DE102014200272A1 - Dielectric lens for radar sensors - Google Patents

Abstract

Dielectric lens for radar sensors, comprising a lens body (12) having at least one radar wave refracting lens surface (14) defined by a function h (x, y) in a rectangular coordinate system having coordinate axes X, Y and Z, where h (x, y) for each point of the lens surface (14) indicates the value of the z-coordinate as a function of the x and y coordinates, characterized in that if a Y-section of the lens surface (14) for a given value x Given the x-coordinate by the function h _x (y): = h (x, y), the lens surface (14) at least two Y-sections (20, 22), which are independent of each other in the sense that the a Y-cut (22) determined neither due to a symmetry of the lens surface by the other Y-section (20) nor by displacement along the z-axis in the other Y-section (20) can be converted.

Description

The invention relates to a dielectric lens for radar sensors, in particular for motor vehicles, having a lens body which has at least one lens surface which breaks the radar waves and is defined by a function h (x, y) in a rectangular coordinate system with coordinate axes X, Y and Z, where h (x, y) for each point of the lens surface indicates the value of the z coordinate as a function of the x and y coordinates.

Dielectric lenses for radar sensors have the purpose of breaking the radar waves so that the radiation emitted by transmitting antenna elements of the radar sensor is focused and, conversely, the radiation reflected by the ordered objects is focused on receiving antenna elements.

Commonly used are rotationally symmetrical lenses. For these lenses, the function h (x, y) has the form: h (x, y) = h (r), where r is the radial distance of the point (x, y) from the center of the lens (r ² = x ² + y ² ). In the design of such lenses, in an iterative process, a section through the lens surface along a diameter of the lens is calculated and then rotated 180 °.

Although lenses of this type offer some advantages, they have the problem that the focal point changes in the direction of the lens edges. As a result, the self-similarity of different parallel cuts through the lens surface is severely impaired in both elevation and azimuth.

Out DE 10 2009 024 433 A1 is known a lens whose lens surface is curved differently in elevation and in the azimuth. In other words, the slices through the lens surface in azimuth and elevation are different from each other, so that in particular the slices passing through the center of the lens in azimuth and elevation have _hzzi (x) = h (x, 0) and h _ele (y) = h (0, y).

In the design of such lenses, for example, one can proceed by first defining the two sections through the center of the lens in azimuth and elevation, and then superimposing these sections on an additive basis: h (x, y) = h _azi (x) + h _ele (y), where for reasons of consistency and without restriction of universality can be required: h _azi (0) = h (0, 0) and h _ele (0) = 0.

The object of the invention is to provide a dielectric lens with improved optical properties for radar sensors.

This object is achieved in that if a Y-cut of the lens surface for a given value x of the x-coordinate is given by the function h _x (y): = h (x, y), the lens surface has at least two Y-cuts which are independent of one another in the sense that one Y-cut can not be determined due to a symmetry of the lens surface by the other Y-cut nor can be converted into the other Y-cut by displacement along the z-axis.

In the design of such a lens, one can proceed by initially defining the corresponding Y-sections independently of one another for a plurality of values of the x-coordinate in order to optimize the refraction behavior of the lens in the YZ plane for the respective x-position. Furthermore, independent of the Y-cuts, one can define an X-cut h _{y = 0} (x) through the center of the lens and then modify the Y-cuts h _x (y) by adding constants such that the function applies to all points (x, 0) on the X-axis applies: h _x (0) = h _{y = 0} (x).

For example, in the automotive-mounted radar sensor, if the X-axis is the horizontal axis in the transverse direction of the vehicle and the Y-axis is the vertical axis, the focal length of the lens in azimuth (given by the X-section) differs from that of Select focal lengths in elevation, which are given by the different Y-sections. The focal lengths in elevation are in turn dependent on the respective lateral position (x-coordinate). This makes it possible, for example, to focus the incident radiation on a line instead of as before on a point.

Advantageous embodiments of the invention are specified in the subclaims.

In the following, embodiments of the invention will be explained in more detail with reference to the drawing.

Show it:

1 a perspective view of a lens according to the invention;

2 (A) and (B) Sketches for explaining the concept of a section for a spherical-plano-convex lens;

3 (A) and (B) a perspective view of a rotationally symmetric lens and a sketch for constructing sections through such a lens;

4 (A) and (B) is a perspective view of a prior art non-spherical lens and related sections; and

5 essential parts of a radar sensor with a lens according to the invention.

In 1 is in perspective a lens 10 for a radar sensor shown. This lens 10 has a massive lens body 12 of a dielectric plastic having a convexly curved lens surface 14 forms at which the passing through the lens radar waves are refracted and bundled.

The lens surface 14 is formed in the example shown symmetrically to two mutually perpendicular axes X and Y. When the radar sensor with the lens 10 is installed in a motor vehicle, for example, the axis X extends horizontally and the axis Y vertically, while a perpendicular to the axes X and Y axis Z extends in the direction of travel of the vehicle. The radar waves passing through the lens 10 go through are emitted and received substantially in the direction of the axis Z.

In the Cartesian coordinate system formed by the axes X, Y and Z, the lens surface 14 be described by a function z = h (x, y).

In 1 is still an X-section 16 (a section parallel to the X axis) shown by the center of the lens 10 passes. The X-cut 16 is thus a section line of the lens surface 14 with the XZ plane and can be described by a function h _{y = 0} (x) = h (x, 0). The index "y = 0" indicates that the cut is at the location y = 0.

Further shows 1 a Y-cut 20 which also passes through the middle of the lens 10 goes through, but runs in the direction of the Y-axis. This Y-cut thus corresponds to the cutting line which the lens surface 14 with the YZ plane and can be described as a function h _{x = 0} (y) = h (0, y).

1 shows a second Y-cut 22 at the point x = x ₀ , which is described by a function h _{x = x0} (y) = h ( _{x0 ,} y). Accordingly, further Y-cuts are possible for other values of the x-coordinate, as are further X-cuts for values of the y-coordinate other than 0.

The peculiarity of the lens described here 10 is that the Y-cuts for the different values of the x-coordinate, especially the Y-cuts 20 . 22 are independent of each other. The term "independent" is to be explained below on the basis of 2 to 4 be explained in more detail.

2 (A) shows a conventional spherical plano-convex lens 10 ' in a view in the direction of the Y-axis. This lens has a convex lens surface 14 ' , which is described by the function h (x, y) = (R ² -x ² -y ² ) ^1/2 , where R is the radius of curvature of the lens surface 14 ' is. The lens also has a second - flat - lens surface 14a , described by the function h (x, y) = H, where H is a constant.

In 2 (A) are also two cutting planes 24 . 26 shown running parallel to the YZ plane at different x positions.

2 B) shows a view of the same lens 10 ' in the direction of the X-axis. The in the cutting planes 24 . 26 formed Y-cuts are with 24a and 26a designated. With these Y-cuts 24a and 26a they are circle segments that have the same center of curvature (on the X axis) and differ in their radii. Another Y-cut that passes through the center of the lens (x = 0) drops in 2 B) with the contour of the lens surface 14 ' and therefore has the radius R. For any intersection at any coordinate position x, the radius r is given by r = (R ² -x ² ) ^1/2 . All Y-sections are thus by the radius of curvature R of the lens surface 14 ' and the coordinate x is uniquely determined and therefore not independent of each other. There is no free parameter that could be varied to change the shape of the cut.

The same applies to all rotationally symmetric lenses, even if they are not spherical. As an example shows 3 (A) a lens 10 '' with a non-spherical, but rotationally symmetric lens surface 14 '' , 3 (B) shows the same lens 10 '' in plan view, so in a view along the Z-axis. The X-cut passing through the center of the lens is described by a function h _{y = 0} (r), where r is here identical to the x-coordinate. Due to the rotational symmetry, the same function also describes the Y-cut h _{x = 0} (r) at the position x = 0. The Y-cut at any point x ₀ is also uniquely determined due to the rotational symmetry and is described by the Function h _{x = x0} (y) = h _{y = 0} ((x ₀ ² + y ² ) ^1/2 ), because the function value at the position (x ₀ , y) is the same as the function value of the X-section the location having the same distance r (= (x ₀ ² + y ² ) ^1/2 ) to the coordinate origin. The Y-sections at any point x are thus clearly determined and not independently selectable.

4 (A) and (B) show an example of a non-rotationally symmetric lens 10 ''' in which the X and Y cuts passing through the center of the lens 28 . 30 are independent of each other and in particular differently curved. For example, the X-section 28 is defined by any suitably chosen function h _{y = 0} (x) and the y-cut 30 is given by a function h _{x = 0} (y) satisfying the condition h _{x = 0} (0) = 0 and otherwise also free is selectable. The feature that the complete lens surface 14 ''' one then obtains by making the two cuts 28 . 30 additive superimposed: h (x, y) = h _{y = 0} (x) + h _{x = 0} (y). For a Y-cut at any point x ₀ then: h _x0 (y) = h _{y = 0} (x ₀ ) + h _{x = 0} (y). Therein, only the second term h _{x = 0} (y) depends on y. This term corresponds to the Y-section 30 through the middle of the lens and determines the shape of the cutting curve. The other term h _{y = 0} (x ₀ ) is constant and corresponds to a displacement of the curve along the z-axis.

By this rule are thus all Y-cuts such as the cuts 32 and 34 in 4 (A) clearly determined. 4 (B) shows a view of the same lens 10 ''' in the direction of arrows bb in 4 (A) , The cuts 32 and 34 are shown here by dashed lines. Unlike a spherical lens, these cuts do not lie on concentric circles, but they extend apart parallel to each other along the z-axis (vertically), so they have identical curvatures.

The in 2 to 4 The examples shown have in common that the Y-sections are not independent of each other. At most one of these Y-cuts can be chosen freely. All other Y-cuts are then uniquely determined by the symmetry of the lens and / or by a given X-cut.

In the lens according to the invention 10 according to 1 are the ones in Y-cuts 22 and 24 independent of each other in the sense that the shape of both Y-cuts can be chosen freely. In other words, if the Y-cut passing through the center of the lens 20 and the X-section through the center of the lens 16 is given, so it is the Y-cut 22 not yet clearly determined.

The lens surface 14 For example, you can construct as follows. First, the floor plan of the lens is set in the XY plane. This plan may have any shape, for example, circular, elliptical, rectangular or rod-shaped. Then, a set of cut planes is defined for several Y-cuts, and for each cut plane, the associated Y-cut is chosen freely and independently of all other Y-cuts, preferably such that the resulting position of the focus is in view of the optical requirements is optimized. The various Y-cuts are arranged by parallel displacements along the Z-axis so that their values for y = 0 are an X-cut 16 result, which determines the refractive behavior in azimuth. Finally, the points between the individual Y-sections are complemented by interpolation.

On the basis of the function h (x, y) thus obtained, an NC machine, which is an injection mold for the lens body, can then be controlled 12 processed accordingly.

Similar to in 4 can be the X and Y cuts going through the center of the lens 16 . 20 have different curvatures, so that the lens has different focal lengths in azimuth and elevation. Moreover, in the lens according to the invention, however, the individual Y-cuts also have freely and independently selectable curvatures, so that the refraction properties and in particular the focal lengths in elevation can be set individually for each x-position in order to optimize the optical properties of the lens.

As an application example shows the 5 schematically an angle-resolving radar sensor with a lens according to the invention 10 and four antenna patches spaced apart from the lens 36 which are used to transmit and receive radar waves in four separate channels. The antenna patches 36 are arranged on a line parallel to the X-axis (ie horizontally), so that the azimuth angle of the associated object can be calculated or at least estimated by comparing the amplitudes and phases of the radar signals received in the different channels. The different antenna patches 36 are hit by incoming radar waves in the azimuth at slightly different angles of incidence on the lens 10 to meet. Since the shape of the associated Y-section can be chosen freely for each x-position on the lens, the refractive properties of the lens can be adjusted so that the radar waves for all antenna patches 36 be optimally focused in elevation.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009024433 A1 [0005]

Claims (3)

Dielectric lens for radar sensors, with a lens body ( 12 ), the at least one radar wave breaking lens surface ( 14 ) defined by a function h (x, y) in a rectangular coordinate system with coordinate axes X, Y and Z, where h (x, y) for each point of the lens surface (FIG. 14 ) indicates the value of the z-coordinate as a function of the x and y coordinates, characterized in that when a Y-section of the lens surface ( 14 ) for a given value x of the x-coordinate is given by the function h _x (y): = h (x, y), the lens area ( 14 ) at least two Y-sections ( 20 . 22 ) that are independent of one another in the sense that the one Y-section ( 22 ) due to symmetry of the lens surface by the other Y-cut ( 20 ) determined by displacement along the z-axis in the other Y-section ( 20 ) is convertible. A lens according to claim 1, wherein an X-section passing through the center of the lens ( 16 ) and a through the center of the lens going Y-section ( 20 ) have different curvatures. Lens according to claim 1 or 2, wherein the lens body ( 12 ) has an elliptical ground plan in the XY plane.

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