Abstract: A metrology system includes front and back vision components portions. The front vision components portion includes a light source, camera, variable focal length (VFL) lens, and objective lens defining an optical axis. The back vision components portion may include a reflective surface and a polarization altering component. A workpiece with apertures is located between the front and back vision components portions. For each aperture of the workpiece, the system adjusts a relative position between the front vision components portion and the workpiece to align its optical axis with each aperture such that light from the light source passes through the aperture and is reflected by the reflective surface of the back vision components portion. The system uses the VFL lens and camera to acquire an image stack including images of the aperture, and analyzes the image stack to determine a measurement related to a workpiece feature of the aperture.

Abstract: A metrology system includes front and back vision components portions. The front vision components portion includes a light source, camera, variable focal length (VFL) lens, and objective lens defining an optical axis. The back vision components portion may include a reflective surface and a polarization altering component. A workpiece with apertures is located between the front and back vision components portions. For each aperture of the workpiece, the system adjusts a relative position between the front vision components portion and the workpiece to align its optical axis with each aperture such that light from the light source passes through the aperture and is reflected by the reflective surface of the back vision components portion. The system uses the VFL lens and camera to acquire an image stack including images of the aperture, and analyzes the image stack to determine a measurement related to a workpiece feature of the aperture.

Abstract: A high-power fast-pulse driver and illumination system for high speed metrology imaging is provided, which includes an illumination source and a driver circuit configured to overdrive the illumination source using high currents and/or high current densities. The high currents are currents higher than manufacturer-recommended currents used to drive the illumination source and the high current densities are current densities higher than manufacturer-recommended current densities used to drive the illumination source. The illumination source is operated using a lifetime preserving technique selected from a first technique of operating the illumination source at low duty cycles of 2% or less or a second technique of operating the illumination source in a burst mode at higher duty cycles for short intervals. The driver and illumination system may be incorporated in a variable focus lens (VFL) system, to define multiple exposure increments for acquiring one or more images focused at one or more focus planes.

Abstract: A variable focal length lens system includes a tunable acoustic gradient (TAG) lens; a TAG lens controller; and processor(s) configured to: (a) operate the TAG lens controller to drive a periodic modulation of the TAG lens optical power at a TAG lens resonant frequency, using a first amplitude driving signal that provides a first focal Z range extending between peak focus distances Z1max+ and Z1max?; and expose a first image using a first exposure increment approximately at the timing of Z1max+ or Z1max?; (b) adjust the TAG lens controller to drive the periodic modulation using a second amplitude driving signal that provides a second focal Z range extending between peak focus distances Z2max+ and Z2max?; and expose a second image using a second exposure increment approximately at the timing of Z2max+ or Z2max?; and (c) perform processing that includes determining focus metric values for the first and second images.

Abstract: A system and method are provided for utilizing a focus state calibration object for determining calibration data for a variable focal length (VFL) lens system which includes a VFL lens (e.g., a tunable acoustic gradient lens). The calibration object includes a planar tilted pattern surface on which a set of focus state reference regions (FSRRs) are distributed (e.g., a tilted grating). The FSRRs have known geometric relationships relative to the planar tilted pattern surface and have known region relationships relative to one another. A plurality of camera images is acquired at different phase timings of the periodic modulation, and calibration data is determined based at least in part on analyzing the plurality of camera images. The determined calibration data indicates respective phase timings of the periodic modulation that correspond to respective effective focus positions of the VFL lens system.

Abstract: A triangulation sensing system includes a projection axis configuration and an imaging axis configuration. The projection axis configuration includes a triangulation light source (e.g. an incoherent source) and a variable focus lens (VFL) that is controlled to rapidly periodically modulate a triangulation light focus position (TLFP) along a Z axis over a focus position scan range, to provide a corresponding triangulation light extended focus range (TLEFR) that supports accurate measurement throughout. In some implementations, the triangulation system may be configured to provide the best measurement accuracy for a workpiece region of interest (WROI) by exposing its triangulation image only when the scanned TLFP temporarily coincides with the WROI Z height. In some implementations, the triangulation system may be configured to limit various measurement operations to using only an operational pixel subset of a detector that receives image light from the WROI, in order to shorten the measurement time.

Abstract: A variable focal length lens system includes a tunable acoustic gradient (TAG) lens; a TAG lens controller; a light source; a camera; and processor(s) configured to: (a) drive a periodic modulation of the TAG lens optical power, using a first amplitude driving signal that provides a first amplitude of the periodic modulation at a resonant frequency of the TAG lens, the first amplitude corresponding to a first focal Z range extending between peak focus distances Z1max+ and Z1max?, wherein the first amplitude driving signal is selected based on a first target focus distance Ztarget?1 and calibration data which relates different amplitude driving signals to different target focus distances Ztarget?i; and (b) operate the light source and camera to expose an image using at least one exposure increment wherein the focus distance during the exposure increment moves over a first exposure Z range that includes target focus distance Ztarget?1.

Abstract: A variable focal length lens system includes a tunable acoustic gradient (TAG) lens; a TAG lens controller; and processor(s) configured to: (a) operate the TAG lens controller to drive a periodic modulation of the TAG lens optical power at a TAG lens resonant frequency, using a first amplitude driving signal that provides a first focal Z range extending between peak focus distances Z1max+ and Z1max?; and expose a first image using a first exposure increment approximately at the timing of Z1max+ or Z1max?; (b) adjust the TAG lens controller to drive the periodic modulation using a second amplitude driving signal that provides a second focal Z range extending between peak focus distances Z2max+ and Z2max?; and expose a second image using a second exposure increment approximately at the timing of Z2max+ or Z2max?; and (c) perform processing that includes determining focus metric values for the first and second images.

Abstract: A variable focal length lens system includes a tunable acoustic gradient (TAG) lens; a TAG lens controller; a light source; a camera; and processor(s) configured to: (a) drive a periodic modulation of the TAG lens optical power, using a first amplitude driving signal that provides a first amplitude of the periodic modulation at a resonant frequency of the TAG lens, the first amplitude corresponding to a first focal Z range extending between peak focus distances Z1max+ and Z1max?, wherein the first amplitude driving signal is selected based on a first target focus distance Ztarget?1 and calibration data which relates different amplitude driving signals to different target focus distances Ztarget?i; and (b) operate the light source and camera to expose an image using at least one exposure increment wherein the focus distance during the exposure increment moves over a first exposure Z range that includes the target focus distance Ztarget?1.

Abstract: A triangulation sensing system includes a projection axis configuration and an imaging axis configuration. The projection axis configuration includes a triangulation light source (e.g. an incoherent source) and a variable focus lens (VFL) that is controlled to rapidly periodically modulate a triangulation light focus position (TLFP) along a Z axis over a focus position scan range, to provide a corresponding triangulation light extended focus range (TLEFR) that supports accurate measurement throughout. In some implementations, the triangulation system may be configured to provide the best measurement accuracy for a workpiece region of interest (WROI) by exposing its triangulation image only when the scanned TLFP temporarily coincides with the WROI Z height. In some implementations, the triangulation system may be configured to limit various measurement operations to using only an operational pixel subset of a detector that receives image light from the WROI, in order to shorten the measurement time.

Abstract: A high-power fast-pulse driver and illumination system for high speed metrology imaging is provided, which includes an illumination source and a driver circuit configured to overdrive the illumination source using high currents and/or high current densities. The high currents are currents higher than manufacturer-recommended currents used to drive the illumination source and the high current densities are current densities higher than manufacturer-recommended current densities used to drive the illumination source. The illumination source is operated using a lifetime preserving technique selected from a first technique of operating the illumination source at low duty cycles of 2% or less or a second technique of operating the illumination source in a burst mode at higher duty cycles for short intervals. The driver and illumination system may be incorporated in a variable focus lens (VFL) system, to define multiple exposure increments for acquiring one or more images focused at one or more focus planes.

Abstract: A triangulation sensing system includes a projection axis configuration and an imaging axis configuration. The projection axis configuration includes a triangulation light source (e.g. an incoherent source) and a variable focus lens (VFL) that is controlled to rapidly periodically modulate a triangulation light focus position (TLFP) along a Z axis over a focus position scan range, to provide a corresponding triangulation light extended focus range (TLEFR) that supports accurate measurement throughout. In some implementations, the triangulation system may be configured to provide the best measurement accuracy for a workpiece region of interest (WROI) by exposing its triangulation image only when the scanned TLFP temporarily coincides with the WROI Z height. In some implementations, the triangulation system may be configured to limit various measurement operations to using only an operational pixel subset of a detector that receives image light from the WROI, in order to shorten the measurement time.

Abstract: A method is provided for operating a tunable acoustic gradient (TAG) lens imaging system. The method includes: (a) providing a smart lighting pulse control routine/circuit (SLPCRC) that provides a first mode of exposure control corresponding to a points from focus (PFF) mode of the TAG lens imaging system and a second mode of exposure control corresponding to an extended depth of focus (EDOF) mode of the TAG lens imaging system; (b) placing a workpiece in a field of view of the TAG lens imaging system; and (c) periodically modulating a focus position of the TAG lens imaging system without macroscopically adjusting the spacing between elements in the TAG lens imaging system, wherein the focus position is periodically modulated over a plurality of focus positions along a focus axis direction in a focus range including a surface height of the workpiece, at a modulation frequency of at least 30 kHz.

Abstract: A system and method are provided for utilizing a focus state calibration object for determining calibration data for a variable focal length (VFL) lens system which includes a VFL lens (e.g., a tunable acoustic gradient lens). The calibration object includes a planar tilted pattern surface on which a set of focus state reference regions (FSRRs) are distributed (e.g., a tilted grating). The FSRRs have known geometric relationships relative to the planar tilted pattern surface and have known region relationships relative to one another. A plurality of camera images is acquired at different phase timings of the periodic modulation, and calibration data is determined based at least in part on analyzing the plurality of camera images. The determined calibration data indicates respective phase timings of the periodic modulation that correspond to respective effective focus positions of the VFL lens system.

Abstract: A method is provided for operating a tunable acoustic gradient (TAG) lens imaging system. The method includes: (a) providing a smart lighting pulse control routine/circuit (SLPCRC) that provides a first mode of exposure control corresponding to a points from focus (PFF) mode of the TAG lens imaging system and a second mode of exposure control corresponding to an extended depth of focus (EDOF) mode of the TAG lens imaging system; (b) placing a workpiece in a field of view of the TAG lens imaging system; and (c) periodically modulating a focus position of the TAG lens imaging system without macroscopically adjusting the spacing between elements in the TAG lens imaging system, wherein the focus position is periodically modulated over a plurality of focus positions along a focus axis direction in a focus range including a surface height of the workpiece, at a modulation frequency of at least 30 kHz.

Abstract: A variable focal length (VFL) lens system is provided including a VFL lens, a VFL lens controller, an objective lens, a camera and an optical power monitoring configuration. During a standard workpiece imaging mode, the objective lens transmits workpiece light along an imaging optical path through the VFL lens to the camera, which provides a corresponding workpiece image exposure. During an optical power monitoring mode, the optical power monitoring configuration produces a monitored beam pattern which travels along at least a portion of the imaging optical path through the VFL lens to the camera, which provides a monitoring image exposure. Different monitoring image exposures are acquired at different phase timings of the periodic modulation of the VFL lens, and a dimension of the monitored beam pattern is measured in each monitoring image exposure as related to an optical power of the VFL lens at the corresponding phase timing.

Abstract: A focus state reference subsystem comprising a focus state (FS) reference object is provided for use in a variable focal length (VFL) lens system comprising a VFL lens, a controller that modulates its optical power, and a camera located along an optical path including an objective lens and the VFL lens. Reference object image light from the FS reference object is transmitted along a portion of the optical path through the VFL lens to the camera. Respective FS reference regions (FSRRs) of the FS reference object include a contrast pattern fixed at respective focus positions. A camera image that includes a best-focus image of a particular FSRR defines a best-focus reference state associated with that FSRR, wherein that best-focus reference state comprises a VFL optical power and/or effective focus position of the VFL lens system through the objective lens.

Abstract: A variable focal length (VFL) lens system is provided including a VFL lens, a VFL lens controller, an objective lens, a camera and an optical power monitoring configuration. During a standard workpiece imaging mode, the objective lens transmits workpiece light along an imaging optical path through the VFL lens to the camera, which provides a corresponding workpiece image exposure. During an optical power monitoring mode, the optical power monitoring configuration produces a monitored beam pattern which travels along at least a portion of the imaging optical path through the VFL lens to the camera, which provides a monitoring image exposure. Different monitoring image exposures are acquired at different phase timings of the periodic modulation of the VFL lens, and a dimension of the monitored beam pattern is measured in each monitoring image exposure as related to an optical power of the VFL lens at the corresponding phase timing.

Abstract: A method is provided for operating an imaging system to maintain a tunable acoustic gradient (TAG) lens at a desired operating state. In a first step, the TAG lens operates using a standard imaging drive control configuration (e.g., a standard drive voltage and duration) during a plurality of imaging drive mode time periods, to achieve a standard imaging state of the TAG lens. In a second step, the TAG lens operates using a regulating adaptive drive control configuration during a plurality of regulating adaptive drive mode time periods, wherein at least one of a different respective TAG lens drive voltage and a different respective TAG lens drive duration is used for different respective regulating adaptive drive mode time periods, based on a monitoring signal that is indicative of a difference between the standard imaging state and a current operating state of the TAG lens.

Abstract: A method is provided for operating an imaging system to maintain a tunable acoustic gradient (TAG) lens at a desired operating state. In a first step, the TAG lens operates using a standard imaging drive control configuration (e.g., a standard drive voltage and duration) during a plurality of imaging drive mode time periods, to achieve a standard imaging state of the TAG lens. In a second step, the TAG lens operates using a regulating adaptive drive control configuration during a plurality of regulating adaptive drive mode time periods, wherein at least one of a different respective TAG lens drive voltage and a different respective TAG lens drive duration is used for different respective regulating adaptive drive mode time periods, based on a monitoring signal that is indicative of a difference between the standard imaging state and a current operating state of the TAG lens.