Tunable acoustic gradient lens system with reflective configuration and increased power

A method for operating a tunable acoustic gradient (TAG) lens system which includes a TAG lens, the method comprising:

• providing a control signal that controls a drive signal of the TAG lens to periodically modulate optical power of the TAG lens over a range of optical powers that occur at respective phase timings within the periodic modulation;
• operating a camera to receive light transmitted along an imaging optical path during an image exposure and provide a corresponding camera image, wherein the imaging optical path includes the TAG lens, wherein the system includes an objective lens that inputs workpiece light arising from a workpiece during a workpiece image exposure and transmits the workpiece light along the imaging optical path to the TAG lens which provides workpiece light to the camera during the workpiece image exposure, to provide a workpiece image in a corresponding camera image, wherein an effective focus position in front of the objective lens during a workpiece image exposure corresponds to the optical power of the TAG lens during that workpiece image exposure;
• and
• providing a control signal for controlling an image exposure timing used for a camera image,
• wherein the TAG lens comprises:
• a controllable acoustic wave generating element;
• a refractive fluid;
• and
• a lens casing surrounding a casing cavity, wherein:
• an operational volume of the refractive fluid is contained in the casing cavity and the controllable acoustic wave generating element is arranged inside the lens casing around an optical path that passes through the operational volume, and an axial direction of the TAG lens is defined as parallel to an optical axis of the optical path;
• and
• 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, in accordance with which the TAG lens is controlled to provide a periodically modulated optical power variation for the TAG lens when a periodic drive signal is applied to the acoustic wave generating element;
• and
• the lens casing comprises:
• a case wall portion that extends generally along the axial direction;
• a first case end portion that extends generally transverse to the axial direction and comprises a centrally located window configuration comprising a window mounted along the optical path in a window mounting portion and a case end rim portion that is at least partially aligned with and sealed to the case wall portion;
• and
• a second case end portion that extends generally transverse to the axial direction and comprises a centrally located mirror configuration comprising a mirror mounted along the optical path in a mirror mounting portion and a case end rim portion that is at least partially aligned with and sealed to the case wall portion;
• and
• wherein workpiece light from the objective lens passes through the window of the TAG lens to enter the TAG lens and makes a first pass through the operational volume of the refractive fluid and is reflected by the mirror of the TAG lens and makes a second pass back through the operational volume of the refractive fluid and passes back out through the window of the TAG lens to exit the TAG lens and continue along the optical path to the camera.

A tunable acoustic gradient (TAG) lens comprising:

• a controllable acoustic wave generating element;
• a refractive fluid;
• and
• a lens casing surrounding a casing cavity, wherein:
• an operational volume of the refractive fluid is contained in the casing cavity and the controllable acoustic wave generating element is arranged inside the lens casing around an optical path that passes through the operational volume, and an axial direction of the TAG lens is defined as parallel to an optical axis of the optical path;
• and
• 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, in accordance with which the TAG lens is controlled to provide a periodically modulated optical power variation for the TAG lens when a periodic drive signal is applied to the acoustic wave generating element;
• and
• the lens casing comprises:
• a case wall portion that extends generally along the axial direction;
• a first case end portion that extends generally transverse to the axial direction and comprises a centrally located window configuration comprising a window mounted along the optical path in a window mounting portion and a case end rim portion that is at least partially aligned with and sealed to the case wall portion;
• and
• a second case end portion that extends generally transverse to the axial direction and comprises a centrally located mirror configuration comprising a mirror mounted along the optical path in a mirror mounting portion and a case end rim portion that is at least partially aligned with and sealed to the case wall portion,
• wherein the TAG lens is configured to enable light to pass through the window of the TAG lens to enter the TAG lens and make a first pass through the operational volume of the refractive fluid and be reflected by the mirror of the TAG lens and make a second pass back through the operational volume of the refractive fluid and pass back out through the window of the TAG lens to exit the TAG lens and continue along the optical path.