Patent Publication Number: US-2022228855-A1

Title: Method, system, and apparatus for optical measurement

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application Ser. No. 63/139,848, filed on Jan. 21, 2021, the contents of which are hereby incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     A method, system and apparatus are provided in accordance with an example embodiment for optically measuring workpiece features, and more particularly, to optically measure internal surfaces of round bores and countersinks. 
     BACKGROUND 
     Manufacturing, and particularly precision manufacturing required for industries such as the aerospace industry, requires accurate machining of workpieces. Machining of workpieces involves many variables that affect the accuracy and precision of the machining operation. Reducing the variability of the variables involved in machining improves the quality of the machining operation while enhancing efficiency. One aspect of machining that has inherent variability is tool wear. As a machining tool wears, the capabilities of the tool are diminished. Inspecting machine tools for wear can be an expensive task both in terms of time (and machine downtime) and effort. Inspection of workpieces produced by wearing machine tools can also be expensive, and defects induced by worn tools may not be realized until the defect is substantial, risking scrapping of a machined part. While machining tools may be replaced based on a number of uses or duration of use, such replacement may lead to replacement of machine tools that have substantial tool life remaining, leading to unnecessary replacement at substantial expense. It is desirable to understand the life of machining tools based on their performance, while not overburdening the machining process with inspections, machining validation, and unnecessary tool replacement. 
     BRIEF SUMMARY 
     A method, system and apparatus are provided for optically measuring workpiece features, and more particularly, to optically measure internal surfaces of round bores and countersinks. Embodiments provide a probe including a probe base and a probe tip; a countersink camera having a countersink camera lens; a bore camera having a bore camera lens; and a laser source configured to generate a first laser cone and a second laser cone, where the probe tip defines a first reflective surface and a second reflective surface, where the first reflective surface is configured to receive the first laser cone and form a bore laser cone, where the second reflective surface is configured to receive the second laser cone and form a countersink laser cone, where the bore camera lens receives the bore laser cone reflected from a bore in response to the probe tip being received within the bore, and where the countersink camera lens is configured to receive the countersink laser cone reflected from a countersink in response to the probe tip being received within the countersink. 
     The laser source of an example embodiment includes a diffractive optical element to receive a laser beam and generate the first laser cone and the second laser cone. Embodiments include a forward-facing camera having a forward-facing camera lens; and a light source, where the forward-facing camera lens is configured to receive, through an aperture defined in the probe tip, light from the light source reflected from a workpiece. The first laser cone includes a first opening angle and the second laser cone includes a second opening angle, different from the first opening angle. According to some embodiments, the first reflective surface is positioned in the probe tip to receive the first laser cone at the first opening angle and the second reflective surface is positioned in the probe tip to receive the second laser cone at the second opening angle. 
     According to an example embodiment, the bore camera lens receives the bore laser cone reflected from a bore to a third reflective surface and to the bore camera lens in response to the probe tip being received within the bore. The countersink camera lens of some embodiments is configured to receive the countersink laser cone reflected from a countersink to a countersink beam reflector and to the countersink camera lens in response to the probe tip being received within the countersink. Embodiments include a controller configured to measure a surface of the bore in response to the bore laser cone received at the bore camera lens. The controller is configured to measure an exit burr from the bore in response to the probe advancing through an exit surface of the bore. The controller of some embodiments is configured to determine one or more dimensions of the bore and an exit burr in response to the bore laser cone received at the bore camera lens. The controller of some embodiments is configured to determine one or more dimensions of the countersink in response to the countersink laser cone received at the countersink camera lens. The probe tip of an example embodiment defines a first opening and a second opening, where the first reflective surface is disposed within the first opening and the second reflective surface is disposed within the second opening. 
     Embodiments provided herein include a system having a controller and a probe including: a probe base and a probe tip, the probe tip having a first reflective surface and a second reflective surface; a countersink camera within the probe tip having a countersink camera lens; a bore camera within the probe tip having a bore camera lens; and a laser source within the probe tip configured to generate a first laser cone and a second laser cone, where the first reflective surface is configured to receive the first laser cone and form a bore laser cone, where the second reflective surface is configured to receive the second laser cone and form a countersink laser cone, where dimensions of a bore are measured by the controller in response to the probe tip being received within the bore and the camera lens receiving the bore laser cone, where dimensions of the countersink are measured by the controller in response to the probe tip being received within the countersink and the countersink camera lens receiving the countersink laser cone. 
     According to an example embodiment, the first laser cone is received at the first reflective surface at a first opening angle and the second laser cone is received at the second reflective surface at a second opening angle, different from the first opening angle. The probe of some embodiments includes a third reflective surface, where the bore laser cone is received at the bore camera lens from the third reflective surface in response to the first laser cone being reflected from the first reflective surface to form the bore laser cone and the bore laser cone being reflected from the bore to the third reflective surface. The probe of some embodiments includes a countersink beam reflector, where the countersink laser cone is received at the countersink camera lens from the countersink beam reflector in response to the second laser cone being reflected from the second reflective surface to form the countersink laser cone and the countersink laser cone being reflected from the countersink to the countersink beam reflector. The controller of some embodiments is configured to determine one or more dimensions of the bore and one or more exit burrs in response to the probe advancing through the bore based on the bore laser cone received at the bore camera lens. The controller of some embodiments is configured to determine one or more dimensions of the countersink in response to the probe advancing through the countersink based on the countersink laser cone received at the countersink camera lens. 
     Embodiments provided herein include a method for measuring dimensions of a bore and countersink including: advancing a probe through a bore and a countersink; and measuring dimensions of the bore and the countersink based on a bore laser cone received at a bore camera lens and a countersink laser cone received at a countersink camera lens, where the bore laser cone is received at the bore camera lens in response to a first laser cone reflecting from a first reflective surface of the probe to form the bore laser cone and the bore laser cone being reflected from a surface of the bore to a third reflective surface of the probe and to the bore camera lens, and where the countersink laser cone is received at the countersink camera lens in response to a second laser cone reflecting from a second reflective surface of the probe to form the countersink laser cone, the countersink laser cone being reflected from a surface of the countersink to a countersink beam reflector and to the countersink camera lens. 
     According to some embodiments, methods include: generating from a laser source and a diffractive optical element, a first laser cone at a first opening angle, where the first laser cone is reflected at the first reflective surface to form the bore laser cone; and generating from the laser source and the diffractive optical element a second laser cone at a second opening angle, where the second laser cone is reflected at the second reflective surface to form the countersink laser cone, and where the second opening angle is different from the first opening angle. Methods of an example embodiment include identifying the bore in a workpiece based on light reflected from the workpiece to a forward-facing camera lens of the probe through an aperture defined in a probe tip of the probe. Measuring dimension of the bore and the countersink are performed, in some embodiments, based on a calibration table established for the probe. Methods of some embodiments include measuring dimensions of a burr on an exit surface of the bore in response to the probe advancing past the exit surface of the bore. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Having thus described certain example embodiments of the present disclosure in general terms, reference will hereinafter be made to the accompanying drawings which are not necessarily drawn to scale, and wherein: 
         FIG. 1  is a representation of a probe apparatus attached to an end effector of a robot according to an example embodiment of the present disclosure; 
         FIG. 2  illustrates a probe apparatus including a probe base and probe tip according to an example embodiment of the present disclosure; 
         FIG. 3  illustrates a system including controller configured to control a robot and/or a probe according to an example embodiment of the present disclosure; 
         FIG. 4  illustrates a cross-section view of a probe according to an example embodiment of the present disclosure; 
         FIG. 5  illustrates the bore laser cone and countersink laser cone formed from respective reflective surfaces according to an example embodiment of the present disclosure; 
         FIG. 6  illustrates the axial beam produced by the reflection of at least a portion of the countersink laser cone off of the countersink, collected at the countersink beam reflector, and directed to the countersink camera lens according to an example embodiment of the present disclosure; 
         FIG. 7  illustrates a probe tip entering a countersink and bore and an associated image, according to an example embodiment of the present disclosure; 
         FIG. 8  illustrates an image representing the countersink at a position proximate the bore according to an example embodiment of the present disclosure; 
         FIG. 9  illustrates the probe tip inserted through the workpiece and emerging from a back side of the workpiece according to an example embodiment of the present disclosure; 
         FIG. 10  illustrates the irradiance received at the bore camera lens in image with irradiated pixels with breaks as found in the images of the countersink according to an example embodiment of the present disclosure; 
         FIG. 11  illustrates a section view of the probe tip as it exits the back side of the workpiece and an associated image, according to an example embodiment of the present disclosure; 
         FIG. 12  illustrates a section view the probe tip as the bore laser cone exits the bore on the back side of the workpiece and an associated image, according to an example embodiment of the present disclosure; 
         FIG. 13  illustrates the bore laser cone reflected from the first reflective surface and scattered by the back surface of the workpiece and an associated image, according to an example embodiment of the present disclosure; 
         FIG. 14  illustrates a process of calibrating a probe using reference bores to generate a calibration table according to an example embodiment of the present disclosure; 
         FIG. 15  illustrates using off-axis illumination received in the forward-facing camera lens for insertion alignment of the probe according to an example embodiment of the present disclosure; and 
         FIG. 16  is a flowchart of a process for optically scanning and measuring a bore and countersink according to an example embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all aspects are shown. Indeed, the disclosure may be embodied in many different forms and should not be construed as limited to the aspects set forth herein. Rather, these aspects are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. 
     A method, system, and apparatus product are provided in accordance with an example embodiment described herein for optically measuring workpiece features, and more particularly, to optically measure internal surfaces of round bores and countersinks. Embodiments described herein include a unique capability of providing a means of measuring exit burr height. The modular design of example embodiments integrate low-cost mass-produced miniature components into a compact package requiring only electrical signals from a host interface. The probe described herein provides forward vision capability to support collision avoidance. 
     Automated manufacturing provides enhancements to efficiency and accuracy. However, routine measurement is necessary to ensure accuracy is maintained while tooling and machinery experience wear over time. One area in which accurate and repeatable automated manufacturing requires high precision is in aerospace. Holes drilled in aircraft components may be critical to a sound structure, where exit burrs may prove less than optimal and may be indicative of cutting tool wear or machining speed/force issues. For holes in joints, the number of allowable joint load cycles is known to be related to the exit burr height. In situ exit burr height measurement can reduce or eliminate the cost or need to measure cutting tool life, eliminate or reduce the recurring waste of residual cutting tool life, and eliminate or reduce recurring waste of validation upon cutting. 
     One technique for dealing with burrs is that a part may be manually de-burred, where an assembly may be clamped into a jig, machined/drilled, disassembled, de-burred, reassembled, gap-checked, and fastened. Such a process is both time-consuming and inefficient. Further, such a process is subject to human error. Another method for dealing with burrs may include one-up assembly. For every material stack and hole diameter condition, a non-recurring activity is used to determine a cutting tool&#39;s life in stack up representative coupons with statistical confidence. Once qualified, and during all subsequent recurring cutting operations, the number of holes cut per cutting tool must be counted, and cutting tools disposed of with statistical confidence before the cutting tool could cause excessive exit burr height. To ensure qualification validation, a work piece test coupon may need to be drilled before and/or after drilling the workpiece. This method is also time consuming and inefficient. 
     Embodiments described herein provide for optically measuring workpiece features, and more particularly, to optically measure internal surfaces of round bores and countersinks. Embodiments described herein provide for measurement of exit burr height to confirm exit burrs are within tolerance, thereby confirming cutting tool functionality. Embodiments described herein provide a low-cost method of measurement of machined holes and countersinks without suffering the inefficiencies of previous methods. 
     Embodiments described herein employ a multi-axis robot, such as the robot  10  illustrated in  FIG. 1  configured to engage a probe  20  as an end-effector of the robot. The probe  20  may also be referred to as a bore optical scan sensor. The probe  20  may be a removable and replaceable component that is readily attached and detached to the robot  10 . The robot of example embodiments is configured for the inspection of workpieces using the probe. The robot  10 , together with the controller described further below and the probe  20 , enables positioning and orientation within six degrees of freedom for measurement of a relatively small bore through a work piece. Embodiments enable the measurement of a bore and countersink surface and measurement of exit burr height, which provides the ability to identify tool wear or machining issues. 
     The probe  20  includes a probe tube having at least one laser source, cameras, and a geometry of angled reflectors enabling an integrated modular probe. Further, the use of inexpensive components and without requiring high-precision machining or molding of the probe results in a probe that is highly cost-effective and therefore substantially disposable and replaceable, as needed. Embodiments enable the efficient optical three-dimensional bore surface measurements of a countersink, bore, exit surface, and exit burr height. Accurate measurement of the exit surface enables material stack thickness measurement for identification of the ideal fastener length. 
       FIG. 2  illustrates an enlarged view of the probe  20  including a forward-vision open tip including opening  22 , a modular probe tip  24 , modular probe base  26 , and the interface  28  to a robot tool holder  12 . The interface may include electrical connections between the modular probe base  26  and the robot tool holder  12 , along with a physical connection to mount the probe  20  to the robot. The physical connection may be a threaded connection, a frictional engagement, or the like. The robot tool holder  12  interfaces with the robot  10 , where communication between a controller and the robot tool holder  12  may be wired or optionally wireless communication through a communication interface. 
       FIG. 3  illustrates a system  31  including controller  30  configured to control a robot  10  and/or a probe  20 . The controller  30  includes a computing device  34  that has processing circuitry  36  in communication with a communication interface  42 , a memory  38 , and a user interface  40 . The controller  30  may be in communication with one or both of the robot  10  and the probe  20  as shown. 
     The computing device  34  of controller  30  may be configured in various manners and, as such, may be embodied as a personal computer, a tablet computer, a computer workstation, a mobile computing device such as a smartphone, a server or the like. Regardless of the manner in which the computing device  34  is embodied, the computing device of an example embodiment includes or is otherwise associated with processing circuitry  36 , memory  38 , and optionally a user interface  40  and a communication interface  42  for performing the various functions herein described. The processing circuitry  36  may, for example, be embodied as various means including one or more microprocessors, one or more coprocessors, one or more multi-core processors, one or more controllers, one or more computers, various other processing elements including integrated circuits such as, for example, an ASIC (application specific integrated circuit) or FPGA (field programmable gate array), or some combination thereof. In some example embodiments, the processing circuitry  36  is configured to execute instructions stored in the memory  38  or otherwise accessible to the processing circuitry. These instructions, when executed by the processing circuitry  36 , may cause the computing device  34  and, in turn, the controller  30  to perform one or more of the functionalities described herein. As such, the computing device  34  may comprise an entity capable of performing operations according to an example embodiment of the present disclosure while configured accordingly. Thus, for example, when the processing circuitry  36  is embodied as an ASIC, FPGA or the like, the processing circuitry and, correspondingly, the computing device  34  may comprise specifically configured hardware for conducting one or more operations described herein. Alternatively, as another example, when the processing circuitry  36  is embodied as an executor of instructions, such as may be stored in the memory  38  the instructions may specifically configure the processing circuitry and, in turn, the computing device  34  to perform one or more algorithms and operations described herein. 
     The memory  38  may be a non-transitory memory and include, for example, volatile and/or non-volatile memory. The memory  38  may comprise, for example, a hard disk, random access memory, cache memory, flash memory, an optical disc (e.g., a compact disc read only memory (CD-ROM), digital versatile disc read only memory (DVD-ROM), or the like), circuitry configured to store information, or some combination thereof. In this regard, the memory  38  may comprise any non-transitory computer readable storage medium. The memory  38  may be configured to store information, data, applications, instructions, or the like for enabling the computing device  34  to carry out various functions in accordance with example embodiments of the present disclosure. For example, the memory  38  may be configured to store program instructions for execution by the processing circuitry  36 . 
     The user interface  40  may be in communication with the processing circuitry  36  and the memory  38  to receive user input and/or to provide an audible, visual, mechanical, or other output to a user. As such, the user interface  40  may include, for example, a display for providing an image captured by the probe  20  or measured output from the probe  20  as described further below. Other examples of the user interface  40  include a keyboard, a mouse, a joystick, a microphone and/or other input/output mechanisms. 
     The communication interface  42  may be in communication with the processing circuitry  36  and the memory  38  and may be configured to receive and/or transmit data. The communication interface  42  may include, for example, one or more antennas and supporting hardware and/or software for enabling communications with a wireless communication network. Additionally or alternatively, the communication interface  42  may include the circuitry for interacting with the antenna(s) to cause transmission of signals via the antenna(s) or to handle receipt of signals received via the antenna(s). In some environments, the communication interface  42  may alternatively or also support wired communication. 
       FIG. 4  illustrates a cross-section view of a probe  20  according to embodiments of the present disclosure. As shown, the probe tip  24  extends from the probe base  26  and is supported by support struts  52 . The probe tip  24  includes laser diodes and camera lenses to provide bore surface measurements as described herein. As shown, the probe tip includes a forward-facing camera lens  54  of a forward-facing camera or image capture device with forward vision field of view  56  through an aperture defined in the probe tip. The forward-facing camera lens  54  is used for general alignment and insertion as will be described in greater detail below. The probe tip  24  also includes a laser source  60  including a laser diode  60   a  and diffractive optical element  60   b , where the diffractive optical element  60   b  is configured to receive a laser beam from the laser diode  60   a  and generate two laser cones. The diffractive optical element  60   b  which may also be referred to as a pattern generator or beam shaper is configured to receive the laser light from the laser diode and form the two laser cones. Optionally, two diffractive optical elements may be used whereby a first diffractive optical element forms a first cone and allows a portion of the laser to pass through the first diffractive optical element to a second diffractive optical element that may take at least a portion of the remaining laser light reaching the second diffractive optical element and form the second cone. The one or more diffractive optical elements thereby forms two laser cones having different opening angles as described further below. The first laser cone  63  emitted at a first opening angle  163  from the diffractive optical element forms the bore laser cone  64  which is reflected from a first reflective surface  62  of the probe tip  24  to impinge on a bore as described further below. 
     The probe tip is configured with openings through the body of the probe tip and reflective surfaces in the probe tip which will be shown and described in greater detail below. The second laser cone  67  emitted at a second opening angle  167  from the diffractive optical element, less than the first opening angle  163  of the first laser cone  63 , forms the countersink laser cone  68  that is reflected from a second reflective surface  66  of the probe tip  24  to impinge on a countersink as described further below. The bore laser cone  64  and countersink laser cone  68  are arranged at different angles relative to one another to provide accurate measurements of different aspects of a bore and countersink. The first opening angle  163  of the first laser cone  63  and the second opening angle  167  of the second laser cone  67  are determined based on a position of the laser diode  60   a  and the diffractive optical element  60   b  relative to the first reflective surface  62  and the second reflective surface  66 . The opening angles are established such that the first laser cone  63  is received at the first reflective surface  62  to form the bore laser cone  64  and the second laser cone  67  is received at the second reflective surface  66  to form the countersink laser cone  68 . 
     The probe tip  24  cross-section of  FIG. 4  also includes a bore camera lens  70  of a bore camera or bore image capture device and a countersink camera lens  72  of a countersink camera or countersink image capture device. The bore camera lens  70  is arranged to receive a portion of the bore laser cone  64  reflected from a bore being inspected, while the countersink camera lens  72  is arranged to receive a portion of the countersink laser cone reflected from a countersink of the bore being inspected. As will be described below with respect to  FIG. 6 , the countersink camera lens  72  receives a portion of the countersink laser cone reflected from the countersink of the bore being inspected that is gathered at the countersink beam reflector  74  before being returned to the countersink camera lens  72 . 
     The area within the probe tip  24  through which beams are passing as they are emitted and received by a respective camera lens may be hollow and exposed to the environment of the workpiece during use. However, according to some embodiments, the area within the probe tip may be filled with an optical-grade epoxy that allows the beams from the laser diode  60   a  and diffractive optical element  60   b  to pass through the optical-grade epoxy without diffraction such that the beams are received at the respective camera lenses as if the optical-grade epoxy was not present. Filling the area within the probe tip  24  with optical-grade epoxy improves the robustness of the probe tip  24  such that minor contact of the probe tip with the workpiece (e.g., the bore or the countersink) may not ruin the probe tip  24  or affect the accuracy of the probe  20 . Further, employing optical-grade epoxy in the voids within the probe tip  24  may allow the support struts  52  to be smaller as they are less structurally relied upon to support the probe tip  24 . Reducing the size of the support struts  52  reduces the amount of obstruction to the beams as they are reflected to the camera lenses. 
       FIG. 5  illustrates how the bore laser cone  64  and countersink laser cone  68  emanate from respective reflective surfaces.  FIG. 5  depicts a partial view of the probe tip  24  entering a bore  80  having countersink  82 . The laser source  60  including laser diode  60   a  and diffractive optical element  60   b  produces first laser cone  63  which enters first opening  162  and is reflected from the first reflective surface  62  of first opening  162  forming the bore laser cone  64  that is scattered as the probe tip  24  is not sufficiently inserted into the bore  80  for the bore laser cone  64  to meet an inner surface of the bore  80 . The controller  30  is configured to measure a surface of the bore  80  in response to the bore laser cone  64  received at the bore camera lens  70 . The controller  30  is also configured to measure one or more dimensions of the bore  80  in response to the bore laser cone  64  received at the bore camera lens  70 . The laser diode  60   a  and diffractive optical element  60   b  also produces second laser cone  67  which enters second opening  166  and is reflected from the second reflective surface  66  of second opening  166  to form the countersink laser cone  68 , which impinges on the countersink  82  and is reflected, at least in part, by the countersink  82  forming an axial beam  69  that is received at the countersink beam reflector  74  of  FIG. 4  and collected/reflected to the countersink camera lens  72 . 
     As shown in  FIG. 5 , the first reflective surface  62  defined within first opening  162  is configured to receive the first laser cone  63  and form a bore laser cone  64 . The second reflective surface  66  defined within second opening  166  is configured to receive the second laser cone  67  and form the countersink laser cone  68 . The bore camera lens  70  receives the bore laser cone  64  reflected from a bore in response to the probe tip being received within the bore as will be further illustrated and described with respect to  FIG. 9  below. The countersink camera lens  72  receives the countersink laser cone  68  reflected from a countersink in response to the probe tip  24  being received within the countersink as will be further illustrated and described with respect to  FIGS. 7 and 8  below. 
     The first opening  162  and second opening  166  are openings or cut-outs in the probe tip  24  that allow the first laser cone  63  and the second laser cone  67  to pass through to respective reflective surfaces to form the bore laser cone  64  and the countersink laser cone  68 . The first opening  162  is a one of a first plurality of openings around the probe tip  24  allowing the first laser cone  63  to pass through to first reflective surface  62 . Similarly, the second opening  166  is one of a second plurality of openings disposed around the probe tip  24  allowing the second laser cone  67  to pass through to second reflective surface  66 . The first plurality of openings may include, for example, three cut-outs or openings around the probe tip  24  where each opening is close to 120 degrees, or the first plurality of openings around the probe tip  24  may include four openings with each opening close to 90 degrees. Regardless of the number of openings, a portion of the probe tip may extend between each of the first plurality of openings to provide support for the probe tip  24 . Similarly, the second plurality of openings may include two, three, or four openings about the body of the probe tip with portions of the probe tip  24  extending between each of the openings. The portions of the probe tip  24  extending between the openings may be sized to be a small portion of the circumference of the probe tip  24  to allow the bore laser cone  64  and/or the countersink laser cone  68  to cover as much of the area around the probe tip as possible. As described further below, voids and openings of the probe tip may be filled with an optical-grade epoxy to enhance strength and robustness of the probe tip while enabling the openings to be larger. 
     As the probe tip  24  is inserted into the bore  80  past the countersink  82 , the countersink laser cone  68  impinges upon the countersink from an opening of the countersink at the surface of the workpiece, to the bore  80 . This produces a sequence of images of the countersink that are effectively images of slices of the countersink  82 . Each of these slice images will reveal any surface anomalies including burrs and voids, and from the images, a burr height or void size can be established. 
       FIG. 6  illustrates the axial beam  69  produced by the reflection of at least a portion of the countersink laser cone  68  off of the countersink, collected at the countersink beam reflector  74 , and directed to the countersink camera lens  72 .  FIG. 7  illustrates the image captured by the countersink camera lens  72  based on the reflected countersink laser cone  68  forming an axial beam and being reflected off the countersink beam reflector  74 . The controller  30  is configured to measure the surface of the countersink in response to the countersink laser cone  68  being reflected at the countersink beam reflector  74  and collected at the countersink camera lens  72  to produce image  95  of pixels irradiated by the countersink laser cone  68 . The image  95  produced includes the reflected axial beam  69  as it was reflected into the countersink camera lens  72  irradiating pixels to form the image. As shown, the beam appears a relatively scattered though a discernable image of irradiated pixels  90  representing the “slice” of the countersink  82 . The breaks  92  in the irradiated pixels  90  are caused by the support struts  52  casting a shadow and impeding the countersink laser cone. This slice is taken proximate the opening of the bore  80  at the workpiece surface, where the bore  80  is widest. The peak irradiance measured at the countersink camera lens  72  is 0.158 Watts per centimeter squared (W/cm 2 ). The image is 1000 pixels wide by 1000 pixels high, and 2.4 millimeters wide by 2.4 millimeters high. The more sparse distribution of irradiated pixels of the irradiated pixels  90  are the result of beam scatter of the countersink laser cone  68  traveling further to reach the extremities of the countersink  82 . 
     Conversely,  FIG. 8  illustrates an image  195  representing the countersink  82  at a position proximate the bore  80 . As shown, the slice of the countersink  82  proximate the bore  80  produces irradiated pixels  190  that have more sharply defined edges and greater pixel resolution, with an irradiance of 0.25 W/cm 2 . The irradiated pixels  190  also include breaks  192  caused by the support struts  52 . The geometry of the countersink is established based on the measurements taken using the probe as described herein. The outermost diameter of the countersink is identified where the countersink laser cone  68  begins to be received at the countersink camera lens  72 . The angle of the countersink can be established through measurement of the diameter of the countersink at any two depths, and using the distance the probe tip  24  was advanced between those two measurements, as measured by the robot  10 . 
     The robot  10  advancing the probe  20  to a countersink and bore of a work surface may do so through coordinate locations of a machined countersink and bore in a workpiece. Optionally, the probe  20  may be advanced to a countersink and bore of a work surface through visual identification using, for example, a camera. The forward-facing camera of the forward-facing camera lens  54  may be used for general alignment of the probe tip  24  with the countersink and bore of the work surface. The alignment performed visually, based on coordinate locations, or a combination thereof may position the probe tip  24  sufficiently close to the countersink to enable initial measurements to be taken. As shown in  FIG. 7 , the probe tip  24  is entering the countersink  82  and the bore  80 . Embodiments of the probe  20  apparatus described herein may provide further alignment and orientation based on measurement of the countersink  82  and/or bore  80 . 
     As the probe tip  24  approaches the countersink  82  and measurement of the surface and countersink commence, a non-circular (i.e., elliptical) countersink or bore indicates that the probe tip  24  is not axially aligned with the bore  80 . The height and width of the initial arcs received by the countersink camera lens  72  are used to determine alignment and normality of the probe tip  24  with the work surface and bore  80  there through. Embodiments described herein provide a feedback loop to the controller  30  whereby alignment instructions are generated and provided to the robot  10  to align the probe tip  24  with the bore  80 . The alignment instructions provide end-effector rotation axis and degree to enable the probe tip  24  to become aligned with the bore  80 . In practice, as the probe tip  24  approaches the countersink  82  and bore  80 , measurements identifying the countersink  82  or bore  80  as elliptical may cause the robot to cease advancement of the probe tip  24  into the bore  80 . Alignment of the probe tip  24  may commence with the rotation of the robot end effector to correct the axial alignment of the probe tip  24  with the bore  80 . Axial alignment is identified as achieved when the measurement of the bore  80  or countersink  82  provides a circular resultant shape. 
       FIG. 9  illustrates the probe tip  24  inserted through the workpiece  84  and emerging from an exit surface  88  of the workpiece, where the countersink  82  is disposed on a front side  86  of the workpiece  84 . The illustrated embodiment of  FIG. 9  depicts measurement of the bore  80  as the bore laser cone  64  remains within the bore  80 . The illustrated cross-section view depicts the first laser cone  63  emitted from the laser diode  60   a  and diffractive optical element  60   b  and reflecting from first reflective surface  62  forming the bore laser cone  64 . The bore laser cone  64  reaches the bore  80  and is reflected back to another reflective surface (i.e., third reflective surface  61 ), that reflects the beam from the bore laser cone  64  to the bore camera lens  70  along beam path  65 . The countersink laser cone  68  is also depicted; however, due to their angle of incidence in the bore  80 , the countersink laser cone  68  is reflected away from interfering with the bore laser cone that is received at the bore camera lens  70 . 
       FIG. 10  illustrates the irradiance received at the bore camera lens in image  295  with irradiated pixels  290  with breaks  292  as found in the images of the countersink. The X, Y pixel locations in the image correspond to the hole diameter at the point of measurement. The image is 2.0 millimeters wide and 2.0 millimeters high, and the irradiance of the image  295  of  FIG. 10  is 0.183 W/cm 2 . 
       FIG. 11  illustrates a section view of the probe tip  24  as it exits the exit surface  88  of the workpiece  84 . As it is exiting, a substantially normal bore slice is seen in image  395  with irradiated pixels  392 . However, as seen in the cross-section image of the probe tip  24  exiting the workpiece  84 , there is an exit burr  300  at the exit surface  88  of the workpiece  84 , not yet reached by the bore laser cone  64 .  FIG. 12  illustrates a section view the probe tip  24  as the bore laser cone  64  exits the bore  80  on the exit surface  88  of the workpiece  84 . At the illustrated point, the bore laser cone has encountered the exit burr  300 , where there is a corresponding burr diametrically opposed to the illustrated burr. As shown in the image  495 , the diameter of the bore is no longer seen since the bore laser cone no longer impinges on the inside of the bore  80 . However, irradiated pixels  492  illustrate exit burrs  300  at the exit surface  88  surface of the workpiece  84 . The controller  30  is configured to measure one or more dimensions of the burr  300  in response to the bore laser cone  64  reflected from the burr  300  and received at the bore camera lens  70 . The presence of these irregularities provides an indication of surface anomalies in the form of burrs, while the travel distance of the probe tip  24  between the last indication of the bore  80  diameter and the last indication of the exit burrs  300  in irradiated pixels  492  provide a height of the exit burrs  300 . In the illustrated embodiment, for example, the exit burr  300  is detected as having an arc length of 0.27 inches, and a height of 0.003 inches. 
     As the probe tip  24  continues to pass through the bore  80 , the probe tip exits the exit surface  88  of the workpiece  84 . The bore laser cone  64 , reflecting from first reflective surface  62  no longer impinges on the bore  80  as shown in  FIG. 13 . Rather, the bore laser cone  64  is reflected from first reflective surface  62  and scattered by the exit surface  88  of the workpiece  84 . Diffuse reflected rays follow path  78  and are reflected from surface  79  to reach forward-facing camera lens  54 , producing a diffuse image  595  of the edge of the bore. The diffuse image provides the distance to the back surface and may include irradiated pixels  592  depicting indications of the burrs on the exit surface  88  of the workpiece  84  where pixels in the vicinity of the burrs may be more diffuse due to the irregular surface at the locations of the burrs. 
     The probe  20  of example embodiments described herein therefore is able to provide precise measurement of a countersink and bore, and to identify surface anomalies including burrs of only thousandths of an inch. Further, the probe  20  described herein is constructed of inexpensive components such that probes may be disposable. As measurement probes of the scale described herein are susceptible to damage due to their size and function, a precise measurement tool that is low cost is highly desirable. 
     To maintain a low production cost of probes as described herein, the probes may be manufactured with relatively wide tolerances with respect to the finite measurements the probes are able to make. As such, each probe may be uniquely calibrated to compensate for any manufacturing variations. Calibration may be performed at the time of manufacture or by an end-user to generate a calibration table that is unique to each probe. Embodiments described herein may use metrology reference bores  600  to calibrate probe  20 , as depicted in  FIG. 14 . The calibration procedure may proceed in substantially the same manner as described above with respect to measurement of a countersink and bore. The precise dimensions of the reference bores  600  are known, such that measurements taken with the probe  20  can be compared against the known reference bore. From the differences between the measurements of the probe  20  and the reference bore  600 , a calibration table  602 . The reference table may include calibration parameters for a variety of different elements of the probe  20 . For example, the angular offset of the probe tip  24  relative to the probe base  26  may be identified, along with internal component calibration parameters, such as an angular offset of each of the camera lenses, an angular offset of the beams, a rotational component of the camera lenses, etc. The calibration table  602  may include calibration parameters for any features of the probe  20  that may vary between units. 
     Using the calibration table  602  derived for the specific probe  20 , the calibration table  602  may be employed with sensed measurements of the probe to arrive at accurate and repeatable measurements from the sensor to measure bores  604  in situ. 
     Embodiments described herein may be aligned with a bore and countersink through coordinate location as described above, and may employ visual locating. Embodiments of the probe  20  may use the forward-facing camera lens  54  to identify the location of the probe tip  24  relative to a bore or countersink. To accomplish this, off-axis illumination may be provided by a light source, such as light source  620  of  FIG. 15 . In an example, light source  620  is an off-axis illumination device. As shown, the light source  620  illuminates a surface of a workpiece, and reflected illumination is received through the in the forward-facing field of view  56  (as shown in  FIG. 4 ) into the probe tip  24  and captured at the forward-facing camera lens  54 . Based on the light reflected from the surface of the workpiece  630 , a bore or countersink within the workpiece can be identified by a change in the reflected light. Using this technique, embodiments of the probe  20  can identify a bore and countersink location independently, and subsequently use the techniques described above for alignment with the bore based on dimensional measurement of the bore or countersink. 
       FIG. 16  is a flowchart of a method for optically measuring workpiece features, and more particularly, to optically measure internal surfaces of round bores and countersinks. According to the illustrated method  700 , a probe  20  is advanced through a bore  80  and a countersink  82  as shown at block  710 . A first laser cone  63  is directed to a first reflective surface  62  to form a bore laser cone  64  at block  720  and a second laser cone  67  is directed to a second reflective surface  66  to form a countersink laser cone  68  at block  730 . A bore camera lens  70  receives the bore laser cone  64  as shown at block  740  that has been reflected by the first reflective surface  62 , reflected by the bore  80 , and reflected by a third reflective surface  61  to the bore camera lens  70 . A countersink camera lens  72  receives the countersink laser cone  68  as shown at block  750  that has been reflected by the second reflective surface  66 , reflected by the countersink  82 , and reflected by a countersink beam reflector  74  to the countersink camera lens  72 . The bore  80  surface is measured at block  760  based on the bore laser cone  64  received at the bore camera lens  70 . The countersink  82  is measured at block  770  based on the countersink laser cone  68  received at the countersink camera lens  72 . 
     In an example, method  700  further includes generating, from a laser source  60  including a laser diode  60   a  and a diffractive optical element  60   b , the first laser cone  63  at a first opening angle  163 , where the first laser cone is reflected at the first reflective surface  62  to form the bore laser cone, and generating, from the laser source  60  including the laser diode  60   a  and the diffractive optical element  60   b , the second laser cone  67  at a second opening angle  167 , where the second laser cone is reflected at the second reflected surface to form the countersink laser cone, and where the second opening angle  167  is different from the first opening angle  163 . 
     In an example, method  700  further includes identifying the bore  80  in a workpiece  84  based on light reflected from the workpiece to a forward-facing camera lens  54  of the probe  20  through an opening  22  defined in the probe tip  24 . 
     In an example, measuring dimensions of the bore  80  and the countersink  82  are performed based, at least in part, on a calibration table  602  established for the probe  20 . 
     In an example, method  700  further includes measuring dimensions of an exit burr  300  on an exit surface  88  of the bore in response to the probe  20  advancing past the exit surface  88  of the bore  80 . 
     As described above,  FIG. 16  illustrates a flowchart of a system, method, and apparatus according to example embodiments of the present disclosure. It will be understood that each block of the flowcharts, and combinations of blocks in the flowcharts, may be implemented by various means, such as hardware, firmware, processor, circuitry, computing device, and/or other devices associated with execution of software including one or more computer program instructions. For example, one or more of the procedures described above may be embodied by computer program instructions. In this regard, the computer program instructions which embody the procedures described above may be stored by the memory  38  of a controller  30  employing an embodiment of the present disclosure and executed by the processing circuitry  36  of the controller  30 . As will be appreciated, any such computer program instructions may be loaded onto a computer or other programmable apparatus (e.g., hardware) to produce a machine, such that the resulting computer or other programmable apparatus implements the functions specified in the flowchart blocks. These computer program instructions may also be stored in a computer-readable memory that may direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture the execution of which implements the function specified in the flowchart blocks. The computer program instructions may also be loaded onto a computer or other programmable apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flowchart blocks. 
     Accordingly, blocks of the flowcharts support combinations of means for performing the specified functions and combinations of operations for performing the specified functions for performing the specified functions. It will also be understood that one or more blocks of the flowcharts, and combinations of blocks in the flowcharts, can be implemented by special purpose hardware-based computer systems which perform the specified functions, or combinations of special purpose hardware and computer instructions. 
     In some embodiments, certain ones of the operations above may be modified or further amplified. Furthermore, in some embodiments, additional optional operations may be included. Modifications, additions, or amplifications to the operations above may be performed in any order and in any combination. 
     Many modifications and other embodiments set forth herein will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the present application is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe example embodiments in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.