Showing papers on "Illumination problem published in 2004"

Illumination compensation methods for automatic fiber connector inspection

Abstract: Unevenly distributed image illumination is a problem in an automatic machine visual inspection system used for fiber connector defect detection. This unevenly distributed illumination makes it difficult to find an appropriate horizontal threshold to convert a gray-scale image to a binary image to separate surface defects, such as blobs and scratches, from the background of the connector. This paper proposes some effective methods to compensate the unevenly distributed illumination problem so that standard image processing methods can be used effectively to detect the defects of the fiber connectors.

Face recognition based on illumination restoration

Abstract: Variations in lighting conditions make face recognition an even more challenging and difficult task In this paper, a novel approach is proposed to handle the illumination problem Our method can restore a face image captured under arbitrary lighting conditions to one with frontal illumination by using a ratio-image and an iterative algorithm The restored images with frontal illumination are used for face recognition by means of PCA Experimental results demonstrate that our method can achieve a higher recognition rate, based on the Yale B and Yale database Moreover, our algorithm has several advantages over other previous algorithms: (1) it does not need to estimate the face surface normals and the light source directions; (2) it does not need many images captured under different lighting conditions for each person, nor a set of bootstrap images that includes many images with different illuminations; and (3) it does not need to detect accurate positions of some facial feature points and to warp the image for alignment, etc