Process for the production of a three-dimensional object with resolution improvement by "pixel-shift"

• US 20050248062A1
• Filed: 05/09/2005
• Published: 11/10/2005
• Est. Priority Date: 05/10/2004
• Status: Active Grant

• Current Assignee: Envisiontec GmbH
• Original Assignee: Envisiontec GmbH
• Inventors: El-Siblani, Ali, John, Hendrik, Shkolnik, Alexandr
• Granted Patent: US 7,790,093 B2
• Time in Patent Office: Days
• US Class Current: 264/401
• CPC Class Codes: B29C 64/106 using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
• CPC Class Codes: B29C 64/129 characterised by the energy source therefor, e.g. by global irradiation combined with a mask
• CPC Class Codes: B33Y 30/00 Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B33Y 50/00 Data acquisition or data processing for additive manufacturing
• CPC Class Codes: B33Y 50/02 for controlling or regulating additive manufacturing processes
• CPC Class Codes: G03F 7/2022 Multi-step exposure, e.g. hybrid; backside exposure; blanket exposure, e.g. for image reversal; edge exposure, e.g. for edge bead removal; corrective exposure
• CPC Class Codes: G03F 7/70291 Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices

Abstract

The invention relates to a process or a device for the production of a three-dimensional object by layer-wise solidification of a material which is solidifiable under the application of electromagnetic irradiation by means of mask illumination, wherein the mask is produced using an image forming unit having a prescribed resolution, which is formed from a constant number of image forming elements (pixels) being discrete and being arranged in a spatially mutually fixed manner. For the improvement of the resolution along the outer and inner contours of the sectional areas of the object to be generated layer-wise in the sub-pixel range, a multiple illumination per layer is performed, which consists of a series of multiple images that are mutually shifted in the sub-pixel range in the image/construction plane, wherein a separate mask/bitmap is produced for each shifted image.

Claims

1. A process for the production of a three-dimensional object by layer-wise solidification of a material solidifiable by the action of electromagnetic irradiation by means of mask illumination, wherein the mask is produced by an image forming unit having a prescribed resolution, which mask is formed from a constant number of image forming elements (pixel) being discrete and spatially arranged in a fixed manner to each other, characterized in that, for improving the resolution in the sub-pixel range along the outer and inner contours of the sectional areas of the object to be generated layer-wise, a multiple illumination is carried out for each layer which consists of a sequence of a multitude of images mutually shifted in the sub-pixel range in the image/construction plane, wherein a separate mask/bitmap is produced for each shifted image.

2. The process according to claim 1, characterized in that said image forming unit is formed of a constant number of image forming elements (pixel) being discrete and spatially arranged to each other in a two-dimensional matrix.

3. The process according to claim 1, characterized in that a sequence of at least 2 images mutually shifted in the sub-pixel range is carried out in the image/construction plane, corresponding to the resolution of the image forming unit and under consideration of the corresponding sub-pixel shift.

4. The process according to claim 1 for the generation of the bitmap from a sectional area of a three-dimensional object, characterized in that the sectional area, i.e. outer and inner contours, are defined by vectorial trails which are superimposed by technical image processing by a rastered area (bitmap), the resolution of which exactly corresponds to the resolution of the discrete elements (pixels) in the image forming unit and thus in the image in the construction plane, wherein the superimposition of vectorial trails and bitmap takes place in a superior-ordered XY-coordinate system, and wherein the active pixels are calculated by a specific algorithm in order to define the sectional area in the form of a rastered mask.

5. The process according to claim 1, characterized in that the mask generation (bitmapping) of each sectional area of a three-dimensional object is carried out in the starting position and in various states displaced (shifted) in the sub-pixel range in XY, and that a total image having an enhanced resolution in the contour portion corresponding to the pixel shift is obtained by the superimposition of these bitmaps per sectional area.

6. The process according to claim 1, characterized in that a bitmap is produced which is shifted relative to the sectional area by delta X, which results in a new distribution of active pixels.

7. The process according to claim 1, characterized in that a bitmap is produced which is shifted by delta Y in the sub-pixel range relatively to the sectional area, which results in a new distribution of active pixels.

8. The process according to claim 1, characterized in that a bitmap is produced which is shifted along the pixel diagonal by delta X and delta Y relatively to the sectional area, which results in a new distribution of active pixels.

9. The process according to claim 1, characterized in that the total illumination of an individual layer results from the sum of the partial illuminations of the masks/bitmaps shifted in the sub-pixel range.

10. The process according to claim 1, wherein, for each layer of the object, a multitude of masks or bitmaps having different sub-pixel shifts in XY can be generated and can be illuminated serially for each layer to be hardened.

11. The process according to claim 1, characterized in that a simplified process for resolution improvement is achieved in such a manner that only the bitmap of the starting position and the bitmap of the diagonal-shift by a half pixel-diagonal are produced and are subsequently illuminated for each layer to be hardened.

12. The process according to claim 1, characterized in that, for the shifted imaging of the rastered masks/bitmaps in the construction plane which are produced in a shifted manner in the sub-pixel range for the purpose of selectively hardening the material layer, the image forming unit is tilted for each shifted bitmap such that the desired shift of the image in the sub-pixel range in the image/construction plane is achieved.

13. The process according to claim 1, characterized in that, for the shifted imaging of the rastered masks/bitmaps in the construction plane which are produced in a shifted manner in the sub-pixel range for the purpose of selectively hardening the material layer, the image forming unit for each shifted bitmap is shifted by the corresponding sub-pixel range in X and Y, that is parallel in plane to the image/construction plane.

14. The process according to claim 1, characterized in that, for the shifted imaging of the rastered masks/bitmaps in the construction plane which are produced in a shifted manner in the sub-pixel range for the purpose of selectively hardening the material layer, the image forming projection unit is maintained fixed in its position, and the imaging optic of the projection unit is tilted for each shifted bitmap such that the desired shift of the image in the image/construction plane in the sub-pixel range is achieved.

15. The process according to claim 1, characterized in that, for the shifted imaging of the rastered masks/bitmaps in the construction plane which are produced in a shifted manner in the sub-pixel range for the purpose of selectively hardening the material layer, the image forming projection unit is maintained fixed in its position, and the imaging optic of the projection unit is shifted for each shifted bitmap in XY such that the desired shift of the image in the image/construction plane in the sub-pixel range is achieved.

16. The process according to claim 1, characterized in that, for the shifted imaging of the rastered masks/bitmaps in the construction plane which are produced in a shifted manner in the sub-pixel range for the purpose of selectively hardening the material layer, the projection unit is tilted for each bitmap via actuators such that the projected image in the construction plane is shifted in the corresponding sub-pixel range in X and Y.

17. The process according to claim 1, characterized in that, for the shifted imaging of the rastered masks/bitmaps in the construction plane which are produced in a shifted manner in the sub-pixel range for the purpose of selectively hardening of the material layer, a cardanic mounted transparent, plane-parallel plate is arranged between the projection unit and the image/construction plane, which plate shifts, by rotation around two axis (XY) which are present in-plane parallel to the image/construction plane, the projection beam path and thus the image in the image/construction plane in the sub-pixel range in X and Y.

18. The process according to claim 1, characterized in that, for the shifted imaging of the rastered masks/bitmaps in the construction plane which are produced in a shifted manner in the sub-pixel range for the purpose of selectively hardening of the material layer, a transparent plane-parallel plate is arranged between the projection unit and the image/construction plane, which plate shifts, by rotation around an axis parallel to a pixel-diagonal, the projection beam path and thus the image in the image/construction plane in the sub-pixel range along the pixel diagonal which is orthogonal thereto.

19. The process according to claim 1, characterized in that, for the shifted imaging of the rastered masks/bitmaps in the construction plane which are produced in a shifted manner in the sub-pixel range for the purpose of selectively hardening of the material layer, the projection unit is maintained fixed in its position, and the projection beam is deflected via a mirror into the image/construction plane, wherein the deflecting mirror is provided with an adjustment possibility (cardanic support) by which the projection beam for each shifted bitmap can be deflected such that a shift of the image in the sub-pixel range is achieved in the image-/construction plane.

20. The process according to claim 1, characterized in that the projected light output for each pixel is varied by “

grey scaling”

within a projection mask, in order to selectively influence the hardening level in a layer thereby and thus to raise the light output of the contour-pixel relative to the light output of the area-pixel, in order to compensate the partial illumination due to partial superimposition of a contour-pixel by the sub-pixel shift of the individual bitmap in the contour portion.

21. A device for the production of a three-dimensional object by layer-wise solidification of a material which is solidifiable under the application of electromagnetic irradiation by means of mask illumination, whereby the irradiation necessary for hardening is imaged into the image/construction plane, wherein the device comprises a rastered, image forming unit for the selective illumination, which is embodied either by line or by matrix,

characterized in that the image forming unit composes the image from individual image dots (pixels) and thus forms a rastered mask (bitmap), wherein the pixels are arranged within the plane in a manner mutually fixed to each other, and that the image forming unit and/or an imaging optic which is provided between the image forming unit and the image/construc-tion plane is/are designed such that a sequence of a multitude of images, which are mutually shifted in a sub-pixel range, can be created, wherein a separate mask/bitmap can be produced for each shifted image.

22. The device according to claim 21, characterized in that said image forming unit for the selective illumination is embodied by a matrix.

23. A device according to claim 21, characterized in that a series of at least 2 images, which are mutually shifted in a sub-pixel range, can be created in the image/construction plane.

24. A device according to claim 21, characterized in that said image forming unit is a projection unit.

25. A device according to claim 21, characterized in that said image forming unit is a line, particularly a matrix having discretely emitting elements for image formation.

26. A device according to claim 21, characterized in that the device is provided with actuators in order to shift the whole image forming unit per partial image in a plane-parallel manner towards the image/construction plane in XY in the sub-pixel range.

27. A device according to claim 21, characterized in that the device is provided with actuators which can tilt the image forming unit per shift-generated bitmap such that the individual, shift-generated bitmaps in the image/construction plane are imaged in a manner shifted in the sub-pixel range.

28. A device according to claim 21, characterized in that, between the image forming unit and the image/construction plane, a mirror is arranged as an imaging optic and is

cardanically mounted and is rotatable via actuators such that the beam path is deflected into the image plane and that the individual, shift-generated bitmaps in the image-/construction plane can be imaged in a correspondingly shifted manner in the sub-pixel range.

29. A device according to claim 21, characterized in that,

between the image forming unit and the image/construction plane, a transparent plate having mutual plane-parallel surfaces is arranged as an imaging optic and can be tilted by means of one or more actuators such that the beam path is shifted and that the individual, shift-generated bitmaps in the image-/construction plane are imaged in a manner shifted in the sub-pixel range.

30. A device according to claim 21, characterized in that the image forming projection unit is maintained fixed in its position and that the imaging optic can be shifted in XY in a sub-pixel range of the image forming unit via actuators such that the desired shift of the image in the image-/construction plane in a sub-pixel range is achieved.

31. A device according to claim 21, characterized in that the image forming projection unit is maintained fixed in its position and that the imaging optic can be tilted via actuators such that the desired shift of the image in the image/construction plane in the sub-pixel range is achieved.