Abstract: Optical method for determining the lateral gap of two pieces (1, 2) having adjacent edges (3, 4) forming a slot (5) consisting in emitting a parallel light beam (8) through at least one zone of said slot, from one side of the latter; in detecting the beam (8a) passing through this zone of said slot, at the other side of the latter; and in comparing the light intensity of this beam transversing said zone with a predetermined value so as to obtain or to provide the gap between the edges of said pieces in said zone. This method may be applied to the positioning of a first piece, such as a chip, opposite or in an opening made in a second piece, such as a substrate, and may consist in moving said first piece in order to bring it above the opening of the second piece, in comparing, as the first piece moves, the light intensity passing through the slot separating said pieces and in stopping the movement of the first piece when the intensity of the light through-beam is equal to a predetermined value.

Abstract: An optical method and optical device for distance measurement, comprising the steps of emitting an incident light beam (13) comprising at least two waves of differing wavelengths (.lambda.1 and .lambda.2); separating this beam into a reference beam (15) and a measurement beam (17) which are reflected on, respectively, a reference reflector (16) and a zone (18) of a part (19), of which it is desired to measure the position in the direction of the measurement beam and recombine into a resultant beam (20), in which said waves exhibit conditions of polarization, the components of which rotate when the optical path of the aforementioned measurement beam varies and which determine, in the direction of the measurement beam, adjacent ranges at the ends of each one of which the angular positions of two corresponding components of these conditions of polarization are identical; determining, in the resultant beam (20), the angular positions (.alpha.1 and .alpha.