METHOD FOR INCREASING THROUGHPUT AND REDUCING BLURRINESS DUE TO MOVEMENT

• US 20110273689A1
• Filed: 07/22/2008
• Published: 11/10/2011
• Est. Priority Date: 08/17/2007
• Status: Active Grant

• Current Assignee: Xeikon Prepress NV (ColourOz TopCo)
• Original Assignee: Xeikon IP B.V.
• Inventors: Neber, Sascha, Ebeling, Guido, Hedde, John
• Granted Patent: US 8,643,826 B2
• Time in Patent Office: Days
• US Class Current: 355/67
• CPC Class Codes: B41J 2/465 using masks, e.g. light-switching masks
• CPC Class Codes: B41J 2/471 using dot sequential main scanning by means of a light deflector, e.g. a rotating polygonal mirror
• CPC Class Codes: G03B 27/32 Projection printing apparatus, e.g. enlarger, copying camera
• CPC Class Codes: H04N 1/12 using the sheet-feed movement or the medium-advance or the drum-rotation movement as the slow scanning component, e.g. arrangements for the main-scanningsheet-feed movement by translatory movement of a flat picture-bearing surface H04N1/1008; main-scanning using oscillating or rotating mirrors H04N1/113; using multi-element arrays H04N1/19
• CPC Class Codes: H04N 1/195 the array comprising a two-dimensional array or a combination of two-dimensional arrays
• CPC Class Codes: H04N 2201/0426 Scanning an image in a series of contiguous zones
• CPC Class Codes: H04N 2201/0458 Additional arrangements for improving or optimising scanning resolution or quality

Abstract

The invention relates to a method for illuminating printing plates (5) in which the light from a light source (2) is imaged on a two-dimensional light modulator (4) having a plurality of rows of light-modulated cells (8), and said light is modulated thereby, whereupon the light modulator (4) is imaged on light-sensitive material (5) via an imaging beam path (11), wherein the light-sensitive material (5) is moved relative to the light modulator (4) substantially perpendicularly to the direction of the rows of light-modulated cells (8) at a relative speed and wherein the data pattern to be imaged on the light-sensitive material (5) is displayed beginning in the first row of the light modulator (4) in each row consecutively during a respective exposure time (T, T′) and then moved to the subsequent row of the light modulator (4). In order to improve said method, the invention proposes that the image (10) of the data pattern be held substantially stationary relative to the light-sensitive material (5) during the exposure time (T, T′).

Claims

1. Method for the exposure of printing plates (5), in which light from a light source (2) is imaged on a two-dimensional light modulator (4) with a multiplicity of rows of light-modulating cells (8) and is modulated by this modulator, according to which the light modulator (4) is imaged via an imaging optical path (11) on light sensitive material (5), wherein the light sensitive material (5) is moved substantially perpendicularly to the direction of the rows of light-modulating cells (8) relative to the light modulator (4) at a relative speed and wherein the data patterns to be imaged on the light sensitive material (5), starting in the first utilized row of the light modulator (4), are displayed sequentially in each row in each instance during a holding time (T, T′

), and subsequently are displaced to the in each instance succeeding row of the light modulator (4) until data patterns are pushed out of the last utilized row, at a displacement rate through which the image (10) of a given data pattern is, on average, kept stationary relative to the light sensitive material (5), characterized in that the image (10) of the data pattern during the holding time (T, T′

) is kept substantially stationary relative to the light sensitive material (5).

2. Method as claimed in claim 1, characterized in that the relative movement between the light modulator (4) and the light sensitive material (5) is substantially compensated during the holding time.

3. Method as claimed in claim 2, characterized in that the image (10) of the data pattern is moved relative to the light modulator (4) with a periodic movement profile.

4. Method as claimed in claim 2, characterized in that the movement profile in a space-time representation has a gradual, increasing slope (24) and a steep, decreasing slope (26), in particular a sawtooth shape.

5. Method as claimed in claim 4, characterized in that the movement profile is synchronized with the displacement of the data patterns between the rows, wherein in particular the gradual, increasing slope (24) is executed during the holding time (T, T′

).

6. Method as claimed in claim 2, characterized in that the light source (2) is switched off during the steep, decreasing slope (26).

7. Method as claimed in claim 2, characterized in that all light-modulating cells (8) are switched inactive during the steep, decreasing slope (26).

8. Method as claimed in claim 2, characterized in that the light modulator (4) is mechanically moved, in particular tilted and/or displaced, in order to move the image (10) of the data pattern.

9. Method as claimed in claim 2, characterized in that the imaging optical path (11) is displaced in order to move the image (10) of the data pattern.

10. Method as claimed in claim 9, characterized in that an electric voltage (13) utilizing an electro-optical effect, in particular the Kerr effect, is varied in order to displace the imaging optical path (11).

11. Method as claimed in claim 9, characterized in that a deflection mirror and/or a lens (9) and/or a prism and/or a camera wedge is mechanically moved in order to displace the imaging optical path.

12. Method as claimed claim 9, characterized in that a dispersive element is disposed in the imaging optical path (11) and the wavelength of the light source is modulated in order to displace the imaging optical path (11).

13. Method as claimed in claim 1, characterized in that the light sensitive material (5) is mechanically moved in order to move the image (10) of the data pattern.

14. Method as claimed in claim 1, characterized in that the holding time (T, T′

) is selected shorter than the reciprocal of the displacement rate.

15. Method as claimed in claim 14, characterized in that the light source (2) is operated pulsed and/or the light modulator (4) is periodically switched inactive in order to reduce the holding time (T, T′

).

16. Exposure and modulation arrangement (1) for carrying out the method as claimed in claim 1, with a light source (2), a two-dimensional light modulator (4) with a multiplicity of rows of light-modulating cells (8), with a device (3) for imaging on the light modulator (4), with a device (9) for imaging the light modulator (4) on light sensitive material (5), with a device (6) for generating a relative movement between the light modulator (4) and the light sensitive material (5), wherein the direction of the relative movement extends substantially perpendicularly to the direction of the rows of light-modulating cells (8), as well as with a device (7) for displaying during a holding time (T, T′

) and subsequent displacement of a data pattern through the several columns of the light modulator (4), at a displacement rate, through which the image (10) of a given data pattern is, on average, kept stationary relative to the light sensitive material (5) during the movement, characterized in that it includes means (12, 13) for the compensation of the relative movement between the light modulator (4) and the light sensitive material (5) in order to keep the image (10) of the data pattern during the holding time (T, T′

) substantially stationary relative to the light sensitive material (5).

17. Arrangement as claimed in the preamble of claim 16, characterized in that it includes means (12, 13) for displacing the imaging optical path (11) relative to the light modulator in order to keep the image (10) of the data pattern substantially stationary during the holding time (T, T′

) relative to the light sensitive material (5).

18. Arrangement as claimed in claim 17, characterized in that the means for displacement comprise a mechanically movable optical element, in particular a lens (9) and/or a prism and/or a mirror and/or a camera wedge.

19. Arrangement as claimed in claim 16, characterized in that the means for displacement includes a dispersive element, in particular a grating and/or a prism, and that the light source (2) includes means for varying its wavelength.

20. Arrangement as claimed in claim 17, characterized in that the means for displacement include an electro-optical element, in particular a Kerr cell (12), and that a variable voltage source (13) is provided for activating the electro-optical element (12).

21. Arrangement as claimed in claim 17, characterized in that means for compensation include means for modulating a periodic movement, in particular a piezoelectric drive and/or an oscillator coil, onto the light modulator (4) and/or the light sensitive material (5).

22. Arrangement as claimed in claim 17, characterized in that the means for modulation and/or the means for displacement includes an energy store, which is developed for the storage and output of energy during a periodic movement.

23. Arrangement as claimed in claim 17, characterized in that the means for modulating and/or the means for displacement comprise a solid-body bearing.

24. Method as claimed in the preamble of claim 1, characterized in that the displacement rate is so selected that the quotient of the relative speed and the product of the displacement rate and the height of the light-modulating cells is at least two, in particular two.

25. (canceled)