JP2009063318A - Apparatus and method for distance measurement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distance-measuring apparatus capable of measuring the distance to an object in a short computation time, without requiring a large amount of collation data. <P>SOLUTION: An ellipse of inertia of the area of an image of the object, having a known shape and at a reference distance is computed, and data of a reference curve acquired by approximating a data constellation of the reciprocal of the ellipticity of the computed ellipse of inertia and the major axis of the ellipse of inertia by a polynomial is stored, in advance, in a reference curve storage means. The distance-measuring apparatus is provided with the reference curve storage means; an image acquisition means for acquiring the images of the object, which is an object of distance measurement; an image analysis means for determining the inertial ellipse of the object in the images acquired by the image acquisition means, the major axis of the inertial ellipse, and the reciprocal of the ellipticity; and a distance computation means for making reference to the reference curve stored in the reference curve storage means, determining the major axis in the reference distance, on the basis of the reciprocal of the inertial ellipse determined by the image analysis means, and determining the distance to the object, on the basis of a ratio between the major axis in the reference distance and the major axis determined, on the basis of the acquired images. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a distance measuring device and a distance measuring method for measuring a distance to a target object using a captured image.

When the target object is located far away from the focal length of the camera, the obtained object image has the following characteristics when the posture of the target object with respect to the camera is constant and the distance between the camera and the target object is different.
(A) The two-dimensional shape of the object image area hardly changes depending on the distance.
(B) The length of the object image area decreases in inverse proportion to the distance.

  Therefore, when the target object has the same posture, if the length of the image at the reference distance is known, the ratio of the length of the reference image to the length of the image in the obtained image is obtained, thereby obtaining the target object. Can be measured. However, since the two-dimensional shape of the object image area varies depending on the posture of the target object, in order to obtain the distance in the conventional method, the posture is measured from the obtained image and the obtained posture is In general, the distance is obtained by calculating the length of the object image area and comparing it with the length of the image when the target object at the reference distance assumes the same posture.

As a prior art, the image information including the target whose distance is to be estimated and the shape model including the actual size information corresponding to the target whose distance is to be estimated are collated, and the distance to the target in the image is estimated passively. A distance estimation device is known (see, for example, Patent Document 1).
JP 2007-077844 A

  However, the conventional image processing calculation has the following problems. That is, the calculation for obtaining the posture from the object image in the image is complicated, takes a long time, and has a large storage capacity for storing the collation data in order to collate with a lot of data for calculating the posture. There is a problem that is necessary.

  The present invention has been made in view of such circumstances, and provides a distance measuring device and a distance measuring method capable of measuring the distance to a target object in a short calculation time without requiring a large amount of collation data. For the purpose.

  The present invention calculates the inertia ellipse of the area of the image of the target object whose shape is known and is separated by the reference distance, and uses the polynomial to calculate the reciprocal of the ellipticity of the calculated inertia ellipse and the major axis of the inertia ellipse using a polynomial. Reference curve storage means in which reference curve data approximated by a curve is stored in advance, image acquisition means for acquiring an image of a target object to be measured for distance, and the target object in the image acquired by the image acquisition means An image analysis means for obtaining an inertia ellipse from the image, a major axis of the inertia ellipse, and an inverse of the ellipticity, and an ellipticity obtained by the image analysis means with reference to a reference curve stored in the reference curve storage means Distance calculating means for obtaining a major axis at the reference distance from the reciprocal of the distance, and obtaining a distance to the target object from a ratio of the major axis at the reference distance and the major axis obtained from an acquired image. And wherein the door.

  The present invention calculates the inertia ellipse of the area of the image of the target object whose shape is known and is separated by the reference distance, and uses the polynomial to calculate the reciprocal of the ellipticity of the calculated inertia ellipse and the major axis of the inertia ellipse using a polynomial. A distance measurement method in a distance measurement apparatus comprising reference curve storage means in which data of a reference curve approximated by a curve is stored in advance, and image acquisition means for acquiring an image of a target object to be measured for the distance, An image analysis step for obtaining an inertial ellipse, a major axis of the inertial ellipse, and a reciprocal of the ellipticity from the image of the target object in the image acquired by the image acquisition means, and a reference curve stored in the reference curve storage means Then, the major axis at the reference distance is obtained from the reciprocal of the ellipticity obtained by the image analysis step, and the ratio between the major axis at the reference distance and the major axis obtained from the acquired image. And having a distance calculation step of obtaining a distance al to the target object.

  According to the present invention, since the calculation process after extraction of the target object image is simpler than the conventional method, an effect that the distance to the target object can be measured in a short calculation time can be obtained. In addition, since the reference curve is stored and a large amount of collation data necessary for obtaining the posture is not required, an effect that the required memory capacity can be greatly reduced is also obtained.

Hereinafter, a distance measuring device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment. In this figure, reference numeral 1 denotes a target object whose distance is to be measured, such as an artificial satellite flying in outer space. Reference numeral 2 denotes a distance measuring device that measures the distance to the target object 1. Reference numeral 21 denotes a camera provided with an optical system lens for obtaining a captured image of the target object 1. Reference numeral 22 denotes an image acquisition unit that reads data of an image captured by the camera 21 and temporarily holds it inside. Reference numeral 23 calculates an inertia ellipse of the area of the image of the target object whose shape is known, and the reciprocal of the ellipticity (minor axis / minor axis) of the calculated inertia ellipse (major axis / minor axis; hereinafter, ellipticity- ¹⁾ Is a reference curve storage unit in which data of a reference curve obtained by approximating a data group of the major axis of the inertia ellipse with a polynomial curve is stored in advance. Reference numeral 24 denotes an image analysis unit that analyzes the obtained image to obtain an inertia ellipse from the image of the target object, and obtains an ellipticity ^{−1 of the} inertia ellipse. Reference numeral 25 determines the major axis of the inertia ellipse corresponding to the ellipticity ⁻¹ obtained by the image analysis unit 24 with reference to the reference curve data stored in the reference curve storage unit 23, and based on the obtained major axis, It is a distance calculation part which calculates the distance to a target object.

  Here, the inertia ellipse of the target object image will be described with reference to FIG. The image analysis unit 24 obtains an inertial ellipse based on the area of the target object image, using the feature that the two-dimensional shape of the object image region hardly changes depending on the distance. FIG. 3 shows an example in which an inertia ellipse is obtained by image processing for two target object images ((a) and (b) shown in FIG. 3) having different distances to the target object. When calculating the distance to the target object, the distance calculation unit 25 uses the reciprocal number (major axis / minor axis) of the ellipticity of the inertia ellipse of the area of the image and the index of the length as the index of the aspect ratio of the target object image. The major axis of the inertia ellipse obtained as follows is used.

Next, a method for generating reference curve data stored in the reference curve storage unit 23 shown in FIG. 1 will be described. First, a target object whose shape is known is set at a reference distance, and a reference image is captured by the camera 21 for various postures and held in the image acquisition unit 22. Thus, the image acquisition unit 22 holds a plurality of reference images as shown in FIG. Then, the image analysis unit 24 calculates an inertia ellipse of the area of the target object image for each reference image group, and approximates the reciprocal of the ellipticity (ellipticity ⁻¹ ) and the long diameter data group by a polynomial. This curve is the reference curve shown in FIG. 5 and is defined by equation (1).

Ra _std = a ₀ γ ⁿ + a ₁ γ ^n-1 + a ₂ γ ^n-2 +... + A _n (1)
^{_{Here, a 0 γ n + a 1}} γ n-1 + a 2 γ n-2 + ···· + a n is the reference curve, gamma is the ellipticity ^-1, _{Ra std} is the major axis of inertia ellipse reference distance . By using this equation (1), if the ellipticity ⁻¹ γ is obtained, the major axis Ra _std of the inertial ellipse at the reference distance can be obtained. The image analysis unit 24 writes the reference curve to the reference curve storage unit 23, thereby generating the reference curve data.
If there is three-dimensional data of the target object, the reference image may be created by computer graphics.

Next, with reference to FIG. 2, the operation of the distance measuring device 2 shown in FIG. 1 for measuring the distance to the target object whose shape is known will be described. First, an image of a target object whose distance is to be measured is captured by the camera 21 (step S1). And the image acquisition part 22 reads the image data of the target object imaged with the camera 21 from the camera 21, and hold | maintains it inside. In response to this, the image analysis unit 24 reads the image data held in the image acquisition unit 22 and obtains an inertia ellipse of the area of the target object image by image analysis processing. Then, the image analysis unit 24 calculates the obtained major axis of the inertia ellipse (the major axis of the inertia ellipse of the image in the acquired image) and the ellipticity ⁻¹ , and outputs them to the distance calculation unit 25.

Next, the distance calculation unit 25 refers to the reference curve stored in the reference curve storage unit 23 and obtains the major axis at the reference distance from the ellipticity ⁻¹ output from the image analysis unit 24. Then, the distance to the target object is obtained from the ratio of the major axis of the acquired image to the major axis at the reference distance according to equation (2).

Z = Z _std · Ra _std / Ra (2)
Here, Z is the distance to the target object, Z _std is the distance to the target object at the reference position (reference distance), Ra is the major axis of the inertia ellipse of the image in the acquired image, and Ra _std is at the reference position. It is the major axis (value obtained from the reference curve) of the inertia ellipse of the image.

  In this way, for an image group obtained by taking various postures of the target object at a fixed distance to the target object, the length of the image with respect to the aspect ratio of the target object image in each image is When uniquely determined, the object distance is obtained by calculating the length of the image at the reference distance corresponding to the aspect ratio of the image in the acquired image and comparing it with the length of the image in the acquired image. be able to. In addition, since the calculation process after extracting the target object image is simpler than the conventional method, the distance to the target object can be measured in a short calculation time. Further, since the reference curve is stored and a lot of collation data necessary for obtaining the posture is not required, the necessary memory capacity can be greatly reduced. In addition, for a three-dimensional object having two orthogonal axes where there is little change in the shape of the image area of the target object with respect to a change in posture due to rotation around the axis of the target object, distance measurement with high accuracy is performed. Is possible.

  The program for realizing the function of the processing unit in FIG. 1 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into the computer system and executed to perform distance measurement processing. You may go. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

It is a block diagram which shows the structure of one Embodiment of this invention. It is a flowchart which shows operation | movement of the distance measuring device 2 shown in FIG. It is explanatory drawing which shows an example of the attitude | position data for calculating | requiring the reference curve memorize | stored in the reference curve memory | storage part 23 shown in FIG. It is explanatory drawing which shows the inertia ellipse of an image area. It is explanatory drawing which shows an example of the reference curve memorize | stored in the reference curve memory | storage part 23 shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Target object, 2 ... Distance measuring device, 21 ... Camera, 22 ... Image acquisition part, 23 ... Reference curve memory | storage part, 24 ... Image analysis part, 25 ... Distance calculator

Claims (2)

Calculate the inertia ellipse of the area of the image of the target object whose shape is known, separated by the reference distance, and approximate the data group of the calculated ellipticity of the inertia ellipse and the major axis of the inertia ellipse using a polynomial curve Reference curve storage means in which curve data is stored in advance;
Image acquisition means for acquiring an image of a target object to be measured for distance;
Image analysis means for obtaining an inertia ellipse, the major axis of the inertia ellipse, and the inverse of the ellipticity from the image of the target object in the image acquired by the image acquisition means;
With reference to the reference curve stored in the reference curve storage means, the major axis at the reference distance is obtained from the reciprocal of the ellipticity obtained by the image analysis means, and the major axis at the reference distance and the obtained image are obtained. A distance measuring device comprising: distance calculating means for obtaining a distance to the target object from a ratio to a major axis. Calculate the inertia ellipse of the area of the image of the target object whose shape is known, separated by the reference distance, and approximate the data group of the calculated ellipticity of the inertia ellipse and the major axis of the inertia ellipse using a polynomial curve A distance measurement method in a distance measurement device comprising reference curve storage means in which curve data is stored in advance, and image acquisition means for acquiring an image of a target object for which distance measurement is to be performed,
An image analysis step for obtaining an inertia ellipse, a major axis of the inertia ellipse, and an inverse of the ellipticity from the image of the target object in the image acquired by the image acquisition means;
Referring to the reference curve stored in the reference curve storage means, the major axis at the reference distance is obtained from the reciprocal of the ellipticity obtained by the image analysis step, and the major axis at the reference distance and the obtained image are obtained. A distance calculating step of obtaining a distance to the target object from a ratio to a major axis.

Images