Systems and methods for operating lighting assemblies in a multi-imager environment

Abstract

At least some embodiments of the present invention are directed to means for operating an illumination assembly associated with a group of imaging devices. An example method includes causing each of a plurality of imaging devices to acquire image data during a group acquisition operation, wherein each of the plurality of imaging devices has (i) a respective delay until a start of an exposure duration, (ii) the respective exposure duration, and (iii) a total operating duration. The method also includes causing an illumination assembly to transition from a first state to a second state based on a shortest delay of the imaging devices, and further causing the illumination assembly to transition from the second state to a third state based on a longest total operating duration of the imaging devices.

Description

BACKGROUNDIn applications such as fixed industrial scanning, multiple cameras may be configured to share a single lighting assembly that is controlled, e.g., via a single communication / signal bus. If a visual inspection needs to be performed simultaneously, such a configuration may not be a problem because the illumination may be controlled to be activated along with the simultaneous activation of the imaging devices. However, in cases where the cameras are programmed to be activated at different times (e.g., when a product moves from location A on a conveyor at time t to location B at time t+n), when they are activated at different exposure times, when there is an uneven delay in activation due to infrastructure, or in other cases of non-synchronous operation, issues may arise with the proper timing for activation of the lighting assembly to ensure sufficient illumination during operation of all cameras.Although one remedy to this problem is to operate the lighting assembly in the "flashlight" mode, where it remains on indefinitely, such an approach results in a waste of energy.Therefore, there is a need for systems and methods for coordinating activation of an illumination assembly associated with multiple, non-synchronously activated imaging assemblies.DESCRIPTIONIn one embodiment, the present invention is an imaging system comprising: a host device having a processor; a plurality of imaging devices, each of the plurality of imaging devices communicatively coupled to the host device; and an illumination assembly for illuminating at least one target imaged by each of the plurality of imaging devices, the illumination assembly communicatively coupled to the host device, each of the plurality of imaging devices being caused by the host to acquire image data during a group acquisition operation, wherein each of the plurality of imaging devices is associated with (i) a respective delay until a respective beginning of an exposure duration, (ii) the respective exposure duration over which image data is acquired, and (iii) a respective total operation duration comprising the respective delay and the respective exposure duration, wherein, during the group acquisition process, the lighting assembly is caused by the host device to transition from a first operating state to a second operating state based on a shortest delay selected from each of the respective delays of each of the plurality of imaging devices, and wherein, during the group acquisition process, the lighting assembly is caused to transition from the second operating state to a third operating state based on a longest total operating duration selected from each of the respective total operating durations of each of the plurality of imaging devices.In another embodiment, the present invention is a method of operating an imaging system comprising: (a) causing, by a host device having a processor, each of a plurality of imaging devices to acquire image data during a group acquisition operation, wherein each of the plurality of imaging devices is associated with (i) a respective delay until a respective beginning of an exposure time, (ii) the respective exposure time over which image data is acquired, and (iii) a respective total operation time comprising the respective delay and the respective exposure time; (b) causing, by the host device and during the group acquisition process, an illumination assembly to transition from a first operating state to a second operating state based on a shortest delay selected from each of the respective delays of each of the plurality of imaging devices, the illumination assembly operable to illuminate at least one target imaged by each of the plurality of imaging devices; and (c) causing, during the group acquisition process, the illumination assembly to transition from the second operating state to a third operating state based on a longest total operating duration selected from each of the respective total operating durations of each of the plurality of imaging devices.BRIEF DESCRIPTION OF THE DRAWINGSThe accompanying figures, wherein like reference numerals refer to identical or functionally similar elements throughout the several views, together with the detailed description below, form a part of the specification and serve to further illustrate embodiments of concepts that include the claimed invention, as well as explain various principles and advantages of these embodiments. FIG. 1 shows an example of an environment with an example imaging and illumination system used therein, in accordance with embodiments of the present disclosure. FIG. 2 is an example of a timing diagram of various signals transmitted from a host to imaging assemblies and lighting assemblies, in accordance with embodiments of the present disclosure. FIG. 3 is an example of a process flow corresponding to the timing diagram of FIG. 2, in accordance with embodiments of the present disclosure.Those skilled in the art will appreciate that elements in the figures are shown for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to improve understanding of embodiments of the present invention.The apparatus and method components have been represented, where appropriate, by conventional symbols in the drawings that show only those specific details relevant to understanding the embodiments of the present invention, so as not to obscure the disclosure with details readily apparent to those skilled in the art having recourse to the present description.DETAILED DESCRIPTIONTurning now to FIG. 1, an example environment 100 is shown in which systems and methods according to the present disclosure may be implemented and / or practiced. The environment 100 is illustrated with a conveyor 102 on which is placed one or more items 104 that are moved from left to right via the conveyor. As the object 104 moves through an imaging area 106, cameras (also referred to as imaging devices) 108, 110 capture one or more images of the object 104 for downstream processing. To ensure sufficient illumination of the object 104 during imaging operations, the environment 100 includes an illumination assembly 112 that emits light over at least a portion of the field of view (FOV) of each camera.The collection of the plurality of cameras and the lighting assembly may collectively be referred to as an imaging system 114, which also includes a host device communicatively coupled to each of the cameras 108, 110 and the lighting assembly 112. The host 116 could be in the form of a computer that can execute an application that can provide illumination / imaging trigger signals to the cameras 108, 110 and the lighting assembly 112 directly or indirectly (e.g., via a PLC 117) downstream. The application may be stored in a memory 116.1 of the host 116 and may be executed by a processor 116.2 of the host 116. It should be appreciated that certain aspects of the control of the various assemblies may also be adopted by the PLC 117. As such, the PLC 117 may also include suitable memory and processor elements to effectively perform downstream control operations. In other examples, the PLC 117 may be integrated with the host 116.The host is communicatively coupled to the lighting assembly 112 via communication means 118 and to the imaging assemblies 108, 110 via communication means 120. The communication means 118, 120 between the host 116 and the lighting assembly 112 and / or the imaging assemblies 108, 110 may take any form available to those of ordinary skill in the art. In preferred embodiments, the host 116 is directly or indirectly connected to (i) the lighting assembly 112 via a single communication bus and to (ii) the imaging assemblies 108, 110 via a wired connection, e.g., via Ethernet, USB, serial, CoaPress, FireWire, CameraLink, etc. In addition to a direct connection, the communication means 106, 108 may also include gateways, switches, routers, PLCs, etc.The lighting assembly 112 may be any assembly capable of emitting electromagnetic radiation in the portion of the electromagnetic spectrum perceived by the human eye or in the ultraviolet or infrared portion of the spectrum. The components responsible for this emission may include LEDs, lasers, halogen lamps, etc. Moreover, the lighting assembly may include a single light source (e.g., a single LED), multiple light sources (e.g., multiple LEDs), or multiple rows of light sources (e.g., multiple rows of LEDs or different colors). Depending on the application, the lighting assembly may include one or more filters, such as a polarization or color filter.To operate the lighting assembly 112, the host 116 transmits a lighting signal (also referred to as a lighting control signal) to the lighting assembly 112 via communication means 118 that, via internal wiring and / or processing, causes the lighting assembly 112 to activate its light source(s) and provide lighting via a FOV for a predetermined duration. The actual activation of the illumination source can be achieved in various ways. For example, an illumination signal in the form of a pulse having a duration of t milliseconds (ms) may be transmitted from the host directly to the lighting assembly 112 such that the current forming the pulse drives the illumination source for the duration of t milliseconds. In another example, the signal may be transmitted from the host with a duration of t milliseconds, which signal activates a physical or logic relay for t milliseconds such that a drive current for t milliseconds is directed through the relay to the lighting source. In another embodiment, the lighting assembly 112 may include an activation duration register that may be programmed with a value that defines the lighting duration (e.g., t milliseconds). In this case, the host 116 may send a trigger signal to the lighting assembly 112 to activate its lighting source for the duration specified by the value programmed in the activation duration register.With respect to the imaging assemblies 108, 110, in various embodiments, each assembly includes an image sensor (or images sensors) (also referred to as an imaging sensor or imager) that is a solid state device, e.g., a CCD or a CMOS imager, that has a one-dimensional array of addressable image sensors or pixels arranged in a single row, or a two-dimensional array of addressable image sensors or pixels arranged in mutually orthogonal rows and columns and that is for sensing return light captured from a lens group via an imaging FOV along an imaging axis that is perpendicular to the substantially flat image sensor. The lens group serves to focus the returning light onto the array of image sensors (also referred to as pixels) to enable the image sensor and thus the imaging assembly to generate a digital image. In particular, the light incident on the pixels is captured and the output of these pixels generates image data associated with the environment within the field of view (which may include the target 104). This image data may be processed by an internal controller / processor (e.g., by being sent to a decoder that identifies and decodes decodable characters detected in the image data) and / or may be sent upstream to the host 116 for processing there.The activation of the imaging sensor of the imaging assemblies 108, 110 may be at least partially controlled by the host 116 via the communication means 120. In some cases, a pulse of duration y milliseconds may be sent from the host directly to an imaging assembly 108 / 110, where the current forming the pulse drives the imaging sensor to capture image data over an image. In other cases, a y millisecond duration pulse transmitted from the host 116 may be passed to a logic and / or physical relay, which relay allows a drive current to be sent to the image sensor for a y millisecond duration. In another embodiment, an imaging assembly 108 / 110 and / or its corresponding image sensor may include a register, wherein the value written to the register is associated with the duration (e.g., a duration of y milliseconds) over which the sensor will capture image data for a frame of images in response to a trigger signal. In this case, the image sensor is activated in response to receipt of an exposure trigger signal (also referred to as an exposure signal or an exposure control signal) to capture image data for a duration of y milliseconds over one frame.As mentioned above, in some examples, the imaging assemblies 108 and 110 may have different activation times and / or exposure durations. FIGS. 2 and 3 show an example timing diagram 200 of various signals transmitted from the host 116 (and in this example, via a PLC 117) to the imaging assemblies 108, 110 and the lighting assembly 112, as well as a process flow 300 corresponding to the timing diagram in accordance with the present disclosure. More specifically, at time t 0, the host 116 sends a trigger signal 202 to the PLC 117. In this example, the PLC 117 is programmed with various delays when the individual imaging assemblies 108, 110 are to be activated and with what exposure time. For simplicity, it is assumed that both imaging assemblies 108 of FIG. 1 operate synchronously, and both imaging assemblies 110 of FIG. 1 are also considered to operate synchronously. However, it should be appreciated that control of individual cameras is also within the scope of the methods and approaches presented herein.Upon receipt of the trigger signal 202 by the PLC 117 (e.g., generated by the host 116 based on a machine application executing an image processing task), the PLC sends exposure control signals 208 and 210 to the imaging devices 108 and 110, respectively. As can be seen from the diagram 200, the exposure control signal 108 is transmitted to the imaging devices 108 with a time delay TD 1 at the time t 1. The exposure time over which image data is acquired by the imaging devices 108 takes t 3- t 1, such that the total operation time is TT 1, which corresponds to t 3- t 0. Similarly, the exposure control signal 110 is transmitted to the imaging devices 110 with a time delay TD 2 at time t 2. The exposure time during which the image data is acquired from the imaging devices 110 takes t 4- t 2 so that the total operation time is TT 2, which corresponds to t 4- t 0. Referring to FIG. 3, this collection of transmissions 302 causes imaging devices 108, 110 to capture image data during a group acquisition operation, each of the imaging devices 108, 110 being associated with (i) a respective delay until a respective beginning of an exposure duration, (ii) the respective exposure duration over which image data is captured, and (iii) a respective total operating duration including the respective delay and the respective exposure duration. In some embodiments, a group acquisition process is a collection of signals directed to a series of imaging devices grouped in any way (e.g., a group including a single lighting assembly coupled to a host via a single communication bus).To ensure proper illumination throughout the exposure period, the PLC 117 sends a common illumination control signal 212 to the lighting assembly 112. This signal is transmitted at time t1 and continues until time t4. Specifically, the beginning of the signal 212 corresponds to the shortest time delay selected from the time delays TD 1 and TD 2 of the imaging devices 108, 110. In this example, the shortest time delay is TD 1 corresponding to the exposure pulse 208 for the imaging device 108 triggered by the PLC at time t 1. The beginning of the signal 212 causes the PLC 304 to cause the lighting assembly 112 to transition from a first operating state to a second operating state, and this occurs based on the shortest delay selected from the respective delays of the imaging devices 108, 110.Signal 212 remains active until time t4. At this time, the PLC 306 causes the lighting assembly 112 to transition from the second operating state to a third operating state. The time of this transition is based on the longest total operating time of each of the imaging devices 108, 110. In the present example, this corresponds to the total operating duration TT2and in particular to the completion thereof at the time t4.From this, the specific duration of the common illumination pulse 212 can be calculated as the longest total operating duration (TT2)-shortest time delay (TD1). In addition, the start of the common illumination pulse 212 may be associated with the start of the exposure control pulse having the shortest time delay (t1) and the end of the common illumination pulse 212 may be associated with the end of the exposure control pulse of the imaging assembly having the longest total operating duration (t4).These time delays and operating times need not be calculated in real time, but instead may be preprogrammed during the configuration of an image processing job based on the requirements and image processing parameters of that job in the memory of the host / PLC. Note also that in some cases only a single group acquisition process is requested, e.g., for each execution of an image processing job, but the same method may be applied for an indeterminate number of group acquisition processes, as shown in FIG. 2, where group acquisition process 2 follows group acquisition process 1. Finally, while only two exposure signals 208 and 210 are shown being transmitted to two different imaging assemblies 108 and 110, it should be appreciated that the described approaches may be extended to any number of imaging devices.By using the above-mentioned approach, the lighting assembly can only remain active for a certain period of time, instead of being permanently switched on. This is particularly advantageous in configurations in which only one lighting assembly is associated with a group of imaging assemblies and in which the lighting assembly is connected to its host via a single communication bus. Thus, the lighting assembly may transition between a switched-off state (when pulse 212 is low) and an active state (when pulse 212 is high). Alternatively, the lighting assembly 212 may transition between a lower illumination intensity state (when the pulse 212 is low) and a higher illumination intensity state (when the pulse 212 is high).The above description refers to possible embodiments in the accompanying drawings. Alternative embodiments of the examples depicted in the drawings include one or more additional or alternative elements, methods, and / or devices. Additionally or alternatively, one or more of the example blocks may be combined, divided, rearranged, or omitted in the diagrams. The components represented by the blocks of the diagrams are implemented by hardware, software, firmware, and / or any combination of hardware, software, and / or firmware. In some examples, at least one of the components represented by the blocks is implemented by a logic circuit. As used herein, the term "logic circuit" is expressly defined as a physical device that includes at least one hardware component configured (e.g., by operating according to a predetermined configuration and / or by executing stored machine readable instructions) to control one or more machines and / or perform operations of one or more machines. Examples of logic circuits include one or more processors, one or more coprocessors, one or more microprocessors, one or more controllers, one or more digital signal processors (DSPs), one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more microcontroller units (MCUs), one or more hardware accelerators, one or more special purpose computer chips, and one or more system-on-chip devices (SoC). Some example logic circuits, such as ASICs or FPGAs, are specially configured hardware for performing operations (e.g., one or more of the operations described herein and illustrated in the flowcharts of this disclosure, if any). Some example logic circuits are hardware that executes machine readable instructions to perform operations (e.g., one or more of the operations described herein and represented by the flowcharts of this disclosure, if any). Some example logic circuits include a combination of specially configured hardware and hardware executing machine readable instructions. The above description relates to various operations and flowcharts described herein, which may be appended to illustrate the flow of these operations. All such flowcharts are representative of the example methods disclosed herein. In some examples, the methods represented by the flowcharts implement the devices represented by the block diagrams. Alternative implementations of the example methods disclosed herein may include additional or alternative operations. Moreover, operations of alternative implementations of the methods disclosed herein may be combined, split, rearranged, or omitted. In some examples, the operations described herein are implemented by machine readable instructions (e.g., software and / or firmware) stored on a medium (e.g., an accessible machine readable medium) for execution by one or more logic circuits (e.g., processor(s)). In some examples, the operations described herein are implemented by one or more configurations of one or more specially developed logic circuits (e.g., ASIC(s)). In some examples, the operations described herein are implemented by a combination of specially-developed logic circuits and machine-readable instructions stored on a medium (e.g., a tangible machine-readable medium) for execution by logic circuits.As used herein, each of the terms "accessible machine-readable medium," "non-transitory machine-readable medium," and "machine-readable storage device" is expressly defined as a storage medium (e.g., a disk of a hard disk drive, a digital versatile disk, a compact disk, flash memory, read-only memory, random access memory, etc.) on which machine-readable instructions (e.g., program code in the form of, e.g., software and / or firmware) execute for any suitable period of time (e.g., permanently, for a longer period of time (e.g., during execution of a program associated with the machine readable instructions) and / or for a short period of time (e.g., during caching of the machine readable instructions and / or during a buffering process)). Moreover, the terms "accessible machine-readable medium", "non-transitory machine-readable medium", and "machine-readable storage device" are expressly defined herein to exclude the transmission of signals. That is, none of the terms "accessible machine readable medium", "non-transitory machine readable medium", and "machine readable storage device" as used in the claims of this patent can be read to be implemented by a propagating signal.In the foregoing description, certain embodiments have been described. However, it will be apparent to one skilled in the art that various modifications and changes may be made without departing from the scope of the invention as set forth in the following claims. Accordingly, the specification and figures are to be regarded as illustrative rather than restrictive, and all such modifications are intended to be included within the scope of the present teachings. Moreover, the described embodiments / examples / implementations are not to be understood as mutually exclusive, but rather as potentially mutually reusable if such combinations are in some way permissive. In other words, any feature disclosed in any of the foregoing embodiments / examples / implementations may be included in any of the other foregoing embodiments / examples / implementations.The benefits, advantages, solutions to problems, and any elements that may result in the occurrence or enhancement of a benefit, advantage, or solution are not to be understood as critical, required, or essential features or elements in any or all of the claims. The invention is defined only by the appended claims, including any modifications made during the pendency of this application and all equivalents of the appended claims.Moreover, in this document, relational terms such as first and second, upper and lower, and the like may be used only to distinguish one entity or action from another entity or action without necessarily requiring or implying an actual such relationship or order between such entities or actions. The terms "comprises," "comprising," "has," "have," "has," "having," "contains," "containing," or any other variation thereof are intended to cover a non-exclusive inclusion such that a process, method, product, or device having a list of elements comprises, comprises, contains, not only comprises those elements, but may also comprise other elements not expressly listed or inherent to such process, method, product, or device. An element preceding "comprises... a", "has... a", "comprises... a" or "contains... a" does not exclude, without further restrictions, the existence of additional identical elements in the process, method, product or apparatus comprising the element. The terms "a" and "an" are defined as one or more unless expressly stated otherwise herein. The terms "substantially," "generally," "about," "about," or any other version thereof are defined to be readily understood by one of ordinary skill in the art, and in one non-limiting embodiment, the term is defined as within 10%, in another embodiment as within 5%, in another embodiment as within 1%, and in another embodiment as within 0.5%. The term "coupled" as used herein is defined as connected, but not necessarily directly and not necessarily mechanically. A device or structure that is "configured" in a particular manner is at least also configured in such a manner, but may also be configured in ways that are not listed.The Abstract of the Disclosure is provided to enable the reader to quickly ascertain the nature of the technical disclosure. It is provided with the understanding that it is not used to interpret or limit the scope or meaning of the claims. Furthermore, it can be seen from the foregoing detailed description that various features are summarized in various embodiments for the purpose of obscuring the disclosure. This type of disclosure is not to be interpreted as reflecting the intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims show, the inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description, each claim standing on its own as a separately claimed subject matter.

Claims

An imaging system comprising: a host device having a processor; a plurality of imaging devices, each of the plurality of imaging devices communicatively coupled to the host device; and an illumination assembly for illuminating at least one target imaged by each of the plurality of imaging devices, the illumination assembly communicatively coupled to the host device, each of the plurality of imaging devices being caused by the host to acquire image data during a group acquisition operation, wherein each of the plurality of imaging devices is associated with (i) a respective delay until a respective beginning of an exposure duration, (ii) the respective exposure duration over which image data is acquired, and (iii) a respective overall operation duration comprising the respective delay and the respective exposure duration, wherein, during the group acquisition process, the lighting assembly is caused by the host device to transition from a first operating state to a second operating state based on a shortest delay selected from each of the respective delays of each of the plurality of imaging devices, and wherein, during the group acquisition process, the lighting assembly is caused to transition from the second operating state to a third operating state based on a longest total operating duration selected from each of the respective total operating durations of each of the plurality of imaging devices.The system of claim 1, wherein the group detection process is triggered by the host device.The system of claim 1, wherein each of the plurality of imaging devices captures image data via a respective single exposure operation during the group acquisition operation.The system of claim 1, wherein for each of the plurality of imaging devices, the respective delay until the respective beginning of the exposure time is measured from a job trigger triggered by the host device.The system of claim 1, wherein the plurality of imaging devices are not associated with any other illumination assemblies.The system of claim 1, wherein the first operating state of the lighting assembly is the same as the third operating state of the lighting assembly.The system of claim 1, wherein the lighting assembly emits more light in the second operating state than in the first operating state.The system of claim 7, wherein in the first operating state the lighting assembly is disabled to emit no light and wherein in the second operating state the lighting assembly is enabled to emit light.The system of claim 1, wherein the host device is further configured to store, in a memory for each of the plurality of imaging devices, (i) the respective delay until the respective beginning of the exposure time, (ii) the respective exposure time over which the image data is acquired.The system of claim 1, wherein the lighting assembly is coupled to the host device via a single communication bus.The system of claim 1, wherein the host device, in response to execution of an image processing task, causes the plurality of imaging devices to successively perform multiple group acquisition operations.A method of operating an image processing system, comprising: (a) causing, by a host device having a processor, each of a plurality of imaging devices to acquire image data during a group acquisition operation, wherein each of the plurality of imaging devices is associated with (i) a respective delay until a respective beginning of an exposure time, (ii) the respective exposure time over which image data is acquired, and (iii) a respective total operation time comprising the respective delay and the respective exposure time; (b) causing, by the host device and during the group acquisition process, an illumination assembly to transition from a first operating state to a second operating state based on a shortest delay selected from each of the respective delays of each of the plurality of imaging devices, the illumination assembly operable to illuminate at least one target imaged by each of the plurality of imaging devices; and (c) causing, during the group acquisition process, the illumination assembly to transition from the second operating state to a third operating state based on a longest total operating duration selected from each of the respective total operating durations of each of the plurality of imaging devices.The method of claim 12, wherein the group detection process is triggered by the host device.The method of claim 12, wherein each of the plurality of imaging devices captures image data via a respective single exposure operation during the group acquisition operation.The method of claim 12, wherein for each of the plurality of imaging devices, the respective delay until the respective beginning of the exposure time is measured from a job trigger triggered by the host device.The method of claim 12, wherein no other illumination assemblies are operable to illuminate the at least one target imaged by each of the plurality of imaging devices.The method of claim 12, wherein the first operating state of the lighting assembly is the same as the third operating state of the lighting assembly.The method of claim 12, wherein the lighting assembly emits more light in the second operating state than in the first operating state.The method of claim 18, wherein in the first operating state the lighting assembly is deactivated to emit no light and wherein in the second operating state the lighting assembly is activated to emit light.The method of claim 12, wherein the lighting assembly is coupled to the host device via a single communication bus.The method of claim 12, further comprising executing an image processing task via the host device, wherein the image processing task comprises performing steps (a), (b), and (c) at least twice.

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