Method for Measuring a Distance Between an Object and an Optical Sensor, Control Device for Carrying Out Such a Method, Distance Measuring Apparatus Comprising Such a Control Device, and Motor Vehicle Comprising Such a Distance Measuring Apparatus

Abstract

A method for measuring a distance between an object and an optical sensor by an illumination device and the optical sensor. A spatial position of a visible distance region in an observation region of the optical sensor is specified. A captured image of the visible distance region is captured by the optical sensor. A start image line and an end image line of the visible distance region are determined in the captured image. A base point image line is ascertained in the captured image as an image line with a shortest distance to the start image line in which the object can be detected. A distance from the object is ascertained by evaluating an image position of the base point image line relative to the start image line and the end image line while taking account of the spatial position of the visible distance region.

Claims

1.-8. (canceled)

9. A method for measuring a distance between an object (17) and an optical sensor (7) by an illumination device (5) and the optical sensor (7), comprising the steps of: controlling the illumination device (5) and the optical sensor (7) in a manner temporally coordinated with one another; wherein a spatial position of a visible distance region (15) in an observation region (13) of the optical sensor (7) is specified by the temporally coordinated control of the illumination device (5) and of the optical sensor (7), wherein a captured image (23) of the visible distance region (15) is captured by the optical sensor (7) by the temporally coordinated control; wherein a start image line for a beginning (19) and an end image line for an end (21) of the visible distance region (15) are determined in the captured image (23); wherein a base point image line is ascertained in the captured image (23) as an image line with a shortest distance to the start image line in which the object (17) can be detected; wherein a distance from the object (17) is ascertained by evaluating an image position of the base point image line relative to the start image line and the end image line while taking account of the spatial position of the visible distance region (15).

10. The method according to claim 9, wherein for the captured image (23) of the visible distance region (15), a line histogram (25) is created over all image lines associated with an evaluation region (27) in the observation region (13) on the optical sensor (7) by summing illumination intensities per image line of the optical sensor (7), and wherein the start image line and the end image line are determined by the line histogram (25).

11. The method according to claim 9, wherein an object distance is determined as a distance between the object (17) and the optical sensor (7), wherein a distance region width is determined as a difference from the end (21) of the visible distance region (15) and the beginning (19) of the visible distance region (15), wherein a base point distance is determined as an image line distance on the optical sensor (7) between the base point image line and the start image line, wherein a distance region image width is ascertained as an image line distance between the end image line and the start image line, wherein the object distance is ascertained as a sum of the beginning (19) of the visible distance region (15) and a product of the distance region width with a ratio of the base point distance to the distance region image width.

12. The method according to claim 9, wherein the illumination device (5) and the optical sensor (7) are configured for operation in a near infrared range.

13. The method according to claim 9, wherein a temporal sequence of captured images (23) is created, wherein a temporal coordination of the illumination device (5) and of the optical sensor (7) is altered such that a change in the distance of the object (17) over time is determined.

14. A control device (9) configured to carry out the method according to claim 9.

15. A distance measuring apparatus (3), comprising: an illumination device; an optical sensor (7); and a control device (9) configured to carry out the method according to claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows a schematic illustration of one exemplary embodiment of a motor vehicle with one exemplary embodiment of a distance measuring apparatus;

[0037] FIG. 2 shows a schematic illustration of a captured image, captured in the context of one embodiment of the method using an optical sensor; and

[0038] FIG. 3 shows a schematic illustration of a line histogram which is used in one embodiment of the method.

DETAILED DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 shows a schematic illustration of one exemplary embodiment of a motor vehicle 1, with one exemplary embodiment of a distance measuring apparatus 3. The distance measuring apparatus 3 has an illumination device 5 and an optical sensor 7. Moreover, the distance measuring apparatus 3 has a control device 9 which is only shown schematically here and, in a manner not shown explicitly, is operatively connected to the illumination device 5 and the optical sensor 7 for the respective control thereof. An illumination frustum 11 of the illumination device 5 and an observation region 13 of the optical sensor 7 are shown in particular in FIG. 1. A visible distance region 15 which results as a subset of the observation region 13 of the optical sensor 7 is also shown in hatched lines.

[0040] A object 17 is arranged in the visible distance region 15.

[0041] A beginning 19 and an end 21 of the visible distance region 15 are also drawn in FIG. 1.

[0042] The control device 9 is configured in particular to carry out an embodiment that is described in more detail below of a method for measuring a distance x between the object 17 and the optical sensor 7.

[0043] The illumination device 5 and the optical sensor 7 are controlled in a manner temporally coordinated with one another, wherein a spatial position of the visible distance region 15 in the observation region 13 is specified by the temporally coordinated control of the illumination device 5 and of the optical sensor 7. A captured image of the visible distance region 15 is captured by the optical sensor 7 using the coordinated control.

[0044] FIG. 2 shows a schematic illustration of such a captured image 23 in an image plane of the optical sensor 7. A start image line v.sub.near for the beginning 19 and an end image line v.sub.far for the end 21 of the visible distance region 15 in the captured image 23 is illustrated in FIG. 2. The position of this start image line v.sub.near and of the end image line v.sub.far is determined. A base point image line v is also determined in the captured image 23 as that image line having the shortest distance to the start image line v.sub.near in which the object 17 can be detected. The distance of the object 17 is then ascertained by evaluating the image position of the base point image line v, i.e., the position thereof in the captured image 23, relative to the start image line v.sub.near and the end image line v.sub.far while taking the object-side spatial position of the visible distance region 15 into account.

[0045] The image of the object 17 in the captured image 23 is denoted with 17′ in FIG. 2.

[0046] In addition, an evaluation region 27 which can be determined in particular by a GPS prediction and/or by a method for optical lane tracking is drawn in FIG. 2. As the region of interest, the evaluation region 27 is smaller here than the observation region 13. However, it can also coincide with the latter.

[0047] An object distance x—cf. FIG. 1—is determined as distance between the object 17 and the optical sensor 7 in particular, by determining a distance region width (x.sub.far−x.sub.near) as difference from the end 21 of the visible distance region 15 and the beginning 19 of the visible distance region 15. A base point distance (v−v.sub.near) is determined as image line distance on the optical sensor 7 between the base point image line v and the start image line v.sub.near. A distance region image width (v.sub.far−v.sub.near) is ascertained as image line distance between the end image line v.sub.far and the start image line v.sub.near. The object distance x is then ascertained as sum of the beginning 19 of the visible distance region 15 and the product of the distance region width (x.sub.far−x.sub.near) with the ratio of the base point distance (v—v.sub.near) to the distance region image width (v.sub.far−v.sub.near) In particular, the object distance x is ascertained according to Equation (1) given above.

[0048] FIG. 3 shows a schematic illustration of a line histogram 25 of the captured image 23 according to FIG. 2 or of the evaluation region 27 of the captured image 23. The individual image lines of the optical sensor 7 are plotted on the x axis in this line histogram 25, with a sum of the illumination intensities per pixel over all pixels of the respective image line in the evaluation region 27 being plotted on the y axis for each image line. This line histogram 25 is created over all image lines assigned to the evaluation region 27 on the optical sensor 7 by summing the illumination intensities per image line of the optical sensor 7. The start image line v.sub.near and the end image line v.sub.far are then ascertained by means of the line histogram 25, wherein in particular owing to the temporally coordinated control of the illumination device 5 and of the optical sensor 7, significant jumps in intensity in the start image line v.sub.near and in the end image line v.sub.far can be seen.

[0049] The illumination device 5 and the optical sensor 7 are preferably designed for operation in the near infrared range, in particular at 1.55 μm.

[0050] In the context of the method, a temporal sequence of captured images 23 is preferably created, wherein the temporal coordination of the illumination device 5 and of the optical sensor 7 is altered so that a change in the distance of the object 17 over time can be determined.