Projection moiré method and apparatus for dynamic measuring of thermal induced warpage

• US 6,564,166 B1
• Filed: 07/07/2000
• Issued: 05/13/2003
• Est. Priority Date: 10/27/1999
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Petriccione, Gregory James, Ume, Ifeanyi Charles
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): Dougherty, Anthony T.
• Application Number:
  US09/611,394
• Time in Patent Office: 1,040 Days
• Field of Search: 702/136, 374/57
• US Class Current: 702/136
• CPC Class Codes: G01B 11/25 by projecting a pattern, e.g. one or more lines, moiré fringes on the object G01B11/255 takes precedence ; image analysis for depth or shape recovery G06T7/50

Abstract

The projection moiré and temperature controlled chamber system houses a workpiece in the chamber and subjects the workpiece to changing temperatures according to a predefined temperature/time profile. As the workpiece is subjected to changing temperatures, a projection moiré system projects a plurality of moiré fringe patterns onto the workpiece, and a camera detects thermally induced warpage in the workpiece. The detection of thermally induced warpage, indicated by changes in the projected fringe moiré patterns on the workpiece, is analyzed by a processing unit. The temperature controlled chamber includes a plurality of heating sources, at least one cooling source, temperature probes and an adjustable support frame. Output temperature of the heating/cooling sources may be variable. The position of the support frame is adjustable and controlled by the processor in a manner such that a reference point associated with the workpiece or the frame is held in a stationery manner. The chamber may also include a plurality of air blowers and exhaust vents to facilitate temperature control within the chamber. An alternative embodiment includes a supplemental shadow moiré system.

Claims

1. A method for measuring thermally induced warpage, the method comprising the steps of:

positioning a workpiece in a chamber;

projecting a plurality of fringe patterns on said workpiece;

regulating temperature in said chamber during simulation of a predefined temperature/time profile;

recording images of said fringe patterns-projected on said workpiece;

analyzing changes in said plurality of fringe patterns; and

maintaining position of a reference point associated with said workpiece at a fixed position in space during simulation of the predefined temperature/time profile.

2. The method of claim 1, wherein said step of regulating temperature further includes changing temperature in said chamber according to a plurality of predefined temperature values corresponding to a plurality of predefined times.

3. The method of claim 1, wherein said step of projecting is effected with a shadow moiré

system.

4. The method of claim 1, wherein said step of regulating temperature further includes the step of heating effected by a plurality of heating sources.

5. The method of claim 1, wherein said step of regulating temperature further includes venting hot gases such that hot gases residing in said chamber are expelled from said chamber.

6. The method of claim 1, wherein said step of regulating temperature further includes the step of blowing gases residing in said chamber effected by at least one blower residing in said chamber.

7. The method of claim 1, wherein said step of projecting is effected with a projection moiré

system.

8. The method of claim 7, wherein said step of projecting is effected with a shadow moiré

system.

9. The method of claim 1, wherein said step of regulating temperature further includes the step of heating effected by at least one heating source.

10. The method of claim 9, wherein said at least one heating source is a variable output heating source such that said step of heating is effected by adjusting an output temperature of said variable output heating source.

11. The method of claim 1, wherein said step of regulating temperature further includes the step of cooling effected by at least one cooling source.

12. The method of claim 11, wherein said at least one cooling source is a variable output cooling source such that said step of cooling is effected by adjusting an output temperature of said variable output cooling source.

13. The method of claim 1, further comprising the step of:

detecting motion of said reference point as temperature is regulated in said chamber; and

adjusting at least one support post holding said workpiece such that position of said reference point is maintained at a fixed position in space as thermally induced warpages are induced in said workpiece during simulation of the prefined temperature/time profile.

14. A system for measuring thermally induced warpage, comprising:

means for positioning a workpiece in a chamber;

means for projecting a plurality of fringe patterns on said workpiece;

means for regulating temperature in said chamber;

means for recording images of said fringe patterns projected on said workpiece;

means for analyzing changes in said plurality of fringe patterns; and

means for maintaining position of a reference point associated with said workpiece at a fixed position in space during simulation of a predefined temperature/time profile.

15. The system of claim 14, wherein said means for regulating temperature further includes means for changing temperature in said chamber to a plurality of predefined temperature values corresponding to a plurality of predefined times.

16. The system of claim 14, wherein said means for projecting is effected with a shadow moiré

system.

17. The system of claim 14, wherein said means for regulating temperature further includes means for heating effected by a plurality of heating means.

18. The system of claim 14, wherein said means for regulating temperature further includes means for blowing gasses residing in said chamber.

19. The system of claim 14, wherein said means for projecting is effected with a projection moiré

system.

20. The system of claim 19, wherein said means for projecting is effected with a shadow moiré

system.

21. The system of claim 14, wherein said means for regulating temperature further includes means for heating effected by at least one heating means.

22. The system of claim 21, wherein said means for heating is a variable output heating means such that heating is effected by adjusting an output temperature of said variable output heating means.

23. The system of claim 14, wherein said means for regulating temperature further includes means for cooling effected by at least one cooling means.

24. The system of claim 23, wherein said means for cooling is a variable output cooling means such that cooling is effected by adjusting an output temperature of said variable output cooling means.

25. The system of claim 14, wherein said means for regulating temperature further includes means for venting hot gasses such that hot gasses residing in said chamber are expelled from said chamber.

26. A system for measuring thermally induced warpage, comprising:

a projection moiré

system, wherein said projection moiré

system projects a plurality of fringe patterns on a workpiece;

a chamber, wherein said workpiece is positioned;

at least one heating source wherein temperature in said chamber may be increased;

at least one cooling source wherein temperature in said chamber may be decreased, such that thermally induced warpages induced in said workpiece may be analyzed; and

a moveable frame wherein said workpiece is secured thereto such that position of a reference point associated with said workpiece is maintained at a fixed position in space as thermally induced warpages are induced in said workpiece during simulation of a predefined temperature/time profile.

27. The system of claim 26, further comprising a plurality of heating sources.

28. The system of claim 26, wherein said at least one heating source is a variable output heating source such that heating is effected by adjusting an output temperature of said variable output heating source.

29. The system of claim 26, wherein said at least one cooling source is a variable output cooling source such that cooling is effected by adjusting an output temperature of said variable output cooling source.

30. The system of claim 26, wherein said projection moiré

system further comprises a processor such that changes on warpage in said workpiece induces by increase and decreases in temperature in said chamber may be analyzed.

31. The system of claim 26, further comprising a vent such that hot gasses residing in said chamber are expelled from said chamber.

32. The system of claim 26, further comprising at least one blower residing in said chamber such that hot gasses residing in said chamber are circulated.

33. The system of claim 26, further comprising:

a position detector which detects the position of a reference point on said workpiece;

a plurality of adjustable support posts attached to said moveable frame; and

a position controller wherein said position controller detects movement of said reference point and transmits commands to said adjustable support posts, such that said reference point is maintained at a fixed position in space during simulation of the predefined temperature/time profile.

34. The system of claim 26, further comprising:

a position detector which detects the position of a reference point on said moveable frame;

a plurality of adjustable support posts attached to said moveable frame;

a position controller wherein said position controller detects movement of said reference point; and

an adjusting means connected to said adjustable support posts such that said adjusting means adjusts said adjustable support posts according to a plurality of commands received from said position controller, such that said reference point is maintained at a fixed position in space during simulation of the predefined temperature/time profile.

35. A computer readable medium having a temperature control program, the program comprising logic configured to perform the steps of:

regulating temperature in a chamber;

storing a plurality of images recorded by a camera of a plurality of fringe patterns projected onto a workpiece;

analyzing changes in said plurality of fringe patterns; and

determining motion of a reference point associated with said workpiece based upon information provided by at least one position detector; and

controlling at least one support post holding said workpiece such that position of said reference point is maintained at a fixed position in space as thermally induced warpages are induced in said workpiece during simulation of a predefined temperature/time profile.