KR101199913B1 - Cross type stereo vision system and method for measuring distance - Google Patents

Abstract

The present invention discloses a cross-type stereo vision system and a distance measuring method using the same. The distance measuring method according to the present invention is a distance measuring method using a cross-type stereo vision system including left and right cameras, and (a) projection of a target image located on a pixel plane of the left and right cameras into a virtual window. The virtual window is defined as a virtual plane connecting a point where the viewing angle boundary lines of the left and right cameras meet; (b) calculating binocular difference by left and right cameras on the projected target; And (c) calculating a distance between the baseline and the target using the calculated binocular difference. According to the present invention, there is an advantage that accurate distance measurement is possible by introducing a virtual window.

Description

Cross-type stereo vision system and distance measurement method using the same {CROSS TYPE STEREO VISION SYSTEM AND METHOD FOR MEASURING DISTANCE}

The present invention relates to a cross-type stereo vision system and a distance measuring method using the same. More particularly, in a stereo vision system having left and right cameras, a system capable of appropriately adjusting the angle of the left and right cameras according to a distance from a target and the same It relates to the distance measuring method used.

The stereo vision system refers to a system for extracting stereoscopic image information from two images input to two cameras installed at left and right sides. Similar to a method of obtaining distance information to a specific object (target) by using two eyes of a person, such a stereo vision system detects where a target at a specific position in one image is located in the other image by detecting two positions. The distance from the camera to the target is calculated by extracting the difference, i.e., disparity.

In general, a stereo vision system is divided into a balance type in which the positions of the left and right cameras are fixed to the baseline, and a cross type in which the angles of the left and right cameras are adjusted.

1 is a diagram illustrating a balanced type stereo vision system.

As shown in FIG. 1, the equilibrium type is designed such that the left and right cameras 100 and 102 are disposed parallel to the baseline 104 and look in the same direction.

On the other hand, Figure 2 is a diagram showing a cross-type stereo vision system, the cross type is inclined at a constant angle with respect to the baseline 102 while the two cameras (100, 102) are rotated by a drive means such as a motor (200) It means to be placed in a binary state.

In the cross type, the left camera 100 and the right camera 102 are adjusted to have the same angle with respect to the baseline 104.

3 is a diagram illustrating a pixel plane used for distance measurement in a balanced type and a cross type stereo vision system.

Here, it is assumed that two cameras have the same viewing angle.

Referring to FIG. 3, in order to measure the distance of a specific object, a surface 300 in which the first pixel surface by the left camera 100 and the second pixel surface by the right camera 100-2 overlap is used. In comparison with the cross type (FIG. 3B), the size of the pixel plane 300 used for the distance measurement is always smaller than the cross type (FIG. 3B).

Therefore, although it is preferable to use a cross-type stereo vision system for distance measurement, the conventional cross-type stereo vision system has a problem of having different binocular differences even when objects are in the same position.

4 to 5 illustrate binocular differences in the pixel plane with respect to targets at different positions in the balanced type and cross type stereo vision systems, respectively.

As shown in FIG. 4, in the case of the balanced method, all objects having the same distance from the camera have the same binocular difference.

FIG. 5 is a diagram illustrating binocular difference when the pixel planes of the left and right cameras 100 and 102 are positioned as one reference point. As shown in FIG. 5, in the case of the cross type, the object is at the same distance from the camera. The pixel plane has different binocular differences depending on the position of the object, which makes it difficult to accurately measure distances.

The present invention to solve the problems of the prior art as described above, to propose a cross-type stereo vision system and a distance measuring method using the same that can accurately measure the distance between the camera and the object while securing a large pixel plane for distance measurement do.

In order to achieve the above object, according to a preferred embodiment of the present invention, a distance measuring method using a cross-type stereo vision system including a left and right camera, (a) a virtual target image located on the pixel plane of the left and right cameras; Projecting into a virtual window, wherein the virtual window is defined as a virtual plane connecting a point where the viewing angle boundary lines of the left and right cameras meet; (b) calculating binocular difference by left and right cameras on the projected target; And (c) calculating a distance between the baseline and the target using the calculated binocular difference.

The distance measuring method according to the present invention comprises the steps of: determining whether the calculated binocular difference exceeds a preset threshold; If the calculated binocular difference exceeds the threshold, the method may further include adjusting an angle of the left and right cameras so that the virtual window is positioned at an estimated distance corresponding to the calculated binocular difference.

The angle adjustment step may be performed using the following equation.

[Mathematical Expression]

Where G is the angle of the left and right cameras and the baseline, a is the viewing angle of the left and right cameras, A is the distance from the baseline to the virtual window, and B is the distance of the left and right cameras.

After the angle adjustment of the left and right cameras, steps (a) to (c) may be repeatedly performed.

The virtual window may be defined as a virtual plane connecting the points where the viewing angle boundary lines in the same direction of the left and right cameras meet.

The binocular calculation step may include: calculating coordinates on the target projected onto the virtual window; And calculating the binocular difference on the target using the calculated coordinates.

The pixel plane may be divided into a positive pixel plane (+ pixel) and a negative pixel plane (-pixel) with respect to the virtual window with respect to the center.

According to another aspect of the present invention, there is provided a cross-type stereo vision system, comprising: left and right cameras positioned on a baseline; And a control unit configured to calculate a disparity in a virtual window on a target obtained from the left and right cameras, and calculate a distance between the baseline and the target using the calculated binocular difference. Including, the virtual window is provided with a cross-type stereo vision system is a virtual plane connecting the point where the viewing angle boundary of the left and right cameras overlap.

According to the present invention, an accurate distance measurement using a virtual window in a cross-type stereo vision system is possible.

1 shows a stereo vision system of the balanced type.
2 illustrates a cross type stereo vision system.
3 illustrates a pixel plane used for distance measurement in a balanced type and cross type stereo vision system.
4 to 5 show binocular differences in pixel plane relative to targets at different positions in the balanced and cross type stereo vision systems, respectively.
6 illustrates a cross type stereo vision system according to a preferred embodiment of the present invention.
7 is a view showing a detailed configuration of a control unit according to an embodiment of the present invention.
8 is a view for showing the position of the virtual window in the cross type according to an embodiment of the present invention.
9 is a diagram illustrating a binocular vehicle in a state in which a virtual window is introduced according to an embodiment of the present invention.
10 to 11 are views for explaining the angle adjustment process according to the present invention.
12 illustrates pixel planes of the virtual window and the left and right cameras.
FIG. 13 illustrates a projection from a positive pixel plane to a virtual window according to an embodiment of the present invention. FIG.
FIG. 14 illustrates a projection from a negative pixel plane to a virtual window according to an embodiment of the present invention. FIG.
15 is a flowchart illustrating a distance measuring process according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate a thorough understanding of the present invention, the same reference numerals are used for the same means regardless of the number of the drawings.

6 illustrates a cross type stereo vision system according to an exemplary embodiment of the present invention.

As shown in FIG. 6, the system according to the present embodiment may include a left camera 600, a right camera 602, and a controller 604.

The left camera 600 and the right camera 602 are disposed on a baseline serving as a predetermined reference line, and the controller 604 uses the images obtained from the left camera 600 and the right camera 602 to target the target. Calculate binocular difference and use it to calculate the distance from the baseline to the target.

In addition, the angles of the left and right cameras 600 and 602 may be adjusted for accurate distance measurement.

As described above, the left camera 600 and the right camera 602 may be connected to a motor (not shown), the control unit 604 outputs a control signal to the motor for accurate distance measurement to the left camera 600 and The right camera 602 makes a predetermined angle with the baseline.

7 is a diagram illustrating a detailed configuration of a control unit according to an embodiment of the present invention.

As shown in FIG. 7, the controller according to the present exemplary embodiment may include a binocular difference calculator 700, a distance calculator 702, and an angle adjuster 704.

The binocular vehicle calculation unit 700 calculates the binocular difference with respect to the target using the images obtained from the cameras 600 and 602 arranged side by side on the left and right sides.

The binocular difference calculator 700 according to the present exemplary embodiment calculates the binocular difference in the virtual window with respect to the target so that a problem in which the binocular difference is different depending on the position of the target at the same distance does not occur.

According to the present exemplary embodiment, when an image of a target is obtained from the left and right cameras 600 and 602, the image of the target is projected into the virtual window, and the binocular vehicle calculation unit 700 is projected onto the target projected into the virtual window. Calculate the binocular difference.

Here, the virtual window is defined as a virtual plane connecting the points where the viewing angle boundary lines of the left and right cameras 600 and 602 overlap.

8 is a diagram illustrating a position of a virtual window in a cross type according to an embodiment of the present invention.

Referring to FIG. 8, when the left camera 600 and the right camera 602 have a preset viewing angle a and are inclined at a predetermined angle G with respect to the baseline 800, the left and right viewing angle boundary lines overlap. The losing point P1 / P2 is present.

For one camera, the viewing angle boundary line includes a left viewing angle boundary line 802 and a right viewing angle boundary line 804. In this embodiment, the virtual window is set using a point where the viewing angle boundary lines in the same direction of the left and right cameras 600 and 602 meet. Can be.

That is, P1 is a point where the left viewing angle boundary lines of the left and right cameras 600 and 602 meet, P2 is a point where the right viewing angle boundary lines meet, and the virtual window is defined using the above-described P1 and P2.

The distance calculator 702 calculates the distance from the baseline to the target by using the binocular difference with respect to the target in the virtual window as described above.

Since the distance is measured using a binocular car, a detailed description thereof will be omitted.

9 is a diagram illustrating a binocular vehicle in a state in which a virtual window is introduced according to an embodiment of the present invention.

As shown in FIG. 9, when setting the virtual window as in this embodiment, the binocular difference (D1 = D2 = D3) of the targets L / C / R located at the same distance as the baseline 800 is Have the same value. Accordingly, even if the target is located in any direction with respect to the left and right cameras 600 and 602, the distance can be accurately measured.

For accurate distance measurement, the binocular difference is preferably less than or equal to a preset threshold on the virtual window, and when the binocular difference of the target on the virtual window is greater than or equal to the threshold, the angle adjusting unit 704 may adjust the left camera 600 and the right camera according to the distance of the target. Adjust the angle of 602.

According to the present embodiment, the binocular vehicle threshold for angle adjustment may be variously set according to the specifications of the camera or the purpose (the required accuracy) of the stereo vision system.

In general, the distance according to the binocular difference may be expressed as follows.

Where x is the binocular difference, y is the distance to the target, and a, b, c, and d are constants determined by the camera.

)와 임계치(x)의 관계는 다음과 정의될 수 있다. Distance change amount from Equation 1 to the target (

) And the threshold x can be defined as follows.

10 to 11 are views for explaining the angle adjustment process according to the present invention.

In FIG. 10, when the target 900 is located at the first point 910, the target 900 is moved to the initial target 1000 using a virtual window (first virtual window) located at a distance A1 from the baseline 800. Assume that the distance d1 can be measured accurately.

When the target 1000 moves from the first point 1010 to the second point 1012 as shown in FIG. 11, the binocular difference on the first virtual window becomes large. The binocular difference calculator 700 calculates the binocular difference according to the change in the distance of the target 1000, and the distance calculator 702 calculates the distance to the target 1000 according to the calculated binocular difference. Here, the distance to the target calculated based on the first virtual window may be an estimated distance A2.

On the other hand, the angle adjusting unit 704 determines whether the binocular difference calculated by the binocular difference calculator 700 exceeds a preset threshold, and when the binocular difference exceeds a preset threshold in accordance with the movement of the target 1000, the left side is left. The angles of the camera 600 and the right camera 602 are adjusted.

In adjusting the angle, the angle adjusting unit 704 adjusts the angles of the left camera 600 and the right camera 602 such that the virtual window is located at the estimated distance A2 of the target 900.

As shown in FIG. 11, when the distance of the virtual window is farther than the first, the left and right cameras 600 and 602 may be adjusted at an angle smaller than the initial angle with respect to the baseline 800.

According to the present embodiment, the angles of the left camera 600 and the right camera 602 corresponding to the distance of the virtual window may be calculated in real time or stored in a table form, and the angle adjuster 704 may change the virtual window. Adjust the angle to fit the distance.

Subsequently, the binocular difference calculator 700 calculates the binocular difference of the target in the virtual window (second virtual window) located on the changed distance, and the distance calculator 702 uses the calculated binocular difference to target 1000. Calculate the distance to.

As described above, when the distance of the target changes, accurate distance measurement to the target is possible by changing the position of the virtual window and adjusting the angle accordingly.

12 is a diagram illustrating pixel planes of a virtual window and left and right cameras.

Referring to FIG. 12, the pixel planes of the left and right cameras 600 and 602 according to the present exemplary embodiment may be defined based on the point where the virtual window meets the vertical line N of each camera, and according to the position of the virtual window. The relative pixel plane may vary in size. In this case, each pixel plane may be divided into a positive pixel plane (+ pixel) and a negative pixel plane (-pixel) with respect to the virtual window with respect to the center. In this case, the positive pixel plane is a pixel plane located between the camera and the virtual window, and the negative pixel plane is a pixel plane deviating upward of the virtual window.

FIG. 13 illustrates a projection from a positive pixel plane to a virtual window according to an exemplary embodiment of the present invention.

FIG. 13 illustrates a positive pixel plane of the right camera, and may be similarly applied to the left camera.

In FIG. 13, x is an amount of change in the x-axis position when projection is made from the pixel plane to the virtual window, N is a separation distance from the camera to an orthogonal viewing distance, A is a separation distance from the baseline to the virtual window, and G is The tilt angle of the camera relative to the baseline, dD is the distance from the center of the orthogonal viewing distance to the target T, y is a variable for obtaining Q, Q is the target image and the virtual window in the pixel plane of the camera. The distance to the point where the target intersects, J means the resolution. When the resolution is 640 * 320, J is 640 horizontal and 320 vertical.

According to the present exemplary embodiment, the image of the target T positioned on the positive pixel plane is projected onto the virtual window for distance measurement, and the binocular difference in the virtual window with respect to the target may be calculated by knowing the projected position.

The projected position may be represented by two-dimensional coordinates, and FIG. 12 is a view for explaining a process for determining a value of x-coordinate among them, and obtaining y-coordinate may be equally applied.

The x coordinate may be calculated through Equation 3 below.

Here, Q is calculated as in Equation 4 below.

In addition, y is calculated as shown in Equation 5 below.

FIG. 14 illustrates a projection from a negative pixel plane to a virtual window according to an embodiment of the present invention.

FIG. 14 illustrates a negative pixel plane of the right camera, and may be similarly applied to the left camera.

The x coordinate projected onto the virtual window in the negative pixel plane is the same as Equation 3, except that a y value for obtaining Q may be expressed as follows.

Referring to FIG. 8, the relationship between the distance A to the virtual window and the angle G of the camera may be expressed as follows.

B is the distance between the left camera 600 and the right camera 602, a means the viewing angle of each camera.

As described above, when the image of the target is obtained using the left and right cameras, the image is projected onto the virtual window at the current angle, and when the coordinates at the projected position are obtained, the binocular difference of the target on the virtual window is calculated. This allows for accurate measurement of the distance to the target.

15 is a flowchart illustrating a distance measuring process according to an embodiment of the present invention.

Referring to FIG. 15, the controller 604 obtains an image for a target from the left and right cameras 600 and 602 (step 1500), and projects the target image into a virtual window set for the current left and right cameras 600 and 602 (1502). .

 Thereafter, the controller 604 calculates coordinates on the target projected onto the virtual window (step 1504), and calculates binocular difference by the left and right cameras using the calculated coordinates (step 1506).

Next, the controller 604 calculates the distance to the target using the calculated binocular difference (step 1508).

On the other hand, the controller 604 determines whether the calculated binocular difference exceeds a threshold (step 1510).

If it is determined that the binocular difference does not exceed the threshold, the controller 604 determines the distance calculated in step 1508 as the distance to the target (step 1512).

On the other hand, if the binocular difference exceeds the threshold in step 1510, the control unit 604 calculates the angle of the left and right cameras for moving the virtual window to the estimated distance using the distance calculated in step 1508 as the estimated distance (step 1514). ).

Thereafter, the controller 604 drives a motor or the like to control the angle of the left and right cameras to be adjusted (step 1516).

As described above, after the angle adjustment of the left and right cameras is performed, the controller 604 may recalculate the distance to the target based on the moved virtual window by repeating the steps after the operation 1500.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and those skilled in the art will be able to make various modifications, changes, and additions within the spirit and scope of the present invention. Additions should be considered to be within the scope of the following claims.

Claims (11)

A distance measuring method using a cross-type stereo vision system including left and right cameras,
(a) projecting a target on a pixel plane of the left and right cameras into a virtual window, wherein the virtual window is defined as a virtual plane connecting a point where the viewing angle boundary lines of the left and right cameras meet. -;
(b) calculating binocular difference by left and right cameras on the projected target; And
and (c) calculating a distance between the target and the baseline, the baseline on which the left and right cameras are arranged, using the calculated binocular difference. The method of claim 1,
Determining whether the calculated binocular difference exceeds a preset threshold;
If the calculated binocular difference exceeds the threshold, adjusting the angle of the left and right cameras so that the virtual window is positioned at an estimated distance corresponding to the calculated binocular difference. The method of claim 2,
The angle adjusting step is performed using the following equation.
[Mathematical Expression]

Where G is the angle of the left and right cameras and the baseline, a is the viewing angle of the left and right cameras, A is the distance from the baseline to the virtual window, and B is the distance of the left and right cameras. The method of claim 2,
After the angle adjustment of the left and right cameras, the steps (a) to (c) is repeatedly performed. The method of claim 1,
The virtual window is a distance measuring method defined as a virtual plane connecting the point where the viewing angle boundary line in the same direction of the left and right cameras meet. The method of claim 1,
The binocular difference calculation step,
Calculating coordinates on the target projected onto the virtual window; And
And calculating the binocular difference on the target using the calculated coordinates. The method according to claim 6,
The pixel plane is divided into a positive pixel plane (+ pixel) and a negative pixel plane (-pixel) with respect to the virtual window with respect to the center. As a cross type stereo vision system,
Left and right cameras; And
Computing binocular disparity in a virtual window with respect to a target obtained from the left and right cameras, and using the calculated binocular difference, a baseline between the baseline and the target, the baseline on which the left and right cameras are arranged. Includes a control for calculating the distance,
The virtual window is a cross-type stereo vision system is a virtual plane connecting the points where the viewing angle boundary line of the left and right cameras overlap. 9. The method of claim 8,
The control unit,
And determining whether the calculated binocular difference is greater than a preset threshold, and controlling the angle of the left and right cameras to be adjusted when the calculated binocular difference is greater than the threshold. 10. The method of claim 9,
The control unit,
Cross-type stereo vision system for measuring the distance to the target again using the binocular difference in the modified virtual window after the left and right camera angle is adjusted. 9. The method of claim 8,
The control unit,
And projecting the binocular difference in the virtual window after projecting the target image onto the virtual window from the pixel plane.

Images