Reducing effects caused by formation of multiple foci in a deformable lens during changes of applanation of surfaces thereof

A method for operating an optical system having an optical axis, the method comprising at least the steps of:

• transmitting light, incident onto a front surface of the optical system having a first optical power, through two surfaces of constituent first and second lenslets of the optical system that are coaxial with the optical axis and in contact with one another at a first contact region having a first contact surface area and centered on the optical axis;
• changing an optical power of the optical system from the first optical power to a second optical power by axially repositioning a first of the two surfaces along the optical axis to form a second contact region between the first and second of the two surfaces, the second contact region having a substantially flat surface and having a second contact surface area different from the first contact surface area;
• characterized in, that the method further comprises:
• (i) altering an auxiliary external force to compress at least one auxiliary lenslet and a chosen lenslet of the constituent first and second lenslets against one another along the optical axis or to relax axial pressure exerted by one of the at least one auxiliary lenslet and the chosen lenslet on the other, thereby changing an applanated contact area between a surface of the at least one auxiliary lenslet and a surface of the chosen lenslet;
• and
• (b) shifting at least a portion of a circumferential edge of at least one of constituent lenslets of the optical system along the optical axis while substantially not affecting an axial position of a center of said at least one of constituent lenslets;
• and/or
• (ii) wherein at least one of
• said changing the optical power of the optical system from the first optical power to the second optical power by axially repositioning the first of the two surfaces along the optical axis, and
• said altering the auxiliary external force includes changing a degree of applanation of a first aspheric surface and/or a second aspheric surface of two facing each other surfaces of constituent lenslets of the optical system;
• and/or
• (d) applying a radially-directed load to a circumferential edge of at least one of constituent lenslets of the optical system;
• wherein each of said changing the optical power of the optical system from the first optical power to the second optical power, said altering an auxiliary external force, said shifting, said changing a degree of applanation of the first aspheric surface and/or the second aspheric surface, and said applying a radially-directed load is carried out reversibly, and
• wherein said shifting, and/or said changing a degree of applanation of the first aspheric surface and/or the second aspheric surface, and/or said applying a radially-directed load a corresponding step is/are performed on only a subset but not all of constituent lenslets of the optical system.