Patent Description:
Certain vehicles use cameras to capture images of objects in the environment surrounding the vehicle. These images may be used to identify and/or locate objects within the surrounding environment. However, images captured from a vehicle while the vehicle is in motion may be blurry or distorted, which can result in an inaccurate identification and/or location of the objects. A multi-camera calibration method based on a cylindrical calibration object having a chessboard grid and an annular coded marker is disclosed in Chinese application<CIT>. The annular coded marker is used for determining the positions and the sequence of the cameras.

Aspects of the invention are set out in the independent method claim <NUM> and independent system claim <NUM>, and preferred features are set out in the dependent claims.

According to an embodiment, a method includes capturing, by a camera of an image capturing module, a first image of a target. The image capturing module and a drum are attached to a fixture and the target is attached to the drum. The method also includes determining a number of lateral pixels in a lateral pitch distance of the image of the target, determining a lateral object pixel size based on the number of lateral pixels, and determining a drum encoder rate based on the lateral object pixel size. The drum encoder rate is programmed into a drum encoder attached to the drum. The method further includes capturing, by the camera of the image capturing module, a second image of the target while the target is rotated about an axis of the drum, determining a number of longitudinal pixels in one longitudinal pitch distance of the second image, and comparing the number of lateral pixels to the number of longitudinal pixels. A lateral direction is parallel to the axis of the drum, and a longitudinal direction is perpendicular to the axis.

In certain embodiments, the drum encoder rate is a number of electrical pulses generated by the drum encoder in one revolution of a shaft of the drum encoder. In some embodiments, the drum encoder rate is calculated using a circumference of the drum and the lateral object pixel size. The target may be a checkerboard pattern comprising a plurality of black and white squares, the lateral pitch distance may represent a width of one square of the plurality of squares, and the longitudinal pitch distance may represent a length of the one square of the plurality of squares.

In certain embodiments, the method includes determining, in response to comparing the number of lateral pixels to the number of longitudinal pixels, that the number of lateral pixels matches the number of longitudinal pixels and calculating a vehicle encoder rate based on the drum encoder rate. In some embodiments, the method further includes programming the vehicle encoder rate into a vehicle encoder attached to a wheel of a vehicle and capturing, by the camera of the image capturing module, images of a second target. The image capturing module is attached to the vehicle and the second target is attached to a roadway.

In certain embodiments, the method includes determining, in response to comparing the number of lateral pixels to the number of longitudinal pixels, that the number of lateral pixels is different from the number of longitudinal pixels, adjusting the drum encoder rate to an adjusted drum encoder rate, and programming the adjusted drum encoder rate into the drum encoder. The method further includes capturing, by the camera of the image capturing module, a third image of the target while the target is rotated about an axis of the drum, determining a number of longitudinal pixels in one longitudinal pitch distance of the third image, and comparing the number of lateral pixels to the number of longitudinal pixels in the one longitudinal pitch distance of the third image. In some embodiments, the method includes focusing the camera of the image capturing module on the target under constant lighting conditions and obtaining a maximum contrast between two pixels that identify a boundary of light and dark portions of the target.

According to another embodiment, a system includes a fixture, a drum attached to the fixture, a target attached to the drum, a drum encoder attached to the drum, and an image capturing module attached to the fixture. The image capturing module includes a camera that capture a first image of the target and captures a second image of the target while the target is rotated about an axis of the drum. The system further includes one or more controllers communicatively coupled to the drum encoder and the camera. The one or more controllers determine a number of lateral pixels in a lateral pitch distance of the image of the target, determine a lateral object pixel size based on the number of lateral pixels, and determine a drum encoder rate based on the lateral object pixel size, wherein the drum encoder rate is programmed into the drum encoder attached to the drum. The one or more controllers further determine a number of longitudinal pixels in one longitudinal pitch distance of the second image and compare the number of lateral pixels to the number of longitudinal pixels. A lateral direction is parallel to the axis of the drum, and a longitudinal direction is perpendicular to the axis.

According to yet another embodiment, one or more computer-readable storage media embody instructions that, when executed by a processor, cause the processor to perform operations including capturing, by a camera of an image capturing module, a first image of a target. The image capturing module and a drum are attached to a fixture and the target is attached to the drum. The operations also include determining a number of lateral pixels in a lateral pitch distance of the image of the target, determining a lateral object pixel size based on the number of lateral pixels, and determining a drum encoder rate based on the lateral object pixel size, wherein the drum encoder rate is programmed into a drum encoder attached to the drum. The operations further include capturing, by the camera of the image capturing module, a second image of the target while the target is rotated about an axis of the drum, determining a number of longitudinal pixels in one longitudinal pitch distance of the second image, and comparing the number of lateral pixels to the number of longitudinal pixels.

Technical advantages of certain embodiments of this disclosure may include one or more of the following. This disclosure describes systems and methods for bench calibrating an image capturing module, which may reduce the time and/or personnel required to field calibrate the image capturing module. Certain embodiments of this disclosure use a rotating drum located in a laboratory to simulate a moving roadway, which allows an operator (e.g., a computer programmer) to test the calibration system at full speed with a live image. As such, the systems and methods described herein for bench calibrating an image capturing module may improve the safety and efficiency of field calibration since the time the personnel spends calibrating the image capturing module in the field under dangerous conditions (e.g., working on a roadway and under heavy equipment) is reduced, the number of field personnel is reduced, and the cost of expensive field testing is minimized. The systems and methods described in this disclosure may be generalized to different transportation infrastructures, including railways, roads, and waterways.

Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages.

To assist in understanding the present disclosure, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:.

Certain vehicles include image capturing systems that capture images while the vehicle is in motion. These images may be used by machine vision models to detect and/or locate objects in the environment surrounding the vehicle. Embodiments of this disclosure describe systems and methods for calibrating the image capturing modules and/or rotary encoders used by these systems. These calibration procedures may ensure that the image capturing modules and rotary encoders used in these systems are in synchronization and deliver sharp, high contrast, and properly proportioned images.

<FIG> show example systems and methods for calibrating an image capturing module. <FIG> shows an example system for field calibrating an image capturing module, and <FIG> shows an example image capturing module that may be used by the system of <FIG>. <FIG> shows an example system for bench calibrating an image capturing module. <FIG> shows an example method for field calibrating an image capturing module, and <FIG> shows an example method for bench calibrating an image capturing module and a drum encoder. <FIG> shows an example computer system that may be used by the systems and methods described herein.

<FIG> illustrates an example system <NUM> for field calibrating an image capturing module <NUM>. System <NUM> or portions thereof may be associated with an entity, which may include any entity, such as a business, company (e.g., a railway company, a transportation company, etc.), or a government agency (e.g., a department of transportation, a department of public safety, etc.) that field calibrates image capturing module <NUM>. The elements of system <NUM> may be implemented using any suitable combination of hardware, firmware, and software. For example, the elements of system <NUM> may be implemented using one or more components of the computer system of <FIG>.

System <NUM> includes a vehicle <NUM>, a vehicle encoder <NUM>, a beam <NUM>, one or more image capturing modules <NUM>, a computer <NUM>, a network <NUM>, and a target <NUM>. Vehicle <NUM> of system <NUM> is any machine capable of automated movement. Vehicle <NUM> may be a car, a locomotive, a truck, a bus, an aircraft, or any other machine suitable for mobility. Vehicle <NUM> may operate at any speed that allows one or more components (e.g., sensors, cameras, etc.) of beam <NUM> to capture images. For example, vehicle <NUM> may be a rail bound vehicle that travels at <NUM> miles per hour (mph). Roadway <NUM> of system <NUM> is any path that accommodates vehicle <NUM>. For example, vehicle <NUM> may travel along roadway <NUM>. Roadway <NUM> may include a road, a highway, a railroad track, a water way, and the like.

Vehicle encoder <NUM> of system <NUM> is a rotary encoder or other timing device used to measure axle rotation. Vehicle encoder <NUM> may measure the number of times an axle makes a revolution. Vehicle encoder <NUM> may be attached to an axle of vehicle <NUM>. Vehicle encoder <NUM> may be physically and/or logically connected to one or more components of system <NUM>. For example, vehicle encoder <NUM> may be physically and/or logically connected to one or more cameras and/or sensors of image capturing module <NUM>. As another example, vehicle encoder <NUM> may be physically and/or logically connected to computer <NUM>.

Vehicle encoder <NUM> may communicate with a camera of image capturing module <NUM> via a controller to ensure that the camera captures images of the same perspective and proportion regardless of the speed of travel of vehicle <NUM>. For example, vehicle encoder <NUM> may be synchronized with multiple cameras of image capturing modules <NUM> to ensure that all cameras are taking images at the same time. As another example, vehicle encoder <NUM> may be synchronized with a camera of image capturing module <NUM> to ensure that a camera traveling with vehicle <NUM> at a first speed (e.g., <NUM> miles per hour) captures images that are the same perspective and proportion of a camera traveling with vehicle <NUM> at a second speed (e.g., <NUM> miles per hour).

Beam <NUM> of system <NUM> is a structure that contains and orients components (e.g., image capturing modules <NUM>) used to capture images. In certain embodiments, beam <NUM> operates similar to a flatbed document scanner with the exception that beam <NUM> is in motion while capturing images of stationary physical objects. Beam <NUM> engages with vehicle <NUM>. For example, beam <NUM> may be bolted to a sub-frame attached to vehicle <NUM>. In the illustrated embodiment of <FIG>, beam <NUM> has three sections that include two end sections and a center section. Beam <NUM> has a gullwing configuration such that the center section bends inward toward the center of beam <NUM>. The gullwing configuration allows the image capturing components (e.g., sensors, cameras, etc.) of image capturing modules <NUM> within beam <NUM> to be properly oriented within with respect to the physical objects being captured. In certain embodiments, the center section of beam <NUM> is omitted, and each end section is connected to vehicle <NUM>. Beam <NUM> may be made of metal (e.g., steel or aluminum), plastic, or any other material suitable for housing components of beam <NUM> and for attaching beam <NUM> to vehicle <NUM>.

Beam <NUM> may include one or more openings. Openings may provide for the placement of image capturing modules <NUM> within beam <NUM>. Openings may allow for installation, adjustment, and maintenance of image capturing modules <NUM>. While beam <NUM> is illustrated in <FIG> as having a particular size and shape, beam <NUM> may have any size and shape suitable to house and orient image capturing modules <NUM>. Other factors that may contribute to the design of beam <NUM> include shock resistance, vibration resistance, weatherproofing considerations, durability, ease of maintenance, calibration considerations, and ease of installation.

Image capturing modules <NUM> of system <NUM> are used to capture images while vehicle <NUM> is in motion. Each image capturing module <NUM> may include one or more sensors, one or more cameras, and the like. One or more image capturing modules <NUM> may be attached to vehicle <NUM> at any location that allows image capturing modules <NUM> to capture images of the environment surrounding vehicle <NUM>. In the illustrated embodiment of <FIG>, image capturing modules <NUM> are located within beam <NUM>.

In certain embodiments, each end section of beam <NUM> houses one or more image capturing modules <NUM>. For example, a first end section of beam <NUM> may house image capturing module <NUM> that includes two downward facing cameras that capture images of tie and ballast areas of a rail. The first end section of beam <NUM> may house the two downward facing cameras in a portion of the first end section that is substantially horizontal to the rail. The second end section of beam <NUM> opposite the first end section may house two image capturing modules <NUM> that each include two angled cameras that capture images of both sides of the rail and rail fastening system. The second end section of beam <NUM> may house the four angled cameras in portions of the second end section that are at an angle (e.g., a <NUM> degree angle) to the rail.

Image capturing modules <NUM> may include various types of sensors depending on sensing and/or measuring requirements. Sensors housed by image capturing modules <NUM> may include optical sensors (e.g., cameras for visible light (mono and color), infrared, UltraViolet, and/or thermal), motion sensors (e.g., gyroscopes and accelerometers), light detection and ranging (LIDAR) sensors, hyperspectral sensors, Global Positioning System (GPS) sensors, and the like. Optical sensors and lasers may be used together for laser triangulation to measure deflection or profile. LIDAR sensors may be used for generating three-dimensional (3D) point-cloud data. Hyperspectral sensors may be used for specific wavelength responses. An example image capturing module <NUM> is described in <FIG> below.

Computer <NUM> of system <NUM> represents any suitable computing component that may be used to process information for system <NUM>. Computer <NUM> may coordinate one or more components of system <NUM>. Computer <NUM> may receive data from image capturing modules <NUM> and/or vehicle encoder <NUM>. Computer <NUM> may monitor inputs and/or outputs of image capturing modules <NUM> and/or vehicle encoder <NUM>. Computer <NUM> may include a communications function that allows users (e.g., a technician) to engage system <NUM> directly. For example, a user may access computer <NUM> through an interface (e.g., a screen, a graphical user interface (GUI), or a panel) of computer <NUM>. Computer <NUM> may be a laptop computer, a desktop computer, a smartphone, a tablet, a personal digital assistant, a wearable computer, and the like. Computer <NUM> may be located inside or external to vehicle <NUM>. Computer <NUM> may communicate with one or more components of system <NUM> via network <NUM>.

Network <NUM> of system <NUM> is any type of network that facilitates communication between components of system <NUM>. One or more portions of network <NUM> may include an ad-hoc network, an intranet, an extranet, a virtual private network (VPN), a local area network (LAN), a wireless LAN (WLAN), a wide area network (WAN), a wireless WAN (WWAN), a metropolitan area network (MAN), a portion of the Internet, a portion of the Public Switched Telephone Network (PSTN), a cellular telephone network, a <NUM> network, a <NUM> network, a <NUM> network, a Long Term Evolution (LTE) cellular network, a combination of two or more of these, or other suitable types of networks. One or more portions of network <NUM> may include one or more access (e.g., mobile access), core, and/or edge networks. Network <NUM> may be any communications network, such as a private network, a public network, a connection through Internet, a mobile network, a WI-FI network, a Bluetooth network, etc. One or more components of system <NUM> may communicate over network <NUM>. For example, computer <NUM> may communicate over network <NUM>, including receiving information from image capturing modules <NUM> and/or vehicle encoder <NUM>.

Target <NUM> of system <NUM> is an object used to calibrate image capturing module <NUM> and/or vehicle encoder <NUM>. In certain embodiments, target <NUM> is placed in clear view of image capturing module <NUM>. For example, target <NUM> may be secured to roadway <NUM> (e.g., railroad tracks) in clear view of the camera of image capturing module <NUM>. Target <NUM> includes a calibration pattern. The calibration pattern may be any suitable size, shape, and/or design. The calibration pattern design may include a checkerboard pattern, a chessboard pattern, a circle grid pattern, a ChArUcoboard pattern, and the like. For example, the calibration pattern may be a printed black-and-white checkerboard pattern that includes multiple black and white squares. The calibration pattern may have a pitch between <NUM> inch and <NUM> inches (e.g., <NUM> inch, <NUM> inch, etc.). The pitch represents the length/width of one square of the checkerboard pattern. In certain embodiments, the calibration pattern may include units with an unequal length to width ratio. For example, the length of each unit may be twice as long as the width of each unit.

In operation, a vehicle encoder rate is programmed into vehicle encoder <NUM>. The vehicle encoder rate is a number of electrical pulses generated by vehicle encoder <NUM> in one revolution of a shaft of vehicle encoder <NUM>. The vehicle encoder rate may be determined from calibration data previously generated during bench calibration procedures, as described in <FIG> and <FIG> below. If bench calibration data is not available, an arbitrary initial value for the vehicle encoder rate may be programmed into vehicle encoder <NUM>. In certain embodiments, the vehicle encoder rate that is programmed into vehicle encoder <NUM> is an integer. In certain embodiments, an operator programs the vehicle encoder rate into vehicle encoder <NUM>.

Vehicle encoder <NUM> and image capturing module <NUM> of system <NUM> are secured to vehicle <NUM>. Target <NUM> of system <NUM> is secured to roadway <NUM> in view of the camera of image capturing module <NUM> to be calibrated. Target <NUM> is located perpendicularly to the axis of the camera of image capturing module <NUM>. The camera of image capturing module <NUM> is activated, and an operator observes the current focus of the camera under constant lighting conditions. If the contrast between two pixels identifying the boundary of light and dark portions of target <NUM> is less than a maximum obtainable contrast (or less than observed during bench calibration procedures), the operator unlocks the focus mechanism of the camera and adjusts the focus until a maximum contrast is achieved. The focus mechanism is then locked.

Image capturing module <NUM> is connected to computer <NUM> via network <NUM>. Computer <NUM> includes image capturing software. Image capturing module <NUM> captures a first image of target <NUM>, which is displayed on computer <NUM>. The operator determines a number of lateral (e.g., cross-web) pixels in a lateral pitch distance of the first image of target <NUM> and determines a lateral object pixel size (OPS) by dividing the pitch of target <NUM> by the number of lateral pixels in the pitch region. A trial vehicle encoder rate is then determined by dividing the wheel circumference of vehicle <NUM> by the lateral OPS. If the trial vehicle encoder rate is different than the initial vehicle encoder rate programmed into vehicle encoder <NUM>, the trial vehicle encoder rate is programmed into the vehicle encoder <NUM>. The image capturing software of computer <NUM> is triggered off of vehicle encoder <NUM> and vehicle <NUM> is moved forward or backward over target <NUM>.

Image capturing device <NUM> captures second images of target <NUM> while vehicle <NUM> is moved over target <NUM>. An operator of computer <NUM> determines (e.g., counts) a number of light or dark longitudinal (e.g., down-web) pixels in one longitudinal pitch distance of each of the second images and compares the number of lateral pixels to the number of longitudinal pixels. If the number of lateral pixels matches the number of longitudinal pixels, image capturing module <NUM> and vehicle encoder <NUM> are calibrated. If the number of lateral pixels is different from the number of longitudinal pixels, the vehicle encoder rate is adjusted until number of lateral pixels matches the number of longitudinal pixels. As such, system <NUM> may be used to calibrate image capturing module <NUM> and vehicle encoder <NUM> to ensure sufficient images are captured by system <NUM> that may be used to accurately identify objects in the environment surrounding vehicle <NUM>.

Although <FIG> illustrates a particular arrangement of vehicle <NUM>, vehicle encoder <NUM>, beam <NUM>, image capturing modules <NUM>, computer <NUM>, network <NUM>, and target <NUM>, this disclosure contemplates any suitable arrangement of vehicle <NUM>, vehicle encoder <NUM>, beam <NUM>, image capturing modules <NUM>, computer <NUM>, network <NUM>, and target <NUM>. For example, computer <NUM> may be located inside vehicle <NUM>. Vehicle <NUM>, vehicle encoder <NUM>, beam <NUM>, image capturing modules <NUM>, and computer <NUM> may be physically or logically co-located with each other in whole or in part.

Although <FIG> illustrates a particular number of vehicles <NUM>, vehicle encoders <NUM>, beams <NUM>, image capturing modules <NUM>, computers <NUM>, networks <NUM>, and targets <NUM>, this disclosure contemplates any suitable number of vehicles <NUM>, vehicle encoders <NUM>, beams <NUM>, image capturing modules <NUM>, computers <NUM>, networks <NUM>, and targets <NUM>. For example, system <NUM> may include first beam <NUM> at a front end of vehicle <NUM> and second beam <NUM> at a rear end of vehicle <NUM>. As another example, system <NUM> may include multiple computers <NUM>. One or more components of system <NUM> may be implemented using one or more components of the computer system of <FIG>.

<FIG> illustrates an example image capturing module <NUM> that may be used by system <NUM> of <FIG>. Image capturing module <NUM> includes a camera <NUM>, a lens <NUM>, a top plate <NUM>, a base plate <NUM>, a cover plate <NUM>, bolts <NUM>, and an opening <NUM>. Camera <NUM> is any device that captures images. For example, camera <NUM> may capture images of target <NUM> of <FIG>. As another example, camera <NUM> may capture images of a rail component (e.g., a rail joint, a switch, a frog, a fastener, ballast, a rail head, and/or a rail tie). In certain embodiments, camera <NUM> includes one or more sensors.

One or more cameras <NUM> may capture images from different angles. For example, one or more cameras <NUM> may capture images of both rails of a railway system at any given location. Each beam (e.g., beam <NUM> of <FIG>) may include multiple cameras <NUM>. The beam may include first camera <NUM> aimed straight down to capture an overhead image of a target (e.g., target <NUM> of <FIG>), a physical object, etc. The beam may include second camera <NUM> aimed downward and outward to capture an angled image of the target, a physical object, etc..

Camera <NUM> may be a line scan camera. A line scan camera includes a single row of pixels. Camera <NUM> may be a dual line scan camera. A dual line scan camera includes two rows of pixels that may be captured and/or processed simultaneously. As camera <NUM> moves over a physical object, camera <NUM> may capture images such that a complete image of the physical object can be reconstructed in software line by line. Camera <NUM> may have a capture rate up to <NUM> kilohertz. Camera <NUM> may have a resolution and optics to detect physical objects of at least <NUM>/<NUM> inches in size. In certain embodiments, camera <NUM> includes lens <NUM> that focuses and directs incident light to a sensor of camera <NUM>. Lens <NUM> may be a piece of glass or other transparent substance. Lens <NUM> may be made of any suitable material (e.g., steel, aluminum, glass, plastic, or a combination thereof.

Top plate <NUM> and base plate <NUM> are structural elements used to position, support, and/or stabilize one or more components of image capturing module <NUM> (e.g., camera <NUM> or a sensor). Top plate <NUM> and bottom plate <NUM> may be made of any suitable material (e.g., steel, aluminum, plastic, glass, and the like). Top plate <NUM> may be connected to base plate <NUM> with one or more bolts <NUM>. Bolts <NUM> (e.g., jack bolts) may be used to alter a pitch and/or roll orientation of camera <NUM>. For example, bolts <NUM> may be used to change an effective height between top plate <NUM> and base plate <NUM>. Top plate <NUM> and/or base plate <NUM> may be adjusted to reduce vibration and/or shock of image capturing module <NUM>. Top plate <NUM> and/or base plate <NUM> may include resistive heating elements to provide a warm environment for camera <NUM> and lens <NUM> to operate during cooler weather.

Cover plate <NUM> is a plate that covers base plate <NUM>. Cover plate <NUM> may be made of any suitable material (e.g., glass, steel, aluminum, and the like). Cover plate <NUM> includes an opening <NUM>. Opening <NUM> may serve as an aperture through which a lens of camera <NUM> views the physical object. Opening <NUM> allows for transmission of a sensed signal from the surrounding environment to reach a sensor of camera <NUM>. Opening <NUM> may be any suitable size (e.g., oval, rectangular, and the like) to accommodate views of camera <NUM>. Lens <NUM> of camera <NUM> may be positioned directly over opening <NUM>.

Although <FIG> illustrates a particular arrangement of camera <NUM>, lens <NUM>, top plate <NUM>, base plate <NUM>, cover plate <NUM>, bolts <NUM>, and opening <NUM>, this disclosure contemplates any suitable arrangement of camera <NUM>, lens <NUM>, top plate <NUM>, base plate <NUM>, cover plate <NUM>, bolts <NUM>, and opening <NUM>. Although <FIG> illustrates a particular number of cameras <NUM>, lenses <NUM>, top plates <NUM>, base plates <NUM>, cover plates <NUM>, bolts <NUM>, and openings <NUM>, this disclosure contemplates any suitable number of cameras <NUM>, lenses <NUM>, top plates <NUM>, base plates <NUM>, cover plates <NUM>, bolts <NUM>, and openings <NUM>. For example, image capturing module <NUM> may include multiple cameras <NUM>. As another example, in certain embodiments, image capturing module <NUM> may not include certain components (e.g., base plate <NUM>) illustrated in <FIG>. One or more components of image capturing module <NUM> may be implemented using one or more elements of the computer system of <FIG>.

<FIG> illustrates an example system <NUM> for bench calibrating image capturing module <NUM>. Bench calibration includes calibration procedures where image capturing module <NUM> is calibrated at a bench using calibration devices to simulate the process rather than calibrating image capturing module <NUM> in the field using the actual process itself. System <NUM> simulates a roadway (e.g., roadway <NUM> of <FIG>) moving under image capturing module <NUM>. System <NUM> or portions thereof may be associated with an entity, which may include any entity, such as a business, company (e.g., a railway company, a transportation company, etc.), or a government agency (e.g., a department of transportation, a department of public safety, etc.) that bench calibrates image capturing module <NUM>. The elements of system <NUM> may be implemented using any suitable combination of hardware, firmware, and software. For example, the elements of system <NUM> may be implemented using one or more components of the computer system of <FIG>.

System <NUM> of <FIG> includes image capturing module <NUM>, computer <NUM>, network <NUM>, a fixture <NUM>, a drum <NUM>, a motor <NUM>, a motor controller <NUM>, and a drum encoder <NUM>. Fixture <NUM> of system <NUM> is any structure that is used to support one or more components of system <NUM>. Fixture <NUM> may include one or more frames, panels, braces, fasteners (e.g., screws, bolts, etc.), and the like. One or more components of system <NUM> may be installed on fixture <NUM>. In the illustrated embodiment of <FIG>, image capturing module <NUM>, drum <NUM>, motor <NUM>, motor controller <NUM>, and drum encoder <NUM> are installed on fixture <NUM>.

Image capturing module <NUM> is installed on fixture <NUM> with a fixed working distance between image capturing module <NUM> and target <NUM>. This working distance is a nominal working distance and may vary slightly between different vehicles (e.g., vehicle <NUM> of <FIG>) that utilize image capturing module <NUM>. In certain embodiments, the fixed working distance between image capturing module <NUM> and target <NUM> of <FIG> is substantially (e.g., within five percent) equal to the fixed working distance between image capturing module <NUM> installed on vehicle <NUM> of <FIG> and target <NUM> secured to roadway <NUM> of <FIG>. Image capturing module <NUM> may be physically and/or logically connected to one or more components of system <NUM>. For example, image capturing module <NUM> may be physically and/or logically connected to drum encoder <NUM>. As another example, image capturing module <NUM> may be physically (e.g., via a wired connection) and/or logically (e.g., via network <NUM>) connected to computer <NUM>.

Drum <NUM> of system <NUM> is an object that rotates about axis <NUM>. Drum <NUM> is used to simulate a roadway (e.g., roadway <NUM> of <FIG>) moving under image capturing module <NUM>. Drum <NUM> may be any suitable shape or size that allows rotation about axis <NUM>. In the illustrated embodiment of <FIG>, drum <NUM> is cylindrical in shape. In certain embodiments, axis <NUM> passes through the center of drum <NUM>. Drum <NUM> may rotate about a shaft that is located along axis <NUM>. For example, a cylindrical shaft may be placed along the length (or a portion thereof) of the core of drum <NUM>, and drum <NUM> may rotate among the shaft. Drum <NUM> may be any suitable material (e.g., plastic, metal, wood, fabric, a combination thereof, etc.). For example, drum <NUM> may be a hollow plastic cylinder with a metal cap on each end. The shaft of drum <NUM> may pass through the center of each metal cap.

Target <NUM> of system <NUM> is an object used to calibrate camera <NUM> and/or drum encoder <NUM>. Target <NUM> of system <NUM> is attached to drum <NUM>. Target <NUM> is located coaxially and in synchronization with drum encoder <NUM>. Target <NUM> may be any suitable material (e.g., paper, fabric, plastic, ink, a combination thereof, etc.). In certain embodiments, target <NUM> may be fastened to drum <NUM> using one or more fasteners (e.g., an adhesive, screws, pins, nails, etc.). For example, target <NUM> may be glued to an outside surface or an inside surface of drum <NUM>. In certain embodiments, drum <NUM> is a hollow, clear tube, and target <NUM> is placed on the inside surface of the hollow, clear tube such that target <NUM> is visible from the exterior of drum <NUM>. In some embodiments, target <NUM> is part of drum <NUM>. For example, target <NUM> may be printed directly on drum <NUM>.

Target <NUM> includes a calibration pattern <NUM>. Calibration pattern <NUM> may be any suitable size, shape, and/or design. Calibration pattern <NUM> design may include a checkerboard pattern, a chessboard pattern, a circle grid pattern, a ChArUcoboard pattern, and the like. For example, calibration pattern <NUM> may be a printed black-and-white checkerboard pattern with a pitch between <NUM> inch and <NUM> inches (e.g., <NUM> inch, <NUM> inch, etc.). The pitch represents the length/width of one square of the checkerboard pattern. In certain embodiments, calibration pattern <NUM> may include units with an unequal length to width ratio. For example, the length of each unit may be twice as long as the width of each unit. Calibration pattern <NUM> of target <NUM> is identical to the calibration pattern of target <NUM> of <FIG>. In certain embodiments, target <NUM> and target <NUM> of <FIG> are the same target.

Motor <NUM> of system <NUM> is any machine that initiates the rotation of drum <NUM>. Motor <NUM> may be an alternating current (AC) motor, a direct current (DC) motor, a single phase motor (e.g., <NUM>/<NUM> volt), a three phase motor (e.g., <NUM>/<NUM> volt), etc. Motor may have a revolutions-per-minute (RPM) range of <NUM> to <NUM> (e.g., <NUM>-<NUM>). Motor <NUM> may be physically or logically connected to drum <NUM>. For example, a belt <NUM> may be used to connect motor <NUM> to a rod passing through axis <NUM> of drum <NUM>. Belt <NUM> is used to transmit drive from motor <NUM> to drum <NUM>. Motor <NUM> may be attached to fixture <NUM> at any suitable location. In the illustrated embodiment of <FIG>, motor <NUM> is attached to a base of fixture <NUM>.

Motor controller <NUM> of system <NUM> controls the operation of motor <NUM>. For example, motor controller <NUM> may be used to initiate the rotation of motor <NUM>, adjust the speed of motor <NUM>, and the like. In certain embodiments, motor controller <NUM> is manually operated by one or more users. Motor controller <NUM> may include one or more buttons, switches, displays, touch sensors, GUI), and the like that allow one or more users (e.g., operators, technicians, etc.) to input information. For example, motor controller <NUM> may include an on/off switch that allows a user to turn the motor on and/or off, an up/down button that allows the user to increase/decrease the speed of the motor, and the like. In some embodiments, motor controller <NUM> may be connected to computer <NUM> via network <NUM>, which allows motor controller <NUM> to be operated remotely. Motor <NUM> and motor controller <NUM> drive drum <NUM> at a user selectable rate (e.g., <NUM> to <NUM> miles per hour). In certain embodiments, drum <NUM> is driven in proportion to the maximum speed (e.g., <NUM> or <NUM> mph) of vehicle <NUM> of <FIG>.

Drum encoder <NUM> of system <NUM> is a rotary encoder or other timing device used to measure axle rotation. Drum encoder <NUM> is identical (e.g., same make and model) to vehicle encoder <NUM> used in system <NUM> of <FIG>. Drum encoder <NUM> may measure the number of times an axle makes a revolution. Drum encoder <NUM> may be physically and/or logically connected to one or more components of system <NUM>. For example, drum encoder <NUM> may be physically attached to drum <NUM>. As another example, drum encoder <NUM> may be physically and/or logically connected to image capturing module <NUM>. As still another example, drum encoder <NUM> may be physically (e.g., via a wired connection) and/or logically (e.g., via network <NUM>) connected to computer <NUM>.

In operation, a user (e.g., an operator) installs image capturing module <NUM> (or portions thereof such as camera <NUM> of <FIG>) on fixture <NUM> and connects one or more components of image capturing module <NUM> (e.g., camera <NUM> of <FIG>) to computer <NUM> (e.g., a computer). Computer <NUM> includes image capturing software. The user turns (e.g., switches) on the power of image capturing module <NUM>. The user unlocks the focus locking mechanism of image capturing module <NUM> and focuses a camera of image capturing module <NUM> on target <NUM> under constant lighting conditions. A successful focus is achieved when maximum contrast is obtained between two pixels identifying the boundary of the light and dark portion of calibration pattern <NUM> (e.g., a checkerboard pattern) of target <NUM>. The user then locks the focusing mechanism of image capturing module <NUM>. From an image displayed on computer <NUM>, the user observes a black or white region on target <NUM> in the middle of a field of view <NUM> of the camera of image capturing module <NUM>. Field of view <NUM> may represent an angle through which the camera of image capturing module <NUM> picks up electromagnetic radiation. Field of view <NUM> may be limited by the area of the image displayed on computer <NUM>. The operator of computer <NUM> counts the number of light or dark pixels in direction X for a lateral pitch distance of target <NUM>. In the illustrated embodiment of <FIG>, direction X is parallel to axis <NUM>. A lateral object pixel size (OPS) is calculated by dividing the lateral pitch distance of target <NUM> by the number of pixels in the lateral pitch distance. For example, if the lateral pitch distance of target <NUM> equals one inch and the number of pixels for the one-inch pitch distance of target <NUM> is <NUM>, the OPS equals one inch divided by <NUM>, which equals <NUM> inches per pixel. OPS indicates the true physical dimension represented by one pixel at the prescribed working distance (e.g., the distance between the camera of image capturing module <NUM> and target <NUM>).

Measuring and calibrating the OPS ensures that the objects depicted in images captured by image capturing module <NUM> are properly proportioned and that no data is lost between pixels when image capturing module <NUM> is in field operation. In certain embodiments, the pixels are square or approximately square (e.g., having an equal length and width within a two percent tolerance). An allowance may be permitted due the limitations of the camera of image capturing module <NUM> and/or drum encoder <NUM>.

An encoder rate for drum encoder <NUM> is determined based on the OPS. The drum encoder rate is the number of electrical pulses generated by drum encoder <NUM> in one revolution of the shaft of drum encoder <NUM>. The drum encoder rate is equal to the circumference of drum <NUM> divided by the lateral OPS. For example, if the drum circumference is <NUM> inches for a <NUM> inch diameter drum and the lateral OPS is <NUM> inches, the drum encoder rate is <NUM> inches per revolution divided by <NUM> inches, which equals <NUM> pulses (pixels) per revolution.

In certain embodiments, the drum encoder rate is programmed into drum encoder <NUM> as an integer value. For example, drum encoder <NUM> may be programmed to <NUM> or <NUM> pulses per revolution. The user may set motor controller <NUM> to rotate drum <NUM> at a low speed. The low speed may be within a range of five to twenty mph (e.g., <NUM> mph). Image capturing module <NUM> collects images while drum <NUM> is rotating at the low speed and communicates the collected images to computer <NUM>. The operator of computer <NUM> determines (e.g., counts) the number of light or dark pixels in direction Y in one longitudinal pitch distance on target <NUM>. In the illustrated embodiment of <FIG>, direction Y is perpendicular to axis <NUM>.

The user then sets motor controller <NUM> to rotate drum <NUM> at a high speed. The high speed may be within a range of fifty to eighty miles per hour (mph) (e.g., <NUM> mph). The high speed may represent the maximum speed of vehicle <NUM> of <FIG>. Image capturing module <NUM> collects images while drum <NUM> is rotating at the high speed and communicates the collected images to computer <NUM>. The operator of computer <NUM> determines (e.g., counts) the number of light or dark pixels in one pitch distance on target <NUM> in longitudinal direction Y. The high and low speed longitudinal pixel counts are compared to the lateral pixel counts to determine if the camera pixels are representing physical space equally in the lateral and longitudinal directions. If the longitudinal pixel counts are different than the lateral pixel counts, a different drum encoder rate may be programmed into drum encoder <NUM>, and the above process may be repeated to compare the effects of the new drum encoder rate on the pixel counts in the lateral and longitudinal directions.

The drum encoder rate that generates the closest square pixel is then recorded and assigned to image capturing module <NUM>. If the wheel diameter of vehicle <NUM> of <FIG> is known, the vehicle encoder rate for vehicle <NUM> can then be calculated. The vehicle encoder rate is the number of electrical pulses generated by vehicle encoder <NUM> in one revolution of the shaft of vehicle encoder <NUM>. The vehicle encoder rate is equal to the wheel circumference of vehicle <NUM> of <FIG> divided by the drum circumference of drum <NUM> multiplied by the drum encoder rate. For example, if the wheel circumference of vehicle <NUM> is <NUM> inches, the drum circumference of drum <NUM> is <NUM> inches, and the drum encoder rate is <NUM> inches per revolution, the vehicle encoder rate is <NUM> inches divided by <NUM> inches times <NUM> pulses per revolution, which equals <NUM> pulses per revolution. A user may program the vehicle encoder rate into vehicle encoder <NUM> of system <NUM> of <FIG>, which may reduce the time and/or resources required to field calibrate image capturing module <NUM>.

Although <FIG> illustrates a particular arrangement of image capturing module <NUM>, computer <NUM>, network <NUM>, fixture <NUM>, drum <NUM>, motor <NUM>, motor controller <NUM>, and drum encoder <NUM>, this disclosure contemplates any suitable arrangement of image capturing module <NUM>, computer <NUM>, network <NUM>, fixture <NUM>, drum <NUM>, motor <NUM>, motor controller <NUM>, and drum encoder <NUM>. For example, motor <NUM> and motor controller <NUM> may be a single component. Image capturing module <NUM>, computer <NUM>, fixture <NUM>, drum <NUM>, motor <NUM>, motor controller <NUM>, and drum encoder <NUM> may be physically or logically co-located with each other in whole or in part.

Although <FIG> illustrates a particular number of image capturing modules <NUM>, computers <NUM>, networks <NUM>, fixtures <NUM>, drums <NUM>, motors <NUM>, motor controllers <NUM>, and drum encoders <NUM>, this disclosure contemplates any suitable number of image capturing modules <NUM>, computers <NUM>, networks <NUM>, fixtures <NUM>, drums <NUM>, motors <NUM>, motor controllers <NUM>, and drum encoders <NUM>. For example, system <NUM> may include first computer <NUM> communicatively coupled to image capturing module <NUM> and a second computer <NUM> communicatively coupled to drum encoder <NUM>. One or more components of system <NUM> may be implemented using one or more components of the computer system of <FIG>.

<FIG> illustrates an example method <NUM> for field calibrating an image capturing module. Method <NUM> begins at step <NUM>. At step <NUM>, a camera of an image capturing module (e.g., camera <NUM> of image capturing module <NUM> of <FIG>) captures a first image of a target (e.g., target <NUM> of <FIG>). The image capturing module may be secured to a vehicle (e.g., vehicle <NUM> of <FIG>) and the target may be secured to a roadway (e.g., roadway <NUM> of <FIG>). The target is perpendicular to the axis of the camera of the image capturing module. Method <NUM> then moves from step <NUM> to step <NUM>. The image captured by the camera of the image capturing module may be displayed on a computer (e.g., computer <NUM> of <FIG>) communicatively coupled to the image capturing module.

At step <NUM> of method <NUM>, an operator determines a number of lateral pixels in a lateral pitch distance of the image of the target. For example, the operator may observe the current focus of the camera under constant lighting conditions. If the contrast between two pixels identifying the boundary of light and dark portions of the focus target is less than observed in bench testing, the operator may unlock the focus mechanism and adjust the focus until a satisfactory result is obtained. The focus mechanism is then locked. The operator may then count the number of light or dark pixels in a lateral pitch distance of the target at the center of the camera's field of view. Method <NUM> then moves from step <NUM> to step <NUM>.

At step <NUM> of method <NUM>, a lateral OPS is determined using the determined number of lateral pixels. For example, the operator may calculate the lateral OPS by dividing the pitch (e.g., one inch) of target <NUM> by the number of lateral pixels in the pitch region. Method <NUM> then moves from step <NUM> to step <NUM>, where a vehicle encoder rate is determined based on the lateral OPS. programmed into an encoder (e.g., vehicle encoder <NUM> of <FIG>) of a vehicle (e.g., vehicle <NUM> of <FIG>). The vehicle encoder rate is equal to the wheel circumference of vehicle <NUM> of <FIG> divided by the lateral OPS. The vehicle encoder has been set to an initial vehicle encoder rate, which was either determined during a bench calibration procedure or determined arbitrarily. If the calculated vehicle encoder rate is different than the initial vehicle encoder rate previously programmed into the vehicle encoder, then the calculated encoder rate is programmed into the vehicle encoder. Method <NUM> then moves from step <NUM> to step <NUM>.

At step <NUM>, the camera of the image capturing module captures a second image of the target while the vehicle is moved forward or backward over the target. For example, a train operator may move one or more portions of the train (e.g., a locomotive) along the railroad track such that the image capturing module attached to the train passes over a target secured to the railroad track. Method <NUM> then moves from step <NUM> to step <NUM>.

At step <NUM> of method <NUM>, the operator determines a number of longitudinal pixels in one longitudinal pitch distance of the second image of the target. Method <NUM> then moves from step <NUM> to step <NUM>, where the operator determines whether the number of lateral pixels in the first image match the number of longitudinal pixels in the second image. If the number of lateral pixels in the first image match the number of longitudinal pixels in the second image, method <NUM> moves from step <NUM> to step <NUM>, where an operator determines, based on the comparison, that the image capturing module is calibrated.

If, at step <NUM>, the operator determines that the number of lateral pixels in the first image is different than the number of longitudinal pixels in the second image, method <NUM> moves from step <NUM> back to step <NUM>, where an operator adjusts the vehicle encoder rate to account for the discrepancy and programs the new vehicle encoder rate into the vehicle encoder. Steps <NUM> through <NUM> are repeated until the number of lateral pixels in the first image matches the number of longitudinal pixels in the third image (or the fourth image and so on as required). When the number of lateral and longitudinal pixels match, method <NUM> moves from step <NUM> to step <NUM>, where the operator determines, based on the comparison, that the image capturing module is calibrated. Method <NUM> then moves from step <NUM> to step <NUM>, where method <NUM> ends.

Modifications, additions, or omissions may be made to method <NUM> depicted in <FIG>. Method <NUM> may include more, fewer, or other steps. For example, method <NUM> may include programming the initial vehicle encoder rate into the vehicle encoder. As another example, method <NUM> may include activating the camera of the image capturing module. Steps may be performed in parallel or in any suitable order. While discussed as specific components completing the steps of method <NUM>, any suitable component may perform any step of method <NUM>.

<FIG> illustrates an example method <NUM> for bench calibrating an image capturing module. Method <NUM> begins at step <NUM>. At step <NUM>, a camera of an image capturing module (e.g., camera <NUM> of image capturing module <NUM> of <FIG>), a drum (e.g., drum <NUM> of <FIG>), and a motor (e.g., motor <NUM> of <FIG>) are attached to a fixture (e.g., fixture <NUM> of <FIG>). Method <NUM> then moves from step <NUM> to step <NUM>, where a target (e.g., target <NUM> of <FIG>) is fastened to the drum. The target is located coaxially and in synchronization with a drum encoder (e.g., drum encoder <NUM> of <FIG>). The image capturing module is installed in the fixture with a fixed working distance between the camera and the target. This working distance is a nominal working distance and may vary slightly between different vehicles that utilize image capturing module <NUM>. Method <NUM> then moves from step <NUM> to step <NUM>.

At step <NUM>, the camera captures a first image of the target. The camera may be connected to a computer (e.g., computer <NUM> of <FIG>) that includes image capturing software. The first image may be an image in the middle of the camera's field of view that is observed by an operator by using the computer. Method <NUM> then moves from step <NUM> to step <NUM>, where a number of lateral pixels in a lateral pitch distance of the image of the target is determined. For example, an operator may count, using the first image displayed on the computer, the number of light or dark pixels in a lateral pitch distance of the target at the center of the camera's field of view. Method <NUM> then moves from step <NUM> to step <NUM>.

At step <NUM> of method <NUM>, a lateral OPS is determined using the determined number of lateral pixels. The lateral OPS is calculated by dividing the pitch (e.g., one inch) of target <NUM> by the number of lateral pixels in the pitch region. Method <NUM> then moves from step <NUM> to step <NUM>, where a drum encoder rate is programmed into a drum encoder (e.g., drum encoder <NUM> of <FIG>) of the drum. The drum encoder rate is equal to the circumference of drum <NUM> divided by the lateral OPS. Method <NUM> then moves from step <NUM> to step <NUM>, where the drum encoder rate is programmed into the drum encoder. In certain embodiments, the drum encoder is programmed with an integer value representing the drum encoder rate. Method <NUM> then moves from step <NUM> to step <NUM>.

At step <NUM> of method <NUM>, the motor controller is set to rotate the drum at a low speed (e.g., <NUM> mph). Method <NUM> then moves from step <NUM> to step <NUM>, where the camera of the image capturing module captures one or more images of the target while the drum is rotated at the low speed. Method <NUM> then moves from step <NUM> to step <NUM>, where a number of longitudinal pixels in one longitudinal pitch distance of each image is determined. For example, each image may be displayed on the computer, and an operator may count the number of dark or light pixels in one pitch distance in the longitudinal section of each image. Method <NUM> then moves from step <NUM> to step <NUM>.

At step <NUM>, the motor controller is set to rotate the drum at a high speed (e.g., <NUM> mph). Method <NUM> then moves from step <NUM> to step <NUM>, where the camera of the image capturing module captures one or more images of the target while the drum is rotated at the high speed. Method <NUM> then moves from step <NUM> to step <NUM>, where a number of longitudinal pixels in one longitudinal pitch distance of each image is captured while the drum is rotating at the high speed is determined. For example, each image may be displayed on the computer, and an operator may count the number of dark or light pixels in one pitch distance in the longitudinal section of each image. Method <NUM> then moves from step <NUM> to step <NUM>.

At step <NUM>, the operator determines whether the number of lateral pixels in the first image match the number of longitudinal pixels in the images captured while the drum was rotating at the low and high speeds. If the number of lateral pixels in the first image match the number of longitudinal pixels in the low/high speed images, method <NUM> moves from step <NUM> to step <NUM>, where the vehicle encoder rate is calculated using the drum encoder rate. The vehicle encoder rate is equal to the wheel circumference of vehicle <NUM> of <FIG> divided by the drum circumference of drum <NUM> of <FIG> and then multiplied by the drum encoder rate. Method <NUM> then moves from step <NUM> to step <NUM>, where method <NUM> ends.

If, at step <NUM>, the number of lateral pixels in the first image is different than the number of longitudinal pixels in the low/high speed images, method <NUM> moves from step <NUM> back to step <NUM>, where the drum encoder rate is adjusted to account for the discrepancy. The adjusted drum encoder rate is programmed into the drum encoder. Steps <NUM> through <NUM> are repeated until the number of lateral pixels in the first image matches the number of longitudinal pixels in the low/high speed images. When the number of lateral and longitudinal pixels match, method <NUM> moves from step <NUM> to step <NUM>, where the vehicle encoder rate is calculated using the adjusted drum encoder rate. Method <NUM> then moves from step <NUM> to step <NUM>, where method <NUM> ends.

Modifications, additions, or omissions may be made to method <NUM> depicted in <FIG>. Method <NUM> may include more, fewer, or other steps. For example, method <NUM> may include activating the camera of the image capturing module. Steps may be performed in parallel or in any suitable order. While discussed as specific components completing the steps of method <NUM>, any suitable component may perform any step of method <NUM>. For example, one or more steps of method <NUM> may be automated (e.g., performed by computer <NUM> of <FIG>).

<FIG> shows an example computer system that may be used by the systems and methods described herein. For example, one or more components (e.g., computer <NUM>) of system <NUM> of <FIG> and/or system <NUM> of <FIG> may include one or more interface(s) <NUM>, processing circuitry <NUM>, memory(ies) <NUM>, and/or other suitable element(s). Interface <NUM> receives input, sends output, processes the input and/or output, and/or performs other suitable operation. Interface <NUM> may comprise hardware and/or software.

Processing circuitry <NUM> performs or manages the operations of the component. Processing circuitry <NUM> may include hardware and/or software. Examples of a processing circuitry include one or more computers, one or more microprocessors, one or more applications, etc. In certain embodiments, processing circuitry <NUM> executes logic (e.g., instructions) to perform actions (e.g., operations), such as generating output from input. The logic executed by processing circuitry <NUM> may be encoded in one or more tangible, non-transitory computer readable media (such as memory <NUM>). For example, the logic may comprise a computer program, software, computer executable instructions, and/or instructions capable of being executed by a computer. In particular embodiments, the operations of the embodiments may be performed by one or more computer readable media storing, embodied with, and/or encoded with a computer program and/or having a stored and/or an encoded computer program.

Memory <NUM> (or memory unit) stores information. Memory <NUM> may comprise one or more non-transitory, tangible, computer-readable, and/or computer-executable storage media. Examples of memory <NUM> include computer memory (for example, RAM or ROM), mass storage media (for example, a hard disk), removable storage media (for example, a Compact Disk (CD) or a Digital Video Disk (DVD)), database and/or network storage (for example, a server), and/or other computer-readable medium.

Embodiments of the present disclosure are directed to systems and methods for capturing, by a camera of an image capturing module, a first image of a target. The image capturing module and a drum are attached to a fixture and the target is attached to the drum. The method also includes determining a number of lateral pixels in a lateral pitch distance of the image of the target, determining a lateral object pixel size based on the number of lateral pixels, and determining a drum encoder rate based on the lateral object pixel size. The drum encoder rate is programmed into a drum encoder attached to the drum. The method further includes capturing, by the camera of the image capturing module, a second image of the target while the target is rotated about an axis of the drum, determining a number of longitudinal pixels in one longitudinal pitch distance of the second image, and comparing the number of lateral pixels to the number of longitudinal pixels.

Herein, a computer-readable non-transitory storage medium or media may include one or more semiconductor-based or other integrated circuits (ICs) (such as field-programmable gate arrays (FPGAs) or application-specific ICs (ASICs)), hard disk drives (HDDs), hybrid hard drives (HHDs), optical discs, optical disc drives (ODDs), magneto-optical discs, magneto-optical drives, floppy diskettes, floppy disk drives (FDDs), magnetic tapes, solid-state drives (SSDs), RAM-drives, SECURE DIGITAL cards or drives, any other suitable computer-readable non-transitory storage media, or any suitable combination of two or more of these, where appropriate.

Claim 1:
A method, comprising:
capturing (<NUM>), by a camera (<NUM>) of an image capturing module (<NUM>), a first image of a target (<NUM>), wherein:
the image capturing module (<NUM>) and a drum (<NUM>) are attached to a fixture (<NUM>), wherein the drum (<NUM>) is adapted to rotate about an axis (<NUM>) such as to simulate a roadway (<NUM>) moving under the image capturing module (<NUM>); and
the target (<NUM>) is attached to the drum (<NUM>), wherein the target (<NUM>) includes a calibration pattern (<NUM>);
determining (<NUM>) a number of lateral pixels in a lateral pitch distance of the image of the target (<NUM>);
determining (<NUM>) a lateral object pixel size based on the number of lateral pixels;
determining (<NUM>) a drum encoder rate based on the lateral object pixel size, wherein the drum encoder rate is programmed into a drum encoder (<NUM>) attached to the drum (<NUM>), wherein the drum encoder rate corresponds to a number of electrical pulses generated by the drum encoder (<NUM>) in one revolution of a shaft of the drum encoder (<NUM>), or the drum encoder rate is calculated using a circumference of the drum (<NUM>) and the lateral object pixel size;
capturing (<NUM>), by the camera (<NUM>) of the image capturing module (<NUM>), a second image of the target (<NUM>) while the target is rotated about the axis (<NUM>) of the drum (<NUM>);
determining (<NUM>) a number of longitudinal pixels in a longitudinal pitch distance of the second image; and
comparing (<NUM>) the number of lateral pixels to the number of longitudinal pixels and determining (<NUM>), based on the comparison, that the image capturing module (<NUM>) is calibrated;
wherein a lateral direction (X) is parallel to the axis (<NUM>) of the drum (<NUM>), and a longitudinal direction (Y) is perpendicular to the axis (<NUM>).