Frequency setting of a horological oscillator by optomechanical deformations

A method for a fine adjustment of a rate of a mechanical horological oscillator comprising at least one inertial mass, arranged to oscillate about an axis of rotation and returned to a rest position by elastic return means, the method comprising:

• in a first step, said oscillator is equipped with at least one inertial mass including an actuator in a material suitable for irreversible local micro-expansion under the effect of laser fires, said actuator being arranged to impart to an inertia-block a radial linear travel with respect to the axis of rotation, directly or with at least one travel amplifier, when a writing zone, included in the actuator is subjected to suitable laser fires;
• in a second step, a first rough setting of an initial rate of said oscillator is performed in a first rate range and said rate is measured;
• in a third step, a direction and the value of the rate deviation to be imparted to said oscillator are calculated to bring it the rate into a predetermined second rate range, and a direction and a value of the travel to be imparted to each said inertia-block included in said oscillator are calculated;
• in a fourth step, at least one said writing zone is subjected to femtosecond laser fires to create at least one expansion line by local molecular expansion of said material to deform said actuator radially with respect to said axis of rotation;
• and
• in a fifth step, the rate of said oscillator is measured, and if required said third step and said fourth step are repeated until the rate of said oscillator is within said second rate range.