External actuator for a deformable mirror

A mirror assembly comprising

• a mirror faceplate;
• a substrate having front and back surfaces facing toward and away from said faceplate, respectively, and a plurality of passages extending through the substrate along an axis substatially normal to said front and back surfaces;
• and
• a plurality of actuator devices each for controllably adjusting an axial spacing between an associated zone of the faceplate and the front surface of the substrate, each of said plurality of actuator devices including
• an active element having front and back faces facing axially toward and away from the back surface of the substrate, respectively, and an opening passing axially therethrough to form an extension of the respective passage, and capable of undergoing dimensional changes when exposed to at least one of electric and magnetic fields;
• means for subjecting said active element to compression, including
• an end element juxtaposed with the faceplate zone,
• resiliently yieldable spring means interposed between said end element and said front surface of said substrate,
• an elongated preloading element extending through the passage and said opening and having one end portion secured to said end element to constitute a preloading unit therewith, and another end portion remote from said one end portion, at least said another end portion having an external thread, and
• tensioning means juxtaposed with said back face of said active element around said other end portion of said preloading element and having an internal thread in meshing engagement with said external thread of said preloading element for deforming said spring means to the extent necessary for a restoring force of said spring means to exert a preload pressure of a desired magnitude to said back face of said active element;
• and
• means for individually applying to each of said active elements at least said one of said electric and magnetic fields of a controllably variable magnitude for adjusting the spacings to the desired extent.

An actuator device to be mounted in a mounted condition thereof on a support having front and back surfaces and a passage extending axially therethrough substantially normal to the front and back surfaces, comprising

• an active element having front and back faces facing axially toward and away from the back surface of the support, respectively, and an openign passing axially therethrough to form an extension of the passage in the mounted condition, and capable of undergoing dimensional changes when exposed to at least one of electric and magnetic fields;
• means for subjecting said active element in the mounted condition thereof to compression, including
• an end element having a front face and a back face facing axially away from and toward the front surface of said substrate in the mounted condition,
• resiliently yieldable spring means interposed between said end element and said front surface of said support,
• an elongated preloading element extending through the passage and said opening in the mounted condition and having one end portion secured to said end element to constitute a preloading unit therewith, and another end portion remote from said one end portion, at least said other end portion having an external thread, and
• tensioning means juxtaposed with said back face of said active element around said other end portion of said preloading element and having an internal thread in meshing engagement with said external thread of said preloading element for deforming said spring means to the extent necessary for a restoring force of said spring means to exert a preload pressure of a desired magnitude to said back face of said active element;
• and
• means for applying to said active element in the mounted condition thereof at least said one of said electric and magnetic fields of a controllably variable magnitude for adjusting the spacing of said front face of said end element from the front surface of the support of the desired extent.