Method and apparatus for correcting vignetting effect caused on an image captured by lightfield cameras

Abstract

The disclosure addresses the vignetting effect caused on an image captured by lightfield camera. A method to compensate for the vignetting effect for a lightfield camera comprising an image sensor array including plurality of photosites. The method includes the operations of obtaining luminance values from the each photosite; obtaining a set of weight values for compensating the vignetting effect for the each photosite being associated with a present setting of the lightfield camera; and changing the luminance values of the each photosite based on the obtained a set of the weight values.

1 . A method for correcting vignetting effect caused by a lightfield camera ( 1 ) comprising
 obtaining an image sensor array including plurality of photosites and having a color filter array with having different colors associated with each photosite:   obtaining luminance values from each photosite;   obtaining a set of weight values for compensating the vignetting effect for one or more photosites, wherein said set of weight values is associated with a setting of the lightfield camera and   changing the luminance values of each photosite based on the obtained set of the weight values.   
     
     
         2 . The method according to  claim 1 , further comprising obtaining a luminance value of a color of said color filter on a photosite from the luminance values; 
     
     
         3 . The method according to  claim 2 , further comprising obtaining a correction value that corrects the luminance value affected by color of the color filter on the photosite. 
     
     
         4 . The method of  claim 3 , wherein the weight values are obtained by:
 receiving luminance values of each photosite ( 131 ,  132 ,  133 ,  13   p ) when a Lambertian object image is captured (SI);   determining a maximum luminance value from the received luminance values (S 2 ) and   dividing the maximum luminance value by the respective luminance values of each photosite when the Lambertian object image is captured .   
     
     
         5 . The method according to  claim 4 , wherein the weight value is determined by receiving luminance values of each photosite, when a Lambertian object image is captured. 
     
     
         6 . The method according to  claim 5 , wherein the weight value is obtained based on the luminance value of the photosite, the correction value and the maximum luminance value of a color. 
     
     
         7 . The method according to  claim 6 , wherein the calculating further comprises:
 determining a value by dividing the maximum luminance value of a color by the luminance value of the photosite ( 131 ,  132 ,  133 ,  13   p ); and   multiplying the determined value by the correction value (S 60 ).   
     
     
         8 . The method according to  claims 7 , further comprising comparing the luminance value of the photosite ( 131 ,  132 ,  133 ,  13   p ) with a threshold and if the luminance value of the photosite is less than the threshold setting the weight value of the photosite equal to 0. 
     
     
         9 . The method according to  claims 8 , wherein changing the luminance value of each photosite is performed by multiplying the luminance values of each photosite by the respective weight values associated with each photosite. 
     
     
         10 . The method of  claim 1  wherein the lightfield camera ( 1 ) further comprises a storage ( 87 ) storing sets of weight values and correcting values. 
     
     
         11 . The method of  claim 10  further comprising associating the respective sets of weight values with the respective photosite. 
     
     
         12 . The method of  claim 11 , wherein the respective correction values correct the luminance value affected by the color or the color filter on the photosite. 
     
     
         13 . A device for correcting vignetting effect caused on an image captured by a lightfield camera comprising:
 an image sensor array including plurality of photosite and having a color filter array having different colors associated with each photosite;   a storage for storing a set of weight values for compensating the vignetting effect for each photosite;   a processor configured to perform:   obtaining an image sensor array including plurality of photosites and having a color filter array with having different colors associated with each photosite:   obtaining luminance values from each photosite;   obtaining a set of weight values for compensating the vignetting effect for one or more photosites, wherein said set of weight values is associated with a setting of the lightfield camera.   
     
     
         14 . The device according to  claim 13 , wherein said processor obtains a luminance value of a color of said color filter on a photosite from the luminance values. 
     
     
         15 . The device of  claim 14 ,  claim 2 , wherein said processor obtains a correction value that corrects the luminance value affected by color of the color filter on the photosite. 
     
     
         16 . The device of  claim 15 , wherein the weight values are obtained by receiving luminance values of each photosite when a Lambertian object image is captured and said processor determines a maximum luminance value from the received luminance values (S 2 ). 
     
     
         17 . The method of  claim 16 , wherein said processor divides the maximum luminance value by the respective luminance values of each photosite when the Lambertian object image is captured. 
     
     
         18 . The device of  claim 13 , wherein the lightfield camera further comprises:
 a primary lens;   a lenslet array including a plurality of microlenses located between the image sensor array and the primary lens;   an additional lens being arranged between the primary lens ( 10 ) and the microlenses at a distance from the primary lens and the additional lens having a focal length corresponding to the distance.   
     
     
         19 . A lightfield camera comprising:
 a primary lens j;   microlenses;   an image sensor array ( 13 A) including a plurality of photosites ( 131 A,  132 A,  133 A to  13   p A);   wherein the photosites ( 131 A,  132 A,  133 A to  13   p A) have respective sensitivities adjusted for compensating a vignetting effect through obtaining a set of weight values to be caused on an image to be captured by the lightfield camera ( 1 A)   
     
     
         20 . A non-transitory tangible computer-readable medium comprising a computer program product recorded thereon and capable of being run by a processor, including program code instructions for implementing the steps comprising:
 obtaining an image sensor array including plurality of photosites and having a color filter array with having different colors associated with each photosite:   obtaining luminance values from each photosite;   obtaining a set of weight values for compensating the vignetting effect for one or more photosites, wherein said set of weight values is associated with a setting of the lightfield camera.