Abstract:
A coordinate measurement device comprises an articulated arm having a first end, a second end, and a plurality of jointed arm segments therebetween. Each arm segment defines at least one axis of rotation. A laser scanner assembly is coupled to the second end of the arm and is rotatable about a last axis of rotation of the articulated arm. The laser scanner assembly comprises a laser and an image sensor. The laser is positioned on an opposite side of the last axis of rotation from the image sensor.

Description:
PRIORITY INFORMATION 
     This application claims the priority benefit as a continuation under 35 U.S.C. §120 to U.S. patent application Ser. No. 13/449,211 (filed 17 Apr. 2012, now issued as U.S. Pat. No. 8,438,747), which claims the priority benefit as a continuation under 35 U.S.C. §120 to U.S. patent application Ser. No. 13/016,879 (filed 28 Jan. 2011, now issued as U.S. Pat. No. 8,176,646), which claims the priority benefit as a continuation under 35 U.S.C. §120 to U.S. patent application Ser. No. 12/487,535 (filed 18 Jun. 2009, now issued as U.S. Pat. No. 7,908,757), which claims the priority benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/106,096 (filed 16 Oct. 2008), the entirety of which is hereby expressly incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to coordinate measurement machines and, more particularly, to coordinate measurement machines with laser scanners. 
     2. Description of the Related Art 
     Rectilinear measuring systems, also referred to as coordinate measuring machines (CMMs) and articulated arm measuring machines, are used to generate highly accurate geometry information. In general, these instruments capture the structural characteristics of an object for use in quality control, electronic rendering and/or duplication. One example of a conventional apparatus used for coordinate data acquisition is a portable coordinate measuring machine (PCMM), which is a portable device capable of taking highly accurate measurements within a measuring sphere of the device. Such devices often include a probe mounted on an end of an arm that includes a plurality of transfer members connected together by joints. The end of the arm opposite the probe is typically coupled to a moveable base. Typically, the joints are broken down into singular rotational degrees of freedom, each of which is measured using a dedicated rotational transducer. During a measurement, the probe of the arm is moved manually by an operator to various points in the measurement sphere. At each point, the position of each of the joints must be determined at a given instant in time. Accordingly, each transducer outputs an electrical signal that varies according to the movement of the joint in that degree of freedom. Typically, the probe also generates a signal. These position signals and the probe signal are transferred through the arm to a recorder/analyzer. The position signals are then used to determine the position of the probe within the measurement sphere. See e.g., U.S. Pat. Nos. 5,829,148 and 7,174,651, which are incorporated herein by reference in their entireties. 
     Increasingly, PCMM&#39;s are used in combination with an optical or laser scanner. In such applications the optical or laser scanner typically includes an optics system, a laser or light source, sensors and electronics that are all housed in one box. The laser scanner box is then, in turn, coupled to the probe end of the PCMM and to a side of the probe. The various locations that existed for mounting the laser scanning box include positioning the box on top of the probe, forward and below the axis of the probe, and/or off to the side of the probe. In this manner, 2-dimensional and/or 3-dimensional data could be gathered with the laser scanner and combined with the position signals generated by the PCMM. See e.g., U.S. Pat. No. 7,246,030. 
     While such PCMM and laser scanner combinations have been useful. As mentioned above, the purpose of PCMM&#39;s is to take highly accurate measurements. Accordingly, there is a continuing need to improve the accuracy of such devices. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention is the realization that such prior art systems suffer from a number of inefficiencies. For example, prior art systems typically require a repeatable kinematic mount that would allow the laser scanner to be easily removed and replaced from the arm. Such mounts are generic so that many different types of scanners can be mounted to the same CMM. These generic mounts place the laser scanner in non-optimal locations which results in less accurate laser scanning performance The various locations that existed for mounting the laser scanning box were on top of the last axis, forward and below the last axis, or off to the side of the last axis, as discussed further below. 
     Accordingly, one embodiment of the present invention comprises an optical position acquisition member. The member can include a base plate that has an opening configured to receive a CMM measuring probe. A laser and an optical sensor can both mount on the plate such that the sensor is generally collinear with the laser and the opening, with the opening between the laser and the sensor. 
     In another embodiment, an articulated arm CMM is provided. The articulated arm can include a plurality of articulated arm members, a measuring probe, a receiving portion at a distal end, and a base at a proximal end. A base plate can mount on the receiving portion and include a hole positioned such that the measuring probe passes through the hole when mounted. The base plate can couple to a laser and an optical sensor located on opposite sides of the hole. 
     In yet another embodiment, a coordinate measurement device includes an articulated arm and a laser scanner assembly. The articulated arm can have a first end, a second end, and a plurality of jointed arm segments therebetween. Each arm segment can define at least one axis of rotation of the articulated arm, and a last axis of the arm can be defined by bearings near a distal end of the arm. The laser scanner assembly can couple to the second end of the arm and be rotatable about the last axis of rotation of the articulated arm. Additionally, the laser scanner assembly can include a laser and an image sensor, the laser positioned on an opposite side of the last axis of rotation from the image sensor. Further, at least one of the laser and image sensor can overlap the bearings. 
     All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiment(s) disclosed. In addition, the individual embodiments need not provide all or any of the advantages described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying figures showing illustrative embodiments of the invention, in which: 
         FIG. 1  is a perspective view of an embodiment CMM arm with a laser scanner; 
         FIG. 1A  is a side view of the CMM arm of  FIG. 1 ; 
         FIG. 1B  is a top view of the CMM arm of  FIG. 1 ; 
         FIG. 2  is a perspective view of a coordinate acquisition member of the CMM arm of  FIG. 1 ; 
         FIG. 2A  is a side view of the coordinate acquisition member of  FIG. 2 ; 
         FIG. 2B  is a top view of the coordinate acquisition member of  FIG. 2 ; 
         FIG. 2C  is a side cross-sectional view of the coordinate acquisition member of  FIG. 2 , at  2 C- 2 C; 
         FIG. 2D  is a side outline view of the coordinate acquisition member of  FIG. 2 , indicating various dimensions; 
         FIG. 3  is an exploded side view of the coordinate acquisition member of  FIG. 2 ; 
         FIG. 3A  is a back view of a non-contact coordinate detection device of  FIG. 3 , at  3 A- 3 A; 
         FIG. 3B  is a front view of a main body of a coordinate acquisition member of  FIG. 3 , at  3 B- 3 B; 
         FIG. 4A  depicts an alternative coordinate acquisition member; 
         FIG. 4B  depicts a side outline view of the coordinate acquisition member of  FIG. 4A , indicating various dimensions; 
         FIG. 5A  depicts an alternative coordinate acquisition member; 
         FIG. 5B  depicts a side outline view of the coordinate acquisition member of  FIG. 5A , indicating various dimensions; 
         FIG. 6A  depicts an alternative coordinate acquisition member; 
         FIG. 6B  depicts a side outline view of the coordinate acquisition member of  FIG. 6A , indicating various dimensions; 
         FIG. 7A  depicts an alternative coordinate acquisition member; 
         FIG. 7B  depicts a side outline view of the coordinate acquisition member of  FIG. 7A , indicating various dimensions; and 
         FIG. 7C  depicts a front outline view of the coordinate acquisition member of  FIG. 7A , indicating various dimensions. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1-1B  illustrate one embodiment of a portable coordinate measuring machine (PCMM)  1  in accordance with the present invention. In the illustrated embodiment, the PCMM  1  comprises a base  10 , a plurality of rigid transfer members  20 , a coordinate acquisition member  50  and a plurality of articulation members  30 - 36  connecting the rigid transfer members  20  to one another. Each articulation member  30 - 36  is configured to impart one or more rotational and/or angular degrees of freedom. Through the various articulation members  30 - 36 , the PCMM  1  can be aligned in various spatial orientations thereby allowing fine positioning and orientating of the coordinate acquisition member  50  in three dimensional space. 
     The position of the rigid transfer members  20  and the coordinate acquisition member  50  may be adjusted using manual, robotic, semi-robotic and/or any other adjustment method. In one embodiment, the PCMM  1 , through the various articulation members  30 , is provided with seven rotary axes of movement. It will be appreciated, however, that there is no strict limitation to the number of axes of movement that may be used, and fewer or additional axes of movement may be incorporated into the PCMM design. 
     In the embodiment PCMM  1  illustrated in  FIG. 1 , the articulation members  30 - 36  can be divided into two functional groupings based on their operation, namely: 1) those articulation members  30 ,  32 ,  34 ,  36  which allow the swiveling motion associated with a specific transfer member (hereinafter, “swiveling joints”), and 2) those articulation members  31 ,  33 ,  35  which allow a change in the relative angle formed between two adjacent members or between the coordinate acquisition member  30  and its adjacent member (hereinafter, “hinge joints”). While the illustrated embodiment includes four swiveling joints and three hinge joints positioned as to create seven axes of movement, it is contemplated that in other embodiments, the number of and location of hinge joints and swiveling joints can be varied to achieve different movement characteristics in a PCMM. For example, a substantially similar device with six axes of movement could simply lack the swivel joint  30  between the coordinate acquisition member  50  and the adjacent articulation member  20 . In still other embodiments, the swiveling joints and hinge joints can be combined and/or used in different combinations. 
     In various embodiments, the coordinate acquisition member  50  comprises a contact sensitive member  55  (depicted as a hard probe) configured to engage the surfaces of a selected object and generate coordinate data on the basis of probe contact, as depicted in  FIGS. 2-3 . In the illustrated embodiment, the coordinate acquisition member  50  also comprises a non-contact scanning and detection component that does not necessarily require direct contact with the selected object to acquire geometry data. As depicted, the non-contact scanning device comprises a non-contact coordinate detection device  60  (shown as a laser coordinate detection device/laser scanner) that may be used to obtain geometry data without direct object contact. It will be appreciated that various coordinate acquisition member configurations including: a contact-sensitive probe, a non-contact scanning device, a laser-scanning device, a probe that uses a strain gauge for contact detection, a probe that uses a pressure sensor for contact detection, a device that uses an infrared beam for positioning, and a probe configured to be electrostatically-responsive may be used for the purposes of coordinate acquisition. Further, in some embodiments, a coordinate acquisition member  50  can include one, two, three, or more than three coordinate acquisition mechanisms. 
     With particular reference to  FIG. 3 , in various embodiments of the PCMM  1 , the various devices which may be used for coordinate acquisition, such as the laser coordinate detection device  60 , may be configured to be manually disconnected and reconnected from the PCMM  1  such that an operator can change coordinate acquisition devices without specialized tools. Thus, an operator can quickly and easily remove one coordinate acquisition device and replace it with another coordinate acquisition device. Such a connection may comprise any quick disconnect or manual disconnect device. This rapid connection capability of a coordinate acquisition device can be particularly advantageous in a PCMM  1  that can be used for a wide variety of measuring techniques (e.g. measurements requiring physical contact of the coordinate acquisition member with a surface followed by measurements requiring only optical contact of the coordinate acquisition member) in a relatively short period of time. Although, as depicted, only the laser coordinate detection device  60  is removed, in some embodiments the contact sensitive member  55  can also be removed and replaced in a similar manner. 
     In the embodiment of  FIG. 2 , the coordinate acquisition member  30  also comprises buttons  41 , which are configured to be accessible by an operator. By pressing one or more of the buttons  41  singly, multiply, or in a preset sequence, the operator can input various commands to the PCMM  1 . In some embodiments the buttons  41  can be used to indicate that a coordinate reading is ready to be recorded. In other embodiments the buttons  41  can be used to indicate that the location being measured is a home position and that other positions should be measured relative to the home position. In other embodiments the buttons  41  may be used to record points using the contact sensitive member  55 , record points using the non-contact coordinate detection device  60 , or to switch between the two devices. In other embodiments, the buttons  41  can be programmable to meet an operator&#39;s specific needs. The location of the buttons  41  on the coordinate acquisition member  50  can be advantageous in that an operator need not access the base  10  or a computer in order to activate various functions of the PCMM  1  while using the coordinate acquisition member  50 . This positioning may be particularly advantageous in embodiments of PCMM having transfer members  20  that are particularly long, thus placing the base  10  out of reach for an operator of the coordinate acquisition member  50  in most positions. In some embodiments of the PCMM  1 , any number of operator input buttons (e.g., more or fewer than the two illustrated), can be provided. Advantageously, as depicted the buttons  61  are placed on the handle  40  in a trigger position, but in other embodiments it may be desirable to place buttons in other positions on the coordinate acquisition member  50  or anywhere on the PCMM  1 . Other embodiments of PCMM can include other operator input devices positioned on the PCMM or the coordinate acquisition member  50 , such as switches, rotary dials, or touch pads in place of, or in addition to operator input buttons. 
     With particular reference to  FIG. 1 , in some embodiments, the base  10  can be coupled to a work surface through a magnetic mount, a vacuum mount, bolts or other coupling devices. Additionally, in some embodiments, the base  10  can comprise various electrical interfaces such as plugs, sockets, or attachment ports. In some embodiments, attachment ports can comprise connectability between the PCMM  1  and a USB interface for connection to a processor such as a general purpose computer, an AC power interface for connection with a power supply, or a video interface for connection to a monitor. In some embodiments, the PCMM  1  can be configured to have a wireless connection with an external processor or general purpose computer such as by a WiFi connection, Bluetooth connection, RF connection, infrared connection, or other wireless communications protocol. In some embodiments, the various electrical interfaces or attachment ports can be specifically configured to meet the requirements of a specific PCMM  1 . 
     With continued reference to  FIG. 1 , the transfer members  20  are preferably constructed of hollow generally cylindrical tubular members so as to provide substantial rigidity to the members  20 . The transfer members  20  can be made of any suitable material which will provide a substantially rigid extension for the PCMM  1 . The transfer members  20  preferably define a double tube assembly so as to provide additional rigidity to the transfer members  20 . Furthermore, it is contemplated that the transfer  20  in various other embodiments can be made of alternate shapes such as those comprising a triangular or octagonal cross-section. 
     In some embodiments, it can be desirable to use a composite material, such as a carbon fiber material, to construct at least a portion of the transfer members  20 . In some embodiments, other components of the PCMM  1  can also comprise composite materials such as carbon fiber materials. Constructing the transfer members  20  of composites such as carbon fiber can be particularly advantageous in that the carbon fiber can react less to thermal influences as compared to metallic materials such as steel or aluminum. Thus, coordinate measuring can be accurately and consistently performed at various temperatures. In other embodiments, the transfer members  20  can comprise metallic materials, or can comprise combinations of materials such as metallic materials, ceramics, thermoplastics, or composite materials. Also, as will be appreciated by one skilled in the art, many of the other components of the PCMM  1  can also be made of composites such as carbon fiber. Presently, as the manufacturing capabilities for composites are generally not as precise when compared to manufacturing capabilities for metals, generally the components of the PCMM  1  that require a greater degree of dimensional precision are generally made of a metals such as aluminum. It is foreseeable that as the manufacturing capabilities of composites improved that a greater number of components of the PCMM  1  can be also made of composites. 
     With continued reference to  FIG. 1 , some embodiments of the PCMM  1  may also comprise a counterbalance system  110  that can assist an operator by mitigating the effects of the weight of the transfer members  20  and the articulating members  30 - 36 . In some orientations, when the transfer members  20  are extended away from the base  10 , the weight of the transfer members  20  can create difficulties for an operator. Thus, a counterbalance system  110  can be particularly advantageous to reduce the amount of effort that an operator needs to position the PCMM  1  for convenient measuring. In some embodiments, the counterbalance system  110  can comprise resistance units (not shown) which are configured to ease the motion of the transfer members  20  without the need for heavy weights to cantilever the transfer members  20 . It will be appreciated by one skilled in the art that in other embodiments simple cantilevered counterweights can be used in place or in combination with resistance units. Further, although as depicted there is only one counterbalance system  110  unit, in other embodiments there can be more. 
     In some embodiments, the resistance units can comprise hydraulic resistance units which use fluid resistance to provide assistance for motion of the transfer members  20 . In other embodiments the resistance units may comprise other resistance devices such as pneumatic resistance devices, or linear or rotary spring systems. 
     As is known in the art, the position of the contact sensitive member  55  in space at a given instant can be calculated by knowing the length of each rigid transfer member  20  and the specific position of each of the articulation members  30 - 36 . Each of the articulation members  30 - 36  can be broken down into a singular rotational degree of motion, each of which is measured using a dedicated rotational transducer. Each transducer outputs a signal (e.g., an electrical signal), which varies according to the movement of the articulation member in its degree of motion. The signal can be carried through wires or otherwise transmitted to the base  10 . From there, the signal can be processed and/or transferred to a computer for determining the position of the coordinate acquisition member  50  and its various parts in space. 
     In one embodiment, the transducer can comprise an optical encoder. In general, each encoder measures the rotational position of its axle by coupling is movement to a pair of internal wheels having successive transparent and opaque bands. In such embodiments, light can be shined through the wheels onto optical sensors which feed a pair of electrical outputs. As the axle sweeps through an arc, the output of the analog encoder can be substantially two sinusoidal signals which are 90 degrees out of phase. Coarse positioning can occur through monitoring the change in polarity of the two signals. Fine positioning can be determined by measuring the actual value of the two signals at the instant in question. In certain embodiments, maximum accuracy can be obtained by measuring the output precisely before it is corrupted by electronic noise. Additional details and embodiments of the illustrated embodiment of the PCMM  1  can be found in U.S. Pat. No. 5,829,148, the entirety of which is hereby incorporated by reference herein. 
     With reference to  FIGS. 1 ,  1 A, and  1 B, in some embodiments, the PCMM  1  can comprise one or more rotatable grip assemblies  122 ,  124 . In the illustrated embodiment, the PCMM  1  can comprise a lower rotatable grip assembly  122  and an upper rotatable grip assembly  124 . Advantageously, having a lower rotatable grip assembly  122  and an upper rotatable grip assembly  124  disposed on a last transfer member  21 , allows the operator to easily use both hands in positioning the PCMM  1 . In other embodiments, the PCMM  1  can comprise one, or more than two rotatable grips. Additional details of the grip assemblies can be found in Applicant&#39;s co-pending U.S. patent application Ser. No. 12/057,966, filed Mar. 28, 2008, the entirety of which is hereby incorporated by reference herein 
     While several embodiments and related features of a PCMM  1  have been generally discussed herein, additional details and embodiments of PCMM  1  can be found in U.S. Pat. Nos. 5,829,148 and 7,174,651, the entirety of these patents being incorporated by reference herein. While certain features below are discussed with reference to the embodiments of a PCMM  1  described above, it is contemplated that they can be applied in other embodiments of a PCMM such as those described in U.S. Pat. Nos. 5,829,148 or 7,174,651, U.S. patent application Ser. No. 11/963,531, filed Dec. 21, 2007, entitled “IMPROVED JOINT AXIS FOR COORDINATE MEASUREMENT MACHINE”, U.S. patent application Ser. No. 11/943,463, filed Nov. 20, 2007, entitled “COORDINATE MEASUREMENT DEVICE WITH IMPROVED JOINT” and U.S. patent application Ser. No. 11/775,081, filed Jul. 9, 2007, entitled “JOINT FOR COORDINATE MEASUREMENT DEVICE”, the entire contents of these patents and patent applications being incorporated herein by reference. 
     As depicted in  FIG. 1 , the PCMM can include a coordinate acquisition member  50  at an end of its arm.  FIGS. 2-3  depict the coordinate acquisition member  50  in more detail. As shown, the coordinate acquisition member  50  can include a contact sensitive member  55  and a laser coordinate detection device  60  facing a front end  54 . The coordinate acquisition member  50  can further attach to a handle  40  at a lower end  51  and the PCMM  1  at a rear end  52 . The coordinate acquisition member  50  can further include a top end  53 . At the rear end  52 , the coordinate acquisition member  50  can further include a data connection (not shown) with the hinge  31 , such as a slip ring connection, a direct wire, or some other connection. This can allow data transfer between the coordinate acquisition member  50  and the PCMM  1 . The PCMM  1  can include similar data transfer elements along its arm, allowing data transmission between the coordinate acquisition member  50  and the base  10 , or any peripheral computing medium external to the PCMM arm. 
     The laser coordinate detection device  60  can include a light source  65  (depicted as a laser) and an optical sensor  70  (depicted as a camera), and can acquire positional data by a method of triangulation. The laser or light source  65  can create an illuminated laser plane including a laser line L 4 . The camera  70  can be displaced from the laser plane and further be non-parallel to the laser plane. Accordingly, the camera  70  will view points as higher or lower, depending on their position further or closer to the laser  65 . Similarly, the camera  70  will view points illuminated by the laser as being either further to the left or the right, according to their actual position relative to the laser  65 . Comparing the geometric relationship between the position and orientation of the laser  65  and the camera  70  will allow one of skill in the art to appropriately translate the position of the image of the laser-illuminated point in the image captured by the camera  70  to an actual position in space in conjunction with the position of the coordinate acquisition member  50  itself. 
     In  FIG. 1 , a plurality of the axes of movement are marked according to their proximity to the coordinate acquisition member  50 . As depicted, the coordinate acquisition member  50  can pivot about a last axis of rotation L 1  on a swivel  30 . The last axis of rotation L 1  and the swivel  30  are more clearly depicted in  FIG. 2C . As shown, the laser coordinate detection device  60  mounts bearings  150 ,  151  at an end of the PCMM arm  1 . The orientation and position of the bearings  150 ,  151  can substantially define the last axis L 1 . Thus, the laser coordinate detection device  60  can rotate about the last axis L 1 , independent of the contact sensitive member (depicted as a probe)  55 . In some embodiments, the contact sensitive member  55  is not rotatable, reducing potential error from any eccentricity between the contact sensitive member  55  and the last axis L 1 . The swivel  30  can rotate about a second to last axis of rotation L 2  at the end of the last rigid transfer member  21  on a hinge joint  31 . Like the bearings  150 ,  151  and the last axis L 1 , the second to last axis L 2  can be substantially defined by a hinge shaft  140 . As depicted, the last axis L 1  can also be considered a roll axis, and the second to last axis can also be considered a pitch axis. Similarly, rotation about a third to last axis L 3  can be considered a yaw axis. 
     The handle  40  can also generally comprise a pistol-grip style, which can further include ergonomic grooves corresponding to human fingers (not shown). The handle can also have a generally central axis L 5 . Optionally, within the handle  40 , a battery  42  can be held. In some embodiments the handle  40  can include a sealed battery, as described in U.S. Publication No. 2007/0256311A1, published Nov. 8, 2007, which is incorporated by reference herein in its entirety. Further, the battery  42  can insert through the bottom of the handle  40 . In other embodiments, the battery  42  can insert through the top of the handle  40 , and the handle  40  can release from the coordinate acquisition member  50  to expose an opening for battery insertion and removal. The battery can be provided to power the laser scanner, rotational motors about one of the articulation members  30 - 36 , and/or other types of probes or devices. This can reduce current draw through the arm, decrease overall power requirements, and/or reduce heat generated in various parts of the arm. 
     In one embodiment, data can be transmitted wirelessly to and from either the coordinate acquisition member  50  or the non-contact coordinate detection device  60  and the base of the PCMM  1  or to an external device such as a computer. This can reduce the number of internal wires through the PCMM  1 . It can also reduce the number of wires between the PCMM  1  and the computer. 
     Above the handle  40 , the coordinate acquisition member  50  can include a main body  90 , best depicted in  FIG. 3 . The main body  90  can connect directly to the hinge  31  at the rear end  52  of the coordinate acquisition member  50 . The main body  90  can further hold the contact sensitive member  55 . In preferred embodiments, the main body  90  can even further hold the contact sensitive member  55  in near alignment with the swivel  30 , such that an axis of the contact sensitive member  55  extends near the last axis L 1  of the swivel  30 . In some embodiments, the axis of the contact sensitive member  55  can pass through the last axis L 1  of the swivel  30 . In other embodiments the axis of the contact sensitive member  55  can pass within 10 mm of the last axis L 1 , this distance corresponding to D 3  (depicted in  FIG. 2D ). 
     As best depicted in  FIG. 3B , the main body  90  can further include a mounting portion  91 , a recess  92 , and a data port  93 , configured to interact with a laser coordinate detection device (depicted as a laser scanner)  60 . The laser scanner  60 , as best depicted in  FIG. 3A , can include an upper housing  80 , a laser  65 , and a data port  101 . As shown in  FIG. 3 , the laser scanner  60  can be configured to mount on the main body  90  as an auxiliary body (which can include different devices in other embodiments). The upper housing  80  can be shaped to match the mounting portion  91 , and can accordingly be received by that portion. The recess  92  can be shaped to receive the laser  65  when the mounting portion  91  receives the upper housing  80 . Upon these interactions, the data ports  93 ,  101  can interact to pass information between the main body  90  and the laser scanner  60  (and accordingly further along the PCMM arm  1  as described above). The laser coordinate detection device  60  can further include a base-plate  75 . The base-plate  75  can include a port  85  configured to receive the contact sensitive member  55  when the laser scanner  60  mounts to the main body  90 . Additionally, the base-plate  75  can include assembly holes  104  that can interact with assembly holes  94  on the main body  90 , along with fasteners (not shown), to secure the main body  90  and laser scanner  60  together. It will be clear that a variety of screws and other fasteners can be used to attach the main body  90  and the laser scanner  60 . For example, in some embodiments they can be attached by a snap-lock mechanism, allowing easy attachment and removal. Further, in some embodiments a repeatable kinematic mount can be used, where the laser scanner  60  can be removed and remounted to the main body  90  without tools. It can be remounted with a high level of repeatability through the use of a 3-point kinematic seat as is known in the industry. 
     When the PCMM  1  is intended to provide accurate position data, the PCMM can be designed to minimize the errors at both the contact sensitive member  55  and at the non-contact coordinate detection device  60 . The error of the coordinate acquisition member  50  can be reduced by minimizing the effect of the errors of the last three axes on both the contact sensitive member  55  and the non-contact coordinate detection device  60 . The maximum error of the contact sensitive member  55  can be represented in the following equations as Ep, which is primarily a function of the errors of each of the last three axes (L 1 -L 3 ) and the distances from the probe center to the axes. Likewise, the error of the non-contact coordinate detection device  60  can be represented as Es and is primarily a function of the errors of each of the last three axes (L 1 -L 3 ) and the distances from the optical center point P 1  to the axes.
 
 Ep =( d 1* e 1)+( d 2* e 2)+( d 3* e 3)
 
 Es =( d 1′* e 1)+( d 2′* e 2)+( d 3′* e 3)
 
     Where e1, e2, and e3 represent the absolute value of the angular error at each of the three last axes of rotation at the articulation members  30 ,  31 , and  32  respectively; and d 1 , d 2 , d 3 , d 1 ′, d 2 ′, and d 3 ′ represent the distance from the respective axes to either the probe center or the optical center point (or laser focus) P 1 . As will be explained in further detail to follow, the PCMM  1  can enhance the accuracy of the coordinate acquisition member  50  by supplying a superior geometry to reduce both errors Ep and Es while at the same time balancing the Center of Gravity (CG) of the coordinate acquisition member  50  over the handle  40  and reducing the overall height of the coordinate acquisition member  50  (d 4 ) as shown in  FIG. 2D . 
     When the laser scanner  60  mounts the main body  90 , a variety of geometric properties can arise between coordinate acquisition elements. For example, as depicted the camera  70 , the contact sensitive member  55 , and the laser  65  can be directly integrated with the last axis L 1 . For example, as depicted the camera  70 , contact sensitive member  55 , and laser  65  can be generally collinear when viewing from the front (e.g. along axis L 1 ), with the contact sensitive member  55  in the middle and aligned with the last axis L 1  (i.e. d 1 =0). Further, as depicted the upper housing  80 , contact sensitive member  55 , and the laser  65  can be arranged generally parallel to the last axis L 1 . However, the camera  70  can be oriented at an angle relative to the last axis L 1  so as to view the laser plane. 
     Such arrangements can be advantageous in a number of ways. For example, in this arrangement the angular position of the elements about L 1  can be approximately equal (with the exception of a 180 degree offset when on different sides of the last axis L 1 ), simplifying data processing requirements. As another example, providing these elements aligned with the last axis L 1  can facilitate counterbalancing the weight of these elements about the last axis, reducing error from possible deflection and easing movement about the axis. As depicted in  FIG. 2D , the center of gravity (CG) of the coordinate acquisition member  50  can lie along L 1 . Even further, the error associated with the angle of rotation about the last axis L 1  is amplified by the perpendicular distance from the axis to the center of the laser plane emitted by the laser  65  (depicted as d 1 ′ in  FIG. 2D ). In this orientation, the perpendicular distance is minimized. In some embodiments, the perpendicular distance from the center of the laser plane to the last axis can be no greater than 35 mm. Notably, in other embodiments it may be desirable to move the laser  65  even closer to the last axis L 1 , such as by aligning directly therewith. However, the accuracy of the contact sensitive member  55  is also partially dependent on its proximity to the last axis L 1 ; and, as described below, some other advantages can arise from separating the laser  65  from the camera  70 . 
     As further depicted, when the laser scanner  60  mounts the main body  90 , the contact sensitive member  55  and the laser coordinate detection device  60  can form a compact design. For example, the laser  65  and/or the camera  70  can extend past the one or both of the bearings  150 ,  151 . As depicted, the laser  65  extends, at least partially, beyond the bearings  151  but not the bearings  150 ; and the camera  70  extends beyond both bearings. In other embodiments, these elements can extend to the bearings, and not pass them. Generally, causing these elements to overlap reduces the necessary length of the coordinate acquisition member  50 . 
     In some embodiments such compact designs can allow the coordinate acquisition elements to be closer to the second to last axis L 2 , as well as the last axis L 1 . Accordingly, the distance between the second to last axis L 2  and the points of measurement (e.g. at the tip of the contact sensitive member  55  and/or at the focus P 1  of the camera  70 ) can be reduced. As the error in the angular position of the coordinate acquisition member  50  along the second to last axis L 2  is amplified by these distances, this also reduces the error of the PCMM  1  in other ways. For example, the compact design can also reduce error related to the distance from the focus P 1  to the third to last axis L 3 , represented as d 3 ′. Additionally, providing the elements of the coordinate acquisition member  50  closer to the second and third to last axes L 2 , L 3  can reduce deflection, reducing error even further. In some embodiments the contact sensitive member  55  can be within 185 mm of the second and/or third to last axis L 2 , L 3 , and the focus P 1  of the camera  70  can be within 285 mm of the third to last axis. As best depicted in  FIG. 2D , the compact design can further bring a center of gravity (CG) of the coordinate acquisition member  50  closer to a central axis L 5  of the handle  40 . In some embodiments, the distance between the center of gravity and the central axis of the handle  40  can be no greater than 20 mm. As yet another advantage to the compact design, the vertical height d 4  of the coordinate acquisition member  50  can be reduced, allowing measurement in tighter spots. In some embodiments the height can be no greater than 260 mm. Notably, as the coordinate acquisition member  50  in the depicted embodiment rotates about the last axis L 1 , the height d 4  can also represent a maximum length of the coordinate acquisition member  50 . 
     In some embodiments, the laser scanner  60  can include additional advantages. For example, the laser scanner  60  can isolate the laser  65  from heat generated by the other parts of the PCMM arm  1 . For example, as depicted in  FIG. 3 , a base plate  75  holds the laser  65  at one end and the camera  70  at the other, separated by the contact sensitive member  55 . In some embodiments the base plate  75  can include a material with a low coefficient of thermal expansion such as Invar, Ceramic, or Carbon Fiber. Reducing thermal expansion can reduce changes in the position and orientation of the laser  65  and/or the camera  70 , which could create problems such as introducing additional error into the measurements. Similarly, the base plate  75  can also include a material with a low thermal conductivity, hindering transmission of heat, for example, from the camera  70  to the laser  65  or PCMM  1 . 
     As depicted, the camera  70  can be held in an upper housing  80  of the laser scanner  60 , and in some embodiments the upper housing can include multiple cameras. The upper housing  80  can include materials such as aluminum or plastic. Additionally, the upper housing  80  can protect the camera  70  from atmospheric contaminants such as dust, liquids, ambient light, etc. Similarly, the laser  65  can be protected by the recess  92  of the main body  90 . In some embodiments, the recess  92  can include a thermal isolation disc or plate with a low coefficient of thermal expansion and/or conductivity, protecting the laser from external heat and substantially preserving its alignment. 
     In many embodiments, the electronics  160  associated with the laser coordinate detection device  60  can create a substantial amount of heat. As discussed above, various components can be protected from this heat with materials having low coefficients of thermal expansion and conductivity for example. As depicted, the electronics  160  can be positioned in the upper housing  80  of the laser scanner  60 . 
     However, in other embodiments the electronics  160  can be positioned further from the sensors  55 ,  60 , such as in a completely separate housing. For example, in some embodiments the electronics  160  can be held by the laser scanner  60  in a separate housing, also attached to the base plate  75 . In other embodiments, the electronics  160  can be located further down the PCMM  1 , such as in a rigid transfer member  20  or in the base  10 . Moving the electronics  160  further down the PCMM  1  can reduce weight at the end of the arm, minimizing deflection of the arm. Similarly, in some embodiments the electronics  160  can be completely outside the PCMM  1 , such as in a separate computer. Data from the sensors  55 ,  70  can be transmitted through the PCMM  1  on an internal cable in the arm, wirelessly, or by other data transmission methods. In some embodiments, data ports  93 ,  101  can include spring loaded pins such that no cables are externally exposed. 
     As another advantage of the depicted embodiment, the depicted layout of the system can use a smaller volume. The laser coordinate detection device  60  can sometimes operate on a theory of triangulation. Accordingly, it may be desirable to leave some distance between the laser  65  and the camera  70 . The depicted embodiment advantageously places the contact sensitive member  55  within this space, reducing the volume of the coordinate acquisition member  50 . Additionally, the last axis L 1  also passes through this space, balancing the system and reducing the coordinate acquisition member&#39;s  50  rotational volume. In this configuration, the combination of axis and laser scanner can further be uniquely optimized to reduce weight, as the more compact design reduces deflection, and accordingly reduces the need for heavy-load bearing materials. 
     To further illustrate the advantages of the above-described embodiments,  FIGS. 4-7  depict modified configurations in which the laser scanner and or image sensor is positioned in different locations. In  FIGS. 4A ,  4 B, the scanner is centered on the last axis, displacing the contact sensitive member, and is further forward. Accordingly, d 1 ′ has been reduced to zero, but d 1  has increased, essentially transferring error from the non-contact measuring device to the contact measuring device. Additionally, in this embodiment, both the measuring devices  55 ,  60  are further from the second and third to last axes L 2 , L 3 , increasing d 2 , d 2 ′, d 3 , and d 3 ′. Even further, as the center of gravity CG is displaced forward, away from the handle&#39;s axis L 5 , the coordinate acquisition member can be more difficult to maneuver as d 5  is larger, and can further suffer greater deflection. 
     In  FIGS. 5A ,  5 B, the scanner is above the last axis. Accordingly, there is a large distance between the last axis and the laser area (d 1 ′) as well as a larger maximum length d 4  of the coordinate acquisition member  50 . Further, displacing the center of gravity CG from the last axis L 1  can hinder the maneuverability of the coordinate acquisition member  50 . Additionally, the scanner is slightly more forward, increasing the distance from the focus P 1  to the second and third to last axes (d 3 ′). 
     In  FIGS. 6A ,  6 B, the scanner is further forward and below the last axis. Accordingly, there is a large distance between the last axis and the laser area (d 1 ′) and a similarly large distance between the second and third to last axes and the scanner&#39;s focus P 1  (d 3 ′). Further, the center of gravity CG is displaced from the last axis L 1  and the handle (d 5 ), hindering the maneuverability of the coordinate acquisition member  50 . 
     In  FIG. 7A ,  7 B,  7 C, with the scanner off to the side of the last axis, there is a large distance between the last axis and the laser area (d 1 ′), and a large distance between the second and third to last axes and the scanner&#39;s focus P 1  (d 3 ′). Further, displacing the center of gravity CG from the last axis L 1  and the handle&#39;s axis L 5  can hinder the maneuverability of the coordinate acquisition member  50 . 
     The various devices, methods, procedures, and techniques described above provide a number of ways to carry out the invention. Of course, it is to be understood that not necessarily all objectives or advantages described may be achieved in accordance with any particular embodiment described herein. Also, although the invention has been disclosed in the context of certain embodiments and examples, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses and obvious modifications and equivalents thereof. Accordingly, the invention is not intended to be limited by the specific disclosures of preferred embodiments herein.