Abstract:
Apparatus for placement of an optical component on a substrate. The apparatus includes a machine vision system for locating the optical component on the substrate, a contact determiner for determining contact therebetween, and a robot for contacting the optical component and the substrate with one another, and for moving the optical component and the substrate relative to one another under guidance from the machine vision system toward a desired position, wherein the optical component and the substrate contact one another for a portion of the movement. A method includes contacting the optical component with the substrate, locating the optical component on the substrate, and moving the optical component and the substrate relative to one another toward a desired position of the optical component on the substrate, wherein the optical component and the substrate contact one another for a portion of the moving.

Description:
FIELD OF THE INVENTION 
     This invention relates to optical component placement methods and apparatus in general, and more particularly to precision opto-mechanical assembly of fiberoptic telecommunication components. 
     BACKGROUND OF THE INVENTION 
     Development of high productivity methods for manufacturing precision opto-mechanical assemblies is important to ensure large volume production of fiberoptic telecommunication assemblies. Such methods generally avoid active alignment of components using measured device optical performance but rather maintain high mechanical tolerances during assembly so as to achieve the required optical performance. Vision systems are widely used in the precision assembly of mechanical components. In order to achieve high accuracy placement with the assistance of machine vision, an assembly robot needs to have high resolution, a repeatable motion control system and a stiff mechanical structure. The main advantage of utilizing the machine vision system is in reduced requirements for motion control, mechanical structure accuracy, and parts handling accuracy by the assembly robot&#39;s arm tool. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a method for precision placement of an optical component on a substrate with relaxed requirements pertaining to a robot&#39;s motion control system and mechanical structure. 
     Another object of the invention is to provide an apparatus for precision placement of an optical component on a substrate with relaxed requirements pertaining to a robot&#39;s motion control system and mechanical structure. 
     With the above and other objects in view, as will hereinafter appear, there is provided an apparatus for precision placement of an optical component on a substrate and precision assembly thereof into a fiber optic telecommunication package, the apparatus comprising: a machine vision system for locating the optical component relative to a fiducial point on the substrate; contact determiner means for determining contact of the optical component and the substrate with one another; and a robot being configured for contacting the optical component and the substrate with one another under guidance from the contact determiner means, and the robot being further configured for moving the optical component and the substrate relative to one another under guidance from the machine vision system toward a desired position of the optical component relative to the fiducial point on the substrate; wherein said optical component and the substrate contact one another for at least a portion of the movement of the optical component and the substrate toward the desired position of the optical component relative to the fiducial point on the substrate. 
     In accordance with a further feature of the invention there is provided a method for precision placement of an optical component on a substrate and precision assembly thereof into a telecommunication package, the method comprising: contacting the optical component and the substrate with one another; locating the optical component relative to a fiducial point on the substrate; and moving the optical component and the substrate relative to one another toward a desired position of the optical component relative to the fiducial point on the substrate; wherein the optical component and the substrate contact one another for at least a portion of the step of moving the optical component and the substrate relative to one another toward the desired position of the optical component relative to the fiducial point on the substrate. 
     The above and other features of the invention, including various novel details of construction and combinations of parts and method steps will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular devices and method steps embodying the invention are shown by way of illustration only and not as limitations of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which are to be considered together with the accompanying drawing wherein: 
     FIG. 1 is a schematic view of one form of an apparatus for precision placement of an optical component on a substrate, illustrative of an embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In a preferred embodiment of the present invention, novel methods and apparatus are provided for precision opto-mechanical assembly of fiberoptic telecommunication components. These novel methods and apparatus directly dampen vibrations rather than require the use of expensive robot motion control systems with sophisticated dampening systems. Accordingly, a preferred embodiment of the present invention, which uses direct vibration techniques, allows the use of less precise robot motion control systems. This configuration, in turn, translates into significant cost savings for the manufacturing process. 
     Referring to FIG. 1, in a preferred embodiment of the present invention, there is shown an apparatus  5  for precision placement of an optical component  10  on a substrate  15 . Apparatus  5  comprises a machine vision system  20 , a robotic assembly system  25 , and a contact determining system (not shown). Robotic assembly system  25  generally comprises a multi-axis motion stage (not shown) and an arm  30 . Arm  30  is shown having an end portion  35  configured for selective attachment and movement of optical component  10 . In an alternative embodiment of the present invention (not shown), substrate  15  is placed on a stationary surface rather than a multi-axis motion stage. 
     Still referring to FIG. 1, in a preferred embodiment of the invention, arm  30  of robotic assembly system  25  is configured to determine contact between optical component  10  and substrate  15 . A sensor device (not shown) is contained in robotic assembly system  25  to detect contact between optical component  10  and substrate  15  as end portion  35  holding optical component  10  is positioned toward substrate  15 . This sensor device can be programmed to detect contact at a single interval during the positioning of arm  30 . Alternatively, the sensor device can be programmed to continuously monitor whether optical component  10  and substrate  15  are in contact with one another. The sensor device is configured to provide a feedback signal to robotic assembly system  25 . This feedback signal in effect provides guidance to the positioning of end portion  35  so as to maintain contact between optical component  10  and substrate  15  during at least a portion of the positioning as guided by machine vision system  20 . 
     In another preferred embodiment of the present invention (not shown), an auxiliary machine vision system is provided to determine contact between optical component  10  and substrate  15  instead of a sensor device as described above. The auxiliary machine vision system is configured to monitor the position of optical component  10  and substrate  15  relative to one another and to provide a feedback signal to robotic assembly system  25  based on this position. This feedback signal in effect provides guidance to the positioning of end portion  35  so as to maintain contact between optical component  10  and substrate  15  during at least a portion of the positioning as guided by machine vision system  20 . 
     In another preferred embodiment of the present invention (not shown), robotic assembly system  25  is pre-programmed to position optical component  10  and substrate  15  in contact with one another. In this preferred embodiment of the present invention, robotic assembly system  25  does not require either a sensor device or an auxiliary machine vision system as it is pre-programmed to position optical component  10  and substrate  15  in contact with one another. The geometry of optical component  10 , substrate  15  and robotic assembly system  25  relative to one another is predetermined and loaded into the robotic assembly system  25  for computation of appropriate positioning of arm  30  so as to place optical component  10  and substrate  15  in contact with one another. Based on this geometry and pre-programmed locations, robotic assembly system  25  is configured to control arm  30  so as to maintain contact between optical component  10  and substrate  15  during at least a portion of the positioning as guided by machine vision system  20 . 
     In alternative preferred embodiments of the present invention (not shown), optical component  10  and substrate  15  may each be positioned relative to one another by adjustable portions of robotic assembly system  25  in connection to each one. Alternatively, substrate  15  may be positioned relative to a positionally fixed optical component  10  by an adjustable portion of robotic assembly system  25  in connection to substrate  15 . In any of these configurations, examples of adjustable portions of robotic assembly system  25  include, for illustrative purposes only, an arm or multi-axis motion stage. These examples are not intended to limit the scope of the invention. 
     Referring again to FIG. 1, in a preferred embodiment of the present invention, machine vision system  20  is shown configured to view the location of optical component  10  and substrate  15  relative to the upper surfaces of one another. The upper surface of substrate  15  is provided with a fiducial point (not shown) for recognition by machine vision system  20 . The placement position of optical component  10  on substrate  15  is predetermined relative to the location of the fiducial point (not shown). Machine vision system  20  is configured to locate both the fiducial point (not shown) on substrate  15  and the position of optical component  10  on substrate  15 . Next, a signal is generated corresponding to the correction movement necessary to reposition optical component  10  and substrate  15  relative to one another so as to position optical component  10  at the predetermined placement position relative to the fiducial point (not shown). This signal is sent to robot assembly system  25  to move optical component  10  and/or substrate  15  into the pre-determined placement position as described herein. 
     In a preferred embodiment of the present invention, a method is provided for precision placement and attachment of optical component  10  on substrate  15 . First, substrate  15  is positioned on a support in a fixed position to robotic assembly system  25  and optical componenet is positioned on end portion  35  of arm  30  of robotic assembly system  25 . Next, arm  30  of robotic assembly system  25  is moved toward substrate  15  until the contact determining system detects contact between optical component  10  and substrate  15 . A predetermined force is then applied by robotic assembly system  25  so as to create friction between optical component  10  and substrate  15 . 
     Machine vision system  20  then takes an image of optical component  10  on substrate  15 , locates identifying features on substrate  15 , and defines a correction signal. The correction signal is sent to robotic assembly system  25  for generating a correction movement so as to re-position optical component  10  at a pre-determined location relative to the identifying features on substrate  15 . As optical component  10  is resting on substrate  15  at the time that machine vision system takes the image, external factors such as instability and vibration of machine vision system  20  do not have as great an affect on the position of optical component  10  as these external factors would on an optical component held in the air above a substrate. This configuration results in greater position stability of optical component  10  and allows a more precise machine vision measurement of the relative position of optical component  10  with respect to the locating features on substrate  15 . 
     Robotic assembly system  25  generates and performs a correction movement of optical component  10  and substrate  15  relative to one another based on the correction signal received from machine vision system  20 . Optical component  10  and substrate  15  contact one another during the correction movement. In a preferred embodiment of the present invention, optical component  10  slides on substrate  15  during the corrective movement. This contact introduces mechanical dampering into the system and constrains the motion to one plane, thereby achieving more precise motion. 
     After the correction movement is executed, machine vision system  20  takes another image of optical component  10  relative to substrate  15  and another correcton signal is generated. Robotic assembly system  25  then generates and performs another correction movement of optical component  10  and substrate  15  relative to one another. This process can be repeated several times until the position of optical component  10  conforms to a location within specified tolerances with respect to fiducials located on substrate  15 . 
     Modifications to the Preferred Embodiment 
     The robotic assembly system  25  may not need the touch sensing capability. It may be sufficient for robotic assembly  25  to go to the programmed position in the proximity of substrate  15  to ensure the contact between optical component  10  and the substrate. Or another vision system can be used to detect the contact between the part and the substrate. 
     When the corrective motion is performed, it may be necessary to pick up optical component  10  from substrate  15  and put it back to complete the motion. 
     BENEFITS OF THE INVENTION 
     The method and apparatus of the present invention allows achievement of higher tolerances than a conventional machine vision guided parts assembly. As the bottom of optical component  10  and fiducials are located in the same plane, the plane of the surface of substrate  15 , this configuration allows capture of the sharpest image. 
     Influences of undesirable motion is greatly reduced due to the introduction of mechanical friction between optical component  10  and substrate  15 . For example, these influences may include servoing of robotic assembly system  25  associated with positioning and amplification of external vibration due to mechanical structure with a lack of stiffness. Friction provided by optical component  10  sliding on the substrate surface dampens undesirable motion in a wider frequency range than a servo system. All of the above-identified benefits together result in improved accuracy of the assembly. 
     In addition, the requirements concerning the mechanical construction of the equipment and the accuracy of the motion control system are relaxed so as to also reduce the cost of the equipment.