Method and device for improving camera images for driver assistance systems
A method removes brightening, which is caused by scattered light, from an image of an external environment of a vehicle captured by a vehicle camera arranged in or on the vehicle. A curve of a total intensity e.g. along a respective line within the image is determined, wherein the total intensity is caused by desired light and scattered light that reach the coverage area of the vehicle camera. An approximation function of a lower limit of the scattered light intensity is estimated. The estimated approximation function is subtracted from the determined curve of the total intensity to produce a modified image with reduced or corrected scattered light.
1. A method of computationally removing brightening caused by scattered light from an image of a vehicle camera, the method comprising the method steps:
capturing a captured image of an external environment of a vehicle by a vehicle camera arranged in or on the vehicle, and
by a processor unit:
determining a curve of a total intensity within the captured image, wherein the total intensity includes a desired light intensity of desired light and a scattered light intensity of scattered light which reach an image capture coverage area of the vehicle camera and are included in the captured image,
estimating an approximation function of a lower limit of the scattered light intensity,
subtracting the estimated approximation function of the lower limit of the scattered light intensity from the determined curve of the total intensity to produce a corrected intensity curve,
producing a modified image with corrected scattered light based on the corrected intensity curve, and
providing the modified image with corrected scattered light.
2. The method according to claim 1 , wherein the approximation function of the lower limit of the scattered light intensity comprises a Gaussian distribution.
3. The method according to claim 1 , comprising performing the determining of the curve of the total intensity respectively line by line or block by block over an entire image area of the captured image.
4. The method according to claim 1 , wherein the estimating of the approximation function of the lower limit of the scattered light intensity comprises performing interpolation area by area over the captured image.
5. The method according to claim 1 , wherein the estimating of the approximation function of the lower limit of the scattered light intensity comprises checking whether a maximum of the determined curve of the total intensity and a maximum of the corrected intensity curve occur at a same position along a vertical curve of the captured image.
6. The method according to claim 1 , further comprising checking whether the scattered light has the same color throughout the captured image.
7. The method according to claim 1 , wherein the captured image is a first captured image,
further comprising capturing a second captured image of the external environment by the vehicle camera after the first captured image, and tracking the estimated approximation function of the lower limit of the scattered light intensity from the first captured image in the second captured image.
8. The method according to claim 7 , further comprising estimating a position of a sun which causes the scattered light in the second captured image, while filtering to account for a motion of the vehicle camera.
9. The method according to claim 1 , further comprising taking into account a vignetting of the scattered light.
10. The method according to claim 1 , wherein the estimating of the approximation function of the lower limit of the scattered light intensity eliminates strong fluctuations in the corrected intensity curve along a vertical curve of the image at least in sections thereof.
11. The method according to claim 1 , wherein the providing of the modified image comprises displaying the modified image on a display device.
12. The method according to claim 1 , wherein the providing of the modified image comprises processing the modified image to detect objects in the vehicle environment.
13. The method according to claim 1 , wherein the scattered light and the brightening that is removed by the method are caused only by sunlight that is scattered from a lens hood of the vehicle camera.
14. A device for computationally removing brightening caused by scattered light from an image of a vehicle camera, the device comprising a vehicle camera and a processor unit,
wherein the vehicle camera is configured and equipped to be arranged on a vehicle so as to capture a captured image of an external environment of the vehicle, and
wherein the processor unit is configured to:
determine a curve of a total intensity within the captured image, wherein the total intensity includes a desired light intensity of desired light and a scattered light intensity of scattered light which reach an image capture coverage area of the vehicle camera and are included in the captured image,
estimate an approximation function of a lower limit of the scattered light intensity,
subtract the estimated approximation function of the lower limit of the scattered light intensity from the determined curve of the total intensity to produce a corrected intensity curve,
produce a modified image with corrected scattered light based on the corrected intensity curve, and
provide the modified image with corrected scattered light.