[001] The technical field generally relates to optical systems and methods, and more particularly to system and method for continuous optical inspection of materials, such as objects having a curved surface (e.g. , having a substantially tubular or filiform shape or having a substantially circular cross-section). BACKGROUND

[002] Stranded cables are typically composed of a plurality of cables (i.e. , individual strands) wrapped together or wound around a central cable. The inner layers of the cable are sometimes covered with an adhesive material (e.g. , tar or other similar substances) to enable the individual strands to be insulated from each other while sticking altogether. However, the adhesive material may leak and form defects on the surface of the cable, in between each individual strand. Such defects are likely to cause damage to the cables and may even cause failure of the cables when operated under normal conditions or when submitted to relatively high tension. Therefore, it is important to locate these defects effectively and/or prior use.

[003] Commercially available systems and/or methods for inspecting curved or circular surfaces, such as cables' surface or other object having a substantially circular cross-section, present several drawbacks and limitations, notably in terms of defect identification capability, resolution and/or overall process speed. Various challenges therefore remain in the field of inspecting a circular surface in real time.

SUMMARY

[004] The present description generally relates to systems and methods for continuously imaging an object having a curved or circular surface (i.e. , having a substantially circular cross-section). Some of the present techniques can be particularly useful in the context of identifying and/or locating surface defects while the object is being conveyed.

[005] In one embodiment, the present techniques can be applied to the surface analysis of a curved or circular object (i.e. having a substantially circular cross- section) or implemented in a stranding process that involve stranding and conveying portion(s) of cables, as well as optically inspecting the stranded cables. Such embodiments can be referred to as "optical inspection of curved/circular surface embodiments". [006] In accordance with one aspect, there is provided a system for continuously imaging a surface of an object, the system including a support frame, a drum, an optical assembly and a processor. The drum is mounted to the support frame, the drum having an inner periphery and a hollow body for receiving the object therethrough, the hollow body having an input end section, an output end section, and a central rotation axis extending through the input end section and the output end section, the drum being drivable to rotate about the central rotation axis in a conveying mode. The optical assembly is mounted to the drum, such that the optical assembly rotates along with the drum in the conveying mode. The optical assembly includes a light source configured to generate light toward the inner periphery of the inner hollow portion to illuminate the object, and a detector configured for detecting a resulting light emanating from the object, and producing a signal representative of the resulting light. The processor is operatively connected to the detector, the processor being configured for receiving and processing the signal representative of the resulting light, thereby continuously generating an unwrapped image of the surface of the object and planarly representing the surface of the object.

[007] In some embodiments, the object is conveyed at a feeding speed in the conveying mode and the drum is configured to rotate at an adjustable rotational speed, the adjustable rotational speed being proportional to the feeding speed. [008] In some embodiments, the adjustable rotational speed is included between 0 and 300 RPM.

[009] In some embodiments, the processor is mounted onto the rotatable drum.

[0010] In some embodiments, the support frame includes a fixed holder, the fixed holder including a slip ring, the slip ring being operatively connected to the drum near or at the input end section.

[0011] In some embodiments, the hollow body is cylindrical.

[0012] In some embodiments, the system further includes at least one guiding element configured for supporting and guiding the object in the conveying mode. [0013] In some embodiments, the at least one guiding element is mounted near or at the output end section, and is configured for maintaining the object near a center of the hollow body.

[0014] In some embodiments, the light has a spectral profile including a visible waveband extending from 390 to 800 nm. [0015] In some embodiments, the light source includes a plurality of light-emitting diodes.

[0016] In some embodiments, the light source conforms to a shape of the inner periphery of the drum.

[0017] In some embodiments, the system further includes a diffusing optical component, the diffusing optical component being optically coupled with the light source.

[0018] In some embodiments, the diffusing optical component is a diffusing coating provided on a surface of the inner periphery of the drum.

[0019] In some embodiments, the detector is a line scan camera. [0020] In some embodiments, the line scan camera has an X axis and a width extending along the X axis, the width being about 200 mm and having 2048 pixels along the X axis, such that the line scan camera has a spatial resolution of about 0.1 mm/pixel. [0021] In some embodiments, an acquisition rate of the line scan camera is included between 0 and 2000 lines/second and a bandwidth of the line scan camera is about 4 Mbytes/second.

[0022] In some embodiments, the line scan camera is a monochrome line scan camera. [0023] In some embodiments, the detector is selected from the group consisting of: a 2D optical profiler, a 3D optical profiler, color line scan cameras, a charge coupled device (CCD), and a CMOS camera.

[0024] In some embodiments, a focus, an aperture and a field of view of the detector are each individually adjustable. [0025] In some embodiments, the system further includes a programmable rotary encoder mounted to the drum to clock an image acquisition by the detector.

[0026] In some embodiments, the system further includes a control unit including a servo-motor for driving a rotation of the drum.

[0027] In some embodiments, the control unit includes a microcontroller operatively connected to the light source, the detector and the servo-motor.

[0028] In some embodiments, the drum is placed downstream of a cable stranding machine, the control unit being operatively connected to the stranding machine and being further configured for adjusting the adjustable rotational speed upon reception of information about the object being conveyed. [0029] In some embodiments, the object is a stranded cable and said information includes a pitch of the stranded cable. [0030] In some embodiments, the detector and the processor are combined into a single integrated device.

[0031] In some embodiments, the single integrated device is a smart camera.

[0032] In some embodiments, the light source includes two linear dome light sources and the detector includes two detection modules.

[0033] In some embodiments, the two linear dome light sources are respectively mounted at a first pair of diametrically opposed points of the drum and the first pair of diametrically opposed points defines a first axis, and the two detection modules are respectively mounted at a second pair of diametrically opposed points of the rotatable drum and the second pair of diametrically opposed points defines a second axis, the first axis being substantially perpendicular to the second axis.

[0034] In some embodiments, the processor is configured for identifying a defect on the surface of the object, identifying a number of defects in a portion of the surface of the object, identifying a minimum/maximum size of the defect in the portion of the object, and identifying a quantity of a length of object being conveyed per unit of time.

[0035] In some embodiments, the system is operatively connected to an operation unit, the processor being remotely connected to the operation unit.

[0036] In some embodiments, the system further includes a wireless network card, and the operation unit includes a programmable logic controller, the operation unit being remotely connected to the programmable logic controller through the wireless network card.

[0037] In some embodiments, the operation unit is configured for receiving the signal representative of the resulting light from the processor through the wireless network card and is operable to operate the system upon reception of the signal representative of the emanating light. [0038] In some embodiments, a communication between the processor and the programmable logic controller relies on a communication protocol through an input/output port.

[0039] In some embodiments, the communication protocol is a Modbus TCP/IP protocol.

[0040] In some embodiments, the operation unit further includes an external router and an external computer, the processor being operatively connectable to the external router for transferring results of an analysis from the processor to the router. [0041] In some embodiments, the external computer includes a user interface and a display for displaying the results of the analysis.

[0042] In some embodiments, the resulting light includes diffusely reflected light produced through diffuse reflection of the light off the object.

[0043] In accordance with another aspect, there is provided a system for continuously imaging a surface of a conveyed object, the conveyed object having a pitch and being conveyed at a feeding speed. The system includes a drum, an optical assembly and a processor. The drum drum has an input end section and an output end section, a central rotation axis extending from the input end section to the output end section and defining a conveying path, and a hollow body for receiving the conveyed object along the conveying path at the feeding speed, the hollow body having an inner periphery. The optical assembly is mounted to the drum and is rotatable about the central rotation axis at an adjustable rotational speed, the adjustable rotational speed being proportional to the pitch of the conveyed object and to the feeding speed. The optical assembly includes two light sources and two detectors. The two light sources project light toward the inner periphery of the hollow body and illuminate the conveyed object, the two light sources being respectively mounted at a first pair of diametrically-opposed positions of the hollow body. The two detectors detect resulting light emanating from the conveyed object, and output a signal representative of the resulting light, the two detectors being respectively mounted at a second pair of diametrically- opposed positions of the hollow body. The processor is operatively connected to the two detectors, the processor being configured for receiving the signal representative of the resulting light, and being configured for continuously generating an unwrapped image of the surface of the conveyed object, thereby allowing to planarly represent the surface of the conveyed object.

[0044] In some embodiments, the adjustable rotational speed is included between 0 and 300 RPM. [0045] In some embodiments, the processor is mounted onto the rotatable drum.

[0046] In some embodiments, the support frame includes a fixed holder, the fixed holder including a slip ring, the slip ring being operatively connected to the drum at the input end section.

[0047] In some embodiments, the hollow body is cylindrical. [0048] In some embodiments, the system further includes at least one guiding element configured for supporting and guiding the conveyed object.

[0049] In some embodiments, the at least one guiding element is mounted near or at the output end section, and is configured for maintaining the object near a center of the hollow body. [0050] In some embodiments, the light has a spectral profile including a visible waveband extending from 390 to 800 nm.

[0051] In some embodiments, the two light sources each includes a plurality of light-emitting diodes.

[0052] In some embodiments, each one of the two light sources conforms to a shape of the inner periphery of the drum. [0053] In some embodiments, the system further includes a diffusing optical component, the diffusing optical component being optically coupled with the two light sources.

[0054] In some embodiments, the diffusing optical component is a diffusing coating provided on a surface of the inner periphery of the drum.

[0055] In some embodiments, each one of the two detectors is a line scan camera.

[0056] In some embodiments, the line scan camera has an X axis and a width extending along the X axis, the width being about 200 mm and having 2048 pixels along the X axis, such that the line scan camera has a spatial resolution of about 0.1 mm/pixel.

[0057] In some embodiments, an acquisition rate of the line scan camera is included between 0 and 2000 lines/second and a bandwidth of the line scan camera is about 4 Mbytes/second.

[0058] In some embodiments, the line scan camera is a monochrome line scan camera.

[0059] In some embodiments, each one of the two detectors is selected from the group consisting of: a 2D optical profiler, a 3D optical profiler, color line scan cameras, a charge coupled device (CCD), and a CMOS camera.

[0060] In some embodiments, a focus, an aperture and a field of view of the two detectors are each individually adjustable.

[0061] In some embodiments, the system further includes a programmable rotary encoder mounted to the drum to clock an image acquisition by the two detectors.

[0062] In some embodiments, the system further includes a control unit including a servo-motor for driving a rotation of the drum. [0063] In some embodiments, the control unit includes a microcontroller operatively connected to the two light sources, the two detectors and the servo-motor.

[0064] In some embodiments, the drum is placed downstream of a cable stranding machine, the control unit being operatively connected to the stranding machine and being further configured for adjusting the adjustable rotational speed upon reception of information about the conveyed object.

[0065] In some embodiments, the conveyed object is a stranded cable and said information includes a pitch of the stranded cable.

[0066] In some embodiments, the detector includes two detection modules. [0067] In some embodiments, the first pair of diametrically-opposed positions of the hollow body defines a first axis; and the second pair of diametrically-opposed positions of the hollow body defines a second axis, the first axis being substantially perpendicular to the second axis

[0068] In some embodiments, the processor is configured for identifying a defect on the surface of the conveyed object, identifying a number of defects in a portion of the surface of the conveyed object, identifying a minimum/maximum size of the defect in the portion of the conveyed object, and identifying a quantity of a length of conveyed object per unit of time.

[0069] In some embodiments, the system is operatively connected to an operation unit, the processor being remotely connected to the operation unit.

[0070] In some embodiments, the system further includes a wireless network card, and the operation unit includes a programmable logic controller, the operation unit being remotely connected to the programmable logic controller through the wireless network card. [0071] In some embodiments, the operation unit is configured for receiving the signal representative of the resulting light from the processor through the wireless network card and is operable to operate the system upon reception of the signal representative of the emanating light.

[0072] In some embodiments, a communication between the processor and the programmable logic controller relies on a communication protocol through an input/output port.

[0073] In some embodiments, the communication protocol is a Modbus TCP/IP protocol.

[0074] In some embodiments, the operation unit further includes an external router and an external computer, the processor being operatively connectable to the external router for transferring results of an analysis from the processor to the router.

[0075] In some embodiments, the external computer includes a user interface and a display for displaying the results of the analysis.

[0076] In some embodiments, the resulting light includes diffusely reflected light produced through diffuse reflection of the light off the object.

[0077] In accordance with another aspect, there is provided a method for continuously imaging a surface of an object. The method includes steps of: providing the object within a hollow body of a drum having an inner periphery and a central rotation axis; rotating the drum about the central rotation axis, such that an optical assembly mounted to the drum rotates along with the drum; projecting illumination light towards the inner periphery of drum with the optical assembly; detecting resulting light emanating from the object with the optical assembly; producing a signal representative of the resulting light; processing the signal representative of the resulting light with a processor; and continuously generating an unwrapped image of the surface of the object and planarly representing the surface of the object. [0078] In some embodiments, the object is being conveyed in a conveying mode, and the step of providing the object includes conveying the object along the central rotation axis extending from an input end section to an output end section of the drum. [0079] In accordance with another aspect, there is provided a system for continuously imaging a surface of an object. The system includes a rotatable device, an optical assembly and a processing unit. The rotatable device has an inner hollow portion for receiving the object and has a longitudinal rotation axis. The inner hollow portion has an inner periphery. The optical assembly is mounted onto the rotatable device and is rotatable about the longitudinal rotation axis. The optical assembly includes an illumination unit and a detection unit. The illumination unit projects illumination light toward the inner periphery of the inner hollow portion and illuminates the object. The detection unit detects object light emanating from the object, and outputs optical data representative of the detected object light. The processing unit is operatively connected to the detection unit. The processing unit receives the optical data from the detection unit and continuously generates an unwrapped image of the surface of the object, thereby allowing to planarly represent the surface of the object.

[0080] In accordance with another aspect, there is provided a system for continuously imaging a surface of an object. The system includes a rotatable drum, an optical assembly and a processing unit. The rotatable drum has an inner hollow portion for receiving the object and has a longitudinal rotation axis. The inner hollow portion has an inner periphery. The optical assembly is mounted onto the rotatable device and is rotatable about the longitudinal rotation axis. The optical assembly includes an illumination unit and a detection unit. The illumination unit projects illumination light toward the inner periphery of the inner hollow portion and illuminates the object. The detection unit detects object light emanating from the object, and outputs optical data representative of the detected object light. The processing unit is operatively connected to the detection unit. The processing unit receives the optical data from the detection unit and continuously generates an unwrapped image of the surface.

[0081] In accordance with another aspect, there is provided a system for continuously imaging a surface of a conveyed object. The system includes a rotatable drum, an optical assembly and a processing unit. The rotatable drum has an input end, an output end, a longitudinal rotation axis and an inner hollow portion. The longitudinal rotation axis extends from the input end to the output and defines a conveying path. The inner hollow portion receives the conveyed object along the conveying path at the feeding speed. The inner hollow portion has an inner periphery. The optical assembly is mounted onto the rotatable drum and is rotatable about the longitudinal rotation axis at a rotational speed. The rotational speed is proportional to the pitch of the object and to the feeding speed. The optical assembly includes an illumination unit and a detection unit. The illumination unit projects illumination light toward the inner periphery of the inner hollow portion and illuminates the conveyed object. The detection unit detects object light emanating from the conveyed object, and outputs optical data representative of the detected object light. The processing unit is operatively connected to the detection unit. The processing unit receives optical data from the detection unit and continuously generates an unwrapped image of the surface of the object, thereby allowing to planarly represent the surface of the object.

[0082] In one embodiment, there is provided a rotatable drum such as described herein for use in a system for continuously imaging a surface of an object.

[0083] In one embodiment, the processing unit is mounted onto the rotatable drum.

[0084] In one embodiment, the rotatable drum has a cylindrical body rotatably mounted to an external support frame and the external support frame is stationary.

[0085] In one embodiment, the system further includes a bearing, and the rotatable drum is mounted to the external support frame through the bearing. [0086] In one embodiment, the system further includes a slip ring located near or at the input end of the rotatable drum and operatively connected to the rotatable drum.

[0087] In one embodiment, the system includes a guiding mechanism comprising at least one guiding element for supporting the object.

[0088] In one embodiment, the at least one guiding element is mounted near the output end of the rotatable drum and maintains the object near the center of the inner hollow portion of the rotatable drum.

[0089] In one embodiment, the illumination light emitted by the illumination unit can have a spectrum encompassing an illuminating waveband that lies in the visible range of the electromagnetic spectrum. In such embodiments, the object light emanating from the object is representative of an optical response of the object.

[0090] In one embodiment, the illumination unit is based on light-emitting diodes technology. [0091] In one embodiment, the illumination unit conforms to the inner periphery of the hollow portion of the rotatable drum.

[0092] In one embodiment, the illumination unit comprises a diffusing surface optically coupled with the illumination unit. For example, the diffusing surface could be an acrylic sheet. [0093] In one embodiment, the rotatable drum rotates about the longitudinal rotation axis at a rotational speed along a rotational path, thereby rotatably engaging the optical assembly about the object.

[0094] In one embodiment, the rotational speed is comprised between 0 and 300 RPM. [0095] In one embodiment, the detection unit is a line scan camera. For example, in some variants, the line scan camera has an X axis and a width extending along the X axis. The line scan camera can have a spatial resolution of about 0.1 mm/pixel (i.e. when the width is about 200 mm and has 2048 pixels along the X axis). In some variants, the acquisition rate of the line scan camera is comprised between 0 and 2000 lines/second, for example when a resolution of the camera along the rotational path is about 0.1 mm/line. The acquisition rate can be limited by the geometrical properties of the object, as well as the rotational speed of the rotatable drum. In some variants, the bandwidth of the line scan camera is about 4 Mbytes/second (i.e. 2000 lines/second x 2048 pixels x 1 byte). In some variants, the line scan camera is a monochrome line scan camera. In other variants, the detection unit could be a 2D or a 3D optical profilers, color line scan cameras, a charge coupled device (CCD), a CMOS camera, or any other cameras, devices and/or sensors allowing to detect and visualize the information constituting an image.

[0096] In one embodiment, the focus, aperture and the field of view of the detection unit are individually adjustable.

[0097] In one embodiment, the detection unit is optically coupled with optical components.

[0098] In one embodiment, the rotational speed of the rotatable drum is adjustable and is adjusted according to the geometrical properties of the object, such as its shape and/or dimension.

[0099] In one embodiment, the system comprises a programmable rotary encoder mounted onto the rotatable drum to clock image acquisition. The programmable rotary encoder is in contact with the external support frame and is operatively connected with at least one optocoupler. [00100] In one embodiment, the system includes a control unit including a servomotor for rotating the rotatable drum. [00101] In one embodiment, the control unit includes a microcontroller operatively connected to at least one of the following: the illumination unit, the detection unit and the servo-motor.

[00102] In one embodiment, the detection unit and the processing unit are combined into a single integrated device, such as a smart camera. For example, in some variants, the spectral detection unit and the processing unit can be part of a smart line scan camera.

[00103] In one embodiment, the illumination unit includes two illumination modules and the detection unit includes two detection modules. In some variants, the two illumination modules are mounted at a first pair of diametrically opposed points of the rotatable drum and the first pair of diametrically opposed points defines a first axis. The two detection modules are mounted at a second pair of diametrically opposed points of the rotatable drum and the second pair of diametrically opposed points defines a second axis. [00104] In one embodiment, the first axis is substantially perpendicular to the second axis.

[00105] In one embodiment, the detection unit and the processing unit are two independent interconnected devices.

[00106] In one embodiment, the illumination unit, the detection unit, the processing unit and the control unit are combined into a single integrated device. Alternatively, the illumination unit, the detection unit, the processing unit and the control unit are independent interconnected devices.

[00107] In one embodiment, the processing unit is configured for performing at least one of the following analysis: identifying a defect on the surface of the object, identifying the number of defects in a portion of the surface of the object, identifying the minimum/maximum size of the defect(s) in the portion of the object and/or identifying a quantity of the imaged object per unit of time (i.e. a length of the conveyed object per minute).

[00108] In one embodiment, the system is operatively connected to an operation unit and the processing unit is remotely connected to the operation unit. In some variants, the operation unit includes a programmable logic controller and the operation unit is remotely connected to the programmable logic controller through a wireless network card.

[00109] In one embodiment, the operation unit is configured for receiving the optical data from the processing unit through the wireless network card and is operable to operate the system upon reception of the optical data.

[00110] In one embodiment, results of the analysis are sent from the processing unit to the programmable logic controller using a communication protocol (i.e. Modbus TCP/IP) through an input/output port. Alternatively, the results of the analysis can be sent from the processing unit to the operation unit using discrete signals.

[00111] In one embodiment, the operation unit further includes an external router and an external computer. The processing unit is operatively connectable to the external router. For example, the wireless network card can transfer the results of the analysis from the processing unit to the router. In some variants, the router is operatively connected to the microcontroller, the input/output port and the external computer. In some variants, the external computer includes a user interface and a display for displaying the results of the analysis.

[00112] In one embodiment, the object light includes diffusely reflected light produced by diffuse reflection of the illumination light off the object. [00113] In one embodiment, the system can include a stranding machine for stranding cables near the input end of the rotatable drum. In such embodiments, the object is a stranded cable which is conveyed along the conveying path after being stranded by the stranding machine.

[00114] In one embodiment, the stranded cable is conveyed along the conveying path at a feeding speed and has a stranding pitch. [00115] In one embodiment, the rotational speed of the rotatable drum rotating about the longitudinal rotation axis is proportional to the feeding speed and to the stranding pitch of the stranded cable.

[00116] In one embodiment, the control unit is operatively connected to the stranding machine and is configured for adjusting the rotational speed of the rotatable drum upon reception of information provided by the stranding machine. For example, the rotational speed can be adjusted so as to be proportional to the feeding speed of the stranding machine.

[00117] In one embodiment, the processing unit is configured for adjusting at least one of the following parameter of the analysis: pitch of the stranded cable, diameter of the cable, material(s) forming the cable (e.g. aluminum or copper), maximum size of the defect(s) accepted, defect detection threshold (i.e. minimal size of the defect(s)), statistical analysis to be performed onto the stranded cable and/or acquisition rate or resolution (i.e. in mm/line).

[00118] In accordance with another aspect, there is provided a method for continuously imaging a surface of an object. The method includes steps of providing the object within an inner hollow portion of a rotatable drum having an inner periphery and having a longitudinal rotation axis, rotating the rotatable drum about the longitudinal rotation axis, projecting illumination light towards the inner periphery of the inner hollow portion, rotary detecting object light emanating from the object, and outputting optical data representative of the detected object light, processing the optical data representative of the detected object light, and continuously generating an unwrapped image of the surface of the object, thereby allowing to planarly represent the surface of the object. [00119] In one embodiment, the object is a conveyed object and the step of providing the object includes a sub-step of conveying the object along a conveying path extending from an input end to an output end of the rotatable drum.

[00120] In one embodiment, the detecting step includes detecting the object light as diffusely reflected light. In other embodiments, the detecting step includes detecting the object light as specularly reflected light.

[00121] Other features and advantages of the present description will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[00122] Figures 1 A and 1 B show schematic representations of a front view and a side view of a system for continuously imaging a surface of an object according to one embodiment. [00123] Figures 2A and 2B show different views of a system for continuously imaging a surface of a conveyed object according to one embodiment.

[00124] Figure 3A and 3B illustrate different views of the system of Figure 2.

[00125] Figure 4 shows a schematic representation of a system remotely connected to an operation unit according to one embodiment. [00126] Figure 5 is an unwrapped image of a surface of an object obtained with a system for continuously imaging a surface of an object, according to one embodiment.

[00127] Figures 6A and 6B illustrate images of a defect detected on the surface of a cable. DETAILED DESCRIPTION

[00128] In the following description, similar features in the drawings have been given similar reference numerals, and, to not unduly encumber the figures, some elements may not be indicated on some figures if they were already identified in one or more preceding figures. It should also be understood herein that the elements of the drawings are not necessarily depicted to scale, since emphasis is placed upon clearly illustrating the elements and structures of the present embodiments.

[00129] In the present description, the terms "connected", "coupled", and variants and derivatives thereof, refer to any connection or coupling, either direct or indirect, between two or more elements. The connection or coupling between the elements may be mechanical, physical, optical, operational, electrical, wireless, or a combination thereof.

[00130] In the present description, the expression "optical assembly", "optical system", "imaging assembly", "system", derivatives and variants thereof refer to an apparatus configured to illuminate the surface of an object and acquire images representative of the surface of the object. The optical system could further be understood as a device configured to sense and/or probe light reflected by the surface of the object, according to the needs of a particular application. In the embodiments of the present description presented herein, the optical assembly may provide clear and undistorted images of objects having an outer circular surface.

[00131] In the present description, the terms "light" and "optical", and any variants and derivatives thereof, are intended to refer to electromagnetic radiation in any appropriate region of the electromagnetic spectrum, and are not limited to visible light. For example, in one embodiment, the terms "light" and "optical" may encompass electromagnetic radiation with a wavelength ranging from about 390 to 800 nm. More particularly, although one embodiment of the present techniques can be useful in visible range applications, other embodiments could additionally or alternatively operate in other regions of the electromagnetic spectrum, for example in the millimeter, terahertz, infrared and ultraviolet regions.

[00132] The expression "object having a curved or circular surface" herein encompasses any objects having a substantially tubular, filiform or spherical shape, or having a substantially circular cross-section. More particularly, the expression may refer, but is not limited to any objects whose outer surface has a non-null curvature (i.e., is not flat). In some embodiments, the object is a cable. In other embodiments, the cable is a stranded cable.

[00133] It should be noted that positional descriptors indicating the position or orientation of one element with respect to another element are used herein for ease and clarity of description and should, unless otherwise indicated, be taken in the context of the figures and should not be considered limiting. It will be understood that such spatially relative terms are intended to encompass different orientations in use or operation of the present embodiments, in addition to the orientations exemplified in the figures

[00134] It is also noted, that unless otherwise mentioned, terms such as "substantially" and "about" that modify a value, condition or characteristic of a feature of an exemplary embodiment, should be understood to mean that the value, condition or characteristic is defined within tolerances that are acceptable for proper operation of this exemplary embodiment for its intended application.

[00135] Some embodiments of the present invention may be particularly useful in the field of active imaging (i.e., "continuous" and "real-time" imaging). The embodiments described below are designed for carrying out tasks of material surface inspection, and more particularly non-destructive inspection, testing or evaluation, when, for example, the surface of the object (or the surface of a conveyed object) to be inspected may comprise defects distributed onto its surface. In some implementations, the system may be used in the field of imaging stranding cable suitable for high-voltage application. Alternatively, the system may be used in any other industry wherein active imaging of a circular surface may be useful. In the following description, the expression "real-time imaging" refers to the acquisition of information and/or results that are continuously available for processing, recording and analysis. It is to be noted that the expression "real-time acquisition", or the like, can refer, in some context, to "near real-time acquisition". [00136] The present description generally relates to techniques for optical imagery, defects identification and discrimination of objects based on such defects identification. More particularly, the present techniques generally involve generating an image of the surface of the object and performing statistical analysis on the generated image. [00137] In the present description, the term "object" is meant to encompass broadly any structure, feature or information of interest which is to be imaged using the present systems, methods and techniques. The object can be a cable, a stranded cable, a rope, a fiber, or any other element having an outer circular surface.

[00138] The following expressions will be used throughout the description: - "Strand" refers to multiple wires laid together. The strands can be helically and symmetrically arranged with uniform "pitch";

- "Pitch" (also referred to as "lay length") refers to a distance in a straight line for a wire to make one complete spiral around the center; and

- "Cable" refers to multiple strands laid together helically and being symmetrically arranged, for example in multiple layers with a substantially uniform pitch.

[00139] More particularly, the term "cable" and variants thereof may also be understood herein as any elements having a filiform shape (i.e., having a length substantially larger than a width). In principle, the term "cable" is not meant to be restricted with respect to size, composition or geometrical properties. For example, one embodiment may be suited for imaging cables having a diameter ranging from about 10 to 50 mm, although other sizes may be envisioned in other embodiments. In one embodiment, the cable can be made from aluminum or copper. In some variants, the cable can be a stranded cable (compact-type or compress-type) and comprise, for example 10 to 25 strands. Each strand may have a pitch (i.e., the length that a strand takes to make a complete winding around the cable, i.e., 360 degrees with respect to its cross-section) of about 133 and 320 mm. However, it will be readily understood that the above-mentioned composition, number of strands and pitch of the cables serve as exemplary purposes only, and should not be considered as limitative.

[00140] The object or cables being inspected by the system may be composed of various kinds of materials including, without limitation, metals, alloys, semiconductors, plastics, ceramics, glasses, fibers and/or organic materials.

[00141] The object being inspected can either be imaged while being at rest or in movement (i.e., while being conveyed). In the first case, the object to be imaged will simply be referred to as "object". In the latter case, the system will be said to be in a conveying mode, and the object is then conveyed along a conveying path, as described in greater detail below, and so will be referred to as a "conveyed object". It will be readily understood that the fact that the object is conveyed or not does not put any restrictions onto the embodiments which will be described below, and so the two terms may be used interchangeably.

[00142] Various embodiments of the present techniques, including systems and methods, will now be described with reference to the figures.

System for continuously imaging a surface of an object

[00143] Referring to Figures 1A to 3B, a system 20 for continuously imaging a surface 22 of an object 24 is shown. In nearly all embodiments, the system 20 includes a support frame 26, a drum 27 (sometimes referred to as "a rotatable device"), an optical assembly 34 and a processor 44.

[00144] The drum 27 has a hollow body 28 for receiving the object 24 and a central rotation axis 30 typically passing through the hollow body 28. More particularly, the hollow body 28 has an input end section 50, an output end section 52, and the central rotation axis 30 extends through the input end section 50 and the output end section 52. When operated in the conveying mode, the drum 27 is drivable to rotate about the central rotation axis 30. As it has been previously explained, in the conveying mode, mode, the system 20 is configured to receive a conveyed object 24

[00145] As illustrated, the hollow body 28 also has an inner periphery 32, and the inner periphery 32 has a reflective surface. The reflective surface is made of a material which can provide, for example, a reflection of light, or other types of radiation.

[00146] Depending on the application, and more specifically on the characteristics of the object to be imaged or inspected, the drum 27 can have various dimensions and different geometrical configuration. For example, in some implementations, the drum 27 can have a length that ranges between 20 and 80 cm, and a diameter that ranges between 30 and 150 cm. Of course, other dimensions can be used in other alternative embodiments. For example, in some implementations, the diameter of the rotatable drum can be adjusted in view of a desired length for the conveying path 54.

[00147] In the depicted embodiments, the drum 27 is cylindrical, i.e., has a cylindrical body 46. It will however be readily understood that the drum could alternatively have a different shape or configuration.

[00148] As it has been previously mentioned, the drum 27 further has an input end section 50 and an output end section 52. It is to be noted that the central rotation axis 30 extends from the input end 50 to the output end 52, and hence defines the conveying path 54, i.e., a trajectory followed by the object being conveyed in the hollow body 28 of the drum 27.

[00149] The input end section 50 is configured to supply, inject, dispose, transfer or arrange the object 24 to be characterized onto inner hollow portion 28 of the drum 27. As illustrated, the input end section 50 is an open extremity of the hollow body 28, so as to admit a passage of the object 24 therethrough. In some implementations, the input end 50 may be provided downstream of a stranding machine or a storing unit (not shown, i.e., a cable coil) for storing the objects 24 and supplying the object 24 to the input end 50.

[00150] The output end section 52 is configured to let the object 24 pass after its inspection by the optical assembly 34. As illustrated, the output end section 52 is an open extremity of the hollow body 28, so as to admit a passage of the object 24 therethrough. [00151] In some embodiments, the speed of the conveyed object 24 along the conveying path 54, i.e., through the hollow body 28 from the input end section 50 to the output end section 52 is adjustable. For example, it can range from about 0 to 500 mm/s (i.e., about 0 to 30 m/min). The speed of the conveyed object 24 can be selected so different detectors 40 may be used. [00152] The support frame 26 comprises a fixed holder 56. In some embodiments, the system 20 includes aa slip ring 58. The slip ring 58 is herein refer to as an electromechanical device (and variants thereof) configured for transmitting power and/or other electrical signals from the fixed holder 56 to the drum 27. The slip ring 58 allows to drive the drum 27 in rotation while transmitting power or signals to, for example and without being limitative, the optical assembly 34 and the processor 40 provided on the drum 27. In some embodiments, the slip ring 58 is located near or at the input end 50 of the drum 27. In such a scenario, the slip ring 58 is operatively connected with the drum 27. More particularly, the slip ring 58 is mounted at an interface between a fixed (i.e., stationary) portion of the support frame 26 and a mobile portion of the support frame 26, such that the drum 27 can rotate when driven by appropriate means.

[00153] The system 20 also includes a stand 48. The stand 48 is stationary (i.e., remains in a fixed position, or alternatively, does not rotate), and is configured for supporting, for example and without being limitative, the fixed holder 56, as well as the drum 27, the optical assembly 34 and the processor 40.

[00154] In some embodiments, the system 20 includes at least one guiding element 60 (sometimes referred to as a "guiding mechanism"). The guiding element 60 is configured for guiding and supporting the object 24. For example, the guiding element 62 can be mounted near the output end 52 of the drum 27 and be positioned such that it maintains the object 24 near a center region (for example, the tolerated deviation may be of about +/- 1 mm) of the hollow body 28 of the drum 27. [00155] The configuration and positioning of the guiding element 60 can be advantageous when imaging the object as it is being conveyed, as the guiding element 60 allows stabilizing the object 24 during the optical measurements (i.e., inspection) by the optical assembly 34, which can facilitate locating defects onto the surface 22 of the object 24 by facilitating, for example and without being limitative, the acquisition of a relatively stabilized image.

[00156] The optical assembly 34 is mounted onto the drum 27, such that the optical assembly 34 rotates along with the drum 27 in the conveying mode. More particularly, when the object 24 is conveyed at a feeding speed in the conveying mode, the drum 27 is configured to rotate at an adjustable rotational speed, the adjustable rotational speed being proportional to the feeding speed.

[00157] The optical assembly 34 includes a light source 36. The light source 36 is configured and positioned for generating and projecting light 38 toward the inner periphery 32 of the hollow body 28, hence illuminating the object 24 inside the hollow body 28 or as it is conveyed along the conveying path 54. [00158] The optical assembly 34 also includes a detector 40. The detector 40 is configured and positioned for detecting resulting light 42 emanating from the object 24, and outputting a signal representative of the resulting light 42, after its detection. [00159] In some embodiments, the light has a spectrum encompassing an illuminating waveband that lies, for example, in the visible range of the electromagnetic spectrum. In such embodiments, the resulting light 42 emanating from the object 24 is representative of an "optical response" of the object 24. [00160] In some embodiments, the light source 36 is based on light-emitting diodes technology. Alternatively, different lighting technologies could be used such as, for example, solid-state lighting including lasers, light-emitting diodes (LEDs) and organic LEDs (OLEDs), incandescent lighting, halogen lighting, fluorescent light, and discharge lighting. [00161] The light source 36 can conform to a shape of the inner periphery 32 of the hollow body 28 of the drum 27.

[00162] The system 20 can further comprise a diffusing optical component. The diffusing optical component is optically coupled with the light source 36. In some implementations, the diffusing optical component includes a diffusing surface (not shown). In some embodiments, the diffusing optical surface is a diffusing coating provided on a surface of the inner periphery 32 of the drum 27. In other embodiments, the diffusing optical component could be an acrylic sheet.

[00163] The light source 36 is typically configured for emitting light in a continuous regime. It will however be readily understood that the light source 36 could be operated either in a continuous regime or an intermittent regime, according to one's needs or the targeted applications. Some factors may also influence the configuration of the light source 36, such as the wavelength, power, spatial and spectral profiles of the light 38. In some targeted application, it may be useful to operate the light source 36 so as it generates low power and diffused light 38, which may limit, for example, optical effect (i.e., the formation of hotspots or unwanted light reflection) into the object 24.

[00164] The light source 36 could be coupled to optical components (not shown) configured to alter at least some of the properties of the light 38 prior to its interaction with the object 24. The expression "optical components" herein refers, but is not limited to: lenses, mirrors, filters, and other suitable reflective, refractive and/or diffractive optical components. The position of the light source 36 may also be adjustable, for example if it is required or could be more efficient to control the irradiance of the light 38 on the object 24.

[00165] The detector 40 is configured to detect light 42 emanating from the object upon its irradiation by the light 38. The term "detector", "detection unit" or similar expression broadly refer to any optical detector or combination of optical detectors for measuring light emanating from the object that can be used for optical inspection purposes.

[00166] As used throughout the description, the expression "light emanating from" is herein generally understood as any light which has interacted with the object 24 prior to its detection by detector 40, and so may result from absorption- reemission, fluorescence emission and/or nonlinear optical processes. [00167] In some scenarios, the resulting light 42 may represent a portion of the illumination light 48 that was not totally absorbed by the object 24 and that was at least partially reflected by the object 24.

[00168] Similarly to the light source 36, the detector 40 can comprise or be coupled with optical components which have been previously described for altering the resulting light 42.

[00169] In the conveying mode, the drum 27 rotates about the central rotation axis 30 at a rotational speed along a rotational path 68, thereby rotatably engaging the optical assembly 34 (and so the light source 36 and the detector 40) about the object 24. [00170] In some embodiments, the detector 40 is a line scan camera 64. For example, in some variants, the line scan camera has an X axis and a width extending along the X axis. The line scan camera 64 can have, for example, a spatial resolution of about 0.1 mm/pixel (i.e., when the width is about 200 mm and has 2048 pixels along the X axis). The acquisition rate of the line scan camera can be comprised between 0 and 2000 lines/second, for example when a resolution of the camera along the rotational path is about 0.1 mm/line. The acquisition rate can be limited by the geometrical properties of the object 24, as well as the rotational speed of the drum 27. In some variants, the bandwidth of the line scan camera is about 4 Mbytes/second (i.e. 2000 lines/second x 2048 pixels x 1 byte). In some variants, the line scan camera is a monochrome line scan camera.

[00171] In other implementation, the detection unit could be a 2D or a 3D optical profilers, color line scan cameras, a charge coupled device (CCD), a CMOS camera, or any other cameras, devices and/or sensors allowing to detect and visualize the information constituting an image.

[00172] The drum 27 may comprise at least one slot 66 substantially aligned with at least a portion of the field of view 65 of the line scan camera 64, i.e., the field of view 65 of the line scan camera 64 encompasses the slot 66. In such a scenario, the slot 66 is substantially aligned with the line scan camera 64, as the camera rotates about the longitudinal axis 30.

[00173] In one embodiment, the line scan camera 64 has focus, a field of view 65 and an aperture. The focus, field of view 65 and the aperture of the line scan camera 64 (or any other device embodying the detector 40) are adjustable, according to principles well known by one skilled in the art.

[00174] The resulting light 42 typically includes diffusely reflected light produced by diffuse reflection of the illumination light off the object 24.

[00175] In one embodiment, the rotational speed of the drum 27, (and so of the optical assembly 34, is comprised between 0 and 300 RPM. Of course, this interval may vary according to one's needs or according to the targeted applications. [00176] The system 20 more particularly allows adjusting the rotational speed of the drum 27 according to the geometrical properties of the object 24, such as its shape and/or dimension, and as to accommodate to the properties of the object 24 which have been previously described. [00177] In one embodiment, the light source 36 includes two linear dome light sources 70,72 (sometimes referred to as "illumination modules") and the detector 40 includes two detection modules 74,76. In some variants, the two linear dome light sources 74, 76 are mounted at a first pair of diametrically opposed positions 78,80 of the drum 27 and the first pair of diametrically opposed points defines a first axis 82. The two detection modules are mounted at a second pair of diametrically opposed positions 84,86 of the drum 27 and the second pair of diametrically opposed points defines a second axis 88. In the depicted embodiment, the first axis 82 is substantially perpendicular to the second axis 88.

[00178] In some embodiments, a heat sink 89 is provided onto the drum 27. The heat sink 89 can be in thermal contact with at least one of the following: the light 36, the detector 40 and the processor 44.

[00179] The processor 44 is mounted onto the drum 27 and operatively connected to the detector 40. The processor 44 is configured for receiving a signal representative of the resulting light 42 from the detector 40 and continuously generating an image representative of the surface 22 of the object 24. More particularly, the system 20 allows generating a planar image of the circular surface 22 of the object 24, and so allows generating an "unwrapped image" (e.g. a linear image representing an unwrapped strand of a cable) of the circular surface 22. The "unwrapped image" may help locating the presence of defects on the surface 22 of the object. 24.

[00180] The resulting light 42 is collected and detected by the detector 40 and is then processed (i.e. , converted to electrical data and any other relevant conversion) using techniques already known by one skilled in the art. [00181] In one embodiment, the processor 44 is configured for performing at least one of the following operations: identifying a defect on the surface of the object 24, identifying the number of defects in a portion of the surface 22 of the object 24, identifying the minimum/maximum size of the defect(s) in the portion of the object 24 and/or identifying a quantity of the imaged object 24 per unit of time (i.e., the length of the conveyed object per minute). The general principles underlying such operation are generally well known to one skilled in the art.

[00182] As it will be readily understood, the processor 44 can be implemented as a single unit or as a plurality of interconnected processing sub-units. Also, the processing unit can be embodied by a computer, a microprocessor, a microcontroller, a central processing unit, or by any other type of processing resource or any combination of such processing resources configured to operate collectively as a processing unit. The processor 44 can be implemented in hardware, software, firmware, or any combination thereof, and be connected to the various components of the spectral identification system via appropriate communication ports.

[00183] Still referring to Figures 1A to 3B, the system 20 comprises a programmable rotary encoder 90 mounted onto the drum 27 to clock the image acquisition. The programmable rotary encoder 90 is in contact with the external fixed holder 56 and is operatively connected with at least one optocoupler 92. In some variants, the programmable rotary encoder 90 can be provided with a 24 VDC power supply (not illustrated). Optionally, when the system 20 comprises two linear dome light sources 70,72 and two detection modules 74,76, the system 20 may comprise two optocouplers 92 operatively connected to the programmable rotary encoder 90, for sharing the electrical signal between the two detection modules 74,76.

[00184] The control unit 94 may include a microcontroller 98 operatively connected to at least one of the following: the light source 36, the detector 40 and a servomotor 96. [00185] In some embodiments, the detector 40 and the processor 44 are combined into a single integrated device. For example, in some variants, the detector 40 and the processor 44 can be part of a smart line scan camera 64. Alternatively, the detector 40 and the processor 44 are two independent interconnected devices. [00186] Similarly, in some embodiments, the light source 36, the detector 40, the processor 44 and the control unit 94 are combined into a single integrated device. Alternatively, the light source 36, the detector 40, the processor 44 and the control unit 94 are independent interconnected devices.

[00187] In some embodiments, schematically represented at Figure 4, the system 20 is operatively connected to an operation unit 100. The operation unit is configured for operating the system 20 and/or a production line of the object 24. The processor 44 is remotely connected to the operation unit 100. In some variants, for example, the operation unit 100 includes a programmable logic controller 102 and the operation unit 100 is remotely connected to the processor 44 through a wireless network card 104 (included in the system 20).

[00188] The operation unit 100 is typically configured for receiving the optical data from the processor 44 through the wireless network card 104 and is operable or used to operate the system 20 upon reception of the optical data. For example, in a scenario where a defect is detected on the surface 22 of the object 24, the operation unit 100 may be useful for stopping the system 20 (or the production line of the object 24), which allows a user to interact (i.e. insert a new object or remove the object 24 from the system 20) in a non-hazardous, safe, and efficient manner.

[00189] In one embodiment, the results of the analysis (i.e. , the operations performed by the processor 44) are sent from the processor 44 to the programmable logic controller 102 using a communication protocol (e.g. , Modbus TCP/IP) through an input/output port 106, following steps that are well known by one skilled in the art. Alternatively, the results of the analysis can be sent from the processor 44 to the operation unit 102 using discrete signals. [00190] In one embodiment, the operation unit 100 further includes an external router 108 and an external computer 1 10 operatively connected to the router 108. The processor 44 is operatively connected to the external router 108. For example, the wireless network card 104 can transfer the results of the analysis from the processor 44 to the router 108. In some variants, the router 108 is operatively connected to at least one of the microcontroller 98, the input/output port 106 and the external computer 1 10. In some variants, the external computer 1 10 includes a user interface and a display for displaying the results of the analysis and the image of the surface 22 of the object 24. The external computer 1 10 may allow the user to operate (interact with) the system 20. Such configuration may be useful for the operator controlling, i.e., starting, stopping and/or adjusting parameters of the system 20 or the line of production of the object 24, based on the image displayed on the computer 1 10 screen, as well as selecting properties of the object 24 to be imaged (and the associated required analysis parameters). [00191] In one embodiment, the system 20 can include or be mounted near a stranding machine (not shown) for stranding cables. In such a configuration, the stranding machine is located near the input end section 50 of the drum 27 and the object 24 is a stranded cable which is conveyed along the conveying path 54 after being stranded (i.e. "formed") by the stranding machine. [00192] In one embodiment, the stranded cable is conveyed along the conveying path 54 at a feeding speed and has a stranding pitch. As previously mentioned, the feeding speed of the cable (at the input end 50) is typically comprised between 0 to 500 mm/s, but may of course vary according to some of the characteristics of the object 24. [00193] In one embodiment, the adjustable rotational speed of the drum 27 rotating about the longitudinal rotation axis 30 is proportional to the feeding speed and to the stranding pitch of the stranded cable. [00194] In one embodiment, the operation unit 100 is operatively connected to the stranding machine and is configured for adjusting the rotational speed of the drum 27 upon reception of information provided by the stranding machine.

[00195] In one embodiment, the processor 44 is configured for adjusting at least one of the following parameters of the analysis: pitch of the stranded cable, diameter of the cable, material(s) forming the cable (e.g., aluminum or copper), maximum size of the defect(s) accepted, defect detection threshold (i.e., minimal size of the defect(s)), statistical analysis to be performed onto the stranded cable and/or acquisition rate or resolution (i.e., in mm/line). [00196] As illustrated in Figure 5, the embodiments presented in the current description may be useful for generating a planar image 1 12 of the circular or curved surface of the object, and so allows generating an "unwrapped image" of the circular surface. For example, the planar image 1 12 may be useful to visually inspect the surface of the stranded cable. As presented in Figure 5, the cable is typically composed of a plurality of strand surfaces 1 14, and each strand surface 1 14 is separated from its neighboring strand surface 1 14 by a cavity 1 16.

[00197] As it can be appreciated, the system 20 allows to obtain a clear and relatively undistorted two-dimensional representation a three-dimensional object in real-time or in near real-time. In this regard, the system 20 continuously generates an unwrapped image of the surface of the object being inspected and further planarly represents the surface of the object.

[00198] As illustrated in Figures 6A and 6B, the planar image 1 12 facilitate the visual inspection of the cable. As such, a defect 1 18, which could be, for example and without being limitative, the adhesive material leaking between each of the strand surfaces 1 14 and protruding from the cavity 1 16 may be more easily identified by a visual recognition system or by an operator.

Example of an implementation [00199] In one implementation, the system is configured for continuously imaging a surface of a conveyed object. In such implementation, the conveyed object has a pitch and can be conveyed at a feeding speed. The system includes a drum. The drum has an input end section and an output end section; a central rotation axis extending from the input end section to the output end section and defining a conveying path; and a hollow body for receiving the conveyed object along the conveying path at the feeding speed. The hollow body has an inner periphery.

[00200] In this implementation, the system also includes an optical assembly mounted to the drum. The optical assembly is rotatable about the central rotation axis at an adjustable rotational speed. The adjustable rotational speed is proportional to the pitch of the conveyed object and to the feeding speed. The optical assembly includes two light sources and two detectors. The two light sources project light toward the inner periphery of the hollow body and illuminate the conveyed object. The two light sources are respectively mounted at a first pair of diametrically-opposed positions of the hollow body. The two detectors detect resulting light emanating from the conveyed object and output a signal representative of the resulting light. The two detectors are respectively mounted at a second pair of diametrically-opposed positions of the hollow body.

[00201] The system according to this implementation further includes a processor operatively connected to the two detectors. The processor receives the signal representative of the resulting light, and is configured for continuously generating an unwrapped image of the surface of the conveyed object, thereby allowing to planarly represent the surface of the conveyed object.

Method for continuously imaging a surface of an object [00202] The present description also relates to a method for continuously imaging an object or a cable, as well as a method for continuously imaging a conveyed object (e.g. a cable). Such methods can be performed with the system such as described above. [00203] The method includes steps of providing the object within a hollow body of a drum having an inner periphery and a central rotation axis; rotating the drum about the central rotation axis, such that an optical assembly mounted to the drum rotates along with the drum; projecting light towards the inner periphery of drum with the optical assembly; detecting resulting light emanating from the object with the optical assembly; producing a signal representative of the resulting light; processing the signal representative of the resulting light with a processor; and continuously generating an unwrapped image of the surface of the object and planarly representing the surface of the object. [00204] In some embodiments, the object is being conveyed in a conveying mode, and the step of providing the object includes a sub-step of conveying the object along the central rotation axis extending from an input end section to an output end section of the drum.

[00205] In one implementation, the method includes a step of providing an object within a hollow body of a drum having an inner periphery and having a longitudinal rotation axis.

[00206] In this implementation, the method includes a step of rotating the rotatable drum about the longitudinal rotation axis, and also includes a step of projecting illumination light towards the inner periphery of the inner hollow portion with an optical assembly.

[00207] The method further includes a step of detecting, with a detector, resulting light emanating from the object as the drum and the optical assembly rotates about the longitudinal rotation axis, and outputting a signal or optical data representative of the resulting light. [00208] The method further includes a step of processing the signal or the optical data representative of the resulting light. [00209] The method includes a step continuously generating an unwrapped image of the surface of the object. The above-mentioned step may allow, for example, to planarly represent the surface of the object.

[00210] The detecting step can include detecting the object light as diffusely reflected light. In other embodiments, the detecting step includes detecting the object light as specularly reflected light.

[00211] In some embodiments, the method further includes a step of selecting properties of the object, a step of displaying the image of the surface of the object, and a step of stopping the system if a defect is detected onto the surface of the object.

[00212] Several alternative embodiments and examples have been described and illustrated herein. The embodiments of the invention described above are intended to be exemplary only. A person skilled in the art would appreciate the features of the individual embodiments, and the possible combinations and variations of the components. A person skilled in the art would further appreciate that any of the embodiments could be provided in any combination with other embodiments disclosed herein. It is understood that the invention may be embodied in other specific forms without departing from the central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. Accordingly, while specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the scope of the invention as defined in the appended claims.