VELOCITY MATCHING IMAGING OF A TARGET ELEMENT

A system may include an image sensor. A system may include an actuator configured to cause a controlled movement of the image sensor relative to a target element, the controlled movement being based on an operating velocity of the target element relative to an initial position of the image sensor. A system may include a controller communicatively coupled to the image sensor, the controller configured to: identify the operating velocity, determine an activation time to activate the image sensor for a designated exposure time based on the operating velocity and the controlled movement; and activate the image sensor at the activation time.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to Indian Provisional Application No. 202311059598 filed Sep. 5, 2023, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

These teachings relate generally to motion imaging and more particularly to velocity matching imaging of a target element.

BACKGROUND

Visual artifacts are anomalies apparent in visual representations such as photographs. Motion blur is an artifact that results when the image being recorded moves during the recording of a single exposure. Capturing fast moving objects with a rolling shutter camera can further introduce wobble, skew, spatial aliasing, and temporal aliasing, reducing the overall clarity and accuracy of the captured images.

DETAILED DESCRIPTION

The terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein. The word “or” when used herein shall be interpreted as having a disjunctive construction rather than a conjunctive construction unless otherwise specifically indicated. The terms “coupled,” “fixed,” “attached to,” and the like refer to both direct coupling, fixing, or attaching, as well as indirect coupling, fixing, or attaching through one or more intermediate components or features, unless otherwise specified herein.

Borescope inspection is typically done periodically to assess the distress level of components inside a fully or partially assembled aircraft engine. Imaging inspections can be done under diffused lighting with continuous illumination and are performed in motion, with either the component moving while the camera is stationary or the camera moving with respect to the component. However, the still and video images captured under these conditions can include imaging artifacts, such as motion blur or the like, introduced due to the motion of the moving elements. Currently, low engine rotation speeds such as 0.1 or 0.2 revolutions per minute, intense illumination, and/or short exposure times are utilized to minimize the motion blur effect from movement of the components. Motion blur and other imaging artifacts can also be corrected using various image processing techniques, such as blind deconvolution, which characterizes the speed and angle of motion using image processing methods to estimate a point spread function for motion artifacts. Conventional techniques for artifact correction are commonly very processing intensive, take significant time to be applied, and can require layers of additional post processing (e.g., deconvolution) to correct for other artifacts introduced during post processing. These are all significant challenges in the context of imagining of aircraft components.

Generally speaking, the various aspects of the present disclosure are employed with a system that includes an image sensor and an actuator that is activated to move the image sensor at a similar speed and in a similar direction to a target element, such as rotating airfoils of a turbo engine. In some embodiments, the speed of rotation of the target element is taken as an input to set and trigger movement of a tool carrying the image sensor parallel to the component in motion so as to maintain the same frame of reference. When the imaging tool and component are moving in the same direction with generally the same speed, the image sensor and the target element are in a pseudo-static state. Images acquired in this state can achieve the full resolution of the image sensor without or with reduced motion artifacts. Once the images are acquired, the tool is reset to the original position and the motion is periodically repeated as the target element passes by the image sensor. In some embodiments, the speed input is identified by an external optical trigger, a proximity probe, an acoustic sensor, etc. In some embodiments, the target element includes a fan blade or similar rotating component of a turbofan engine, and a sensor device can count the number of blades passing by the image sensor in a preconfigured unit time and utilize the counted number and unit time to estimate the speed of the target element.

The foregoing and other benefits may become clearer upon making a thorough review and study of the following detailed description. Referring now to the drawings, and in particular toFIG.1, a part inspection imaging system or inspection system100that is compatible with many of these teachings and for use in inspecting a system102such as an engine or the like will now be presented. The inspection system100includes a borescope unit104having a camera106, a guide tube108, and a light source110. In some embodiments, the light source110is a standard light source integrated into the borescope unit104. However, in some embodiments, the light source110is physically separate from the borescope unit104. The light source110can include various different light emitting devices, such as a light emitting diode, an array of light emitting diodes, a xenon strobe light, a laser light source, a fiberoptic light transport, other direct local light sources, other indirect remote light sources, etc.

The guide tube108is used to position the camera106and/or the light source110at a desired location relative to the system102, for example, an interior region R of the system102. The distal end of the guide tube108is generally small and narrow and is fed into difficult to reach locations, such as the inside of objects or mechanical devices, including jet engines or the like. When placed inside the system102, the camera106then relays image data captured thereby back to an eyepiece and/or a display where the inside of the system102can be viewed and magnified. For instance, the camera106can be used to obtain images of a target element120in the interior region R of the system102. In some embodiments, the light source110is mounted on the guide tube108to be brought into position where the light source110can illuminate a target element120of the system102.

In some embodiments, the borescope unit104is replaced with a snake-arm robot, such as any of those disclosed in U.S. Pat. Nos. 8,069,747B2, 7,543,518B2, U.S. Ser. No. 11/084,169B2 and European Patents EP2170565B1, EP3643451A1, EP3643452A1, each of which is incorporated by reference in their entirety. Snake-arm robots, like borescopes, are used to inspect confined spaces. Snake-arm robots are electro-mechanical devices that include an arm with high degrees of freedom that are controlled in a snake-like manner to follow a contoured path and avoid obstacles or comply when contacting obstacles. A snake arm robot typically includes a sequence of links that are driven by one or more motors and can move relative to one another to change the shape or curvature of the extension arm. In some embodiments, the inspection system100may include a rigid or flexible elongated extension element that is sized and shaped to insert the camera106and the light source110into a confined space, such as the interior of a jet engine, to perform inspection. It will also be appreciated that the inspection system100can be deployed in conjunction with non-confined space vision systems used to identify surface anomalies on an accessible portion of an object, for example, in a photo studio setting or the like.

The inspection system100includes a sensor114and a controller116that is communicatively and/or electrically coupled to the sensor114, the camera106, and/or the light source110. The camera106is supported inside the guide tube108and includes an image sensor112with a field of view118for capturing one or more images of the target element120inside the system102. In some embodiments, the image sensor112is located at a distal end of the borescope unit104. The camera106can also include other optical elements, such as lenses and the like, that together with the image sensor112form an optical system with a resolution with respect to static (e.g. non-moving objects) that is defined in terms of line pairs per millimeter (lp/mm). In particular, lp/mm refers to the ability of the optical system to fully distinguish between a number of separately delineated same-sized black and white pairs of lines (i.e., the line pairs) presented in a specific spatial region a certain mm in length. As seen inFIG.1, the controller116can include a programmable processor117and a memory119. The processor117may include, for example, a microprocessor, a system-on-a-chip, an application specific integrated circuit (ASIC), and/or a field programmable gate array (FPGA). The memory119may include, for example, an electrical charge-based storage media such as EEPROM or RAM, or other non-transitory computer readable media.

Where the system102includes a jet engine or the like, the target element120can include one or more fan blades, compressor blades, turbine blades, stator airfoils, nozzles, guide vanes, shrouds casings, combustor liners, and/or other elements of the engine. Furthermore, the sensor114includes a sensing region122in which the sensor114detects movement of the target element120relative to the sensor114, for example relative movement of a blade or shaft encoder to detect blade presence in multiple stages. It will be appreciated that in cases where the camera106is used to inspect stationary elements the controlled movement of the camera106as described herein is superimposed on gross motion of the inspection system100at the camera106and not at or via a base of the borescope unit104or similar insertion device.

In some embodiments, the target element120is moved by a turning tool123. The turning tool123can control the operating velocity of the target element120within the interior region R either at the direction of the controller116or a different controller distinct from the controller116. For example, the turning tool123can rotate a shaft of an engine to in turn rotate fan blades that include the target element120inside the interior region R. In some embodiments, the operating velocity of the target element120is in the range of about 1 mm/s to about 50 mm/s. Furthermore, in some cases the camera106is used to image a stationary object. In such cases, the turning tool123can be used to transport the camera106, mounted on a moving element of the engine, for example a blade, rotor or shaft, with respect to the stationary object.

In some embodiments, the sensor114is used to detect movement of another portion of the system102that is linked to the target element120, for example a shaft or rotor of a jet engine. The sensor114is coupled to the guide tube108for insertion into the system102along with the borescope unit104. Alternatively, the sensor114is a standalone device that is separately positionable relative to the system102proximate to the target element120. The sensor114can include, but is not limited to, various contact and non-contact motion sensing devices, such as a whisker or electrical continuity sensor or switch, a roller type switch, an inductive proximity sensor, an optical proximity sensor, a hall effect sensor, an electrical continuity sensor, an ultrasonic sensor, etc. Where the sensor114is a contact sensor, such as a switch, the sensing region122can include a region in which the contact sensor physically traverses. In some embodiments, where the sensor114is triggered off of a rotor or shaft of the system102, the sensor114can include a roller located on the shaft or rotor, a motion flow sensor such as in an optical or laser mouse, a gyroscope or inertial measurement unit (IMU) attached to the shaft or rotor, a pull thread temporarily attached to the shaft or rotor, or other similar devices.

The inspection system100also includes an actuator124. The actuator124is configured to cause a controlled movement of the image sensor112relative to the target element120. In some embodiments, the controller116is configured to activate the actuator124to perform the controlled movement. The controlled movement brings a speed and movement direction of the image sensor112to within a range of at least about 20% to about 1% of the operating velocity of the target element120during an imaging period that encompasses a designated exposure time for the image sensor112. In some examples, the designated exposure time is in a range from about 1 ms to about 50 ms. In some embodiments where the turning tool123is used to move the target element120, the actuator124is linked to the turning tool123such that rotation of the target element120at the operating velocity induces the controlled movement.

Furthermore, in some embodiments, the inspection system100includes a movement guide126. The movement guide126is configured to induce the controlled movement of the image sensor112applied by the actuator124to follow a preconfigured path. In some embodiments, the movement guide126is coupled to the borescope unit104. The preconfigured path can include a curved path of the target element120around a rotational axis (e.g., a rotation point of an engine fan blade or the like), a linear path perpendicular to a tool axis127through which the image sensor112is inserted into the interior region R, or other. As shown inFIG.1, the image sensor112is inserted into the interior region R through a port128of the system102. In particular, where the image sensor112is part of the borescope unit104, a distal end of the borescope unit104is inserted through the port128along the tool axis127so that a first portion130of the borescope unit104passes through the port128and a second portion132of the borescope unit104is disposed at a generally perpendicular angle to the first portion130within the interior region R. The first portion130and the second portion132is a subset of various elongated portions of the borescope unit104that are angled with respect to each other. In some embodiments, the angles between the different elongate portions (including between the first portion130and the second portion132) are adjustable to enable the field of view118of the image sensor112to include an area of the interior region R through which the target element120moves.

With reference now toFIG.2, the image sensor112includes a plurality of light sensitive pixel elements200that are activatable. The plurality of light sensitive pixel elements200are arranged in discrete rows202A,202B,202C,202Z, etc. as shown inFIG.2. The plurality of light sensitive pixel elements200are activated simultaneously, individually on a rolling basis, and/or by discrete rows on a rolling basis. The designated exposure time includes the time period over which the plurality of light sensitive pixel elements200are active. Thus, for situations where the activation is done on a rolling basis, the designated exposure time begins when the first pixel is activated and ends when the last pixel is deactivated. When activated, each one of the activated light sensitive pixel elements200generates a digital signal representative of light viewable by that pixel element when active. The camera106and/or the controller116can convert those digital signals into image data that is viewable on a display device by an operator of the inspection system100. In some embodiments, the controller116determines an activation time for the image sensor112(e.g., the time when the light sensitive pixel elements200are activated for the exposure time) based on the operating velocity of the target element120relative to an initial position of the image sensor112within the interior region R. Furthermore, the controller116can be configured to activate the image sensor112at the activation time.

In general, the controller116can synchronize the activation time of the image sensor112with the movement of the target element120. In particular, the controller116can identify the operating velocity of the target element120and base the activation time of the image sensor112on the identified operating velocity. The controller can receive user input that identifies the operating velocity directly or determine the operating velocity using the sensor114. In particular, a trigger signal or condition such as a detection signal that is sent or transmitted from the sensor114, is received at the controller116, and indicates the presence of movement within the sensing region122is utilized to determine the operating velocity and/or to directly initiate activation of the image sensor112. As such the detection signal can detect a position of a fan blade to synchronize with the frame rate of the camera106.

In some embodiments, the controller116utilizes a time delay as measured from receipt of the detection signal to synchronize the activation of the image sensor112with the movement of the target element120. Specifically, the time delay is used to ensure that the target element120is within the field of view118when the image sensor112is activated. The time delay is set to a time value measured from receipt of the detection signal to the occurrence of a specific frame in a sequence of frames being captured by the image sensor112. The specific frame can be a set first number of frames before a key frame that will include the target element120. The set number of frames can be based on a known or average revolutions per minute (RPM) associated with the target element120. Furthermore, the image sensor112is activated until a second set number of frames after the key frame.

The first and second set number of frames are dependent on the precise nature of the rotation of the target element120. For example, where the RPM of the target element120is generally constant and non-variable (e.g., when moved by use of a precise version of the turning tool123) the first and second set numbers of frames are one. However, where the RPM of the target element120is more variable or uncertain (e.g. by a version of the turning tool123with a varying turning tool speed), the first and second set numbers of frames are a higher number such as ten frames to ensure that the target element120is captured by the image sensor112.

The time delay can also be set based on an average RPM of the target element120. In some embodiments, the controller116determines the average RPM from repeated receptions of the detection signal. The time delay is determined using time and/or distance synchronization. In particular, time synchronization can include utilizing a known travel time between a location of the sensor114and the field of view118and distance synchronization can include utilizing a known distance between a location of the sensor114and the field of view118. Furthermore, in some embodiments, the first and second set numbers of frames are determined as a function of an observed standard deviation in the operating velocity of the target element120relative to the stationary initial position of the image sensor112.

It will be understood that the movement detected by the sensor114is the movement of the target element120or the movement of another element associated with the target element120. For example, where the target element120is part of a group of moving elements that move through the sensing region122on a repeating and periodic basis, the movement that initiates the blade detection signal is the movement of a preceding or succeeding element in the group. Specifically, where the target element120includes a fan blade of a jet engine, a trigger for the controller to activate the image sensor112and capture one or more images of that specific fan blade is the presence of another of the fan blades within the sensing region122. Furthermore, the motion detected by the sensor114is the motion of the shaft or rotor of the engine.

In some embodiments, where the target element120includes elements from within multiple stages of an engine, such as the stage of fan blades and multiple stages of other elements and airfoils (e.g. stator airfoils, rotor airfoils, compressor vanes, compressor blades, turbine blades, turbine buckets, turbine vanes, etc.), the sensor114is configured to detect movement relative to a single common reference point for each of the multiple stages. For example, the single common reference point can include a shaft of the engine or the movement of blades within one stage. In these embodiments, illumination, imaging, and movement of the borescope unit104for each stage is done simultaneously via multiple borescope units104and using a known clocking of each of the stages.

In some embodiments, the sensor114is omitted. In these embodiments, synchronization of the activation of the image sensor112with the movement of the target element120is accomplished using a known repeating and periodic movement relative to the field of view118based on a known frequency and duration of the repeating periodic motion of the target element120(e.g., a known clocking rate of the target element120). Furthermore, in embodiments where the exact clocking rate of the target element120is not known and the sensor114is also omitted, the synchronization of the activation of the image sensor112and the movement of the target element120is accomplished using the image sensor112and a time delay calibration method such as described in U.S. patent application Ser. No. 18/141,493 filed on May 1, 2023, which is incorporated by reference in its entirety.

With reference now toFIG.3, the target element120is one of a first set of airfoils300of the system102. The first set of airfoils300can include a set of blades mounted together on a shaft, disc, or blisc, and capable of rotating together about a common axis relative to stationary stator vanes302. As shown inFIG.3, the operating velocity of the target element120can include a linear velocity306of a point on the target element120that is a distance304from the tool axis127and in line with a central ray314of the image sensor112(FIG.1). InFIG.3, the controlled movement caused by the actuator124(FIG.1) is a linear velocity308with a directional component that is linear and oriented parallel or tangential to the linear velocity306and generally perpendicular with respect to the tool axis127. The controlled movement takes place entirely within a clearance defined by a difference between a first diameter310of the port128and a second diameter312of the longer section of the borescope unit104that passes through the port128and is configured to avoid any of the stationary stator vanes302or other obstacles present in the interior region R. In some embodiments, the clearance distance is in a range from about 0.1 mm to about 4 mm. In some embodiments, the minimum clearance for the controlled movement may be between some other position or obstacle in the interior region R and a different part of the borescope unit104.

The borescope unit104may include a bend or protrusion on which the camera106is mounted such that the tool axis127is parallel to the direction of view ofFIG.3(e.g., in/out of the page). In this case, the borescope unit104is L-shaped, in which the vertical stroke of the L represents the long shaft, while the horizontal stroke represents the camera106. In other instances, the camera106may be positioned so that the field of view118is at an angle to the shaft but be housed within the second diameter312. In other embodiments, the transition from an axis of the camera106to the tool axis127may be curved or offset such that the two axes do not intersect (e.g., there may be more a complex transition from the shaft to the camera106then as shown inFIG.3). The shaft and the camera body may be approximately linear or may be shaped for access or for obstacle avoidance in more complex manners understood by those having skill in the art.

The controlled movement is configured to move the camera106and thus the image sensor112so that the motion of at least one point on the target element120(e.g. one or more of the first set of airfoils300) is slowed relative to at least one ray entering the camera lens (e.g. the central ray314). This slow down produces a relative motion of the key point on the target element120as projected to an image plane of the camera106that is reduced to minimize or reduce image blur. The relative speed between the target element120and the image sensor112is configured to be slow or stationary for the exposure time teof the image sensor112.

FIG.3generally shows a projection looking from an engine center outwards along the tool axis127in which the first set of airfoils300are shown as moving in the linear velocity306. However, it will be appreciated thatFIG.3shows a flat representation of a set of objects (e.g. the first set of airfoils300) mounted on a cylindrical support (shaft or disc) which rotates about the engine centerline. In some embodiments, the controlled movement of the image sensor112is at least partially curved to match the rotation of the target element120about the engine centerline to ensure that all points on the blade are projected to fixed positions in an image plane of the camera106for the duration of the exposure time. In some embodiments, the movement guide126is configured to constrain movement of the borescope unit104or similar support structure for the camera106induced by the actuator124to follow the partially curved path that matches the rotational path of the target element120around the engine centerline.

Furthermore, as seen inFIG.4, in some embodiments, the controlled movement induced by the actuator124(FIG.1) is an angular velocity400around the tool axis127. In particular, the actuator124is configured to oscillate the borescope unit104in a rotary manner around the tool axis127. In these embodiments, there is relatively less clearance between the borescope unit104and the port128as compared with the generally linear motion described with respect toFIG.3. Because of the rotary motion, the limitation on the maximum amount of the controlled motion is defined by angular limits within the interior region R instead of the difference between the first diameter310and the second diameter312. These angular limits include a maximum angular displacement402at which the camera106(or other relevant section of the borescope unit104) would contact the stationary stator vanes302adjacent the port128and/or other obstacles present within the interior region R. Thus, use of the rotational angular velocity400in place of the linear velocity308can enable matching of the operating velocity for cases where the clearance between the first diameter310and the second diameter312ofFIG.3are small enough to make linear motion ineffective or cost prohibitive such as clearances that are less than 1 mm, less than 2 mm, or less than 4 mm.

Given the rotational nature of the controlled movement, matching the linear velocity306of the target element120to the angular velocity400is defined with reference to a key point403on the target element120. In particular, the actuator124(FIG.1) is configured to match the speed and direction (e.g., the linear velocity306) of the movement of the central ray314, where the central ray314is defined from a center point of the camera lens to the key point403. The key point403moves at the linear velocity306, which can be broken down into a horizontal component404perpendicular to the central ray314and a vertical component406parallel to the central ray314. The horizontal component404and vertical component406are vectors that when summed together equal the linear velocity306. The rotational speed for the camera106that matches the linear velocity306can be determined using circular motion equations 1-3 below. The variables vx, r, ωc, vt, and Ø in equations 1-3 correspond, respectively, to a magnitude of the horizontal component404, the distance304, a magnitude of the angular velocity400, a magnitude of the linear velocity306, and an angle408between the linear velocity306and the horizontal component404.

With reference now toFIG.5, it will be further appreciated that the actuator124(FIG.1) can be configured to induce the controlled movement as a hybrid or combination of the linear and revolution arrangements ofFIGS.3and4. In particular, the actuator124can be configured to cause a rotational movement around a pivot axis or rotational axis500to perform the controlled movement. The rotational axis500is located at a point outside the interior region R and is disposed perpendicular to the tool axis127at a distance502from the camera106. As shown inFIG.5, the rotational axis500is located proximate to an exterior casing of the system102to reduce the amount of lateral motion of the borescope unit104within the port128, and provide for a near-linear motion of the camera106at the distal end of the borescope unit104. Furthermore, longer lengths for the distance502then shown inFIG.5are possible. Such increased values of the distance502result in less rotation of the camera106within the interior region R.

With reference now toFIGS.6-9, different embodiments for the actuator124will be discussed in more detail.FIG.6shows a crank and rocker arrangement for the actuator124. Specifically, the actuator124includes a crank600that rotates continuously about a point602and that has a fixed non-zero length between the point602and a point604. The actuator124further includes a rocker606that rotates about a point608and has a fixed non-zero length between the point608and a point610. The crank600and the rocker606are connected by a linkage612having a fixed non-zero length between the point604and the point610. The points602and608are stationary relative to a common frame of reference such as an engine casing or other exterior portion of the interior region R. As the crank600rotates continuously about the point602, the rocker606moves in a reciprocating arcuate motion about the point608.

As shown inFIG.6, the camera106and/or the borescope unit104is coupled to the rocker606at the point610by a linkage616. The linkage616, either alone or in combination with the movement guide126(FIG.1), can convert the rotary motion of the rocker606into a general linear motion applied to the camera106and/or the borescope unit104(e.g., the linear velocity308). For these and similar linear motion embodiments describe herein, the movement guide126(FIG.1) can include a linear slide or guide. In some embodiments, the conversion of the rotary motion to linear motion is accomplished by separating out the rotational and linear components of the rotation of the rocker606.

Alternatively, in some embodiments, the camera106and/or the borescope unit104is coupled directly to or in close proximity to the point610. In these embodiments, the shape of the controlled movement induced by the actuator124is a function of the distances between the various points602,604,608, and610. For example, if a length614between the point602and the point608and a length of the rocker606are long compared to lengths of the crank600and the rocker606, the motion of the rocker606at the point610will tend towards a sinusoidal linear motion. However, different relative distances between the various points602,604,608, and610can induce the motion of the rocker606at the point610to tend towards rotational motion for use in applying the angular velocity400as shown inFIG.4.

FIG.7shows a cam and cam follower arrangement for the actuator124. Specifically, the version of the actuator124shown inFIG.7includes a cam700that rotates about a rotational axis702and a follower704that linearly and/or rotationally translates the camera106and/or the borescope unit104based on a physical profile of the cam700. In some embodiments, the profile of the cam700may be configured to provide the precise matched velocity (e.g. the linear velocity308and/or the angular velocity400(FIG.4)) during the exposure period of the camera106without error and with minimal acceleration and jerk during each phase of the controlled movement.

FIG.8shows a four-bar linkage embodiment of the actuator124. The four-bar linkage shown inFIG.8comprises linkages800,802, and804coupled together at pivot points806,808,810, and812. In particular, the linkage800is coupled to the linkage802at the pivot point808and the linkage802is coupled to the linkage804at the pivot point810. The pivot points812and806are fixed to the exterior or other portion of the system102to serve as a fourth linkage. Furthermore, the linkage802is coupled to the borescope unit104. In operation, the pivot point806and/or the pivot point812are actively rotated to induce rotational movement of the linkages800,802, and804which in turn induce the controlled movement on the borescope unit104and/or the camera106. For example, the four-bar linkage is arranged so that the controlled movement imparted to the borescope unit104and/or the camera106approximates the rotational motion of the target element120around the centerline of a rotating turbofan engine, such as by rotating the borescope unit104about the rotational axis500.

FIG.9shows a passive mechanical embodiment of the actuator124that transfers the movement of the first set of airfoils300into the angular velocity400and/or the linear velocity308. As shown inFIG.9, the actuator124comprises a finger member900or similar rigid or semi-rigid projection attached to the borescope unit104, for example to the guide tube108(FIG.1). The finger member900is made of or coated with a polymer or similar material configured to prevent or limit damage to the stationary stator vanes302and the first set of airfoils300. Additionally, the actuator124comprises a spring or similar mechanism902that biases the borescope unit104into the initial position and in a direction against the motion of the first set of airfoils300(e.g., in a counter-clockwise direction opposite the angular velocity400or in a linear direction opposite the linear velocity308). The spring is active at all times after the borescope unit104is inserted through the port128.

In operation, as the first set of airfoils300are rotated, a trailing airfoil902that trails the target element120contacts the finger member900when the target element120is within or nearly within the field of view118. In some embodiments, the sensor114(FIG.1) and/or another similar sensor can detect the position of the borescope unit104and/or the position of the target element120to trigger activation of the image sensor112of the camera106. The trailing airfoil902continues to move and induce rotational and/or linear movement on the camera106and/or the borescope unit104via the finger member900by overcoming the biasing force of the spring. Eventually, the borescope unit104reaches a point where the finger member900slips over the leading edge of the trailing airfoil902at which point the bias force imparted by the spring causes the borescope unit104to return to the initial position. In some embodiments, the finger member900is connected to the tool axis127via a gearbox or similar leverage providing member to better match the speed of the camera106to the speed of the first set of airfoils300.

Additional embodiments for the actuator124beyond those shown and described with respect toFIGS.6-9are also possible. For example, the actuator124can include a linear actuator, a voice coil, a torque motor, or other mechanical, magnetic, or piezoelectric actuator. The actuator124can also include different combinations of the various different embodiments for the actuator124described herein. The various embodiments are used in conjunction with either the linear, revolute, and/or hybrid variants of the controlled movement as described herein. In particular, the torque motor may be utilized for revolute variants of the controlled movement. The crank and rocker mechanism ofFIG.6may be used for both cases, except that in the revolute case, the camera106and/or the borescope unit104is mounted with a centreline at the point608, to rotate about the point608. The cam and cam follower example may also be used for both variations, except that for the revolute case the camera106and borescope unit104are provided with the follower704on a lever arm having a radius on which the cam700acts. Furthermore, different embodiments for the movement guide126may be utilized for the different variations of the controlled movement. In particular, for the linear variation, the movement guide126can include linear motion elements such as slides and guides used to constrain the borescope unit104and/or camera106to linear motion. For the revolute case, the movement guide126can include curved guides, curved guideways, ball slides or the like that contain the camera106and/or the borescope unit104to move in an arc around a centreline approximately co-located with a centreline of the system102around which the target element120rotates, so as to more precisely match the motion of the blades.

With reference now toFIGS.10-12, various patterns for the controlled movement induced by the actuator124will be discussed in more detail. In particular, the velocity patterns shown inFIGS.10-12show the velocity of the camera106(FIG.1) under the controlled movement on the y-axis over time on the x-axis. As shown inFIG.10, the controlled movement can include a linear velocity pattern1000that includes an initiation period1010where the actuator124accelerates the image sensor112to a steady state velocity that matches or approximates the operating velocity of the target element120(e.g., the linear velocity306ofFIGS.3and4). The steady state velocity can include the linear velocity308, the angular velocity400, or other hybrid variations as described herein. Furthermore, the steady state velocity can include a maximum velocity of the image sensor112and, in some embodiments, is within a range from about 20% to about 1% of the operating velocity of the target element120.

Following the initiation period1010, the linear velocity pattern1000includes a steady state period1020where the actuator124holds the image sensor112at the steady state velocity. The steady state period1020is configured to be longer than the designated exposure time for the image sensor112and, in some embodiments, is in a range of about 1 ms to about 166 ms. In some embodiments, the controller116sets the activation time for the image sensor112to occur during the steady state period1020such that the designated exposure time expires before an end of the steady state period1020.

Following the steady state period1020, the linear velocity pattern1000includes a deceleration period1030where the actuator124decelerates the image sensor112away from the steady state velocity back towards a velocity of zero. Following the deceleration period1030, the linear velocity pattern1000includes a reset period1035where the actuator124returns the image sensor112to its initial position. In some embodiments, the reset period1035can include equal magnitude and opposite direction inverses of the deceleration period1030, the steady state period1020, and the initiation period1010to return the image sensor to the initial position. For example, as shown inFIG.10, these remaining portions can include an inverse initiation period1040, and inverse steady state period1050, and an inverse deceleration period1060. However, it will be appreciated that other faster and slower configurations for the reset period1035are possible. For example, the reset period1035can be faster than the combined time for the initiation period1010, steady state period1020, and deceleration period1030to enable longer possible values for the exposure time and steady state period1020relative to a constant periodic rate of revolution for the target element120.

Following the reset period1035, the linear velocity pattern1000can repeat in a periodic manner to match a periodic nature of the movement of the target element120. In some embodiments, the periodic cycle of the linear velocity pattern1000is aligned with a repeating frame rate of the camera106or vice versa to ensure that the target element120is captured by the image sensor112. In some embodiments, a repetition rate for the periodic embodiments of the linear velocity pattern1000is in a range of about 1 cycle per second to about 100 cycles per second. However, in some embodiments, the repetition rate is in a range of 3 cycles per second to about 25 cycles per second. In these embodiments, the portions of the linear velocity pattern1000before the reset period1035can last between about 0.02 seconds (20 ms) and about 0.166 seconds (166 ms). In embodiments where the repetition rate is 100 cycles per second, the portions of the linear velocity pattern1000before the reset period1035can last about 0.005 seconds (5 ms). Furthermore, for a repetition rate of 15 cycles per second, the portions of the linear velocity pattern1000before the reset period1035can last 0.033 seconds (33 ms).

The travel distance of the image sensor112during the linear velocity pattern1000is defined in terms of straight-line motion in Equations 4-7 below (e.g., using linear measurements of the flat representation shown inFIG.3). However, it will be clear to a person of ordinary skill in the art that the equations 4-7 may easily be converted to cylindrical (angular) units as needed. Equation 4 defines a distance s1in which the image sensor112travels during the initiation period1010, Equation 5 defines the target steady state velocity, Equation 6 defines a distance s2that the image sensor112travels during the steady state period1020, and Equation 7 defines a distance s3the image sensor112travels during the deceleration period1030. For Equations 4-7, u equals an initial velocity of the image sensor112(e.g. 0), t1equals a time duration of initiation period1010, a1equals the acceleration during the initiation period1010, t2equals a time duration of the steady state period1020, t3equals a time duration of the deceleration period1030, and a3equals the deceleration during the deceleration period1030.

For purposes of the generally linear movement of the image sensor112described above with respect toFIG.3, the total of the distances s1, s2, and s3are constrained by the clearance amount C defined by the difference between first diameter310and the second diameter312(e.g., s1+s2+s3≤c). Additionally, the time t2is constrained to be greater than or equal to the exposure time tefor the image sensor112. Other practical constraints can also apply, such as values of the acceleration, velocity, and deceleration need to be within the tolerances of stiffness for the borescope unit104and achievable with available embodiment for the actuator124. There may also be an additional considerations for control system settling times and/or control of jerk (the first derivative of acceleration) to provide for a smooth motion.

In the particular example shown inFIG.10, the initiation period1010and the deceleration period1030are equal and opposite and a single period of the linear velocity pattern1000is completed in 0.04 seconds to accommodate a frame rate of 25 and an exposure time of 0.004 seconds or lower. Under these conditions the times t1and t3are set equal to 0.04−(2×0.004)/4 seconds (i.e. 0.008 seconds). Furthermore, using equations 4 and 6 above v1, a1, and s1are calculated as below.

Thus, for this specific example, the distance travelled during equal and opposite acceleration and deceleration cycles is 0.053 mm, which means the total motion for the image sensor112and/or the camera106is contained in a space of about 0.0532+2×0.053=0.16 mm. When a higher frame rate or a shorter exposure time is used, the rate of reciprocation may be increased from 25 cycles per second to 50 or 100 cycles per second. In turn, this would enable the engine to be turned at a higher rate and reduce the time taken to complete an inspection.

In some embodiments, the linear velocity pattern1000is substituted for a suitable approximation such as a sinusoidal or equivalent pattern. This substitution can reduce complexity and cost of the actuator124. An example curved velocity pattern1100is shownFIGS.11and12superimposed over the linear velocity pattern1000. The curved velocity pattern1100or an equivalent thereof are especially useful in combination with the crank and rocker, cam and cam follower, and four-bar linkage embodiments of the actuator124described with respect toFIGS.6-8.

As shown inFIG.11, the curved velocity pattern1100is fitted to minimize the difference with respect to the linear velocity pattern1000during steady state period1020in which the exposure time for the image sensor112will occur. As shown inFIG.12, the maximum mismatch or difference in magnitude between the target magnitude for the steady state velocity of the linear velocity pattern1000of 0.0133 m/s during the steady state period1020at points i, ii and iii in the figure above, is 0.000334 m/s, or about 2.5% of the target steady state velocity. This period of minimal overlap can constitute an imaging period or a positive peak period of the curved velocity pattern1100in which the controller116sets the activation time to occur such that the designated exposure time for the image sensor112expires before an end of the positive peak period (e.g., the imaging period has a first time length that is greater than the designated exposure time). Like the linear velocity pattern1000, the curved velocity pattern1100can be periodic to align with a periodic motion of the target element120. In particular, the curved velocity pattern1100can in some embodiments include a continuous periodic velocity pattern.

A method1300for inspecting a part or the system102with a part inspection imaging system such as the inspection system100is shown inFIG.13. In some embodiments, the method may be performed in whole or in part by the controller116. The method1300includes identifying the operating velocity of a target element120, as in1310. Then, the method1300includes performing, with the actuator124, the controlled movement of the image sensor112, as in1320. As described herein, the controlled movement is based on the operating velocity of the target element120relative to an initial position of the image sensor112. Next, the method1300includes setting an activation time to activate the image sensor112for the designated exposure time based on the operating velocity and the controlled movement, as in1330. Then, the method1300includes activating the image sensor112at the activation time, as in1340.

A part inspection imaging system comprising: an image sensor; an actuator configured to cause a controlled movement of the image sensor relative to a target element, the controlled movement being based on an operating velocity of the target element relative to an initial position of the image sensor; and a controller communicatively coupled to the image sensor, the controller configured to: identify the operating velocity; determine an activation time to activate the image sensor for a designated exposure time based on the operating velocity and the controlled movement; and activate the image sensor at the activation time.

The system of any preceding clause wherein the image sensor is located at a distal end of a borescope unit, wherein the distal end of the borescope unit is inserted through a port along a tool axis into an interior region that contains the target element.

The system of any preceding clause wherein a total travel distance of the image sensor from the initial position during the controlled movement is less than or equal to a clearance distance.

The system of any preceding clause wherein the clearance distance is a distance between an exterior of the borescope unit and an interior of the port when the image sensor is at the initial position.

The system of any preceding clause wherein the clearance distance is in a range from about 0.1 mm to about 4 mm.

The system of any preceding clause wherein the clearance distance is a distance between the distal end of the borescope unit and other elements present within the interior region.

The system of any preceding clause wherein the borescope unit comprises elongate portions angled with respect to each other, the elongate portions including a first portion that passes through the port and a second portion disposed perpendicular to the first portion within the interior region, and wherein the image sensor is disposed on the second portion.

The system of any preceding clause wherein the actuator linearly translates the borescope unit perpendicular to the tool axis to perform the controlled movement.

The system of any preceding clause wherein the actuator rotates the borescope unit around the tool axis to perform the controlled movement.

The system of any preceding clause wherein the actuator pivots the borescope unit around a pivot axis to perform the controlled movement, wherein the pivot axis is located at a point outside the interior region and is disposed perpendicular to a tool axis of the borescope unit at the point outside the interior region.

The system of any preceding clause wherein the actuator includes at least one of a linear actuator, a voice coil, a torque motor, a crank and rocker, a cam and cam follower, or a four-bar linkage.

The system of any preceding clause wherein the controller is configured to activate the actuator to perform the controlled movement of the image sensor relative to the target element.

The system of any preceding clause further comprising a turning tool configured to rotate the target element at the operating velocity.

The system of any preceding clause further comprising a second controller configured to activate the turning tool and the actuator.

The system of any preceding clause wherein the actuator is linked to the turning tool such that rotation of the target element at the operating velocity induces the controlled movement.

The system of any preceding clause wherein the controlled movement includes an initiation period where the actuator accelerates the image sensor to a steady state velocity that matches the operating velocity, a steady state period where the actuator holds the image sensor at the steady state velocity, and a deceleration period where the actuator decelerates the image sensor away from the steady state velocity.

The system of any preceding clause wherein the steady state velocity is an angular velocity around a tool axis through which the image sensor is inserted into an interior region that contains the target element, wherein the angular velocity matches the operating velocity when a center point of a camera lens associated with the image sensor has a velocity that approximately matches the velocity of a key point on the target element that is moving at the operating velocity.

The system of any preceding clause wherein the controlled movement includes a reset period where the actuator returns the image sensor to the initial position.

The system of any preceding clause wherein the reset period includes equal magnitude and opposite direction inverses of the deceleration period, the steady state period, and the initiation period to return the image sensor to the initial position.

The system of any preceding clause wherein the steady state period is longer than the designated exposure time, and wherein the controller sets the activation time to occur during the steady state period such that the designated exposure time expires before an end of the steady state period.

The system of any preceding clause wherein the controlled movement includes a continuous periodic velocity pattern for the image sensor, wherein the continuous periodic velocity pattern includes a positive peak period that includes a maximum velocity of the image sensor for the continuous periodic velocity pattern that is within a range of about 20% to about 1% of the operating velocity, and wherein the controller sets the activation time to occur during the positive peak period such that the designated exposure time expires before an end of the positive peak period.

The system of any preceding clause further comprising a movement guide coupled to a borescope unit that includes the image sensor, wherein the movement guide is configured to induce the controlled movement of the image sensor to follow a preconfigured path.

The system of any preceding clause wherein the preconfigured path includes a curved path of the target element with respect to a rotational axis, and wherein the movement guide includes at least one of a curved guideway or a ball slide.

The system of any preceding clause wherein the preconfigured path includes a linear path perpendicular to a tool axis through which the image sensor is inserted into an interior region that contains the target element, and wherein the movement guide includes linear slide or guide.

The system of any preceding clause further comprising an additional sensor configured to transmit a detection signal to the controller when the additional sensor detects movement within a sensing region of the additional sensor, wherein the controller determines the operating velocity based on the detection signal.

The system of any preceding clause wherein the sensor is one of a switch, an inductive proximity sensor, an optical proximity sensor, a hall effect sensor, an electrical continuity sensor, or an ultrasonic sensor.

The system of any preceding clause wherein the controller determines the operating velocity using a received user input.

The system of any preceding clause wherein the received user input includes a known frequency and duration of a repeating and periodic movement of the target element relative to the image sensor.

The system of any preceding clause wherein the activation time comprises a time delay from receipt of the detection signal based on a known value of the operating velocity.

The system of any preceding clause wherein the controller identifies the operating velocity from an average revolutions per minute of the target element, the average revolutions of the target element determined by the controller from repeated receptions of the detection signal, and wherein the activation time comprises a time delay from receipt of the detection signal based on the average revolutions per minute of the target element.

The system of any preceding clause wherein the controlled movement includes an imaging period where a maximum velocity of the image sensor is within a range of at least about 20% to about 1% of the operating velocity and a reset period, the imaging period having a first time length that is greater than the designated exposure time.

The system of any preceding clause wherein the first time length is in a range of about 20 ms to about 166 ms.

The system of any preceding clause wherein the reset period has a second time length that is equal to the first time length.

The system of any preceding clause wherein the reset period has a second time length that is greater than the first time length.

The system of any preceding clause wherein the reset period has a second time length that is less than the first time length.

The system of any preceding clause wherein the controller is further configured to identify a repeating frame rate as the activation time, and wherein the controlled movement includes a periodic cycle that is aligned with the repeating frame rate.

The system of any preceding clause wherein the periodic cycle repeats at a rate in a range of about 1 cycle per second to about 100 cycles per second.

The system of any preceding clause wherein the designated exposure time is in a range from about 1 ms to about 4 ms.

The system of any preceding clause wherein the operating velocity is in a range of about 1 mm/s to about 50 mm/s.

A method for inspecting a part with a imaging system, the method comprising:identifying an operating velocity of a target element; performing, with an actuator, a controlled movement of an image sensor, the controlled movement being based on an operating velocity of the target element relative to an initial position of the image sensor; setting an activation time to activate the image sensor for a designated exposure time based on the operating velocity and the controlled movement; and activating the image sensor at the activation time.

The method of any preceding clause further comprising: identifying an imaging period of the controlled movement for which a maximum velocity of the image sensor is within a range from about 20% to about 1% of the operating velocity and which has a time length that is greater than the designated exposure time; and setting the activation time to occur within the imaging period such that the designated exposure time expires before an end of the imaging period.