Patent Publication Number: US-2023132784-A1

Title: Thermally stable sawmill scanner

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 63/263,317, filed on Oct. 29, 2021, which is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The disclosure pertains to housings for optical systems. 
     BACKGROUND 
     Optical scanners can be used in a sawmill to provide log dimensions, permitting optimum use of each log. In some cases, a laser line beam is projected onto a log surface while the log is simultaneously translated on a carriage and a camera views the log with the projected line beam and acquires data on log shape. Multiple laser line beam zones can be used to provide 3D log profiles for use in determining how each log should be further processed. 
     Sawmills present a challenging environment that makes precise, repeatable scanning difficult. Challenges includes wide temperature ranges, moisture, vibration, dust as well as the need to operate reliably so that production need not be interrupted to service scanner systems. These challenges are particularly difficult in high resolution scanning in which even small positional errors must be avoided. For these and other reasons, improved scanning approaches are needed. 
     SUMMARY 
     In some examples, scan assemblies comprise a scan assembly housing that defines an interior volume, the scan assembly housing including a side wall having a sealing surface portion situated proximate a top of an interior surface. A lid is provided that includes an inward extension having a sealing surface that faces the interior surface the sealing surface portion of the scan assembly housing. At least one compressive seal is situated between the sealing surface portion of the scan assembly housing and the sealing surface of the lid, wherein the scan assembly housing and the lid, as assembled, compress the compressive seal so that the interior volume of the scan assembly housing is sealed by the lid. In examples, at least one light source is operable to project a patterned beam and at least one camera situated to image the projected patterned beam, wherein the at least one light source and the at least one camera are secured to the scan assembly housing and are situated in the interior volume. In examples, the at least one camera includes a first camera and a second camera situated so that respective camera axes intersect a measurement volume irradiated by the light source. An image processor can be coupled to the first camera and the second camera and configured to transmit coordinates associated with imaging of the patterned beam wherein the image processor is thermally coupled to the lid. In some embodiments, the interior ribs define coupled cavities in an interior of the scan assembly housing and wherein each rib has a sealing surface portion contiguous with the sealing surface portion. At least one light source is operable to project a patterned beam and at least one camera situated to image the projected patterned beam having respective optical axes, wherein the at least one light source and the at least one camera are secured to the scan assembly to orient respective optical axes. The at least one light source can be thermally coupled to the lid and mechanically coupled to the scan assembly housing. In examples, the at least one light source is a line beam source, and the optical axes of the first camera and the second camera are at angles of between 5° and 45° with respect to the axis of the line beam source, and the first camera and the second camera are situated equidistant from the line beam source, and the optical axes of the first and second cameras and the line beam source are coplanar. The first camera and the second camera can be secured to a bottom of the scan assembly housing that is opposite the lid and mechanically coupled to the scan assembly housing and thermally coupled to the lid. In some examples, the axes of the first camera and the second camera are situated symmetrically with respect to an axis of the patterned beam. The first camera and the second camera can be secured so that respective camera axes intersect. A data communication port that is operable to provide data communication for the scan assembly can be provided and a scanner power supply coupled to the data communication port and operable to power the first camera, the second camera, and the at least one light source based on at least one electrical input to the data communication port. 
     In some examples, a synchronizer is coupled to the data communication port to receive time stamped encoder data and global timing data. In further examples, fasteners are situated to secure the lid to the scan assembly housing, wherein each of the plurality of fasteners is made of a material having a thermal conductivity of less than 20 W/m/K. In an example, the fasteners are Hastelloy screws. The side wall of the scan assembly housing can include a seal guide portion that is coupled to the sealing surface portion, wherein the seal guide portion is situated proximate a top of an interior surface of the housing. The lid can include on O-ring groove, and the sealing surface of the lid is situated in the O-ring groove. The at least one light source can include at least one pulsed laser. 
     Methods comprise securing at least one optical system to a first housing portion, the optical system having an optical axis associated with receiving or delivering an optical beam. Electrical power is provided to the at least one optical system with a communication connection and heat associated with the at least one optical system to a thermally coupled second housing portion. The first housing portion can be secured to a second housing portion to define an enclosure so that the first housing portion is decoupled from thermal expansion of the second housing portion. The securing can produce a piston seal between the first housing portion and the second housing portion. 
     The foregoing and other features and advantages of the disclosed technology will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a plan view of a scan assembly housing. 
         FIG.  1 A  is a sectional view of the scan assembly housing of  FIG.  1   . 
         FIG.  1 B  is a plan view of a lid operable to seal an interior volume of the scan assembly housing. 
         FIG.  1 C  illustrate securing the lid of  FIG.  1 B  to the scan assembly housing of  FIG.  1   . 
         FIG.  2    illustrates an alternative housing and lid that are sealable with a piston seal. 
         FIG.  3 A  is a perspective view of a scan assembly housing in which multiple cavities are defined. 
         FIG.  3 B  is a plan view of the scan assembly housing of  FIG.  3 A . 
         FIG.  3 C  is an elevational view of a lid for the scan assembly housing of  FIGS.  3 A- 3 B . 
         FIG.  3 D  is a plan view of the lid of  FIG.  3 C . 
         FIG.  3 E  illustrates optical axis directions associated with the scan assembly housing of  FIG.  3 A . 
         FIGS.  3 F- 3 G  are sectional views illustrating a compressive seal situated to seal the lid of  FIG.  3 C  to the scan assembly housing of  FIG.  3 A . 
         FIG.  4    illustrates a method of sealing an optical housing in which a portion of the optical housing is used as a heat sink and is thermo-mechanically separated from other portions of the optical housing. 
         FIG.  5 A  is a sectional view of a representative housing have a thermally uncoupled end. 
         FIG.  5 B  illustrates an optical system aligned by being pressed toward a reference surface defined on a housing. 
         FIG.  6    is a block diagram of a representative method of thermo-mechanically uncoupling an optical alignment surface from a heat sink portion of an enclosure. 
         FIG.  7    illustrates a multi-scanner system. 
         FIGS.  8 A- 8 C  illustrate a scanner housing. 
     
    
    
     DETAILED DESCRIPTION 
     Introduction 
     The disclosure pertains to methods and apparatus that permit stable alignment of optical systems even in the presence of large temperature variations, particularly temperature variations produced by heat generated in the operation of the optical systems and any associated processing hardware. In many practical application, optical systems are situated to receive an optical beam or transmit an optical beam along an axis that remains stable, even as portions of a housing that enclose or support the optical system expand and contract in response to operation of the optical system or to environmental changes. In some examples, one, two, three or more optical systems are secured to one or more portions of a housing or other support, while other portions of the housing or support are used to remove heat from the enclosure. The examples are described below with reference to optical scanning assemblies for use in sawmills, but the disclosed methods and apparatus can be used with other optical assemblies or other systems in which stable mechanical alignment is needed and are particularly suited for applications in which optical systems must function in difficult environments due to heat, dust, vibration, humidity, or other environmental conditions. 
     Scanning optical assemblies typically use semiconductor lasers whose useful life is limited by migration of defects into the laser active area where they function as optical absorbers. Absorption increases temperature around the defect which in turn reduces the bandgap of the semiconductor. As the bandgap narrows, the material absorbs more light leading to reduced performance and sometimes a runaway absorption process that leads to catastrophic optical damage. Minimizing the temperature of the device slows the migration of defects and increases laser useful life. One way to minimize temperature is to leave a laser off when a scanner is not actively exposing an image with the laser. Thus, pulsing the laser can increase laser useful life. The disclosed approaches permit the use of pulsed semiconductor lasers and can provide control of pulse timing. 
     Spatial resolution and accuracy are superior when objects are suitably close to a scanner. Scanning large boards with high accuracy therefore requires multiple scanners. In this case, scanners can be installed such that the projected laser lines touch at the edges. For example, to scan a 20 foot board, 10 adjacent scanners can be used. In this case, the scanners are mounted 2 feet apart, each scanner having a laser illuminating a 2 foot section of the board and all 10 lasers effectively producing a single 20 foot long laser line, or scan zone, down the length of the board. In such a configuration, when one scanner is taking an image, lasers associated with any adjacent scanners are to be turned off. To provide ample scan data, both the exposure time of each image and the time between images is preferably minimized or reduced. To ensure that scanners do not take images that overlap temporally, the scanners must be synchronized temporally. This is frequently done with a separate electrical input to the scanner, sometimes called a sync line, the synch line providing a clock signal that each scanner can use to time scans. When assembling data from multiple scanners to build an image of a board or log, a process must receive a signal or other indication of board location when each scan was taken. This is frequently accomplished by attaching an encoder to a conveyance that moves the board through the scan zone. The encoder signal is frequently delivered to each scanner with yet another electrical input. 
     Scanners typically have at least two electrical connectors, one for data and one for all other signals, for example, timing, encoder signals and power. The data connection is often a standard RJ45 connector, however, the second connector is typically a custom connector that adds cost and complexity associated with cable routing and management and also adds another layer of complexity associated with trouble shooting when something goes wrong. For this reason, it would be advantageous to perform all these functions over the data cable. Further, as discussed above, deformations of the scanner housing over temperature are to be reduced or avoided for successful use in challenging environments. Larger housings needed for multiple electrical connections have larger deformations. Reducing a number of electrical connections permits a housing size to be reduced and including all the required functionality into a single connector such as a single RJ45 connector can reduce beam pointing errors. It can be especially convenient to use a single RJ45 connector and connect to scanners use ethernet to provide power as well as data and control communications. 
     General Considerations and Terminology 
     As used in this application and in the claims, the singular forms “a,” “an,” and “the” include the plural forms unless the context clearly dictates otherwise. Additionally, the term “includes” means “comprises.” Further, the term “coupled” does not exclude the presence of intermediate elements between the coupled items. 
     The systems, apparatus, and methods described herein should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The disclosed systems, methods, and apparatus are not limited to any specific aspect or feature or combinations thereof, nor do the disclosed systems, methods, and apparatus require that any one or more specific advantages be present or problems be solved. Any theories of operation are to facilitate explanation, but the disclosed systems, methods, and apparatus are not limited to such theories of operation. 
     Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth below. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed systems, methods, and apparatus can be used in conjunction with other systems, methods, and apparatus. Additionally, the description sometimes uses terms like “produce” and “provide” to describe the disclosed methods. These terms are high-level abstractions of the actual operations that are performed. The actual operations that correspond to these terms will vary depending on the particular implementation and are readily discernible by one of ordinary skill in the art. 
     In some examples, values, procedures, or apparatus are referred to as “lowest”, “best”, “minimum,” or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, or otherwise preferable to other selections. 
     Examples are described with reference to directions indicated as “above,” “below,” “upper,” “lower,” and the like. These terms are used for convenient description, but do not imply any particular spatial orientation. For convenience, some examples describe containers and walls of such container s are referred to as side walls or container bottoms or floors. Surface from which optical beams are emitted or to which optical beams are directed are referred to as front surfaces. 
     As used herein, the term “housing” refers to a container that defines a cavity that can enclose at least portions of optical systems such as laser beam sources and detectors as well as electrical systems used in operation of the laser beam sources and detectors. The term “housing” is also used to refer to selected portions of an enclosure such as, for example, a rectangular or cylindrical box that is closed with by a lid. Cross-sections of housings can have polygonal, oval, elliptical or other simple or complex shapes and housings can define multiple cavities that can be coupled via passages or be uncoupled. For convenience, some examples area described with reference to an enclosure formed by a rectangular box having a lid that is securable to the box to form a sealed housing. A lid can be configured to close any end of a housing. 
     In some examples, compressive seals are situated to be compressed by two or more surfaces associated with a housing. Such compressive seals can be made of rubber, plastic, or other compressible materials and formed as flat gaskets or other shapes, but O-rings are especially convenient. In some examples, container lids seal an interior volume using compressive seals that are compressed by one or more interior surfaces of a container. The lid and container are referred to as being thermo-mechanically isolated because thermal expansion, contraction, or warping of the lid and the container are uncoupled to each other by the compressive seal. In typical examples, the lid is then used as a heat sink for optical and electrical systems situated within the housing such as camera systems, light sources such as pattern beam sources, laser line scanners, imaging processing circuitry, communication and networking hardware, electrical power convertors and power supplies such as switch mode power supplies. In these examples, optical systems are secured to the housing and expansion of the lid is thermo-mechanically uncoupled from the container by the compressive seal, tending to allowing optical axes associated with the optical systems to be maintained or subjected to acceptably small deviations. Alternatively, the container can serve as a heat sink, and optical systems secured to a lid. 
     The compressive seals used in some examples can be referred to as “piston seals” as a compressible material such as an O-ring is situated to seal side surfaces of a housing and a lid so that the lid can move in and out of the cavity formed by the housing without subjecting the housing to forces that would tend to deform the housing. 
     In the disclosed examples, optical beams such as laser beams are directed toward a target that is to be measured. These beams are generally patterned beams, i.e., beams such as line beams, multi-line beams, beams comprising a plurality of illumination areas arranged along a line or in two or more dimensions, or other configurations. Two or more cameras are generally situated to have axes that are directed to a common measurement volume to be incident to a common target. 
     Any of the examples and features of the examples disclosed below can be combined with any other examples and the associated features. 
     Example 1 
     Referring to  FIG.  1   , a container  102  has a front wall  104 , a back wall  106 , side walls  108 ,  110  and a bottom  112 . An intermediate wall  114  extends between the front wall  104  and the back wall  106  to define cavities  116 A,  116 B. In the example of  FIG.  1   , one or more optical systems  118 ,  120  are secured to the front wall  104  and have respective optical axes  124 ,  126  that can be associated with directing optical beams from or to optical systems. For example, one or both of optical systems  118 ,  120  can be imaging systems or line beam generators or other optical systems. Optical windows  128 ,  130  permit optical radiation to enter or exit the container  102  while sealing the cavities  116 A,  116 B. In some cases, the optical systems  118 ,  120  include optical windows and additional windows are not required. A tab  103  secured the container  102  can be used to align optical axes  124 ,  126  or other portions of the housing  102  can be used for mounting and alignment. In the example of  FIG.  1   , two optical systems are shown, but in other examples 2, 3, 4, or more optical systems can be provided along with associated cavities. In still further examples, two or more optical systems are situated in a single cavity. One or more electrical connectors  134 ,  136  are secured to the container  102  and provide power, data communication, data acquisition, and control signals for the optical systems  118 ,  120 . Fastener portions  141 - 144  are provided in the enclosure walls so that a such as illustrated in  FIG.  1 B  can be secured to the enclosure  102 . 
     Referring to  FIG.  1 B , a cover  150  includes protrusions  124 A,  124 B (shown as extending out of the plane of  FIG.  1 B ) that extend into the cavities  116 A,  116 B, respectively of  FIG.  1    with the cover  150  connected to the container  102 . Through-holes  161 - 164  corresponding to fastener portions  141 - 144  are provided to connect the lid  150  to the container  102  with screws or other fasteners. 
       FIG.  1 A  is a sectional view of an enclosure  100  defined using the cover  150  and the container  102 . The container  102  is sealable to the protrusions  124 A,  124 B with compressive gaskets  166 ,  168  such as O-rings that contact and are compressed by inner surfaces  170 ,  172  of respective container sides  108 ,  110  and surfaces  171 ,  173  of the intermediate wall  114 . In some cases, portions of inner surfaces and/interior wall surfaces are machined or polished to promote sealing with a gasket. The enclosure  100  thereby decouples thermal expansion, contraction, and warping (or other dimensional changes of the cover  150 ) from the container  150 . The cover  150  is secured to the container  150  and separated with a flexible spacer  174  so that the cover  150  and the container  102  are mechanically isolated. Compression of the gaskets  166 ,  168  by deformation of the cover  150  typically does not provide sufficient force to deform the container  102  and the axes of the optical systems secured to the container  102  (such as at the front wall  104 ) are not significantly disturbed. 
     Gasket seals as illustrated are robust and permit the use of optical systems in such enclosures in difficult environments. This sealing mechanism permits the cover  150  to move into and out of the container  102  and is referred to herein as a “piston seal.” In this configuration, one more sealed cavities such as cavities  116 A,  116 B are formed that are suitable for enclosing optical components, electronic systems, and other hardware to be shielded from environmental problems such as dust and humidity. In addition, because any warping, expansion, contraction of the lid  150  is substantially uncoupled to the container  102 , the lid  150  can serve as a heat sink. As shown in  FIG.  1 A , thermally conductive plates  119 ,  121  thermally couple the optical systems  118 ,  120  to the lid  150 . In other examples, optical systems can be secured to a lid and thermally coupled to a container so that the container serves as a heat sink. While two cavities are used in this example, one, two, three, or more can be provided. 
     The lid  150  and the container  102  can be coupled together with fasteners such as screws, rivets, or other fasteners. As shown in the partial sectional view of  FIG.  1 C , a screw  182  in inserted into through hole  161  and into threaded bore  141 . The spacer  174  is compliant, permitting the lid  150  and the container  102  to be fixed to each other while still permitting the enclosure  102  to be substantially isolated from any mechanical changes in the lid  150 . As shown in  FIG.  1 C , an aperture  180  permits wires and other electrical connectors and/or fill gas to be coupled into both the cavities  116 A,  116 B. 
     Example 2 
     Referring to  FIG.  2   , an example enclosure  200  includes a lid  250  that is coupled to a container  202  to define cavities  224 ,  226 . Interior surfaces of the enclosure  202  further include sealing surface  203 ,  205  that are situated to contact O-rings  220 ,  222 . An interior wall  209  includes interior surfaces  210 ,  216  that further include contact surfaces  211 ,  217  situated to contact the O-rings  220 ,  222 , respectively. The lid  250  includes projections  224 A,  226 A corresponding to the cavities  224 ,  226 , respectively and having contact surfaces  221 ,  223 . The lid  250  can be coupled to the container  202  with screws such as representative screws  252 ,  254  that secure a flexible cover  256  to the container  202 . The cover  256  can also be fastened to the lid  250  with rivets, adhesives, or other fasteners. An aperture  214  is defined in the interior wall  209  to permit wires and other electrical connectors to pass between the cavities  224 ,  226  and fill gas to be coupled into both. 
     Example 3 
     Referring to  FIGS.  3 A- 3 B , a container  300  defines cavities  302 - 306  that can retain optical systems, processor systems, amplifiers, power convertors, communications interfaces, or other optical, electrical, or computational systems. As shown, the cavities  303 ,  304 ,  306  are coupled to respective apertures  322 ,  324 ,  326  that permit transmission and reception of optical radiation and are defined in an exterior wall  301 . Typically, optically transmissive windows are situated in the apertures to seal the cavities. In one example, the cavities  322 ,  326  retain camera systems and the cavity  324  retains a patterned beam source such as a line beam generator. Faces  320 A,  320 B of the enclosure  300  are angled so that optical axes  301 A- 301 C associated with the cavities  302 ,  304 ,  306  intersect. The axes  301 A,  301 C are symmetric about the axis  301 B, but other arrangements are possible. The cavities  302 - 306  are separated by interior walls  312 ,  314 ,  316 ,  318  that include respective apertures  312 A,  314 A,  316 A,  318 A so that the cavities  302 - 306  are internally coupled. A top surface  333  is configured for forming a piston seal as discussed in detail below (see  FIG.  3 E ) and aperture  330  is provided for a communication connector or cable, such as an Ethernet or USB connector or cable as wells as a power cable, or power can be derived from Ethernet or other communication connections. 
     Referring to  FIGS.  3 C- 3 D , a lid  350  for the container  300  includes projections  352 - 356  corresponding to cavities  302 - 306 . The projections  352 - 356  extend from a plate  360  and have by O-ring sealing areas as indicated at  362 - 367  for establishing seals with the container exterior wall  301  and the interior walls  312 - 318 . The projections  352 - 356  include respective first step portions  372 - 376  and second step portions  382 - 386 . As assembled to the container, a respective seal is formed at each projection with an O-ring, but in other examples, a single perimeter O-ring can be used. 
       FIG.  3 E  is a plan view of an enclosure formed with the lid  350  and the container  300  showing the orientation of the optical axes  3011 ,  301 B,  301 C. Referring to the sectional view of  FIG.  3 F , a representative electrical or optical assembly  391  is situated in the cavity  304  and the lid  350  and the projection  354  as well as the step portions  374 ,  384 . Referring to the partial sectional view of  FIG.  3 G , an O-ring  397  is situated between sealing surfaces  394 ,  395  of the lid  350  and the container  300 , respectfully. A window  390  is situated in the aperture  324 . A beveled surface  396  and stepped surfaces  374 ,  398  facilitate O-ring placement while sealing the lid  350  to the container  302 . A gap  399  separates the lid  350  and the container  300  so that thermal expansion, contraction, warping, or other deformation of the lid  350  do not tend to alter the container  300 . 
     Example 4 
     Referring to  FIG.  4   , an enclosure  400  is formed of a lid  450  and a container  402  that are sealed with an O-ring  416 . Apertures in the lid  450  are configured to retain optical windows  411 ,  413  that permit optical beams to be transmitted and received with optical systems  410 ,  412 , respectively. In this example, the optical systems  410 ,  412  are secured to the lid  450  which can be secured as needed using threaded holes  452 ,  453 , or other fasteners. The optical systems  410 ,  412  are thermally coupled to the container  402  with thermal coupling members  420 ,  422 . An electronic system  414  can include a power convertor, communication interface, camera and scan control systems or other components and is thermally coupled to the container with a thermal coupling member  424 . In typical examples, power and communication are provided from a connector  406  using, for example, power over ethernet. A power convertor can be configured to provide suitable voltages and currents for various components, but not all such connections are shown for clarity of illustration. 
     Example 5 
     Referring to  FIG.  5 A , an assembly  500  includes a container  502  and a container end  504  that is thermo-mechanically uncoupled from the container  502  with an O-ring  506 . Top and bottom lids are not shown and, in this example, the container  502  has a rectangular box shape. Other shapes can be used as may be convenient. The O-ring  506  extends about a perimeter of the end  504  so that the end  504  is movable with respect to the container  502 . As shown, optical systems  510 - 515  such as detection systems (for example cameras) or illumination systems receive or direct radiation via apertures  520 - 525  defined in the container  502  as indicated by the arrows. Electrical systems  540 ,  542  can be secured to the end  504 . Typically, at least some portions of the electrical systems are thermally coupled to the end  504 . Electrical connectors  541 ,  543  are coupled to cables  550 ,  551 , respectively for communication with remote electronics or processing systems indicated at  560 . The container  502  is generally secured to establish optical axis directions for the optical systems  510 - 515  and deformation of the end  504  during operation generally tends to not change optical axis directions. For example, mounting flanges  555 ,  557  can be secured to the container  502 . Alternatively, optical systems can be secured to the end  504  and electrical systems secured to the container  502  so that the container  502  is allowed to move in response to heating or environmental changes while the end  504  remains fixed. In addition, top and bottom lids that are fixedly secured to the container  502  can also be used for optical system mounting. In some cases, some electrical systems or components can be secured to the same surfaces or parts to which optical systems are secured. 
     Example 6 
     While an optical system can be secured to a wall of a container for alignment, in some examples an optical system is aligned by urging one or more portions onto a reference surface defined in container wall. For example, as shown in  FIG.  5 B , an enclosure  580  contains an optical system  582  that is urged toward a container wall  584  that is secured to an opposite container wall  586 . by a spring  585 . A container led  590  is coupled to form a piston seal using an O-ring  592 . 
     Example 7 
     Referring to  FIG.  6   , a method  600  includes providing an optical reference surface and fixing an optical axis of at least one optical system based on the optical reference surface at  602 . In some cases, the optical reference surface is a mounting surface for one or more optical systems. In other examples, optical axes of one or more optical systems are determined using the reference surface by, for example, pressing the optical system toward the reference surface using a spring or other flexible member with the optical system secured to a different surface. At  604 , heat sources such as associated electronics area coupled to a floating member and mechanically secured at  606 . At  608 , the enclosure is sealed and at  610  can be filled with a suitable gas. 
     Example 8 
     Referring to  FIG.  7   , a representative multi-scanner system  700  includes first and second scanners  702 ,  704  that are coupled by single connectors  703 ,  705 , respectively, to an ethernet switch  708 . Additional scanners can be provided but are not shown for convenient illustration. The scanner  702  includes one or more lasers  710 , cameras  712 , an internal clock  714 , a synchronizer  716 , an image processor  717 . The lasers  710  can be configured to produce continuous or pulsed beams, and as noted above, the use of pulsed beams can permit lasers to last longer. Other scanners such as the scanner  704  can be similar. The internal clock  714  includes one or more oscillators that can provide timing information and timing is aligned with so-called global timing provided by a scan timing synchronizer  721  to the ethernet switch  708 . Typically, the oscillators in the internal clock  714  exhibit drift; and are not accurate enough to maintain synchronization of multiple scanners. For this reason, the scan timing synchronizer  721  is used to maintain a single “global time” for the system  700  and regularly sends network packets with a number that represents a current global time at which each packet was sent. For example, when a first packet is sent by the scan timing synchronizer  721  to the scanner  702  at time T 1  (via the ethernet switch  708 ), when first packet arrives, the scanner  702  receives the first packet at local time T 1 ′ at the scanner  702  and also knows the time T 1  at which the first packet was sent. A second packet is sent by the scan timing synchronizer  721  at T 2  and the scanner  702  receives the second packet at local time T 2 ′ and knows the time T 2  at which the second packet was sent. Based on a difference between the times the first and second packets are sent and received, an offset Δ between global time and local time at the scanners  702  be established as Δ=½(T 1 ′−T 1 −T 2 ′+T 2 ). The offset Δ is then used to correct local time to global time. Other scanners are similarly synchronized, and synchronization can be repeated periodically. In this way all scanner clocks are set to system global time and image data is associated with global time. Positions of scan data from different scanners can be established, and if pulsed lasers are used, temporal overlap of laser pulses from different scanners can be avoided. 
     The single connectors  703 ,  705  are also used to provide power to the scanners  702 ,  704  as well as to send and receive timing packets, camera data, and scan control commands. In this example, single cables  703 A,  705 A terminate at the respective connectors  703 ,  705  and at the ethernet switch  708  and power distribution is provided by respective power buses  702 A,  704 A. Each of the scanners  702 ,  704  directs laser beams to a load  730  (typical logs or lumber) and images the load  730  as indicated schematically at  734 ,  736 , respectively. The load  730  is transported by a log stage  738  that is coupled to an encoder  740  that communicates load position to the scan synchronizer  721  so that load positions for each scanner at each time can be correlated. As a result, each of the scanners  702 ,  704  can return (X,Y) coordinates of scanned logs or lumber to the ethernet switch and these coordinates can then be communicated to one or more processing systems such as computer  750  to determined how the scanned logs or lumber are to be further processed. 
     As shown in  FIG.  7   , communication of power, data, and timing signals are provided to and from each scanner with a single ethernet connector via the ethernet switch  708 . The scanners return (X,Y) coordinates of the load, and communication of full images is not required. Timing information (global time packets) are also provided to the scanners via the ethernet connection and the ethernet switch  708 . This permits each of the scanners to be compact, limiting thermal distortions which can degrade measurement of loads. 
     Example 9 
     Referring to  FIGS.  8 A- 8 C , another representative enclosure  800  includes a single piece container  802  that is sealable with a lid  804 . The container  802  defines a cavity  812  in which one or more image processors, laser sources, cameras, clock circuits, and other components can be placed. The cavity  812  is generally divided into a plurality of subcavities that are sealed to the lid  804  with sealing surfaces on container sides and on ribs that separate the subcavities.  FIG.  8 A  shows an O-ring  822  that is retrained in a groove  816  having portions  818 ,  820  that are situated facing the cavity  812  or away from the cavity  812 . As shown in  FIGS.  8 B- 8 C , the O-ring  822  seals a subcavity  805  and an O-ring  832  is situated to seal a subcavity  834 . The lid  804  can be secured to the container  802  using screws or other fasteners situated in holes  840 ,  842 . While screws of various materials can be used, a low conductivity material (&lt;10, 15, or 20 W/m/K) such as nickel-chromium-iron-molybdenum alloys (for example, Hastelloy) can permit a scanner housing temperature to remain uniform. For example, low thermal conductivity limits distortion-inducing heat from the lid  804  from propagating to a perimeter of the enclosure  802 . This is contrary to conventional approaches which distribute heat broadly to control thermal effects. 
     In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are only preferred examples and should not be taken as limiting the scope of the disclosure.