JP4044454B2 - Position measurement using zoom - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a position measurement method using zoom, in which a measurement target is imaged on a screen at a focal point that is moved by a zoom function of a monocular camera, and the position of the measurement target is measured according to the principle of triangulation using parallax. In particular, the present invention aims to be applied to a machine such as an autonomous robot whose movement is automated by image measurement. That is, the present invention is useful when applied to an automated machine (robot) having a vision (camera) and capable of extracting, specifying, and recognizing an environment and a work target from a captured image.
[0002]
[Prior art]
In general robots, active sensors that emit a signal to an object or the like and detect from a change in the signal are widely used. A major drawback of active sensors is that signal interference is unavoidable, including when there are multiple sensors that emit the same type of signal in the same environment. For example, an ultrasonic sensor and an infrared sensor that are common as active sensors often cannot be measured due to interference between signals. As described above, the types of sensors that can be mounted on the robot are limited to combinations of signals that do not interfere with each other. Further, in an environment where there are a plurality of robots, it is extremely impractical to prepare a combination of sensors that do not interfere with each other.
[0003]
In contrast to the signal interference problem caused by such active sensors, the vision (camera) only receives light from the outside, so there is no signal interference. Also, in the future, assuming a prefectural border where there are multiple robots in the vicinity, non-interfering sensors are indispensable, and visual use is promising in that respect. However, there are some problems due to the use of vision. In the vision of a robot, image measurement by stereo vision composed of two or more cameras is widely used. In stereo viewing, the position of the measurement target is calculated from two or more images having different appearances.
[0004]
As a precondition for measurement, the measurement target on each image must match. For this reason, it is sometimes difficult to associate (distinguish, resolution) the measurement target in an environment where similar patterns exist. Arise. In addition, in order to associate measurement targets, it is essential to accurately install two cameras and adjust camera parameters such as brightness and contrast. In particular, it is impossible to perfectly match camera parameters such as brightness of a plurality of cameras, and adjustment to the color is not performed in most stereo visions. In practice, there is a limit to brightness and contrast adjustment with a monochrome camera.
[0005]
For this reason, a position measurement method using a monocular camera has been proposed in order to avoid the problem of camera parameter adjustment and stereo vision correspondence. This is a manipulator (robot, hand), etc. with a camera attached to the tip. By moving the viewpoint while tracking the object to be measured, parallax is obtained in the same way as in stereo vision, and triangulation The position is measured in principle. In this method, measurement can be performed with relatively high accuracy due to the accuracy of the manipulator, but the facility is large and cannot be mounted on a small mobile robot or the like.
[0006]
Therefore, as a method for measuring the position only with the zoom function of the monocular camera, a lens focusing method using the depth of field of the lens (for example, see Non-Patent Document 1 below) or an image processing apparatus for similar imaging with a zoom lens (described below) (See Patent Document 1). In these methods, the distance to the subject is obtained from the relationship between the focus of the subject and the focus (focus). Specifically, this method is widely used for autofocus cameras, but there are the following two problems when applied to a robot.
[0007]
[Non-Patent Document 1]
K. Ohba, J .; C. Pedraza Ortega: “Micro-observation technology for tele-micro-operation”, Advanced Robotics, vol. 15, no. 8, pp. 779-878, 2000.
[Patent Document 1]
JP-A-5-209730 (FIG. 2 and paragraph 0018)
[0008]
[Problems to be solved by the invention]
(L) In these measurement methods, it is premised that the subject can be focused, and when these techniques are mounted on the mouth bot, it is necessary to have the robot that moves constantly automatically determine the focus. At present, it is difficult to request this determination from the robot. Also, (2) the measurement accuracy by these methods depends on the subject depth of the camera, but as the depth of field becomes shallower, focusing becomes more difficult, and considering the image recognition by the robot, the robot processes It is desirable that the image is in focus as much as possible. Therefore, a lens with a shallow depth of field is not appropriate for robot vision. Furthermore, in the image processing apparatus for similar imaging using the zoom lens of Patent Document 1, it is necessary to accurately measure a minute parallax, which causes a large error in practice and does not endure actual use.
[0009]
Therefore, the present invention solves the problems of the conventional position measurement method using the zoom, and is optimal for autonomously moving robots and the like by making full use of high resolution technology using error prediction and image interpolation technology. An object of the present invention is to provide a zoom position measurement method that can realize a low-cost and compact apparatus by zoom control using a simple monocular lens.
[0010]
[Means for Solving the Problems]
For this reason, the technical solution means adopted by the present invention is:
In the position measurement method by zoom, which measures the position of the measurement object according to the principle of triangulation method by parallax by forming an image on the screen at the focal point moving by the zoom function of the monocular camera,Acquire the image of the measurement object tracked while searching with zoom control at the three-dimensional coordinates with the photosensitive surface as the origin, measure the position of the measurement object from the acquired image data, and store and process the measurement data In determining the three-dimensional position of the measurement point from at least two focal positions, the measurement accuracy, which is an unmeasurable area obtained from the combination of the measurement point position and focal length on the image, is measured. Position measurement by zoom, which is used as an evaluation index for measurement, and selects the combination with the highest measurement accuracy from a plurality of image data of the measurement target acquired by zoom control, and uses it as three-dimensional position measurement data of measurement points In the wayis there.
  Also,Zoom controlAcquisition of the image of the measurement target tracked while searching and storage control of the measurement data from the image data,Distortion correction of the lens of the monocular camera,In addition to performing image enlargement processing and measurement data deterministic control in parallel with uncertainty as an evaluation index of measurement accuracy, it is now possible to search for data that goes back in the past based on the newest data This is a characteristic position measurement method using zoom.
  Also, the zoom position measurement method is characterized in that lens distortion correction is performed on the acquired measurement data based on an internal parameter of the camera at the time when the image is taken.
  Also,The image dataThe zoom position measurement method is characterized in that zooming processing is performed.
[0011]
Embodiment
Embodiments of a position measurement method using zoom according to the present invention will be described below with reference to the drawings. As shown in FIG. 2, the basic configuration of the present invention is to form an image of a measurement object M on a screen at a focal point that is moved by a zoom function of a monocular camera, and position the measurement object according to the principle of triangulation using parallax. In the position measurement method using zoom to measure the image, the image of the measurement target tracked while searching together with the zoom control is acquired in three-dimensional coordinates with the photosensitive surface as the origin, and the position of the measurement target is measured from the acquired image data Thus, the measurement data is stored and processed.
[0012]
Hereinafter, the principle and the superiority based on the experimental results will be described in detail. First, the usefulness in the robot industry of the position measurement method using zoom according to the present invention will be described. Currently, research on highly intelligent robots such as humanoids is actively conducted, but the present result is only a mechanism such as a limb. The next step is thought to be that a robot with a body acquires intelligence, but at the present time, sensing devices are poor. Vision (camera) is a powerful device for realizing intelligent robots, but there is no substitute for stereo vision in terms of position measurement technology, and the measurement method of the present invention is likely to be established as an approach different from stereo vision. . In the future, robots will tend to be smaller, and this position measurement method is also advantageous over stereo vision in that respect.
[0013]
<Basic measurement principle>
The position measurement method using zoom is basically the same as the measurement method using stereo vision, and is a method for obtaining measurement points from two different viewpoints. The measurement principle is shown in FIG. This figure is a view from the side of the camera. The measurement point M seen from the camera is the focal point f moved by zooming._1,f_2,... f_nPosition on the screen depending on the position of₁, V₂, ... v_nIt looks different. This means that a parallax has occurred as in the case of stereo vision, and the position of the measurement point M can be obtained from the measurement principle of triangulation.
[0014]
When the coordinates are defined as in FIGS. 1 and 2, the position of the photosensitive surface is the origin, and the positions of the measurement points on the screen are u and v. Furthermore, from the position (u, v) of the measurement point on the screen, it is defined as the azimuth θ, φ where the measurement point M exists. In this coordinate system, the position of the measurement point M can be obtained by the following equation.
x = (f₂-F₁) Q₁q₂/ (Q₂-Q₁)
y = (f₂-F₁) P₁p₂/ (P₂-P₁(1)
z = (f₁p₁-F₂p₂) / (P₁-P₂)
= (F₁q₁-F₂q₂) / (Q₁-Q₂)
However, q₁= Tanφ₁, Q₂= Tanφ₁, P₁= Tan θ₁, P₂= Tan θ₂And when considering the pinhole model, q₁= V₁/ F₁, Q₂= V₂/ F₂, P₁= U₁/ F₁, P₂= U₂/ F₂Can be obtained as Also, the focal length f when the focal length is continuously moved₁, F₂, F_Three, ... f_nFrom an arbitrary focal length f_i, F_jThe position of the measurement point can also be obtained from the image.
[0015]
<Measurement algorithm>
A rough algorithm of this measurement method is shown in FIG. This algorithm is roughly divided into two processes. One is “search for a measurement target”, acquires an image, controls the zoom mechanism while tracking the measurement target, and records measurement data. This process is performed continuously. For the tracked measurement target, these sets of data, such as the frame number of the captured image (captured time), the camera's internal parameters such as the position and focal length of the measurement target image (screen) at that time Are recorded. The recorded data is preferably stored in a memory on the computer so that a certain amount of data is accumulated. In addition, a past image may be required in the tracking algorithm, and therefore image data may be stored as long as there is a memory capacity.
[0016]
Another process flow will be described. The recorded data is acquired, and “lens distortion correction” is performed based on the internal parameters of the camera at the time when the image was taken, and the position (measurement point) of the measurement target on the image is accurately determined. When the image resolution is insufficient, the image enlargement process is performed to improve the “image resolution resolution”. In this measurement method, the three-dimensional position of the measurement point can be obtained from at least two focal positions, but the measurement accuracy is obtained from the combination of the measurement point position and the focal length on the image. be able to. This measurement uncertainty is used as an evaluation index for measurement accuracy, and a combination having the highest measurement accuracy is selected from a plurality of recorded data and determined as measurement data. The above two processes are performed in parallel, and in order to keep the influence of the imaging delay to a minimum, the data is searched back to the past on the basis of the data just recorded at the present time.
[0017]
<Search for measurement target>
In this measurement method, tracking of the measurement target (tracking) is used in order to effectively use the zoom effect. For this purpose, it is desirable to use a camera having a pan / tilt control mechanism. FIG. 4 shows a method for tracking a measurement target. In FIG. 4, first, an object is searched from an image (step 1). For example, when measuring the box in the figure, the direction of the camera is controlled so that the box becomes the center of the image (step 2). For example, when a general line segment extraction algorithm is applied, a ridge line (edge) of the box can be extracted, and an intersection of the line segments can be selected as a measurement point (FIG. 5 shows an example thereof). At this time, if the camera is directed so that the box becomes the center of the image, the measurement point moves to the edge on the image by zooming in (telephoto). The movement of the measurement point on the image means that “parallax is generated by the movement of the focal point”. In this measurement method, it is desirable to control the orientation of the camera in order to actively use this principle.
[0018]
<Lens distortion correction>
In this measurement method, it is necessary to accurately obtain the orientation of the measurement point from the position on the image. Ideally, it is desirable to use a zoom camera with a known optical system. However, in general, a zoom function is realized by combining a plurality of lenses, and in this case, distortion of the lens occurs. In such a case, it is necessary to correct lens distortion. An outline of the lens correction model is shown in FIG. FIG. 6 is a side view of the zoom lens model. This is a case where a pinhole model is assumed.For example, when obtaining the orientation of a certain measurement point, if there is an error between the orientation of the measurement point obtained from the model and the orientation of the actual measurement point. Corrects lens distortion by a coefficient α. The orientation θ of the actual measurement point at point p is
θ = αtan^-1(V / f)
More demanded. However, the degree of distortion of the lens differs depending on the focal length and the position on the image (position on the photosensitive surface). For this reason, it is possible to obtain a focal length and a position on the photosensitive surface, thereby correcting partial distortion.
[0019]
<Measurement uncertainty>
In measurement in a digital image, the area occupied by one pixel can be considered as uncertainty. That is, as shown in FIG. 7, the measurement point cannot be obtained with a higher resolution than the area occupied by one pixel. This region is an uncertainty in position measurement. In the position measurement method using zoom, a portion where uncertain regions from the respective focal points overlap as shown in FIG. 8 becomes an uncertain region of position measurement, which can be used as measurement accuracy. In order to obtain the measurement uncertainty as shown in FIG. 8, as shown in FIG. 9, the measurement points on the image are positioned at four positions a, b, c, and so on, which are regions of pixel dimensions (Δu, Δv). Obtained from point d. In the position measurement method by zooming, a total of eight positions a, b, c, d and a ′, b ′, c ′, d ′ on the image at two focal points are displayed on the corresponding images. By substituting the position into the equation (1), an uncertain region of measurement can be obtained.
[0020]
As described above, measurement accuracy can be evaluated by obtaining measurement uncertainty. In order to obtain high measurement accuracy, it is necessary to satisfy the following two requirements: “large parallax” and “high image resolution (if the pixel in FIG. 9 is fine, the area of uncertainty is narrow)” is there. Regarding the parallax, two conditions are necessary: “the appearance of the measurement point on the image is greatly different” and “the distance between the two focal points is long”. However, if the distance between the two focal points is increased, the measurement point is out of the image frame. Therefore, it is necessary to control the zoom so that the measurement target does not disappear from the image while always tracking the measurement point. The algorithm of this position measurement method searches the combination with the highest measurement accuracy while evaluating the above-mentioned conditions from multiple images with different focal points while tracking the measurement target, and measuring it And
[0021]
<Image resolution resolution>
As described for uncertainty, when using a digital image, it is necessary to obtain as fine a pixel as possible. For this reason, when the measurement accuracy is insufficient, an image enlargement method is applied to increase the image resolution. This reduces the pixel size on the image and reduces the uncertainty area.
[0022]
  In order to verify the effect of the zoom measurement method based on the theoretical configuration as described above, the results of experiments actually performed using a camera are described below.
<Experimental equipment>
In this research, in order to verify the effect of the zoom measurement method, the actual measurement was performed using a camera. In this actual case, the imageCapuchiA personal computer (Personal Computer, hereinafter referred to as PC) mounted with a board was prepared, and a CCD camera (EVI-D30 manufactured by Sony) capable of controlling the zoom mechanism was connected to the PC. This camera is equipped with an RS-232C compliant serial interface and can control the viewing direction and zoom mechanism by commands from the PC. The focal length f by zooming is 5.4 to 64.8 [mm]. This system configuration is shown in FIG. The specifications of the camera are shown in the table of FIG. The video from this camera is output as an NTSC video signal, and this video can be acquired by a PC at a resolution of 320 × 240 [pixel] or 640 × 480 [pixel 1] within the number of effective pixels.
[0023]
<Looking at measurement points>
In this research, we searched for a characteristic pattern on the image on the PC, and created a program to find the measurement point on the image while gazing at it. Since this program can also control the zoom function, the position of the measurement point in three dimensions is measured from the position of the measurement point on the image with a different viewpoint while moving the viewpoint by zooming. It was to be. A measurement object as shown in FIG. 12 was prepared. FIG. 12 shows an image in which six rectangles having a height of 8.0 [mm] and a width of 8.0 [mm] are arranged in a horizontal row at intervals of 60 [mm]. The rectangle in this image was set as the measurement target. In an image in which similar patterns as shown in FIG. 12 are regularly arranged, it may be difficult to associate the measurement points of the left and right images in stereo view. In the zoom measurement method of the present invention, it is possible to robustly associate measurement points by applying a general tracking method (gazing point tracking method).
[0024]
In this experiment, the measurement points were extracted by performing thumbtack processing such as “binarization”, “labeling”, and “remove noise”, and the measurement points were extracted by labeling. . Then, the center of the extraction pattern is set as a measurement point. 12 was placed at a position of 0.43 [m] in front of the camera (z direction) and 0.0 [m] in the height of the camera (x direction) (FIG. 13). Is in the y direction at positions of 0.16, -0.10, 0.04, 0.02, and 0.08 [m], and the focal length is f = 5.4 [mm] to f. = Tracking the measurement point while zooming to 8.0 and 20.0 [mm], as shown in Fig. 14. By applying a simple tracking method like this experiment, it is robust. It was found that it was possible to track the measurement points.
[0025]
<Extracting measurement points of subpixel order>
In this experiment, in consideration of gaze in real time, it was decided to capture an image at 320 × 240 [pixel1]. In the zoom measurement method, since the position of the measurement point is calculated from minute parallax, it is necessary to obtain the highest possible resolution. Therefore, the labeled area is enlarged up to 6 times in length and width, and the center of gravity is calculated in the area. The center of the measurement point was determined. This corresponds to obtaining the measurement points on the image up to the sub-pixel (Kazunori UMEDA, Takashi TAKAHASHI: “Subpixel Stereo Method: a New Methodology of Stereo Vision”). As an example, FIG. 15 shows a part of an image obtained by enlarging the extracted region up to 6 times in length and width. A linear interpolation method was applied to enlarge the image.
[0026]
<Measurement results>
The values of the CCD camera element size, focal length, etc. used in this study are all theoretical values, and these values must be corrected for use in image measurements in this experiment. Moreover, since the correction for each focal length is complicated, the focal length f, which is a parameter in the zoom measurement method._w, f_tMeasurement point position u on the screen_w, v_wAnd u_t, v_tThe correction coefficient α is determined by setting a polynomial consisting of In this experiment, the refraction of light incident on the lens, which causes image distortion, is assumed, and p = α · u from Equation (1)._t/ f_tAnd f at six measurement points (except z = 0.43 [m]) from α = A · P (A and P are matrices)._w, f_t, u_w, v_w, u_t, v_tThe coefficient of each term was obtained from α obtained from the true value. However, A = [α₁, Α₂, Α_Three, Α_Four, Α_Five, Α₆], P = [f_w, f_t, u_w, v_w, u_t, v_t]^TIt is.
[0027]
As a result, α₁= 3.06 × 10², Α₂= 5.10 × 10^-6, Α_Three= 8.48 × 10^-Four, Α_Four= 3.8, α_Five= 6.57 × 10^-6, Α₆= −1.83 × 10^-3Thus, the correction coefficient α is approximately 1.0 to 1.2. The measurement results are shown in FIG. Of the 6 points in front of the actual vehicle, 4 points close to the center could be measured with sufficient accuracy. In FIG. 16, “+” on the broken line means a true measurement point (True Points), and “◯” means a measured value (Measured Points). Also, the line segment drawn on the circle indicates the region of measurement uncertainty calculated from the resolution of the CCD camera and image used in this experiment. From the measurement uncertainty represented by the line segment, it was confirmed that the uncertainty in the y direction was extremely narrow compared to the z direction. The measurement points A, B, and D have a slight error, and the uncertainty is located so as to include the true value. Therefore, it was found that sufficient measurement accuracy was obtained. In particular, measurement was possible with an error of about several millimeters in the y-axis direction. On the other hand, the measurement point C is slightly away from the true value, and it was found to be an error even when viewed in the uncertainty region. The reason is considered to be that the measurement point has shifted due to the influence of noise or the like on the image processing.
[0028]
<High resolution of measurement points by zooming>
As a feature of the zoom measurement method, image enlargement by zooming (high resolution of measurement points) can be mentioned. In the zoom measurement method, since measurement is performed from a minute parallax, the measurement uncertainty region extends in the z direction. However, since the area is reduced to some extent by increasing the resolution of the measurement point, it is not a diamond for all four points as in the result of FIG. 16, but a narrow area such as a line segment connecting the focus and the measurement result. .
[0029]
<Discussion>
<Parallax andMeasurement accuracyRelationship with>
Based on the results of this experiment, the effects of parallax will be discussed. In the zoom measurement method, the parallax changes as the viewpoint moves. For this reason, it is necessary to grasp the relationship between parallax and measurement accuracy. Therefore, the region of uncertainty in the y-axis and z-axis directions is considered as measurement accuracy, and the relationship between parallax and uncertainty is examined. In FIGS. 17 and 18, the horizontal axis represents parallax and the vertical axis represents uncertainty, and these relationships are represented. The white plot was calculated from the theoretical value based on the formula (1) from the true value. The black plot represents the measurement accuracy in the measurement result, that is, the uncertainty region shown in FIG. 17 and 18, it was confirmed that the greater the parallax, the smaller the dullness and the higher the accuracy of measurement possible.
[0030]
<Measurement uncertainty in the zoom measurement method>
In FIG. 17 and FIG. 18, the measured value and the true value at each measurement point are close to each other. From this, it was confirmed that sufficient measurement results were obtained. Furthermore, all measurement results were located on a curve representing the relationship between the theoretical parallax and the uncertainty obtained from the true value. This means that approximate correction has been correctly performed and measurement points have been obtained up to the sub-pixel. Therefore, it has been found that the cause of the error at the measurement point C is not a distortion of the lens or the like, but a problem in image processing due to noise or fluctuation on the image.
[0031]
<Issues for practical application of zoom measurement method>
From the results of this experiment, it was found that sufficient measurement is possible by obtaining measurement points up to the subpixel order even with a small parallax. To obtain more practical measurement results with the zoom measurement method, (1) obtain an image with high resolution. (2) Camera internal parameters such as lens distortion can be corrected. Are required. With regard to (1), devices such as DV cameras are not only digitized but also increased in resolution, and it is considered that in the future, sufficient resolution for the zoom measurement method will be obtained. In view of the recent increase in computer processing speed, it is expected that image capture and processing will also be performed at high speed. Regarding (2), various distortion correction methods have been proposed. However, a camera having a zoom function combines a plurality of lenses, and correcting this theoretically is a troublesome task. Development of a simpler correction method is desired.
[0032]
<Conclusion>
In this study, to avoid the problem of mapping measurement points like stereo vision, we focused on gaze with a single eye and described “zoom vision” in which the focal point is changed and the viewpoint is moved while gazing. Then, the “zoom measurement method” was proposed as a new image measurement method for obtaining the position of the measurement point based on the zoom view. In this study, we provided a zoom vision formulation and an uncertainty calculation method, and actually measured the position of similar patterns using a CCD camera with a zoom mechanism. And the usefulness of the zoom measurement method was shown by evaluation of the measurement result and uncertainty.
[0033]
As described above, according to this zoom measurement method, (1) since only one camera is used, it is not necessary to install a plurality of cameras and adjust camera parameters as in stereo view. Moreover, since only a camera equipped with a zoom function is used, the equipment is simple and small. (2) By applying the tracking (tracking) technique of measurement points by gaze, it is possible to avoid the problem of associating measurement points, which is a problem in stereo vision. Specifically, even if there are objects with similar patterns such as tiled and latticed patterns, this measurement method can always keep a close eye on a measurement object, and thus a matching problem such as stereo vision arises. Absent. (3) Since it is not necessary to create an out-of-focus image unlike the lens focusing method, advanced image processing such as image recognition, perceptual processing, and the like can be applied simultaneously while applying this measurement method.
[0034]
The embodiment of the present invention has been described above. However, within the scope of the present invention, a monocular camera format, a zoom function configuration, a screen configuration, a format and its three-dimensional coordinate setting configuration, and a zoom control configuration , Search with a monocular camera, tracking form, acquisition form of a measurement target image, measurement form of a position from image data, storage form of the measurement data, camera internal parameter setting form, lens distortion correction form, image enlargement processing Form, setting form of measurement uncertainty as an evaluation index of measurement accuracy, parallel control form with storage control form of measurement data and confirmation control form of measurement data, search form of data going back to the past based on new data Etc. can be selected as appropriate. Moreover, each specification etc. of an experimental apparatus are illustrations, and these should not be interpreted limitedly.
[0035]
【The invention's effect】
As described above in detail, in the present invention, a zoom is performed in which a measurement target is imaged on a screen at a focal point that is moved by a zoom function of a monocular camera, and the position of the measurement target is measured by the principle of triangulation using parallax. In the position measurement method according to the method, the image of the measurement target tracked while searching together with the zoom control is acquired in three-dimensional coordinates with the photosensitive surface as the origin, and the position of the measurement target is measured from the acquired image data. Since data is stored and processed, even if it is applied to a moving subject such as a robot, it can be easily viewed even if the measurement target is a similar pattern by applying measurement point tracking technology by gaze. , You can reliably acquire and process images in 3D coordinates with the photosensitive surface as the origin, and there is no need to install multiple cameras or adjust camera parameters. Only used one camera equipped with a function, it is possible to equipment specifically to be simple and compact.
[0036]
In addition, when the obtained measurement data is subjected to lens distortion correction based on the internal parameters of the camera at the time when the image is taken, a more accurate azimuth of the measurement point that is the object is obtained. It becomes possible. Furthermore, when the image enlargement process is performed, when the resolution of the image is insufficient, it is possible to increase the resolution of the image resolution and obtain the measurement value more accurately. Furthermore, when determining the three-dimensional position of a measurement point from at least two focal positions, the measurement accuracy is the measurement uncertainty, which is an unmeasurable area obtained from the combination of the position of the measurement point on the image and the focal length. When selecting the combination with the highest measurement accuracy from multiple acquired image data and using it as measurement data, obtain measurement values with higher accuracy by recognizing measurement uncertainty. Can do.
[0037]
Further, acquisition of the image of the measurement object tracked while searching together with the zoom control and storage control of the measurement data from the image data, distortion correction of the lens, image enlargement processing, and uncertainty are evaluated as an evaluation index of the measurement system. In addition to performing the final control of the measured data in parallel, it is possible to search for data that goes back in the past based on the newest data, and to minimize the effects of imaging delays. . Thus, by making full use of high resolution technology using error prediction and image interpolation technology, it is possible to realize a low-cost and compact device by zoom control using a monocular lens that is optimal for autonomously moving robots, etc. A position measurement method is provided.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a basic principle of position measurement by zoom, which is the basis of the present invention.
FIG. 2 is a three-dimensional coordinate diagram with a photosensitive surface as an origin adopted in the position measurement method using zoom according to the present invention.
FIG. 3 is a schematic diagram of an algorithm of a position measurement method using zoom according to the present invention.
FIG. 4 is a diagram illustrating an example of a tracking method of a measurement target.
FIG. 5 is a diagram illustrating an example of movement of measurement points by zooming in.
FIG. 6 is a conceptual diagram of lens distortion correction.
FIG. 7 is an explanatory diagram of measurement uncertainty in a digital image.
FIG. 8 is an explanatory diagram of measurement uncertainty in the position measurement method using zoom.
FIG. 9 is an explanatory diagram of an area of one pixel on the digital image.
FIG. 10 is a system configuration diagram of an experimental apparatus for verifying the effect of the position measurement method using zoom according to the present invention.
FIG. 11 is a table of an example of camera specifications.
FIG. 12 is an example of an array of measurement points to be measured.
FIG. 13 is an arrangement diagram of measurement points installed in front of the camera.
FIG. 14 is a state diagram of an example of tracking measurement points.
FIG. 15 is an enlarged view of measurement points.
FIG. 16 is an example of a measurement result of measurement points.
FIG. 17 is an example of a measurement result of a measurement value and a true value according to a relationship diagram of parallax and uncertainty in the y direction.
FIG. 18 is an example of a measurement result of a measured value and a true value according to a relationship diagram between parallax and uncertainty in the z direction.
[Explanation of symbols]
      M Measurement target3D position

Claims (4)

In a position measurement method using zoom, which measures the position of the measurement object according to the principle of triangulation method by parallax by forming an image on the screen at the focal point moving by the zoom function of the monocular camera, the third order with the photosensitive surface as the origin In the original coordinates, acquire the image of the measurement target tracked while searching together with zoom control, measure the position of the measurement target from the acquired image data, and store and process the measurement data, at least two focus positions When measuring the three-dimensional position of the measurement point from the measurement uncertainty, the measurement uncertainty, which is a non-measurable area obtained from the combination of the measurement point position on the image and the focal length, is used as an evaluation index for measurement accuracy. Select the combination with the highest measurement accuracy from the multiple image data of the measurement target acquired by zoom control, and use it as the 3D position measurement data of the measurement point Position measuring method according to the zoom characterized and. Acquisition of the image of the measurement object tracked while searching with the zoom control and storage control of the measurement data from the image data , distortion correction of the lens of the monocular camera, image enlargement processing, evaluation of uncertainty and measurement accuracy evaluation The zoom position according to claim 1, wherein the measurement data used as the index is determined and controlled in parallel, and the search for data going back in the past is made possible based on the newest data. Measurement method. 3. The position measurement method using zoom according to claim 1, wherein the obtained measurement data is subjected to lens distortion correction based on an internal parameter of the camera at the time when the image is taken. . The zoom position measurement method according to claim 1, wherein the image data is enlarged.

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