audio disc not illustrated the objective lens 21 is supported by a support mechanism which comprises a bobbin 22 of substantially cylindrical form a pair of leaf springs 23 and a block 24 specifically the leaf springs 23 are arranged in parallel with each other and connected to the upper and the lower ends of the bobbin 22 respectively with this support mechanism the objective lens 21 is allowed to move along its optical axis that is in directions of focusing indicated at an arrow f in the figure within a predetermined range of movement at the same time the objective lens 21 is supported by this support mechanism so that the optical axis thereof is maintained to be perpendicular to the recording surface of the digital audio disc a focusing coil 28 is wound around the bobbin 22 so that a central axis of the coil 28 is on the optical axis of the objective lens 21 as is shown in fig4 an inner space s 1 of the bobbin 22 and the surrounding coil 28 is reserved as a vacant space to accommodate the objective lens 21 and the light beam which passes therethrough when the objective lens 21 with its support is placed in the operating position the focusing coil 28 is located in a hollow vacant space s 2 formed in a magnetic circuit made up of a pair of confronting.