WO2021210003A1

WO2021210003A1 - Optical communication link for moving elements

Info

Publication number: WO2021210003A1
Application number: PCT/IL2021/050433
Authority: WO
Inventors: Yves Villaret
Original assignee: Motx Ltd.
Priority date: 2020-04-16
Filing date: 2021-04-16
Publication date: 2021-10-21

Abstract

Optical communication link with elements mobile along a defined path, the link comprising an optical guide extending along the defined path, the optical guide allowing light to enter or leave the guide along its length and having at least one of a static optical sensor and a static optical transmitter at a first end to inject or detect signals, the elements respectively having at least one of a mobile optical sensor and a mobile optical transmitter configured to slide along the guide as each respective element moves along the defined path, also to inject or detect signals from the guide.

Description

OPTICAL COMMUNICATION LINK FOR MOVING ELEMENTS

RELATED APPLICATION

This application claims the benefit of priority under 35 USC § 119(e) of US Provisional Application No. 63/010,729 filed 16 April 2020, the contents of which are incorporated herein by reference in their entirety.

FIELD AND BACKGROUND OF THE INVENTION

Optical guides are widely used, in many forms. Optical fibers are a type of optical guide which is widely used in communications. Other optical guides are used for sensors and short-range networking, as shown for example in patent US 5,195,162 by Sultan et al.

Characteristic of all these known applications is that the light sources are placed at fixed positions relative to the optical guide.

Optical fibers are commonly used for communication between computers and communication servers. They can be implemented in one to one or one to many configurations. When a “one to many” configuration is used, i.e. from a central computer or server A (node A) to many computers or servers Bn (node Bn), a main optical fiber having an end at node A is split into many secondary fibers that end at nodes Bn. Optical signals are injected into the fiber at one end and subsequently sensed at the far ends of the fibers. The fiber ends may then be fixed in proximity with optical sensors or emitters of the nodes. This type of communication between nodes are often referred as a “Passive Optical Network”, or PON.

A limitation of this type of communication is that the node emitter/receiver is placed at a precisely fixed position in proximity to the fiber ends and thus optical communications are not suitable for moving elements.

Nevertheless, in the automation industry, there is a need to provide communication between moving elements, whether they be parts of machines, pallets carrying parts for machining or other operations, or anything else, and a central controller. This is commonly done using electrical cables and cable chains. Automatic machines operate at high speed and short cycles; consequently, electrical cables are cyclically subject to bending and friction, and thus have a limited life time. It would thus be desirable to provide communication means that do not require moving cables.

An example of such a system is a linear motion system implemented with a ball screw and a linear encoder. In such a system, an electrical rotary motor, equipped with a rotary encoder, is used to rotate a screw; the screw traverses a nut fixed to a carriage sliding over linear bearing. The rotation of the screw generates a linear movement of the carriage. Commonly, the motor rotation angle is precisely controlled by a servo drive, so that the movement of the carriage is precisely controlled. Whenever a high precision is required, the mechanical backlash of the nut and the torsional flexibility of the screw induce deviation of the carriage position beyond the required accuracy. A common solution for this is to use a high precision linear encoder attached to the carriage. The servo drive controller executes a control algorithm that combines both rotary encoder and linear encoder to precisely control the position of the carriage.

Linear encoders commercially available include an encoder head to be fixed to the moving part (carriage). The linear encoder head includes magnetic or optical sensors and interface electronic outputting a digital signal data. Linear encoders are then connected to the central controller by means of an electrical cable and cable chain. These cables are subject to bending and friction, and thus have a limited life time. If the cable were replaced by an optical fiber, the lifetime would be even worse.

It is thus desirable to provide communication means to transmit data between moving elements and static controller(s). Generally, the distance between moving elements and the static controller is relatively short, within the range of the machine size and a few meters.

Wireless solutions have been proposed, as for example in patent US 5,965,963 by Chitayat. However wireless solutions are very seldom accepted in industrial application, due to possible interference and lack of reliability.

SUMMARY OF THE INVENTION

An object of the present embodiments is to provide an optical communication system between a numbers of units that are moving along a defined path. The path may be of any shape, and with or without bifurcations.

An optical communication system according to the present invention, further referred here as OCS, may be advantageously used to capture optical signals from a number of sources, mix the sources as necessary and propagate them to at least one guide extremity, wherein the sources may be elements that move along a path in proximity to the optical guide. Alternatively, the OCS may be used to propagate signals from a single stationary source to one or more moving elements. A third alternative is a bidirectional communication in which signals may come from a single stationary source and propagate to the one or more moving elements. A fourth alternative involves the signal propagating from one moving element to another moving element. Many useful applications of an OCS according to the present embodiments may be considered. Certain implementations are described below as examples. It must be understood that many other usages may be considered.

In one example, in manufacturing industry, Conveyors and transportation systems convey various components of the manufactured products on separate pallets. Pallets move along a path, which can be of any shape and with bifurcations. Herein, we refer to these types of transportation system as Multi-carriage Systems, or MCS.

In such MCS, the OCS of the present embodiments provides communication means between each pallet and a central controller unit so that various sensors can be installed on each pallet that report the state of the component on the pallet to the central controller.

In an example of use in a MCS, a sensor measures the weight of the component on the pallet, and according to the measured weight the pallet is routed by the central controller to a specific location.

In another example of use in a MCS, the sensor measures the precise position of the pallet, and the central controller precisely controls the movement of the pallet.

In yet another example of use in a MCS, the sensor detects the proximity to other pallets and the distance between pallets is controlled by the central controller.

The OCS of the present embodiments may also be used with linear motion systems, widely used in automatic machinery. They include linear stages using ball screws, linear motors or belts. The OCS of the present embodiments may enable the use of sensors on the moving element. Sensors such as limit switches, linear encoders and sensors of any type required for the specific application may be used. The sensor output is propagated and sent to a central controller by means of the optical guide.

There are specific linear motion systems that use ball screws and require high accuracy. A common practice is to use a motor with an encoder to drive the ball screw, and use a second-high precision linear encoder fixed to the moving element. This second-high precision encoder requires moving cables fixed to the moving element. These moving cables induce vibrations and have a negative impact on the reliability of the motion system. To address these drawbacks, a power supply on the moving element can be used to power the encoder, for example a battery or a contactless power transfer system, and the OCS of the present embodiments may provide the communication means to send the encoder data to the motion controller. Many other useful applications where a pallet communicates with a central controller or to other pallets may do so using the present embodiments in order to advantageously enhance the functionality of multi-carriage systems.

The present embodiments may provide means to establish an optical communication link between elements moving along a linear path and at least one static unit. An optical guide which allows diffusion of light out of its sides along its length, and/or captures light from along its length is disposed along the path of the moving elements which include optical elements that slide along the length of the optical guide. The light diffused or captured along the length of an optical guide may be used to establish a communication link between moving elements sliding along the optical guide and at least one static element optically connected to the optical guide at one of its extremities.

In general, the optical guide is selected to have at least one of the two following properties:

1) an optical signal injected at one of its extremities is partially diffused along the path and

2) optical power emitted in proximity alongside the optical guide is partially propagated to at least one of its extremities.

Each static unit (SU) is placed in proximity to one of the optical guide extremities. A static unit (SU) implements at least one of the following two functions: a) it converts an optical signal sensed at the optical guide extremity into an electrical signal, b) it converts an electrical signal into an optical signal and injects the optical signal into the optical guide.

An optical head (OH) is fixed to each moving element, sliding in proximity alongside the optical guide and implements at least one of the two functions: a) it converts part of the optical signal diffused by the optical guide into an electrical signal b) it converts an electrical signal into an optical signal which is emitted in proximity alongside the optical guide. Digital data is coded into an electrical signal and is transmitted from the SU (SU function b) to the moving element (OH function a) and/or from the moving element (OH function b) to the SU (SU function a).

According to one aspect of the present invention there is provided an optical communication link with elements mobile along a defined path, the link comprising a first optical fiber extending along at least part of the defined path, the optical fiber having a length and being configured to allow light to enter or leave the fiber along the length and having at least one of a static optical sensor and a static optical transmitter at a first end of the optical fiber, the elements respectively having at least one of a mobile optical sensor and a mobile optical transmitter configured to slide along the length as the respective element moves along the defined path.

In an embodiment, light diffusing outwardly or captured along the length of the first optical fiber establishes communication between the elements and the static optical sensor and the static optical transmitter, as respective at least ones of the mobile optical sensor and the mobile optical transmitters slide along the first optical fiber.

In an embodiment, the first optical fiber comprises a core and cladding, and a discontinuity is applied to the cladding in a strip along the length, thereby to provide the light diffusing outwardly or being captured.

In an embodiment, the first optical fiber comprises a transparent tube coated with a reflective material and the reflective material is removed in a strip along the length.

In an embodiment, the discontinuity comprises addition of a diffusive substance to the cladding to form the strip.

In an embodiment, the discontinuity comprises a step change in an outer radius of the first optical fiber, the step change baring a planar face in the cladding along the length.

In an embodiment, the first optical fiber comprises a core without cladding.

In an embodiment, the first optical fiber has a first side along the length towards the at least one of the mobile optical sensor and the mobile optical detector, and wherein a reflective coating is provided along a second side along the length opposite the first side.

In an embodiment, the first optical fiber has a first side along the length towards the at least one of the mobile optical sensor and the mobile optical detector, and wherein a diffusive surface is provided along a second side along the length opposite the first side.

In an embodiment, the mobile optical sensor or the mobile optical detector is configured to inject or detect light at an acute angle from the length. In an embodiment, the mobile optical sensor or the mobile optical detector is placed across a predetermined gap from the first optical fiber.

In an embodiment, the elements mobile along a path are pallets moving along a track.

The first optical guide may comprise two or more guide sections, each guide section having the static optical transmitter and/or the static optical sensor at one end.

In an embodiment, the communication is bidirectional.

An embodiment may be used to connect a central controller to the elements. According to a second aspect of the present invention there is provided an optical communication method for communication with elements mobile along a defined path, the method comprising: laying a first optical fiber to extend along at least part of the defined path, the optical fiber having a length and allowing light to enter or leave the fiber along the length; sliding the at least one of a mobile optical sensor and a mobile optical transmitter, along the length, the at least one of a mobile optical sensor and the mobile optical transmitter being attached to and moving with a respective element moving along the defined path, thereby to inject light into the first optical fiber or to detect light from the first optical fiber to establish communication with the elements.

In the method, light diffusing outwardly or captured along the length of the first optical fiber establishes communication between the elements and the at least one of a static optical sensor and a static optical transmitter, as respective at least ones of the mobile optical sensor and the mobile optical transmitters slide along the first optical fiber.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS:

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

In the drawings:

Fig. 1 is a simplified schematic diagram which shows an optical guide implementing a communication link between one static unit at one extremity and several optical heads alongside the optical guide according to an embodiment of the present invention; Fig. 2 is a simplified schematic diagram which shows an optical communication link between 3 movers on a linear path and a static unit according to an embodiment of the present invention;

Fig. 3 is a simplified schematic diagram which shows a multi-carriage system wherein a communication link is implemented using several optical guides and static units;

Fig. 4 is a simplified schematic diagram which shows an implementation of an optical head sliding along an optical guide according to an embodiment of the present invention;

Fig. 5a is a simplified schematic diagram which shows an implementation wherein the optical guide is an optical fiber, and wherein the outer surface of the fiber has been modified on a strip along the fiber to allow side entrance and exit of light according to an embodiment of the present invention;

Fig. 5b is a simplified schematic diagram which shows a small portion of the optical guide of Fig 5a showing details of the modification and the light dispersing of a side entering light ray according to an embodiment of the present invention;

Fig. 6 is a simplified schematic diagram which shows an optical fiber with a spiral cross section to provide a thin planar entrance section according to an embodiment of the present invention;

Fig. 7 is a simplified schematic diagram which shows an implementation wherein the optical guide is an optical fiber, and wherein the outer surface of the fiber has been modified to be dispersive on a strip along the fiber, and light is injected on the diametrically opposite side of the fiber, according to an embodiment of the present invention; and

Fig. 8 is a simplified flow chart illustrating operation of an embodiment of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

Optical guides are widely used in lighting and fiber optic communication. In fiber optic communication system, it is desired to allow a propagation of light signals over long distance, and for this purpose optical fibers have been designed with a very low attenuation factors of a few decibel per kilometer. Fiber optic communication system are designed to provide a communication link between distant and fixed stations.

In lighting applications, optical guides and fibers are often designed to diffuse light over their length. This is for example described in patent US 8,591,087 B2 by Bickham et al. Consequently, optical guides for lighting applications are conceived for relatively short distances. Optical guides that diffuse light may also have the property of capturing some light along their length and propagating this light to one of their extremities.

The present embodiments may provide an optical communication link with elements mobile along a defined path, the link comprising an optical fiber extending along the defined path, the optical fiber allowing light to enter or leave the fiber along its length and having at least one of a static optical sensor and a static optical transmitter at a first end to inject or detect signals, the elements respectively having at least one of a mobile optical sensor and a mobile optical transmitter configured to slide along fiber as each respective element moves along the defined path, also to inject or detect signals from the fiber.

It is noted that all optical fibers have some level of attenuation. The fibers of the present embodiments however allow light to enter or leave along the length to an extent that allows signaling to be detected by standard light detectors.

In the present disclosure, the light diffused or captured along the length of an optical guide may be used to establish a communication link between moving elements sliding along the optical guide and at least one static element optically connected to the optical guide at one of its extremities.

The present embodiments may provide optical wireless communication between moving elements and static stations. Optical guides that allow for outward diffusion of light along their lengths are used. These optical guides are also able to capture a small portion of light that is emitted along their lengths and in proximity thereto, and propagate this light power to one of their extremities. Such optical guides are disposed along the movement path of the moving element. The amplitude of the optical signal transmitted is rapidly decreasing with the length of the optical guide, limiting the applicable length of the optical guide. Whenever a longer path is desired, several optical guides are used, each one covering a portion of the desired path.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

Referring to Fig 1, optical guide 101 is used to provide an optical communication link between a static unit 102 and three optical heads 104a-104c. The optical guide 101 defines a path, and optical heads 104a-104c are able to move along and in proximity to that path. Static unit 102 has an optical connection 103 to the optical guide and includes a light emitter to convert electrical signal 105 into an optical signal and inject it into the optical guide 101. Static unit 102 also includes a receiver to convert an optical signal received at the optical connection 103 into electrical signal 105. Optical heads 104a- 104c also include a receiver to convert light into an electrical signal and a light emitter to convert electrical signal 106a- 106c into light. Optical heads including light emitters are able to slide along and in proximity to the path defined by the optical guide, without contact and with a small air gap. Data encoded into an electrical signal can thus be transmitted from the static unit to the optical heads using a light emitter from the static unit and light receivers at the optical heads. The light emitter of the static unit 102 injects a high intensity light signal. Part of the signal is diffused along the light guide and is sensed by the optical head receivers. Symmetrically, data encoded into an electrical signal may be transmitted from an optical head to the static unit using the optical head light emitter and the static unit light receiver.

The communication link described above is bidirectional, however it must be understood that a unidirectional link may be used, either from static unit to several optical heads, or from several optical heads to a static unit. In particular, in order to implement a bidirectional communication link, it may be advantageous to use two optical guides, wherein one optical guide is used for communication from a static unit to optical heads, and the second optical guide is used for communication from optical heads to a static unit. The two optical guides may be disposed in parallel along the path of the optical heads.

The optical guide according to the present embodiments may diffuse and capture a sufficient amount of light so that standard light sensors may be used in the receiver and will be sensitive enough to detect the diffused or captured light. In a first example, the electrical signal used to encode the data to be transmitted is a digital signal and presence or absence of light may encode the Boolean values 0 and 1. In that case a threshold of light intensity is defined to differentiate the 0 and 1 states. It is then required that the amount of diffused or captured light may be higher than the threshold.

In a second example a signal is encoded in a frequency modulated carrier. In that case, narrow bandwidth, high gain amplifiers may be used, and the minimum required amount of diffused or captured light is lower.

In all cases, the optical guide may be designed to provide a sufficient amount of diffused or captured light along the path length. The optical guide to be used may be of many kinds. Several examples are shown hereinbelow in respect of Figs. 5a-7.

Reference is now made to Fig 2 which is a simplified diagram showing an optical link between one static unit 209 and three moving elements 201a-201c. The moving elements 201a- 201c are schematically shown here as moving pallets sliding over a linear track 203. To each pallet 201a-201c is attached an optical head 202a-202c. The optical heads 202a-202c slide over, contactlessly but in proximity to, an optical guide 204. A power supply is attached to each pallet (205a-205c) to provide power to the optical heads. The power supply is preferably a contactless power supply, for example inductive, or a battery, so that a moving cable is not required. Each pallet is designed to transport a load and includes specific sensors for the specific function of the system. The data output of the sensors is converted in optical signals by the optical heads; a portion of this optical signal is captured and propagated by the optical guide 204 to the static unit 209 and converted to an electrical signal by the static unit 209. Conversely, the static unit 209 may convert an electrical signal into an optical signal and inject the optical signal into the optical guide 204; optical heads 202a-202c may capture a portion of the injected optical signal and convert it into an electrical signal which becomes available on pallets 201a-201c.

As an example, the signal sent by the static unit 209 may be a request signal, requesting a pallet sensor to send back sensor data.

The system described above may establish a multi-carriage system with one static unit and several optical heads. Whenever a greater number of carriages is required, and the path length is increased, the number of optical heads that may be optically connected is limited by the bandwidth of the optical link and the attenuation of the optical signal along the optical guide. Several optical links may be used, each one covering a portion of the total track length.

Reference is now made to Fig 3, in which a multi-carriage system is schematically shown. Five pallets 302a-302e slide on a closed loop track 301. To each pallet an optical head is fixed 306a-306e. Along the path, six optical guides 307a-307f are disposed, each one extending over a different portion of the path and altogether extending over the entire path length. When the pallets 302a-302e slide on the track the corresponding optical heads 306a-306e travel in proximity to the optical guides 307a-307f. Each optical guide extremity is optically connected to an interface unit 305a-305f. Each interface unit is thus optically connected to two optical guides. Considering for example interface unit 305b, it is optically connected to optical guides 307a and 307b, interface unit 305c is optically connected to optical guide 307b and 307c and so on for all interface units. Each interface unit 305a-305f may include two static units as described above in respect of Fig 1, and electronics may connect the electric signal to a field bus node. Field buses used in the present embodiments may be of any industrial type selected for the MCS. Examples of fieldbuses include Ethercat, Can bus, and Modbus. All interface units 305a-305f are connected in a loop to a central controller 304. Finally, a communication link is established by means of the optical guide, the interface units and the field bus between pallets and the central controller. Such a communication link is wireless and contactless, and thus not subject to wear and failure. High communication speeds may be used since optical transmission is intrinsically very fast. In particular, the communication link may be used to read a high precision position sensing device to control the position of the pallet at high speed and with precision.

In commercially available multi-carriage systems, the movement of the pallets is generated by the electromagnetic force of a great number of coils disposed all along the track. In order to control the position of a number of pallets, software is needed to activate the coils in proximity to the pallets, in coordination with the position information from each. This requires a high speed communication between pallets position measurement devices and coil drive controllers.

In the case where each pallet has its own power, its own position measurement and its own controller, a particular advantage of such an MCS using the OCS of the present embodiments is that only one drive is needed per pallet to control its speed and position. The central controller then has the relatively simple task of communicating position commands to each pallet. The communication speed required is relatively low and the control software is greatly simplified.

Reference is now made to Fig 4, which shows the principle of an implementation of an optical head 405 sliding in proximity with an optical guide 403. A long static support 401 has a one turn square spiral section shape and may extend over the whole length of the path. At internal wall 407 a slot is provided to receive the optical guide 403. A moving support 402 is shaped to be inserted in the static support and may slide along the optical guide without making contact. An optical head 405 is attached to the moving support at its internal part 406. A light emitter 404 is shown in Fig 4 in proximity to the optical guide 403 without contact. When the moving support 402 slides contactlessly inside the static support 401, the light emitter 404 slides along the optical guide 403, contactlessly and in proximity. The static and moving supports (401, 402) are coated with optical black material, so that no parasitic light may reach the optical guide. In Fig 4, a light emitter only is visible, but a light receiver may also be installed on the optical head. The air gap between the static and moving supports may be sized to allow the optical guide to assume a curved path.

Having shown how an optical communication link may work, we now consider various optical guides that may be used.

Figs. 5a and 5b show an optical guide designed to diffuse or capture a sufficient amount of light along a few meters length. Along the length of the optical guide 500 an entry strip 501 is formed. This entry strip 501 is of small width 505 in order to allow entrance of light without overly degrading the attenuation factor of the guide. The entry strip 501 has a surface which is made of diffusive material for example, so that part of the light emitted in proximity to the strip may diffuse into the optical guide and subsequently propagate along the guide.

One kind of optical guide that may be used is an optical fiber on which the property of a thin strip along its outer wall is modified. A small section of such an optical fiber is shown in Fig 5b. On the optical fiber 500, the property of the fiber surface has been modified and made dispersive on a thin strip 501 extending all along the optical fiber, and shown as a double dashed line 501. The optical fiber 500 has a round cross-section and at its outer circumference, cladding 502, is made of a material of lower refraction index, as is typical in optical fiber manufacture. The thin entry strip 501 introduces a discontinuity in the cladding on the width of the entry strip. The surface of the entry strip 501 is treated to be diffusive. Thus for example the strip may be coated with a diffusive material. Light emitted in proximity to the entry strip may diffuse into the interior of the fiber in all directions, as shown for the light ray 506 which is dispersed in many directions as shown at 507. Part of the dispersed light may be captured by the fiber and propagate to one of its extremities. Inversely, part of the multimode light injected in the fiber may diffuse all over the length of the entry strip and may be sensed by an optical head in proximity to the guide.

Another kind of optical guide that may be used is a light pipe. The light pipe is a transparent tube or bar coated with a reflective material and the reflective material is removed along the length of entry strip 501. Light may be injected or sensed in proximity to the entry line.

Another kind of optical guide that can be used is a fiber optic designed to diffuse light along its path, such as the kind of optical fiber used for light effects and decoration purposes. An example is described in patent US 8,591,087 B2 by Bickham et al. As described in this patent, small particles are inserted in the fiber to diffuse light. The same particles will also diffuse light if a transversal light beam is projected on the fiber side.

Another kind of optical guide that may be used is shown in Fig 6. Optical fiber 600 has been extruded to have a spiral section contour and planar entrance strip 603, where the cladding has a step change in the radius to form the planar entrance strip. The fiber has a typical fiber structure with a round interior 607 and surrounding cladding 606, the surrounding cladding material 606 having a lower refraction index than the internal part 607. A light emitter 602 is shown issuing a light beam; a light ray 604 is shown entering the optical fiber through the entrance strip 603 and propagates in a helicoidal trajectory 605 along the fiber. In order for light ray 604 to penetrate the fiber, the planar entrance strip 603 is made diffusive or dispersive so that some rays at least may be dispersed in a direction that can be propagated by the fiber. The width of the entrance strip 603 may be made as small as possible to minimize the attenuation factor of the fiber.

Reference is now made to Fig 7, which shows an implementation wherein the optical guide is an optical fiber, and wherein the outer surface of the fiber has been modified on a strip along the fiber, and light is injected on the diametrically opposite side. On the optical fiber 700, the property of the fiber surface has been modified and made dispersive on a thin strip 702 extending all along the optical fiber. A light emitter 701 emits light ray 703, which strikes the outer surface of the fiber at point 704. By the law of refraction, the light ray is refracted to form ray 705 and hits the interior of the thick strip 702 at point 706. Due to the dispersive property of the thick strip 702, the ray is dispersed in many directions, and some of these dispersion rays are in a direction that can be propagated by the fiber. The embodiment of Fig. 7 may thus provide a way of achieving side injection of light into the fiber 700.

Referring now to Fig. 8, optical guides and the methods described hereinabove may thus provide means to establish communication between a number of units alongside the path of an optical guide and at least one static unit in proximity of an end of the optical guide. A track along which mobile elements move 800 is provided and optical fiber is laid out along the track 802. The fiber allows for diffusion out or injection in of light along its length, and sensors or transmitters on the mobile element slide along the optical fiber as the element moves along the track - 804. Signals are injected into the optical fiber and detected and thus communication is established over the optical fiber with the mobile units. The communication may be bidirectional as discussed.

Thus, communication means between a static unit and several mobile units disposed alongside the path is conceived and described, without any need for cable leads. According to the present embodiments, communication may be established between a large number of units moving along a path and at least one static unit, and the embodiments may be applicable in multi-carriage system, linear motors, cranes and many others.

The terms "comprises", "comprising", "includes", "including", “having” and their conjugates mean "including but not limited to".

The term “consisting of’ means “including and limited to”.

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment and the present description is to be construed as if such embodiments are explicitly set forth herein. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or may be suitable as a modification for any other described embodiment of the invention and the present description is to be construed as if such separate embodiments, subcombinations and modified embodiments are explicitly set forth herein. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting. In addition, any priority document(s) of this application is/are hereby incorporated herein by reference in its/their entirety.

Claims

WHAT IS CLAIMED IS:

1. Optical communication link with elements mobile along a defined path, the link comprising a first optical guide extending along at least part of said defined path, the optical guide having a length and being configured to allow light to enter or leave the guide along said length and having at least one of a static optical sensor and a static optical transmitter at a first end of said optical guide, the elements respectively having at least one of a mobile optical sensor and a mobile optical transmitter configured to slide along said length as said respective element moves along said defined path.

2. The optical communication link of claim 1, wherein light diffusing outwardly or captured along the length of said first optical guide establishes communication between said elements and said at least one of said static optical sensor and said static optical transmitter, as respective at least ones of said mobile optical sensor and said mobile optical transmitters slide along said first optical guide.

3. The optical communication link of claim 1 or claim 2, wherein said first optical guide comprises a core and cladding, and wherein a discontinuity is applied to said cladding in a strip along said length, thereby to provide said light diffusing outwardly or being captured.

4. The optical communication link of claim 1 or claim 2, wherein said first optical guide comprises a transparent tube coated with a reflective material and wherein the reflective material is removed in a strip along said length.

5. The optical communication link of claim 3, wherein said discontinuity comprises addition of a diffusive substance to said cladding to form said strip.

6. The optical communication link of claim 3, wherein said discontinuity comprises a step change in an outer radius of said first optical guide, said step change baring a planar face in said cladding along said length.

7. The optical communication link of claim 1 or claim 2, wherein said first optical guide comprises a core without cladding.

8. The optical communication link of claim 7, wherein said first optical guide has a first side along said length towards said at least one of said mobile optical sensor and said mobile optical detector, and wherein a reflective coating is provided along a second side along said length opposite said first side.

9. The optical communication link of claim 7, wherein said first optical guide has a first side along said length towards said at least one of said mobile optical sensor and said mobile optical detector, and wherein a diffusive surface is provided along a second side along said length opposite said first side.

10. The optical communication link of claim 7, wherein said at least one of said mobile optical sensor and said mobile optical detector is configured to inject or detect light at an acute angle from said length.

11. The optical communication link of any one of the preceding claims, wherein said at least one of said mobile optical sensor and said mobile optical detector is placed across a predetermined gap from said first optical guide.

12. The optical communication link of any one of the preceding claims, wherein said elements mobile along a path are pallets moving along a track.

13. The optical communication link of any one of the preceding claims, wherein said first optical guide comprises a plurality of guide sections, each guide section having at least one of said static optical transmitter and said static optical sensor at a respective first end.

14. The optical communication link of any one of the preceding claims, wherein said communication is bidirectional.

15. The optical communication link of any one of the preceding claims, connecting a central controller to said elements.

16. Optical communication method for communication with elements mobile along a defined path, the method comprising laying a first optical guide to extend along at least part of said defined path, the optical guide having a length and allowing light to enter or leave the guide along said length; sliding said at least one of a mobile optical sensor and a mobile optical transmitter, along said length, said at least one of a mobile optical sensor and said mobile optical transmitter being attached to and moving with a respective element moving along said defined path, thereby to inject light into said first optical guide or to detect light from said first optical guide to establish communication with said elements.

17. The optical communication method of claim 16, wherein light diffusing outwardly or captured along the length of said first optical guide establishes communication between said elements and said at least one of a static optical sensor and a static optical transmitter, as respective at least ones of said mobile optical sensor and said mobile optical transmitters slide along said first optical guide.