JP6202240B2 - Overhead image presentation device - Google Patents

Description

  The present invention relates to a bird's-eye view image presentation device, and more particularly, to a bird's-eye view image presentation device that converts an image captured by a vehicle-mounted camera into a bird's-eye view image viewed from a virtual viewpoint for driving support and the like and displays the image on a monitor.

  In recent years, for the purpose of driving assistance when the vehicle is moving backward, an overhead image presentation device that presents a bird's-eye view image looking down from above the vehicle to the driver is becoming popular. The bird's-eye view image presentation device converts the image captured by the in-vehicle camera (back camera) mounted on the rear of the vehicle, and creates a bird's-eye view image that virtually looks down on the target parking frame and the rear end of the vehicle from the viewpoint above the vehicle And has a function of displaying the created overhead image on the monitor and presenting it to the driver.

It is desirable that the function of creating and presenting an overhead image for the purpose of driving support satisfies the following two points.
1. 1. Enlarge the peripheral display field of view with a size and resolution that allows the driver to see objects around the vehicle to eliminate blind spots. Displaying objects drawn on the ground virtually, such as parking frames and objects originally drawn on the ground, guide lines, etc. without deforming them (for example, displaying straight lines as straight lines)

As such a bird's-eye view image presenting apparatus, there are apparatuses described in Japanese Patent Application Laid-Open Nos. 2008-141643 and 2005-167638.
In Japanese Patent Application Laid-Open No. 2008-141634, a virtual three-dimensional surface connecting a foreground surface and a far-field surface is set, and by using viewpoint conversion using the virtual three-dimensional surface, image data captured by an in-vehicle camera is used for near and far views. A bird's-eye view image presentation device that creates and displays the two display data is described.
Japanese Patent Laid-Open No. 2005-167638 obtains an image of a 360-degree field of view and converts it into image data overlooking the road surface including a part of the vehicle near the center of the field of view, and the vehicle away from the center of the field of view. A bird's-eye view image presentation device that converts the image data into the image data viewed in the horizontal direction and displays two image data in the bird's-eye view and the horizontal direction is described.

JP 2008-141643 A JP 2005-167638 A

However, in the apparatus described in Japanese Patent Application Laid-Open No. 2008-141463, virtual projection planes are created separately for the foreground projection plane and the foreground projection plane, and the boundary between the foreground projection plane and the foreground projection plane is defined. Are connected. Further, in the apparatus described in Japanese Patent Laid-Open No. 2005-167638, a virtual projection plane is created separately for the overhead view projection plane and the horizontal projection plane, and the overhead view projection plane and the horizontal projection plane are Join the boundary.
In other words, in the apparatuses described in Japanese Patent Application Laid-Open Nos. 2008-141634 and 2005-167638, the virtual projection plane is created separately on two projection planes, and the boundary between the bottom surface and the wall surface is created. Are combined. For this reason, mismatching may occur at the boundary between the two projection planes, which gives the driver a sense of incongruity. In addition, in order to avoid inconsistencies, the process of creating a virtual projection plane becomes complicated.

  The present invention can seamlessly display a bird's-eye view image so as not to give the driver a sense of incongruity, can easily set a virtual projection plane, and expands the display range to reduce blind spots. An object of the present invention is to provide a bird's-eye view image presentation device that can display an object drawn on the ground without being deformed and can suppress the curvature of a distant landscape.

The present invention includes a plurality of imaging means for imaging a vehicle periphery, an image conversion means for converting an image captured by the imaging means into a bird's-eye view image looking down from a virtual viewpoint above the vehicle, and the image conversion means. In a bird's-eye view image display device comprising a display means for displaying a bird's-eye view image, the virtual projection plane for projecting the bird's-eye view image is horizontal to the plane and at an arbitrary height with the vehicle placed on the plane. When the virtual projection plane is cut by the horizontal plane, the horizontal cut plane of the virtual projection plane is represented by a super-elliptical shape, and the vertical plane that passes through the center of the super-ellipse and is perpendicular to the plane and in any orientation a three-dimensional curved vertical cutting plane of the virtual projection plane is represented by a bathtub curve when cut a virtual projection plane by, and is represented by a single formula, the overhead image is the hyperelliptic long radius Other splits a short radial position, the image captured by the plurality of imaging means, characterized in that bind with the dividing plane.

The virtual projection plane according to the present invention is a solid curved surface in which the horizontal cut surface is represented by a super-elliptical shape and the vertical cut surface is represented by a bathtub curve, and thus extends obliquely upward from the planar bottom surface and the periphery of the bottom surface. It consists of a wall. For this reason, this invention can display without expanding the display range and reducing the blind spot and without deforming the object drawn on the ground.
The virtual projection plane according to the present invention suppresses the curvature of a distant landscape because the cut surface formed by an arbitrary plane that is parallel to the bottom surface and located between the bottom surface and the virtual viewpoint is an enlarged shape of the bottom surface. Can do.
Since the virtual projection surface of the present invention is a curved surface represented by a single mathematical expression, it is possible to seamlessly display a bird's-eye view image so as not to give the driver a sense of incongruity. Can be set.

FIG. 1 is a system configuration diagram of an overhead image presentation device. (Example) 2A is a plan view of a virtual projection plane represented by an elliptical shape and a bathtub curve, and FIG. 2B is a diagram of the virtual projection plane represented by an elliptical shape and a bathtub curve as viewed from the Y-axis direction. 2 (C) is a view of the virtual projection plane represented by an elliptical shape and a bathtub curve as seen from the X-axis direction, and FIG. 2 (D) is a view of the virtual projection plane represented by an elliptical shape and a bathtub curve as seen from the Z-axis direction. It is a figure. (Example) FIG. 3 is a diagram showing a vertical cut surface of a virtual projection plane represented by a bathtub curve to which the Arrhenius chemical reaction formula is applied. (Example) FIG. 4 is a diagram showing mathematical expressions representing a virtual projection plane in which the horizontal cut surface is elliptical and the vertical cut surface is represented by a bathtub curve. (Example) FIG. 5A is a plan view of a virtual projection surface having a similar elliptical shape regardless of the height, and FIG. 5B is a perspective view of the virtual projection surface having a constant similar elliptical shape regardless of the height. (Example) 6A is a view showing an overhead image in which the curvature of the ellipse in the long radius direction is reduced, and FIG. 6B is a view showing an overhead image in which the curvature of the ellipse in the long radius direction is increased. (Example) FIG. 7 is a diagram showing a virtual projection surface having a curved surface with a large curvature all around. (Example) 8A is a plan view of a virtual projection plane represented by a super-elliptical shape and a bathtub curve, and FIG. 8B is a diagram of the virtual projection plane represented by a super-elliptical shape and a bathtub curve viewed from the Y-axis direction. FIG. 8C is a view of the virtual projection plane represented by the super elliptical shape and the bathtub curve from the X-axis direction, and FIG. 8D is the virtual projection plane represented by the super elliptical shape and the bathtub curve. It is the figure seen from the axial direction. (Example) FIG. 9 is a diagram illustrating a mathematical expression representing a virtual projection plane in which a horizontal cut surface is a super-elliptical shape and a vertical cut surface is represented by a bathtub curve. (Example) FIG. 10 is a diagram showing a virtual projection plane in which the front and rear, left and right surfaces are Gabriel Lame curves with a small curvature. (Example) FIG. 11A is a plan view of a virtual projection surface having a constant super-elliptical shape regardless of the height, and the bottom surface is a super-elliptical shape regardless of the height, and FIG. It is a perspective view of a virtual projection surface of a certain similar super-elliptical shape. (Example) FIG. 12 is a view showing a bird's-eye view image by a virtual projection plane having a bottom surface with a super-elliptical shape. (Example) FIG. 13 is a diagram showing a change in the height direction of the virtual projection plane using the Arrhenius chemical reaction formula, the sigmoid curve, and the hyperbolic function tanh. (Example) FIG. 14 is an explanatory diagram of a situation where the vehicle is moved backward and moved to the parking frame. (Example) FIG. 15 is a view showing an overhead image at position A in FIG. (Example) FIG. 16A is a diagram illustrating an overhead image at a position B in FIG. 14, and FIG. 16B is a diagram illustrating background movement of a corner of the overhead image at a position B in FIG. (Example) 17A shows a bird's-eye view image having a super-elliptical bottom surface having a certain order, and FIG. 17B shows a bird's-eye view image having a super-elliptical bottom surface having a different order from FIG. 17A. FIG. (Example) 18A is a view showing an overhead image in which the left side of the screen divided into left and right is an elliptical bottom surface and the right side is a super elliptical bottom surface, and FIG. 18B is an overhead image of FIG. 18A. It is a figure explaining the background movement of a corner | angular part. (Example) FIG. 19A is a diagram illustrating an image obtained by extracting and enlarging a part of a conventional overhead image, and FIG. 19B is a diagram illustrating an image captured by the camera and an overhead image. (Example) FIG. 20A is a diagram illustrating the relationship of the height position of the virtual viewpoint with respect to the vehicle, and FIG. 20B is a diagram illustrating an enlarged image obtained by extracting a part of the overhead image. (Example) FIG. 21A is a diagram for explaining the field of view when the virtual viewpoint is lowered with respect to the vehicle, and FIG. 21B is an enlarged image obtained by extracting a part of the overhead view image from the virtual viewpoint lowered with respect to the vehicle. FIG. 21C is a diagram for explaining the deformation of the image when the X-axis direction is reduced with respect to the vehicle. (Example) 22A is a diagram showing an image obtained by extracting and enlarging a part of a conventional bird's-eye view image, and FIG. 22B is a diagram showing a bird's-eye view image by a virtual projection plane represented by a super-elliptical shape and a bathtub curve. 22 (C) is a diagram showing an overhead image on a virtual projection plane in which the degree of the super ellipse is increased. (Example) FIG. 23 is a diagram showing a virtual projection plane obtained by combining two projection planes having different orders of mathematical expressions representing the super-elliptical shape in the front and rear. (Example) FIG. 24 is a system configuration diagram of the overhead image presentation device. (Example) FIG. 25A is a diagram showing an image obtained by combining the foreground image captured by the foreground camera and the background image captured by the background camera, and FIG. 25B is a virtual image having a large order of the foreground image and the background image. FIG. 25C is a diagram showing a bird's-eye view image obtained by converting a foreground image and a background image using a small-order virtual projection surface. (Example) FIG. 26 is a diagram showing a virtual projection plane obtained by combining four projection planes having different orders of mathematical expressions representing a super-elliptical shape in front, rear, left, and right. (Example) FIG. 27A is a diagram showing a conversion table obtained by dividing a virtual projection plane having a large order of a mathematical expression representing a super-elliptical shape into four parts, and FIG. 27B shows a virtual projection plane having a small order of a mathematical expression representing an elliptical shape. It is a figure which shows the conversion table divided | segmented into four. (Example) FIG. 28 is a view showing a bird's-eye view image obtained by combining images converted by four projection planes having different orders of mathematical expressions representing a super-elliptical shape in front, rear, left and right. (Example)

  Embodiments of the present invention will be described below with reference to the drawings.

1 to 28 show an embodiment of the present invention. As shown in FIG. 1, the overhead image presentation device 2 of the vehicle 1 includes a camera 3 that is an imaging unit that captures the surroundings of the vehicle 1, and an overhead view obtained by looking down the image Gc taken from the virtual viewpoint Sv above the vehicle. The image conversion means 4 which converts into the image Gp, and the monitor 5 of the display means which displays the bird's-eye view image Gp converted by the image conversion means 4 are provided. The camera 3 is attached to the rear part of the vehicle 1 and images the rear of the vehicle 1. The image conversion means 4 is provided in the processing means 6 of the overhead image presentation device 2.
The processing means 6 is connected to the camera 3 and the monitor 5, and is connected to a reverse confirmation switch 7, an overhead image display selection switch 8, and a steering angle sensor 9 of the steering angle detection means. The reverse confirmation switch 7 activates the overhead view image presentation device 2 to display the overhead view image Gp on the monitor 5. The overhead image display selection switch 8 selects and switches the image to be displayed on the monitor 5 between the image Gc captured by the camera 3 and the overhead image Gp. The steering angle sensor 9 detects the steering angle of the steering handle of the vehicle 1.
As shown in FIGS. 2B, 2C, and 2D, the virtual viewpoint Sv is set at an imaging position of the virtual camera 10 arranged so as to look down from above the vehicle 1. When the vehicle 1 is placed on the plane 11, the bird's-eye view image Gp looks down from the virtual viewpoint Sv of the virtual camera 10 disposed above the vehicle 1, the image Gc captured by the camera 3 attached to the rear portion of the vehicle 1. It is the image projected on the virtual projection plane Ps set to the direction.
The virtual projection plane Ps has an elliptical shape in plan view as shown in FIGS. The virtual projection plane Ps, as shown in FIG. 3, Arrhenius in the height _{y e} direction of setting a virtual projection plane Ps (Arrehnius) Chemical reaction formula (hereinafter, referred to as "Arrhenius equation".) Applying, oval It consists of a solid curved surface (bathtub projection plane) represented by a shape and a bathtub curve, and is composed of a bottom surface 12 on the plane 11 and a wall surface 13 extending obliquely upward from the periphery of the bottom surface 12.

As shown in FIG. 4, the coordinate system of the virtual projection plane Ps is [x _e , y _e , z _e ], the ratio n of the major radius a to the minor radius b of the bottom surface 12, and Y _e = Y _e0 on the bottom surface 12. = 0, the point [x _e , y _e , z _e ] = [x _e0 , 0, z _e0 ] (the shape of the bottom surface 12) up to the periphery (wall surface 13) of the bottom surface 12 is set to the plane 11 at the height y _e On the other hand, the model is modeled by an elliptical general expression represented by a major radius a and a minor radius b of the ellipse horizontally cut (formula 1), and developed by b = n · a, with “major radius a as a parameter. A virtual projection plane Ps of a three-dimensional curved surface represented by a model formula (Formula 2) correlated with a height y _e based on the Arrhenius formula.
As shown in FIG. 5, the virtual projection plane Ps represented by this model formula (Formula 2) is obtained by changing the curvature in the major radius direction (X direction) of the ellipsoid cut horizontally with respect to the plane 11. to reduce the curvature of the (Z-direction), by curvature constant similar elliptical upward regardless height y _e, as shown in FIG. 6, relative to the rear of the distant landscape of the vehicle 1, curved An image in which straightness is ensured while suppressing deformation can be displayed.
However, when the shape of the bottom surface 12 of the virtual projection plane Ps is an elliptical shape in which the curvature in the short radius direction (Z direction) of the ellipsoid cut horizontally with respect to the plane 11 is reduced, The curvature in the X direction becomes large, and it becomes difficult to achieve both the effects of “securing the left and right visual field” and “reducing the curvature and improving the straightness of the distant landscape behind the vehicle 1”. That is, as shown in FIG. 7, when the shape of the bottom surface 12 of the virtual projection plane Ps is an elliptical shape, the entire circumference of the wall surface 13 is a curved surface having a large curvature, and the curved deformation is strong.

Therefore, this overhead image presentation device 2 sets the virtual projection plane Ps on which the overhead image Gp is projected as follows.
As shown in FIGS. 8B, 8 </ b> C, and 8 </ b> D, the virtual projection plane Ps is horizontal with respect to the plane 11 and positioned at an arbitrary height with the vehicle 1 placed on the plane 11. When the virtual projection plane Ps is cut by the horizontal plane Ph, the horizontal cut plane of the virtual projection plane Ps is expressed in a super-elliptical shape, passes through the center M of the super-ellipse, and is perpendicular to the plane 11 and has an arbitrary orientation. When the virtual projection plane Ps is cut by the vertical plane Pv, the vertical cut plane of the virtual projection plane Ps is a solid curved surface (super elliptical bathtub projection plane) represented by a bathtub curve (failure rate curve), And it is represented by one mathematical expression (see FIG. 9).
As shown in FIGS. 8A to 8D, the virtual projection plane Ps has a super-elliptical shape in plan view.
As shown in FIG. 9, the virtual projection plane Ps has a coordinate system [x _e , y _e , z _e ] of the virtual projection plane Ps, a ratio n between the major radius a and the minor radius b of the bottom surface 12, Instead of the general formula (formula 2) of the ellipse applying the Arrhenius formula of FIG. 4, the conversion formula (kth power) can be adjusted by the following formula. When Y _e = Y _e0 = 0 on the bottom surface 12 of the super-elliptical shape, the point [x _e , y _e , z _e ] = [x _e0 , 0, z _e0 ] (bottom surface 12) to the periphery of the bottom surface 12 (wall surface 13). ) Is defined by a general formula of the super ellipse (formula 3), and developed by b = n · a to obtain one mathematical formula (formula 4) representing the solid curved surface represented by the superelliptical shape and the bathtub curve. .
In other words, the ellipse formula is replaced by the super-elliptical shape (rounded square shape) proposed by Gabriel Lame (Gabriel Lame's super-elliptical formula), and expressed by the super-elliptical shape and bathtub curve. One mathematical expression representing a solid curved surface is obtained. Gabriel Lame's super-elliptic formula is that the ellipse gets closer to the super-ellipse (rounded rectangle) as the order k of the model formula increases. The long radius and short radius are common. The virtual projection plane Ps: Y _e = A · (−1 + EXP [B · (a)]) using the long radius a in the cross section as a parameter is set by the one mathematical formula.
As shown in FIGS. 10 and 11, the virtual projection plane Ps has a cross section obtained by cutting the shape of the bottom surface 12 horizontally with respect to the plane 11 to a super elliptical shape (rounded square shape), and the shape of the wall surface 13 is high. since the y _e in regardless of curvature is constant for similar super elliptical shape, as shown in FIG. 12, can be maintained behind the straightness of the vehicle 1, it can be avoided curvature of distant scenery.

As described above, the virtual projection plane Ps of the overhead view image presentation device 2 is a solid curved surface in which the horizontal cut surface is represented by a super-elliptical shape and the vertical cut surface is represented by a bathtub curve. It comprises a bottom surface 12 and a wall surface 13 extending obliquely upward from the periphery of the bottom surface 12. For this reason, this bird's-eye view image presentation device 2 can display the object displayed on the ground without deforming it while expanding the display range to reduce the blind spot.
Since the virtual projection plane Ps of the overhead view image presentation device 2 is a shape obtained by enlarging the shape of the bottom surface 12 with a cut surface formed by an arbitrary plane parallel to the bottom surface 12 and positioned between the bottom surface 12 and the virtual viewpoint Sv. The curvature of the distant landscape can be suppressed.
Since the virtual projection plane Ps of the overhead image presentation device 2 is a curved surface represented by one mathematical expression (Equation 4), the overhead image Gp may be displayed seamlessly so as not to give the driver a sense of incongruity. In addition, the virtual projection plane Ps can be easily set.
In the formula for the height y _e direction of the virtual projection plane Ps, it has been applied Arrhenius equation to apply parametric a (sectional length radius), as shown in FIG. 13, in addition to the Arrhenius equation, parametric A similar bathtub curve can be obtained by applying the sigmoid curve to which a (cross-section radius) is applied and the hyperbolic function tanh. However, when setting the height y _e direction of the curved surface of the virtual projection plane Ps sigmoidal curve, the hyperbolic function tanh is the limit point (convergence point) is generated both in the height y _e direction. Therefore, in the case of the bird's-eye view image Gp, it is necessary to set parameters so that the convergence height is higher than the installation height of the virtual camera 10, that is, the height position of the virtual viewpoint Sv.

As shown in FIG. 14, when the vehicle 1 is moved straight back and forth in the vicinity of the position A in the situation where the vehicle 1 is moved to the parking frame (guideline) 14 as shown in FIG. By displaying the bird's-eye view image Gp converted by the virtual projection plane Ps composed of a three-dimensional curved surface represented by a bathtub curve, as shown in FIG. 15, securing of the visual field (reducing blind spots) and curving deformation of the screen display are achieved. Improvements can be made.
On the other hand, as shown in FIG. 14, the bird's-eye view image presentation device 2 is configured to turn the vehicle 1 around the position B in a situation where the vehicle 1 is moved to the parking frame (guideline) 14 and turn back in FIG. As shown in FIG. 16B, the background image is the vehicle 1 in the vicinity of the super-elliptical corner portion (cornered corner) of the overhead image Gp displayed on the monitor 5. It moves with a trajectory close to a right angle that does not match the movement of. Such movement of the background image may give an uncomfortable feeling to the driver.
By the way, as described above, the super-elliptical formula of Gabriel Lame has a feature that “the ellipse and the super-ellipse have the same vertical and horizontal radii (major radius and minor radius) regardless of the order”. The order k, the major radius a, and the minor radius b of one mathematical formula (Formula 4) representing the super-elliptical shape shown in FIG. 9 are independent parameters, and the magnitudes of the values do not affect each other. Therefore, even in the bottom surface 12 of the different multipliers (order k) or the wall surface 13, (bathtub section), Bath coordinates _{[x e, y e, z} e] y e axis in [0, 90, 180, 270 ] In the deg position, an image is always formed at the same rounding position caused by the major radius a and the minor radius b.
Therefore, as shown in FIGS. 17A and 17B, the image conversion means 4 divides the overhead view image Gp into left and right parts, and has different degrees k on the left and right sides of the overhead view image Gp, and has a common major radius and minor radius. A plurality of projection planes (bathtub projection planes) are prepared in advance, and based on the steering angle of the steering wheel detected by the steering angle sensor 9 during the turning of the vehicle 1, as shown in FIG. By switching the virtual projection plane Ps that combines the projection planes, as shown in FIG. 18B, it is possible to bring the background movement near the corner portion of the super-elliptical shape closer to a natural display.
In the actual switching process of the virtual projection plane Ps, an image conversion table (offset table) for performing image conversion processing in advance is a Gabriel-Lame multiplier (order) in units of the left half and right half sizes of the screen of the monitor 5. k) patterns are prepared, and tables of the same multiplier (order k) are combined during straight reverse, and tables of different multipliers (order k) are combined according to the steering angle during reverse turning. Thereby, during turning backward, it is possible to display a bird's-eye view image Gp along the movement of the vehicle 1 by switching to a combination of tables that can realize natural movement of the background image along the turning of the vehicle 1.

Thus, since the image conversion means 4 changes the order k of the projection surface represented by a super ellipse based on the state of the vehicle 1, it can suppress a sense of discomfort given to the driver. Specifically, the overhead view image presentation device 2 includes a steering angle sensor 9 that detects the steering angle of the vehicle 1, and the image conversion means 4 calculates the degree k of the super ellipse based on the steering angle detected by the steering angle sensor 9. In order to change, it can display so that a background may change naturally according to the turning of the vehicle 1 during the turning of the vehicle 1, and it can prevent a driver from feeling uncomfortable.
Further, the image conversion means 4 divides the overhead image Gp into left and right and changes the order k of the left and right image projection planes based on the steering angle detected by the steering angle sensor 9, so that the vehicle 1 is turning. Can be displayed so that the background changes naturally with the turning of the vehicle 1 so as not to give the driver a sense of incongruity. Can be reduced.
In addition, since the wall surface 13 constituting the virtual projection plane Gp has a super-elliptical shape, this overhead view image presentation device 2 is configured so that no deviation occurs at the joint portion of the image even if the order of the left and right images is changed. Can do.

By the way, in the conventional bird's-eye view image based on the ground projection plane, as shown in FIG. 19 (A), only the “region with small display deformation” is extracted from the converted image, and the process of enlarging it according to the screen size of the monitor is performed. It was. In this case, in the process of enlarging in accordance with the screen size of the monitor, the model can be defined as a state where the virtual camera is installed at a low position and the vicinity of the ground is photographed. As a result, the display size of the parking frame (guideline) 14 displayed on the screen is large, and it is easy to see the specification of the parking assistance image for elderly people who are weak in visual acuity.
On the other hand, in the wide-range overhead view image with the virtual projection plane Ps represented by the above-mentioned super-elliptical shape and bathtub curve, the virtual camera 10 is installed upward and the position of the virtual viewpoint Sv is raised, so FIG. As shown in FIG. 4, the parking frame (guideline) 14 and the like have a relatively small display size with respect to the screen, and it is assumed that the parking frame (guideline) 14 is slightly difficult to view.
Therefore, in order to set a wide range overhead view image that displays the display size near the parking frame (guideline) 14 shown in the wide range overhead view image closer to the conventional overhead view image, the virtual camera 10 is installed below. The virtual viewpoint Sv must be set to a low position.
FIG. 20 shows a converted image in which the virtual viewpoint Sv is set low for the purpose of enlarging the display size near the parking frame 14. As shown in FIG. 20A, when the virtual viewpoint Sv is set low, as shown in FIG. 20B, the left and right display range on the converted image is a conventional overhead view image by ground projection (FIG. 19B). Since there is almost no difference from)), the advantage of using the stereoscopic projection surface is lost.
Therefore, in order to enlarge the left and right fields of view, as shown in FIG. 21A, the value of the Rx radius of the X-axis method of the bottom surface 12 of the virtual projection plane Ps represented by the super-elliptical shape and the bathtub curve is reduced. By performing the process, that is, the process of enlarging the ratio n between the long radius a and the short radius b, the left and right display range can be expanded as shown in FIG. However, in the image of FIG. 21 (C), the left and right display range can be enlarged and the blind spots can be reduced as compared with the conventional overhead view image (FIG. 21 (B)). Since the linearity of the frame 14 is attracted to the three-dimensional curved surface and is curved, and the overhead view image is deformed into a letter C having different parallelism (constricted toward the distance), the parking support effect is reduced. become.
As described above, regarding the overhead image Gp with the virtual viewpoint Sv set at a low position, the resolution near the ground on the display is improved on the projection plane in which the features of the hemisphere and the ellipsoid are reflected in the profile elements of the projection plane. Therefore, the influence of the curvature due to the projection surface curvature is more strongly reflected in the converted image. In addition, when trying to perform a bird's-eye view process on a projection surface having a curved surface with respect to the display image of the square monitor 5, it is difficult to evenly correct the upper corner portion (upper left corner and upper right corner portion) of the screen, which is also uncomfortable. Display deformation occurs.

Regarding such a problem, with respect to the virtual projection plane Ps (bathtub projection plane) having the bottom surface 12 based on the super-elliptical shape proposed by Gabriel Lame, the display image of the square monitor 5 has a square profile as an element. Therefore, it is possible to sufficiently cope with the curved deformation and the complementation of the two corners at the top of the screen.
In view of this, the overhead view image presentation device 2 is configured so that when the position of the virtual viewpoint Sv is lowered by the image conversion means 4, the virtual projection plane based on the conventional elliptical shape shown in FIG. ), The length of the virtual projection plane Ps having the bottom surface 12 based on the super-elliptical shape in the lateral direction (X-axis direction) of the vehicle 1 is shortened, and the order of the super-ellipse is represented as shown in FIG. Increase k.
As described above, when the position of the virtual viewpoint Sv is lowered, the image conversion unit 4 shortens the length of the virtual projection plane Ps in the lateral direction (X-axis direction) of the vehicle 1 and increases the degree k of the super ellipse. By doing this, even if the position of the virtual viewpoint Ps is lowered, the left and right display ranges can be secured wider than the conventional image shown in FIG. Can be converted into an overhead image Gp that is easier to park.

The above-described bird's-eye view image presentation device 2 converts the rear image of the vehicle 1 captured by one camera 3 into the bird's-eye view image Gp and displays it on the monitor 5, but the images are captured by a plurality of cameras 3 attached to the vehicle 1. An image around the vehicle 1 can be converted into an all-around bird's-eye view image and displayed on the monitor 5. In this case, as shown in FIG. 23, the origin of the coordinate system [x _e , y _e , z _e ] of the virtual projection plane Ps is desirably set near the center position of the vehicle 1 in the world coordinate system.
For example, as shown in FIG. 24, the bird's-eye view image presentation device 2 that presents a bird's-eye view image of the entire circumference of the vehicle has a foreground camera 3 f that captures a landscape in front of the vehicle 1 and a background that captures a landscape in the rear of the vehicle 1. The camera 3b, the image conversion means 4 for converting the foreground image Gcf captured by the foreground camera 3f and the background image Gcb captured by the background camera 3b into the bird's-eye view image Gpw around the entire vehicle, and a monitor for displaying the bird's-eye view image Gpw And 5. The processing means 6 of the bird's-eye view image presentation device 2 is connected to the cameras 3f and 3b and the monitor 5, and is connected to the reverse confirmation switch 7, the bird's-eye view image display selection switch 8, and the steering angle sensor 9 of the steering angle detection means. doing.
As shown in FIG. 25A, the image conversion means 4 inputs the foreground image Gcf picked up by the foreground camera 3f and the foreground image Gcb picked up by the background camera 3b, and combines them with the foreground image Gcf and the foreground image Gcb. Then, as shown in FIG. 25 (B), the image is projected onto a virtual projection plane Ps with the degree k of the super ellipse increased and converted into a bird's-eye view image Gpw around the entire vehicle, or as shown in FIG. 25 (C). The image is projected onto a virtual projection plane Ps having a reduced ellipse order k, converted into a bird's-eye view image Gpw around the entire vehicle, and displayed on the monitor 5.
Accordingly, the overhead image presentation device 2 shown in FIGS. 24 and 25 ensures the linearity of the drawing on the road surface in the vicinity of the host vehicle, such as a parking frame (guideline), for both the front landscape and the rear landscape. Furthermore, by using the side portion of the virtual projection plane Ps (bathtub projection plane), a wider range of distant surrounding scenery can be displayed without a sense of incongruity. Furthermore, also for the all-around bird's-eye view image Gpw obtained by connecting the images Gcf and Gcb of the plurality of cameras 3f and 3b, continuity near the connection boundary between the bottom surface 12 and the side surface 13 of the virtual projection plane Ps is ensured (seamless and seamless image) Can be created).
Note that the overhead image presentation device 2 includes not only the foreground camera 3f and the background camera 3b described above, but also a left view camera 3l that captures a landscape on the left side of the vehicle 1, as shown by a broken line in FIG. A right view camera 3r that captures a landscape on the right side is connected to the processing unit 6, and a left view image Gcl captured by the left view camera 3l and a right view image Gcr captured by the right view camera 3r are connected to the processing unit 6. Can be combined and combined with the foreground image Gcf and the background image Gcb described above, converted into a bird's-eye view image Gpw around the entire vehicle, and displayed on the monitor 5.

Moreover, the overhead image presentation device 2 that converts and presents the surrounding image of the vehicle 1 captured by the plurality of cameras 3 as described above into the all-around overhead image Gpw, divides the overhead image Gpw, and By changing the order k based on the steering angle detected by the steering angle sensor 9, the movement of the all-around image displayed on the monitor 5 while the vehicle 1 is turning can be brought close to a natural display.
As shown in FIG. 26, the overhead image presentation device 2 sets the origin of the coordinate system [x _e , y _e , z _e ] of the virtual projection plane Ps near the center position of the vehicle 1 in the world coordinate system. (A) As shown in (B), the overhead image Gpw is divided into four first to fourth quadrants Q1 to Q4 at the positions of the long radius and the short radius, and a large order for each of the first to fourth quadrants Q1 to Q4. A conversion table T1 (FIG. 27A) for a projection surface having a super-elliptical shape (rectangular rectangle) with k and a conversion table T2 for a projection surface having an elliptical shape with a small order k (FIG. 27B) are converted. The means 4 is prepared in advance. The image conversion means 4 sets the combination of projection planes set in the first to fourth quadrants Q1 to Q4 based on the steering angle of the steering wheel detected by the steering angle sensor 9 while the vehicle 1 is traveling.
For example, when the vehicle 1 is traveling straight, the image conversion means 4 sets all of the first to fourth quadrants Q1 to Q4 to a super-elliptical projection plane with a large degree k shown in FIG. Then, the overhead image Gpw is displayed on the monitor 5. Thereby, the bird's-eye view image Gpw can be displayed in a natural manner with little bending deformation.
On the other hand, when the vehicle 1 is turning, the image conversion means 4 has a super-elliptical projection plane (Fig. 28) with a large degree k on the front inner side (second quadrant Q2) in the turning direction. 27 (A)), the front outer side (first quadrant Q1) in the turning direction is set to an elliptical projection surface (FIG. 27B) with a small order k, and the overhead image Gpw is displayed on the monitor 5 To do. As a result, the bird's-eye view image Gpw can have a natural display with little curved deformation on the inner side in the turning direction, a natural display of the background movement on the outer side in the turning direction, and the background movement in the vicinity of the corner portion of the turning image. It can be close to the natural display.
When the vehicle 1 is turning, as shown in FIG. 28, not only in the first quadrant Q1 and the second quadrant Q2, but also in the third quadrant Q3 and the fourth quadrant Q4 as described above. The third quadrant Q3 is set to an elliptical projection plane with a small degree k (FIG. 27B), and the fourth quadrant Q4 is set to a superelliptical projection plane with a large degree k (FIG. 27A). Then, the overhead image Gpw is displayed on the monitor 5.
That is, an optimal table combination for each of the plurality of cameras 3 is made into a database according to the steering angle, and a dynamic all-around image is created by varying the combination of the conversion tables for each straight movement / turning movement of the vehicle 1. be able to.
Thus, the overhead image presentation device 2 combines the images captured by the plurality of cameras 3 by the image conversion means 4 to generate the overhead image Gpw of the entire vehicle around the vehicle 1, Even when the vehicle 1 is turning, the all-around overhead image Gpw can be displayed on the monitor 5 without causing a gap in the image coupling portion.

  The present invention seamlessly displays a bird's-eye view image so as not to give the driver a sense of incongruity, can easily set a virtual projection plane, expands the display range to reduce blind spots, and is drawn on the ground An object can be displayed without being deformed, and can be applied to a bird's-eye view image presentation device for driving assistance of various vehicles.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Overhead image presentation apparatus 3 Camera 4 Image conversion means 5 Monitor 6 Processing means 7 Backward confirmation switch 8 Overhead image display selection switch 9 Steering angle sensor 10 Virtual camera 11 Plane 12 Bottom surface 13 Wall surface 14 Parking frame (guideline)

Claims (6)

A plurality of imaging means for imaging the periphery of the vehicle, an image conversion means for converting an image captured by the imaging means into an overhead image viewed from a virtual viewpoint above the vehicle, and an overhead image converted by the image conversion means A bird's-eye view image presentation device comprising display means for
The virtual projection plane for projecting the bird's-eye view image is horizontal to the virtual projection plane when the vehicle is placed on a plane and the virtual projection plane is cut by a horizontal plane that is horizontal to the plane and positioned at an arbitrary height. The direction cut surface is represented by a super-elliptical shape,
When the virtual projection plane is cut by a vertical plane that passes through the center of the super ellipse and is perpendicular to the plane and in any orientation, the vertical cut plane of the virtual projection plane is a solid curved surface represented by a bathtub curve, and Represented by a single formula ,
The bird's-eye view image presenting apparatus, wherein the bird's-eye view image is divided at a position of a major radius or a minor radius of the super ellipse, and images taken by the plurality of imaging means are combined on the division plane .   The overhead image presentation apparatus according to claim 1, wherein the image conversion unit changes the order of the super ellipse based on a state of the vehicle.   3. The steering angle detecting means for detecting a steering angle of the vehicle, wherein the image converting means changes the order of the super ellipse based on the steering angle detected by the steering angle detecting means. The overhead image presentation apparatus described. Wherein the image conversion means, an overhead image display device according to claim 3, characterized in that changing the order of the left and right images based on the steering angle detected by the steering angle detecting means. Wherein the image conversion means, an overhead image display device according to claim 4, characterized in that to produce a vehicle entire circumference of the overhead image around the vehicle.   3. The overhead image according to claim 2, wherein when the position of the virtual viewpoint is lowered, the image conversion unit shortens the length of the virtual projection plane in the lateral direction of the vehicle and increases the order of the super ellipse. Presentation device.