VEHICULAR CAMERA AND METHOD FOR PERIODIC CALIBRATION OF VEHICULAR CAMERA

• US 20120320209A1
• Filed: 01/13/2011
• Published: 12/20/2012
• Est. Priority Date: 01/13/2010
• Status: Active Grant

• Current Assignee: Magna Electronics Incorporated (Magna International Incorporated)
• Original Assignee: Magna Electronics Incorporated (Magna International Incorporated)
• Inventors: Zibman, Sharon, Vico, Marko, Stefanovic, Aleksandar
• Granted Patent: US 9,150,155 B2
• Time in Patent Office: Days
• US Class Current: 348/148
• CPC Class Codes: B60R 1/00 Optical viewing arrangements; Real-time viewing arrangements for drivers or passengers using optical image capturing systems, e.g. cameras or video systems specially adapted for use in or on vehicles
• CPC Class Codes: B60R 11/04 Mounting of cameras operative during drive; Arrangement of controls thereof relative to the vehicle
• CPC Class Codes: B60R 2300/304 using merged images, e.g. merging camera image with stored images
• CPC Class Codes: B60R 2300/402 Image calibration
• CPC Class Codes: B60R 2300/806 for aiding parking
• CPC Class Codes: G06T 11/60 Editing figures and text; Combining figures or text
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/30252 Vehicle exterior; Vicinity of vehicle
• CPC Class Codes: G06T 2207/30264 Parking
• CPC Class Codes: G06T 7/80 Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration

Abstract

In a first aspect, the invention is directed to a vehicular camera and a method for calibrating the camera after it has been installed in a vehicle. In particular, the invention is directed to calibrating a vehicular camera after the camera has been installed in a vehicle, wherein the camera is of a type that applies an overlay to an image and outputs the image with the overlay to an in-vehicle display.

Claims

1. A camera for a vehicle, said camera comprising:

a lens positioned to capture a view behind a vehicle, wherein the view includes a portion of the bumper of the vehicle;

an imager including an image sensor and an imager microcontroller, wherein the image sensor is positioned to receive images from the lens; and

a camera microcontroller configured to control the application of an overlay to the images, wherein the camera microcontroller is operable to receive data from the imager microcontroller relating to bars of pixels on the image sensor, wherein the microcontroller is further operable to detect a reference point in the images using the data and is operable to determine an offset amount with which to shift the overlay on the images.

2. :

A camera as claimed in claim 1, wherein the imager microcontroller is operable to transmit the images to an in-vehicle display via an analog signal.

3. :

A camera as claimed in claim 1, wherein the camera microcontroller is operable to detect the reference point iteratively using data from the imager microcontroller relating to successively smaller bars of pixels on the image sensor.

4. :

A camera as claimed in claim 1, wherein the camera microcontroller is operable to detect the vertical pixel position of the reference point using data from vertically stacked bars of pixels on the image sensor.

5. :

A camera as claimed in claim 4, wherein the camera microcontroller is operable to detect the horizontal pixel position of the reference point using data from horizontally stacked bars of pixels on the image sensor.

6. :

A camera as claimed in claim 1, wherein the reference point corresponds to a point on the edge of the bumper of the vehicle.

7. :

A camera as claimed in claim 6, wherein the edge of the bumper of the vehicle appears as a curved line in the images received by the imager and wherein the reference point is an extremum on the curved line.

8. :

A camera as claimed in claim 1, wherein, prior to detecting the reference point, the camera microcontroller determines whether there is sufficient contrast in the images.

9. :

A camera as claimed in claim 8, wherein the camera microcontroller selects bars of pixels in the images and compares brightness values of the pixels and variances in brightness between adjacent pixels within each bar to determine if there is sufficient contrast in the images.

10. :

A camera as claimed in claim 1, wherein the camera microcontroller is operable to determine the rotation angle of the camera and to adjust the offset amount based on the rotation angle.

11. :

A camera as claimed in claim 10, wherein the camera microcontroller is operable to determine the rotation angle of the camera and to adjust the position of the overlay rotationally based on the detected rotation angle.

12. :

A camera as claimed in claim 1, further comprising a near-infrared light emitting diode operable to emit near-infrared light on the portion of the bumper of the vehicle.

13. :

A method of calibrating a vehicular camera installed in a vehicle, wherein the camera has an imager and a camera microcontroller, said method comprising;

(a) determining whether the contrast in images received by the imager is beyond a selected threshold value;

(b) searching for a reference point in the images depending on the result of step (a) using the camera microcontroller; and

(c) adjusting the position of an overlay applied by the microcontroller to the images depending on the result of step (b).

14. :

A method as claimed in claim 13, wherein step (b) includes;

(d) selecting a search window within the images;

(e) dividing the search window into a plurality of bars, wherein each bar corresponds to a plurality of pixels on the imager;

(f) receiving data relating to brightness levels of the bars; and

(g) detecting the position of the reference point based on changes in brightness levels from bar to bar.

15. :

A method as claimed in claim 14, wherein the search window selected in step (d) is a vertical position search window and wherein step (b) further includes;

(h) selecting a rotation angle detection search window;

searching for the positions of a plurality of rotation angle reference points; and

(i) determining whether to adjust the position of the overlay rotationally based on the results of step (i).

16. :

A camera for a vehicle, said camera comprising;

a lens positioned to capture a view behind a vehicle, wherein the view includes a portion of the bumper of the vehicle;

an imager including an image sensor and an imager microcontroller, wherein the image sensor is positioned to receive images from the lens;

a camera microcontroller configured to control the application of an overlay to the images, wherein the camera microcontroller is operable to receive data from the imager microcontroller relating to bars of pixels on the image sensor, wherein the microcontroller is further operable to detect a reference point in the images using the data and is operable to determine an offset amount with which to shift the overlay on the images;

wherein the imager microcontroller is operable to transmit the images to an in-vehicle display via an analog signal; and

wherein the camera microcontroller is operable to detect the reference point iteratively using data from the imager microcontroller relating to successively smaller bars of pixels on the image sensor.

17. :

A camera as claimed in claim 16, wherein the camera microcontroller is operable to detect the vertical pixel position of the reference point using data from vertically stacked bars of pixels on the image sensor, and wherein the camera microcontroller is operable to detect the horizontal pixel position of the reference point using data from horizontally stacked bars of pixels on the image sensor.

18. :

A camera as claimed in claim 16, wherein a near-infrared light emitting diode is operable to emit near-infrared light on the portion of the bumper of the vehicle.

19. :

A camera as claimed in claim 16, wherein, prior to detecting the reference point, the camera microcontroller determines whether there is sufficient contrast in the images, and wherein the camera microcontroller selects bars of pixels in the images and compares brightness values of the pixels and variances in brightness between adjacent pixels within each bar to determine if there is sufficient contrast in the images.

20. :

A camera as claimed in claim 16, wherein the camera microcontroller is operable to determine the rotation angle of the camera and to adjust the offset amount based on the rotation angle, and wherein the camera microcontroller is operable to determine the rotation angle of the camera and to adjust the position of the overlay rotationally based on the detected rotation angle.