Calibrating a focused beam of energy in a solid freeform fabrication apparatus by measuring the propagation characteristics of the beam

• US 6,646,728 B1
• Filed: 07/09/2001
• Issued: 11/11/2003
• Est. Priority Date: 07/09/2001
• Status: Expired due to Term

• Current Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Original Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Inventors: Partanen, Jouni P., Tang, Nansheng
• Primary Examiner(s): Evans, F. L.
• Assistant Examiner(s): GEISEL, KARA E
• Application Number:
  US09/901,163
• Time in Patent Office: 855 Days
• Field of Search: 356/121, 356/122, 425/174.4
• US Class Current: 356/122
• CPC Class Codes: B23K 26/705 Beam measuring device
• CPC Class Codes: B29C 64/135 the energy source being concentrated, e.g. scanning lasers or focused light sources
• CPC Class Codes: B33Y 30/00 Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B33Y 40/00 Auxiliary operations or equipment, e.g. for material handling
• CPC Class Codes: G01J 1/4257 applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam monitoring arrangements for lasers in general H01S3/0014

Abstract

The invention relates in general to calibrating a focused beam of energy in a solid freeform fabrication apparatus, and, in particular, to a method of measuring the propagation characteristics of the beam to produce beam propagation data. The beam propagation data can be used to verify that the beam is operating within tolerance, and/or produce a response that can be used to further calibrate the beam. The invention is particularly useful in determining asymmetric conditions in the beam. The beam propagation data is produced in accord with the “M²” standard for characterizing a beam. In one embodiment, the response indicates the beam is unacceptable for use in the apparatus. In another embodiment, the response is provided to calibrate the focal position of the beam. In still another embodiment, the response is provided to an adjustable beam that eliminates the asymmetric condition.

Claims

1. A method of measuring the propagation characteristics of a focused beam of energy along a propagation axis in a solid freeform fabrication apparatus, the propagation characteristics established by beam conditioning optics, the method comprising:

directing the focused beam of energy to a profiling stage on the apparatus, the profiling stage receiving the focused beam of energy having substantially the same propagation characteristics used by the apparatus when forming a three-dimensional object;

taking a first set of at least two measurements indicative of a beam width of the focused beam of energy at the profiling stage, the first set of measurements associated with a first planar position orthogonal to the propagation axis of the focused beam of energy;

shifting the propagation characteristics of the focused beam of energy respectively with the profiling stage along the propagation axis of the focused beam by a first relative distance;

taking a second set of at least two measurements indicative of the beam width of the focused beam of energy at the profiling stage, the second set of measurements associated with a second planar position orthogonal to the propagation axis of the focused beam of energy;

shifting the propagation characteristics of the focused beam of energy respectively with the profiling stage along the propagation axis of the focused beam by a second relative distance;

taking a third set of at least two measurements indicative of the beam width of the focused beam of energy at the profiling stage, the third set of measurements associated with a third planar position orthogonal to the propagation axis of the focused beam of energy;

producing beam propagation data from the sets of measurements taken in each of the planar positions and the first and second relative distances;

analyzing the beam propagation data to detect a non-optimal condition of the beam; and

producing at least one response when a non-optimal condition is detected.

2. The method of claim 1 wherein the step of taking the first set, the second set, and the third set of measurements further comprises:

providing at least one sensor at the profiling stage;

moving the focused beam of energy across the sensor to obtain a plurality of intensity readings indicative of a profile of the focused beam of energy, the plurality of intensity readings being taken for each planar position; and

analyzing the plurality of intensity readings to determine the measurements indicative of the beam width for each planar position.

3. The method of claim 2 wherein the step of shifting the propagation characteristics of the focused beam of energy respectively with the profiling stage is accomplished by moving the profiling stage in a direction along the propagation axis while the propagation characteristics of the focused beam of energy remains stationary.

4. The method of claim 2 wherein the step of shifting the propagation characteristics of the focused beam of energy respectively with the profiling stage is accomplished by moving the propagation characteristics of the focused beam of energy in a direction along the propagation axis while the profiling stage remains stationary.

5. The method of claim 4 wherein the propagation characteristics of the focused beam of energy is respectively shifted along the propagation axis of the beam by adjusting the beam conditioning optics without substantially altering the propagation characteristics of the beam.

6. The method of claim 4 wherein the propagation characteristics of the focused beam of energy is respectively shifted along the propagation axis of the beam by moving the focused beam of energy in the apparatus without adjusting the beam conditioning optics.

7. The method of claim 1 wherein the non-optimal condition detected is an out-of-focus condition, an astigmatic condition, an asymmetrical waist condition, an asymmetrical divergence condition, or combination thereof.

8. The method of claim 7 wherein the first, the second, and the third sets of at least two measurements are taken with one measurement being taken in a first direction and the other measurement being taken in a second direction, the first and second directions for each planar position being mutually perpendicular and symmetrically oriented about the propagation axis of the focused beam of energy.

9. The method of claim 8 wherein the step of analyzing the beam propagation data comprises:

(a) determining a first beam waist from the measurements taken in the first direction;

(b) determining a second beam waist from the measurements taken in the second direction;

(c) determining a first focal point value between the first beam waist on the propagation axis and a reference point on the beam propagation axis;

(d) determining a second focal point value between the second beam waist on the propagation axis and the reference point; and

(e) determining an astigmatism value by comparing the first focal point value and the second focal point value.

10. The method of claim 9 wherein the response is determined by comparing the astigmatism value to a range of astigmatism values acceptable for the solid freeform fabrication apparatus.

11. The method of claim 9 wherein the response is determined by processing any combination of the astigmatism value, the first beam waist, and the second beam waist.

12. The method of claim 9 wherein the step of analyzing the beam propagation data further comprises:

(a) determining a first divergence angle from the measurements taken in the first direction;

(b) determining a second divergence angle from the measurements taken in the second direction;

(c) determining a first times-diffraction-limit number from the measurements taken in the first direction;

(d) determining a second times-diffraction-limit number from the measurements taken in the second direction; and

(e) wherein the response is determined by processing any combination of the astigmatism value, the first beam waist, the second beam waist, the first divergence angle, the second divergence angle, the first times-diffraction-limit number, and the second times-diffraction-limit number.

13. The method of claim 1 wherein the beam propagation data is delivered to a display device of the solid freeform fabrication device to produce a graphic display of the propagation characteristics of the beam.

14. The method of claim 1 wherein the response is delivered to the beam conditioning optics to adjust the beam conditioning optics to achieve an optimized position for the focused beam of energy for the apparatus.

15. A method of calibrating a focused beam of energy in a solid freeform fabrication apparatus by detecting and eliminating a non-optimal condition present in propagation characteristics of the focused beam, the propagation characteristics established by beam conditioning optics, the method comprising:

directing the focused beam of energy to a profiling stage on the apparatus, the profiling stage receiving the focused beam of energy having substantially the same propagation characteristics used by the apparatus when forming a three-dimensional object;

taking a first set of at least two measurements indicative of a beam width of the focused beam of energy at the profiling stage, the first set of measurements associated with a first planar position orthogonal to a propagation axis of the focused beam of energy;

shifting the propagation characteristics of the focused beam of energy respectively with the profiling stage along the propagation axis of the focused beam by a first relative distance;

taking a second set of at least two measurements indicative of the beam width of the focused beam of energy at the profiling stage, the second set of measurements associated with a second planar position orthogonal to the propagation axis of the focused beam of energy;

shifting the propagation characteristics of the focused beam of energy respectively with the profiling stage along the propagation axis of the focused beam by a second relative distance;

taking a third set of at least two measurements indicative of the beam width of the focused beam of energy at the profiling stage, the third set of measurements associated with a third planar position orthogonal to the propagation axis of the focused beam of energy;

producing beam propagation data from the sets of measurements taken in each of the planar positions and the first and second relative distances;

analyzing the beam propagation data to detect a non-optimal condition of the beam;

producing at least one response when a non-optimal condition is detected;

delivering the response to the beam conditioning optics; and

adjusting the beam conditioning optics upon the delivery of the response to substantially eliminate the non-optimal condition.

16. The method of claim 15 wherein the step of taking the first set, the second set, and the third set of measurements further comprises:

providing at least one sensor at the profiling stage;

moving the focused beam of energy across the sensor to obtain a plurality of intensity readings indicative of a profile of the focused beam of energy, the plurality of intensity readings being taken for each planar position; and

analyzing the plurality of intensity readings to determine the measurements indicative of the beam width for each planar position.

17. The method of claim 16 wherein the step of shifting the propagation characteristics of the focused beam of energy respectively with the profiling stage is accomplished by moving the profiling stage in a direction along the propagation axis while the propagation characteristics of the focused beam of energy remains stationary.

18. The method of claim 16 wherein the step of shifting the propagation characteristics of the focused beam of energy respectively with the profiling stage is accomplished by moving the propagation characteristics of the focused beam of energy in a direction along the propagation axis while the profiling stage remains stationary.

19. The method of claim 18 wherein the propagation characteristics of the focused beam of energy are respectively shifted along the propagation axis of the beam by adjusting the beam conditioning optics without substantially altering the propagation characteristics of the beam.

20. The method of claim 18 wherein the propagation characteristics of the focused beam of energy are respectively shifted along the propagation axis of the beam by moving the focused beam of energy in the apparatus without adjusting the beam conditioning optics.

21. The method of claim 15 wherein the non-optimal condition detected is an out-of-focus condition, an astigmatic condition, an asymmetrical waist condition, an asymmetrical divergence condition, or combination thereof.

22. The method of claim 21 wherein the first, the second, and the third sets of at least two measurements are taken with one measurement being taken in a first direction and the other measurement being taken in a second direction, the first and second directions for each planar position being mutually perpendicular and symmetrically oriented about the propagation axis of the focused beam of energy.

23. The method of claim 22 wherein the step of analyzing the beam propagation data comprises:

(a) determining a first beam waist from the measurements taken in the first direction;

(b) determining a second beam waist from the measurements taken in the second direction;

(c) determining a first focal point value between the first beam waist on the propagation axis and a reference point on the beam propagation axis;

(d) determining a second focal point value between the second beam waist on the propagation axis and the reference point; and

(e) determining an astigmatism value by comparing the first focal point value and the second focal point value.

24. The method of claim 23 wherein the step of analyzing the beam propagation data further comprises:

(a) determining a first divergence angle from the measurements taken in the first direction;

(b) determining a second divergence angle from the measurements taken in the second direction;

(c) determining a first times-diffraction-limit number from the measurements taken in the first direction; and

(d) determining a second times-diffraction-limit number from the measurements taken in the second direction.

25. The method of claim 24 wherein the response is determined by processing any combination of the measurements taken in the first direction, the measurements taken in the second direction, a ratio between the first and second relative distances, the first focal point value, the second focal point value, the astigmatism value, the first beam waist, the second beam waist, the first divergence angle, the second divergence angle, the first times-diffraction-limit number, and the second times-diffraction-limit number.

26. The method of claim 15 wherein the beam propagation data is delivered to a display device of the solid freeform fabrication device to produce a graphic display of the propagation characteristics of the beam.

33. The apparatus of claim 15 wherein the non-optimal condition detected is an out-of-focus condition, an astigmatic condition, an asymmetrical waist condition, an asymmetrical divergence condition, or combination thereof.

34. The apparatus of claim 33 wherein the first, the second, and the third sets of at least two measurements are taken with one measurement being taken in a first direction and the other measurement being taken in a second direction, the first and second directions for each planar position being mutually perpendicular and symmetrically oriented about the propagation axis of the focused beam of energy.

35. The apparatus of claim 34 wherein the controller analyzes the beam propagation data and determines:

(a) a first beam waist from the measurements taken in the first direction;

(b) a second beam waist from the measurements taken in the second direction;

(c) a first focal point value between the first beam waist on the propagation axis and a reference point on the beam propagation axis;

(d) a second focal point value between the second beam waist on the propagation axis and the reference point; and

(e) an astigmatism value by comparing the first focal point value and the second focal point value.

36. The apparatus of claim 34 wherein the response produced by the controller is determined by comparing the astigmatism value to a range of astigmatism values acceptable for the solid freeform fabrication apparatus.

37. The apparatus of claim 34 wherein the response produced by the controller is determined by processing any combination of the astigmatism value, the first beam waist, and the second beam waist.

38. The apparatus of claim 34 wherein the controller analyzes the beam propagation data and determines:

(a) a first divergence angle from the measurements taken in the first direction;

(b) a second divergence angle from the measurements taken in the second direction;

(c) a first times-diffraction-limit number from the measurements taken in the first direction;

(d) a second times-diffraction-limit number from the measurements taken in the second direction; and

(e) the response from any combination of the astigmatism value, the first beam waist, the second beam waist, the first divergence angle, the second divergence angle, the first times-diffraction-limit number, and the second times-diffraction-limit number.

27. A solid freeform fabrication apparatus adapted to measure the propagation characteristics of a focused beam of energy utilized by the apparatus when forming three-dimensional objects from a build material, the apparatus comprising:

an apparatus structure;

a platform in communication with the apparatus structure for supporting the build material of the three-dimensional object when the three-dimensional object is formed by the apparatus;

a laser beam generator in communication with the apparatus structure for producing the energy that is transmitted in the focused beam of energy;

beam conditioning optics in communication with the apparatus structure, the beam conditioning optics receiving the energy transmitted from the laser beam generator and projecting the focused beam of energy about a propagation axis;

scanning optics in communication with the apparatus structure receiving the focused beam of energy and directing the focused beam of energy towards the platform;

a profiling stage in communication with the apparatus structure and adapted for receiving the focused beam of energy from the scanning optics;

at least one sensor in communication with the profiling stage to take at least two measurements indicative of the beam width of the focused beam of energy at the profiling stage;

a controller in communication with at least the beam conditioning optics, the scanning optics, the sensor, the platform; and

wherein the controller

(a) produces beam propagation data from sets of at least two measurements indicative of the beam width, the first set taken in a first planar position, the second set taken in a second planar position, and the third set taken in a third planar position;

(b) analyzes the beam propagation data to detect a non-optimal condition of the focused beam; and

(c) produces at least one response when the non-optimal condition of the focused beam is detected.

28. The apparatus of claim 27 wherein the sensor obtains a plurality of intensity readings indicative of a profile of the focused beam of energy at each planar position;

and

the controller analyzes the plurality of intensity readings taken at each planar position to determine the at least two measurements indicative of the beam width for that planar position.

29. The apparatus of claim 28 wherein in order to take the plurality of intensity readings for each planar position, the profiling stage is moved in a direction along the propagation axis while the propagation characteristics of the focused beam of energy remains stationary.

30. The apparatus of claim 28 wherein in order to take the plurality of intensity readings for each planar position, the propagation characteristics of the focused beam of energy is moved in a direction along the propagation axis while the profiling stage remains stationary.

31. The apparatus of claim 30 wherein in order to take the plurality of intensity readings for each planar position, the propagation characteristics of the focused beam of energy is respectively shifted along the propagation axis of the beam by adjusting the beam conditioning optics without substantially altering the propagation characteristics of the beam.

32. The apparatus of claim 30 wherein in order to take the plurality of intensity readings for each planar position, the propagation characteristics of the focused beam of energy is respectively shifted along the propagation axis of the beam by moving the focused beam of energy in the apparatus structure without adjusting the beam conditioning optics.

39. The apparatus of claim 27 further comprising:

a display device wherein the controller delivers the beam propagation data to the display device to produce a graphic display of the propagation characteristics of the beam.

40. The method of claim 27 wherein the controller delivers the response to the beam conditioning optics to adjust the beam conditioning optics to achieve an optimized position for the focused beam of energy for the apparatus.

41. A solid freeform fabrication apparatus adapted to calibrate a focused beam of energy utilized by the apparatus when forming three-dimensional objects from a build material, the apparatus comprising:

an apparatus structure;

a platform in communication with the apparatus structure for supporting the build material of the threedimensional object when the three-dimensional object is formed by the apparatus;

a laser beam generator in communication with the apparatus structure for producing the energy that is transmitted in the focused beam of energy;

beam conditioning optics in communication with the apparatus structure, the beam conditioning optics receiving the energy transmitted from the laser beam generator and projecting the focused beam of energy about a propagation axis;

scanning optics in communication with the apparatus structure receiving the focused beam of energy and directing the focused beam of energy towards the platform;

a profiling stage in communication with the apparatus structure and adapted for receiving the focused beam of energy from the scanning optics;

at least one sensor in communication with the profiling stage to take at least two measurements indicative of the beam width of the focused beam of energy at the profiling stage;

a controller in communication with at least the beam conditioning optics, the scanning optics, the sensor, the platform; and

wherein the controller

(a) produces beam propagation data from sets of at least two measurements indicative of the beam width, the first set taken in a first planar position, the second set taken in a second planar position, and the third set taken in a third planar position;

(b) analyzes the beam propagation data to detect a non-optimal condition of the focused beam; and

(c) produces at least one response when the non-optimal condition of the focused beam is detected and delivers the response to the beam conditioning optics to substantially eliminate the non-optimal condition.

42. The apparatus of claim 41 wherein the sensor obtains a plurality of intensity readings indicative of a profile of the focused beam of energy at each planar position;

and

the controller analyzes the plurality of intensity readings taken at each planar position to determine the at least two measurements indicative of the beam width for that planar position.

43. The apparatus of claim 42 wherein in order to take the plurality of intensity readings for each planar position, the profiling stage is moved in a direction along the propagation axis while the propagation characteristics of the focused beam of energy remains stationary.

44. The apparatus of claim 42 wherein in order to take the plurality of intensity readings for each planar position, the propagation characteristics of the focused beam of energy is moved in a direction along the propagation axis while the profiling stage remains stationary.

45. The apparatus of claim 44 wherein in order to take the plurality of intensity readings for each planar position, the propagation characteristics of the focused beam of energy is respectively shifted along the propagation axis of the beam by adjusting the beam conditioning optics without substantially altering the propagation characteristics of the beam.

46. The apparatus of claim 44 wherein in order to take the plurality of intensity readings for each planar position, the propagation characteristics of the focused beam of energy is respectively shifted along the propagation axis of the beam by moving the focused beam of energy in the apparatus structure without adjusting the beam conditioning optics.

47. The apparatus of claim 41 wherein the non-optimal condition detected is an out-of-focus condition, an astigmatic condition, an asymmetrical waist condition, an asymmetrical divergence condition, or combination thereof.

48. The apparatus of claim 47 wherein the first, the second, and the third sets of at least two measurements are taken with one measurement being taken in a first direction and the other measurement being taken in a second direction, the first and second directions for each planar position being mutually perpendicular and symmetrically oriented about the propagation axis of the focused beam of energy.

49. The apparatus of claim 48 wherein the controller analyzes the beam propagation data and determines:

(a) a first beam waist from the measurements taken in the first direction;

(b) a second beam waist from the measurements taken in the second direction;

(c) a first focal point value between the first beam waist on the propagation axis and a reference point on the beam propagation axis;

(d) a second focal point value between the second beam waist on the propagation axis and the reference point; and

(e) an astigmatism value by comparing the first focal point value and the second focal point value.

50. The apparatus of claim 49 wherein the controller further analyzes the beam propagation data and determines:

(a) a first divergence angle from the measurements taken in the first direction;

(b) a second divergence angle from the measurements taken in the second direction;

(c) a first times-diffraction-limit number from the measurements taken in the first direction; and

(d) a second times-diffraction-limit number from the measurements taken in the second direction.

51. The apparatus of claim 50 wherein the controller calculates the response by processing any combination of the measurements taken in the first direction, the measurements taken in the second direction, a ratio between the first and second relative distances, the first focal point value, the second focal point value, the astigmatism value, the first beam waist, the second beam waist, the first divergence angle, the second divergence angle, the first times-diffraction-limit number, and the second times-diffraction-limit number.

52. The apparatus of claim 41 further comprising:

a display device wherein the controller delivers the beam propagation data to the display device to produce a graphic display of the propagation characteristics of the beam.

53. The apparatus of claim 41 wherein the controller delivers the response to the beam conditioning optics to adjust the beam conditioning optics to achieve an optimized position for the focused beam of energy for the apparatus.