Patent ID: 8406557
Filing Date: 2013-03-26
Classification: H04N

Abstract:
1. A method for correcting lens shading in an image processing apparatus, comprising the steps of separating a white image captured by an image pickup device and an image pickup unit into reference white images corresponding to color channels; estimating a vignetting center having a maximum light intensity in each of the reference white images; defining multiple reference segments on each of the reference white images, wherein each of the reference segments has one endpoint at the vignetting center and another endpoint on a border of the corresponding reference white image; calculating a lens shading correction value corresponding to each pixel constituting the reference segments using a corresponding light intensity, and deriving a lens shading correction function corresponding to each reference segment using a corresponding calculated lens shading correction value; and removing vignetting of a general image received in a general image processing mode, using the derived multiple lens shading correction functions, wherein estimating a vignetting center comprises: (1) setting a center of an image pickup surface as a center candidate of a reference white image; (2) determining as a light-intensity center a part of the image pickup surface where a pixel has a maximum light intensity among pixels constituting a horizontal segment passing through the center candidate in the reference white image, and re-setting the light-intensity center as the center candidate; (3) re-determining as the light-intensity center a part of the image pickup surface where a pixel has a maximum light intensity among pixels constituting a vertical segment passing through the re-set center candidate in the reference white image, and re-setting the light-intensity center as the center candidate; and (4) determining a last center candidate as the vignetting center by iterating steps (2) and (3).