System and method for imaging apparatus calibration

• US 8,743,340 B2
• Filed: 12/29/2009
• Issued: 06/03/2014
• Est. Priority Date: 12/31/2008
• Status: Active Grant

• Current Assignee: Rolls-Royce Corporation (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls-Royce Corporation (Rolls-Royce Holdings Plc)
• Inventors: Schlienger, Max Eric, Withey, Paul Anthony
• Primary Examiner(s): Whitesell Gordon, Steven H
• Assistant Examiner(s): Asfaw, Mesfin T
• Application Number:
  US12/648,603
• Publication Number:
  US 20100271608A1
• Time in Patent Office: 1,617 Days
• Field of Search: 355/53, 355/55, 355/63, 355/67, 355/77, 353/70, 353/101, 353/121, 353/30, 353/69, 353/76, 348/222.1, 348/383, 348/745, 348/806, 348/190, 348/191, 348/207.1
• US Class Current: 355/53
• CPC Class Codes: B29C 64/264 Arrangements for irradiation
• CPC Class Codes: G03B 17/54 with projector
• CPC Class Codes: G03B 21/005 Projectors using an electronic spatial light modulator but not peculiar thereto
• CPC Class Codes: G03B 21/147 Optical correction of image distortions, e.g. keystone
• CPC Class Codes: G03B 21/53 Means for automatic focusing, e.g. to compensate thermal effects

Abstract

A system is disclosed including an image sensor positioned at a first specified angle relative to a projected image plane. The system includes a projector that projects a test pattern onto the projected image plane. A controller is structured to iteratively adjust the projector focus until an image focus index is maximized, where the image focus index is a function of an amplitude of at least one harmonic frequency of a scan of the test pattern. The controller is further structured to determine a skew indicator value and adjust a projector skew adjustment. The controller is further structured to compare a current zoom level to a target zoom level and adjust a projector zoom. The projected image plane is a manufacturing surface, where the projected image is utilized in a manufacturing process.

Claims

1. A method, comprising:

positioning an image sensor at a first specified angle relative to a projected image plane;

projecting a test pattern onto the projected image plane;

positioning an aperture between the image sensor and the projected image plane;

positioning the image sensor such that a first pixel row of the image sensor is at a second angle relative to an edge of the test pattern;

iteratively scanning the test pattern and adjusting a projector focus value to maximize an image focus index, the image focus index comprising a function of at least one harmonic frequency amplitude of a test pattern scan.

2. The method of claim 1, wherein adjusting the projector focus value comprises at least one of adjusting a projector lens position and adjusting a projection distance comprising a distance between the projector and the projected image.

3. The method of claim 1, wherein the image focus index comprises a member selected from the group consisting of a root-mean-squared (RMS) amplitude value for a first harmonic frequency divided by an RMS amplitude value for the fundamental frequency (FF), a sum of RMS amplitude values for a plurality of harmonic frequencies divided by the RMS amplitude value for the FF, and a sum of RMS amplitude values for each harmonic frequency having an RMS amplitude value at least equal to 1% of the RMS amplitude value for the FF divided by the RMS amplitude value for the FF.

4. The method of claim 1, wherein the aperture comprises a pinhole.

5. The method of claim 1, wherein the aperture comprises an imager lens, and wherein adjusting a projector focus value to maximize an image focus index further includes iteratively adjusting the imager lens position to maximize an imager focus value, and fixing the imager lens position.

6. The method of claim 5, further comprising dithering the imager lens position after adjusting the projector focus value, and re-adjusting the projector focus value in response to the dithering indicating the image focus index is not at a maximum value.

7. The method of claim 1, further comprising determining a skew indicator value, and tuning a projector skew adjustment in response to the skew indicator value.

8. The method of claim 7, wherein the skew indicator value comprises at least one of a ratio of a first fundamental frequency to a second fundamental frequency and a ratio of a first fundamental frequency amplitude to a second fundamental frequency amplitude.

9. The method of claim 8, wherein the skew indicator value comprises at least one of a horizontal skew indicator value and a vertical skew indicator value.

10. The method of claim 8, wherein the projector skew adjustment comprises at least one member selected from the group consisting of a horizontal skew correction, a vertical skew correction, and a projector position.

11. The method of claim 1, further comprising interpreting a target zoom level, determining a current zoom level, and controlling the current zoom level in response to the target zoom level wherein determining the current zoom level comprises interpreting a target fundamental frequency, and interpreting a fundamental frequency (FF) for the test pattern.

12. A system, comprising:

a projector structured to project a test pattern onto a projected image plane;

an image sensor positioned at a first specified angle relative to the projected image plane, wherein a first pixel row of the image sensor is positioned at a second angle relative to an edge of the test pattern;

an aperture positioned between the image sensor and the projected image plane;

a controller structured to iteratively scan the test pattern and adjust a projector focus value to maximize an image focus index, the image focus index comprising a function of at least one harmonic frequency amplitude of a test pattern scan; and

wherein the projector is further structured to project a production image onto a manufacturing surface.

13. The system of claim 12, wherein the aperture comprises one of a pinhole and an imager lens.

14. The system of claim 12, wherein the image sensor comprises one of a charge-coupled device (CCD) and a complementary metal-oxide-semiconductor (CMOS).

15. The system of claim 12, wherein the manufacturing surface comprises a photosensitive polymer layer.

16. The system of claim 12, wherein the controller is further structured to adjust the projector focus value by commanding at least one of a projector lens position actuator and a projection distance actuator.

17. The system of claim 12, wherein the image focus index comprises a member selected from the group consisting of a root-mean-squared (RMS) amplitude value for a first harmonic frequency divided by an RMS amplitude value for the fundamental frequency (FF), a sum of RMS amplitude values for a plurality of harmonic frequencies divided by the RMS amplitude value for the FF, and a sum of RMS amplitude values for each harmonic frequency having an RMS amplitude value at least equal to 1% of the RMS amplitude value for the FF divided by the RMS amplitude value for the FF.

18. The system of claim 12, wherein the projector further includes a skew adjustment comprising at least one member selected from the group consisting of a horizontal skew correction, a vertical skew correction, and a projector position, and wherein the controller is further structured to determine a skew indicator value, and to tune the projector skew adjustment in response to the skew indicator value.

19. The system of claim 18, wherein the skew indicator value comprises at least one of a ratio of a first fundamental frequency to a second fundamental frequency and a ratio of a first fundamental frequency amplitude to a second fundamental frequency amplitude.

20. The system of claim 18, wherein the skew indicator value comprises at least one of a horizontal skew indicator value and a vertical skew indicator value.

21. The system of claim 12, wherein the controller is further structured to interpret a target zoom level, to determine a current zoom level, and to control the current zoom level in response to the target zoom level.

22. The system of claim 12, wherein the controller is further structured to determine the current zoom level by interpreting a target fundamental frequency, and interpreting a fundamental frequency (FF) for the test pattern.

23. The system of claim 12, wherein the first specified angle comprises a parallel angle.

24. The system of claim 12, wherein the second angle comprises a parallel angle.

25. An apparatus, comprising:

a scanning module structured to provide an image sensor scan command, wherein an image sensor creates a test pattern scan in response to the image sensor scan command, wherein the test pattern scan comprises a scan of a test pattern projected onto a manufacturing surface;

a focus definition module structured to determine an image focus index comprising a function of at least one harmonic frequency amplitude of the test pattern scan; and

a focus control module structured to iteratively adjust a projector focus value to maximize the image focus index.

26. The apparatus of claim 25, wherein the focus control module is further structured to iteratively adjust an imager lens position to maximize the image focus index, the apparatus further comprising an imager focus verification module structured to dither the imager lens position, and wherein the focus control module is further structured to re-adjust the projector focus value in response to the dithering of the imager lens position indicating that the image focus index is not at a maximum value.

27. The apparatus of claim 25, further comprising a skew control module structured to determine a skew indicator value as a function of a first fundamental frequency value and a second fundamental frequency value, and to tune a projector skew adjustment in response to the skew indicator value.

28. The apparatus of claim 27, wherein the projector skew adjustment includes at least one member selected from the group consisting of a horizontal skew correction, a vertical skew correction, and a projector position.

29. The apparatus of claim 28, wherein the zoom control module is further structured to determine the current zoom level by interpreting a target fundamental frequency, and interpreting a fundamental frequency (FF) for the test pattern.

30. The apparatus of claim 27, wherein the skew indicator value comprises at least one of a ratio of a first fundamental frequency to a second fundamental frequency and a ratio of a first fundamental frequency amplitude to a second fundamental frequency amplitude.

31. The apparatus of claim 25, further comprising a zoom control module structured to interpret a target zoom level, to determine a current zoom level, and to provide a zoom level command in response to the target zoom level.

32. The apparatus of claim 25, wherein the image focus index comprises a member selected from the group consisting of a root-mean-squared (RMS) amplitude value for a first harmonic frequency divided by an RMS amplitude value for the fundamental frequency (FF), a sum of RMS amplitude values for a plurality of harmonic frequencies divided by the RMS amplitude value for the FF, and a sum of RMS amplitude values for each harmonic frequency having an RMS amplitude value at least equal to 1% of the RMS amplitude value for the FF divided by the RMS amplitude value for the FF.

33. A system, comprising:

a manufacturing surface, an image projector, an imaging sensor, and an aperture disposed between the manufacturing surface and the imaging sensor;

wherein the imaging sensor is positioned at a first specified angle relative to the manufacturing surface and a first pixel row of the imaging sensor is positioned at a second angle relative to an edge of a test pattern projected onto the manufacturing surface;

means for maximizing an image focus index;

means for iteratively scanning the test pattern and adjusting a projector focus value; and

wherein in the means for maximizing the image focus index, the image focus index comprises a function of at least one harmonic frequency amplitude of a test pattern scan.

34. The system of claim 33, further comprising means for determining a skew indicator value, means for tuning a projector skew adjustment in response to the skew indicator value.

35. The system of claim 33, further comprising means for determining a current zoom level, and means for controlling the current zoom level in response to a target zoom level.

36. The system of claim 33, wherein the image focus index comprises a member selected from the group consisting of a root-mean-squared (RMS) amplitude value for a first harmonic frequency divided by an RMS amplitude value for the fundamental frequency (FF), a sum of RMS amplitude values for a plurality of harmonic frequencies divided by the RMS amplitude value for the FF, and a sum of RMS amplitude values for each harmonic frequency having an RMS amplitude value at least equal to 1% of the RMS amplitude value for the FF divided by the RMS amplitude value for the FF.