Apparatus and method for profiling a beam

• US 5,058,988 A
• Filed: 11/08/1988
• Issued: 10/22/1991
• 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
• Application Number:
  US07/268,816
• Time in Patent Office: 1,078 Days
• Field of Search: 356/121-123, 356/237, 356/356, 356/355, 356/153, 250/347, 250/239, 425/174, 425/174.1, 164/35, 204/22, 204/40.1, 204/25, 204/308, 204/250
• 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 10/00 Processes of additive manufacturing
• 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: B33Y 50/00 Data acquisition or data processing for additive manufacturing
• 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 develope 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:

a sensor for sensing the intensity of a portion of the reaction means when that portion of the reaction means is incident on the sensor;

means for relatively displacing the sensor and the reaction means such that substantially all portions of the reaction means may be sensed by the sensor;

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

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

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

3. The apparatus of claim 2 wherein the beam is a laser beam.

4. The apparatus of claim 2 wherein the medium is a fluid.

5. The apparatus of claim 4 wherein the fluid is a photopolymer.

6. The apparatus of claim 1 wherein the means for relatively displacing comprises two rotatable mirrors for displacing the reaction means.

7. The apparatus of claim 1 wherein the sensor comprises a pinhole in an opaque plate over a detector.

8. The apparatus of claim 1 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 of claim 1 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 a portion of the reaction means onto a sensor and sensing the intensity of the portion of the reaction means;

b) relatively displacing the reaction means and sensor such that a different portion of the reaction means impinges upon the sensor;

c) repeating steps a) and b) until the intensity of substantially all portions of the reaction means have been sensed;

d) calculating an exposure of the medium based on the sensed intensity of and movement of the reaction means; and

e) calculating the cure parameter of the medium based upon the 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. 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 comprising the steps of:

sensing an intensity of a portion of the reaction means when that portion of the reaction means is incident on a sensor;

relatively displacing the sensor and the reaction means such that substantially all portions of the reaction means may be sensed by the sensor;

calculating 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

calculating 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.

15. A method for determining a scanning speed 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;

specifying a scanning direction and path of the reaction means as it crosses the area element of the medium;

calculating an integrated intensity profile of the reaction means in a direction parallel to the scanning direction by utilizing the profile of the intensity of the reaction means and the known scanning direction; and

calculating the scanning speed at which the reaction means must move across the area element, 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 path of the reaction means, and the required exposure.

16. The method of claim 15 wherein the cure parameter is the cure depth.

17. The method of claim 16 wherein the medium is a substance having a critical exposure and having an absorption characteristic which substantially follows Beer'"'"'s law wherein the absorption characteristic is penetration depth.

18. The method of claim 15 wherein the cure parameter is cure width.

19. An apparatus for determining an intensity profile of a reaction means in a stereolithography system for producing a three-dimensional object substantially on a layer by layer basis at a surface of a building medium, comprising:

a sensor for sensing the intensity of part of the reaction means when that part of the reaction means is incident on the sensor; and

a single directing means for directing each part of the reaction means onto the sensor to determine the intensity of each part of the reaction means, thereby determining the intensity profile for the reaction means and for directing the reaction means onto the surface of the medium for producing the object.

20. An apparatus for determining a scanning speed 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 a area element of the medium, based on curing characteristics of the medium;

means for generating a profile of an intensity of the reaction means;

means for specifying a scanning path and direction of the reaction means as it crosses the area element of the medium;

means for calculating an integrated intensity profile of the reaction means in a direction parallel to the scanning direction by utilizing the profile of the intensity of the reaction means and the scanning direction; and

means for calculating the scanning speed at which the reaction means must move across the area element, 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 scanning path and the required exposure.

21. The apparatus of claim 20 wherein the cure parameter is cure depth.

22. The apparatus of claim 20 wherein the cure parameter is cure width.