Vision system camera with mount for multiple lens types

This invention provides a vision system housing having a front plate assembly that accommodates a plurality of lens mount types. The front plate includes a central aperture that is located at a predetermined axial (camera axis) distance from a plane of an image sensor. The aperture is stepped from a wider diameter adjacent to the front to a narrower diameter more adjacent to the sensor. This arrangement enables threaded mounting of a plurality of lens mount types, for example M12 and C-Mount. The exterior (front) surface of the front plate includes threaded holes and a removable spring clip arrangement constructed to accommodate a liquid lens positioned over the aperture with an associated lens assembly mounted within the aperture and in optical communication with the liquid lens. The lens is operated using an electrical connection provided by a cable that interconnects with a multi-pin socket positioned on the front plate.

FIELD OF THE INVENTION

This invention relates to vision system cameras and more particularly to lens mounts for vision system cameras.

BACKGROUND OF THE INVENTION

Vision systems that perform measurement, inspection, alignment of objects and/or decoding of symbology (e.g. bar codes) are used in a wide range of applications and industries. These systems are based around the use of an image sensor, which acquires images (typically grayscale or color, and in one, two or three dimensions) of the subject or object, and processes these acquired images using an on-board or interconnected vision system processor. The processor generally includes both processing hardware and non-transitory computer-readable program instructions that perform one or more vision system processes to generate a desired output based upon the image's processed information. This image information is typically provided within an array of image pixels each having various colors and/or intensities. In the example of a symbology (barcode) reader, the user or automated process acquires an image of an object that is believed to contain one or more barcodes. The image is processed to identify barcode features, which are then decoded by a decoding process and/or processor obtain the inherent alphanumeric data represented by the code.

It is increasingly desirable to provide vision systems and associated vision system components that can be used for a variety of purposes. By way of example, an integrated sensor and single instruction, multiple data (SIMD) processor, which can be termed a vision system on a chip (VSoC), is shown and described in U.S. patent application Ser. No. 12/184,187, entitled VISION SENSORS, SYSTEMS AND METHODS, by E. John McGarry, et al., the teachings of which are incorporated by reference as useful background information. This architecture provided a highly versatile and widely applicable vision system platform for a variety of vision system tasks. The ability to provide a versatile system reduces costs by eliminating the need to provide a number of purpose-built vision system arrangements for specific applications. It is therefore desirable to provide such versatile vision system platforms. Other currently available arrangements of sensors and processors (e.g. digital signal processors (DSPs) can also be employed to provide a relatively compact and robust vision system.

While programs can be readily adapted for a particular vision system task, it is more of a challenge to adapt the system's physical package to that task. For example, some vision tasks call for a larger lens, such as a cine or C-mount unit, while others can be accomplished best with a smaller M12 thread (12 mm×0.5 mm thread) lens, also termed an “S-mount”, or more basically, an “M12” lens. Others are best suited to a liquid lens, or a similar arrangement. By way of further background, a liquid lens uses two iso-density liquids—oil is an insulator while water is a conductor. The variation of voltage passed through the lens by surrounding circuitry leads to a change of curvature of the liquid-liquid interface, which in turn leads to a change of the focal length of the lens. Some significant advantages in the use of a liquid lens are the lens' ruggedness (it is free of mechanical moving parts), its fast response times, its relatively good optical quality, and its low power consumption and size. The use of a liquid lens can desirably simplify installation, setup and maintenance of the vision system by eliminating the need to manually touch the lens. Relative to other autofocus mechanisms, the liquid lens has extremely fast response times. It is also ideal for applications with reading distances that change from object-to-object (surface-to-surface) or during the changeover from the reading of one object to another object.

The choice of lens type (e.g. C-mount, M12, liquid lens, etc.) can be driven by such factors as lighting/illumination, field of view, focal distance, relative angle of the camera axis and imaged surface, and the fineness of details on the imaged surface. In addition, the cost of the lens and/or the available space for mounting the vision system can drive the choice of lens.

It is therefore desirable to provide a vision system that can readily accommodate a variety of lens types while avoiding the need of costly changes to the vision system's physical housing or package. This vision system should be able to employ multiple lens types with no reduction in quality of the acquired image when compared with using a system that provides a discrete, purpose-built lens mount.

SUMMARY OF THE INVENTION

This invention overcomes the disadvantages of the prior art by providing a vision system housing having a front plate assembly that accommodates a plurality of lens mount types. The front plate includes a central aperture that is located at a predetermined axial (camera axis) distance from a plane of an image sensor. The aperture is stepped from a wider diameter adjacent to the front to a narrower diameter more adjacent to the sensor. This arrangement of diameter and relative depth within the front plate enables threaded mounting of a plurality of lens mount types, illustratively an M12 lens mount and C-Mount. The threaded base for the M12 lens mount is provided in the smaller-diameter interior portion of the front plate aperture, adjacent to the sensor. Additionally, the threaded base for the C-Mount lens is provided at the front of the front plate, adjacent to the exterior surface of the front plate and housing. The exterior (front) surface of the front plate includes threaded holes and a spring clip arrangement (fastened by screws) constructed and arranged to accommodate a liquid lens positioned over the aperture with an associated lens assembly mounted within the aperture and in optical communication with the liquid lens. The lens is operated using an electrical connection provided by a cable that interconnects with a multi-pin socket positioned on the front plate aside the aperture. The socket interconnects with processor circuitry within the housing that enables control of the liquid lens.

In an illustrative embodiment the vision system defines a housing that includes a front plate assembly comprising an aperture aligned relative to an image sensor located within an interior of the housing, the aperture including an outer step having a first diameter and in inner step have a second diameter smaller than the first diameter. The first step is constructed and arranged to receive a first lens type base and the second step is constructed and arranged to receive a second lens type base. By way of example, the outer step is constructed and arranged to receive a C-mount lens base and the inner step is constructed and arranged to receive an M12 lens base. Moreover, the front plate assembly is constructed and arranged to receive, over the aperture, a liquid lens module. A clip assembly, illustratively comprising a spring assembly with retaining shoulders that is secured by screws to threaded holes around the aperture, engages portions of the housing or shell of the liquid lens module. The front plate assembly also illustratively includes a first socket, interconnected with control circuitry within the housing, which receives a cable to operate the liquid lens module. A second socket can also interconnect the control circuitry with an illuminator. The front plate assembly is illustratively attached to a body section of the housing bolts having ends that are exposed at the outer face of the front plate assembly and pass into the body section. These ends can include threaded holes that receive fasteners that allow attachment of the front plate assembly to a mount or accessory.

More generally, in an illustrative embodiment, the vision system housing includes a main body section having an image sensor within the interior thereof. A front plate assembly is attached to the main body section. The front plate assembly includes threaded structures for selectively, removably and directly attaching at least three discrete types of lens thereto. By way of example, the three lens types can include a C-mount lens, and M12 lens and a liquid lens module.

DETAILED DESCRIPTION

With reference toFIGS. 1 and 2, a vision system that includes an external package or “housing”100is shown in detail. The housing100can be constructed from polymer, metal, composite or a variety of materials in accordance with ordinary skill. In an embodiment, it consists of a front plate section110, a main body section112and a rear section114. The front plate section (or “front plate”)110is joined to the main body and rear sections using four threaded bolts116that are seated within wells in the front plate110, and that engage threaded holes in the rear section, thereby compressing the three sections together against gaskets118that seal the housing against infiltration of moisture and other environmental agents. The construction of the housing is highly variable in alternate embodiments. For example, the housing can be constructed with an integrated or unitary rear and main body or a unitary front plate and main body. Likewise, other fastening techniques can be employed, such as employing joining clamps or clips between sections.

In this embodiment, the bolts116are located adjacent to each of four corners of the somewhat rectangular-cross-section housing. The bolts116each contain respective threaded wells at their front end that allow for the attachment of accessories using threaded fasteners, or the attachment of the housing itself to a mounting surface. Alternatively, the bolts116can be substituted with appropriate bolts that also pass through holes in a mounting surface or accessory (not shown), and collectively join the surface/accessory to the sections of the housing in appropriate compression.

The interior of the housing100supports an image sensor212(FIG. 2) that is arranged to acquire each image frame as an array of individual image pixels. In an embodiment, the sensor array is a CMOS sensor212(also termed an “imager”), which acquires image data in the form of pixel data. A cover glass210id provided to protect the sensor array212. The sensor212is mounted on a printed circuit board250secured as depicted near the front end of the housing. The sensor circuit board250also illustratively includes processing circuitry (e.g. a digital signal processor DSP) that receives the pixel data from the sensor array212and performs various vision system processes on the data in accordance with non-transitory computer-readable program instructions and/or firmware instructions. The sensor circuit board250is interconnected with various power, control and other associated circuit components located on a circuit board220in the rear114of the housing. The two board assemblies220,250are illustratively interconnected by a multi-lead cable222in this embodiment. Other arrangements of circuitry and interconnections are expressly contemplated. For example, in another embodiment, a VSoC arrangement (described above) can be provided to perform image acquisition and processing. The rear section114(and/or other sections110,112of the housing) can be constructed from aluminum so as to act as a heat sink that assists in dissipating heat generated within the housing by the circuitry (described further below).

An external connector (or a plurality of connectors)130are located at the rear side of the housing100for providing power, data and/or other interface functions. The connector(s) is/are operatively connected to the circuit board220. The rear also includes an external status and control panel140that provides the user with status indicators and feedback on vision system operations (for example, indicating whether a symbol has been properly identified and decoded). Appropriate on/off switches and other interface buttons can also be provided at this location, or at another appropriate location on the housing100.

The plane of the sensor212is oriented perpendicularly to the longitudinal axis (i.e. camera axis)230of the housing100. It resides within a space240that is open to an aperture150within a central region of the front plate110. The space240is bounded by an enclosing wall242(having a relatively planar sides that can define a rectangular cross-section tube) that provides clearance for the sensor212. The wall242extends from a step face244to the surface of the sensor circuit board250. The distance DS from the step face244to the plane of the sensor212is approximately 6 millimeters. The aperture150is defined by an outer step152and a narrower inner step154. Each step is threaded as described below. In particular, the outer step152defines a diameter DOS of approximately 25.4 millimeters (1 inch), and a depth (along the axial direction) LOS of approximately 5 millimeters. Likewise, the inner step154defines a diameter DIS of approximately 12 mm. The outer step152is female-threaded to a pitch of 32 threads per inch (TPI) and the inner step154is female-threaded to a pitch of 0.5 mm. In general, the positioning of the steps and size of the space are constructed and arranged to accommodate the focal length of each lens type being employed herein.

In an embodiment, the front plate assembly110is constructed from metal (e.g. die cast aluminum alloy), which is finished using an appropriate machining process. The casting includes the depicted recesses152,154and other supporting structures (i.e. walls242,251and252) for lenses and other internal components. Notably, the supporting walls242(etc.), which contact and/or surround the sensor circuit board250assist in directing heat away from the board250and its associated circuit components and into the housing structure, where the heat is dissipated into the surrounding ambient air. In alternate embodiments the layout and configuration of the supporting structures can vary. In general, the thickness of walls used in such supporting structures is selected to provide sufficient structural strength with respect to the material employed in constructing the front plate110. The front plate assembly110includes, along its front face164, a plurality of threaded holes160that can be female-threaded to any appropriate size, so as accept corresponding threaded screws (described below). These screws can be used to attach a plurality of fittings and accessories to the front plate.

Note that directional terms such as “front”, “rear”, “up”, “down”, “top” bottom”, “right”, and “left”, as well as their variants and synonyms, should be taken as relative conventions only, and not as absolute indications of orientation of a structure relative to the direction of prevailing gravitational force.

With reference particularly toFIG. 1, the face164of the front plate assembly110includes a pair of connection sockets170and172respectively oriented to the right and left of the aperture150(as viewed from the front). Both sockets include respective connectors, which are interconnected with the system's processor circuitry (i.e.250and220). The right socket170is employed to operate the optics of a liquid lens (described above, and again below). The left socket172is employed to interconnect and operate an illumination assembly that can be directly attached to the front plate via threaded holes160or can be separately mounted. The illumination assembly is described in further detail in commonly assigned U.S. patent application Ser. No. 13/302,858, entitled CAMERA SYSTEM WITH EXCHANGABLE ILLUMINATION ASSEMBLY, by Laurens Nunnink, filed on Nov. 22, 2011, and the teachings of which are expressly incorporated herein by reference as useful background information.

The perimeter180of the aperture150includes a circumferential spring assembly182with a pair of diametrically opposed, radially inwardly directed retaining shoulders184. The spring assembly182is removably secured to the front face164by opposed screws186(M2 thread in this embodiment) that threadingly seat into holes (502inFIG. 5). In an embodiment, the screws186are separated by a distance (on-center) of approximately 28 millimeters, taken through the camera axis (230). As described further below, the removable spring assembly is constructed and arranged to retain a liquid lens assembly.

It is contemplated that a user receives a housing100with a cap (not shown) to protect the aperture and sensor, and that the applicable lens is purchased separately—to be attached by the user in a straightforward manner as described further below. Alternatively, the lens can be provided to the housing by the manufacturer. In either case, there are a wide range of lens choices available.

Having described the generalized construction and function of the housing100and front plate assembly110according to an illustrative embodiment, the implementation of various types of lenses in conjunction with the housing is now described in further detail. With reference toFIGS. 3 and 4, the housing110is provided with an attached M12 lens310according to an embodiment. By way of non-limiting example, the lens is a commercially available M12 lens with a conventional M12 threaded base. The male thread of the lens is secured into the female thread of the narrower, more-inset step154, and is stopped from further inward threading, and generally locked in place using a counter nut320, which is initially threaded onto the lens310base before attachment to the front plate assembly110. The applied counter nut320can be adhered by the manufacturer (or another party) in place at an appropriate location along the lens using adhesive or another fixing technique. This ensures that, when the lens is tightened into place (e.g. by the user) to form a tight engagement with the front face430of the step154as shown, it is also positioned at a proper, predetermined distance with respect to the sensor's image plane. The lens310is thereby locked in place at a desired offset (to provide proper focal length) with respect to the plane of the sensor212. Alternatively, where the user seeks to vary the mounting position of the lens, the counter nut can remain unfixed to the lens thread and counter-rotated by the user (or another party) to secure the lens in a desired position.

The front end of the lens can include a radially outwardly oriented ring330that engages the inner perimeter of an optional, frustoconically shaped stopper410(FIG. 4). The stopper protects the region of the aperture150between the lens front and the outer step152, and avoids inadvertent loosening or readjustment of the tightened lens/counter ring310/320and protects against infiltration of dirt and moisture. The stopper410can be any acceptable shape, or alternatively omitted. It is secured to the front plate assembly110by a pressed-in friction fit that resides against the female threads in the outer step152. It is illustratively mounted by pressing it into the thread well until it seats against the front face430of the inner step154as shown (FIG. 4). The stopper can be constructed from an elastomeric material. In alternate embodiments, the stopper can employ a different securing system with respect to the housing front plate assembly110, such as clips or mating threads.

It should be clear that attachment and detachment of the exemplary M12 lens310is relatively straightforward, and entails the threaded rotation of only a few components with respect to the inner step154and (optionally) the outer step152. Thus, the user or the manufacturer can desirably assemble an M12 lens vision system from a few readily available components. Likewise, if the user desires a C-mount-lens-based vision system, the housing can be assembled as shown inFIGS. 5-7.

As shown, the male-threaded base512of the exemplary C-mount lens510is threadingly attached to the female threads of the outer step152as shown (FIG. 6). The base512is tightened until its rear shoulder620engages the perimeter180of the aperture150. The perimeter180is spaced from the plane of the sensor at an appropriate distance so as to provide the proper focal length for the lens510with respect to the sensor's image plane. The perimeter180upon which the lens shoulder620can be slightly recessed (as shown) relative to the surrounding front face164to provide the correct clearance, or it can be raised relative thereto to provide the proper focal length. In alternate embodiments, the step152and its front perimeter face can be a lockable insert that is adjustable within the surrounding front plate assembly (using an outer coaxial thread that mates between the insert and the front plate, for example) to allow the seating location of the lens to vary, thereby varying the focal length. Notably, the optics of the lens510, combined with the geometry of the front plate assembly110focuses received light rays so that they pass free of interference from the rear end630of the lens510through the smaller diameter step154, and into the space240. In this manner, the light rays received by the lens510are focused to cover the area of the sensor212.

The C-Mount lens can be optionally covered by a shroud (or cover) assembly710(FIG. 7) that primarily protects it from ingress of dirt/contaminants and moisture. The shroud710can also serve to protect against inadvertent change to the lens settings. The shroud assembly consists of a gasket plate720that covers the front face (164) and an overlying shroud base730. The gasket plate720and shroud base include through-holes that expose the central threaded holes (120) of each of the assembly bolts116. This allows the system to be mounted as described above or receive additional accessories on top of the shroud base730. The gasket plate720and shroud base730thereby cover and seal the sockets (170,172) in this configuration. In alternate embodiments, one or both of the sockets170,172can be exposed through the gasket plate720and shroud base730. The shroud base730and gasket plate720are secured to the front plate assembly110are compressibly secured by four screws (not shown) that thread into the screw holes160formed on the front plate assembly110. In this embodiment, the shroud base730is countersunk in the region of each threaded hole160to receive a correspondingly shaped machine screw. Different screws or any other fastener arrangement that secures the shroud base730and (optionally) the gasket plate720can be employed in alternate embodiments can be employed in alternate embodiments. The front ring732of the shroud base730receives the shroud body740, which overlies and covers the lens510. The shroud body740can be constructed as a single piece, or from a plurality of pieces (e.g. a main body and nose as shown). It can be secured to the ring732by a threaded interconnection or another fastening arrangement.

Notably, with reference toFIGS. 8-10, the versatility of the housing100and front plate assembly110enables mounting of an electronically operated, auto-focusing liquid lens810according to an illustrative embodiment. As described also above, a liquid lens uses two iso-density liquids—oil is an insulator while water is a conductor. The variation of voltage passed through the lens by surrounding circuitry leads to a change of curvature of the liquid-liquid interface, which in turn leads to a change of the focal length of the lens. Some significant advantages in the use of a liquid lens are the lens' ruggedness (it is free of mechanical moving parts), its fast response times, its relatively good optical quality, and its low power consumption and size. The use of a liquid lens can desirably simplify installation, setup and maintenance of the vision system by eliminating the need to manually touch the lens. As noted above, relative to other autofocus mechanisms, the liquid lens has extremely fast response times. It is also ideal for applications with reading distances that change from object-to-object (surface-to-surface) or during the changeover from the reading of one object to another object.

In this embodiment, the exemplary liquid lens810can be based upon a commercially available liquid lens component910(FIG. 9) available from Varioptic SA of France. The liquid lens component910is mounted within an outer shell/housing820that is secured in place by the spring shoulders184described above. It is expressly contemplated that alternate hold-down arrangements for the liquid lens can be employed. For example, the housing can include a C-mount base that engages the threads of the outer step152. An advantage of the spring-retained lens arrangement is that it allows for the positioning of the connector cable830in a location that leads properly to the socket170(where the cable's connector832is shown connected inFIG. 8). Note that the socket and connector can be any acceptable multi-pin arrangement that provides sufficient connections to control the lens.

The inner face of the lens' outer shell or housing820engages an O-ring (or other resilient structure that allows an open central aperture)920that, in turn, pressurably bears upon the circuit board922. This circuit board922includes the control circuitry employed according to the art to operate the focal length adjustment of the lens component910. The lens is compressed between the circuit board and the internal, fixed lens assembly940that focuses light rays from the liquid lens component onto the sensor212. The fixed lens assembly940is secured into the front plate assembly110by threads that engage the inner step154. A counter ring942prevents loosening of this lens assembly940. The pressure applied by the spring retaining shoulders184is sufficient to retain the lens component910free of movement and vibration, but this pressure also remains within the desired specification to avoid over-compression of the lens component910, which could degrade performance or burst the lens.

With reference briefly to the front view ofFIG. 10, the spring retaining shoulders are arranged to engage associated abutments1010on each of opposing sides of the lens outer housing/shell820. Like the spring assembly hold-down screws186, the abutments1010are located at a non-vertical and non-horizontal angle with respect to the geometry (top, bottom, right and left sides) of the system housing100. This allows for the cable830to exit the top end of the lens housing/shell820free of interference by the hold-down components. In this embodiment, the spring shoulders184(and abutments1010) are aligned along a line that is approximately perpendicular to the line between the screws186. In alternate embodiments a larger or smaller number of screws and/or spring shoulders184(among other fastening arrangements) can be used to retain the lens810with respect to the front face164of the housing100. Likewise, it is contemplated that the overall spring assembly can be constructed as a single unit with an appropriate number of retaining shoulders to secure the lens, or a multi-part unit each having one or more shoulders (as shown).

It is expressly contemplated that the arrangement of components in both (or either of) the internal fixed lens assembly942and the overlying liquid lens module (810) are highly variable in alternate embodiments. The depicted illustrative embodiment is an effective arrangement that can be assembled in a straightforward manner by the manufacturer or user.

It should be clear that the vision system housing and associated front plate construction provides a highly versatile system for selecting and “directly attaching” a variety of desirable lenses and lens mount types that are traditionally not interchangeable on a single housing without (free of) additional adapters. Such adapters can reduce accuracy, increase the chance of loosening of components and generally increase the system's complexity. The resulting vision system allows for fewer specialized components and more customization either by the manufacturer or end user. More particularly, the system provides the end user with the ability to change out lens types so that the system can be updates or re-tasked to a new use from an earlier use, as desired.

The foregoing has been a detailed description of illustrative embodiments of the invention. Various modifications and additions can be made without departing from the spirit and scope of this invention. Each of the various embodiments described above may be combined with other described embodiments in order to provide multiple features. Furthermore, while the foregoing describes a number of separate embodiments of the apparatus and method of the present invention, what has been described herein is merely illustrative of the application of the principles of the present invention. For example, while the illustrative housing is adapted for use with M12 and C-mount lens bases, it is expressly contemplated that adapters can be employed to allow for attachment of other lens types, such as the T-mount lens—for example the above-described alternate embodiment having an outer step insert. Likewise, the front plate assembly can be constructed and arranged to provide a different combination of mounts by appropriately sizing and threading the stepped apertures. Moreover, while various components are attached using threaded screws, it is expressly contemplated that other fastener types can be used for various interconnections, such as snap-connectors, rivets, clips, and the like. Also, in an embodiment, a plurality of front plate assemblies can be produced and provided to a standard main body section and rear to allow for further versatility of the vision system. In addition, any process or processor herein can comprise one or more electronic hardware components, software in the form a non-transitory computer-readable medium of program instructions, or a combination of hardware and software. More generally, the term “process” should be taken broadly to include various combinations of hardware components and/or software program steps that perform one or more functions in a system or method. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this invention.