamic object. Basically, as shown in (a), the target object is extracted from the image, the center of gravity of the target object is calculated, and this center of gravity is used as the measured value of the position of the target object.

FIG. 2B is a block diagram showing the detailed structure of the center of gravity calculating unit in FIG. First, remove noise from the input image,
Projection values of each row and each column of the image are calculated from the image in which the target object is extracted by performing various image processing such as mask calculation.

In the projection value calculation section 21, the image data of the image size in the column direction k, the row direction m, the i-th row and the j-th column is M (i, j).
Then, the horizontal projection Ph [i] of the i-th row, the vertical projection Pv [j] of the j-th row, and the total sum Sum of the projections are calculated as follows.

[0006]

[Equation 1]

The projection section determining unit 22 subdivides the image processing target area, which is the effective range of the image processing, as shown by the broken line in FIG. FIG. 3A shows a dividing method when the X coordinate of the center of gravity is calculated from the vertical projection, and FIG. 3B is a case where the Y coordinate of the center of gravity is calculated from the horizontal projection. The reason for the division is that when the center of gravity is calculated using all the pixel values in one screen, it is affected by noise other than the remaining target object in the image. In particular, it is difficult to calculate the accurate center of gravity in a state where noise cannot be ignored (for example, when the object is very small and noise is present) by comparing the accumulation of noise projection values with the accumulation of object projection values. ..

Further, each section is overlapped as shown in FIG. This is because when an arbitrary section is overlapped and taken at equal intervals as shown in FIG. 4A, in the case of the object A, the desired center of gravity can be calculated because it is located in the section, but in the case of the object B, Since the center of gravity is calculated in each section across the sections, the error of the center of gravity becomes large. The positions of, and in the section represent the center of gravity of the object including noise in each section.

Therefore, as shown in FIG. 4B, the arbitrary sections are overlapped while being shifted by a half cycle. This results in (a)
The center of gravity of the target object B, which could not be calculated accurately with, can also be calculated in sections.

The projection value accumulating section 23 calculates the cumulative value of the projection values calculated by the equation (1) in each section of ... Specifically, if the vertical projection value of a certain j-th column is Pv [j], the cumulative value of the projection values in the section j = L1 to L2 can be calculated by the following formula.

[0011]

[Equation 2]

In order to realize these, an arithmetic unit for calculating a cumulative value of projection values in odd-numbered sections of ,, ...
,, ··· By preparing two calculation units that calculate the cumulative value of the projection values in the even-numbered section, it is possible to suppress the access to the projection values of each column or each row at one time. Sequential operation becomes possible along the scan line. In other words, one screen of the television is 1/60 second, and the position of the center of gravity is calculated within this time.

The maximum cumulative value calculating unit 24 selects the maximum interval from the cumulative values of the projections obtained by the equations (2) and (3). They are (MAXL1, MAXL2),
(MAXL1 ′, MAXL2 ′), and the cumulative values of the projections are MAXPv and MAXPh, respectively.

The center of gravity calculating section 25 calculates the center of gravity in the section where the cumulative value is maximum. The center of gravity can be calculated by the following formula.

[0015]

[Equation 3]

The center of gravity calculated by the equations (4) and (5) is shown in FIG.
FIG. 4 shows a case where there is an overlap of arbitrary sections in (b).
Even in the case where there is no overlap of arbitrary sections in (a), first, if the maximum projection section is obtained, and then that section is expanded and the center of gravity is calculated again, the same results as in equations (4) and (5) are obtained. can get. This will be described in detail in Examples.

[0017]

When the center of gravity of the target object is calculated by the method as described above, in a noisy section,
The center of gravity of the combined target object and noise will be calculated. If the noise is small, the center of gravity of the target object can be obtained, but if the noise is larger than that of the target object, the position of the center of gravity of the target object cannot be correctly calculated.

The present invention has been made in view of the above problems, and an object thereof is to provide a position measuring device for a dynamic object which eliminates the influence of noise and measures the correct position of the center of gravity of the target object. ..

[0019]

FIG. 1 shows the principle of the present invention. In the figure, 1 is an object extracting means for extracting a target object from an image, 2 is a center of gravity calculating means for calculating a center of gravity of the extracted object, 3 is a distance between center of gravity calculating means for calculating a distance between the calculated adjacent centers of gravity, Reference numeral 4 denotes a center-of-gravity determination unit that determines whether or not the center of gravity is correct based on the calculated distance between the centers of gravity.

Further, the center of gravity determining means 4 determines that the center of gravity is correct when the calculated distance between the centers of gravity is smaller than the determination value.

Further, a center-of-gravity velocity calculating means for determining the moving velocity of the center-of-gravity between adjacent centers of gravity is provided, and the judgment value is set to a value corresponding to this center-of-gravity velocity.

[0022]

The object extracting means 1 extracts the target object from the image, the center of gravity calculating means 2 calculates the center of gravity of the target object, and the inter-center of gravity distance calculating means 3 calculates the distance between adjacent centers of gravity. The center-of-gravity determination unit 4 determines whether the center of gravity calculated later is not the center of gravity of the object erroneously obtained by noise but the correct center of gravity of the target object based on the calculated distance between the centers of gravity.

The center-of-gravity determining means 4 determines a correct center of gravity when the distance between adjacent centers of gravity is smaller than a predetermined determination value. This is because the moving target object is grasped at regular time intervals and its center of gravity is calculated, so that the time-series intervals of the centers of gravity do not become disjoint values. Therefore, an appropriate judgment value is set, and if it is smaller than this judgment value, the center of gravity is correct.

The moving speed of the target object changes. On the other hand, since the center of gravity is calculated at fixed time intervals, the distance between adjacent centers of gravity increases as the moving speed increases. By taking this into consideration and setting the determination value to a value corresponding to the moving speed, a more accurate center of gravity can be determined.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 5 is a block diagram of a video rate position measuring apparatus according to an embodiment of the present invention. This device can be used for motion analysis of tennis and golf. For example, in the case of golf, it is possible to measure the position of the golf club head during swing and each position of the player's body at 1/60 second intervals, and use this data to analyze the form. In other words, the target object input from the camera 31 is a DSP (Digital Signal P
The center of gravity of the moving target object is calculated by the processing up to 36, the trajectory of the target object is calculated in the host computer, and it is determined whether the center of gravity calculated by the DSP 36 is correct,
Take out only the correct center of gravity and analyze the form.

In measuring, a color marker is attached to a portion of the subject whose position is to be measured. For example, head, shoulders, waist,
Put color markers on hands and knees. Also, if attached to the head of a golf club, the movement of the head can be analyzed.

In the A / D converter 32, the color video camera 31
Image signals input from R (Red), G (Green), B
(Blue) Convert to digital signal. The color extraction circuit 33 performs data conversion on the R, G, B image data output from the color video camera 31 using a look-up table (LUT), and obtains pixel values only for image data of a plurality of specific colors. A specific value corresponding to that color is output, and a pixel value of 0 is output for other colors.

FIG. 6 is a diagram showing a method of color extraction.
Using T, the designated specific color is represented as 1 and the other colors are represented as 0 to extract the desired color. For details, see JP-A-63-
No. 314988, "Video Rate Color Extraction Device".

The noise removing circuit 34 removes isolated points by using a 3 × 3 logical filter to extract a continuous pattern of dots, such as four connections. FIG. 7 shows an example of a table of output values for a 3 × 3 input pattern.

The projection calculation circuit 35, as shown in FIG. 8, is a horizontal projection for each row for a binary pattern from which noise has been removed,
Determine the vertical projection for each column. The projection calculation circuit 35 is prepared by the number of colors to be identified. The calculation of the projection value is described in detail, for example, in Japanese Patent Laid-Open No. 63-140381, "Video Rate Projection Calculation Circuit".

The calculation of the center of gravity is realized by using the DSP 36. FIG. 9 shows the external RAM of the DSP 36 and the program processing block. The horizontal and vertical projection results obtained by the processing of FIG. 8 are stored in the external RAM of the DSP 36. The maximum value and the minimum value of the moving area of the object from the host computer are stored in the external RAM as the projection effective section. Further, a value about twice the size of the target object is stored in the area of the arbitrary section width of the external RAM as the section width. Using the values of horizontal projection, vertical projection, projection effective section, and arbitrary section width, the cumulative value of the projection values of each section is calculated in sequence.

The section projection values calculated one after another are compared with the maximum section projection value calculated previously, and if larger than that, the section projection value is set as a new section maximum projection value. At the same time, the starting point and the ending point of the section are stored. By repeating this process, the section having the maximum projection value, the start point and the end point of the section are obtained, and are stored in the external RAM.

FIG. 10 is a diagram for explaining the calculation of the maximum projection value in the section. Set 10 as the starting point on the host computer as the effective projection area.
Set the line, end point to 97 lines, and each section width to 4 lines. From the 14th row to the 17th row, the maximum projection value of each row in each section is calculated.
The maximum projection value for a section of a line is 312. From this, it can be seen that the target object is in this section or in an area adjacent to this section.

The center of gravity calculation section may be determined by the section overlapping method shown in FIG. 4, or by the section expansion method as shown in FIG. The interval expansion method is, as shown in FIG. 11, based on the information of the maximum projection interval in which the accumulation of projection values is maximum,
An arbitrary section correction width (for example, half the width of the section width) registered in advance is added before and after the arbitrary section width to expand the section width. If the projection effective section is exceeded, the start point or the end point of the projection effective section is set as the end point of the centroid calculation section.

By determining the center of gravity calculation section in this way, the center of gravity of the object A is calculated only within the section of (a) of FIG. 11, so the accuracy of the center of gravity deteriorates. But,
By expanding the section as in (b) so that the object A falls within the center of gravity calculation section, the center of gravity can be calculated accurately.

Next, the center of gravity calculating section calculates the center of gravity in the center of gravity calculation section determined as described above. In horizontal projection, the start point of the center of gravity calculation section is sth and the end point is edh,
In vertical projection, if the start point of the centroid calculation section is stv and the end point edv, and the cumulative values of the projection values of each section are SUMv and SUMh, the centroid can be calculated by the following equation.

[0037]

[Equation 4]

In this way, the center of gravity of the moving object is
60 points are calculated sequentially, but the host computer stores these centroids, calculates the trajectory of the moving object based on the distance between the centroids, and removes the centroids that deviate from the trajectory.

FIG. 12 shows a gravity center determination procedure for determining a correct center of gravity. The center-of-gravity storage means 41 stores Xcenter and Ycenter calculated by the DSP 36 in time series as in the following equation.

[0040]

[Equation 5]

The center-of-gravity distance calculation means 42 calculates the distance D between adjacent center of gravity as follows.

[0042]

[Equation 6]

The velocity calculating means 43 determines the velocity V of the moving object from the distance D between the adjacent centers of gravity as follows. V = D / dt where dt is the sampling interval for calculating the center of gravity, and in the present embodiment, the center of gravity can be calculated at the video rate, so dt =
It is 1/60 second.

The center-of-gravity determining means 44 determines that the center of gravity (X [i], Y [i]) is correct when if D <D _th , with the allowable distance between adjacent centers of gravity being D _th . else
When, the center of gravity (X [i], Y [i]) is determined as an error.

Allowable distance D_thChanges the moving speed of an object
If it is small, calculate it in advance and use the system as a fixed value.
You can use it. In this case, the speed calculation means 43 is unnecessary
Is. If there is a large change in the moving speed of the object,
Maximum speed of movement, although you can also use maximum speed of movement
Is large and the moving speed of the object is slow, the allowable distance D _th
May become large and pick up the wrong center of gravity.
It Therefore, always monitor the moving speed of the object as follows.
Allowable distance D depending on the moving speed_thIs changed sequentially.

[0046]

[Equation 7]

When the i-1th centroid is incorrect, the i-2th centroid is used to determine whether the ith centroid is correct. At this time, the distance D is doubled, and therefore the following formula is used for calculation.

[0048]

[Equation 8]

Generally, when the reliability of the i-th center of gravity is determined using the j-th center of gravity, the distance between the centers of gravity is calculated by the following formula.

[0050]

[Equation 9]

In this way, the locus of the center of gravity of the moving object is obtained, and the motion can be analyzed from this locus. FIG. 13 shows an example of analysis results of the golf foam obtained in this example. Figure
13 is the result of obtaining the amount of vertical variation of each part from the address to the impact based on the result of calculating the coordinate value of the color marker attached to each part of the body every 1/60 seconds.

[0052]

As is apparent from the above description, according to the present invention, the time series of the centers of gravity are obtained, and the centers of gravity are determined based on the distance between adjacent centers of gravity, so that correct determination can be performed without being affected by noise.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a block diagram of a conventional object position measurement.

FIG. 3 is a diagram showing an example of subdivision of an image processing target area.

FIG. 4 is an explanatory diagram for setting an arbitrary section for calculating the center of gravity of an object.

FIG. 5 is a configuration diagram of a position measuring system of the present embodiment.

FIG. 6 is a diagram illustrating a method of extracting a desired color from an image.

FIG. 7 is a diagram showing a 3 × 3 logical filter.

FIG. 8 is a diagram illustrating a color marker projection calculation method.

FIG. 9 is a diagram illustrating a procedure of a centroid calculation process.

FIG. 10 is a diagram illustrating a method of calculating a maximum projection value in a section.

FIG. 11 is a diagram illustrating a method of enlarging a maximum projection section to determine a centroid calculation section.

FIG. 12 is a block diagram illustrating a gravity center determination procedure.

FIG. 13 is a diagram showing an example of golf swing analysis according to the present embodiment.

[Explanation of symbols]

 21 Projection value calculation unit 22 Projection section determination unit 23 Projection value accumulation unit 24 Maximum accumulated value calculation unit 25 Centroid calculation unit 31 TV camera 32 A / D converter 33 Color extraction circuit 34 Noise elimination circuit 35 Projection calculation circuit 36 DSP 41 Centroid Storage means 42 Distance between center of gravity calculation means 43 Speed calculation means 44 Center of gravity determination means

Claims (3)

[Claims] 1. An object extracting means (1) for extracting a target object from an image, a center of gravity calculating means (2) for calculating a center of gravity of the extracted object, and a distance between center of gravity for calculating a distance between the calculated adjacent centers of gravity. A measuring device for a dynamic object, comprising: a calculating means (3); and a center of gravity determining means (4) for determining whether or not the calculated center of gravity is a correct center of gravity. 2. The apparatus for measuring a dynamic object according to claim 1, wherein the center of gravity determining means (4) determines that the center of gravity is correct when the calculated distance between the centers of gravity is smaller than a determination value. 3. The dynamic object according to claim 2, further comprising a center-of-gravity velocity calculating means for determining a moving velocity of the center of gravity between adjacent center of gravity, and the determination value is a value corresponding to the center-of-gravity velocity. Measuring device.