Process for the Production of a Three-Dimensional Object With Resolution Improvement by Pixel Shift

• US 20110009992A1
• Filed: 07/30/2010
• Published: 01/13/2011
• Est. Priority Date: 05/10/2004
• Status: Active Grant

• Current Assignee: Envisiontec GmbH (Desktop Metal, Inc.)
• Original Assignee: Envisiontec GmbH (Desktop Metal, Inc.)
• Inventors: El-Siblani, Ali, John, Hendrik, Shkolnik, Alexandr
• Granted Patent: US 7,962,238 B2
• Time in Patent Office: Days
• US Class Current: 700/97
• 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 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 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/construction 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.

2. The device according to claim 1, characterized in that said image forming unit for the selective illumination is embodied by a matrix.

3. A device according to claim 1, 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.

4. A device according to claim 1, characterized in that said image forming unit is a projection unit.

5. A device according to claim 1, characterized in that said image forming unit is a line, particularly a matrix having discretely emitting elements for image formation.

6. A device according to claim 1, 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.

7. A device according to claim 1, 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.

8. A device according to claim 1, 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.

9. A device according to claim 1, 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.

10. A device according to claim 1, 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.

11. A device according to claim 1, 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.

12. A method for generating a bitmap used to guide the projection of electromagnetic radiation from a rastered image forming unit unto the surface of a curable resign, wherein the image forming unit has an image forming matrix, the method comprising:

defining a coordinate system;

providing a vector path defining an interior area, wherein the interior area of the vector path corresponds to an inner contour of the object to be formed from the curable resin;

defining a bitmap comprising a plurality of bitmap grid elements, wherein each bitmap grid element corresponds to a location in the image forming matrix;

superimposing the bitmap onto the coordinate system to define a first bitmap position relative to the coordinate system;

superimposing the vector path on the coordinate system;

calculating a first degree of overlap between each bitmap grid element and the interior area, wherein the first degree of overlap for each grid element corresponds to the area of each bitmap grid element occupied by a portion of the interior area when the bitmap is in the first bitmap position relative to the coordinate system;

shifting the bitmap to a second bitmap position relative to the coordinate system; and

calculating a second degree of overlap between each bitmap grid element and the interior area, wherein the second degree of overlap corresponds to the area of each bitmap grid element occupied by a portion of the interior area when the bitmap is in the second bitmap position relative to the coordinate system.

13. The method of claim 12, further comprising projecting electromagnetic radiation onto the curable resin from the image forming unit based on the first degree of overlap and the second degree of overlap for each grid element.

14. The method of claim 12, wherein the step of projecting electromagnetic radiation onto the curable resin comprises first projecting electromagnetic radiation onto the curable resin such that each location in the image forming unit matrix projects electromagnetic radiation having an intensity that corresponds to the first degree of overlap for the bitmap grid element that corresponds to the image forming unit matrix location and second projecting electromagnetic radiation onto the curable resin such that each location in the image forming unit matrix projects electromagnetic radiation having an intensity that corresponds to the second degree of overlap for the bitmap grid element that corresponds to the image forming unit matrix location.

15. The method of claim 12, wherein each grid element has a length and width, and the step of shifting the bitmap to the second position comprises shifting the bitmap from the first bitmap position to the second bitmap position in the direction of the width by a distance that is less than the width and in the direction of the length by a distance that is less than the length.

16. The method of claim 12, wherein each grid element has a length and a width, and the step of shifting the bitmap to the second position comprises shifting the bitmap from the first bitmap position to the second bitmap position in the direction of the width by a distance that is less han the width.

17. The method of claim 12, wherein each grid element has a length and a width, and the step of shifting the bitmap to the second position comprises shifting the bitmap from the first bitmap position to the second bitmap position in the direction of the width by a distance that is less than the width in the direction of the length by a distance that is less than the length.

18. A method for generating a bitmap used to guide the projection of electromagnetic radiation from a rastered image forming unit onto the surface of a curable resin, wherein the image forming unit has an image forming matrix, the method comprising:

defining a bitmap having a plurality of grid elements, wherein the bitmap corresponds to a portion of an object being formed from the curable resin and each grid element corresponds to a location in the image forming matrix; and

calculating gray scale values for each grid element, wherein each gray scale value corresponds to an intensity of electromagnetic radiation projected from the corresponding location in the image forming matrix.

19. A method for generating a bitmap used to guide the projection of electromagnetic radiation from a rastered image forming unit onto the surface of a curable resin, wherein the image forming unit has an image forming matrix, the method comprising:

providing a portion of an image of the object to be formed from the curable resin;

defining a bitmap, wherein the bitmap has a plurality of grid elements and each grid element corresponds to a location in the image forming matrix;

superimposing the object image on the first bitmap to define a first relative orientation between the object image and the bitmap;

calculating a first degree of overlap between each grid element and the object image when the bitmap is in the first relative orientation;

shifting the bitmap relative to the object to define a second relative orientation between the object image and the bitmap; and

calculating a second degree of overlap between each grid element and the object image when the object image is in the second relative orientation.

20. The method of claim 19, further comprising projecting electromagnetic radiation onto the curable resin based on the first degree of overlap and the second degree of overlap for each grid element.

21. The method of claim 20, wherein the step of projecting electromagnetic radiation onto the curable resin comprises first projecting electromagnetic radiation onto the curable resin such that each location in the image forming unit matrix projects electromagnetic radiation having an intensity that corresponds to the first degree of overlap for the bitmap grid element that corresponds to the image forming unit matrix location and second projecting electromagnetic radiation onto the curable resin such that each location in the image forming unit matrix projects electromagnetic radiation having an intensity that corresponds to the second degree of overlap for the bitmap grid element that corresponds to the image forming unit matrix location.