CLAIM OF PRIORITY

[0001] This patent application claims the benefit of priority to U.S.

Provisional Application Serial No. 62/898,333, filed September 10, 2019, which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

[0002] This disclosure relates to signal transfer between a rotary and a stationary device, in particular, optical non-contact signal transfer.

BACKGROUND

[0003] Many industrial, medical, and other systems involve data transfer between rotating and stationary components. For example, in a pipe inspection system as used, e.g., in steel mills to inspect pipes for cracks, wall thickness variations, laminations or other tube defects, the pipe may be fed through a barrow that rotates around the pipe hundreds of rounds per minute, carrying electromagnetic induction or ultrasound equipment for performing the inspection measurements that is controlled by electrical signals from a stationary control system. As another example, in a computed tomography system, a patient may be irradiated from multiple angles using an x-ray or other radiation source that rotates around the patient, controlled by a stationary computer. A standard approach for establishing communication between the rotating and stationary devices in such scenarios is to use slip rings that either make mechanical contact between the rotating and stationary components, e.g., by means of carbon brushes, or that couple the two components inductively. This approach is usually limited to analog signal exchange and low data rates. Further, it tends to be maintenance-intense, especially for mechanical slip rings, where reliable signal transfer is contingent on clean contact surfaces. SUMMARY

[0004] Disclosed herein is an optical rotary communication system that uses light emitted along a radial direction with respect to a rotational axis of a rotary device to transfer analog or digital signals between the rotary device and a stationary device in a contactless manner, substantially reducing maintenance requirements as compared with contact-based systems and facilitating higher data rates than conventionally achieved.

[0005] The communication system generally includes one or more light- emitting devices (e.g., light-emitting diodes (LEDs)) driven by suitable electronic transmission circuitry and one or more light-sensing devices (e.g., photodiodes) along with associated electronic receiver circuitry for processing photocurrents generated upon exposure of the light-sensing devices to light. The light-emitting device(s) may be mounted on and rotate along with the rotary device, with the light-sensing device(s) being stationary (e.g., mounted on the stationary device); or, alternatively, the light-emitting device(s) may be stationary and the light-sensing device(s) mounted on the rotary device. Further, the rotary device may be placed interior to the stationary device or surround the stationary device, depending on the particular application and context. Light- emitting and light-sensing devices are arranged in the same plane transverse to the rotational axis and face in mutually opposite radial directions; that is, if the light-emitting device(s) face and emit light radially inward, the light-sensing device(s) face radially outward to detect the light, or vice versa. In this manner, each light-emitting device faces each light-sensing device, and thereby establishes a line of sight with that light-sensing device, at some point during a full rotation. As will be appreciated, depending on where the light-emitting devices and light-sensing devices are located, signal transfer is enabled from the rotary device to the stationary device or from the stationary device to the rotary device. In some embodiments, two sets of light-emitting devices, one on the rotary device and one on the stationary device, are paired with two corresponding sets of light-sensing devices, one on the stationary device and one on the rotary device, respectively, to allow for bidirectional communication. [0006] In some embodiments, continuous signal transfer is facilitated by an array of light-emitting devices, driven in unison, that fully extends around a circumference of a circle centered at the rotary axis, in conjunction with a single light-sensing device or array of light-sensing devices. The light- emitting device may, for instance, be mounted around a circumference of the rotary device, or the circumference of a stationary device that is arranged coaxially with the rotary device. The array of light-emitting devices may be configured, e.g., in terms of spacings between the individual devices, to ensure that, for any rotational position of the rotary device, at least one of the light- emitting devices is in optical communication with the light-sensing device(s); conditions on the configuration of the array of light-emitting devices can be relaxed if an array of multiple light-sensing devices (e.g., arranged along a circle concentric with the array of light-emitting devices) is used. As will be appreciated by those of ordinary skill in the art, the roles of light-emitting and light-sensing devices can also be reversed by using an array of light-sensing devices extending around the circumference of a circl e centered at the rotary axis and wired in parallel to additively combine their photocurrents in conjunction with one or more light-emitting devices, even though an array of light-emitting devices may be easier to drive, and thus simplify the electronic circuitry, as compared with an array of light-sensing devices. Further, in some embodiments, the light-emitting and light-sensing devices both extend only partially around the circumference.

BRIEF DESCRIPTION OF THE DRAWINGS [0007] The foregoing will be more readily understood from the following description of various example embodiments as depicted in the accompanying drawings, in which:

[0008] FIGS. 1 A and IB are perspective and cross-sectional views, respectively, of an example rotary communication system in which a ring array of light-emitting devices on a rotary device transfers signals to a light-sensing device on a stationary device, in accordance with various embodiments;

[0009] FIGS. 2A and 2B are perspective and cross-sectional views, respectively, of an example rotary communication system in which a ring array of light-emitting devices on a stationary device transfers signal s to a light sensing device on a rotary device, in accordance with various embodiments; [0010] FIG. 3 is a schematic circuit diagram illustrating an electronic transmission module in accordance with various embodiments; and [0011] FIG. 4 is a schematic circuit diagram illustrating an electronic receiver module in accordance with various embodiments.

DESCRIPTION

[0012] This disclosure pertains to optical rotary communication systems that can be used in many systems where signals are to be transferred between a rotating system component and stationary system component. One example is a pipe inspection system where ultrasonic, electromagnetic, or other inspection equipment is mounted on a fast-rotating barrow surrounding a concentrically placed pipe, allowing the pipe to be inspected from all directions as it is moved along its longitudinal axis through the barrow. A stationary computer or other processing system may be communicatively coupled to the equipment to provide control signals and/or exchange data. Such coupling can be achieved optically, in accordance herewith, using a receiver or transmitter module located on and rotating with the barrow and a stationary transmitter or receiver module to facilitate signal transfer from the stationary computer to the rotating barrow or from the rotating barrow to the stationary computer, respectively. Similarly, rotary communication systems may find application in medical apparatus (e.g., for medical imaging or radiation therapy) rotating around a patient, wind turbines, helicopters, carousels, and many others.

[0013] FIGS. 1 A and IB illustrate, in perspective and cross-sectional views, an example system configuration 100 for optically transferring signals from a rotary device 102 to a stationary device 106. The configuration 100 includes, beyond the rotary and stationary devices 102, 106, a rotary, non- contact communication system including an array 108 of light-emitting devices 114 and an array 110 of (one or more) light-sensing devices 120, as well as associated electronic transmission and receiver circuitry (not shown).

[0014] In FIG. 1 A, the rotary device 102 is shown as a tubular cylindrical structure, which rotates about a rotational axis 104. In a non-limiting example, the rotary device 102 may be a rotating barrow as used in a pipe inspection system, e.g., with a diameter between twenty centimeters and two meters. The stationary device 106 is placed next to the rotary device 102; it may include, e.g., a controller for operating equipment on the rotary device 102. [0015] The light-emitting devices 114 may he, e.g., light-emitting diodes

(LEDs), or other devices capable of converting an applied electrical current into light, such as light-emitting transistors, laser diodes, etc. The light-sensing devices 120 may be, e.g., photodiodes, or other devices that create electrical signals (e.g., photocurrents) when exposed to light, such as phototransistors or photoconductive detectors. For specificity, the following discussion references example implementations using LEDs and photodiodes, and therefore refers to the array 108 of light-emitting devices 114 also as the “transmission LED array (TLA)” and to the array 110 of light-sensing devices 120 also as the “receiving photodiode array (RPA).” It should be understood, however, that other types of light-emitting and light-sensing devices may be substituted for the LEDs and photodiodes.

[0016] As can be seen in FIG. 1 A, the TLA 108 and RPA 110 are mounted on the rotary device 102 and stationary device 106 in a shared plane 112 perpendicular to the rotational axis 104. A cross-section of the system configuration 100 along the shared plane 112 is shown in FIG. IB. As shown, the TLA 108 is composed of, or includes, multiple individual LEDs 114 (or other light-emitting devices) arranged one-dimensionally around the outer circumference 116 of the rotary device 102, collectively forming a ring structure as shown in FIG. 1 A. The LEDs 114 emit light in a radially outward direction, as indicated by the arrows. The LEDs 114 may be individually mounted on the rotary device 102, or, alternatively, be disposed on a common ring-shaped substrate attached to the rotary device 102. While the LEDs 114 are depicted with gaps in between to illustrate that their light-emitting surfaces need not form a contiguous surface, the LEDs 114 with their associated packaging may form a mechanically contiguous structure. To provide a concrete example, LED packages may be 5 mm in length , with light-emitting surfaces each 2 mm in length. To cover the circumference of a rotating barrow having a circumference of, for example, 1000 mm, 200 such LED packages may be used. Light emitted by the LEDs 114 will generally diverge such that, beyond a certain distance from the light-emitting surfaces, the beams from adjacent, simultaneously emitting LEDs 114 overlap, thereby irradiating the entire 360° angle around the axis 104. [0017] The RPA 110 is mounted on a surface 118 facing the rotatory device 102, such that the one or more photodiodes 120 of the RPA 110 face radially inward. In an extreme case, the RPA 110 includes only a single photodiode 120 (or other light-sensing device). In other, alternative implementations, the RPA 110 includes a one-dimensional arrangement of multiple photodiodes 120 (shown in dashed outlines) along the intersection of the plane 112 perpendicular to the rotational axis 104 with the surface 118 of the stationary device 102. Using multiple photodiodes 120 in the RPA increases the angular overlap between the TLA 108 and RPA 110, and may serve signal optimization based on a larger fraction of the emitted light being captured, or allow for increased distances between the LEDs 114 of the TLA 108.

[0018] In various embodiments, the TLA 108 and RPA 110 are configured to be continuously in optical contact with each other as the rotary device 102 rotates about its axis 104; that is, as soon as or before an LED 114 loses a line of sight with the RPA 110, a new line of sight between the next LED 114 and the photodiode(s) 120 of the RPA 110 is established. Configuring the TLA 108 and RPA 110 may involve, e.g., choosing the numbers of LEDs 114 and spacings between them based on the distance between the TLA 108 and the RPA 110 and the beam divergence of the LEDs 114. The distance between the TLA 108 and the RPA 110 may depend on the transmission power of the LEDs 114 and the sensitivity of the photodiode(s) 120. In some embodiments, the TLA 108 and RPA 110 are spaced between 1 mm and 50 mm apart.

[0019] FIGS. 2A and 2B show an example system configuration 200 for optically transferring signals from a stationary device 202 to a rotary device 204 in perspective and cross-sectional views, respectively. In this configuration 200, an RPA 206 is mounted on the rotary device 204 (again depicted as a tubular structure) and rotates along with the rotary device 204 around a rotational axis 208. The TLA 210 is, in this case, stationary, and forms a ring that surrounds the rotary device 204 and is co-planar with the RPA 206, with spacing between the TLA 210 and the rotary device 204. The TLA 210 may, for instance, be mounted on the interior surface 212 of a stationary device 202 that coaxially surrounds the rotary device 204. The rotary device 204 can rotate inside the ring-shaped TLA 210. [0020] As illustrated in FIG. 2B, the TLA 210 is composed of or includes a one-dimensional array of LEDs 214 arranged along a circle centered at the rotational axis 206. The LEDs 214 emit light in the radially inward direction, as indicated by the arrows. The RPA 202 on the rotary device 204 m ay contain only a single photodi ode 216, or an array of photodiodes 216 (indicated in dashed outlines) along a circle concentric with the TLA 210. An array of photodiodes 216 can, as in configuration 100, serve signal optimization or relaxation of the spacing requirements on the LEDs 214 within the TLA 210. [0021] Various modifications to the configurations 100, 200 described with respect to FIGS. 1 A-2B are contemplated. For example, while, in both of the above configurations 100, 200, light is emitted by a circular array of LEDs and detected by an individual or, as depicted, a few photodiodes, the reverse — a circular array of photodiodes detecting light emitted by one or a few LEDs — is also possible. In yet another configuration, both TLA and RPA may extend around the entire circumference of respective concentric circles (e.g., for redundancy or improved signal quality). Conversely, it is possible that both TLA and RPA extend only partially around the circumference. Partial arrays may be configured to still achieve angular overlap for any rotational position (e.g., using a TLA that extend around half of a circle, along with a TDA that extends in two portion along two non-conti guous quadrants of a circle). Alternatively, in some embodiments, the TLA and RPA may be configured such that angular overlap between them, and therefore signal transfer, is limited to only a portion of a full rotation. As another variation, a rotary communication system may include two pairs of a TLA and an RPA, e.g., in two different planes perpendicular to the rotational axis, one pair for signal transfer from the rotary to the stationary device, and the other pair for signal transfer from the stationary device to the rotary device.

[0022] FIGS. 3 and 4 show schematic circuit diagrams illustrating example electronic transmission and receiver modules for converting between electrical and optical signals, in accordance with various embodiments. In the depicted example, input and output electrical signals are both digital. It is noted, however, that the TLA/RPA configurations described above are equally applicable to embodiments for analog electrical signals. [0023] FIG. 3 depicts a transmission module 300 including a TLA 302 and associated electronic transmission circuitry for driving the TLA 302 in accordance with an input electrical signal 304. The circuitry includes a signal buffer 306 that buffers the input electrical signal 304, a signal conditioner 308, and an LED driver 310 that generates the drive current applied to an array of LEDs, connected in series, that form the TLA 302. As shown, the LED driver 310 may be implemented with a transistor (e.g., a bipolar transistor) that, based on the conditioned input electrical signal applied to its base, switches the power to the TLA 302, which is connected to the transistor’s collector, on and off. A digital input electrical signal 304 is thus converted to a binary optical signal, i.e., to control blinking of the LED array (as a whole, that is, with all LEDs blinking synchronously).

[0024] FIG. 4 depicts a receiver module 400 including a RPA 402 and associated electronic receiver circuitry for converting photocurrents generated in the photodiodes back into an electrical signal. The photodiodes are connected in parallel, and their sum is fed into an amplifier 404 (e.g., an operational amplifier) of the receiver circuitry. The amplified signal is then further processed in a filter circuit 406 and a signal conditioner 408 before a digital output signal 410 is generated in an output driver circuit 412.

[0025] In accordance with various embodiments, transmission and receiver modules 300, 400 can accommodate signals with data rates of in excess of 100 megabits (e.g., hundreds of megabits). Such high data rates are important, e.g., to enable applications otherwise difficult to implement due to the high data rate request, such as Phased Array Steel Pipe Inspection Units.

[0026] Although embodiments have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader scope of the disclosure. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.