Printing by active tiling

Abstract

A photosensitive area 11, such as a photolithographic sheet, in an images plane is notionally subdivided in both dimensions to form contiguous (tiled) sub-areas. Variable illumination means 1,4 provides a selected pixellated light pattern, which is directed 8, 9, 10 to fill a selected one of the sub-areas so that pixels of said pattern are, at least 15 microns across at the sub-area, and control means are responsive to an input signal representative of an image conjointly to control the production and direction of the pixellated patterns so that an entire image is produced over all of the said sub-areas. As shown, the variable illumination means comprises a light source 2 with digital micro-mirror array deflector device 4, and the sub-area is selected by lens array 8 with a shutter 10 and polariser array 11 10. The latter may be replaced by a two-axis steering mirror and lens array. An analogue micro-mirror array, optionally with, a kaleidoscope, may be used in the illumination means, with (a) collimating optics and lens array; or (b) a focussing macrolens, for sub-area selection.

Description

bean beam splitter 3 onto a micro-electromechanical array 4 of 1000 by 1000 mirrors each of which can be deflected between two angles. Light 7 reflected from mirrors at one of the angles is lost from the system, but diverging light 5 reflected from mirrors at the other angle and transmitted through the splitter 3 is collimated by a lens 6 and is then incident on a 12 by 12 lens array 8. Each lenticular lens forms a separate image of the array 4.

One such image is selected by a corresponding 12 by 12 array of shutters formed by a liquid crystal array 10 9 of π cells and a 12 by 12 array of (Glan-Taylor polarisers 10 (a single large polariser could be used). Light incident on the liquid crystal array should be polarised, and this is effected either by a separate polariser, for example immediately following the lamp 1, by using a laser source 1,or 1, or by providing a polarising beam splitter 3. In use a selected π cell is activated to rotate the plane of incident light by 90° to enable transmission byte by the corresponding polariser 10 in a known manner so that an image of the whole array 4 is formed on a selected sub-area in an image plane 11.

In operation of the system, an input signal representative of an image which is very large in terms of numbers of pixels, for example 12000 by 12000, is effectively broken down to sub-image signals representative of 12 by 12 contiguous (tiled) sub-images. Each sub-image signal in turn is used to address the mirror array 4, while information concerning the location of the sub-image within the entire image is used to control the shutter array so that the sub-image is directed to the correct location in plane 11, so that eventually the entire image is reproduced in plane 11. The sub-images may be provided in any predetermined order, but preferably immediately adjacent sub-images are formed in immediate succession, for example serially along a first line of 12 sub-images, the serially along succeeding lines, either in the same line direction (as in conventional raster scanning) or in reverse directions (as in boustrophedral scanning).

In use, a photosensitive surface is located in plane 11. Where this surface is for production of a printing mask or plate, e.g. a photoresist layer, it may be necessary to use a UV source 1.

In this system it must be ensured that the light 5 is sufficiently diverging for uniform illumination of the lens array 8. With certain types of light source or illumination optics, or where an alternative type of light modulator replaces the mirror array 4, this may occur naturally, but in other cases additional means known per se are provided to ensure that this happens.

Generally it is preferred to avoid the use of polarisation optics, and FIGS. 2 to 4 have no such requirement. In these Figures the light source may provide polarised (for example laser) or unpolarised light.

In FIG. 2, the diverging light beam 5, is focused by a lens 12 via a mirror 13 and a 12 by 12 lens array 14 onto the imaging plane 11. The mirror 13 is tiltable about two axes so that a selected one of the lenses of array 14 receives substantially all of the sub-image light 5 from the array 4 and produces a corresponding sub-image at its location in plane 11, so that again a complete image may eventually be synthesised thereon by tiling. In this arrangement, the light from source 1 need not be collimated. As shown and preferred, the mirror is planar, but a mirror curved in one or both dimensions could be employed to act in conjunction with lens 13, or even alone (although this requires a larger movable component) for focussing purposes.

FIG. 3 is somewhat similar to FIG. 1, but here the mirror array 4 is replaced by a 2000 by 2000 micro-electromechanical array 15 of mirrors which can be tilted in at least 7 different directions, one direction producing light 7 lost to the system, leaving at least 6 useful directions. In this case the light incident on the mirror array is arranged to be reasonably well collimated, so that light reflected from mirrors of the array set to one of the useful angles is transmitted by the splitter 3 to fall on a corresponding restricted area of a collimating lens 6 and thence to a corresponding one of a 6 by 6 array 16 of lenses illuminating a corresponding local area of plane 11.

In use a sub-image signal is fed to array 15 and its location on the plane 11 is selected in at least a first dimension by selection of the deflection angle of the selected mirrors of array 15. For any sub-image, this deflection angle is selected from the six useful angles, and is common to all selected mirrors for that sub-image. If the mirrors of the array 15 are capable of multi-angle deflection about two axes (six useful direction for each axis), this alone enables selection of the sub-image location in both dimensions, and again the complete image is synthesised by tiling of the sub-images on plane 11.

Alternatively some other manner of providing selecting of the sub-area location in the second dimension must be provided—for example, the position of the photosensitive surface in plane 11 could be changed, the entire mirror array 15 could be rotated about the second axis, or a further steerable deflecting mirror could be located between splitter 3 and lens 6. It will be noted that as illustrated FIG. 3 does away with the need for the shutter array of FIG. 1.

The arrangement of FIG. 4 avoids the requirement for the lens array 16 of FIG. 3 by the use of a kaleidoscope 17 between the splitter 3 and the mirror array 15. Sub-image light emerging from splitter 3 after reflection at array 15 falls onto a local area of a lens 18 in dependence On the deflection angle of the micro-mirrors, and the lens 18 focuses it onto a corresponding local area of plane 11 so that tiling of sub-images in at least one direction may be accomplished. Arrangements for tiling in the second dimension are much the same as those discussed with reference to FIG. 3.

It should be clear to the skilled reader that these embodiments are exemplary only, and that various modification may be made within the scope of the invention defined by the appended claims. For example, although FIGS. 1 and 2 have been described with respect to a two-dimensional placement of each sub-image in plane 11 by control of the shutter array 10, 11 or the two-axis mirror 13, it should be clear that placement in one dimension may be so provided (i.e. a linear shutter array, or a one axis mirror) together with an alternative method of controlling placement in the other dimension. As discussed with respect to FIGS. 3 and 4, this could be provided, for example, by movement of the photosensitive surface, provision of a further one-axis tiltable mirror (so that in FIG. 2 there will be two such mirrors in series), or by tilting of the array 4.

Claims

1. Apparatus for exposing a photosensitive area in an image plane which area is notionally subdivided in both dimensions to form contiguous sub-areas, the apparatus comprising variable illumination means for producing a selected pixellated light pattern, directing means for directing said pattern to fill a selected one of said sub-areas, and control means responsive to an input signal representative of an image conjointly to control said illumination means and said directing means such that the entire image is produced over all of the said sub-areas, wherein said directing means comprises means for replicating said light pattern to form an array of like patterns, and selecting means for selecting one of said patterns for transmission to a corresponding sub-area of said area.

2. Apparatus according to claim 1 wherein said selecting means comprises an array of light shutters.

3. Apparatus according to claim 2 wherein each shutter corresponds to a respective one of said sub-areas.

4. Apparatus according to claim 1 wherein said replicating means comprises a lens array, each lens of said array corresponding to a respective one of said sub-areas.

5. Apparatus according to claim 1 wherein the illumination means is provided by a pixellated light source.

6. Apparatus according to claim 1 wherein the illumination means comprises a light source and a pixellated spatial light modulator.

7. Apparatus according to claim 6 wherein the spatial light modulator is a micro-electromechanical device or a liquid crystal array.

8. Apparatus according to claim 7 wherein the microelectromechanical device comprises a two-dimensional array of tiltable mirrors.

9. Apparatus according to claim 1 wherein the illumination means is optically addressable to produce said light pattern.

10. Apparatus according to claim 1 wherein the illiminanation means is electrically addressable to produce said light pattern.

11. Apparatus according to claim 1 wherein the illumination means and the directing means are separate elements.

12. Apparatus according to claim 1 wherein said pixels are at least 40 microns across at said sub-area.

13. Apparatus according to claim 1 wherein said illumination means provides ultra-violet light.

14. An apparatus as claimed in Apparatus according to claim 1 wherein the pixel size of said pattern is at least 15 μm across at the sub-area.

15. Apparatus for exposing a photosensitive area in an image plane which area is notionally subdivided in first and second dimensions to form contiguous sub-areas, the apparatus comprising variable illumination means both for producing a selected pixellated light pattern and for directing said pattern in a direction corresponding to a selected one of said sub-areas in said image plane, the variable illumination means comprising, in part, a micro-electrochemical micro-electromechanical device in the form of a two dimensional array to of tiltable mirors mirrors, and control means responsive to an input signal representative of an image to control said illumination means such that respective said pixellated light patterns are provided in each of the sub-areas in a sequence, one sub-area at a time, to synthesise synthesize the entire image, wherein the illumination means comprises an array of selectively operable elements, each element being individually capable of directing incident light towards the image plane at any selected one of a plurality of angles in at least the first said dimension so to form a said pixellated light pattern, said selected angle determining at least in part the selected sub-area.

16. Apparatus according to claim 15 wherein each mirror of the array of mirrors is tiltable about two axes to thereby determine the location of the sub-area in both said first and second dimensions.

17. Apparatus according to claim 15 wherein each mirror of the array of mirrors is tiltable about one axis to determine the location of the sub-area in the first said dimension, and light from the array of mirrors is directed to the image plane via a mirror tiltable, about a different axis to determine the location of the sub-area in said the second dimension.

18. Apparatus according to claim 15 wherein each mirror of the array of mirrors is tiltable about one axis to determine the location of the sub-area in the first said dimension, and means are provided for moving the photosensitive area in the image plane to determine the location of the sub-area in the said second dimension.

19. Apparatus according to claim 15 wherein light from said array of mirrors is directed to said image plane via collimating optics and a like array of lenses each corresponding to one of said plurality of angles.

20. Apparatus according to claim 15 wherein light from said array of mirrors is directed to said image plane via a kaleidoscope and a focusing lens.

21. Apparatus according to claim 15 wherein said pixels are at least 40 microns across at said sub-area.

22. Apparatus according to claim 15 wherein said illumination means provides ultra-violet light.

23. An apparatus as claimed in Apparatus according to claim 15 wherein the pixel size of said pattern is at least 15 μm across at the sub-area.

24. A method of exposing a photosensitive area, in response to an input signal representative of an image, said area being notionally subdivided in both dimensions to form contiguous sub-regions, comprising the steps of providing a pixellated light pattern corresponding to a selected part of said image and directing said pattern to fill a corresponding selected one of said sub-regions and repeating the process for other sub-regions until the entire image is produced over all of the sub-regions of said area, said method including the steps of replicating said light pattern to form an array of like patterns, and selecting one of said patterns for transmission to a corresponding sub-area of said area.

25. A method according to claim 24 wherein said photosensitive area comprises a recording medium.

26. A method according to claim 24 wherein said recording material is selectively cured, or selective selectively rendered removable, on exposure to light from said illumination means.

27. A method according to claim 24 wherein said light from the illumination means comprises ultra-violet light.

28. A method of producing a printing plate including the step of performing the method of claim 24.

29. An apparatus as claimed in A method according to claim 24 wherein the pixel size of said pattern is at least 15 μm across at said photosensitive area.

30. A method of exposing a photosensitive area, in response to an input signal representative of an image, said area being notionally subdivided in both dimensions to form contiguous sub-regions, comprising the steps of providing a pixellated light pattern corresponding to a selected part of said image and directing said pattern to fill a corresponding selected one of said sub-regions and repeating the process for other sub-regions, one sub-region at a time, until the entire image is produced over all of the sub-regions of said area, said method including the steps of controlling individual elements of a light modulator array both to produce said pixellated pattern with light and to direct light towards the image plane at any selected one of a plurality of angles thereby to determine at least in part the selected sub-area, the light modulator comprising in part a micro-electromechanical device in the form of a two dimensional array to of tiltable mirors mirrors.

31. An apparatus as claimed in A method according to claim 30 wherein the pixel size of said pattern is at least 15 μm across at said photosensitive area.

32. An apparatus comprising:

illumination means configured to produce a pixellated light pattern and to direct said pattern in a direction corresponding to a selected sub-area in an image plane which is subdivided to form contiguous sub-areas, wherein said illumination means comprises:

a micro-electromechanical device comprised of an array of tiltable mirrors, wherein said pattern is directed to said selected sub-area according to selected deflection angles associated with said array of tiltable mirrors, and

control means configured to control said micro-electromechanical device to sequentially provide a selected pixellated light pattern in each of said sub-areas, one sub-area at a time, to synthesize an entire image comprised of a plurality of pixellated light patterns sequentially formed on the image plane.

33. The apparatus according to claim 32 wherein said illumination means further comprises an array of light emitting diodes.

34. The apparatus according to claim 32 wherein angular deflections of each tiltable mirror comprise any of three or more values.

35. The apparatus according to claim 32 wherein angular deflections of each tiltable mirror comprise any of seven different values.

36. The apparatus according to claim 32 wherein said tiltable mirrors are tiltable about two axes.

37. The apparatus according to claim 32 wherein said illumination means further comprises a beam splitter.

38. The apparatus of claim 32 wherein said plurality of pixellated light patterns are sequentially provided to said sub-areas by varying said deflection angles associated with said array of tiltable mirrors.

39. An apparatus comprising:

a light modulator configured to produce a plurality of pixellated light patterns, wherein said light modulator is configurable with a plurality of deflection angles;

a lens configured to focus a light beam associated with one of said plurality of pixellated light patterns onto a selected sub-area of an image plane; and

a kaleidoscope comprised of multiple internal reflecting surfaces, wherein each of said plurality of pixellated light patterns is sequentially directed onto said image plane by varying the deflection angles associated with said light modulator and by reflecting said light beam on said multiple internal reflecting surfaces to build up a complete image comprised of said plurality of pixellated light patterns.

40. The apparatus of claim 39 wherein said kaleidoscope provides an even illumination of the light modulator.

41. The apparatus of claim 39 wherein said reflection of said light beam on said multiple internal reflecting surfaces results in multiple available images.

42. The apparatus of claim 41 wherein a selection of one of said multiple available images is determined according to an angle of deflection provided by said light modulator.

43. The apparatus of claim 39 further comprising a substantially collimated light source.

44. The apparatus of claim 39 further comprising a beam splitter, wherein said kaleidoscope is positioned between said beam splitter and said light modulator.

45. The apparatus of claim 39 wherein said light beam is directed from the kaleidoscope onto the lens prior to being directed onto said image plane.

46. The apparatus of claim 39 wherein said light modulator comprises an array of tiltable mirrors configured to be pivoted about two axes of rotation.

47. A method comprising:

producing a pixellated light pattern;

directing, by a micro-electromechanical device comprised of an array of tiltable mirrors, said pattern in a direction corresponding to a selected sub-area in an image plane which is subdivided to form contiguous sub-areas, wherein said pattern is directed to said selected sub-area according to selected deflection angles associated with said array of tiltable mirrors, and

sequentially providing a selected pixellated light pattern in each of said sub-areas, one sub-area at a time, to synthesize an entire image comprised of a plurality of pixellated light patterns sequentially formed on the image plane.

48. The method according to claim 47 further comprising varying said deflection angles associated with said array of tiltable mirrors to sequentially provide said plurality of pixellated light patterns to said sub-areas.

49. The method according to claim 47 wherein a first pattern is directed to a first sub-area of said image plane according to a first set of deflection angles associated with said array of tiltable mirrors, and wherein a second pattern is directed to a second sub-area of said image plane according to a second set of deflection angles associated with said array of tiltable mirrors.

50. The method according to claim 49 wherein said second pattern is produced after said first pattern, and wherein said second pattern is different than said first pattern.

51. The method according to claim 47 wherein said image plane comprises a stationary printing plate.