Blocking device for a semi-finished optical element

A blocking device for blocking a semi-finished optical element (11;

• 111) having a first face (14;
• 114) to which the blocking device (13;
• 113) is to be attached and having opposite to the first face (14;
• 114) a second face (15) to be surfaced in a surfacing machine (10) configured for holding the semi-finished optical element (11;
• 111) via the blocking device (13;
• 113), said blocking device (13;
• 113) comprising:
• a mounting portion (20) provided for mounting the blocking device (13;
• 113) on a corresponding mounting member (17) of said surfacing machine (10) ;
• and
• a blocking portion (21) configured for blocking said semi-finished optical element (11;
• 111) ;
• said blocking portion (21) comprising a support member configured for providing a rigid support to said semi-finished optical element (11;
• 111),
• wherein said support member includes a support element (23;
• 123) made of a shape-memory material comprising ferromagnetic elements (27), said support element having a rigid state below a predetermined temperature and a plastic state above said predetermined temperature, said support element (23;
• 123) assuming in the absence of external forces a predetermined memory shape when heated above said predetermined temperature, said support member having a contact face (25;
• 125) onto which said first face (14;
• 114) of said semi-finished optical element (11;
• 111) is to be applied;
• wherein said blocking portion (21) includes a heating device (36) configured for heating said support element above said predetermined temperature,
• wherein said ferromagnetic elements (27) configure said support element (23;
• 123) for being inductively heated above said predetermined temperature by the heating element (36),
• wherein the blocking device is further configured to generate a magnetic retaining effect.