Abstract:
The invention provides for an imaging apparatus for imaging integrated circuits and a respective integrated circuit carrier. This enables positional analysis to be carried out on the integrated circuits and respective carrier. The imaging apparatus includes a support structure, and a bed mounted on the support structure and displaceable along an operatively horizontal axis, the bed being configured to support a nest assembly that operatively retains the integrated circuit carrier and respective integrated circuits. Also included is a support assembly operatively mountable with respect to a bed on which the integrated circuit carrier and integrated circuits are supported, in use. The apparatus further includes an image recordal device mounted on the support assembly and configured to record an image representing the integrated circuit carrier and integrated circuits, the support assembly including an adjustment mechanism to enable adjustment of a position of the image recordal device relative to the bed.

Description:
FIELD OF INVENTION 
     The invention relates to the field of printing, in general. More specifically, the invention relates to testing of alignment printhead integrated circuits positioned on a carrier. 
     CO-PENDING APPLICATIONS 
     The following applications have been filed by the Applicant simultaneously with the present application: 
     
       
         
               
               
               
               
               
               
               
             
           
               
                   
               
             
             
               
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     The disclosures of these co-pending applications are incorporated herein by reference. The above applications have been identified by their filing docket number, which will be substituted with the corresponding application number, once assigned. 
     CROSS REFERENCES 
     The following patents or patent applications filed by the applicant or assignee of the present invention are hereby incorporated by cross-reference. 
     
       
         
               
               
               
               
               
               
               
             
           
               
                   
               
             
             
               
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     BACKGROUND 
     Pagewidth printers that incorporate micro-electromechanical components generally have printhead integrated circuits that include a silicon substrate with a large number of densely arranged, micro-electromechanical nozzle arrangements. Each nozzle arrangement is responsible for ejecting a stream of ink drops. 
     In order for such printers to print accurately and maintain quality, it is important that the printhead integrated circuits be tested. This is particularly important during the design and development of such integrated circuits. 
     Some form of platform or carrier is generally required for testing such integrated circuits. The carrier is required to be suitable for the attachment of printhead integrated circuits. In addition, in order for an array of printhead integrated circuits on the carrier to operate properly, relative orientation of the printhead integrated circuits should be monitored. 
     SUMMARY 
     According to a first aspect of the invention there is provided a measuring apparatus for measuring the positions of a plurality of printhead integrated circuits relative to a carrier on which the printhead integrated circuits are located, the carrier having carrier fiducials and each integrated circuit having integrated circuit fiducials, said measuring apparatus comprising:
         a support assembly;   a receptacle positioned on the support assembly and configured to receive the carrier, the receptacle being movable relative to the support assembly between a loading position and a sensing position;   a sensor configured to sense positions of the carrier and integrated circuit fiducials; and   a control system configured to control the sensor to measure the positions of the carrier and integrated circuit fiducials.       

     Preferably, the support assembly includes a displacement mechanism to displace the receptacle between the loading and sensing positions. 
     Preferably, the receptacle includes a clamp arrangement for clamping the carrier to the receptacle. 
     Preferably, the sensor includes a digital camera arrangement configured to sense the fiducials and to communicate image data representing the fiducials to the control system. 
     Preferably, the control system includes a graphical display for displaying the image data. 
     Preferably, the control system is configured further to process the image data to measure positions of the carrier fiducials and the integrated circuit fiducials and to generate positional data for analysis. 
     Preferably, the control system includes a reader configured to read a code on the carrier. 
     Preferably, the reader includes a barcode scanner for reading a barcode on the carrier. 
     According to a second aspect of the invention there is provided a method for testing an alignment of a carrier with respect to a plurality of integrated circuits on the carrier, the carrier having optically discernible carrier references and each integrated circuit having optically discernible circuit references, said method comprising the steps of:
         receiving the carrier in a holding assembly;   sensing positions of the carrier and circuit references; and   measuring the positions of the carrier and circuit references.       

     Preferably, the step of receiving the carrier in the holding assembly includes the step of clamping the carrier between clamps of the holding assembly. 
     Preferably, the step of sensing includes the step of sensing two of the carrier references and two of the circuit references on each integrated circuit. 
     Preferably, the step of sensing includes sensing with a digital camera arrangement and generating image data. 
     Preferably, the step of measuring includes the step of generating and displaying an image from the image data. 
     Preferably, the step of measuring includes the step of generating co-ordinate values corresponding to positions of the carrier references and the circuit references. 
     Preferably, the step of measuring includes the step of measuring an alignment of consecutive integrated circuits using the co-ordinate values. 
     According to a third aspect of the invention there is provided a safety system for a measuring apparatus for measuring positions of integrated circuits on an integrated circuit carrier positioned, in use, in a working enclosure of the machine, said safety system comprising:
         a sensor arrangement for sensing an operational status of the measuring apparatus;   an emergency cut-off configured to deactivate the measuring apparatus automatically when an undesired operational status is sensed by the sensor arrangement; and   a control system connected to the sensor arrangement and the emergency cut-off to activate the emergency cut-off on receipt of a predetermined signal from the sensor arrangement.       

     Preferably, the operational status is an aspect selected from: a position of at least one measuring device of the measuring apparatus; a presence of a foreign object in the working enclosure; a fluid pressure of a pneumatic or hydraulic mechanism of the measuring apparatus; a position of the integrated circuit carrier; authenticity of the carrier; an electricity supply to the measuring apparatus; and an operator identifier of an operator operating the measuring apparatus. 
     Preferably, the sensor arrangement has a plurality of micro-switches for sensing the position of the at least one movable mechanism. 
     Preferably, the sensor arrangement includes a light curtain to sense the ingress of a foreign object into the enclosure. 
     Preferably, the sensor arrangement includes a pressure sensor to sense the fluid pressure of a hydraulic or pneumatic movable mechanism. 
     The sensor arrangement may include proximity switches to determine the position of the integrated circuit carrier. 
     The sensor arrangement may include a barcode scanner to scan a barcode of the integrated circuit carrier. 
     The sensor arrangement may include a residual current circuit breaker to detect residual current and provide overcurrent protection. 
     According to a fourth aspect of the invention there is provided a measuring apparatus comprising:
         a housing assembly that defines an enclosure;   a control system mounted in the housing assembly;   an operator interface mounted on the housing assembly and connected to the control system to allow an operator to control the measuring apparatus;   a measuring table assembly mounted in the housing assembly and configured to receive a nest assembly supporting an integrated circuit carrier carrying a number of integrated circuits; and       

     a camera assembly mounted in the housing assembly and configured to generate image data representing the integrated circuit carrier and the integrated circuits, the camera assembly being connected to the control system which is configured to carry out a positional analysis on the integrated circuit carrier and the integrated circuits to determine at least one of positions of the integrated circuits on the carrier and relative positions of consecutive integrated circuits. 
     The housing assembly may include a closure which can be opened or closed to allow or prevent access to the enclosure. The closure may include a safety switch and the control system may include a controller connected to the safety switch to stop operation of the measuring apparatus if the closure is opened during operation. 
     The measuring table assembly may include a linear stage assembly to displace the nest assembly linearly into an imaging position. 
     The camera assembly may include a camera post that is mounted on the measuring bed assembly to extend operatively above the measuring bed assembly. 
     The camera assembly may include a digital camera mounted on the camera post to be displaceable with respect to the camera post for focusing purposes. The digital camera may be connected to the control system so that the control system can receive the image data generated by the digital camera. 
     The control system may be configured to identify fiducials on the integrated circuit carrier and the integrated circuits and to calculate co-ordinate values with respect to a predetermined reference point corresponding to said fiducials. 
     The control system may be configured to determine positions of the integrated circuits on the integrated circuit carrier and relative positions of the integrated circuits to assess alignment of the integrated circuits. 
     According to a fifth aspect of the invention there is provided an imaging apparatus for imaging integrated circuits and a respective integrated circuit carrier so that positional analysis can be carried out on the integrated circuits and respective carrier, the imaging apparatus comprising
         a support structure;   a bed mounted on the support structure and displaceable along an operatively horizontal axis, the bed being configured to support a nest assembly that operatively retains the integrated circuit carrier and respective integrated circuits;   a support assembly operatively mountable with respect to a bed on which the integrated circuit carrier and integrated circuits are supported, in use; and   an image recordal device mounted on the support assembly and configured to record an image representing the integrated circuit carrier and integrated circuits, the support assembly including an adjustment mechanism to enable adjustment of a position of the image recordal device relative to the bed.       

     The bed may include a linear stage engaged with the support structure to facilitate adjustment of a position of the bed relative to the support structure along the horizontal axis. 
     The bed may include a proximity sensor to generate a suitable signal when the nest assembly is in a predetermined position. 
     The support assembly may include a support post extending operatively vertically with respect to the bed, the adjustment mechanism being in the form of a linear displacement mechanism mounted on the support post to displace the image recordal device with respect to the support post. 
     The image recordal device includes LED assemblies incorporating LED&#39;s and positioned on the support assembly such that the LED&#39;s illuminate the integrated circuit carrier and the integrated circuits. 
     The image recordal device includes a digital camera, the adjustment mechanism being configured to adjust the position of the digital camera to achieve focus of the digital camera. 
     The digital camera is a black and white camera incorporating a CCD array. 
     The image recordal device includes a lighting controller to control operation of the LED&#39;s. 
     According to a sixth aspect of the invention there is provided a software product for execution by a controller of a measuring apparatus, as described above, said software product enabling the apparatus to perform the above method. 
     According to a seventh aspect of the invention there is provided a computer readable medium incorporating a software product, as described above. 
     Embodiments of the invention are now described, by way of example, with reference to the accompanying drawings. The following description is intended to illustrate particular embodiments of the invention and to permit a person skilled in the art to put those embodiments of the invention into effect. Accordingly, the following description is not intended to limit the scope of the preceding paragraphs in any way. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows: 
         FIG. 1  shows a front perspective view of a carrier for printhead integrated circuits; 
         FIG. 2  shows a top view of the carrier of  FIG. 1  showing alignment of fiducials, in accordance with one embodiment of the invention; 
         FIG. 3  shows a schematic front view of a measuring apparatus for measuring alignment of fiducials, in accordance with one embodiment of the invention; 
         FIG. 4  shows a front perspective exploded view of components forming a camera assembly, in accordance with one embodiment of the invention, of the apparatus of  FIG. 3 ; 
         FIG. 5  shows a rear perspective of the camera assembly of  FIG. 4 ; 
         FIG. 6  shows a front perspective view of a support assembly, in accordance with one embodiment of the invention, of the apparatus of  FIG. 3 ; 
         FIG. 7  shows a block diagram for a method of testing alignment of a carrier with respect to a number of integrated circuits, in accordance with one embodiment of the invention; 
         FIG. 8  shows a service panel layout of the apparatus shown in  FIG. 3 ; 
         FIG. 9  shows a pneumatic diagram of pneumatic components of the apparatus shown in  FIG. 3 ; 
         FIG. 10  shows a diagram of a number of mechanical and electrical components of the apparatus of  FIG. 3 ; 
         FIG. 11  shows a control diagram for a stepper motor of a camera assembly of the apparatus of  FIG. 3 ; 
         FIG. 12  shows a control diagram for a servo motor of a measuring table assembly of the apparatus of  FIG. 3 ; and, 
         FIG. 13  shows a control diagram for a safety system of the apparatus of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the invention will now be described with reference to specific embodiments thereof. Reference to “an embodiment” or “one embodiment” is made in an inclusive rather than restrictive sense. As such, reference to particular features found in one embodiment does not exclude those features from other embodiments. 
     The following description is intended to assist a person skilled in the art to understand the invention. Accordingly, features commonplace in the art are not described in particular detail, as such features will be readily understood by the skilled person. 
     With reference to  FIG. 1  of the drawings, a carrier  10  for a number of printhead integrated circuits (ICs)  14  is shown. The carrier  10  is an LCP (liquid crystal polymer) molding which has a co-efficient of thermal expansion very near that of silicon. As the printhead heats to its operational temperature, any difference in the thermal expansion of the printhead ICs and the carrier will be within acceptable tolerances. The printhead ICs  14  include an array of nozzle arrangements configured to eject ink drops onto a printing medium. The nozzle arrangements are MEMS (micro-electromechanical system) devices fabricated using lithographic etching and deposition processes commonly employed in semi-conductor chip production. 
     The carrier  10  defines a number of tortuous ink paths therein (not shown) which terminate in a surface on which the printhead ICs  14  are mounted. The printhead ICs  14  are mounted to the carrier  10  via an adhesive laminar film  12  (often referred to as a die attach film) with suitable perforations or openings positioned to establish fluid communication between each of the ink paths and corresponding nozzles rows on the printhead ICs. The ink paths in the carrier  10  facilitate the delivery of ink from a suitable ink reservoir to the printhead ICs  14 . The printhead ICs  14  must be aligned when mounted to the carrier  10 . Misalignment of the printhead ICs  14  on the carrier  10  can lead to bad print quality or inlets of the printhead ICs  14  being out of register with the openings in the adhesive laminar film  12 . 
       FIG. 2  shows a closer view of the surface of the carrier  10  on which the printhead ICs  14  are mounted. The carrier  10  includes a first carrier fiducial  16  and a second carrier fiducial  18 . The carrier fiducials  16  and  18  are accurately located on the carrier  10  during manufacture thereof. These fiducials serve as points of reference for aligning the printhead ICs  14  on the carrier  10 . 
     The printhead ICs  14  have two fiducials each. The enlarged insets of  FIG. 2  shows printhead IC  14 . 1  has first fiducial  20  located on one end thereof and a second fiducial  22  located on an opposite end. The IC mounted adjacent IC  14 . 1  has similar fiducials located on its ends, such that its first fiducial  24  is closely adjacent the second fiducial  24  on IC  14 . 1 . The IC fiducials e.g.  20 ,  22  are preferably less than 150 μm in diameter and typically less than 100 μm in diameter. The fiducials  20  and  22  are 95 μm dia. bare aluminum etched during manufacture of each printhead IC  14 . In the embodiment shown, there are five printhead ICs  14  mounted on the carrier  10 , the last IC being indicated by reference numeral  14 . 2 . The first and last ICs  14 . 1  and  14 . 2  are mounted so that their respective fiducials lie within a predetermined tolerance to the carrier fiducials  16  and  18  respectively. 
     The intermediate printhead ICs  14  are then laid end-to-end between end printhead ICs  14 . 1  and  14 . 2  so that their respective fiducials align to within a predetermined tolerance with respect to each other. By measuring the positions of the different fiducials with respect to one another, it is possible to measure the alignment of the printhead ICs with each other and with respect to the carrier  10 . 
       FIG. 3  shows an embodiment of a measuring apparatus  30  for measuring the positions of the fiducials  16 ,  18  of the carrier  10  and the fiducials  20  and  22  of the printhead ICs  14  shown in  FIG. 2 . In broad terms, the apparatus  30  is configured to sense the fiducials, compare the distances between the respective fiducials to a predetermined tolerance, and display these results. The apparatus  30  is also typically configured to relay the results to a remote monitoring system that manages a manufacturing process of printing equipment. More detail of the remote monitoring system is discussed below. 
     In the embodiment shown, the apparatus  30  includes a support structure or housing  32  having a services panel  34 . The housing  32  houses a support assembly  44 , a camera assembly  46  and a barcode scanner  42  (also represented in  FIG. 10 ) behind transparent panels  48 . The panels  48  also form a sliding door  49  to allow an operator access to the support assembly  44 . The door  49  includes a magnetic door switch  50  which forms part of a safety system of the apparatus, as described below. Also shown is a warning beacon  38 , which indicates an operational status of the apparatus  30 , a touch panel PC  36  and control panel  40  which allows operator interface with the apparatus  30 . 
     The door  49  also provides a practical safety feature of covering the touch panel PC  36  and control panel  40  when in an open position, as the panel  48  slides over these components to provide access to the components inside the housing  32 . When the panel  48  is open to allow access to the inside of the housing  32 , access to the touch panel PC  36  and control panel  40  is effectively restricted. This prevents accidentally activating the apparatus  30  when the panel  48  of the housing  32  is open, which may injure the operator of the apparatus. 
       FIG. 4  shows the components forming one embodiment of the camera assembly  46  and barcode scanner  42  in more detail. The camera assembly  46  includes a camera mount base  64  with rubber mountings  62  for mounting to the housing  32 . Also included is camera post  74  fitted to the mount base  64 , having an upright pillar  60  and a cover plate  80  with a cover  78  to form a structure for supporting a pedestal  82  to which positioning beam  76  is attached, as shown. 
     The beam  76  serves as support for the barcode scanner  42 , that has a sensor  68  attached to a bracket  66 , as shown. The Hand Held Products Inc. IT3800 model barcode scanning sensor is suitable for this application. The sensor  68  is attached to the bracket  66  with mounting screws  76 , with the bracket  66  in turn fixed to the beam  76  by means of socket screws  70 . 
     Camera and optics, forming an optical assembly  94 , are attached to the supporting pedestal  82  with a camera bracket  98  and a camera mounting base  92  operatively fast with a mounting plate  90 , as shown. Also included is camera lighting module  96 . The Allied Vision AVT F-145B black and white IEEE 1394 SXGA+C-Mount digital camera equipped with a Megapixel Sony ⅔″ type progressive CCD-array is suitable for this application. The lighting module includes LEDs (light emitting diodes) coupled with a Gardasoft PP610 lighting controller  146  (see  FIGS. 8 and 10 ). The camera is assembled with adapters and tubes, as shown, to complete the optical assembly  94 . The optical assembly  94  is arranged in signal communication with a controller of the apparatus to allow the controller to “see” the fiducials. 
     The mounting plate  90  is attached to the pedestal  82  by means of a camera adapter plate  84  operatively fast with a mounting member  88  via socket fasteners  86 , as shown. The mounting plate  90  includes a linear stepper motor  91  to facilitate focusing the camera by moving the camera in a Z-axis direction. Stepper motor  91  is controlled by a stepper motor controller  250  shown in  FIG. 11 . 
     Referring again to  FIG. 11 , the controller  250  communicates with the optical assembly  94  via the contacts  252 . The controller  250  is configured to generate motor drive signals at contacts  254  and to receive positional feedback at contacts  256 . The motor  91  includes an integral Hall effect limit switch  258  for positional adjustment of the motor  91 . 
       FIG. 5  shows a rear perspective view of the camera assembly  46  of  FIG. 4 , with the components assembled. 
       FIG. 6  shows the support assembly or measuring table assembly  44  in more detail. The support assembly  44  includes a displacement mechanism in the form of linear servo motor  110 , and plate adapter  116  for mounting a carrier clamp or carrier receptacle  117  thereto. The receptacle  117  is shaped and dimensioned to receive the carrier  10  shown in  FIG. 2 , in use, and includes two pneumatic clamps  119  to hold the carrier in place. When the operator places the carrier  10  in the receptacle fast with the plate adapter  116 , the controller clamps the carrier fast in the receptacle  117 , when the measuring process is actuated to ensure accuracy of fiducial detection. Operation of the clamps  119  is described with reference to  FIG. 10  below. The servo motor  110  ( FIG. 12 ) is controlled with a servo motor controller  152  that is described in further detail below. 
     As can be seen in  FIG. 10 , the apparatus includes four optocouplers, two indicated at  260  to switch red, amber and green lights  264  on and off and two indicated at  262  to operate the pneumatic clamps  119  with solenoid valves  266  ( FIG. 10 ). LEDs of the optocouplers  260  are connected to the stepper motor controller  250  (see  FIG. 11 ) and to the servo motor controller  152 . The receivers of the optocouplers  260  are, in turn, connected to the red, amber and green lights  264  so that the lights  264  can indicate an operational status of the stepper and servo motors  91 ,  110 . 
     The servo motor controller  152  ( FIG. 12 ) is connected at  276  to a pneumatic clamp arrangement  274  shown in  FIG. 10 . In particular, the controller  152  is connected to a pressure regulator  278  of the clamp arrangement  274 , at  279 . Controlling software defined by the PC associated with the touch panel  36  (see  FIG. 3 ) can also communicate with the pressure regulator  278  via a signal converter  280  and an analogue output module  282 . Thus, operation of the pneumatic clamps  119  (see  FIG. 6 ) is coordinated with operation of the servo motor  110  and the camera assembly  46  (see  FIGS. 4 and 5 ). 
     Also shown in  FIG. 10  is a manual isolation valve  284  having the pneumatic structure indicated with reference numeral  202  in  FIG. 9 , and described in further detail below. 
     The servo motor controller  152  controls the servo motor  110  so that the plate adapter  116  can be moved between a loading position, where an operator is able to load the carrier  10  into the clamp, and a sensing position, where the receptacle with carrier  10  is below the optical assembly  94 . 
     The PBA LMS50 linear stage motor is a suitable servo motor  110 . The receptacle  117  also typically includes a proximity switch  121  (indicated physically in  FIG. 6  and in the control diagram of  FIG. 10 ). The proximity switch  121  is connected to the controller  152  at  286  ( FIG. 11 ) so that the controller  152  can stop the motor  110  once the plate  116  has reached a predetermined extent of movement. 
     The Pepper1 and Fuchs NBB 1,5-F79-E2 inductive proximity switches are suitable for this role. The support assembly  44  also includes cable trays  112  and  114  for housing and locating electrical wires to the linear motor  110  and pneumatic lines to the clamp in a manner which allows unobstructed movement of the plate  116  relative to the motor  110 . 
       FIG. 7  shows a block diagram of method steps performed by an operator and the apparatus  30  to check alignment of the fiducials. It is to be appreciated that reference to a reference numeral representing a particular method step refers to a respective block indicated by such reference numeral in the accompanying drawings. As such, the method included in the invention is not limited or constrained to particular method steps referred to in this manner. A skilled person will understand that further methods are possible under this invention which might exclude some of these steps or include additional steps. 
     The apparatus  30  includes a control system or controller, discussed below, which provides a safety system and control during operation. The control system uses the touch panel PC  36  as an operator interface. Accordingly, some steps of the method are performed by the control system, whilst some steps are performed by an operator, as will be apparent from the below discussion. 
     A remote monitoring system is referred to in the steps of  FIG. 7 . The remote monitoring system is typically a separate computer system arranged in signal communication with the apparatus  30 , and more specifically with a network interface of the apparatus  30 , as described below. The remote monitoring system performs quality assurance tasks by monitoring the progress and status of the carrier  10 . 
     For example, the barcode scanner  42  of the apparatus  30  is configured to scan a barcode of each carrier placed in the clamp  117  of the plate adapter  116 . This barcode uniquely identifies each carrier, with the barcode sent to the remote monitoring system during an assembly and testing process of the carrier  10 . If, during the assembly and testing process, any flaws are detected, the relevant carrier is recorded as flawed by the remote monitoring system. In the event a flawed carrier is not quarantined and proceeds to a next step of the process, the remote monitoring system can prevent a controller or control system of a machine forming part of the process from performing any further work on the carrier. 
     Circuit detail of the barcode scanner  42  is shown in  FIG. 10 . The scanner  42  is switched on by a relay  272 . The relay  272  is connected to the stepper motor controller  250 . Thus, when a PCB (printed circuit board)of the scanner  42  is switched on, the relay  272  serves to actuate the stepper motor controller  250  so that the camera assembly  46  can begin an auto-focusing procedure. 
     This quality assurance functionality of the remote monitoring system prevents unnecessary work done on inferior quality carriers, as well as preventing the assembly of faulty printing components which could lead to malfunctioning final printing products, or the like. 
     Referring now to  FIG. 7 , the method commences with an operator removing a carrier with ICs thereon from a clean storage environment, such as a clean cabinet. This step is indicated by block  170 . The operator then proceeds to scan the barcode of the carrier with the barcode scanner  42 , indicated by block  172 . This action serves to actuate the controller  250  so that the camera assembly  46  can begin the auto-focusing procedure. 
     As shown at block  174 , the control system of the apparatus  30  relays the scanned barcode to the remote monitoring system. If there is a problem with the barcode, the remote monitoring system or the barcode scanner  42  can send a message to the touch panel PC  36  (or user interface—UI) to display a message to the operator, shown by block  176 . The operator can then rescan the barcode, or discard the carrier as faulty. 
     If the remote monitoring system relays a message that the carrier  10  is suitable, the operator proceeds to load the carrier  10  into the clamp or test fixture  117 , as at block  178 . The carrier  10  is then moved into the sensing position by the support assembly  44 , as described above, under operation of the servo motor  110 . The controller or PC  36  controls movement of the support assembly  44  via the controller  250 . The camera assembly  46  achieves the required Z-axis movement for focusing through operation of the servo motor  91  under control of the controller  250 . The camera assembly  46  then enables the determination of the first and second carrier fiducials, shown at blocks  180  and  182 , as well as the first and second IC fiducials of each IC, as shown at blocks  184  and  186 . 
     The camera assembly  46  senses all the fiducials in this manner until the last fiducial has been sensed and its position on the carrier  10  stored by the controller. This process is indicated at block  188 . Once all the fiducials have been sensed, the PC  36  is configured to generate data of the relative positions of the sensed fiducials to each other, as at block  190 . This generated data is then displayed to the operator on the PC touch screen  36  (block  192 ) and uploaded to the remote monitoring system (block  194 ) as results of the sensing step. 
     If the results are unsatisfactory, the remote monitoring system is able to flag that respective carrier  10  as flawed. The method ends with the controller moving the carrier  10  from the sensing position to the loading position where the operator can remove the carrier  10  from the clamp or test fixture  117 . This is indicated at block  196 . 
       FIG. 8  shows the components of the control system concealed by the services panel  34  (see  FIG. 3 ). The connector blocks  126  and the trunking  120  link to the PC touch screen  36  (see  FIG. 3 ) to operate the control system. The Advantech PPC-123T touch screen display PC suitable as the PC touch screen  36 . The trunking  120  is mounted in the support structure for connecting the relevant electrical and pneumatic wires and lines to the different components. The connecting blocks  126  facilitate the electrical connections between the components. The components are attached to mounting rails  128 . 
     Mains isolation switch  122  forms the primary electrical connection of the apparatus to an external power source. The Sprecher &amp; Schuh LE2-12-1782 2 pole switch cam unit is suitable for this application. The main pneumatic connection of the apparatus  30  is via pressure regulator  124 . The Festo MPPES-3-1/4-2-010 series regulator has been found suitable for this task. A circuit breaker  130  (such as a Hager AC810T series circuit breaker) provides electrical protection for the electrical components, along with fuses  132 . 
     Power supply  134  is a Phoenix Contact 12V 3A DC power supply and power supply  136  is a Phoenix contact 24V 2A DC power supply. The power supplies  134  and  136  supply the relevant components with electrical power. Optocouplers  138  (indicated with reference numerals  260 ,  262  in  FIG. 10 ) are used to facilitate operation and interconnection between the clamp arrangement  274 , the lights  264  and the servo motor  110 , as described above. These units  138  are two pairs of NEC PS2502-2 series optocouplers. 
     A safety relay  140  in the form of an Omron G9S-2002 plug-in safety relay is connected to a servo motor controller  152  in order to switch off the servo motor  110 . Safety door controller  142  is linked to magnetic door switches  50  (see  FIG. 3 ) to stop the apparatus if the doors  48  (see  FIG. 3 ) are opened. The controllers and switches from the Omron D40B series are suitable for these purposes. Safety contactors  144  are used to limit the motion of the support assembly  44 . The safety contactors are two Sprecher &amp; Schuh CAS7 series safety contactors. The LED light controller  146  is also mounted on the rail  128 . Control panel  40  (see  FIG. 3 ) also includes an emergency stop switch  290  ( FIG. 13 ) for immediately stopping the apparatus  30 . 
     The solenoid valves  148  and  150 , such as SMC SY3160 series 5-port solenoid valves, control main air isolation and a pneumatic circuit of the clamp or test fixture  117  (see  FIG. 6 ). The servo motor controller  152  such as a linear stage Motion Technologies CEL 6/200 driver is used to control operation of the stepper motor  110  (see  FIG. 6 ). 
     Capacitor  154  is a 35V 2.2 mF unit from Panasonic. Component  156  has an isolated convertor and analog output modules to convert the outputs from the PC touch screen (see  FIG. 3 ) to control signals for the relevant components. An ADAM-4520 converter is suitable for the application. A Z-axis driver  158  in the form of a Zaber NA08A-16 stepper motor with a Copley STP-075-07 series driver, is responsible for camera focus of the camera assembly  46  via motor  91  (see  FIG. 4 ). 
       FIG. 9  shows a pneumatic diagram for pneumatic components of the apparatus  30 . A main air supply  200  provides pressurised air to an isolation valve  202  in the form of an SMC VHS20-01 series manual isolation valve. This is in turn connected to mist separator  204 , which is an SMC AFM20-01-C series unit. Solenoid valve  206  is a SMC SY3160-5MOZ-C6 series valve used to isolate the main system, and pressure regulator  208  regulates pressure to solenoid valves  210  and  212 . 
     Solenoid valves  210  and  212  (indicated as  266  in  FIG. 10 ) are both SMC SY3160-5MOZ-C6 series valves. In the shown configuration, valve  210  is not used, but valve  212  controls the clamp or test fixture  117  (see  FIG. 6 ) for clamping the carrier  10  to the support assembly  44 . The valve  212  actuates two parts of the clamp, namely clamp module  214  and  216 . Clamping module  218  is connected to valve  210  and therefore not operative in this particular embodiment. 
       FIGS. 10 to 13  provide circuit diagrams showing the interconnections of the various electrical components. As will be appreciated by the skilled person, one component typically has a number of discrete wires comprising a single connection to another component. The circuit diagrams inherently show all the wires, but these can be collectively referred to as a single connection in the above description. 
     In  FIG. 10 , there is shown the barcode scanner  42  connected to the barcode scanner relay  272 , in turn, connected to the stepper motor controller  250  ( FIG. 11 ) and the servo motor controller  152 . Thus, operation of the controllers  250 ,  152  can be linked to operation of the scanner  42 . 
     The LEDs  264  and their operative connection to the optocouplers  260  is also shown in  FIG. 10 . Likewise, the solenoid valves  266  and their operative connection to the optocouplers  262  are shown. The optocouplers  260 ,  262  are connected to the controllers  152 ,  250 . 
       FIG. 10  also shows the circuitry of the proximity switch  121 . Circuitry of the lighting controller  146  is also shown. The pneumatic clamp arrangement  274  including the pressure regulator  278 , the analogue output module  282  and the signal converter  280  is shown. 
       FIG. 11  shows the circuitry relating to the stepper motor controller  250 . As can be seen, there is an electrical connection between the linear stepper motor  91  and the Integral Hall limit switch  258 . 
       FIG. 12  shows the circuitry relating to the servo motor controller  152 . The PC  36  is connected to the controller  152  via an RS 232 connection. As shown, the controller  152  is connected to the servo motor  110 . At  288 , the controller  152  is connected to the safety relay  140  ( FIG. 13 ). At  286 , the controller  152  is connected to the proximity switch  121 . At  276 , the controller  152  is connected to the pneumatic clamp arrangement  274 . 
       FIG. 13  shows circuitry of a safety system, in accordance with the invention, of the measuring apparatus  30 . The safety relay  140  is shown connected to the safety door controller  142  and the contacts  144 . Operative connection of the magnetic door switches  50  is also shown. 
     The touch panel PC  36  controls operation of the servo motor controller  152  and thus the servo motor  110  to move the plate adapter  116  with the carrier  10  below the camera assembly  46 . The controller  250  facilitates control of the linear stepper motor  91  to focus the optical assembly  94  on the carrier  10 . The controller  36  can then examine the carrier with the camera assembly  46  to determine the relative positions of the respective fiducials and if they are properly aligned. 
     Similarly, controller  152  receives feedback from sensors such as the proximity switch  121  to determine the position of the carrier  10 , and controls the pneumatic components, described in  FIG. 9 , to clamp the carrier to the plate adapter  116 . 
     It is to be appreciated that the invention also extends to a software product for execution by the controller  36 , as described above. The software product enables the controller  36  to perform the functions and relevant method steps described above. The invention inherently includes a computer readable memory, such as a magnetic or optical disc, incorporating such a software product.