| 摘要 |
When welding optical fibers retained to form a fiber ribbon the end portions of the fibers are imaged by a lens system on a surface comprising CCD-elements in a camera. Since two such pictures must be made in approximately perpendicular directions in order to determine the positions of the fiber ends, the optical axis when capturing such a picture must be located obliquely to a plane through the end portions of the fiber ribbons. The oblique position of the object in the picture results in that the magnification of the end portions of the fibers will be different for different fibers and thereby also the background illumination will be different and the contrast in a captured image will vary in the different portions of the picture, which show different fibers. In order to achieve a homogenous background illumination a light source is placed in the radiation path behind the end portions (of the object) as seen from the camera and between the light source and the object a diaphragm, which is designed as a non-circular aperture, for example having the shape of a semicircle or a symmetric trapezoid. In order to even more improve the background illumination a light scattering plate is arranged between the diaphragm and the object.
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