Apparatus and method for profiling a beam

• US 5,267,013 A
• Filed: 10/07/1991
• Issued: 11/30/1993
• Est. Priority Date: 04/18/1988
• Status: Expired due to Term

• Current Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Original Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Inventors: Spence, Stuart T.
• Primary Examiner(s): Rosenberger, Richard A.
• Assistant Examiner(s): Pham, Hoa Q.
• Application Number:
  US07/772,575
• Time in Patent Office: 785 Days
• Field of Search: 356/121-123, 356/153, 356/237, 356/355, 356/356, 250/347, 250/239, 425/174, 425/174.1, 104/35, 204/22, 204/25, 204/40.1, 204/250, 204/308
• US Class Current: 356/121
• CPC Class Codes: B29C 64/135 the energy source being concentrated, e.g. scanning lasers or focused light sources
• CPC Class Codes: B29C 64/40 Structures for supporting 3D objects during manufacture and intended to be sacrificed after completion thereof
• 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
• CPC Class Codes: G03F 7/0037 Production of three-dimensional images
• CPC Class Codes: G03F 7/70416 2.5D lithography
• CPC Class Codes: G05B 2219/49013 Deposit layers, cured by scanning laser, stereo lithography SLA, prototyping
• CPC Class Codes: G06T 17/00 Three dimensional [3D] modelling, e.g. data description of 3D objects
• CPC Class Codes: G06T 17/10 Constructive solid geometry [CSG] using solid primitives, e.g. cylinders, cubes
• CPC Class Codes: G06T 17/20 Finite element generation, e.g. wire-frame surface description, tesselation

Abstract

An apparatus and a method for profiling the intensity of a beam and thus measuring the overall intensity and power of a beam are disclosed that have particular use in stereolithography. A beam sensor comprising a pinhole in a plate and a photodetector behind the pinhole measures the intensity of portions of a beam as the beam is moved over the beam sensor. Software associated with the sensors in a computer controls the scanning mechanism for the beam so that the beam is shifted to find the pinhole and move across it in order to develop the intensity profile. The invention can be used to detect drift in the scanning mechanism, determine the focus of the beam, and predict the depth and width of photopolymer cured by the beam.

Claims

1. An apparatus for determining a cure parameter in a stereolithography device for producing a three-dimensional object from a medium solidifiable to varying depths upon varying exposure to a reaction means having portions of varying intensity, said reaction means operating and moving in a prescribed pattern onto the medium, comprising:

at least one sensor for sensing and individually recording the intensity of portions of the reaction means when said portions of the reaction means are incident on said at least one sensor, whereby an intensity distribution for the reaction means is obtained;

means for operating and moving the reaction means relative to the medium;

means for determining net exposure of the medium based on the sensing of intensity by said at least one sensor and movement of the reaction means; and

means for determining the cure parameter of the medium based upon the determined net exposure and known properties of the medium.

2. The apparatus of claim 1, additionally comprising:

an independent means for determining a total power in the reaction means;

means for summing individual intensity values to obtain a summed uncalibrated intensity value;

means for calibrating the individual intensity values by utilization of a scaling factor obtained from a ratio of said total power and said summed uncalibrated intensity value.

3. The apparatus of claim 1 wherein the reaction means comprises an electromagnetic beam.

4. The apparatus of claim 3 wherein the beam is a laser beam.

5. The apparatus of claim 4 wherein the means for operating and moving the reaction means comprises two rotatable mirrors for displacing the reaction means.

6. The apparatus of claim 5 wherein the medium is a fluid.

7. The apparatus of claim 6 wherein the fluid is a photopolymer.

8. The apparatus of claim 7 wherein the cure parameter is cure depth.

9. The apparatus of claim 8 wherein the means for calculating the cure depth calculates a cure depth profile.

10. The apparatus for claim 8 wherein the cure parameter is cure width.

11. A method for calculating a cure parameter in a stereolithography apparatus for producing a three-dimensional object from a medium solidifiable to varying depths upon varying exposure to a reaction means having portions of varying intensity, said reaction means operating and moving in a prescribed pattern on the medium, comprising the steps of:

a) directing portions of the reaction means onto at least one sensor and sensing the intensity of said portions of the reaction means, whereby an intensity distribution for the reaction means is obtained;

b) determining an exposure of the medium based on the sensed intensity of and movement of the reaction means; and

c) determining the cure parameter of the medium based upon said exposure of the medium by the reaction means and known characteristics of the medium.

12. The method of claim 11 wherein the cure parameter is cure depth.

13. The method of claim 11 wherein the cure parameter is cure width.

14. The method of claim 11 additionally comprising:

determining a total power in the reaction means using an independent sensor;

summing individual intensity values to obtain a summed uncalibrated intensity value;

calibrating the individual intensity values by utilizing a scaling factor obtained from a ratio of said total power and said summed uncalibrated intensity value.

15. An apparatus for determining a scanning parameter necessary to achieve a desired cure parameter in a stereolithography device for producing a three-dimensional object from a medium solidifiable to varying depths upon varying exposure to a reaction means operating in a prescribed pattern onto a surface of the medium, comprising:

means for determining a required exposure to obtain the desired cure parameter in an area element of the medium, based on curing characteristics of the medium;

means for generating a profile of an intensity of the reaction means including at least one sensor for detecting portions of the reaction means;

means for specifying at least one scanning path of the reaction means as it crosses the area element of the medium;

means for determining an integrated intensity profile of the reaction means for the at least one scanning path by utilizing the profile of the intensity of the reaction means and the at least one scanning path; and

means for determining the scanning parameter at which the reaction means must move across the area element along said at least one path, such that the reaction means appropriately exposes the area element, by utilizing the integrated intensity profile of the reaction means, that at least one scanning path, and the required exposure.

16. The apparatus of claim 15, additionally comprising:

an independent means for determining a total power in the reaction means;

means for summing individual intensity values to obtain a summed uncalibrated intensity value;

means for calibrating the individual intensity values by utilization of a scaling factor obtained from a ratio of said total power and said summed uncalibrated intensity value.

17. The apparatus of claim 15 wherein the reaction means comprises an electromagnetic beam.

18. The apparatus of claim 17 wherein the beam is a laser beam.

19. The apparatus of claim 18 wherein the means for operating the reaction means comprises two rotatable mirrors for displacing the reaction means.

20. The apparatus of claim 19 wherein the medium is a fluid.

21. The apparatus of claim 20 wherein the fluid medium is a photopolymer.

22. The apparatus of claim 21 wherein the cure parameter is cure depth.

23. The apparatus of claim 21 wherein the scanning parameter is scanning speed.

24. The apparatus of claim 21 wherein the scanning parameter is step period.

25. The apparatus of claim 21 wherein the scanning parameter is step size.

26. A method for determining a scanning parameter necessary to achieve a desired cure parameter in a stereolithography device for producing a three-dimensional object from a medium solidifiable to varying depths upon varying exposure to a reaction means operating in a prescribed pattern onto a surface of the medium, comprising the steps of:

determining a required exposure to obtain the desired cure parameter in an area element of the medium, based on characteristics of the medium;

generating a profile of an intensity of the reaction means including using a sensor to detect portions of the reaction means;

specifying at least one scanning path of the reaction means as it crosses the area element of the medium;

determining an integrated intensity profile of the reaction means for the at least one scanning path by utilizing the profile of the intensity of the reaction means and the at least one scanning path; and

determining the scanning parameter at which the reaction means must move across the area element along said at least one scanning path, such that the integrated intensity profile of the reaction means appropriately exposes the area element, by utilizing the integrated intensity profile of the reaction means, the at least one scanning path of the reaction means, and the required exposure.

27. The method of claim 26 wherein the cure parameter is cure depth.

28. The method of claim 26 wherein the medium is a photopolymer having a critical exposure and having an absorption characteristic which substantially follows Beer'"'"'s law wherein the absorption characteristic is penetration depth.

29. The method of claim 26 additionally comprising:

determining a total power in the reaction means using an independent sensor;

summing individual intensity values to obtain a summed uncalibrated intensity value;

calibrating the individual intensity values by utilizing a scaling factor obtained from a ratio of said total power and said summed uncalibrated intensity value.

30. The method of claim 29 wherein the reaction means is a laser beam and the medium is a photopolymer.

31. A method for determining a cure depth of an area element of a medium in a stereolithography device for producing a three-dimensional object on substantially a layer by layer basis, wherein the medium is solidifiable to a depth which is determined by exposure of the medium to a reaction means operating in a prescribed pattern at a working surface of the medium, said reaction means having portions of varying intensity, comprising the steps of:

sensing and individually recording the intensity of portions of the reaction means when said portions of the reaction means are incident on at least one sensor, whereby an intensity distribution of the reaction means is obtained;

determining net exposure in the area element of the medium at approximately the working surface by summing the intensity of each portion of the reaction means that is passed over the area element, wherein the intensity of each portion is multiplied by a time over which each portion of the reaction means is incident on the area element; and

determining the cure depth of the area element of the medium provided by the exposure from the reaction means and known curing properties of the medium.

32. The method of claim 31 additionally comprising:

determining a total power in the reaction means using an independent sensor;

summing individual intensity values to obtain a summed uncalibrated intensity value;

calibrating the individual intensity values by utilizing a scaling factor obtained from a ratio of said total power and said summed uncalibrated intensity value.

33. In a method for determining a cure parameter in a stereolithography apparatus for producing a three-dimensional object from a medium solidifiable to varying depths upon varying exposure to a beam of light, said beam of light operating and moving in a prescribed pattern on the medium, comprising the step of forming successive layers of medium in preparation for forming successive layers of said three-dimensional object and the step of forming said successive layers of said three-dimensional object by selectively exposing said successive layers of medium to said beam of light, the improvement comprising the steps of:

determining an exposure of the medium based on an intensity distribution of the beam of light and movement of the beam of light including the step of directing a plurality of portions of the beam of light onto at least one sensor and measuring amounts of light received by said at least one sensor; and

determining the cure parameter of the medium based upon said determined exposure and known characteristics of the medium.

34. In an apparatus for determining a cure parameter in a stereolithography apparatus for producing a three-dimensional object from a medium solidifiable to varying depths upon varying exposure to a beam of light, said beam of light operating and moving in a prescribed pattern on the medium, comprising means for forming successive layers of medium in preparation for forming successive layers of said three-dimensional object and means for forming said successive layers of said three-dimensional object by selectively exposing said successive layers of medium to said beam of light, the improvement comprising:

at least one sensor;

means for determining an exposure of the medium based on an intensity distribution and movement of the beam of light including means for directing a plurality of portions of the beam of light onto the at least one sensor and means for measuring amounts of light received by said at least one sensor; and

means for determining the cure parameter of the medium based upon said determined exposure and known characteristics of the medium.

35. In a method for determining a desired scanning parameter necessary to achieve a desired cure parameter in a stereolithography apparatus for producing a three-dimensional object from a medium solidifiable to varying depths upon varying exposure to a beam of light, said beam of light operating and moving in a prescribed paths on the medium, comprising the step of forming successive layers of medium in preparation for forming successive layers of said three-dimensional object and the step of forming said successive layers of said three-dimensional object by selectively exposing said successive layers of medium to said beam of light, the improvement comprising the steps of:

determining a required exposure to obtain the desired cure parameter in an area element of the medium, based on known characteristics of the medium;

specifying at least one scanning path of the beam of light as it crosses the area element of the medium;

determining the scanning parameter for the beam of light, along said at least one scanning path that yields said desired cure parameter, by utilizing the required exposure and by determining and utilizing an exposure of the medium based on an intensity profile of the beam of light and the at least one scanning path, including directing a plurality of portions of the beam of light onto at least one sensor and measuring amounts of light received by said at least one sensor.

36. In an apparatus for determining a desired scanning parameter necessary to achieve a desired cure parameter in a stereolithography apparatus for producing a three-dimensional object from a medium solidifiable to varying depths upon varying exposure to a beam of light, said beam of light operating and moving along prescribed paths on the medium, comprising means for forming successive layers of medium in preparation for forming successive layers of said three-dimensional object and means for forming said successive layers of said three-dimensional object by selectively exposing said successive layers of medium to said beam of light, the improvement comprising:

at least one sensor for sensing portions of the beam of light;

means for determining a required exposure to obtain the desired cure parameter in an area element of the medium, based on known characteristics of the medium;

means for specifying at least one scanning path of the beam of light as it crosses the area element of the medium;

means for determining the scanning parameter for the beam of light, along said at least one scanning path that yields said desired cure parameter, by utilizing the required exposure and by determining and utilizing an exposure of the medium based on an intensity profile of the beam of light and the at least one scanning path, including directing a plurality of portions of the beam of light onto the at least one sensor and measuring amounts of light received by said at least one sensor.

37. In a method for determining a cure parameter in a stereolithography apparatus for producing a three-dimensional object from a medium solidifiable to varying depths upon varying exposure to a beam of light, said beam of light operating and moving in a prescribed pattern on the medium, comprising the step of forming successive layers of medium in preparation for forming successive layers of said three-dimensional object and the step of forming said successive layers of said three-dimensional object by selectively exposing said successive layers of medium to said beam of light, the improvement comprising the steps of:

determining a summed intensity distribution of the beam of light, including the step of directing a plurality of portions of the beam of light onto at least one sensor and measuring the amounts of light received by said at least one sensor;

deriving an exposure of the medium based on the summed intensity distribution of and movement of the beam of light; and

determining the cure parameter of the medium based upon said derived exposure and known characteristics of the medium.

38. In an apparatus for determining a cure parameter in a stereolithography apparatus for producing a three-dimensional object from a medium solidifiable to varying depths upon varying exposure to a beam of light, said beam of light operating and moving in a prescribed pattern on the medium, comprising means for forming successive layers of medium in preparation for forming successive layers of said three-dimensional object and means for forming said successive layers of said three-dimensional object by selectively exposing said successive layers of medium to said beam of light, the improvement comprising:

at least one sensor;

means for determining a summed intensity distribution of the beam of light, including the step of directing a plurality of portions of the beam of light onto the at least one sensor and measuring amounts of light received by said at least one sensor;

means for deriving an exposure of the medium based on the summed intensity distribution of and the movement of the beam of light; and

means for determining the cure parameter of the medium based upon said derived exposure and known characteristics of the medium.

39. In a method for determining a desired scanning parameter necessary to achieve a desired cure parameter in a stereolithography apparatus for producing a three-dimensional object from a medium solidifiable to varying depths upon varying exposure to a beam of light, said beam of light operating and moving along prescribed paths on the medium, comprising the step of forming successive layers of medium in preparation for forming successive layers of said three-dimensional object and the step of forming said successive layers of said three-dimensional object by selectively exposing said successive layers of medium to said beam of light, the improvement comprising the steps of:

determining a required exposure to obtain the desired cure parameter in an area element of the medium, based on known characteristics of the medium;

specifying at least one scanning path of the beam of light as it crosses the area element of the medium;

determining a summed intensity distribution of the beam of light along the at least one scanning path, comprising the step of directing a plurality of portions of the beam of light onto at least one sensor and measuring amounts of light received by said at least one sensor;

determining the scanning parameter at which the beam of light must move across the area element along said at least one path, such that the beam of light appropriately exposes the area element, by utilizing the integrated intensity profile of the beam of light, the at least one path of the beam of light, and the required exposure.

40. An improved stereolithography apparatus for producing a three-dimensional object from a medium solidifiable to varying depths upon varying exposure to a beam of light, said beam of light operating and moving along prescribed paths on the medium, comprising means for forming successive layers of medium in preparation for forming successive layers of said three-dimensional object and means for forming said successive layers of said three-dimensional object by selectively exposing said successive layers of medium to said beam of light, the improvement comprising:

means for determining a required exposure to obtain the desired cure parameter in an area element of the medium, based on known characteristics of the medium;

at least one sensor;

means for specifying at least one scanning path of the beam of light as it crosses the area element of the medium;

means for determining a summed intensity distribution of the beam of light for the at least one scanning path, including means for directing a plurality of portions of the beam of light onto the at least one sensor and measuring amounts of light received by said at least one sensor; and

means for determining the scanning parameter at which the beam of light must move across the area element along said at least one path, such that the summed intensity distribution of the beam of light appropriately exposes the area element, by utilizing the summed intensity profile of the beam of light, the at least one path of the beam of light, and the required exposure.