Method for positioning the mirrors of a triple axis laser gyrometer, in particular when starting the gyrometer

A method for positioning three translatable mirrors in a laser gyrometer comprising three laser ring cavities, the positioning being carried out when starting the gyrometer, each of the three laser ring cavities comprising an optical amplifier medium which can be excited so as to generate light waves, an optical cavity formed by a set of mirrors including two of the translatable mirrors, the length of said optical cavity depending on the position of said two translatable mirrors, said two translatable mirrors being displaceable in ranges of positions imparting to the optical cavity lengths at which the amplifier medium generates at least one laser wave, each of the three translatable mirrors being used in the formation of two of the optical cavities, the method comprising:

• a phase of prepositioning the three mirrors at an initial triplet of predetermined respective initial positions;
• a phase of displacing the three mirrors simultaneously in translation in ranges having an equal amplitude less than or equal to a highest intermode in a plurality of intermodes of the optical cavity, so as to ensure that each of the optical cavities passes through a length at which the amplifier medium offers a gain maximum, intensities of the laser waves respectively traveling through each of the optical cavities being measured for each triplet of positions which are occupied by the mirrors, wherein said intermodes are related to variations in voltages within a particular mode of the laser gyrometer;
• a phase of determining, on the basis of the three triplets of positions of the mirrors which respectively allowed each of the three cavities to offer a maximum intensity, the length of each of the three cavities at which said cavity provides a maximum intensity;
• a phase of determining a single final triplet of positions of the mirrors making it possible simultaneously to impart to the three cavities lengths at which they provide a maximum intensity;
• and
• a phase of positioning the mirrors at the final triplet of positions.