Pixel defect correction device for line crawl
To enhance accuracy in correction of a defective pixel. An image of an object is captured using a digital camera, and stored in an image memory 14 . A processor 16 detects a defect, using pixels located in the vertical and horizontal directions relative to, in lines of the same color as, and separated by one line from, the focused line. With any defect found, the presence or absence of line crawl is next determined. When it is determined that line crawl is present, the presence or absence of a diagonal edge is then determined. Subsequently, the surrounding pixels used to correct a defective pixel are selected in consideration of whether or not line crawl or a diagonal edge are present.
1. A pixel defect correction device for correcting a defect in any pixel in a group of pixels arranged as predetermined, comprising:
defect detection means for detecting a defect in a focused pixel, using pixels surrounding the focused pixel; wherein the group of pixels are disposed on a single image sensor filtered by a color filter having two or more colors arranged in a predetermined array so that the group of pixels contain two or more color signals;
line crawl determination means for determining the presence or absence of line crawl, a wavelength of light passing through one color of a filter that reaches a deeper site under a light receiving surface of an image sensor resulting in electric charge that appears as noise in adjacent pixels, around a defective pixel;
correction means for correcting the defective pixel that uses pixels selected according to the presence or absence of a line crawl; and
diagonal edge determination means for determining the presence or absence of a diagonal edge which includes, as a part thereof, the defective pixel;
wherein when line crawl is present, the correction means corrects the defective pixel while using pixels selected according to the presence or absence of a diagonal edge.
2. A pixel defect correction device according to claim 1 , wherein
when it is determined that both line crawl and a diagonal edge are present, the correction means corrects the defective pixel using a plurality of pixels located in a diagonal direction relative to, and in lines of a same color, the defective pixel.
3. A pixel defect correction device according to claim 1 , wherein
when it is determined that line crawl is present and that no diagonal edge is present , the correction means corrects the defective pixel using a plurality of pixels located in vertical and horizontal directions relative to, and in lines of a same color as, the defective pixel.
4. A pixel defect correction device according to claim 1 , further comprising:
verification means for verifying, when line crawl is absent, a defect in the defective pixel, using a second set of surrounding pixels which are different from the surrounding pixels used by the defect detection means.
5. A pixel defect correction device according to claim 4 , wherein
when a defect is verified by the verification means, the correction means corrects the defective pixel using the second set of surrounding pixels, and
when a defect is not verified, the defective pixel is output without correction.
6. A pixel defect correction device according to claim 4 , wherein the surrounding pixels used by the defect detection means comprise a plurality of pixels located in a line of a same color as the focused pixel, and the second set of surrounding pixels comprises a plurality of pixels adjacent to the focused pixel.
7. A pixel defect correction device according to claim 1 , wherein the line crawl determination means determines the presence or absence of line crawl around a defective pixel by comparing a difference between a pixel value at a position of the focused pixel which is estimated using a plurality of pixels of a same color as, and located in lines separated by one line from, the focused pixel, and a pixel value at a position of the focused pixel which is estimated using a plurality of pixels of a same color as, and adjacent to, the focused pixel, with a threshold.
8. A pixel defect correction device according to claim 7 , wherein the threshold is variably set depending on a noise level of a pixel.