Apparatus for identification and tracking of objects

• US 5,762,292 A
• Filed: 09/11/1989
• Issued: 06/09/1998
• Est. Priority Date: 09/08/1988
• Status: Expired due to Fees

• Current Assignee: Lfk-Lenkflugkã¶Rpersysteme GmbH (MBDA)
• Original Assignee: Daimler-Benz Aerospace AG (Mercedes-Benz Group AG)
• Inventors: Schweyer, Nikolaus, Pfefferle, Rudolf, Holick, Fred
• Primary Examiner(s): Jordan, Charles T.
• Application Number:
  US07/411,158
• Time in Patent Office: 3,193 Days
• Field of Search: 244/3.17
• US Class Current: 244/3.17
• CPC Class Codes: F41G 7/343 comparing observed and stored data of target position or of distinctive marks along the path towards the target
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/10032 Satellite or aerial image; Remote sensing
• CPC Class Codes: G06T 2207/30212 Military
• CPC Class Codes: G06T 2207/30256 Lane; Road marking
• CPC Class Codes: G06T 7/12 Edge-based segmentation
• CPC Class Codes: G06T 7/70 Determining position or orientation of objects or cameras camera calibration G06T7/80
• CPC Class Codes: G06V 10/48 by mapping characteristic values of the pattern into a parameter space, e.g. Hough transformation

Abstract

Target acquisition device with an imaging sensor, a signal processing circuit and an evaluating circuit comprising a computer for implementing a gray-value analysis of the output signals of the imaging sensor, wherein the signal processing circuit contains threshold value transmitters for the brightness transitions and for the local extreme values, a selection of three values, bright/reference/dark, is effected in the signal evaluation circuit and a centroid of the target is determined from the latter, particularly by means of producing coordinates of the target, and, in order to acquire the target according to the position finding by means of comparison of the measured parameters with the stored parameters in the evaluating circuit, the computer also evaluates the mathematical signs of the received gradient image for determining the target direction, and in that, in addition to a binary image, edges and non-edges, edge points lying on a straight line can also be obtained, particularly from one or more image sections.

Claims

1. Device for the acquisition and tracking of objects by means of characteristic features by which these objects are identifiable from a distance in the air in front of a background by means of an imaging sensor and a processing circuit for the signals obtained from the latter for comparison with reference signals stored beforehand, characterized by the combination of the following features:

a) output signals of an imaging sensor (1), which is stabilized with respect to attitude, are analyzed with respect to brightness gradients contained therein for extracting edge lines (2) of the object;

b) edge points are selected in a point selector (3) from the local extreme values of the brightness gradients by means of adaptive threshold value formation in the signal processing circuit;

c) edge points lying on a straight line are represented by local extreme values by means of a parameter transformer (4), which local extreme values characterize a straight line portion by means of their parameters;

d) the measured parameters are compared with the stored reference parameters (11) in an evaluating computer (5) while taking into account measured path data, and the results of the comparison are made available at its output for further processing;

e) the output signal of the sensor (1) is analyzed within a plurality of image sections for average brightness and variance;

f) a gray value histogram of edge points is calculated within a plurality of image sections;

g) two threshold values which divide up the brightness values into three words, bright/reference/dark, and thus convert the image into a three-stage image are calculated from the data from e) and f) for each of the image sections;

h) all image portions designated as "bright" or "dark" are roughly analyzed with respect to their magnitude, shape and position in order to determine whether or not they could be the sought target or whether or not possible target objects coincide with other objects and, if this is the case, the target objects are separated; and

i) all possible target objects are accurately analyzed by means of shape, position and orientation features in order to determine whether or not they are sought targets.

2. Target acquisition device according to claim 1, characterized in that the target search can be switched in at least two stages from rough to precise in that the parameter gradation is reduced when determining the local extreme values.

3. Target acquisition device according to claim 1 or 2, characterized in that the accuracy of the target search is increased by repeating the individual search steps with a plurality of different image sections.

4. Target acquisition device according to claim 1, characterized in that after the comparison of the measured parameters with the stored parameters in the evaluating circuit by means of the computer, a plausibility test of the results is effected, with respect to magnitude, distance, position and frequency of the object, and in that interference objects are accordingly eliminated.

5. Target acquisition device according to claim 1, characterized in that only edge directions located at an expected direction within a predetermined tolerance range are taken into account in the processing in one of extracting edge lines (2) and point selector (3).

6. Target acquisition device according to claim 1, characterized by the imaging sensor (1), a signal processing circuit and an evaluating circuit comprising a computer for implementing a gray-value analysis of the output signals of the imaging sensor, wherein the signal processing circuit contains threshold value transmitters for the brightness in such a way that a sorting is effected in the signal evaluating circuit for the three values, bright/reference/ dark, a surface centroid or center of mass and contour features of the target are determined from this, by producing coordinates of the target and of its contour points, and, for the purpose of target acquisition according to the position finding the computer determines, by means of scanning the features, whether or not a sought target is concerned according to a decision tree and regulating of the hierarchical scanning, and also evaluates the mathematical sign of the obtained gradient image, for determining the target direction, and in that edge points lying on a straight line are also obtained in the computer in addition to a binary image--edges and non-edges--from one or more image sections.

7. Navigation device comprising means according to one of claim 1 or 6 for the acquisition of road structures, characterized in that the computer further processes the results obtained from the comparison of the measured parameters with the stored parameters in the evaluating circuit (2-5, 11) while taking into account the measured path data--as known per se--to form data for guidance of a missile for target tracking.

8. Navigation device according to claim 7, characterized in that use is made for acquisition and tracking objects moving on the ground along known lines.

9. Navigation device according to claim 7, characterized in that it serves for the acquisition and tracking stationary objects on the ground, in the form of one of bridges, antennae, hangars, polygons, prisms, spheres, comprising at least partially typical basic-shape elements.