Multi-beam scanning apparatus

• US 20020085085A1
• Filed: 12/17/2001
• Published: 07/04/2002
• Est. Priority Date: 12/15/2000
• Status: Active Grant

• Current Assignee: Heidelberger Druckmaschinen Ag
• Original Assignee: Heidelberger Druckmaschinen Ag
• Inventors: Fischer, Jorg-Achim, Jacobsen, Thomas
• Granted Patent: US 6,618,070 B2
• Time in Patent Office: Days
• US Class Current: 347/239
• CPC Class Codes: B23K 26/0608 in the same heat affected zone [HAZ] B23K26/0613, B23K26/0619 take precedence
• CPC Class Codes: B23K 26/067 Dividing the beam into multiple beams, e.g. multifocusing
• CPC Class Codes: G02F 1/113 Circuit or control arrangements
• CPC Class Codes: G02F 1/33 Acousto-optical deflection devices circuit or control arrangements therefor G02F1/113
• CPC Class Codes: H04N 1/00278 with a printing apparatus, e.g. a laser beam printer
• CPC Class Codes: H04N 1/0635 using oscillating or rotating mirrors
• CPC Class Codes: H04N 1/1911 Simultaneously or substantially simultaneously scanning picture elements on more than one main scanning line, e.g. scanning in swaths

Abstract

A multi-beam scanning apparatus is provided for use with a recording medium that is located on an at least partially cylindrical inner bearing face of a recording device, in which the bearing face has a cylinder axis. The scanning apparatus includes a scanner unit for scanning the recording medium with at least one exposure beam. The scanner unit includes an acousto-optical element that is either an acousto-optical deflector or an acousto-optical modulator. The scanner unit includes a deflection element that is axially displaceable and rotatable relative to the cylinder axis of the bearing face. The acousto-optical element is mounted to rotate together with the deflection element about the cylinder axis.

Claims

1. A multi-beam scanning apparatus for use with a recording medium located on an at least partially cylindrical inner bearing face of a recording device, in which the bearing face has a cylinder axis, the scanning apparatus, comprising:

a scanner unit for scanning the recording medium with at least one exposure beam;

said scanner unit including an acousto-optical element selected from the group consisting of an acousto-optical deflector and an acousto-optical modulator;

said scanner unit including a deflection element that is axially displaceable and rotatable relative to the cylinder axis of the bearing face; and

said acousto-optical element being mounted to rotate together with said deflection element about the cylinder axis.

2. The multi-beam scanning apparatus according to claim 1, wherein said acousto-optical element is simultaneously actuated with voltage signals at different frequencies on a plurality of channels to split a laser beam, which is delivered from outside said acousto-optical element into said acousto-optical element, into a series of exposure beams.

3. The multi-beam scanning apparatus according to claim 2, wherein the frequencies of the voltage signals are each modulated differently to independently vary intensities of the exposure beams.

4. The multi-beam scanning apparatus according to claim 3, comprising a high-frequency driver for triggering said acousto-optical element with the voltage signals.

5. The multi-beam scanning apparatus according to claim 2, comprising a high-frequency driver for triggering said acousto-optical element with the voltage signals.

6. The multi-beam scanning apparatus according to claim 5, wherein said driver receives a video input signal, and said driver modulates the carrier frequency of each one of the voltage signals in accordance with the received video input signal.

7. The multi-beam scanning apparatus according to claim 6, comprising:

devices for transmitting the voltage signals from said driver to said acousto-optical element;

said devices transmitting the voltage signals in a manner selected from the group consisting of capacitively transmitting the voltage signals and inductively transmitting the voltage signals; and

said driver not rotating.

8. The multi-beam scanning apparatus according to claim 1, comprising:

a non-rotating laser light source feeding a laser beam along the cylinder axis into said acousto-optical element.

9. The multi-beam scanning apparatus according to claim 1, comprising:

a laser light source generating a laser beam having a beam path; and

a device disposed in the beam path upstream of said acousto-optical element;

said acousto-optical element having an optical entry face; and

said device deflecting the laser beam to said optical entry face at a defined angle.

10. The multi-beam scanning apparatus according to claim 9, wherein said device includes an optical wedge.

11. The multi-beam scanning apparatus according to claim 9, wherein said device rotates together with said acousto-optical element.

12. The multi-beam scanning apparatus according to claim 11, wherein said device includes an optical wedge.

13. The multi-beam scanning apparatus according to claim 9, wherein:

said device includes an optical wedge that has a light entry face oriented toward said laser light source;

said optical wedge has a light exit face oriented toward said acousto-optical element;

downstream of said light entry face of said optical wedge, the laser beam diverges away from the axis; and

downstream of said light exit face of said optical wedge, the laser beam extends toward the axis such that the laser beam intersects the axis inside said acousto-optical element.

14. The multi-beam scanning apparatus according to claim 1, comprising:

a laser light source generating a laser beam;

said acousto-optical element having an optical entry face;

the laser beam forming a Bragg angle with a normal to said optical entry face of said acousto-optical element.

15. The multi-beam scanning apparatus according to claim 1, comprising:

a laser light source generating a laser beam having a beam path; and

an optical system, disposed in the beam path upstream of said acousto-optical element, for generating a constriction in the laser beam inside said acousto-optical element.

16. The multi-beam scanning apparatus according to claim 1, wherein:

said exposure beam has a beam path;

said deflection element is disposed in the beam path downstream of said acousto-optical element; and

said deflection element deflects the exposure beam essentially radially outward to the recording medium.

17. The multi-beam scanning apparatus according to claim 1, wherein said deflection element includes a device selected from the group consisting of a mirror, a prism, holographic gratings, diffractive gratings, and a concave mirror.

18. The multi-beam scanning apparatus according to claim 1, comprising:

a projection lens system;

the exposure beam having a beam path; and

said projection lens system disposed in the beam path of the exposure beam downstream of said acousto-optical element.

19. The multi-beam scanning apparatus according to claim 18, wherein said projection lens system is a telecentric projection lens system.

20. The multi-beam scanning apparatus according to claim 1, comprising:

correction devices;

said acousto-optical element being simultaneously actuated with voltage signals at different frequencies on a plurality of channels to split a laser beam, which is delivered into said acousto-optical element from outside said acousto-optical element, into a series of exposure beams;

said correction devices being for correcting an amplitude of each one of the voltage signals to generate a plurality of exposure beams having identical light intensities.

21. The multi-beam scanning apparatus according to claim 20, comprising:

a memory having a matrix of correction values Aij for each of M×

N possible turn-on states of the plurality (n) of the channels, where N=n and M=2ⁿ; and

devices for varying the amplitude of each one of the voltage signals with one of the correction values Aij that are stored in said memory.

22. An internal-drum laser exposure device, comprising:

a recording device having an at least partially cylindrical inner bearing face for a recording medium, the bearing face having a cylinder axis; and

a multi-beam scanning apparatus including;

a scanner unit for scanning the recording medium with at least one exposure beam,

said scanner unit including an acousto-optical element selected from the group consisting of an acousto-optical deflector and an acousto-optical modulator,

said scanner unit including a deflection element that is axially displaceable and rotatable relative to the cylinder axis of the bearing face, and

said acousto-optical element being mounted to rotate together with said deflection element about the cylinder axis.