External reservoir configuration for tunable acoustic gradient lens

An external reservoir configuration configured to be coupled to a tunable acoustic gradient (TAG) lens having a lens casing with a casing cavity configured to contain an operational volume of refractive fluid and a controllable acoustic wave generating element arranged inside the lens casing around an optical path that passes through the operational volume, wherein the operational volume of the refractive fluid is capable of changing its refractive index along the optical path in response to application of an acoustic wave by the acoustic wave generating element, and in accordance with which the TAG lens is controlled to provide a periodically modulated optical power variation for the TAG lens, the external reservoir configuration comprising:

• a deformable external fluid reservoir that is configured to contain refractive fluid;
• and
• a flow channel portion that is part of a flow channel that connects the deformable external fluid reservoir to the casing cavity of the TAG lens, wherein the deformable external fluid reservoir contains a reserve volume of the refractive fluid, and at least some of the refractive fluid is able to flow back and forth between the casing cavity and the deformable external fluid reservoir through the flow channel;
• and
• wherein the lens casing, the deformable external fluid reservoir and the flow channel are configured as a sealed system.

A method for preparing and operating a tunable acoustic gradient (TAG) lens having a lens casing with a casing cavity configured to contain an operational volume of refractive fluid and a controllable acoustic wave generating element arranged inside the lens casing around an optical path that passes through the operational volume, the method comprising:

• adding the refractive fluid to the casing cavity and to a deformable external fluid reservoir that is included in an external reservoir configuration and is connected to the casing cavity by a flow channel that passes through the lens casing, wherein the lens casing includes an inlet/outlet port and the external reservoir configuration includes an inlet/outlet port which are each open while the refractive fluid is added and through at least one of which the refractive fluid is provided so as to be added to the casing cavity and to the deformable external fluid reservoir;
• closing the inlet/outlet ports after the casing cavity is filled to contain the operational volume of the refractive fluid and the deformable external fluid reservoir is filled to contain a reserve volume of the refractive fluid at a current temperature of the refractive fluid;
• and
• controlling the TAG lens to provide a periodically modulated optical power variation for the TAG lens.