SYSTEM AND METHOD FOR EXPOSING A MATERIAL WITH IMAGES

Abstract

A system for exposing a material with images includes an exposure table and an electronic light projector arranged above the exposure table. The system is adapted to project images towards a material arranged at the exposure table. The electronic light projector and the exposure table are configured to be moved relative to each other during exposure. The electronic light projector is connected to a projector control unit configured to provide a sequence of images to be exposed represented by image data and superimpose a static image pattern onto the edge sections of the images to be exposed, resulting in a sequence of combined images. The width of the static image pattern is slimmer than the image to be exposed. The electronic light projector is configured to expose the combined images sequentially onto the material.

Claims

1. A system for exposing a material with images, where the system comprises an exposure table and an electronic light projector arranged above the exposure table and being adapted to project images towards a material arranged at the exposure table, where the electronic light projector and the exposure table are configured to be moved relative to each other during exposure and where the electronic light projector is connected to a projector control unit configured to: provide a sequence of images to be exposed represented by image data, superimpose a static image pattern onto the edge sections of the images to be exposed, where the width of the static image pattern is slimmer than the image to be exposed, resulting in a sequence of combined images, and where the electronic light projector is configured to expose the combined images sequentially onto the material.

2. The system according to claim 1, where the images to be exposed are in form of CAD (Computer aided design) image data with a static image pattern superimposed on to the data pattern given by the CAD file on each side of the image area.

3. The system according to claim 1, where the material is a photosensitive or photo polymerizable material.

4. The system according to claim 1, where the electronic light projector is connected to a motor controller providing a synchronization signal to the electronic light projector for controlling the movement of the electronic light projector relative to the exposure table, in order to enable the projector to set up the next image in an image sequence.

5. The system according to claim 1, where the superimposed pattern is fixed while the image data is sequentially presented.

6. The system according to claim 1, where the superimposed pattern on one side of the exposure stripe is complementary to the other side of the adjacent exposure stripe.

7. The system according to claim 1, where the projector control unit is configured to control the superimposition of the static image pattern onto the images to be exposed.

8. The system according to claim 1, where the superimposed pattern has a width between a full projected image width and one projected image pixel.

9. The system according to claim 1, where the superimposed pattern has a length corresponding to number of rows in one projected image.

10. The system according to claim 1, where the superimposed pattern is sawtooth shaped.

11. The system according to claim 10, where the superimposed pattern is stepped sawtooth shaped.

12. A method for exposing a material with images, comprising: providing a sequence of images to be exposed, superimposing a static image pattern onto the edge sections of the images to be exposed, where the width of the static image pattern is slimmer than the image to be exposed, resulting in a sequence of combined images, exposing the combined images sequentially onto the material by means of a light projector, where the electronic light projector and material are moved relative to each other during exposure.

13. The method according to claim 12, where the images to be exposed are in form of CAD (Computer aided design) image data with a static image pattern superimposed on to the data pattern given by the CAD file on each side of the image area.

14. The method according to claim 12, comprising providing a synchronization signal to the electronic light projector for controlling the movement of the electronic light projector relative to the exposure table, in order to enable the projector to set up the next image in an image sequence.

15. The method according to claim 12, controlling the sequence of images to be exposed.

Description

DETAILED DESCRIPTION

[0026] The invention will now be described in more detail and by reference to the accompanying figures.

[0027] FIG. 1 illustrates a system for solidification of photo polymerizable material layers in a 3D printer/rapid manufacturing machine or 2D lithography machine.

[0028] FIG. 2 illustrates the exposure process performed by the system according to the invention.

[0029] FIG. 3 illustrates an ideal situation during exposure where the brightness uniformity over the exposure image from the light projector is ideal, while the positioning of the adjacent exposure stripes are ideal.

[0030] FIG. 4 illustrates a non-ideal situation during exposure where the brightness uniformity causes discontinuity in power between the adjacent exposure stripes.

[0031] FIG. 5 illustrates a resulting power distribution after exposure of overlap zones by use of one embodiment of the system.

[0032] FIG. 6 illustrates a resulting image distribution after exposure of overlap zones having offset in x and y by use of one embodiment of the system.

[0033] FIG. 7 illustrates an example of a CAD image and a superimposed pattern exposed by the electronic light projector onto the material.

[0034] FIG. 8 illustrates one example of a superimposed pattern on the sides of an image to be exposed.

[0035] FIG. 9 illustrates another example of a superimposed pattern on the sides of an image to be exposed.

[0036] FIG. 10 illustrates an example of how the CAD image is exposed to the photosensitive material using two exposure stripes from the image projector

[0037] FIG. 11 illustrates an example of exposure of two adjacent images causing non-exposed areas on the edge between the exposure stripes.

[0038] FIG. 12 illustrates another example of exposure of two adjacent images causing non-exposed areas on the edge between the exposure stripes.

[0039] In FIG. 1 it is illustrated a system 10 for exposing a photosensitive or photo polymerizable material 11 layer by layer to build a 3D object or for 2D direct imaging lithography.

[0040] The system comprises an exposure table 12 and an electronic light projector 13 arranged above the exposure table 12. The electronic light projector 13 can emit light 14 towards the exposure table 12 and thus onto any medium 11 arranged on the exposure table 12, thereby projecting an image onto the medium. The medium 11 is for example a photosensitive or photo polymerizable material. The electronic light projector 13 moves relative to the exposed material 11, while a synchronization signal 15 is provided by a motor controller to enable the projector to set up the next image in an image sequence.

[0041] The electronic light projector comprises a space modulator e.g. a DLP/LCD/LCOS or similar light/power projector which acts as the curing light/power source for the solidification of photo polymerizable material layers in a 3D printer/rapid manufacturing machine or 2D lithography machine (Direct Imaging exposure machine). The process is executed as the projected image is in motion relative to the exposed material, thereby creating adjacent data exposure stripes, as illustrated in FIG. 2. The exposure stripes 21, 22 overlap slightly, thus providing an overlap zone 23.

[0042] The power distribution over the image (brightness uniformity) is a critical parameter for projectors used in motion systems when multiple exposure stripes are required. FIG. 3 illustrates an ideal situation where the power and image positioning are correctly aligned, thus providing a uniform combined exposed image 30.

[0043] If the brightness uniformity is not within certain tolerances, depending on the sensitivity of the exposed material, this will be very noticeable when comparing with the adjacent exposure stripe, either if one or multiple projectors are used. This will provide a discontinuous step 41 in the polymerized result of the exposed material on the edge between the adjacent stripes. FIG. 4 illustrates this situation.

[0044] Also, if the mechanical alignment tolerances of the projector(s) relative to the exposed material is not a fraction of a projected pixel size, there will be an offset in image in both x- and y-direction between the exposure stripes. This will cause non-exposed areas or over-exposed areas on the edge between the exposure stripes if the adjacent exposure stripes are overlapping. Examples of such situations are illustrated in FIGS. 11 and 12.

[0045] When exposure during motion in a motion system covers areas wider than the images by moving in both y-direction and x-direction on the machine, the process will smear out the power difference, and image offset difference between the exposure stripes are smeared over a shared zone between the exposure stripes. This can be called an edge blending area. This smearing will ensure that any difference in power or pixel edge between the exposure stripes will not have a discontinuous character, but a continuous character. FIG. 5 and FIG. 6 illustrates this situation. The example in the figures shows two exposure stripes 51, 52, where the projected image of the second stripe 52 is offset in both x- and y-direction relative to the projected image of the first stripe 51. The image in the overlap zone 53 is thus a blending of the edges of the two image stripes, where the power distribution in the overlap zone is smeared out. In FIG. 5 the power curves 54, 55 representing the two exposure stripes 51, 52 are illustrated. The resulting power curve 53 of the overlap zone is thus a smooth, continuous curve. This continuous character will improve the exposure result quality. The process can also be used when multiple light projectors are used in the same system with only one axis (y axis) or with two axes (x and y axis), creating adjacent exposure stripes.

[0046] FIG. 7 illustrates an example of an image exposed by the electronic light projector onto the material. The image may for example be in form of CAD (Computer aided design) image data 72 with a static image pattern 71 superimposed on to the data pattern given by the CAD file on each side of the image area. The width of the static image pattern 71 can be varied, depending on the requirements of the particular application. In extreme cases, the width of the pattern can be as wide as the image or exposure stripe, while minimum width is one image pixel. Typically, the pattern width will be the same as general tolerances for mechanical equipment for use in such applications, i.e. 20-200 μm

[0047] The superimposed pattern is undergoing a logical “AND” operation with the data pattern given by the CAD file on a pixel by pixel basis as the CAD file data pattern is scrolling over the projector image synchronized with the relative motion of the table where the exposed material is placed.

[0048] The sides 71 of the image area constitute an intentional overlap zone between the adjacent exposure stripes. The part of the image that is included in the overlapping zone contains a superimposed image pattern. The data pattern given by the CAD file will be identical on the adjacent exposure stripes inside the overlapping zone, so that right side of a first exposure stripe inside the overlapping zone is identical to left side of a second exposure stripe inside the overlapping zone. The overlapping CAD data between adjacent image stripes is also described in FIG. 10.

[0049] FIGS. 8 and 9 shows two examples of possible shapes of the superimposed pattern. The figures illustrate a section of both the right side of a first exposure stripe and the left side of a second exposure stripe. The superimposed patterns on each side are complementary shaped as described in FIG. 8 and FIG. 9. This ensures uniform power distributing in the overlap zone.

[0050] The superimposed pattern can be customized depending of the character of the exposed polymerized material, in order to get the best continuous exposure result in the area between the exposure stripes. The pattern may be repeated over the image stripe length as shown in FIGS. 7 to 9.

[0051] The superimposed pattern in the image overlap zone between the two adjacent exposure stripes may vary in size (overlapping zone width) orthogonal to the stripe length, depending on the extent of the desired edge blending.

[0052] The superimposed pattern length along the exposures stripe direction is limited by the number of rows in one 1 image (1 DMD height). In the example of FIG. 7, the number is 1080 (HD) or 1600 (WQXGA), but other image resolutions, such as 2160 (4 k) can also be used.

[0053] During the exposure, the superimposed pattern may be fixed while the data pattern given by the CAD file is scrolling/sequentially exposed according to the relative movement between the exposed material and the projector.

[0054] The superimposed pattern may be preprogrammed and superimposed by a projector control unit, which may be connected to or comprised in the projector. The control system may in one embodiment be programmed in an external PC which controls the projector.

[0055] The exposed result by using the system according to the invention provides a continuous power transition between adjacent exposure stripes and a continuous position transition between the adjacent exposure stripes.