The invention relates to an electromechanical brake force booster for a hydraulic vehicle brake system. An input frame is determined as a special scene or a general scene. The cut pigtail has been eliminated. Furthermore, since the most of the diffraction grating body can be formed of a material having a low refractive index, it is possible to lower the height of the diffraction index body. The thus prepared magnetic material can be used in magnetic devices by virtue of the inexpensiveness and high magnetic properties. The probe, which is disposed on one end of the arm, is rotated in the radial direction of a dielectric recording medium by the rotation of the motor, causing accurate and quick tracking control and track access control.