METHOD FOR ADVANCED AND LOW COST CROSS TRAFFIC ALERT, RELATED PROCESSING SYSTEM, CROSS TRAFFIC ALERT SYSTEM AND VEHICLE

• US 20180082132A1
• Filed: 03/28/2017
• Published: 03/22/2018
• Est. Priority Date: 09/21/2016
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Spampinato, Giuseppe, Curti, Salvatore, Guarneri, Nunziata Ivana, Bruna, Arcangelo Ranieri
• Granted Patent: US 10,242,272 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 18/23 Clustering techniques
• CPC Class Codes: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle
• CPC Class Codes: G06V 20/58 Recognition of moving objects or obstacles, e.g. vehicles or pedestrians; Recognition of traffic objects, e.g. traffic signs, traffic lights or roads
• CPC Class Codes: G06V 40/20 Movements or behaviour, e.g. gesture recognition recognition of facial expressions G06V40/16
• CPC Class Codes: G08G 1/09626 where the origin of the information is within the own vehicle, e.g. a local storage device, digital map

Abstract

A sequence of images obtained by a camera mounted on a vehicle is processed in order to generate Optical Flow data including a list of Motion Vectors being associated with respective features in the sequence of images. The Optical Flow data is analyzed to calculate a Vanishing Point by calculating the mean point of all intersections of straight lines passing through motion vectors lying in a road. An Horizontal Filter subset is determined taking into account the Vanishing Point and a Bound Box list from a previous frame in order to filter from the Optical Flow the horizontal motion vectors. The subset of Optical Flow is clustered to generate the Bound Box list retrieving the moving objects in a scene. The Bound Box list is sent to an Alert Generation device and an output video shows the input scene where the detected moving objects are surrounded by a Bounding Box.

Claims

1. A method for Cross Traffic Alert, comprising the steps of:

receiving a sequence of images from a camera mounted on a vehicle;

processing said sequence of images in order to generate Optical Flow data comprising a list of Motion Vectors being associated with respective features in said sequence of images;

analyzing said Optical Flow data in order to calculate a Vanishing Point as a mean point of all intersections of straight lines passing through Motion Vectors lying in a road;

calculating an Horizontal Filter subset taking into account the Vanishing Point and a Bound Box list from a previous frame and filtering from the Optical Flow horizontal Motion Vectors;

clustering with a subset of the Optical Flow to generate the Bound Box list by retrieving moving objects in a scene, wherein said Bound Box list is sent to an Alert Generation device; and

generating an output video showing the input scene where the moving objects are surrounded by a Bounding Box.

2. The method for Cross Traffic Alert according to claim 1, comprising the steps of:

filtering the Optical Flow according to orientation and selecting only the Motion Vectors laying in the road in order to form a reduced set;

calculating the Vanishing Point for each frame as an average position of all intersections among lines generated by directions of Motion Vectors belonging to the reduced set;

checking the Vanishing Point and estimating the Vanishing Point VP position in the current frame;

overlying a grid over the image to determine if the Vanishing Point position of the current frame belongs to a central area of the grid; and

calculating an arithmetic media between the valid Vanishing Point VP positions relative to subsequent frames.

3. The method for Cross Traffic Alert according to claim 1, wherein calculating the Horizontal Filter subset comprises the steps of:

checking the Bounding Box and maintaining in said subset the Motion Vectors inside the previous calculated Bound Box List;

performing a Horizontal Check wherein the Motion Vectors outside the previous calculated Bound Box List are checked and the horizontal Motion Vectors MVs are filtered and if the Motion Vector is considered Horizontal it is maintained in the subset, and otherwise it is discarded.

4. The method for Cross Traffic Alert according to claim 3, wherein a Motion Vector is considered horizontal, if the two conditions are both satisfied:

the orientation of the Motion Vector lies around an horizontal orientation; and

the orientation difference between the Motion Vector orientation and the orientation of the Motion Vector translated on the Vanishing Point overcomes an evaluated dynamic threshold.

5. The method for Cross Traffic Alert according to claim 4, wherein said dynamic threshold can be valued as percentage of the difference between maximum and minimum orientation lying around the considered Motion Vector and in particular, for each Motion Vectors the neighborhood considered is set to ±

1 in both directions.

6. A processing system, configured to perform the following operations:

receive a sequence of images from a camera mounted on a vehicle;

process said sequence of images in order to generate Optical Flow data comprising a list of Motion Vectors being associated with respective features in said sequence of images;

analyze said Optical Flow data in order to calculate a Vanishing Point as a mean point of all intersections of straight lines passing through Motion Vectors lying in a road;

calculate an Horizontal Filter subset taking into account the Vanishing Point and a Bound Box list from a previous frame and filtering from the Optical Flow horizontal Motion Vectors;

cluster with a subset of the Optical Flow to generate the Bound Box list by retrieving moving objects in a scene, wherein said Bound Box list is sent to an Alert Generation device; and

generate an output video showing the input scene where the moving objects are surrounded by a Bounding Boxmethod of a Cross Traffic Alert system.

7. A Cross Traffic Alert system, comprising:

a camera mounted to a vehicle and configured to a sequence of images; and

an Alert Generation processing system configured to;

receive a sequence of images from a camera mounted on a vehicle;

process said sequence of images in order to generate Optical Flow data comprising a list of Motion Vectors being associated with respective features in said sequence of images;

analyze said Optical Flow data in order to calculate a Vanishing Point as a mean point of all intersections of straight lines passing through Motion Vectors lying in a road;

calculate an Horizontal Filter subset taking into account the Vanishing Point and a Bound Box list from a previous frame and filtering from the Optical Flow horizontal Motion Vectors;

cluster with a subset of the Optical Flow to generate the Bound Box list by retrieving moving objects in a scene, wherein said Bound Box list is sent to an Alert Generation device; and

generate an output video showing the input scene where the moving objects are surrounded by a Bounding Boxmethod of a Cross Traffic Alert system.

8. The Cross Traffic Alert system of claim 7, wherein the system is a component of a vehicle.