Rotary sensor system with a single detector

• US 6,538,750 B1
• Filed: 05/19/1999
• Issued: 03/25/2003
• Est. Priority Date: 05/22/1998
• Status: Expired due to Fees

• Current Assignee: CyberOptics Corporation (Nordson Corporation)
• Original Assignee: CyberOptics Corporation (Nordson Corporation)
• Inventors: Jalkio, Jeffrey A., Cohn, Brian D., Case, Steven K., Fishbaine, David, Konicek, John P., Volkman, Thomas L.
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Nguyen, Sang H.
• Application Number:
  US09/314,169
• Time in Patent Office: 1,406 Days
• Field of Search: 356/237--23, 356/375, 356/394, 356/400, 356/446, 356/614, 356/615, 356/622, 356/629, 356/630, 356/634, 356/635, 356/636, 250/560-561, 250/559.29, 250/559.49, 348/126, 382/8, 382/47, 382/146, 382/149, 382/151
• US Class Current: 356/614
• CPC Class Codes: H05K 13/0812 the monitoring devices being integrated in the mounting machine, e.g. for monitoring components, leads, component placement

Abstract

The system of the present invention reports a signal related to a physical condition of an object, such as an electronic component, with the most basic realization of the system including a vacuum quill for releasably holding the object and a motion control system for rotating the quill. The invention includes control electronics coupled to the detector for providing a trigger signal where the detector is oriented to view a stripe in a viewing plane perpendicular to the central axis of the quill, and to provide an image of the stripe. The control electronics sends a plurality of trigger signals to the detector while the motion control system rotates the quill, with each trigger signal triggering the acquisition of another image of a stripe. A processing circuit processes the plurality of images of the stripes to provide the signal related to the physical condition of the object, which can include the orientation or location of the component, the presence or absence of balls on a ball grid array, the height of a specific lead on a leaded component, the distance between the leads on a leaded component or the coplanarity of features on the component. A method for picking and placing components is also disclosed for use with the apparatus of the present invention.

Claims

1. A system for providing a signal related to a physical condition of an object, the system comprising:

a quill for releasably holding the object;

a motion control system for rotating the quill about a central axis, the central axis having a viewing plane substantially perpendicular thereto;

control electronics for providing a plurality of trigger signals;

a detector adapted to view a stripe in the viewing plane upon receipt of a trigger signal and to provide an image of the stripe, the detector viewing a plurality of stripes while the motion control system rotates the quill; and

processing circuitry for processing the plurality of images of the stripes to provide the signal related to the physical condition of the object.

2. The system of claim 1 further comprising a light source for illuminating at least a portion of the stripe.

3. The system of claim 2 where the light source is adapted to provide front-lit illumination of the stripe.

4. The system of claim 3 where the front-lit illumination is specular.

5. The system of claim 3 where the front-lit illumination is diffuse.

6. The system of claim 3 where the front-lit illumination is diffuse and specular.

7. The system of claim 2 where the light source is adapted to provide back-lit illumination.

8. The system of claim 2 where the light source is adapted to provide back-lit shadow casting illumination.

9. The system of claim 2 where the light source is adapted to provide reflective shadow casting illumination.

10. The system of claim 2 where the light source is a laser.

11. The system of claim 2 where the light source is an LED.

12. The system of claim 2 where a transmit optical path is formed between the light source and the stripe in the plane, and where a mirror is interposed in the transmit optical path.

13. The system of claim 1 farther comprising:

a head mechanically coupled to the quill;

a motor drive unit for translatably moving the head, where the head and the quill move to transport the object.

14. The system of claim 13 where the head moves in the x direction.

15. The system of claim 13 where the head moves in the y direction.

16. The system of claim 13 where the detector is mechanically coupled to the head so that the detector moves with the head.

17. The system of claim 13 where the detector is at a fixed location and the head moves the object to the fixed location.

18. The system of claim 1 where the motion control system rotates the quill at a substantially constant angular velocity.

19. The system of claim 1 where the motion control system rotates the quill at a variable angular velocity.

20. The system of claim 1 where the motion control system includes a rotary encoder with a rotary encoder output representative of an angular position of the quill, and where the control circuitry receives the rotary encoder output.

21. The system of claim 20 where the control electronics issues the trigger signals as a function of the rotary encoder output.

22. The system of claim 1 where the processing circuitry further comprises a storage buffer for holding a Cartesian image array, the array comprising a plurality of locations, the processing circuitry receiving a gray value representative of an area on the plane and computing an (x,y) location corresponding to the area, the (x,y) location corresponding to a target element of the Cartesian image array, the processing circuitry storing the gray value in the target element.

23. The system of claim 1 where the processing circuitry assembles the plurality of the images of the stripes into a polar array, each image of the stripe uniquely associated with a rotational position of the object, and further that each image of the stripe comprises elements therein, each element represented numerically as a gray value in the polar array and each element representative of brightness of an area on the plane.

24. The system of claim 23 where the processing circuitry includes an image processor for mapping the polar array into a Cartesian image array, the Cartesian image array having a plurality of elements therein.

25. The system of claim 24 where the polar array has a plurality of elements therein, and the image processor interpolates among the elements of the polar array to compute the elements of the Cartesian image array.

26. The system of claim 24 where the image processor comprises:

A selector for selecting an (x,y) point corresponding to a target element in the Cartesian image array, the target element representative of an area on the object;

A computer for computing a (r,θ

) point from the (x,y) point;

An algorithm for finding a desired element in the polar array which includes the (r,θ

) point, the algorithm extracting the gray value from the desired element and placing that gray value in the target element of the Cartesian image array.

27. The system of claim 26 where the algorithm is a nearest neighbor algorithm.

28. The system of claim 26 where the algorithm is a linear interpolation algorithm.

29. The system of claim 24 where the Cartesian image array comprises sections which are representative of areas of interest on the component, and the image processor extracts the sections.

30. The system of claim 29 where the image processor formats the sections in an EIA format adapted for communicating to the host processor.

31. The system of claim 1 where the detector is a CCD sensor.

32. The system of claim 1 where the detector is a linear array.

33. The system of claim 32 where the linear array has substantially 1024 pixels.

34. The system of claim 32 where the linear array has substantially 2048 pixels.

35. The system of claim 1 where the object has a top and the viewing plane is substantially coincident with the top.

36. The system of claim 1 where the object has a top and the viewing plane is substantially parallel to the top.

37. The system of claim 1 where the object has a bottom and the viewing plane is substantially coincident with the bottom.

38. The system of claim 1 where the object has a bottom and the viewing plane is substantially parallel to the bottom.

39. The system of claim 1 where the object is an electronic component.

40. The system of claim 39 where the component has a bottom, and where the bottom of the component has raised features thereon, the features selected from the group of features called balls, columns, pins and leads, where the viewing plane is formed from a plurality of the features.

41. The system of claim 40 where the feature is a lead and where the processing circuitry receives a plurality of gray values representative of areas on the plane and identifies at least two areas which correspond to a first lead tip area and a second lead tip area, the processing circuitry computing an orientation of the component from the two lead tip areas, the signal representative of the orientation of the component.

42. The system of claim 41 where the lead tip corresponding to the first lead tip area is located substantially diagonally opposite to the lead tip corresponding to the second lead tip area.

43. The system of claim 40 where the feature is a lead and where the processing circuitry receives a plurality of gray values representative of areas on the plane and identifies at least two areas which correspond to areas on two successive lead tips, the processing circuitry computing a distance between the areas on the lead tips.

44. The system of claim 43 further comprising a host processor coupled to the processing circuitry, the host processor communicating design information related to the component, where the design information is representative of an acceptable spacing between leads and further, where the processing circuits compares the distance to the acceptable spacing and provides the signal, the signal representative of lead tweeze.

45. The system of claim 40 where the processing circuitry receives a plurality of gray values representative of areas on the viewing plane, the circuitry identifying a first gray value which corresponds to an area on a first feature and a second gray value corresponding to an area on a second feature, the processing circuitry computing an orientation of the component from the two areas, the signal representative of the orientation of the component.

46. The system of claim 45 where the area on the first feature is located on the component substantially opposite to the area on the second feature.

47. The system of claim 40 further comprising a host processor coupled to the processing circuitry, the host processor communicating design information related to the component, where the design information is representative of the expected locations of the features and further, where the processing circuitry receives a plurality of gray values representative of areas on the plane proximate to the expected location of the feature and determines whether a feature is present in the component, the signal representative of the presence of the feature.

48. The system of claim 39 where the component has an outline defining a space below and above the component, and where the detector is located outside the space.

49. The system of claim 48 where the detector is located inside a housing.

50. The system of claim 48 further comprising a lens system for forming an optical image of the stripe onto the detector, where the lens system is located outside the space.

51. The system of claim 39 where the component additionally has four edges and four comers and the detector has a principal axis, where the principal axis of the detector is positioned perpendicularly to one of the edges, so that when the component rotates, the stripes largely represent the comers of the component.

52. The system of claim 39 where the component has a center which is substantially coincident with the central axis.

53. The system of claim 39 where the component has a center which is not coincident with the central axis.

54. The system of claim 53 where the quill contacts the component in an area which does not include the central axis.

55. The system of claim 54 where the component has a rectangular outline, where the central axis lies within the rectangular outline.

56. The system of claim 54 where the component has a rectangular outline, where the central axis lies outside of the rectangular outline.

57. The system of claim 54 where the quill is adapted to releasably hold at least one additional component.

58. The system of claim 54 further comprising at least one additional quill for releasably holding an additional component.

59. The system of claim 54 where the quill has a first segment connected to a second segment by an arm, the second segment releasably holding the component and rotating the component about an additional axis, the first segment rotating the arm, the second segment and the component about the central axis, the additional axis substantially parallel to the central axis.

60. The system of claim 59 where the first segment rotates the arm, the second segment and the component about the central axis at a first angular velocity and the second segment rotates the component about the additional axis at a second angular velocity, the first angular velocity and the second angular velocity substantially equal in magnitude and in opposite direction.

61. The system of claim 1 where the object has a center and a perimeter, and where the detector is positioned so that the plurality of stripes represent areas emanating substantially radially from the center and including the perimeter of the object.

62. The system of claim 61 where the motion control system rotates the object substantially through 360 degrees to provide the signal related to the physical condition of the object.

63. The system of claim 1 where the object has a center and a pair of edges, one edge substantially opposite the other, and where the detector is positioned so that the plurality of stripes represent an area including the two edges and the center.

64. The system of claim 63 where the motion control system rotates the object substantially through 180 degrees to provide the signal related to the physical condition of the object.

65. The system of claim 1 where a transmit optical path is formed between the detector and the stripe in the viewing plane, and where a mirror is interposed in the transmit optical path.

66. The system of claim 65 where the mirror is translatably positioned with respect to the stripe in the viewing plane.

67. The system of claim 65 where the mirror is fixedly positioned with respect to the stripe in the viewing plane.

68. The system of claim 65 where the mirror is a beam splitter.

69. The system of claim 65 where the mirror partially reflects the light which impinges thereon.

70. The system of claim 1 further comprising a lens system for forming an optical image of the stripe on the detector.

71. The system of claim 70 where the lens system includes an array of GRIN rod lenses.

72. The system of claim 1 where an observation plane is formed between the detector and the stripe in the viewing plane, the observation plane intersecting the central axis in a point.

73. The system of claim 72 where the system further comprises a light source for illuminating at least a portion of the stripe in the viewing plane.

74. The system of claim 73 where the light source is adapted to provide front-lit illumination of the stripe in the viewing plane.

75. The system of claim 74 where the front-lit illumination is specular.

76. The system of claim 74 where the front-lit illumination is diffuse.

77. The system of claim 74 where the front-lit illumination is diffuse and specular.

78. The system of claim 73 where the light source is adapted to provide back-lit illumination of the stripe in the viewing plane.

79. The system of claim 73 where the light source is adapted to provide back-lit shadow casting of the stripe in the viewing plane.

80. The system of claim 73 where the light source is adapted to provide reflective shadow casting illumination of the stripe in the viewing plane.

81. The system of claim 73 where a receive optical path is formed between the light source and the stripe in the viewing plane, and where a mirror is interposed in the receive optical path.

82. The system of claim 73 where a transmit optical path is formed between the detector and the stripe in the viewing plane, and where a mirror is interposed in the transmit optical path.

83. The system of claim 82 where the signal is representative of the coplanarity of the features.

84. The system of claim 72 where the object has a center and a pair of edges, one edge substantially opposite the other, where one of the plurality of stripe images represent an area including the edges and the center, where the motion control system rotates the object over at least 360 degrees so as to provide a set of data points, the set including two data points representative of a single feature on the object, the processing circuitry operating on the set to provide a height of the feature relative to the plane.

85. The system of claim 84 where the feature is selected from the group of features known as balls, pins, columns and leads.

86. The system of claim 72 where the object is a component which has a center and a pair of edges, one edge substantially opposite the other, where one of the plurality of stripe images represents an area including the edges and the center, where the motion control system rotates the object over at least 360 degrees so as to provide a set of data points, the set including two data points representative of each feature in a set of selected features on the object, the processing circuitry operating on the set to compute heights of the selected set of features and providing the signal representative of a coplanarity of the set of selected features.

87. The system of claim 86 where the feature is selected from the group of features known as balls, columns, pins and leads.

88. The system of claim 87 where the signal is representative of the coplanarity of the features.

89. The system of claim 1 where the central axis is substantially coincident with an observation plane formed between the detector and the stripe in the viewing plane.

90. The system of claim 89 where the system further comprises a light source for illuminating at least a portion of the stripe in the viewing plane.

91. The system of claim 90 where the light source is adapted to provide front-lit illumination of the stripe in the viewing plane.

92. The system of claim 91 where the front-lit illumination is specular.

93. The system of claim 91 where the front-lit illumination is diffuse.

94. The system of claim 91 where the front-lit illumination is diffuse and specular.

95. The system of claim 90 where the light source is adapted to provide back-lit illumination of the stripe in the viewing plane.

96. The system of claim 90 where the light source is adapted to provide back-lit shadow casting of the stripe.

97. The system of claim 90 where the light source is adapted to provide reflective shadow casting illumination of the stripe in the viewing plane.

98. The system of claim 90 where a receive optical path is formed between the light source and the stripe in the viewing plane, and where a mirror is interposed in the receive optical path.

99. The system of claim 90 where a transmit optical path is formed between the detector and the stripe in the viewing plane, and where a mirror is interposed in the transmit optical path.

100. The system of claim 89 where the object has a center and a pair of edges, one edge substantially opposite the other, where one of the plurality of stripe images represent an area including the edges and the center, where the motion control system rotates the object over at least 360 degrees so as to provide a set of data points, the set including two data points representative of a single feature on the object, the processing circuitry operating on the set to provide a height of the feature relative to the plane.

101. The system of claim 100 where the feature is selected from the group of features known as balls, column, pins and leads.

102. The system of claim 101 where the signal is representative of the coplanarity of the features.

103. The system of claim 89 where the object is a component which has a center and a pair of edges, one edge substantially opposite the other, where one of the plurality of stripe images represents an area including the edges and the center, where the motion control system rotates the object over at least 360 degrees so as to provide a set of data points, the set including two data points representative of each feature in a set of selected features on the object, the processing circuitry operating on the set to compute heights of the selected set of features and providing the signal representative of a coplanarity of the set of selected features.

104. The system of claim 103 where the feature is selected from the group of features known as balls, columns and leads.

105. The system of claim 104 where the signal is representative of the coplanarity of the features.

106. A method for picking and placing a component, comprising the steps of:

1. Releasably picking up the component with a quill, the quill having a central axis substantially perpendicular to a viewing plane;

2. Positioning the component relative to a detector, the detector adapted to view a stripe in the viewing plane and including electronics adapted to provide a signal representative of a physical condition of the component; and

3. Rotating the component while acquiring a plurality of views of the stripes.

107. The method of claim 106 farther comprising the steps of:

1. Moving the component to a placement area; and

2. Placing the component as a function of the signal.

108. The method of claim 107 where a head is mechanically coupled to the quill and the detector travels with the head.

109. The method of claim 107 where the component has an outline, the outline forming a space above and below the component, where the method further comprises moving the detector at least partially within the space before step 3 and moving the detector outside the space after step 3.

110. The method of claim 107 where the component has an outline, the outline forming a space above and below the component where the method further comprises moving a mirror to a location at least partially within the space before step 3, and moving the mirror outside the space after step 3.

111. The method of claim 110 where mirror is rotatably moved.

112. The method of claim 110 where mirror is slidably moved.

113. The method of claim 107 where a head is mechanically coupled to the quill and the detector is at a fixed location, where the head moves with the object to the fixed location.

114. The method of claim 106 further comprising the steps of starting to move the component to a placement area before after step 1 has started, and placing the component as a function of the signal.

115. The method of claim 106 further comprising the steps of starting to move the component to a placement area after step 2 has started, and placing the component as a function of the signal.

116. The method of claim 106 further comprising the steps of starting to move the component to a placement area after step 3 has started, and placing the component as a function of the signal.

117. The method of claim 106 where the quill has a first segment rotating about a central axis connected to a second segment by an arm, the second segment releasably holding the component and rotating the component about an additional axis, the first segment rotating the arm, the second segment and the component about the central axis, the additional axis substantially parallel to the central axis, where the motion of step 2 includes a rotation about the central axis and where the rotation of step 3 includes a rotation about the additional axis.

118. A method of picking and placing a component, the method comprising the steps of:

1) releasably picking up the component with a quill, the quill having a central axis substantially perpendicular to a viewing plane;

2) elevating the quill to a measurement elevation relative to a detector;

3) rotating the quill so as to position the component relative to the detector, so that when the component rotates the detector views a stripe in the viewing plane, the detector including electronics adapted to provide a signal representative of a physical condition of the component, the electronics acquiring a plurality of views of the stripes;

4) rotating the quill so as to rotate the component away from the detector; and

5) lowering the quill so as to allow for placement of the component.