In order to extract position and direction of the first joint line of a fingerprint for stable pattern positioning in fingerprint comparison, an apparatus for extracting fingerprint features comprises a vertical strip divider (11) for dividing digitized data of a fingerprint into data of a plurality of strips with straight lines parallel to a y direction; a projection calculator (12) for obtaining histograms, each of said histograms calculated by accumulating pixel values of each of said plurality of strips in an x direction perpendicular to said y direction; a valley candidate calculator (13) for detecting candidate valleys from said histograms, one of said histograms having a locally minimum value at each of said candidate valleys; and a valley information integrator (116) for calculating a position of a joint line of said fingerprint from positional information of said candidate valleys detected by said valley candidate calculator (13).

Before welding, the plug and the sleeve of the fuel rod being in the welding position at the welding station, the sleeve and the plug of the fuel rod are rotated about their common axis with the aid of rotation means, images are taken along the periphery of the fuel element to obtain digitized images, the digitized images are analyzed to determine the position of the joint plane between the sleeve and the plug of the fuel rod, and the rotation of the fuel element is verified. It is deduced whether it is possible to perform the welding or not. If welding is performed, images are taken of the fuel element along the periphery of the fuel element, in the vicinity of a joint line between the sleeve and the plug, to obtain digitized images which are analyzed to check the conformance of a weld made along the joint line.

A welding system for automatically welding two workpieces together at a joint. The system includes a welding box having an electrode for welding the workpieces together; a camera assembly for viewing selected regions of the workpieces including a first edge and a second edge of the joint; and a controller connected to the camera assembly and the welding box for receiving the location of the first edge and the second edge of the joint and calculating the centerline of the joint and providing an output signal representative of the difference of the relative position of the centerline of the joint and the centerline of the fusing element. In the preferred embodiment, a 2-axis light source illuminates the surface of the workpieces to better locate the centerline of the joint.

It is the object of the present invention to perform reduction conversion processing while suppressing the loss of fine line when carrying out the reduction conversion of an image expressing in binary values. The present invention has a reduction operator which logically calculates the value of a converted pixel from a detection of fine lines in the vertical or diagonal direction, a detection of fine lines in the horizontal or diagonal direction and from the value of the original pixel closest to the converted pixel, within a limited region wherein the main scanning pixel number is 2N and the sub-scanning pixel number is 2N original pixels.

A three-dimensional measurement apparatus of a slit light (or pseudo slit light) projection type that is adapted to prevent deterioration of measurement accuracy and to be easily miniaturized. Detected positions C1, C2 are adopted that are determined so as to correspond to scanning lines on each of which a number of brightened pixels falls within an allowable range are detected. The allowable range varies from Nav .times. amin to Nav .times. amax or from Nav-.beta. to Nav +.gamma., where Nav is an average of the numbers of brightened pixels detected on scanning lines for each of which at least one pixel is determined, and amin, amax, .beta., and .gamma. are minimum proper ratio, maximum proper ratio, subtract number of pixels, and add number of pixels, respectively, which are set in advance as parameters.