Glaring reduction for dynamic rearview mirror

• US 9,307,207 B2
• Filed: 09/30/2013
• Issued: 04/05/2016
• Est. Priority Date: 01/07/2013
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Zhang, Wende, Wang, Jinsong, Lybecker, Kent S., Piasecki, Jeffrey S., Frakes, Ryan M., Hester, Travis S.
• Primary Examiner(s): Chen, Chia-Wei A
• Application Number:
  US14/040,952
• Publication Number:
  US 20140192227A1
• Time in Patent Office: 918 Days
• Field of Search: 348/218.1, 348/230.1, 348/222.1, 382274-284
• US Class Current: 1/1
• CPC Class Codes: H04N 23/741 by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors

Abstract

A method for generating a glare-reduced image from images captured by a camera device of a subject vehicle includes obtaining a short-exposure image and a long-exposure image and generating a resulting high dynamic range image based on the short-exposure and long-exposure images. Pixel values are monitored within both the short- and long-exposure images. A light source region is identified within both the short- and long-exposure images based on the monitored pixel values. A glaring region is identified based on the identified light source region and one of calculated pixel ratios and calculated pixel differences between the monitored pixel values of the long- and short-exposure images. The identified glaring region upon the resulting high dynamic range image is modified with the identified light source region within the short-exposure image. The glare-reduced image is generated based on the modified identified glaring region upon the resulting HDR image.

Claims

1. Method for generating a glare-reduced image from images captured by a camera device of a subject vehicle, comprising:

obtaining a short-exposure image and a long-exposure image captured by the camera device;

generating a resulting high dynamic range (HDR) image based on the short-exposure and long-exposure images;

monitoring pixel values within both the short-exposure and the long-exposure images;

identifying a light source region within both the short-exposure and the long-exposure images based on the monitored pixel values;

calculating one of pixel ratios and pixel differences between the monitored pixel values of the long-exposure and the short-exposure images;

identifying a glaring region based on the identified light source region within both the short-exposure and the long-exposure images and one of calculated pixel ratios and calculated pixel differences;

modifying the identified glaring region upon the resulting HDR image with a short-exposure region corresponding to the identified light source region within the unmodified short-exposure image, comprising increasing the portion of the unmodified identified light source region within the short-exposure image and decreasing the portion of the identified light source region within the long-exposure image applied thereto; and

generating a glare-reduced image based on the modified identified glaring region upon the resulting HDR image.

2. The method of claim 1, wherein the short-exposure and the long-exposure images are simultaneously obtained when the camera device utilizes a split sub-pixel imaging chip incorporating a short-exposure sub-pixel and a long-exposure sub-pixel for each pixel.

3. The method of claim 1, wherein the short-exposure and the long-exposure images are obtained during different time periods when the camera device utilizes an imaging chip having an array of pixels each adjustable between one of a short-exposure time and a long-exposure time at a time.

4. The method of claim 3, wherein obtaining the short-exposure and long-exposure images comprises:

for each pixel, utilizing the short-exposure time during a first time period to obtain the short-exposure image and utilizing the long-exposure time during a second time period to obtain the long-exposure image.

5. The method of claim 1, wherein identifying the light source region within both the short-exposure and the long-exposure images comprises:

comparing the monitored pixel values to a light source threshold; and

identifying the light source region within both the short-exposure and the long-exposure images corresponding to a region wherein the monitored pixel values exceed the light source threshold.

6. The method of claim 1, wherein the monitored pixel values comprise at least an intensity value for each pixel within both the short-exposure and the long-exposure images.

7. The method of claim 6, wherein the monitored pixel values further comprise color information for each pixel within both the short-exposure and the long-exposure images.

8. The method of claim 1, wherein identifying the glaring region comprises:

comparing calculated pixel ratios to a glaring threshold;

identifying the glaring region corresponding to a region around a perimeter of the identified light source where calculated pixel ratios exceed the glaring threshold.

9. The method of claim 1, wherein identifying the glaring region comprises:

comparing calculated pixel differences to a glaring threshold;

identifying the glaring region corresponding to a region around a perimeter of the identified light source where calculated pixel differences exceed the glaring threshold.

10. The method of claim 1, wherein generating the glare-reduced image further comprises:

in all other regions not identified as the glaring region, applying HDR processing for enhancing image quality for the resulting HDR image.

11. The method of claim 10, wherein applying HDR processing includes at least one of applied tone mapping, adjusted exposure time, gamma correction and pixel bit-depth conversion.

12. The method of claim 1, wherein modifying the identified glaring region upon the resulting HDR image comprises:

modifying the identified glaring region to include a portion of the identified light source region within the short-exposure image that is greater than a portion of the identified light source region within the long-exposure region.

13. The method of claim 12. wherein the portion of the identified light source region within the short-exposure image gradually decreases from a center of the identified glaring region to a periphery of the identified glaring region.

14. Method for generating a glare-reduced image from images captured by a camera device of a subject vehicle, comprising:

obtaining a short-exposure image and a long-exposure image captured by the camera device;

generating a resulting high dynamic range (HDR) image based on the obtained short-exposure and long-exposure images;

monitoring pixel values within both the short-exposure and the long-exposure images, each pixel value comprising at least an intensity value;

identifying a light source region within both the short-exposure and the long-exposure images based on the monitored pixel values;

identifying a glaring region around a perimeter of the identified light source based on the identified light source region within both the short-exposure and the long-exposure images and the calculated pixel ratios between the monitored pixel values of the long-exposure and the short-exposure images;

modifying the identified glaring region upon the resulting HDR image with a short-exposure region corresponding to the respective identified light source region within the unmodified short-exposure image, comprising increasing the portion of the unmodified identified light source region within the short-exposure image and decreasing the portion of the identified light source region within the long-exposure image applied thereto;

applying HDR processing for obtaining optimal image quality for the resulting HDR image in all other regions not identified as the glaring region; and

generating a glare-reduced image based on the modified identified glaring region upon the resulting HDR image.

15. The method of claim 14, wherein the identified light source region includes one of a direct light source region and a reflective light source region.

16. The method of claim 14, wherein obtaining the short-exposure and the long-exposure images comprises one of:

spatially obtaining the short-exposure and the long-exposure images simultaneously when the camera device utilizes a split sub-pixel imaging chip incorporating a short-exposure sub-pixel and a long-exposure sub-pixel for each pixel; and

temporally obtaining the short-exposure and the long-exposure images during different time periods when the camera device utilizes an imaging chip having an array of pixels each adjustable between one of a short-exposure time and a long-exposure time at a time.

17. The method of claim 14, wherein identifying the light source region within both the short-exposure and the long-exposure images based on the monitored pixel values comprises:

comparing the monitored pixel values to a light source threshold, the light source threshold comprising a minimum intensity indicative of a light source;

identifying the light source region within both the short-exposure and the long-exposure images corresponding to a region wherein the monitored pixel values exceed the light source threshold.

18. The method of claim 14, wherein identifying the glaring region around the perimeter of the identified light source comprises:

comparing calculated pixel ratios to a glaring threshold, the glaring threshold comprising a minimum intensity value indicative of a glaring effect; and

identifying the glaring region corresponding to the region around the perimeter of the identified light source where calculated pixel ratios exceed the glaring threshold.

19. The method of claim 14, wherein the camera device comprises a rear-view camera device for capturing a field of view rearward of the subject vehicle.

20. An apparatus for generating a glare-reduced image from images captured by a camera device of a subject vehicle, comprising:

the camera device capturing a field of view projecting away from the subject vehicle; and

a processing device configured to;

obtain a short-exposure image and a long-exposure image captured by the camera device,

generate a resulting high dynamic range (HDR) image based on the obtained short-exposure and long-exposure images,

monitor pixel values within both the short-exposure and the long-exposure images, identify a light source region within both the short-exposure and the long-exposure images based on the monitored pixel values,

calculate pixel ratios between the monitored pixel values of the long-exposure and the short-exposure images,

identify a glaring region based on the identified light source region within both the short-exposure and the long-exposure images and the calculated pixel ratios,

modify the identified glaring region upon the resulting HDR image with a short-exposure region corresponding to the identified light source region within the unmodified short-exposure image, comprising increasing the portion of the unmodified identified light source region within the short-exposure image and decreasing the portion of the identified light source region within the long-exposure image applied thereto, and

generate a glare-reduced image based on the modified identified glaring region upon the resulting HDR image.