System and method for aligning the optical axis of an optical component part to be perpendicular to a workpiece surface using multi-point autofocus

Abstract

A metrology system includes an optical assembly portion; an adjustment mechanism configured to change the distance and angular orientation between the optical assembly portion and a workpiece surface; and a processor configured to control the adjustment mechanism to move the optical assembly portion to position the workpiece surface within a focal Z autofocus range; capture an image stack of the workpiece surface, wherein each image of the image stack corresponds to a different autofocus height; determine the autofocus heights of at least three locations of the workpiece surface; control the adjustment mechanism based on the autofocus heights to rotate the optical assembly portion relative to the workpiece surface so that the optical axis of the optical assembly portion is nominally aligned with a surface normal of the workpiece surface and adjust the distance between the optical assembly portion and the workpiece surface; and perform a defined operation on the workpiece surface.

Description

Technical Field

[0001] The present disclosure relates to precision metrology, and more particularly, to using multi-point autofocus to align an optical axis perpendicular to a workpiece surface to improve the accuracy of subsequent operations (eg, measurement operations, etc.) to be performed on the workpiece surface. Background Art

[0002] Precision metrology systems, such as precision machine vision inspection systems (or simply "vision systems"), can be used to obtain accurate dimensional measurements of objects and inspect various other object characteristics, and may include computers, cameras, and optical systems, as well as precision stages that move to allow workpieces to be moved and inspected. An exemplary prior art system is the QUICK Series of PC-based vision systems and For example, the QVPAK 3D CNC Vision Measuring Machine User Guide, published in January 2003, generally describes QUICK Series of vision systems and Features and operation of the software, which is hereby incorporated herein by reference in its entirety.This type of system uses a microscope-type optical system and a moving stage to provide inspection images of small or relatively large workpieces.

[0003] General-purpose precision machine vision inspection systems are often programmable to provide automated video inspection. Such systems often include selectable modes of operation as well as GUI features and predefined image analysis "video tools" so that "non-expert" operators can perform operations and programming. For example, U.S. Patent 6,542,180, the entire contents of which are incorporated herein by reference, teaches the use of a vision system that includes automated video inspection using various video tools.

[0004] Variable focal length (VFL) optical systems can be used for observation and precise measurement of surface heights and can be included in precision machine vision inspection systems or other optical systems, such as disclosed in U.S. Patent 9,143,674, which is incorporated herein by reference in its entirety. In short, a VFL lens is capable of acquiring multiple images at multiple focal lengths, respectively. Various types of VFL lenses are known, such as mechanical VFL lenses, in which a multi-lens system is mechanically moved to change its focal length, or non-mechanical VFL lenses, such as adjustable acoustic gradient ("TAG") lenses, which use acoustic waves in a fluid medium to produce a lens effect (to change its focal length). For example, a VFL lens in a precision machine vision inspection system can be used to acquire images of a workpiece at multiple surface heights or "Z heights" of a machine coordinate system (MCS).

[0005] Such configurations are typically only capable of performing certain types of operations (e.g., acquisition of image stacks) from a single direction (e.g., along the Z-axis of the MCS). A system that can provide improvements with respect to such operations (e.g., with respect to workpieces having tilted and / or complex surfaces, etc.) would be desirable. Summary of the invention

[0006] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0007] According to one aspect, a metrology system is provided that includes: an optical assembly portion; an adjustment mechanism; one or more processors; and a memory coupled to the one or more processors and storing program instructions.

[0008] The optical component part includes a light source; an objective lens, which inputs image light generated by the workpiece surface illuminated by the light source and transmits the image light along an imaging light path, wherein the objective lens defines an optical axis of the optical component part, and the optical axis extends at least between the objective lens and the workpiece surface; and a camera, which receives the imaging light transmitted along the imaging light path and provides an image of the workpiece surface.

[0009] The adjustment mechanism is configured to change the distance between the optical assembly portion and the workpiece surface and to rotate the optical assembly portion relative to the workpiece surface to change the angular orientation of the optical axis of the optical assembly portion relative to the workpiece surface.

[0010] When executed by one or more processors, the program instructions stored in the memory cause the one or more processors to at least:

[0011] The adjustment mechanism is controlled to move the optical component part to position the workpiece surface within the focal point Z auto-focus range of the optical component part.

[0012] capturing an image stack of the workpiece surface within a focal point Z autofocus range using the optical assembly portion, wherein the image stack includes a plurality of images of the workpiece surface and each image of the image stack corresponds to a different autofocus height;

[0013] determining auto-focus heights for at least three locations on the workpiece surface based on at least three corresponding regions of interest of the image stack;

[0014] controlling an adjustment mechanism based at least in part on the autofocus heights at at least three locations to: rotate the optical assembly portion relative to the workpiece surface to nominally align an optical axis of the optical assembly portion with a surface normal to the workpiece surface; and adjust a distance of the optical assembly portion from the workpiece surface; and

[0015] Perform defined operations on the workpiece surface.

[0016] According to another aspect, the optical assembly portion further comprises a variable focal length (VFL) lens included in an imaging optical path, and wherein the objective lens transmits image light through the VFL lens along the imaging optical path and the camera receives the imaging light transmitted by the VFL lens along the imaging optical path. The VFL lens may be a tunable acoustic gradient (TAG) lens configured to non-mechanically change the focal length, and to this end, the periodically modulated focus position of the optical assembly portion is controlled by periodically modulating the optical power of the TAG lens. The defined operation performed on the workpiece surface may include capturing one or more images of the workpiece surface using the VFL lens. The defined operation performed on the workpiece surface may include capturing an image stack using the VFL lens while the optical axis of the optical assembly portion is nominally aligned with the surface normal of the workpiece surface, to which end the image stack includes multiple images of the workpiece surface and each image of the image stack corresponds to a different focus position of the optical assembly portion along the direction of the optical axis.

[0017] According to another aspect, determining auto-focus heights for at least three locations on the workpiece surface includes determining focus curve data for each region of interest based at least in part on an analysis of images of the image stack, wherein for each of the at least three locations, a peak of the focus curve data for the corresponding region of interest indicates a corresponding auto-focus height.

[0018] According to another aspect, the program instructions, when executed by the one or more processors, further cause the one or more processors to:

[0019] determining a surface normal to the surface of the workpiece based at least in part on the auto-focus heights at at least three locations; and

[0020] Adjustment information is determined to control an adjustment mechanism to rotate the optical component portion based at least in part on the determined surface normal.

[0021] According to another aspect, the defining operation may include a measuring operation for determining dimensions of features of the workpiece surface.

[0022] According to another aspect, the limiting operation may include a points-from-focus (PFF) operation including:

[0023] acquiring an image stack comprising a plurality of images, each image corresponding to a focus position of a portion of the optical assembly along an imaging optical axis coinciding with the optical axis, and

[0024] Focus curve data is determined based at least in part on an analysis of images of the image stack, wherein the focus curve data indicates 3-dimensional positions of a plurality of surface points on a surface of the workpiece.

[0025] According to another aspect, the defining operation may include a machining operation performed on the workpiece surface, wherein a machining axis of the machining operation is at least one of: nominally coincident with an optical axis of the optical component portion or nominally parallel thereto.

[0026] According to another aspect, the adjustment mechanism may include a rotation mechanism and a Z-axis movement mechanism, wherein the Z-axis movement mechanism is coupled to move the optical component portion along the Z-axis direction, and the rotation mechanism is coupled between the Z-axis movement mechanism and the optical component portion and is configured to rotate the optical component portion relative to the workpiece surface to change the angular orientation of the optical axis of the optical component portion relative to the workpiece surface. The metrology system may be embodied in a precision machine vision inspection system, wherein the adjustment mechanism includes a rotation table, which includes the rotation mechanism and is coupled between the Z-axis movement mechanism and the optical component portion.

[0027] According to another aspect, the metrology system may be embodied in a coordinate measuring machine system, wherein the adjustment mechanism comprises:

[0028] an x-axis sliding mechanism, a y-axis sliding mechanism and a z-axis sliding mechanism, which are configured to move the optical assembly portion in mutually orthogonal x-axis, y-axis and z-axis directions, respectively, within a machine coordinate system, and

[0029] The rotation mechanism is configured to rotate the optical assembly portion relative to the workpiece surface.

[0030] According to another aspect, the metrology system can be embodied in a robotic system, wherein the adjustment mechanism includes a robotic arm having at least three degrees of freedom for moving the optical assembly portion.

[0031] According to another aspect, there is provided a method for operating a metrology system including an optical assembly portion, wherein the optical assembly portion includes:

[0032] light source;

[0033] an objective lens that inputs image light generated by a workpiece surface illuminated by the light source and transmits the image light along an imaging light path, wherein the objective lens defines an optical axis of the optical assembly portion, the optical axis extending at least between the objective lens and the workpiece surface; and

[0034] A camera receives imaging light transmitted along the imaging light path and provides an image of the workpiece surface.

[0035] The method includes:

[0036] moving the optical assembly part to position the workpiece surface within a focal point Z autofocus range of the optical assembly part;

[0037] capturing an image stack of the workpiece surface within a focal point Z autofocus range using the optical assembly portion, wherein the image stack includes a plurality of images of the workpiece surface and each image of the image stack corresponds to a different autofocus height;

[0038] determining auto-focus heights for at least three locations on the workpiece surface based on at least three corresponding regions of interest of the image stack;

[0039] determining, based at least in part on the autofocus heights at the at least three locations, adjustment information for rotating the optical assembly portion relative to the workpiece surface to nominally align an optical axis of the optical assembly portion with a surface normal of the workpiece surface and for adjusting a distance of the optical assembly portion from the workpiece surface;

[0040] rotating the optical component portion using the adjustment information to nominally align an optical axis of the optical component portion with a surface normal of a workpiece surface and to adjust a distance of the optical component portion from the workpiece surface; and

[0041] Perform defined operations on the workpiece surface.

[0042] According to another aspect, the method further includes determining a surface normal of the workpiece surface based at least in part on the auto-focus heights at the at least three locations, wherein the adjustment information is determined based at least in part on the determined surface normal.

[0043] According to another aspect, the workpiece surface is a first workpiece surface of the workpiece and after performing the first defining operation on the first workpiece surface, the method further comprises:

[0044] moving the optical assembly portion to position a second workpiece surface of the workpiece within a focal point Z autofocus range of the optical assembly portion;

[0045] capturing, using the optical assembly portion, an image stack of the second workpiece surface within the focal point Z autofocus range, wherein the image stack includes a plurality of images of the second workpiece surface and each image of the image stack corresponds to a different autofocus height;

[0046] determining auto-focus heights for at least three locations of the second workpiece surface based on at least three corresponding regions of interest of the image stack;

[0047] determining, based at least in part on the autofocus heights at the at least three locations, adjustment information for rotating the optical assembly portion relative to a second workpiece surface to nominally align an optical axis of the optical assembly portion with a surface normal of the second workpiece surface and for adjusting a distance of the optical assembly portion from the second workpiece surface;

[0048] rotating the optical component portion using the adjustment information to nominally align an optical axis of the optical component portion with a surface normal of a second workpiece surface and to adjust a distance of the optical component portion from the second workpiece surface; and

[0049] A defined operation is performed on the second workpiece surface.

[0050] According to yet a further aspect, a metrology system is provided, comprising an optical assembly portion; a Z-axis movement mechanism configured to change a distance between the optical assembly portion and a surface of a workpiece; a rotation mechanism configured to rotate the optical assembly portion relative to the surface of the workpiece to change an angular orientation of an optical axis of the optical assembly portion relative to the surface of the workpiece; one or more processors; and a memory coupled to the one or more processors and storing program instructions.

[0051] The optical component portion includes a variable focal length (VFL) lens; a light source; an objective lens, which inputs image light generated by a workpiece surface illuminated by the light source and transmits the image light along an imaging light path passing through the VFL lens, wherein the objective lens defines an optical axis of the optical component portion, and the optical axis extends at least between the objective lens and the workpiece surface; and a camera, which receives the imaging light transmitted through the VFL lens along the imaging light path and provides an image of the workpiece surface.

[0052] When executed by one or more processors, the program instructions stored in the memory cause the one or more processors to at least:

[0053] At least one of the Z-axis moving mechanism or the rotating mechanism is controlled to move the optical assembly part to position the workpiece surface within a focal point Z auto-focus range of the optical assembly part.

[0054] capturing an image stack of the workpiece surface within a focal point Z autofocus range using the optical assembly portion, wherein the image stack includes a plurality of images of the workpiece surface and each image of the image stack corresponds to a different autofocus height;

[0055] determining auto-focus heights for at least three locations on the workpiece surface based on at least three corresponding regions of interest of the image stack;

[0056] Based at least in part on the autofocus heights at the at least three positions, controlling a rotation mechanism to rotate the optical assembly portion relative to the workpiece surface to nominally align an optical axis of the optical assembly portion with a surface normal of the workpiece surface and controlling a Z-axis movement mechanism to adjust a distance of the optical assembly portion from the workpiece surface; and

[0057] Perform defined operations on the workpiece surface.

[0058] Thus, according to the principles disclosed herein, systems and methods are provided that include utilizing multi-point autofocus to align an optical axis of an optical component portion to be nominally perpendicular to an arbitrary workpiece surface. The systems and methods are capable of rapidly performing multi-point autofocus on a workpiece surface to derive adjustment information required to adjust the optical axis of the optical component portion to be nominally perpendicular to the workpiece surface. Systems and methods for rapidly (re)orienting an optical axis to be nominally perpendicular to a workpiece surface can be used to inspect various types of workpiece surfaces, such as free-form workpiece surfaces (e.g., turbine blades), where, for example, the surface normal may be constantly changing along different portions of the surface or different surfaces. The systems and methods can also be used for automatic alignment / positioning relative to a workpiece surface for subsequent non-optical operations, such as machining (e.g., drilling) operations to be performed on a workpiece surface, where the machining operation axis coincides with the optical axis. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 is a diagram showing various typical components of a general precision machine vision inspection system, the system including an optical assembly portion;

[0060] Figure 2A is with Figure 1 a block diagram of a control system portion and a vision component portion of a machine vision inspection system similar to and including certain features disclosed herein, wherein an optical axis of an optical assembly portion is in an initial orientation in which a multi-point autofocus process can be performed to determine a surface normal of a workpiece surface;

[0061] Figure 2B yes Figure 2A A block diagram of a machine vision inspection system wherein a vision component portion is controlled to orient an optical axis of an optical assembly portion to be nominally perpendicular to a workpiece surface;

[0062] Figure 3A is a schematic diagram of a VFL(TAG) lens system suitable for use in precision metrology systems such as machine vision inspection systems, wherein an optical axis of an optical component portion is in an initial orientation in which a multi-point autofocus process can be performed to determine a surface normal of a workpiece surface;

[0063] Figure 3B yes Figure 3A Schematic diagram of a VFL (TAG) lens system controlled to orient the optical axis of the optical assembly portion to be nominally perpendicular to the workpiece surface;

[0064] Figure 4 It shows Figure 3A and 3B Timing diagram of the periodic modulation of the VFL (TAG) lens system;

[0065] Figure 5Aillustrates a sample workpiece including first and second workpiece surfaces at different angular orientations;

[0066] Figure 5B is a schematic diagram of a portion of an optical assembly in an initial orientation in which a multi-point autofocus process may be performed to determine a surface normal of a workpiece surface;

[0067] Figure 5C It shows Figure 5B A schematic diagram of an optical axis of a portion of an optical assembly oriented nominally perpendicular to a workpiece surface;

[0068] Fig. 6A and 6B illustrates an image stack and the corresponding focus curve that can be used as part of a multi-point autofocus process to determine the surface normal of a workpiece surface;

[0069] Figure 7 A robotic system is shown that embodies a metrology system including an optical assembly portion according to one aspect of the present disclosure;

[0070] Fig. 8A illustrates a coordinate measuring machine (CMM) embodying a metrology system including an optical assembly portion according to an aspect of the present disclosure;

[0071] Figure 8B is a schematic diagram showing coupling to a Fig. 8A A diagram of the optical assembly portion of the probe head of the CMM shown in;

[0072] Figure 8C yes Fig. 8A A schematic diagram of a portion of a CMM, wherein the optical assembly portion is in an initial orientation in which a multi-point autofocus process can be performed to determine a surface normal of a workpiece surface;

[0073] Fig.8D yes Fig. 8A A schematic diagram of a portion of a CMM showing that the optical axis of the optical assembly portion is oriented nominally perpendicular to the workpiece surface;

[0074] Fig. 8E It shows that Fig. 8A A block diagram of the various control elements of the CMM; and

[0075] Fig. 9 is a flow chart of a method for aligning an optical axis to be nominally perpendicular to a workpiece surface using multi-point autofocus according to one aspect of the present disclosure. DETAILED DESCRIPTION

[0076] Figure 1is a block diagram of an exemplary machine vision inspection system 10 that may be used as or include a VFL(TAG) lens system (also referred to herein as an imaging system) in accordance with the present disclosure. The machine vision inspection system 10 includes a vision measurement machine 12 operably connected to exchange data and control signals with a control computer system 14. The control computer system 14 is further operably connected to exchange data and control signals with a monitor or display 16, a printer 18, a joystick 22, a keyboard 24, and a mouse 26. The monitor or display 16 may display a user interface suitable for controlling and / or programming the operation of the machine vision inspection system 10. It should be appreciated that in various embodiments, a touch screen tablet or the like may replace and / or redundantly provide the functionality of any or all of the elements 14, 16, 22, 24, and 26. Various embodiments of the machine vision inspection system 10 are also described in commonly assigned US Pat. Nos. 7,454,053, 7,324,682, 8,111,905, and 8,111,938, each of which is hereby incorporated by reference in its entirety.

[0077] Those skilled in the art will appreciate that any suitable computing system or device, including a distributed or networked computing environment, etc., can generally be used to implement the control computer system 14. Such computing systems or devices may include one or more general or special-purpose processors (e.g., non-customized or customized devices) that execute software to perform the functions described herein. The software may be stored in a memory such as a random access memory (RAM), a read-only memory (ROM), a flash memory, etc., or a combination of such components. The software may also be stored in one or more storage devices such as an optical-based disk, a flash memory device, or any other type of non-volatile storage medium for storing data. The software may include one or more program modules, which include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In a distributed computing environment, the functionality of the program modules may be combined or distributed across multiple computing systems or devices, and the functionality of the program modules may be accessed via service calls in a wired or wireless configuration.

[0078] The vision measuring machine 12 includes a movable workpiece stage 32 and an optical imaging system 34, which may include a zoom lens or an interchangeable objective lens. The zoom lens or interchangeable objective lens typically provides various magnifications for the image provided by the optical imaging system 34. Figure 2A and 2B Described in more detail, the optical imaging system 34 may include an optical assembly portion 205 (eg, which may include a zoom lens and / or an interchangeable objective lens) and in some embodiments may be coupled to a rotational stage 297 .

[0079] Figure 2Ais a method that includes certain features disclosed herein and Figure 1 1 is a block diagram of a control system portion 120 and a vision component portion 200 of a machine vision inspection system similar to the machine vision inspection system 100. As will be described in more detail below, the control system portion 120 is used to control the vision component portion 200. The vision component portion 200 includes an optical component portion 205, light sources 220, 230, 240 (which can be part of the optical component portion 205, or provided separately from the optical component portion), and a workpiece table 210 having a central transparent portion 212. The workpiece table 210 (corresponding to Figure 1 The workpiece stage 32 in the embodiment of the present invention is controllably movable along an X-axis and a Y-axis, which lie in a plane generally parallel to the surface of the stage where the workpiece 20 is positioned. The optical assembly portion 205, which may include at least a portion of the light sources 220, 230, 240, also includes a camera system 260, an interchangeable objective lens 250, and a variable focus length (VFL) lens 270.

[0080] One known VFL lens is a tunable acoustic gradient ("TAG") lens, which uses acoustic waves in a fluid medium to produce a lens effect. Acoustic waves can be generated by applying an electric field at a resonant frequency to a piezoelectric tube surrounding the fluid medium to produce a time-varying density and refractive index distribution in the lens fluid, which adjusts its optical power and thereby adjusts the focal length (or effective focus position) of the optical system. TAG lenses can be used to periodically scan a range of focal lengths at high speed (i.e., periodically modulate its optical power), for example, at a resonant frequency of greater than 30 kHz, or greater than 70 kHz, or greater than 100 kHz, or greater than 400 kHz, up to 1.0 MHz. Such lenses can be understood in more detail through the teachings of the article "High speed varifocal imaging with a tunable acoustic gradient index of refraction lens" (Optics Letters, Vol. 33, No. 18, September 15, 2008), which is incorporated herein by reference in its entirety. TAG lenses and associated controllable signal generators can be obtained, for example, from Mitutoyo Corporation of Kanagawa, Japan. As a specific example, the SR38 series TAG lens is capable of periodic modulation with a modulation frequency of up to 1.0 MHz. Various aspects of the operating principles and applications of the TAG lens are described in more detail in U.S. Patent Nos. 9,930,243; 9,736,355; 9,726,876; 9,143,674; 8,194,307; and 7,627,162; and in U.S. Patent Application Publication Nos. 2017 / 0078549 and 2018 / 0143419, each of which is incorporated herein by reference in its entirety. According to various embodiments, the TAG lens with its fast zoom imaging capability is particularly suitable for use as a VFL lens 270 to perform fast autofocus. As an alternative to the TAG lens, a mechanical VFL lens can also be used as the VFL lens 270, where the multi-lens system is mechanically moved to change its focal length.

[0081] In various embodiments, the optical assembly portion 205 may also include a turret lens assembly 223 having lenses 226 and 228. As an alternative to the turret lens assembly, in various embodiments, a fixed or manually interchangeable magnification changing lens or zoom lens configuration, etc. may be included. In various embodiments, the interchangeable objective lens 250 may be selected from a collection of fixed magnification objective lenses included as part of the variable magnification lens portion (e.g., a collection of objective lenses corresponding to magnifications such as 0.5x, 1x, 2x or 2.5x, 5x, 7.5x, 10x, 20x or 25x, 50x, 100x, etc.).

[0082] The optical assembly portion 205 can be driven along the Z direction by using a driving actuator. M The controllable motor 294 of the axis moves the optical assembly portion 205 along the X-axis and Y-axis (i.e., X M and Y M axis) is substantially orthogonal to the Z axis of the MCS (i.e., Z M The controllable motor 294 is connected to the input / output interface 130 via a signal line 296. As will be described in more detail below, the VFL (TAG) lens 270 can be controlled by the lens control interface 134 via a signal line 234' to periodically modulate the optical power of the VFL lens 270 and thereby modulate the effective focus position (or focal length) of the optical assembly portion 205 (e.g., in some embodiments / orientations, it can be used to change the focus of the image within a relatively small range, or as an alternative to moving the optical assembly portion 205 to change the focus of the workpiece image). The lens control interface 134 can include a VFL lens controller 180, as described in more detail below. The workpiece stage 210 on which the workpiece 20 is placed can be controlled to move relative to the optical assembly portion 205 (e.g., in the X and Y directions and / or as part of a rotatable stage in the Z direction, etc.) so that the field of view of the interchangeable objective lens 250 moves (e.g., between surfaces and / or surface locations on the workpiece 20 and / or between multiple workpieces 20, etc.).

[0083] One or more of the stage light source 220, the coaxial light source 230, and the surface light source 240 (e.g., a ring light) may emit source light 222, 232, and / or 242, respectively, to illuminate one workpiece 20 or multiple workpieces 20. In various exemplary embodiments, gated illumination may be used. For example, during image exposure, the coaxial light source 230 may emit gated source light 232 along a path including a beam splitter 290 (e.g., a partial reflector). The source light 232 is reflected or transmitted as image light 255, and the image light for imaging passes through the interchangeable objective lens 250, the turret lens assembly 223, and the VFL (TAG) lens 270 and is collected by the camera system 260. The workpiece image exposure including the image of the workpiece 20 is captured by the camera system 260 and output to the control system portion 120 on the signal line 262.

[0084] Various light sources (e.g., light sources 220, 230, 240) can be connected to the lighting control interface 133 of the control system portion 120 via related signal lines (e.g., buses 221, 231, 241, respectively). The control system portion 120 can control the turret lens assembly 223 to rotate along the axis 224 via a signal line or bus 223' to select the turret lens to change the image magnification.

[0085] As described above, in various embodiments, the relative position, distance, etc. of the optical assembly portion 205 (e.g., the objective lens 250 of the optical assembly portion 205) relative to the workpiece surface WPS1 and / or WPS2 of the workpiece 20 to be measured can be adjusted along the Z axis of the MCS (e.g., using the controllable motor 294) and along the X axis and Y axis of the MCS (e.g., by moving the workpiece stage 210). In various embodiments, the controllable motor 294 and the movable workpiece stage 210 can be collectively part of an adjustment mechanism configured to at least change the distance, position, and / or orientation between the optical assembly portion 205 and the workpiece surface WPS1 and / or WPS2.

[0086] According to various embodiments of the present disclosure, the adjustment mechanism may further include a rotation mechanism 295 configured to rotate the optical assembly portion 205 relative to the workpiece surface WPS1 of the workpiece 20 to change the orientation (e.g., angular orientation) of the optical axis OA of the optical assembly portion 205 relative to the workpiece surface WPS1. In various implementations, the rotation of the optical assembly portion 205 to change the orientation of the optical axis OA relative to the workpiece surface WPS1 may correspond at least in part to a roll and / or pitch rotation.

[0087] like Figure 2A As shown, the optical assembly portion 205 has a local coordinate system (LCS) including the X, Y, and Z axes of the LCS (i.e., X L , Y L and Z L Axis), which can move and rotate with the optical component part 205, and its optical axis OA is parallel to the Z axis. L Axis alignment (e.g., defining Z L axis). Figure 2A In the orientation shown, the LCS is roughly aligned with the MCS (i.e., the optical axis OA is aligned with the Z direction of the MCS). M In some existing systems, the orientation of the optical axis OA of the optical component part is relatively fixed so as to always be aligned with the Z axis of the MCS. M Axis Alignment. Relative to the LCS, yaw, pitch, and roll rotations can correspond to rotations about their respective axes. In the configuration shown, the rotation about X L The rotation about the Y axis (eg, referred to as the first rotation axis) may be referred to as rolling. L The rotation about the Z axis (eg, referred to as the second rotation axis) may be referred to as pitch, and the rotation about the Z axis may be referred to as L The rotation of the axis may be referred to as yaw.

[0088] In some embodiments, the rotation mechanism 295 can provide a rotation of the optical assembly portion 205 that corresponds to a rotation about at least one of a first rotation axis (e.g., roll) and / or a second rotation axis (e.g., pitch). As used herein, the first rotation axis "and / or" the second rotation axis thus means the first rotation axis alone, the second rotation axis alone, or both the first rotation axis and the second rotation axis. Although the first rotation axis and the second rotation axis can be, for example, orthogonal to each other, the first rotation axis and the second rotation axis can be orthogonal to each other. L Axis and Y L axes, but they do not have to be orthogonal to each other or to the Z axis. L The first rotation axis and the second rotation axis only need to be orthogonal to each other and to the Z axis. L The axes are not parallel (including not co-linear). Generally speaking, in various embodiments, the rotation mechanism 295 can provide "with Z L "out-of-plane" rotational motion (e.g., including at least one of roll or pitch, or a combination thereof).

[0089] As will be described in more detail below, Figure 2B A configuration is shown in which a rotation mechanism 295 has been used to rotate the optical assembly portion 205 relative to the workpiece surface WPS1 to change the angular orientation of the optical axis OA of the optical assembly portion 205 so as to orient the optical axis OA to be nominally perpendicular (i.e., approximately perpendicular) to the workpiece surface WPS1. In addition, a motor 294 has been used to adjust the distance between the optical assembly portion 205 and the workpiece surface WPS1 (e.g., so that the relative position of the workpiece surface is nominally at a desired Z relative to the optical assembly portion 205). L As used herein, the term "nominal" includes variations in one or more parameters that fall within acceptable tolerances. As an example, in one embodiment, an element (e.g., the optical axis OA) can be defined as nominally normal to (i.e., nominally perpendicular to) a workpiece surface (e.g., which can be defined based on a calculated surface plane) if it is normal to (i.e., perpendicular to) the workpiece surface or within 5 degrees of perpendicular to the workpiece surface (e.g., having an angular orientation between 85 degrees and 95 degrees relative to the workpiece surface). As another ... all areas of the workpiece surface within the field of view (FOV) of the optical component portion are at an average or otherwise specified or optimal Z relative to the optical component portion 205. LIf the optical axis OA of the optical component portion is within four depths of field (DOF) of the (i.e., focus) position, then the optical axis OA of the optical component portion can be defined as nominally normal to (i.e., approximately perpendicular to) the workpiece surface (e.g., as can be defined based on a calculated surface plane and for which the workpiece surface can be relatively flat in some cases and located at or near the best focus position of the optical component portion). In one embodiment, this can correspond to at least a portion of the workpiece surface being in the best focus position and all other portions of the workpiece surface in the FOV being within 4 DOF of the best focus position (i.e., for which the optical axis OA of the optical component portion is correspondingly nominally perpendicular to the workpiece surface). As another example, if all portions of the workpiece surface in the FOV are within 4 DOF of the best focus position, then the workpiece surface can be defined as nominally in the best focus position. In other instances, the system and / or definition can be more precise (e.g., such as within 2 DOF, within 2 degrees, within 2%, etc.).

[0090] Relative to Figure 2A orientation, leading to Figure 2B The rotation of the orientation corresponds to the rotation around X L In other configurations, such rotation (e.g., to nominally align the optical axis OA with the surface normal of the workpiece surface) may also or instead include rotation about the Y axis (e.g., the first rotation axis). L A pitch rotation about an axis (e.g., a second rotation axis). Figure 2B As shown, according to the rotation of the optical component part 205, the LCS also rotates accordingly (for example, relative to the MCS), so that the optical axis OA and Z L Axis alignment (e.g., defining Z L axis).

[0091] Various embodiments of the rotating mechanism 295 are possible. Figure 1 and Figure 2A As shown, the rotating mechanism 295 can be provided as part of a rotating table 297 of the vision measuring machine 12, to which the optical assembly part 205 is attached. Therefore, in various embodiments, the optical assembly part 205 can be controllably rotated by driving an actuator (e.g., as part of the rotating mechanism 295) to move (e.g., rotate) the rotating table 297. The rotating table 297 (e.g., including the rotating mechanism 295) is connected to the input / output interface 130 via a signal line 298.

[0092] Alternatively or additionally, the movable workpiece table 210 can be configured to embody a rotary table (e.g., including a rotation mechanism, not shown), which can be configured and controlled similarly to the above-described rotary table 297. As with the above-described rotary table 297, the movement (e.g., rotation) of the workpiece table 210, which is additionally configured as a rotary table, can be controlled by the control system portion 120 via a signal line (e.g., similar to the signal line 298) to achieve a desired rotation (e.g., rotation of the angular orientation of the workpiece 20 located on the workpiece table 210).

[0093] like Figure 2A As shown, in various exemplary embodiments, the control system portion 120 includes a controller 125, an input / output interface 130, a memory 140, a workpiece program generator and actuator 170, and a power supply portion 190. Each of these components, as well as the additional components described below, can be interconnected via one or more data / control buses and / or application programming interfaces or by direct connections between the various components. The input / output interface 130 includes an imaging control interface 131, a motion control interface 132, an illumination control interface 133, and a lens control interface 134. The lens control interface 134 includes or is connected to a VFL lens controller 180, which includes circuits and / or routines for controlling the operation of the VFL (TAG) lens 270 (e.g., as described below with respect to Figure 4 ). The illumination control interface 133 includes illumination control elements 133a-133n that control, for example, the selection, power, on / off switching, and strobe timing (if applicable) of various corresponding light sources for the machine vision inspection system 100.

[0094] The motion control interface 132 is configured to send control signals via signal lines 296 and 298 to move the optical assembly portion 205. In various embodiments, the motion control interface 132 may include a surface normal motion control portion 132sn that may be used to implement a particular process to adjust and / or change the orientation of the optical axis OA of the optical assembly portion 205 so as to be nominally perpendicular to the workpiece surface (e.g., workpiece surface WPS1 and / or WPS2). Control signals may also be sent (e.g., from the motion control interface 132 or the surface normal motion control portion 132sn) to adjust and / or change the distance between the optical assembly portion 205 and the workpiece surface WPS1 and / or WPS2 (e.g., so as to nominally position the optical assembly portion 205 at a desired focus position relative to the workpiece surface, which may depend on the process to be performed on the workpiece surface, such as for a PFF operation, or to obtain an extended depth of field (EDOF) image, or a machining operation, etc.).

[0095] The memory 140 may include an image file memory portion 141, an edge detection memory portion 140ed, a workpiece program memory portion 142 which may include one or more part programs, etc., and a video tool portion 143. The video tool portion 143 includes various tools 143a-143n, in particular an autofocus video tool 143af, which determines a GUI, image processing operations, etc. for each corresponding video tool. The video tool portion 143 also includes a region of interest (ROI) generator 143roi, which supports automatic, semi-automatic and / or manual operations that define various ROIs that can be operated in various video tools included in the video tool portion 143, such as the autofocus video tool 143af.

[0096] The auto focus video tool 143af uses the VFL lens 270 controlled via the input / output interface 130 to determine the focal height (ie, effective focus position (Z)) for the image. L -height)) measurement operations, image processing operations, and the like. In various embodiments, the autofocus video tool 143af may additionally include a high-speed focus height tool that can be used to measure focus height at high speed, as described in more detail in U.S. Patent No. 9,143,674, which is incorporated herein above. High-speed automatic focus and / or focus position determination for one or more image regions of interest can be based on analyzing the image according to known methods to determine corresponding focus feature values ​​(e.g., quantitative contrast metric values ​​and / or quantitative focus metric values) for each region. For example, such methods are disclosed in U.S. Patent Nos. 8,111,905, 7,570,795, and 7,030,351, each of which is hereby incorporated herein by reference in its entirety.

[0097] In various embodiments, the auto-focus video tool 143af may include and / or be associated with a surface normal determination portion 143sn that may be used to implement a specific process (e.g., including or in conjunction with a multi-point auto-focus process) for determining a surface normal of a workpiece surface. In certain embodiments, the surface normal determination portion 143sn may be implemented as a separate process or mode relative to the auto-focus video tool 143af, and may independently or otherwise initiate a multi-point auto-focus process and / or subsequent processing for determining a surface normal (e.g., and for determining a corresponding desired focus position in some embodiments) according to the methods disclosed herein, as will be described in more detail below.

[0098] According to various embodiments, the controller 125 cooperates with the VFL lens controller 180 and the surface normal determination part 143sn to capture an image stack including a plurality of images at different focal lengths of the workpiece surface WPS1, and calculate the auto focus height (e.g., Z ) of at least three locations of the workpiece surface WPS1 based on at least three corresponding regions of interest (ROI) of the image stack. L - height). In various embodiments, for the purpose of calculating at least three auto-focus heights, it may not be necessary to change the relative orientation between the optical assembly portion 205 and the workpiece surface WPS1, as will be described below with reference to Fig. 6A and Figure 6B More fully described. In various embodiments, at least three auto-focus heights may be calculated / determined to define / determine a surface (e.g., based on a defined / determined plane or other representation, which may include three auto-focus heights and / or a calculated average or other determination thereof), thereby calculating a surface normal to the calculated / defined surface. Those skilled in the art will appreciate that, depending on the increasing number of auto-focus heights calculated, such as tens (10, 20, 50, etc.) or hundreds of auto-focus heights, more than three auto-focus heights may be calculated to more accurately define a surface, as long as the additional computational burden and processing time are acceptable in a particular application.

[0099] In various embodiments, a calculated surface normal and / or other data based at least in part on at least three autofocus heights (e.g., related to a defined / determined surface) can be utilized (e.g., by a surface normal determination portion 143sn, a controller 125, and / or a surface normal motion control portion 132sn, etc.) to calculate adjustment information. Based on the calculated adjustment information, the surface normal motion control portion 132sn and / or the motion control interface 132 can control an adjustment mechanism (e.g., a controllable motor 294 and a rotation mechanism 295) to move / rotate the optical component portion 205 so that the optical axis OA of the optical component portion 205 is nominally aligned with the surface normal SN of the workpiece surface WPS1, and adjust the distance between the optical component portion 205 and the workpiece surface WPS1. For example, Figure 2B An adjustment mechanism for (re)orienting the optical component part 205 is shown so that the optical axis OA of the optical component part 205 nominally coincides with the calculated surface normal SN of the workpiece surface WPS1. As will be described in more detail below, Figure 2B In the example of FIG. 204 , the adjustment mechanism is also controlled to adjust the distance between the optical component portion 205 and the workpiece surface WPS1 (eg, so that the workpiece surface WPS1 is nominally at a desired Z relative to the optical component portion 205). L(i.e., focal) position). In various embodiments, the surface normal determination portion 143sn and the surface normal motion control portion 132sn, and / or various processes associated therewith, may be implemented as separate portions / components, and / or may be merged and / or otherwise indistinguishable.

[0100] The controller 125 or other component may then perform defined operations on the workpiece surface WPS1, which is now nominally perpendicular to the optical axis OA and at the desired Z L When performing certain imaging operations, as described above, it may be necessary to adjust the distance between the optical component portion and the workpiece surface (i.e., adjusted by the adjustment mechanism and corresponding to Z L Position) to nominally correspond to an authoritative focus position, which can be a best focus position where the workpiece surface is nominally in focus, or alternatively corresponds to a different focus position when performing a machining operation (e.g., a point self-focus position for certain types of EDOF operations, etc.), and in various embodiments the machining operation axis can be assumed to be coincident with and / or otherwise parallel to the optical axis OA of the optical component portion 205, so that the machining operation (e.g., a drilling operation, etc.) is performed along an axis that is nominally perpendicular to the calculated surface of the workpiece.

[0101] Generally, in various embodiments, the controller 125 and the memory 140 include necessary circuits and / or routines to implement the method of the present disclosure, as will be described more fully below, which includes: positioning the optical component portion 205 relative to the workpiece surface WPS1; capturing an image stack of the workpiece surface at multiple focal lengths; determining auto-focus heights of at least three locations of the workpiece surface based on at least three corresponding ROIs of the image stack (e.g., its surface normal and corresponding adjustment information can be determined based on the auto-focus heights); controlling the adjustment mechanism to: rotate the optical component portion 205 relative to the workpiece surface WPS1 to nominally align the optical axis of the optical component portion 205 with the (e.g., calculated) surface normal SN of the workpiece surface WPS1; and adjusting the distance between the optical component portion and the workpiece surface WPS1 (e.g., so that the workpiece surface WPS1 is nominally located at a desired / specified / determined Z L position); and perform a defined operation on the workpiece surface WPS1.

[0102] One or more display devices 136 (e.g., Figure 1 16) and one or more input devices 138 (e.g., Figure 1A joystick 22, keyboard 24, and mouse 26 (such as a joystick 22, keyboard 24, and mouse 26) are connected to the input / output interface 130. The display device 136 and the input device 138 can be used to display a user interface, which can include various GUI features that can be used to perform inspection operations, and / or create and / or modify part programs, view images captured by the camera system 260, and / or directly control the vision component part 200.

[0103] In various exemplary embodiments, when a user utilizes the machine vision inspection system 100 to create a part program for a workpiece 20, the user generates part program instructions by operating the machine vision inspection system 100 in a learning mode to provide a desired image acquisition training sequence. For example, the training sequence may include locating a specific workpiece feature of a representative workpiece in the field of view (FOV), setting light levels, focusing or autofocus, acquiring an image, and providing an inspection training sequence applied to the image (e.g., using an instance of one of the video tools for that workpiece feature). Such operations may include processes such as those described herein, including utilizing multi-point autofocus to align the optical axis of the optical component portion to be nominally perpendicular to the workpiece surface and adjust the distance between the optical component portion and the workpiece surface, and perform subsequent operations on the workpiece surface (e.g., imaging, measuring, etc.). The learning mode operates so that the sequence is captured or recorded and converted into corresponding part program instructions. When the part program is executed, these instructions will cause the machine vision inspection system to reproduce the trained image acquisition and cause the inspection operation to automatically inspect that the specific workpiece feature (i.e., the corresponding feature in the corresponding position) is located on one or more operating mode workpieces that match the representative workpiece used when creating the part program.

[0104] Figure 3A is a schematic diagram of a VFL (TAG) lens system 300, which includes an optical component portion 305, which includes corresponding Figure 2A The TAG lens system 300 and / or the optical component portion 305 may be adapted to Figure 1 and 2A and a machine vision system of the type shown in 2B, or may be applicable to Figure 7 Robotic systems or Figures 8A-8E The coordinate measuring machine (CMM) system is as follows. It should be understood that Figure 3A Certain numbered components 3XX may correspond to and / or provide Figure 2A Similar numbered components 1XX or 2XX have similar operations or functions and may be understood similarly unless otherwise noted.

[0105] The imaging optical path OPATH (also referred to herein as the workpiece imaging optical path) includes various optical components arranged along a path that transmits image light 355 from the workpiece 320 to the camera 360. The image light is generally transmitted along the direction of their optical axes. Figure 3A In the illustrated embodiment, all optical axes are aligned. However, it should be understood that this embodiment is exemplary and not limiting. More generally, the imaging optical path OPATH may include mirrors and / or other optical elements and may take any form that performs imaging operations on the workpiece 320 using a camera (e.g., camera 360) according to known principles. In the illustrated embodiment, the imaging optical path OPATH includes a TAG lens 370 (which may be included in a 4f imaging configuration) and is used at least in part to image the surface of the workpiece 320 during workpiece image exposure.

[0106] like Figure 3A As shown, the TAG lens system 300 includes an optical assembly portion 305, which includes a light source 330, an objective lens 350, a tube lens 351, a relay lens 352, a VFL (TAG) lens 370, a relay lens 356, and a camera 360. The TAG lens system 300 may also include an exposure (strobe) time controller 333es, a VFL (TAG) lens controller 380, a motion controller 332 (e.g., including a surface normal motion controller 332sn), and a surface normal determination portion 343sn. In various embodiments, the motion controller 332, the surface normal motion controller 332sn, and / or the surface normal determination portion 343sn may operate substantially similarly to the controllers / portions 132, 132sn, and 143sn, respectively, as described above with respect to Figure 2A and 2B In various embodiments, the various components may be interconnected via direct connections or one or more data / control buses (eg, system signal and control bus 395) and / or application programming interfaces.

[0107] As will be described in more detail below (e.g., including with respect to Figure 4 ), in various embodiments, the VFL lens controller 380 can control the driving signal of the TAG lens 370 to periodically modulate the optical power of the TAG lens 370 within the optical power range that appears at each phase timing within the periodic modulation. The objective lens 350 inputs image light from the workpiece 320 during image exposure, and transmits the image light along the imaging optical path OPATH through the TAG lens 370 to the camera 360 during image exposure to provide a workpiece image in a corresponding camera image. The effective focus position EFP in front of the objective lens 350 during image exposure corresponds to the optical power of the TAG lens 370 during the image exposure. The exposure time controller 333es is configured to control the image exposure timing for the camera image.

[0108] about Figure 3A , light source 330 can be a "coaxial" or other light source configured to emit source light 332 along a path that includes a beam splitter 390 (e.g., a partially reflective mirror as part of the beam splitter) and through an objective lens 350 to the surface of a workpiece 320. Objective lens 350 receives image light 355 (e.g., workpiece light) focused at an effective focus position EFP near workpiece 320 and outputs image light 355 to tube lens 351. Tube lens 351 receives image light 355 and outputs it to relay lens 352. In other embodiments, similar light sources can illuminate the field of view in a non-coaxial manner; for example, a ring light source can illuminate the field of view.

[0109] In various embodiments, objective lens 350 may be an interchangeable objective lens, and tube lens 351 may be included as part of a turret lens assembly (e.g., similar to Figure 2A Interchangeable objective lens 250 and turret lens assembly 223). Figure 3A In the illustrated embodiment, image light 355 from the nominal focal plane of the objective lens 350 is focused by the tube lens 351 to form an intermediate image at the nominal intermediate image plane IIPnom. When the TAG lens 370 is in a state where no lens effect (no optical power) is provided, the nominal focal plane of the objective lens 350, the nominal intermediate image plane IIPnom, and the image plane of the camera 360 form a set of conjugate planes according to known microscope imaging principles. In various embodiments, any other lens mentioned herein may be formed by a single lens, a compound lens, etc. or operate in combination therewith.

[0110] Relay lens 352 receives image light 355 from tube lens 351 (or more generally, in various alternative microscope configurations, from an intermediate image plane) and outputs it to TAG lens 370. TAG lens 370 receives image light 355 and outputs it to relay lens 356. Relay lens 356 receives image light 355 and outputs it to camera 360. In various embodiments, camera 360 captures camera images during image exposure (e.g., during an integration period of camera 360) and can provide corresponding image data to the control system portion. Some camera images can include workpiece images (e.g., images of a region of workpiece 320) provided during workpiece image exposure. In some embodiments, image exposure (e.g., workpiece image exposure) can be limited or controlled by flash timing of light source 330 that falls within the image integration period of camera 360. In various embodiments, camera 360 can have a pixel array greater than 1 megapixel (e.g., 1.3 megapixels with a 1280x1024 pixel array, 5.3 microns per pixel).

[0111] exist Figure 3AIn the example of , relay lenses 352 and 356 and VFL (TAG) lens 370 are designated as included in a 4f optical configuration, while relay lens 352 and tube lens 351 are designated as included in a Keplerian telescope configuration, and tube lens 351 and objective lens 350 are designated as included in a microscope configuration. All illustrated configurations are to be understood as being exemplary only and not limiting of the present disclosure. In various embodiments, the illustrated 4f optical configuration allows the VFL (TAG) lens 370 (e.g., which may be a low numerical aperture (NA) device) to be placed at the Fourier plane of objective lens 350. This configuration can maintain telecentricity at workpiece 320 and can minimize scale variations and image distortion (e.g., including providing a fixed focal length for each effective focus position (Z) of workpiece 320). L -height) provides constant magnification).

[0112] In various embodiments, the lens controller 380 may include a drive signal generator portion 381, a timing clock 381', and an imaging circuit / routine 382. The drive signal generator portion 381 may operate (e.g., in conjunction with the timing clock 381') to provide a periodic drive signal to the high-speed VFL (TAG) lens 370 via a signal line 380'. In various embodiments, the TAG lens system 300 (or the optical assembly portion 205') may include a control system (e.g., the control system portion 120 of FIG. 2) that may be configured to operate with the lens controller 380 for coordinated operation.

[0113] In various embodiments, the lens controller 380 may generally perform various functions related to imaging the workpiece 320 in a manner synchronized with the desired phase timing of the TAG lens 370 and controlling, monitoring, and adjusting the actuation and response of the TAG lens 370. In various embodiments, the image circuit / routine 382 performs standard imaging operations of the optical system in synchronization with the phase timing of the TAG lens 370.

[0114] In various situations, the operating characteristics of a VFL lens may drift due to undesirable temperature changes. Figure 3A As shown, in various embodiments, the TAG lens system 300 may optionally include a lens heater / cooler 337 associated with the TAG lens 370. According to some embodiments and / or operating conditions, the lens heater / cooler 337 may be configured to input a certain amount of thermal energy to the TAG lens 370 and / or perform a cooling function to facilitate heating and / or cooling of the TAG lens 370. In addition, in various embodiments, a TAG lens monitoring signal may be provided by a temperature sensor 336 associated with the TAG lens 370 to monitor the operating temperature of the TAG lens 370.

[0115] Regarding the general operation of the TAG lens 370, in various embodiments as described above, the lens controller 380 can periodically and rapidly adjust or modulate its optical power to achieve a high-speed VFL lens that periodically modulates its optical power at high speed at a TAG lens resonant frequency of 400 kHz, 250 kHz, 70 kHz, or 30 kHz, etc. Figure 3A As shown, by driving the TAG lens 370 with periodic modulation of the signal, the effective focus position EFP of the TAG lens system 300 (i.e., the focus position in front of the objective lens 350) can be quickly moved within a range Refp (e.g., a focus range or an autofocus search range, etc.), which is defined by an effective focus position EFP1 (or EFPmax or a peak focal length Z1max+) corresponding to the maximum optical power of the TAG lens 370 combined with the objective lens 350 and an effective focus position EFP2 (or EFPmin or a peak focal length Z1max-) corresponding to the maximum negative optical power of the TAG lens 370 combined with the objective lens 350. In various embodiments, the effective focus positions EFP1 and EFP2 can approximately correspond to phase timings of 90 degrees and 270 degrees, as will be described below with reference to Figure 4 For discussion purposes, the middle of the range Refp may be designated as EFPnom and may correspond approximately to the zero optical power of the TAG lens 370 combined with the nominal optical power of the objective lens 350. According to this description, in some embodiments, EFPnom may correspond approximately to the nominal focal length of the objective lens 350 (e.g., it may correspond to the working distance WD of the objective lens 350).

[0116] and Figure 2A Like the precision machine vision inspection system, Figure 3A The TAG lens system 300 is also associated with or includes an adjustment mechanism that is configured to change the distance between the optical assembly portion 305 and the workpiece surface WPS1 of the workpiece 320 (e.g., using a method similar to Figure 2A The optical assembly portion 305 is rotated relative to the workpiece surface WPS1 of the workpiece 320 (e.g., using the rotating mechanism 295). Figure 3A In the example shown, the adjustment mechanism includes a rotation mechanism 295 configured to rotate the optical component portion 305 (including the optical axis OA of the optical component portion 305) relative to the workpiece surface WPS1. Figure 3A As shown, the rotating mechanism 295 can be provided as part of a rotating table 297 to which the optical assembly portion 305 is attached. Alternatively, the table on which the workpiece 320 is placed can be configured as a rotating table.

[0117] exist Figure 3AIn the example of , the adjustment mechanism has been controlled to move the optical component part 305 to position the workpiece surface WPS1 within the focal point Z autofocus range of the optical component part 305. Figure 3A In the illustration of , this may correspond to positioning the optical assembly portion 305 at a distance D-3A from a position on the workpiece surface WPS1. For example, the distance D-3A may nominally correspond to the working distance WD, which may correspond to the midpoint or other portion of the focal Z autofocus range (e.g., may correspond to a portion or all of the range REFP). Figure 3A As shown, at distance D-3A, all portions of workpiece surface WPS1 are within range REFP, and for these portions, an autofocus process including capturing an image stack can be used to determine autofocus heights at different locations (e.g., at least three locations on workpiece surface WPS1). It should also be understood that workpiece 320 and / or optical component portion 305 have been positioned so that workpiece surface WPS1 is within the field of view of optical component portion 305. As will be described in more detail below, at Figure 3B In the example of , the workpiece 320 can be similarly positioned so that the workpiece surface WPS1 is within the field of view of the optical component portion 305, and the optical axis OA thereof can be directed to a similar or identical position on the workpiece surface WPS1, such as Figure 3A As shown (for example, a workpiece table or other motion mechanism can be used to move along the X direction of the machine coordinate system M and Y M axial direction positioning workpiece 320, etc.).

[0118] and Figure 2A Like a precision machine vision inspection system, the method of the present disclosure can be implemented, including: positioning the optical component part 305 relative to the workpiece surface 320A (for example, controlled by the motion controller 332 and / or 332sn); capturing an image stack of the workpiece surface at multiple focal lengths (for example, by controlling the VFL (e.g., TAG) lens 370, such as controlled by the lens controller 380 and / or the exposure time controller 333es, and / or by moving the optical component part 305, such as controlled by the motion controller 332 and / or 332sn); determining the auto focus heights of at least three positions of the workpiece surface WPS1 based on at least three corresponding ROIs of the image stack (for example, its surface normal and corresponding adjustment information can be determined based on the calculated auto focus heights); controlling the adjustment mechanism to: rotate the optical component part 305 relative to the workpiece surface WPS1 so that the optical axis OA of the optical component part 305 is nominally aligned with the calculated surface normal SN of the workpiece surface WPS1; adjust the distance between the optical component part and the workpiece surface; and perform a defined operation on the workpiece surface WPS1.

[0119] For example, Figure 3BAs shown, when the workpiece surface WPS1 of the workpiece 320 is tilted as shown or otherwise oriented at an angle relative to the horizontal plane, the adjustment mechanism including the rotation mechanism 295 can be used to (re)orient the optical component part 305 so that the optical axis OA of the optical component part 305 is nominally aligned with the determined (e.g., calculated) surface normal SN of the workpiece surface WPS1. In addition, the adjustment mechanism (e.g., including the motor 294 or other corresponding mechanism) can be used to adjust the distance between the optical component part 305 and the workpiece surface WPS1. Figure 3B As shown in , the distance has been adjusted so that the distance D-3B between the optical component portion 305 and the workpiece surface WPS1 nominally corresponds to the working distance WD (e.g., it can be close to or in the middle of the range REFP and / or can correspond to the best focus position, etc.). Specifically, in embodiments that do not include a VFL lens, or in embodiments that include a VFL lens but are not operated, the working distance WD of the objective lens 350 can correspond to the best focus position (i.e., the position where the workpiece surface WPS1 will be in focus). In embodiments that include and operate a VLF lens 370, in some cases, the working distance WD can be specified to correspond to a general "focus position" of the optical component portion and / or can be specified to correspond to a "best focus position" (e.g., close to or in the middle of the range REFP of operation of the VFL lens 370, and the phase timing corresponding to the zero optical power of the VFL lens 370 can correspond to the workpiece surface WPS1 being nominally in focus).

[0120] It should be understood that according to the principles of trigonometry, as the optical component portion 305 is rotated by the rotating mechanism 295 from Figure 3A The orientation is rotated to Figure 3B The distance between the optical component portion 305 and the workpiece surface WPS1 will generally change during the rotation. Figure 3B The distance D-3B may be Figure 3A When the distance D-3A is substantially the same, the adjustment mechanism will still adjust the distance between the optical component part 305 and the workpiece surface WPS1 according to the rotation, as a way to achieve Figure 3B It should also be understood that in various embodiments, distance D-3B may generally be different from distance D-3A. More specifically, according to Figure 3A The surface position of the workpiece surface WPS1 that intersects the optical axis OA (i.e., and correspondingly at the distance D-3A) will be within the focus Z autofocus range, but may not be within the desired Z relative to the optical assembly portion 305. L position (e.g., at a desired focus position or other position, which may correspond to distance D-3B, for example). Figure 3AOne or more other surface locations of the workpiece surface WPS1 may be at a desired Z L position, or none of the other surface positions is at the desired Z L position (e.g., corresponding to distance D-3B). According to the method described herein, Figure 3A In an example of the present invention, the autofocus process is used to determine autofocus heights (e.g., which thus define and indicate the position of the workpiece surface WPS1) at different positions (e.g., at least three positions) of the workpiece surface WPS1. Based at least in part on the determined autofocus heights, the adjustment mechanism rotates and adjusts the distance of the optical component portion relative to the workpiece surface to be at a position such as Figure 3B The direction and distance D-3B shown (eg, corresponding to the desired Z L location, for which Figure 3A One or more positions or no position on the workpiece surface WPS1 Figure 3B The adjustment may have been at distance D-3B or the corresponding desired Z L Location).

[0121] Figure 4 Yes Description Figure 3A and 3B The timing diagram of the phase timing of the periodic modulation control signal PMCS and the optical response RSP of the VFL lens system. Figure 4 In the example of FIG. 1 , an ideal case is illustrated in which the control signal PMCS and the light response RSP have similar phase timing and are therefore represented as the same signal, although it will be understood that in some cases the signals may be separated by a phase offset, as described in U.S. Patent No. 9,736,355, which is commonly assigned and incorporated herein by reference in its entirety. In various embodiments, the control signal PMCS may be coupled to the light response RSP. Figure 3A The optical response RSP is related to the drive signal (e.g., including the amplitude drive signal) generated by the drive signal generator 381, and the optical response RSP can represent the periodically modulated focus position of the optical component portion controlled by periodically modulating the optical focal length of the TAG lens 370 as described above.

[0122] In various embodiments, the sinusoidal shape of the curves PMCS and RSP may depend on the lenses in series (e.g., Figure 3A and 3B The objective lens 350, TAG lens 370, etc. shown in the figure are used to determine the focal length of the TAG lens 370. Figure 4 The period shown is equal to 1 / f (where f=focal length). As will be described in more detail below, according to known principles, the corresponding Z can be established by calibration. L -Height and corresponding phase timing signal value is usually Z L- Height vs. phase calibration (e.g., based on a mathematical model and / or by repeatedly stepping the surface to a known Z L - height, then manually or computationally determine the best focus for the image at the known Z L - The phase sequence of the height and the effective focus position (Z L -Height vs. Phase) The calibration portion stores this relationship in a lookup table or the like, which may be included as part of the lens controller 380 or otherwise).

[0123] Timing diagram 400A shows phase timing (eg, t0, t90, t180, t270, etc.), which are equal to the corresponding phase timing signal value of the control signal PMCS (e.g., t0, t90, t180, t270, etc.), which corresponds to the respective Z L - Height (e.g. In various embodiments, the phase timing signal values ​​(e.g., t0, t90, t180, t270, etc.) may be determined based on the phase timing signal (e.g., as provided by a clock or other technique for establishing timing relative to the periodic modulation, etc.). It will be appreciated that the phase timing signal values ​​shown in the timing diagrams are intended to be exemplary only and not limiting. More generally, any phase timing signal value will have an associated focus position Z within the illustrated focus position range. L - Height (eg, the range in the example shown has a maximum Z L -high and minimum Z L -high ).

[0124] As described above, various techniques may be used (e.g., as part of utilizing multi-point autofocus, point autofocus, maximum confocal brightness determination, etc.) to determine when an imaged surface area is in focus, which may correspond to the Z value of the imaged surface area. L - Height measurement. For example, when the imaged surface area is in focus, the imaged surface area can be determined to be at Z L -high In the use of phase and Z L In the illustrated example of the -height principle, at a phase timing equal to the phase timing signal value Tsurf_ind(-) The focus position is at Z L -high and located at Z L -high The workpiece surface area at is in focus. Similarly, at a phase timing equal to the phase timing signal value Tsurf_ind(+) The focus position is at Z L -high and located at Z L -high The workpiece surface area at which the Z is in focus. It should be understood that such a value may be included in the corresponding Z L - the effective focus position (Z) associated with the corresponding phase timing signal value L -height vs. phase) calibration portion, so that when an imaged surface area is determined to be in focus, the corresponding phase timing signal value (e.g., Tsurf_ind(-)) can be used to look up the corresponding measured Z of the imaged surface area L - Height (e.g. Z L -high ).

[0125] In the illustrated example, the phase timing signal values ​​Tsurf_ind(-) and Tsurf_ind(+) correspond to the movement of the modulated focus position in respective opposite directions. More specifically, the phase timing signal value Tsurf_ind(-) corresponds to the movement of the modulated focus position in a first direction (e.g., downward), while the phase timing signal value Tsurf_ind(+) corresponds to the movement of the modulated focus position in a second direction (e.g., upward) opposite to the first direction.

[0126] Figure 4 It is also qualitatively shown how strobe lighting (e.g., as provided by Figure 3A The exposure time controller 333es can be timed to correspond to the corresponding phase timing of the periodically modulated focus position (for example, etc.), so that the exposure is focused on the corresponding Z L - Images of height (e.g. That is, in the example shown in the figure, when the digital camera collects images during the integration period, if the phase sequence Provided a short strobe pulse, the focus position will be at a height and located at a height Any workpiece surface will be in focus in the resulting image. Figure 4 Other exemplary phase timings and Z shown in L - The same is true for height. According to this principle, it is possible to obtain L Image stacking of highly captured images.

[0127] According to such a principle, the TAG lens system 300 is suitable for quickly performing autofocus operations (e.g., multi-point autofocus operations). Specifically, the TAG lens system 300 can be used to capture an image stack of a workpiece surface including surface positions while periodically modulating the sweep of the focus ZL Range (e.g., focus Z L Autofocus range) of the TAG lens 370 focal length and find the Z position of the workpiece surface L More specifically, as part of a multi-point autofocus process, at least three different regions of interest (ROIs) of the image stack may be analyzed to find at least three Z coordinates corresponding to three workpiece surface locations. L The height (eg, which may be performed simultaneously in certain embodiments) may then be used to calculate / determine the workpiece surface (eg, corresponding to a calculated plane or other representation) and, accordingly, calculate / determine a surface normal to the workpiece surface.

[0128] Figure 5A A sample workpiece WP1 having various workpiece surfaces WPS1, WPS2 and WPS3 is shown. Figure 5A In the example of, with respect to the machine coordinate system (MCS), the workpiece surface WPS2 can be parallel to the horizontal plane, the workpiece surface WPS3 can be parallel to the vertical plane, and the workpiece surface WPS1 can be in a relatively inclined direction. On the workpiece surface WPS1, regions of interest ROI1, ROI2 and ROI3 are shown, each region having a corresponding surface point SP1, SP2 and SP3, which can each be located at the relative center of each corresponding region of interest. As will be described in more detail below, the region of interest can represent an area of ​​interest in an image stack as part of an autofocus process, for which an autofocus height (e.g., Z) can be determined for each corresponding surface point SP1, SP2 and SP3. L Height) (eg, which may be used to determine a plane or other representation and a corresponding surface normal of the workpiece surface WPS1).

[0129] Figure 5B 3 is a schematic diagram showing the distal end of the optical assembly portion 305, the optical axis OA and the image stack acquisition axis ISAA of which are oriented generally in a vertical direction relative to the surface (e.g., a workbench) on which the workpiece WP1 is placed (i.e., the optical axis OA is parallel to the Z axis of the MCS). M -axis). Figure 5C is a schematic diagram of the distal end of the optical assembly portion 305, the optical axis OA and image stack acquisition axis ISAA of the vision probe being oriented at an angle so as to be substantially / nominally normal (eg, perpendicular) to the angled workpiece surface WPS1 of the workpiece WP1.

[0130] To achieve Figure 5C orientation, certain processes may be performed according to the principles disclosed herein. For example, Figure 5BThe configuration can move the optical component part 305 by controlling the adjustment mechanism to place the workpiece surface WPS1 within the focus Z autofocus range of the optical component part 305 (ie, Z L Autofocus range). Figure 5B In the illustration of , this may correspond to positioning the optical component portion 305 at a distance D1 from a location on the workpiece surface WPS1 (e.g., a location where the optical axis OA intersects the workpiece surface WPS1, which in some cases may be generally located at a midpoint or other central location of the workpiece surface WPS1). Figure 5B In the example, the focus Z L The autofocus range is represented by range SR1. Fig. 6A and 6B As described in more detail, as part of the autofocus process, the optical assembly portion 305 may be used to focus the image at the focal point Z. L An image stack of the workpiece surface WPS1 is captured within the autofocus range. The autofocus height may be determined for each of at least three positions (e.g., surface points SP1, SP2, and SP3) of the workpiece surface WPS1 based on at least three corresponding regions of interest ROI1, ROI2, and ROI3 of the image stack, as will be described below with respect to Fig. 6A and 6B Described in more detail. Figure 5B As shown, a surface normal SN of the workpiece surface WPS1 is at an angle ANG1 relative to the optical axis OA of the optical component part 305 .

[0131] like Figure 5C As shown, the adjustment mechanism can be controlled based at least in part on the autofocus height at at least three locations (e.g., surface points) of the workpiece surface WPS1 to: rotate the optical component portion 305 relative to the workpiece surface WPS1 to nominally align the optical axis OA of the optical component portion 305 with the surface normal SN of the workpiece surface WPS1; and adjust the distance between the optical component portion 305 and the workpiece surface WPS1 (e.g., at a distance D2). In various embodiments, when controlling the autofocus height at at least three locations (e.g., surface points) of the workpiece surface WPS1, the adjustment mechanism can be controlled to: rotate the optical component portion 305 relative to the workpiece surface WPS1 to nominally align the optical axis OA of the optical component portion 305 with the surface normal SN of the workpiece surface WPS1; and adjust the distance between the optical component portion 305 and the workpiece surface WPS1 (e.g., at a distance D2). Figure 5C Prior to the adjustment mechanism shown, the determined autofocus heights of the surface points SP1, SP2, and SP3 may be used to calculate or otherwise determine a surface normal SN of the workpiece surface WPS1. For example, three surface points SP1, SP2, and SP3 may be determined to geometrically define a plane (or other representation) corresponding to the workpiece surface WPS1, and the surface normal SN may be calculated and / or otherwise determined accordingly to be normal (i.e., perpendicular) to the calculated / determined plane (or other representation). Once such a surface normal SN is determined, adjustment information may be calculated or otherwise determined, which may be used to control the adjustment mechanism to rotate and otherwise move the optical component portion 305 from Figure 5B Move in the direction shown Figure 5C , for which the optical axis OA is shown as nominally coinciding with the surface normal SN. In addition, an adjustment mechanism (e.g., including a motor 294 or other corresponding mechanism) can be used to adjust the distance between the optical component portion 305 and the workpiece surface WPS1. Figure 5C As shown, the adjustment results in a distance D2 between the optical component portion 305 and the workpiece surface WPS1. Figure 3A and 3B As described, in various embodiments, distance D2 may correspond to a desired Z L The workpiece surface WPS1 is at a position (eg, nominally at or near: the middle of the range SR2; and / or the working distance of the objective lens of the optical assembly portion 305; and / or the best focus position, etc.).

[0132] Once in Figure 5C With the orientation and position shown, a defined operation can be performed on the workpiece surface WPS1. For example, a measurement operation using the optical assembly portion 305 can be performed on the workpiece surface WPS1. As part of such a process or otherwise, a point from focusing operation can be performed on the workpiece surface WPS1 (e.g., for determining a surface profile). As part of a point from focusing operation, the optical assembly portion 305 can be used to measure the surface of the workpiece surface WPS1. Figure 5C In various embodiments, the process can be repeated / continued (e.g., to perform defined operations on other portions of the workpiece surface WPS1 or other workpiece surfaces of the workpiece WP1), and for this purpose, the optical assembly portion 305 can be rotated from Figure 5C The orientation shown in FIG. 1 is to another portion of the workpiece that is nominally perpendicular to the workpiece surface or another surface of the workpiece (eg, for tracking and measuring different portions of a workpiece, such as a continuously curved turbine blade, etc.).

[0133] Figure 5B and 5C It can be understood that the scanning range required for covering the 3-dimensional surface topography of the workpiece surface WPS1 (for example, Figure 5B compared to, Figure 5C range), which depends on the orientation of the optical component part 305 relative to the workpiece surface WPS1 to be measured. Figure 5C Compared with the scanning range SR2 in the direction of Figure 5B The scanning range SR1 of the orientation is significantly larger, so that the 3D surface topography of the workpiece surface WPS1 can be covered. Figure 5CAdjusting the angle / orientation of the optical component portion 305 as in , so that the optical axis OA is nominally normal to (i.e., approximately perpendicular to) the workpiece surface WPS1 is technically advantageous in reducing the required scanning range, which in turn can shorten the scanning time and / or reduce the number of images required to form an image stack (e.g., having a desired image density, etc.).

[0134] like Figure 5B As shown, except that the scanning range SR1 for image stacking is significantly larger than Figure 5C In addition to the scanning range SR2 of the optical component portion 305, the orientation of the optical component portion 305 is also at a relatively acute angle relative to the workpiece surface WPS1, which may reduce the imaging quality or prevent the imaging of certain parts / aspects of certain workpiece features. For example, the acute angle can reduce the imaging quality because less imaging light is reflected back to the optical component portion 305, etc. In comparison, in Figure 5C By orienting the optical component portion 305 to be nominally normal to (i.e., approximately perpendicular to) at least a portion of the workpiece surface WPS1, the optical component portion 305 can have a better angle for imaging the workpiece surface WPS1 (e.g., having a better angle for reflecting imaging light and / or being able to better view certain workpiece features, etc.).

[0135] In various embodiments, as described above, it may also be desirable to continue rotating / adjusting optical assembly portion 305 to be in different orientations to perform processing on different workpiece surfaces or different portions of a workpiece surface of a workpiece. Figures 5A-5C The workpiece WP1 in FIG. 1 is considered to include workpiece surfaces WPS1, WPS2, and WPS3. In one embodiment, the optical component portion 305 may initially be (or may be adjusted to be) such as Figure 5B The optical axis OA is positioned / oriented as shown (e.g., the optical axis OA has a 0 degree tilt relative to the vertical orientation and is nominally perpendicular to the workpiece surface WPS2) for performing certain operations on the workpiece surface WPS2 (e.g., measurement operations, acquiring image stacks for PFF scanning, etc.). Then, the process disclosed herein can be performed, including performing multi-point autofocus on the workpiece surface WPS1 and rotating the optical assembly portion 305 so that the optical axis OA is as shown. Figure 5CThe optical component portion 305 is oriented as shown (e.g., tilted 45 degrees relative to vertical and nominally perpendicular to the workpiece surface WPS1) to perform certain operations on the workpiece surface WPS1 (e.g., measurement operations, acquisition of image stacks PFF for scanning, etc.). Then, the process as disclosed herein can be performed again, including moving the optical component portion to position the workpiece surface WPS3 within the focal point Z autofocus range and performing multi-point autofocus on the workpiece surface WPS3 and rotating the optical component portion 305 so that the optical axis OA is oriented (e.g., tilted 90 degrees relative to vertical and nominally perpendicular to the workpiece surface WPS3) to perform certain operations on the workpiece surface WPS3 (e.g., measurement operations, acquisition of image stacks for PFF scanning, etc.). In various embodiments, the process as disclosed herein can also be initially performed to achieve Figure 5B orientation (eg, the optical axis OA is nominally perpendicular to the workpiece surface WPS2 and for this purpose a specified operation can be performed (ie, carried out) on the workpiece surface WPS2).

[0136] It should be understood that in various embodiments as part of such a process, the optical axis OA of the optical assembly portion 305 may be nominally normal (i.e., approximately perpendicular) to only a portion of the workpiece surface, or in some cases may not actually be nominally normal (i.e., approximately perpendicular) to any particular portion of the workpiece surface, but rather may be nominally perpendicular only to a general overall or average (e.g., calculated) etc. orientation of the workpiece surface. For example, if the workpiece surface is particularly non-planar and / or includes a large number of workpiece features that form a complex or non-uniform 3-dimensional profile / surface topography, the optical axis OA may not be precisely or nominally normal / perpendicular to any particular portion of the workpiece surface, but may be approximately / nominal normal / perpendicular to the overall, average, and / or general (e.g., calculated) etc. orientation or predominant angle of the workpiece surface, for which the optical axis OA may be considered to be nominally perpendicular to the workpiece surface, as described herein.

[0137] Fig. 6A and 6B shows how to use an image stack including images of different focal lengths obtained by optical assembly part 205 or 305 to obtain images along Z L -axis determines the autofocus height of at least three points on the workpiece surface (i.e., the autofocus position or Z L Position or Z L Height). As used herein, “Z LThe "-axis" may correspond to the Z axis of the local coordinate system (LCS) of the optical component portion 205 or 305 (i.e., corresponding to the optical axis OA of the optical component portion 205 or 305). In various embodiments, the image stack IS may be obtained by the optical component portion 205 or 305 operating in a multi-point autofocus mode (e.g., and / or other modes, such as PFF, etc.) to determine the autofocus height (i.e., Z axis) of at least three locations (e.g., surface points) on the workpiece surface. L - Height or Z L - position) (e.g. in one direction, e.g. Figure 5B direction shown).

[0138] Specifically, Fig. 6A and 6B The optical axis direction (ie, the Z direction of the optical component part 205 or 305) is shown for each of one or more points on the workpiece surface. L - coincidence) relative Z L -position (i.e., autofocus height). Fig. 6A and 6B As shown, the focus position of the optical assembly portion 205 or 305 can be moved along the optical axis and / or the image stack acquisition axis through position Z. L (i) The direction may correspond to the focal axis at each image acquisition position. The optical component part 205 or 305 may be at each position Z L The image (i) is captured at (i). For each captured image (i), a focus metric fm(k,i) can be calculated based on a region or sub-region of interest ROI(k) (e.g., a set of pixels) in the image (e.g., where the corresponding surface point is at the center of the region or sub-region of interest ROI(k)). The focus metric fm(k,i) is related to the focus position of the optical component portion 205 or 305 along the direction of the optical axis and / or the image stack acquisition axis when the image (i) is captured (e.g., based on the phase timing of the VFL lens 270 or 370 and / or the distance to the workpiece surface). This generates focus curve data (e.g., position Z L A set of focus metrics fm(k,i) at (i), which is a type of focus peak determination data set), may be simply referred to as a "focus curve" or "auto-focus curve". In one embodiment, the focus metric value may involve a calculation of the contrast or sharpness of a region of interest in the image.

[0139] The Z corresponding to the peak of the focusing curve L - Location (e.g. Fig. 6A Z L k601), which corresponds to the best focus position along the image stack acquisition axis and is the Z region of interest used to determine the focus curve.L position. It will be appreciated that although the image stack is shown as including eleven images (image (1)-image (11)) for illustrative purposes, in actual embodiments, a fewer or greater number of images may be utilized. For example, some autofocus processes may typically acquire an image stack including 5-10 images, while, in contrast, some PFF processes may acquire an image stack including over 200 images. Furthermore, the images in an image stack may be smaller or larger (e.g., including fewer or more regions of interest of a given size), depending on the implementation (e.g., as may be related to the size of the camera field of view and / or other factors).

[0140] As shown in the autofocus curves generated for images (1)-(11), in the illustrated example, image (6) (i.e., having a corresponding focus metric fm(1,6)) appears to be close to or in optimal focus. For example, features in the middle of ROI (1) (e.g., in the middle of ROI (1)) may appear to be in optimal focus, compared to other images where that portion of the workpiece surface may appear increasingly out of focus and may appear increasingly blurred for images farther from image (6). Figure 5A The surface point SP1 in the ROI (6) appears to be in the best focus in the image (6). When the focus metric is based on contrast as described above, one method includes comparing the center pixel of the ROI (e.g. corresponding to the surface point SP1) with its neighboring pixels in the ROI in terms of color / brightness, etc. By finding the image with the highest overall contrast (corresponding to the focus position when the image was acquired), the relative Z of the surface point (e.g., the surface point SP1 at the center of the ROI (1)) can be obtained along the optical axis OA and the image stack acquisition axis. L - Indication / measurement of position (i.e. AF height).

[0141] In the above mentioned Figure 6B In the example, the central region of interest ROI (1) is considered to be roughly in focus on the image (6), which corresponds to the position Z along the optical axis of the optical component part 205 or 305. L (6). Therefore, it can be determined that the surface point (e.g., surface point SP1) on the workpiece surface corresponding to the center of ROI (1) is located at the relative position Z L (6) because this position approximately corresponds to the focus position of ROI (1) of image (6) in the image stack. Similar processing can be performed for each of the regions of interest ROI (2) and ROI (3) to determine the relative Z coordinates of the surface points (e.g., surface points SP2 and SP3, respectively) corresponding to the centers of ROI (2) and ROI (3). L Specifically, the following can be generated for ROI(2) and ROI(3): Fig. 6AThe autofocus curve shown is used to find the best focus image in the corresponding ROI region of interest. For example, assuming that image (5) appears at the best focus in ROI (2) and image (7) appears at the best focus in ROI (3), the autofocus height Z of the surface position at the center of ROI (2) can be determined. L (5), the autofocus height of the surface position at the center of ROI (3) is Z L (7).

[0142] Z of three regions of interest ROI(1), ROI(2), and ROI(3) (eg, with corresponding center surface points SP1, SP2, and SP3) L Height / Autofocus Height (Z L position) can be used to define the corresponding to include or otherwise represent Z L The plane or other representation of the surface of the position / surface point and the surface normal SN defining / determining the surface can be calculated / determined. As previously described, at least three Z L position (i.e., autofocus height) to define the surface, although more than three Z L In various embodiments, multiple regions of interest ROI(1), ROI(2), ROI(3) ... ROI(n) may be processed based on the same (single) image stack, for which, in some cases, it may not be necessary to acquire multiple image stacks to calculate / determine multiple Z L It will be appreciated that in some cases the determined peak focus position (i.e. corresponding to the autofocus height) may fall between two images in the image stack, for which the focus peak position may be determined by interpolation or other techniques based on a fit of the focus curves to the focus metric values ​​determined for the images.

[0143] In various embodiments, Fig. 6A and 6B The illustrations may also represent an image stack obtained by the optical assembly portion 205 or 305 operating in a point focus (PFF) mode (or other mode) to determine the Z coordinates of a plurality of surface points on the workpiece surface. L - Height (i.e., Z L - position). PFF image stacks can be processed to determine or output Z L Height coordinate map (such as point cloud), the Z LThe height coordinate map quantitatively indicates a set of 3-dimensional surface coordinates (e.g., corresponding to the surface shape or contour of the workpiece). Compared with the multi-point autofocus image stack, the PFF image stack can generally contain more images and involve the calculation / determination of more surface points (e.g., for accurate determination of detailed surface contours, etc.), and may accordingly involve a more time-consuming process. For example, in some embodiments, the PFF image stack may include at least 10x, 20x, or 40x, etc. more images than the multi-point autofocus image stack (e.g., as some specific example values ​​in certain embodiments, the multi-point autofocus image stack may include 5-10 images / camera frame, while the PFF image stack may include more than 200 (e.g., 220, etc.) images / camera frame). According to the principles disclosed herein, in relation to nominally aligning the optical axis of the optical component portion with the surface normal of the workpiece surface, the multi-point autofocus image stack can be acquired and processed relatively quickly (e.g., captured with fewer images and fewer surface points and corresponding processing). Thereafter, with the optical component portion so aligned, defined operations (e.g., including PFF operations, etc.) can be performed on the workpiece surface. A PFF operation may provide more detailed information about the surface profile of a workpiece surface, and for this purpose nominally aligning the optical axis with the surface normal may have various advantages (eg, with respect to performing PFF and / or other processes).

[0144] Figure 7 4 is a robotic system 400 that embodies a metrology system of the present disclosure including an optical assembly portion 405 (similar to optical assembly portions 205 and 305) according to an aspect of the present disclosure. The robotic system 400 includes an adjustment mechanism 401 in the form of an articulated arm having multiple degrees of freedom. In various embodiments, the adjustment mechanism 401 (i.e., the articulated arm) can generally be used as (e.g., including the operation of certain portions of the articulated arm) a Z-axis translation mechanism that is configured to change the distance between the optical assembly portion 405 and the workpiece surface 320A, and can also generally be used as (e.g., including the operation of certain portions of the articulated arm) a rotation mechanism that is configured to rotate the optical assembly portion to change the angular orientation of the optical axis relative to the workpiece surface 320A.

[0145] The optical assembly portion 405 includes a camera 360, a VFL (TAG) lens 370, and an illumination source 330. In various implementations, the illumination source 330 may be a ring light (e.g., formed by an array of LEDs) disposed at the distal end of the optical assembly portion 405 in the illustrated embodiment, although the illumination source 330 may alternatively be, for example, a coaxial light. The robotic system 400 includes a controller 425 that includes or is coupled to VFL (TAG) lens control software and robotic integration software that is responsible for controlling the optical assembly portion 405 incorporated into the robotic system 400. In the illustrated embodiment, the optical assembly portion 405 is coupled to the distal end of the articulated arm 401. The controller 425 of the robot system 400 can move the optical component part 405 to change the distance to the workpiece surface 320A by controlling the articulated arm 401 (for example, using the Z-axis moving mechanism part of the articulated arm 401), and can rotate the optical component part 405 to change the angular orientation of the optical axis OA of the optical component part 405 relative to the workpiece surface 320A (for example, using the rotating mechanism part of the articulated arm 401).

[0146] With the above Figures 2A-3B As in the embodiment of the present disclosure, the controller 425 of the robotic system 400 can implement the method of the present disclosure, including: positioning the optical component part 405 so that the workpiece surface 320A is within the autofocus range; capturing an image stack of the workpiece surface at multiple focal lengths within the autofocus range (for example, by controlling the TAG lens 370 and / or moving the optical component part 405); determining the autofocus heights of at least three locations on the workpiece surface based on at least three corresponding ROIs of the image stack (for example, to this end, the surface normal and adjustment information can be determined based on the determined autofocus heights); controlling the adjustment mechanism based at least in part on the determined autofocus heights to: rotate the optical component part relative to the workpiece surface to nominally align the optical axis of the optical component part 405 with the surface normal of the workpiece surface 320A; and adjust the distance of the optical component part from the workpiece surface; and performing a defined operation on the workpiece surface 320A.

[0147] Figures 8A-8E A coordinate measuring machine (CMM) 500 is illustrated that embodies a metrology system including an optical assembly portion 505 according to another aspect of the present disclosure. Fig. 8A As shown, the coordinate measuring machine 500 includes a machine body 501 that moves an optical assembly part 505 (for example, which may be included in a vision probe), an operating unit 503 having a manual joystick 506, and a processing device configuration 509. The machine body 501 includes a panel 510 (for example, a workpiece table) and an adjustment mechanism 520 (see also FIG. 5 ) that moves the optical assembly part 505. Fig. 8EThe adjustment mechanism 520 includes an X-axis sliding mechanism 525, a Y-axis sliding mechanism 526, and a Z-axis sliding mechanism 527, which are arranged on the panel 510 to hold and three-dimensionally move the optical component part 505 relative to the workpiece WP to be measured. Fig. 8A The adjustment mechanism 520 further includes a rotation mechanism 595 .

[0148] Specifically, the adjustment mechanism 520 includes a plurality of adjustment mechanisms capable of adjusting the Y axis in the machine coordinate system (MCS). M The beam supports 521 are movable in the X direction, the beams 522 are bridged between the beam supports 521, and the beams 522 are movable in the X direction in the machine coordinate system. M The column 523 is movable on the beam 522 in the Z direction and is capable of moving along the Z direction in the machine coordinate system. M The Z-axis moving member 524 moves in the column 523, as shown in FIG. Fig. 8A shown. Fig. 8A The X-axis sliding mechanism 525, the Y-axis sliding mechanism 526, and the Z-axis sliding mechanism 527 are respectively arranged between the beam 522 and the column 523, between the panel 510 and the beam support 521, and between the column 523 and the Z-axis moving member 524. The optical component part 505 is attached to the probe head 513, which may include a rotating mechanism 595 and is attached to and supported by the end of the Z-axis moving member 524. The rotating mechanism 595 enables the optical component part 505 to rotate. The X-axis sliding mechanism 525, the Y-axis sliding mechanism 526, and the Z-axis sliding mechanism 527 are each configured to move in the MCS along mutually orthogonal X, Y, and Z axis directions (i.e., X, Y, and Z axis directions, respectively). M , Y M and Z M direction) to move the optical component part 505.

[0149] like Fig. 8E As shown, the X-axis sliding mechanism 525, the Y-axis sliding mechanism 526, and the Z-axis sliding mechanism 527 are respectively provided with an X-axis scale sensor 528, a Y-axis scale sensor 529, and a Z-axis scale sensor 530. Therefore, the movement amount of the optical component part 505 in the X-axis, Y-axis, and Z-axis directions in the machine coordinate system (MCS) can be obtained from the outputs of the X-axis scale sensor 528, the Y-axis scale sensor 529, and the Z-axis scale sensor 530. In the illustrated embodiment, the movement directions of the X-axis sliding mechanism 525, the Y-axis sliding mechanism 526, and the Z-axis sliding mechanism 527 are respectively in the X-axis, Y-axis, and Z-axis directions in the machine coordinate system (MCS). M Direction, Y M Direction and Z M In various embodiments, these relatively direct dependencies and associated components can help ensure a high level of consistency in X M , Y M and Z MThe probe head 513 with the rotation mechanism 595 includes one or more rotation sensors 515 (see Fig. 8E ) for sensing the angular rotation / position / orientation of the optical component portion 505, which will be described in more detail below.

[0150] In various embodiments, such as Fig. 8A and 8E As shown, the adjustment mechanism 520 including the X-axis, Y-axis and Z-axis slide mechanisms 525, 526 and 527 and the rotation mechanism 595 can be controlled to move and align the optical axis OA of the optical assembly portion 505 nominally perpendicular to any workpiece surface. Figures 2A-3B As in the embodiment of 7, Figure 8C , 8D As shown in FIG8E , the optical assembly portion 505 may include a light source 330 and an optical component portion 306 (eg, may include an objective lens 350 , a camera 360 , and a VFL (eg, TAG) lens 370 ).

[0151] like Fig. 8A and 8E As shown, the operation unit 503 is connected to the command part 602 of the controller 625. The controller 625 includes or is coupled to a motion controller 540 configured to control the motion of the optical component part 505. Various commands can be input to the machine body 501 and the controller 625 via the operation unit 503. Fig. 8A As shown, controller 625 may be embodied in a processing unit of a computer system.

[0152] With the above Figures 2A-3B As in the embodiment of 7, the controller 625 of the CMM 500 can implement the method of the present disclosure, including: positioning the optical component part 505 relative to the workpiece surface (WPS1) so that the workpiece surface is within the autofocus range; capturing an image stack of the workpiece surface at multiple focal lengths within the autofocus range (for example, by controlling the TAG lens 370 and / or moving the optical component part 505); determining the autofocus heights of at least three positions on the workpiece surface based on at least three corresponding ROIs of the image stack (for example, to this end, the surface normal and adjustment information can be determined based on the determined autofocus heights); and controlling the adjustment mechanism 520 based at least in part on the autofocus heights determined for the at least three positions to: rotate the optical component part 505 relative to the workpiece surface WPS1 to nominally align the optical axis OA of the optical component part 505 with the surface normal SN of the workpiece surface WPS1; and adjust the distance between the optical component part and the workpiece surface; and perform a defined operation on the workpiece surface WPS1.

[0153] like Fig. 8E As shown, the controller 625 includes a command part 602 , an adjustment mechanism controller 604 , a position determination part 606 , an optical component part controller 608 , an optical component part data part 610 , an analyzer part 612 and a storage part 614 . Fig. 8E The command section 602 is shown issuing commands to the adjustment mechanism controller 604. The command section 602 generates coordinate values ​​in the machine coordinate system as position commands to the adjustment mechanism 520 for each control cycle, taking into account, for example, the moving direction, moving distance, moving speed, etc., to move the optical component section 505 to a plurality of positions and orientations. Fig. 8E The adjustment mechanism controller 604 shown in the figure performs drive control by outputting a drive control signal D in response to a command from the command part 602, thereby causing current to flow through the x-axis, y-axis and z-axis sliding mechanisms 525, 526 and 527 in the adjustment mechanism 520 and the motor of the rotating mechanism 595.

[0154] In one embodiment, the position latch 516 communicates with various sensors and / or drive mechanisms to ensure that the coordinates of the CMM 500 and the optical assembly portion 505 are properly synchronized when acquiring images. More specifically, in various embodiments, the position latch 516 can be used to help ensure the accuracy of measurements and / or other determinations derived from images in the image stack. In various embodiments, the operation of the position latch 516 enables the CMM machine coordinates (which reflect the location of the connection points or other reference points of the optical assembly portion 505 during a particular measurement) to be properly combined with the position data determined from the optical assembly portion image (e.g., the position and orientation relative to the optical assembly portion 505 itself). In certain embodiments, the position latch 516 can be used to trigger measurements from CMM position sensors (e.g., sensors 515 and 528-530, etc.), which may include scales, encoders, or other sensing elements that track the overall position and orientation of the optical assembly portion 505 (e.g., including its base position) in the machine coordinate system. In some embodiments, the position latch 516 can also trigger image acquisition from the optical component portion 505 (e.g., as part of an image stack, a trigger signal can be provided for each image in the image stack, where the corresponding position of the optical component portion 505 and / or the phase timing of the VFL lens 370 are also synchronized and / or tracked accordingly for each image acquisition).

[0155] When only the optical assembly portion 505 is used, the CMM adjustment mechanism 520, and in particular its sensors (515 and 528-530), can provide measurement outputs M to a position determination portion 606 that determines the position of the probe head 513 (or other connection points or reference locations) of the optical assembly portion 505 within the machine coordinate system (MCS) of the CMM. For example, the position determination portion 606 can provide X, Y, and Z coordinates (i.e., X coordinates) for the probe head 513 or other connection points or reference locations of the optical assembly portion 505 within the machine coordinate system. M , Y M and Z M coordinate).

[0156] When the optical assembly portion 505 is used as described herein with respect to various exemplary embodiments (e.g., with respect to certain defined operations or otherwise), the position determination portion 606 can determine the position of the probe 513 on top of the optical assembly portion 505 (or other reference or attachment location). To determine the coordinates of a surface point on a workpiece, information from an analysis of an image stack can be used. For example, a stack of images (of images at different focus positions) can be acquired by the optical assembly portion 505, where the relative positions / focus positions of the images in the image stack are with respect to an optical assembly portion local coordinate system (LCS), which in some embodiments can be related to a reference position of the optical assembly portion within the MCS. To determine the overall position of a surface point within a machine coordinate system (MCS), in some embodiments, the LCS position data of the surface point can be converted and / or otherwise combined with the MCS position data to determine the overall overall position of the surface point.

[0157] When the optical component portion 505 is oriented at an angle (e.g., Fig.8D As shown in Figure 2, the Z axis (i.e., Z) of the local coordinate system (LCS) of the optical component is L When the optical component 505 is oriented at a certain angle (i.e., corresponding to the optical axis OA of the optical component part 505), the acquired image stack indicates the relative distance (e.g., autofocus height or Z) of the surface points of the workpiece along the direction of the Z-axis of the optical component part oriented at the angle. LHeight). In some embodiments, those LCS coordinates can be combined (e.g., converted, added to, etc.) with the MCS coordinates determined for the probe head 513 (or other reference position) to determine the overall position of the surface point on the workpiece in the MCS. For example, if it is desired to determine the coordinates of the surface point based on the MCS, the measurement point determined in the local coordinate system LCS of the optical component portion can be converted to MCS coordinates and added to or otherwise combined with other MCS coordinates of the probe head 513 of the optical component portion 505 (or other reference position). Optionally, if the workpiece itself is assigned its own local coordinate system, the MCS coordinates and / or LCS coordinates determined for the probe head 513 of the optical component portion 505 (or other reference position) can be converted or combined with the local coordinate system of the workpiece. As another example, in some cases, other local coordinate systems (e.g., images for image stacking, etc.) may also or optionally be established. Typically, the MCS covers the coordinates of the overall large volume of the CMM 500, while local coordinate systems typically cover smaller volumes and may typically be included in the MCS in some cases. In various embodiments, as part of the MCS and / or local coordinate system, in addition to X, Y, and Z coordinates, some type of cylindrical, Cartesian, or other coordinates may also or alternatively be utilized with respect to the orientation of the optical assembly portion 505 and the determination of the coordinates of the measured surface points on the workpiece WP. It should be understood that such principles for determining coordinates are also applicable and can be used in other systems described herein (e.g., with respect to Figures 2A-3B , 5A-5C, 7, etc.).

[0158] In some embodiments, position data with respect to the LCS from the image stack can be utilized relatively independently (e.g., with limited or no transformation or combination with coordinates from the MCS or other coordinate system). For example, position data determined from analysis of the image stack can provide 3D coordinates indicating the 3D position of a surface point on the workpiece surface with respect to the LCS, which therefore represents / corresponds to the 3D contour / surface topography of the workpiece surface. As described above, in some embodiments, such data can be combined with other position data represented in the MCS to indicate the overall position of the workpiece surface and surface points within the MCS. However, for certain embodiments, analyses and / or representations, etc., it may be desirable to utilize primarily or only position data determined from the image stack. For example, if the analysis or inspection is primarily to determine the relative position and / or characteristics of workpiece features on the workpiece surface (e.g., where the relative surface / plane is determined / calculated in conjunction with the surface normal and / or other with respect to the distance between workpiece features on the workpiece surface and / or the 3D size of the workpiece features on the surface, etc.), then in some embodiments such data can be determined primarily from the analysis of the image stack. More specifically, if the desired analysis / inspection does not require the overall position within the MCS of the workpiece surface and / or workpiece features, the data determined from the image stack may be utilized with limited or no combination with other MCS or other coordinate system coordinates. In addition to analyzing such data, it will be appreciated that for some operations, a 3D representation of the workpiece surface (e.g., on a display, etc.) may also be similarly determined and / or provided based on data from an analysis of the image stack (e.g., as part of a PFF process, etc.).

[0159] like Fig. 8E As shown, the optical assembly portion controller 608 controls the optical assembly portion 505 (e.g., controls the illumination configuration 330, the camera 360, the VFL lens 370, etc. to obtain images of the image stack, etc.). In various embodiments, certain portions of the movement or focus of the optical assembly portion 505 may be controlled by the CMM adjustment mechanism 520, which moves the optical assembly portion 505 closer to and / or further away from the workpiece, wherein the rotation mechanism 595 may be used to rotate the optical assembly portion 505 to a desired angle / direction (e.g., nominally perpendicular to the workpiece surface). In various embodiments, the focal length of the optical assembly portion 505 may be at least partially determined by the objective lens 350 (e.g., in conjunction with the VFL lens 370, wherein the focal length in front of the optical assembly portion 505 may change during the measurement operation based on the operation of the VFL lens 370). The optical assembly portion data portion 610 receives the output of the optical assembly portion 505 (i.e., image data for the images of the image stack). The analyzer portion 612 may be used to perform relevant analysis (e.g., point self-focus (PFF) analysis or other analysis of the image stack for the optical assembly portion along the Z-axis direction (i.e., Z LThe storage portion 614 may include a portion of a computer memory for storing certain software, routines, data, etc., for operation of the system, etc.

[0160] Figure 8B 5 is a diagram schematically showing certain components of the machine body 501 and the optical assembly part 505 of the CMM 500. Figure 8B As shown, the machine body 501 includes a probe head 513. The probe head 513 receives and transmits signals via a probe head cable 511. The probe head 513 is fixed to a coordinate measuring machine spindle (quill) 517, which is attached to the coordinate measuring machine spindle along the Z-axis direction (i.e., Z) of the MCS. M The probe head 513 is connected to the optical assembly portion 505 at the probe automatic joint connection 531. One implementation of the probe automatic joint connection is described in more detail in U.S. Patent No. 9,115,982, the entire contents of which are incorporated herein by reference.

[0161] The probe head 513 in the illustrated embodiment includes a rotation mechanism 595 that, in some embodiments, rotates 360 degrees in a horizontal plane (e.g., the first rotation sensor 515 can sense its angular movement / position / orientation) and can include a U-joint (e.g., which enables the connected optical component parts to rotate about corresponding axes located in the horizontal plane, and the second rotation sensor 515 can sense its angular movement / position / orientation). Figure 8B In a specific example of the probe head 513, the rotation mechanism 595 supports the rotation of the optical component portion 505 about two different axes: first, rotating (turning) the optical component portion 505 about the Z-axis of the MCS in the current orientation, and second, rotating the optical component portion 505 about the horizontal axis (i.e., the axis in the XY plane of the MCS). In some embodiments, the rotation mechanism 595 including a spherical (or ball-like) joint allows the optical component portion 505 to rotate relative to the Z-axis translation member 524 within the column 523 and / or relative to any horizontal axis to position the optical axis OA of the optical component portion 505 at a desired angle / direction relative to the workpiece surface (e.g., nominally perpendicular to the workpiece surface). In general, the rotation mechanism 595 is a mechanism for changing the orientation of the optical component portion 505 (i.e., the posture of the optical component portion 505).

[0162] The probe auto-joint connector 531 is an electromechanical connector that rigidly and mechanically secures the probe head 513 to the optical assembly portion 505 in a manner that allows the probe head 513 to be disconnected from one probe (e.g., including an optical assembly portion) and attached to another probe. In one embodiment, the probe auto-joint connector 531 may include a first mating auto-exchange joint element 534 and a second mating auto-exchange joint element 536, wherein the first auto-exchange joint element 534 is mounted to the probe head 513 and the second mating auto-exchange joint element 536 is mounted to the optical assembly portion 505. In one embodiment, the probe auto-joint connector 531 has mating electrical contacts or connectors 535 such that when the probes are attached, the contacts automatically engage and form an electrical connection.

[0163] The optical assembly portion 505 may receive at least some of its power and control signals through the self-splicing connection 531, which in turn may pass through the probe head cable 511. Signals transmitted to the optical assembly portion 505 through the self-splicing connection 531 may pass through the connection 535. Fig. 8E As shown, the optical assembly part 505 includes an automatic exchange joint element 536 and a probe assembly 537 mounted on the automatic exchange joint element 536 for automatic connection to the CMM 500 via a probe automatic joint connection part 531.

[0164] In various embodiments, optical assembly portion 505 may also or alternatively have at least some of its power and control signals delivered via cable 511'. In some embodiments, cable 511' may be used due to standard auto-splicing connections 531 having a limited number of available wired connections, and more connections may be desired / utilized for optical assembly portion 505 (e.g., as provided via optional cable 511'). In various embodiments, power and / or communication signals for optical assembly portion 505 (e.g., when delivered via cable 511 and / or cable 511') may go to and from optical assembly portion controller 608 and optical assembly portion data portion 610 (see Fig. 8E ). The optical assembly portion data portion 610 receives the output of the optical assembly portion 505 (i.e., image data of the image for the image stack). The analyzer portion 612 can be used to perform relevant analysis of the image stack, such as autofocus processing to calculate / determine the autofocus height of at least three locations on the workpiece surface (e.g., can be used to calculate / determine the surface normal of the workpiece surface), etc. The storage portion 614 can include a portion of a computer memory for storing certain software, routines, data, etc. for the operation of the controller 625, etc.

[0165] Although in Fig. 8A and 8BThe rotating mechanism 595 is shown as including a U-shaped joint, but the configuration of the rotating mechanism 595 is not limited thereto. For example, the rotating mechanism 595 may be provided in the form of a rotating table included in or on the panel 510 of the CMM 500 to support the workpiece WP (see Fig. 8A ), or provided in the form of a rotary table at the distal end of the Z-axis moving member 524 of the CMM 500 (e.g., similar to Figure 1-3B Rotating table 297).

[0166] Figure 8C and 8D Shows relative to Fig. 8A and 8B Certain components of the CMM 500, including certain parts of the adjustment mechanism 520, which includes a rotation mechanism 595' (embodied in the probe head 513') of the machine body 501 of the CMM 500. Figure 8C The optical assembly portion 505 is shown in the vertical direction (e.g., similar to some prior art systems such as some vision systems that are primarily operated only along the Z direction of the machine coordinate system). M -axis direction to move the focus position up and down to obtain an image stack containing the workpiece image). Figure 8C As shown, the workpiece WP has a workpiece surface WPS1 having an angular orientation (at an angle A1). Figure 8C In the illustration of FIG. 5 , the Z axis of the machine coordinate system is parallel to the optical axis OA of the optical assembly portion 505. It will be appreciated that if the Z axis slide mechanism 527 is simply moved along the Z axis of the MCS, the optical axis OA of the optical assembly portion 505 is parallel to the optical axis OA of the optical assembly portion 505. M -axis moves the optical component part 505 up and down (including the movement of the Z-axis moving member 524 in the column 523), then the optical axis (Z L -axis) can be aligned with the Z axis of the machine coordinate system M -axis and the image stack acquisition axis ISAA are in the same direction. The workpiece surface WPS1 is shown at an angle A1 relative to the horizontal plane of the MCS. In contrast, the workpiece surface WPS2 of the workpiece WP in the MCS is shown as being substantially parallel to the horizontal plane. The surface normal SN of the workpiece surface WPS1 is shown as being at an angle A2 relative to the optical axis OA (e.g., the optical assembly portion 505 may be rotated by an amount indicated by the angle A2, as shown in FIG. Fig.8D shown).

[0167] Fig.8DThe optical assembly portion 505 is shown having been rotated (by angle A2) to an angle relative to a horizontal plane of the MCS (at angle "AH") and a vertical plane of the MCS (at angle "AV"), as may be achieved by the disclosed CMM 500, in accordance with various embodiments of the present disclosure. The optical assembly portion 505 has been rotated (e.g., by a U-joint or other component of the rotation mechanism 595' of the probe head 513') about a horizontal rotation axis RA2 passing through a rotation point R2 to point at the angle AH and with the optical axis OA of the optical assembly portion 505 nominally normal to (e.g., substantially perpendicular to) the workpiece surface WPS1. Fig.8D , the ability of the rotation mechanism 595' of the probe head 513' to rotate the optical assembly portion 505 about the Z-axis of the MCS is illustrated by the rotation axis RA1 passing through the rotation point R1 at the top of the probe head 513' / rotation mechanism 595'. Rotation about the horizontal axis is limited by the rotation point R2 passing through the center of the probe head 513' / rotation mechanism 595' (e.g., according to FIG. Figure 8B The operation of the illustrated U-joint) is illustrated according to the rotation axis RA2 (ie, represented as a single point due to its pointing to the page).

[0168] exist Fig.8D , an example image stack range SR-3B is illustrated, which in various embodiments may be part or all of an autofocus range or a PFF range (e.g., for determining a 3-dimensional surface profile of a workpiece surface WPS1), etc. The workpiece surface WPS1 may have various workpiece features (e.g., surface features) that may be above or below an average planar position of the workpiece surface WPS1. In some embodiments, it may be desirable to have the range of individual focus positions of the image stack extend a certain distance above and below the workpiece surface. Fig.8D As shown, the example image stacking range SR-3B can be significantly smaller than Figure 8C Image stacking range SR-3A (i.e., Figure 8C The image stacking range required to cover all surface points of the workpiece surface WPS1 in the direction shown in FIG. 1 is due to the following facts: Fig.8D The optical component portion 505 in FIG. 5 is oriented so that its optical axis OA is nominally normal to (i.e., substantially perpendicular to) the workpiece surface WPS1, as shown in FIG. Figure 8C The relative angles in the contrast. Fig.8D , the angle of the optical axis OA (and image stack acquisition axis ISAA) relative to at least a portion of the workpiece surface WPS1 is indicated as "AP", which is nominally normal (ie, approximately 90 degrees / vertical) in the illustrated example. Fig.8D Also shown is the angle of the workpiece surface WPS1 relative to the horizontal plane "AW" (eg, corresponding to Figure 8CDepending on the particular angle AW in each embodiment, the rotation mechanism 595' can be adjusted to ensure that the optical axis OA (and ISAA) of the optical assembly portion 505 is nominally normal (ie, substantially perpendicular) to at least a portion of the workpiece surface WPS1.

[0169] To achieve Fig.8D The orientation of Figure 5B and 5C For example, Figure 8C The configuration can be achieved by controlling the adjustment mechanism 520 to move the optical component part 505 to place the workpiece surface WPS1 within the focus Z autofocus range of the optical component part 505. Figure 8C In the illustration of , this may correspond to positioning the optical component portion 505 at a distance D-8C from a position on the workpiece surface WPS1 (e.g., a position where the optical axis OA intersects the workpiece surface WPS1, which in some cases may be located at or near the midpoint or other center position of the workpiece surface WPS1). Figure 8C In the example of , the focus Z autofocus range is represented by range SR-3A. Fig. 6A and 6B As described above, as part of the autofocus process, an image stack of the workpiece surface WPS1 can be captured within the focal point Z autofocus range using the optical assembly portion 505. An autofocus height can be determined for each of at least three locations on the workpiece surface WPS1 based on at least three corresponding regions of interest of the image stack, as described above with respect to Fig. 6A and 6B Described.

[0170] like Fig.8D As shown, the adjustment mechanism 520 can be controlled based at least in part on the autofocus height at at least three surface locations to: rotate the optical component portion 505 relative to the workpiece surface WPS1 to nominally align the optical axis OA of the optical component portion 505 with the surface normal SN of the workpiece surface WPS1; and adjust the distance between the optical component portion 505 and the workpiece surface WPS1. In various embodiments, when controlling the autofocus height at at least three surface locations, the adjustment mechanism 520 can be controlled to: rotate the optical component portion 505 relative to the workpiece surface WPS1 to nominally align the optical axis OA of the optical component portion 505 with the surface normal SN of the workpiece surface WPS1; and adjust the distance between the optical component portion 505 and the workpiece surface WPS1. Fig.8D Before the adjustment mechanism 520 is used, the determined autofocus heights of the at least three surface positions may be used to calculate or otherwise determine a surface normal SN of the workpiece surface WPS1 and / or corresponding adjustment information. The adjustment mechanism 520 may then be controlled (e.g., using the adjustment information and / or the surface normal calculated / determined based on the autofocus heights) to adjust the surface normal SN of the workpiece surface WPS1 to the desired surface. Figure 8C The position and orientation shown rotates or otherwise moves the optical component portion 505 in the Fig.8DThe position and orientation shown, for which the optical axis OA is shown as nominally coinciding with the surface normal SN. In addition, the adjustment mechanism 520 can be used to adjust the distance between the optical component portion 505 and the workpiece surface WPS1. Fig.8D As shown, the adjustment results in a distance D-8D (eg, along the direction of the optical axis OA and / or the corresponding Z direction) between the optical component portion 505 and the workpiece surface WPS1. L direction measurement). As mentioned above Figure 3A and 3B As described, in various embodiments, distance D-8D can correspond to a workpiece surface WPS1 that is nominally at or near: the middle of range SR-3B (e.g., a range for PFF or other relative operations to be performed on the workspace surface); and / or a working distance of an objective lens of optical assembly portion 505; and / or a best focus position, etc. Once at Fig.8D With the orientation and position shown, it is possible to perform defining operations on the workpiece surface WPS1.

[0171] As an example of a defined operation, a measurement operation using the optical assembly portion 505 may be performed on the workpiece surface WPS1. As part of such an operation or otherwise, a PFF operation (e.g., for determining a surface profile of the workpiece surface WPS1) may be performed. As part of the PFF operation, the optical assembly portion 505 may be used to perform a measurement operation on the workpiece surface WPS1. Fig.8D 3B) (e.g., and the image stack corresponds to scan range SR-3B). As another type of defined operation that can be performed on workpiece surface WPS1, a machining operation (e.g., drilling) can be performed, for which it may be desirable that the machining axis (e.g., drilling axis) of the machining operation coincide with (e.g., is coaxial with or parallel to, etc.) the optical axis OA of the optical assembly portion 505, and is therefore also nominally perpendicular to the workpiece surface SRF1.

[0172] Fig. 9 900 is a flow chart of a method for aligning an optical axis perpendicular to a surface using multi-point autofocus according to one aspect of the present disclosure. In block 901, the method operates a metrology system including an optical assembly portion (205, 305, 405, 505). The optical assembly portion includes: a variable focus (VFL) lens; a light source; and an objective lens, the objective lens inputting image light caused by a surface of a workpiece illuminated by the light source, and transmitting the image light along an imaging light path through the VFL lens. The objective lens defines an optical axis of the optical assembly portion extending at least between the objective lens and the workpiece surface. The optical assembly component also includes a camera that receives imaging light transmitted by the VFL lens along the imaging light path and provides an image of the workpiece surface.

[0173] In block 903, the method moves the optical assembly portion to position the workpiece surface to be measured within a focal point Z autofocus range of the optical assembly portion.

[0174] In block 905 , the method captures an image stack of a workpiece surface using an optical assembly portion within a focal point Z autofocus range.

[0175] In block 907, the method calculates auto-focus heights for at least three locations of the workpiece surface based on at least three corresponding regions of interest (ROIs) of the image stack. In various embodiments, a surface normal and corresponding adjustment information for the workpiece surface may be determined based at least in part on the auto-focus heights at the three locations.

[0176] In block 909, the method controls an adjustment mechanism based at least in part on the autofocus heights at at least three locations to: rotate the optical assembly portion relative to the workpiece surface to nominally align the optical assembly portion with a surface normal of the workpiece surface; and adjust a distance between the optical assembly portion and the workpiece surface.

[0177] In block 911 , the method performs a defined operation on the workpiece surface that is now nominally perpendicular to the optical axis.

[0178] Various defined operations are performable, wherein these operations can all take advantage of the fact that a metrology system according to various embodiments can quickly and / or accurately align an optical axis of an optical component portion to be nominally perpendicular to a workpiece surface on which it is to be operated.

[0179] For example, after performing the limiting operation of frame 911, the process of frames 903 to 911 can be repeated for another portion of the workpiece surface and / or another workpiece surface of the workpiece (for example, for a workpiece including a turbine blade, the process can be repeated for different portions, such as along the curve of the turbine blade, etc.).

[0180] As another example, a non-optical operation, such as a machining (eg, drilling) operation, may be performed on a workpiece surface where the machining operation axis coincides with an optical axis of an optical component portion oriented nominally perpendicular to the workpiece surface.

[0181] As other examples, various optical operations may be performed, such as an extended depth of field (EDOF) operation or a point self focus (PFF) operation. Some details of the EDOF operation and the PFF operation may be found, for example, in U.S. Patent Publication 2020 / 0195836, the entire contents of which are incorporated herein by reference. In short, in an EDOF operation, an optical assembly portion (205, 305, 405, 505) including a VFL (TAG) lens may be operated to expose a preliminary image using an EDOF exposure sequence that defines a plurality of discrete image exposure increments that are acquired at corresponding discrete focus positions FP corresponding to corresponding phases of periodically modulated focus positions. The preliminary image is processed to determine or output an EDOF image having a greater depth of field than the VFL (TAG) lens imaging system at a single focus position (e.g., 10-20 times or more in various embodiments), wherein the EDOF image is substantially focused throughout the greater depth of field. In various embodiments, an EDOF image may be provided at a high rate, suitable for display in near real time. For example, the EDOF image exposure sequence may be configured to acquire a preliminary image in less than 500 milliseconds, or less than 250 milliseconds, or less than 100 milliseconds, or less than 50 milliseconds.

[0182] Briefly, in a PFF operation, an optical assembly portion (205, 305, 405, 505) including a VFL (TAG) lens may be operated to expose a stack of images (image stack) using a PFF exposure sequence defining a plurality of discrete image exposure increments acquired at respective discrete focus positions FP corresponding to respective phases of a periodically modulated focus position. The image stack is processed to determine or output a ZP height coordinate map (e.g., a point cloud) that quantitatively indicates a set of 3-dimensional surface coordinates corresponding to a surface shape of a workpiece.

[0183] In various embodiments, when a defined operation performed on a workpiece surface involves movement in the direction of the optical axis OA, it will be appreciated that including a VFL lens (e.g., VFL lens 220, 370, etc.) can have various advantages. For example, as described above, when a VFL lens (e.g., a TAG lens) is included, in some embodiments, modulation of the focal position of the VFL lens can be achieved without requiring physical movement of the component in the direction of the optical axis OA (e.g., can allow such operations to be performed more quickly and repeatably and without the risk of collision, such as potential collision of otherwise moving components with the workpiece surface, structure and / or other components, etc.). In some embodiments, when the optical assembly is partially tilted (e.g., relative to the Z axis of the machine coordinate system, such as Figure 2B , 3B, 5C and 8D), these aspects may be particularly advantageous. In general, in embodiments that do not include a VFL lens and / or require movement along the optical axis beyond the modulation limit of the VFL lens, various more complex movement sequences may be required.

[0184] For example, about Figure 2B In the configuration of FIG. 2 , if an image stack is to be acquired along a constant image stack acquisition axis ISAA (e.g., as part of a multi-point autofocus or PFF operation) without using a VFL lens, this may require various repositioning movements for each image. More specifically, in order to properly align the optical assembly portion 205 along the image stack acquisition axis ISAA relative to the workpiece surface WPS1, for each image acquisition position, adjustments may need to be made along the Z axis of the machine coordinate system (e.g., using the motor 294) as well as adjustments along the Y and / or X axes of the machine coordinate system (e.g., provided by the movable stage 210 that moves the workpiece). Alternatively, in some embodiments, even in situations such as Figure 2B In the orientation shown in , it is also acceptable to provide image acquisition position / movement only along the Z axis of the machine coordinate system (e.g., provided by motor 294). Figure 2B In the orientation shown, such movement only along the Z-axis direction of the machine coordinate system will not maintain the optical axis OA of the optical assembly portion 205 along the constant image stack acquisition axis ISAA so as to capture each image in the image stack, but the captured image stack may have a sufficiently large field of view that one or more desired regions of interest may still be included in all images of the image stack, just with a relative position shift in each image. With appropriate processing, the desired regions of interest can be determined / tracked and used for desired operations (e.g., multi-point autofocus operations, PFF operations, etc. that can be used according to the methods described herein). It should be understood that the inclusion and use of a VFL lens (e.g., VFL lens 270) can avoid the need for such processing and additional movement (i.e., because modulation of the VFL lens can enable image stacks to be captured along the constant image stack acquisition axis ISAA in a relatively fast and repeatable manner without the need for physical movement of other components and associated processing).

[0185] As another example, in Fig.8DIn embodiments where a VFL lens 370 is not used / included, in order to capture an image stack along the image stack acquisition axis ISAA, movement along the X, Y, and / or Z axis directions of the machine coordinate system (e.g., provided by the X, Y, and Z axis slide mechanisms 525, 526, and 527) may be required for each image acquisition position. As described above, when a VFL lens 370 is included and used, such movement may not be required (i.e., because modulation of the VFL lens 370 enables images of the image stack to be acquired corresponding to different focus positions along a constant image stack acquisition axis ISAA without requiring physical movement of other components).

[0186] As described above, in various embodiments, the adjustment mechanism is controlled to move the optical assembly portion to position the workpiece surface within the focal Z autofocus range of the optical assembly portion. In embodiments that include a VFL lens and are used for autofocus scanning (e.g., no movement of other components is used for autofocus scanning), the focal Z autofocus range can be primarily determined by / related to the range of operation of the VFL lens (e.g., range Refp). For example, for certain TAG lenses, in some embodiments, this can correspond to a range of approximately 10 DOF (depth of field) of the optical system (e.g., so it can be positioned within the 10 DOF of the optical system). As described above, in various embodiments that do not use / include a VFL lens (and / or in the case where the system provides movement to increase the scanning range beyond / in addition to the range provided by the operation of the VFL lens), the focal Z autofocus range can be determined by / correspond to other aspects of the system (e.g., related to the range of movement of various components, such as the range of movement of the motor 294, and / or for collision avoidance, etc.).

[0187] As described above, in various embodiments, a multi-point autofocus image stack can be acquired relatively quickly and can include a relatively small number of images (e.g., 5-10 images). In various embodiments, it is desirable to move the optical component portion to position the workpiece surface within the focus Z autofocus range of the optical component portion so that the multi-point autofocus image stack includes images on both sides of the focus Z position of each portion of the workpiece surface. In some embodiments, this can correspond to having at least a certain number of DOF (e.g., 1 or 2 DOF) on either side of the focus Z position of each portion of the workpiece surface in the field of view of the optical component portion. As described above, these aspects may be advantageous in determining a peak value of corresponding focus curve data. More specifically, as described above, determining an autofocus height of a workpiece surface position may include determining focus curve data of a position / corresponding region of interest based at least in part on an analysis of an image of the image stack, wherein the focus curve data of the position / region of interest indicates a corresponding autofocus height, which may correspond to a peak value of the focus curve data, for example. By acquiring images corresponding to sufficient focus curve data on either side of the peak value, the peak value may be determined with greater / sufficient / desirable precision and / or accuracy, etc.

[0188] It should be understood that such principles and descriptions may also apply to other processes described herein. For example, as noted above in various embodiments, after determining / calculating the surface normal, a motion controller may be used to rotate / adjust the orientation of the optical component portion and adjust the distance between the optical component portion and the workpiece surface. In various embodiments, the distance to which the optical component portion is adjusted from the workpiece surface may be based at least in part on principles such as those described above. For example, it may be desirable that the distance causes the workpiece surface to be located at a desired position within the system scan range (e.g., corresponding to a desired position within the PFF image stack scan range, such that there is a desired number of images corresponding to the focus data on either side of each portion of the workpiece surface, and / or based on certain desired performance characteristics of the portion of the scan range, etc.).

[0189] Although preferred embodiments of the present disclosure have been shown and described, based on the present disclosure, those skilled in the art will appreciate that many variations of the illustrated and described arrangements of features and sequences of operations. Various alternatives may be used to implement the principles disclosed herein. In addition, the various embodiments described above may be combined to provide further embodiments.

Claims

1. A metering system comprising: The optical component part comprises: light source; an objective lens that inputs image light generated by a workpiece surface illuminated by the light source and transmits the image light along an imaging light path, wherein the objective lens defines an optical axis of the optical assembly portion, the optical axis extending at least between the objective lens and the workpiece surface; and a camera that receives imaging light transmitted along the imaging light path and provides an image of the workpiece surface; an adjustment mechanism configured to change the distance between the optical assembly portion and the workpiece surface and to rotate the optical assembly portion relative to the workpiece surface to change the angular orientation of the optical axis of the optical assembly portion relative to the workpiece surface; one or more processors; and a memory coupled to the one or more processors and storing program instructions that, when executed by the one or more processors, cause the one or more processors to at least: Controlling the adjustment mechanism to move the optical component part to position the first workpiece surface of the workpiece within the focus Z autofocus range of the optical component part; capturing, using the optical assembly portion, a first image stack of the first workpiece surface within a focal point Z autofocus range, wherein the first image stack includes a plurality of images of the first workpiece surface and each image of the first image stack corresponds to a different autofocus height; determining auto-focus heights for at least three locations of the first workpiece surface based on at least three corresponding regions of interest of the first image stack; Based at least in part on the autofocus heights at the at least three positions, the adjustment mechanism is controlled to: rotating the optical assembly portion relative to the first workpiece surface to nominally align an optical axis of the optical assembly portion with a surface normal of the first workpiece surface; and adjusting the distance between the optical component portion and the first workpiece surface; performing a first operation on the first workpiece surface, wherein the first operation comprises at least one of a measuring operation, a point focus (PFF) operation, a machining operation, or capturing one or more images of the first workpiece surface; controlling the adjustment mechanism to move the optical assembly portion so as to position the second workpiece surface of the workpiece within a focal point Z autofocus range of the optical assembly portion; capturing, using the optical assembly, a second image stack of the second workpiece surface in part, wherein the second image stack includes a plurality of images of the second workpiece surface, and each image of the second image stack corresponds to a different autofocus height; determining auto-focus heights for at least three locations on the second workpiece surface based on at least three corresponding regions of interest of the second image stack; The adjustment mechanism is controlled based at least in part on the autofocus heights at the at least three positions to: rotating the optical component portion relative to the second workpiece surface to nominally align an optical axis of the optical component portion with a surface normal of the second workpiece surface; and adjusting a distance between the optical assembly portion and the second workpiece surface; and A second operation is performed on the second workpiece surface, wherein the second operation includes at least one of a measuring operation, a point self focus (PFF) operation, a machining operation, or capturing one or more images of the second workpiece surface.

2. The metrology system of claim 1 , wherein the optical component portion further comprises a variable focal length (VFL) lens included in an imaging light path, and wherein the objective lens transmits image light through the VFL lens along the imaging light path and the camera receives the imaging light transmitted by the VFL lens along the imaging light path.

3. The metrology system of claim 2, wherein the VFL lens is a tunable acoustic gradient (TAG) lens configured to non-mechanically change the focal length, and to this end control the periodically modulated focus position of the optical component portion by periodically modulating the optical focal length of the TAG lens, and is used to capture images of the first and second image stacks. 4 . The metrology system of claim 2 , wherein a first operation performed on the first workpiece surface comprises capturing one or more images of the first workpiece surface using the VFL lens.

5. The metrology system of claim 2 , wherein a first operation performed on the first workpiece surface comprises capturing an image stack with the VFL lens while an optical axis of the optical assembly portion is nominally aligned with a surface normal of the first workpiece surface, wherein the image stack comprises a plurality of images of the first workpiece surface and each image of the image stack corresponds to a different focus position of the optical assembly portion along the direction of the optical axis.

6. The metering system according to claim 2, wherein: The periodically modulated focus position of the optical component part is controlled by periodically modulating the optical focal length of the VFL lens, and the images of the first image stack are each captured at a different phase timing of the periodic modulation so that each corresponds to a different autofocus height.

7. The metrology system of claim 1 , wherein determining auto-focus heights for at least three locations of the first workpiece surface comprises determining focus curve data for each region of interest based at least in part on an analysis of images of the first image stack, wherein for each of the at least three locations, a peak of the focus curve data for the corresponding region of interest indicates a corresponding auto-focus height.

8. The metering system of claim 1 , wherein the program instructions, when executed by the one or more processors, further cause the one or more processors to: determining a surface normal of a first workpiece surface based at least in part on the auto-focus heights at at least three locations; and Adjustment information is determined to control an adjustment mechanism to rotate the optical component portion based at least in part on the determined surface normal.

9. The metrology system of claim 1, wherein the first operation comprises a measurement operation for determining a size of a feature of a first workpiece surface.

10. The metrology system of claim 1, wherein the first operation comprises a point focus (PFF) operation comprising: acquiring an image stack comprising a plurality of images, each image corresponding to a focus position of a portion of the optical assembly along an imaging optical axis coinciding with the optical axis, and Focus curve data is determined based at least in part on an analysis of images of the image stack, wherein the focus curve data indicates 3-dimensional positions of a plurality of surface points on the first workpiece surface.

11. The metrology system of claim 1 , wherein the first operation comprises a machining operation performed on a first workpiece surface, wherein a machining axis of the machining operation is at least one of: nominally coincident with or nominally parallel to an optical axis of the optical component portion.

12. The metrology system according to claim 1, wherein the adjustment mechanism comprises a rotation mechanism and a Z-axis movement mechanism, wherein the Z-axis movement mechanism is coupled to move the optical component portion along the Z-axis direction, and the rotation mechanism is coupled between the Z-axis movement mechanism and the optical component portion and is configured to rotate the optical component portion relative to the first workpiece surface to change the angular orientation of the optical axis of the optical component portion relative to the first workpiece surface.

13. The metrology system of claim 12, wherein the metrology system is embodied in a precision machine vision inspection system, and the adjustment mechanism comprises a rotary table that includes the rotation mechanism and is coupled between the Z-axis movement mechanism and the optical assembly portion.

14. The metrology system of claim 1, wherein the metrology system is embodied in a coordinate measurement machine system and the adjustment mechanism comprises: an x-axis sliding mechanism, a y-axis sliding mechanism and a z-axis sliding mechanism, which are configured to move the optical assembly portion in mutually orthogonal x-axis, y-axis and z-axis directions, respectively, within a machine coordinate system, and A rotation mechanism is configured to rotate the optical assembly portion relative to the first workpiece surface.

15. The metrology system of claim 1, wherein the metrology system is embodied in a robotic system and the adjustment mechanism comprises a robotic arm having at least three degrees of freedom for moving the optical assembly portion.

16. A method for operating a metrology system comprising an optical assembly portion, wherein the optical assembly portion comprises: light source; an objective lens that inputs image light generated by the workpiece surface illuminated by the light source and transmits the image light along an imaging light path, wherein the objective lens defines an optical axis of the optical assembly portion, the optical axis extending at least between the objective lens and the workpiece surface; and a camera that receives imaging light transmitted along the imaging light path and provides an image of the workpiece surface; The method comprises: moving the optical assembly portion to position a first workpiece surface of the workpiece within a focal point Z autofocus range of the optical assembly portion; capturing, using the optical assembly portion, a first image stack of the first workpiece surface within a focal point Z autofocus range, wherein the first image stack includes a plurality of images of the first workpiece surface and each image of the first image stack corresponds to a different autofocus height; determining auto-focus heights for at least three locations on the workpiece surface based on at least three corresponding regions of interest of the image stack; determining, based at least in part on the autofocus heights at the at least three locations, adjustment information for rotating the optical assembly portion relative to the first workpiece surface to nominally align an optical axis of the optical assembly portion with a surface normal of the first workpiece surface and for adjusting a distance of the optical assembly portion from the first workpiece surface; Rotating the optical component portion using the adjustment information to nominally align an optical axis of the optical component portion with a surface normal of the first workpiece surface and to adjust a distance of the optical component portion from the first workpiece surface; performing a first operation on a first workpiece surface, wherein the first operation comprises at least one of a measuring operation, a point focus (PFF) operation, a machining operation, or capturing one or more images of the first workpiece surface; moving the optical assembly portion to position a second workpiece surface of the workpiece within a focal point Z autofocus range of the optical assembly portion; capturing, using the optical assembly, a second image stack of the second workpiece surface in part, wherein the second image stack includes a plurality of images of the second workpiece surface, and each image of the second image stack corresponds to a different autofocus height; determining auto-focus heights for at least three locations on the second workpiece surface based on at least three corresponding regions of interest of the second image stack; determining, based at least in part on the autofocus heights at the at least three locations, adjustment information for rotating the optical assembly portion relative to a second workpiece surface to nominally align an optical axis of the optical assembly portion with a surface normal of the second workpiece surface and for adjusting a distance between the optical assembly portion and the second workpiece surface; utilizing the adjustment information to rotate the optical assembly portion to nominally align an optical axis of the optical assembly portion with a surface normal of a second workpiece surface and to adjust a distance between the optical assembly portion and the second workpiece surface; and A second operation is performed on the second workpiece surface, wherein the second operation includes at least one of a measuring operation, a point self focus (PFF) operation, a machining operation, or capturing one or more images of the second workpiece surface.

17. The method of claim 16, wherein: The optical assembly portion further includes a tunable acoustic gradient (TAG) lens included in an imaging optical path, and wherein the objective lens transmits image light through the TAG lens along the imaging optical path, and the camera receives the imaging light transmitted by the TAG lens along the imaging optical path; and The method also includes periodically modulating the optical power of the TAG lens to provide a periodically modulated focus position of the optical component portion for capturing images of the first and second image stacks.

18. The method of claim 17, wherein the first operation performed on the first workpiece surface comprises capturing one or more images using the TAG lens.

19. The method of claim 16, further comprising determining a surface normal of the first workpiece surface based at least in part on the auto-focus heights at at least three locations, wherein the adjustment information is determined based at least in part on the determined surface normal.

20. The method of claim 16, wherein the first operation comprises a measurement operation for determining a size of a feature of a first workpiece surface.

21. The method of claim 16, wherein the first operation comprises a point focus (PFF) operation comprising: acquiring an image stack comprising a plurality of images, each image corresponding to a focus position of a portion of the optical assembly along an imaging optical axis coinciding with the optical axis, and Focus curve data is determined based at least in part on an analysis of images of the image stack, wherein the focus curve data indicates 3-dimensional positions of a plurality of surface points on the first workpiece surface.

22. A metering system comprising: The optical component part comprises: Variable focal length (VFL) lens; light source; an objective lens that inputs image light generated by a workpiece surface illuminated by the light source and transmits the image light along an imaging light path through a VFL lens, wherein the objective lens defines an optical axis of the optical assembly portion, the optical axis extending at least between the objective lens and the workpiece surface; and A camera that receives imaging light transmitted by the VFL lens along an imaging optical path and provides an image of a workpiece surface; a Z-axis movement mechanism configured to change the distance between the optical assembly portion and the workpiece surface; a rotation mechanism configured to rotate the optical assembly portion relative to the workpiece surface to change the angular orientation of an optical axis of the optical assembly portion relative to the workpiece surface; one or more processors; and a memory coupled to the one or more processors and storing program instructions that, when executed by the one or more processors, cause the one or more processors to at least: Controlling at least one of the Z-axis moving mechanism or the rotating mechanism to move the optical assembly portion to position a first workpiece surface of the workpiece within a focal point Z autofocus range of the optical assembly portion; capturing, using the optical assembly portion, a first image stack of the first workpiece surface within a focal point Z autofocus range, wherein the first image stack includes a plurality of images of the first workpiece surface and each image of the first image stack corresponds to a different autofocus height; determining auto-focus heights for at least three locations of the first workpiece surface based on at least three corresponding regions of interest of the first image stack; Based at least in part on the autofocus heights at the at least three locations, controlling a rotation mechanism to rotate the optical assembly portion relative to a first workpiece surface to nominally align an optical axis of the optical assembly portion with a surface normal of the first workpiece surface and controlling a Z-axis movement mechanism to adjust a distance of the optical assembly portion from the first workpiece surface; performing a first operation on the first workpiece surface, wherein the first operation comprises at least one of a measuring operation, a point focus (PFF) operation, a machining operation, or capturing one or more images of the first workpiece surface; controlling at least one of the Z-axis moving mechanism or the rotating mechanism to move the optical assembly portion so as to position the second workpiece surface of the workpiece within a focal point Z autofocus range of the optical assembly portion; capturing, using the optical assembly, a second image stack of the second workpiece surface in part, wherein the second image stack includes a plurality of images of the second workpiece surface, and each image of the second image stack corresponds to a different autofocus height; determining auto-focus heights for at least three locations on the second workpiece surface based on at least three corresponding regions of interest of the second image stack; Based at least in part on the autofocus heights at the at least three locations, controlling a rotation mechanism to rotate the optical assembly portion relative to a second workpiece surface to nominally align an optical axis of the optical assembly portion with a surface normal of the second workpiece surface, and controlling a Z-axis movement mechanism to adjust a distance between the optical assembly portion and the second workpiece surface; and A second operation is performed on the second workpiece surface, wherein the second operation includes at least one of a measuring operation, a point self focus (PFF) operation, a machining operation, or capturing one or more images of the second workpiece surface.

23. The metrology system of claim 22, wherein the VFL lens is a tunable acoustic gradient (TAG) lens, wherein a periodically modulated focus position of the optical component portion is controlled by periodically modulating the optical focal length of the TAG lens, and is used to capture images of the first and second image stacks.

24. A system comprising: The optical component part comprises: light source; an objective lens that inputs image light generated by a workpiece surface illuminated by the light source and transmits the image light along an imaging light path, wherein the objective lens defines an optical axis of the optical assembly portion, the optical axis extending at least between the objective lens and the workpiece surface; and a camera that receives imaging light transmitted along the imaging light path and provides an image of the workpiece surface; an adjustment mechanism configured to change the distance between the optical assembly portion and the workpiece surface and to rotate the optical assembly portion relative to the workpiece surface to change the angular orientation of the optical axis of the optical assembly portion relative to the workpiece surface; one or more processors; and a memory coupled to the one or more processors and storing program instructions that, when executed by the one or more processors, cause the one or more processors to at least: Controlling the adjustment mechanism to move the optical component part to position the workpiece surface within the focus Z automatic focusing range of the optical component part; capturing, using the optical assembly portion, a first image stack of the workpiece surface within a focal point Z autofocus range, wherein the first image stack includes a plurality of images of the workpiece surface and each image of the first image stack corresponds to a different autofocus height; determining auto-focus heights for at least three locations on the workpiece surface based on at least three corresponding regions of interest of the first image stack; Based at least in part on the autofocus heights at the at least three positions, the adjustment mechanism is controlled to: rotating the optical assembly portion relative to the workpiece surface to nominally align an optical axis of the optical assembly portion with a surface normal to the workpiece surface; and adjusting the distance between the optical component portion and the workpiece surface; and An operation is performed on the workpiece surface, wherein the operation includes capturing a second image stack when an optical axis of the optical component portion is nominally aligned with a surface normal of the workpiece surface, wherein the second image stack includes a plurality of images of the workpiece surface, and each image of the second image stack corresponds to a different focus position of the optical component portion along the direction of the optical axis.

25. The system of claim 24, wherein: The operation performed on the workpiece surface includes capturing the second image stack using a variable focal length (VFL) lens, wherein the VFL lens is part of the optical component portion and is included in the imaging light path, and the objective lens transmits image light through the VFL lens along the imaging light path and the camera receives the imaging light transmitted by the VFL lens along the imaging light path.

26. A method for operating a system comprising an optical assembly portion, wherein the optical assembly portion comprises: light source; an objective lens that inputs image light generated by the workpiece surface illuminated by the light source and transmits the image light along an imaging light path, wherein the objective lens defines an optical axis of the optical assembly portion, the optical axis extending at least between the objective lens and the workpiece surface; and a camera that receives imaging light transmitted along the imaging light path and provides an image of the workpiece surface; The method comprises: moving the optical assembly part to position the workpiece surface within a focal point Z autofocus range of the optical assembly part; capturing, using the optical assembly portion, a first image stack of the workpiece surface within a focal point Z autofocus range, wherein the first image stack includes a plurality of images of the workpiece surface and each image of the first image stack corresponds to a different autofocus height; determining auto-focus heights for at least three locations on the workpiece surface based on at least three corresponding regions of interest of the first image stack; determining, based at least in part on the autofocus heights at the at least three locations, adjustment information for rotating the optical assembly portion relative to the workpiece surface to nominally align an optical axis of the optical assembly portion with a surface normal of the workpiece surface and for adjusting a distance between the optical assembly portion and the workpiece surface; utilizing the adjustment information to rotate the optical assembly portion to nominally align an optical axis of the optical assembly portion with a surface normal of a workpiece surface and to adjust a distance between the optical assembly portion and the workpiece surface; and An operation is performed on the workpiece surface, wherein the operation includes capturing a second image stack when an optical axis of the optical component portion is nominally aligned with a surface normal of the workpiece surface, wherein the second image stack includes a plurality of images of the workpiece surface, and each image of the second image stack corresponds to a different focus position of the optical component portion along the direction of the optical axis.

27. The method according to claim 26, wherein: The operation performed on the workpiece surface includes capturing the second image stack using a variable focal length (VFL) lens, wherein the VFL lens is part of the optical component portion and is included in the imaging light path, and the objective lens transmits image light through the VFL lens along the imaging light path and the camera receives the imaging light transmitted by the VFL lens along the imaging light path.

Images