Optical scanning with phase shifted beam

• US 6,144,483 A
• Filed: 07/02/1999
• Issued: 11/07/2000
• Est. Priority Date: 08/30/1996
• Status: Expired due to Fees

• Current Assignee: Hanger Solutions, LLC (IP Investments Group LLC)
• Original Assignee: Agfa Corporation (Agfa-Gevaert N.V.)
• Inventors: Scholten, Frank, Allen, Roy D.
• Primary Examiner(s): Ben, Loha
• Application Number:
  US09/346,743
• Time in Patent Office: 494 Days
• Field of Search: 359/305, 359/204, 359/211, 359/220, 359/285, 359/209, 359/210, 358/491, 358/493, 250/234
• US Class Current: 359/305
• CPC Class Codes: B41B 19/00 Photoelectronic composing machines
• CPC Class Codes: B41J 2/473 using multiple light beams, wavelengths or colours
• CPC Class Codes: G02B 26/10 Scanning systems
• CPC Class Codes: H04N 1/047 Detection, control or error compensation of scanning velocity or position H04N1/0402 and H04N1/17 take precedence
• CPC Class Codes: H04N 1/053 in main scanning direction, e.g. synchronisation of line start or picture elements in a line
• CPC Class Codes: H04N 1/0607 Scanning a concave surface, e.g. with internal drum type scanners H04N1/0657 takes precedence
• 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
• CPC Class Codes: H04N 2201/02439 Positioning method
• CPC Class Codes: H04N 2201/0471 using dedicated detectors
• CPC Class Codes: H04N 2201/04732 Detecting at infrequent intervals, e.g. once or twice per line for main-scan control
• CPC Class Codes: H04N 2201/04734 Detecting at frequent intervals, e.g. once per line for sub-scan control
• CPC Class Codes: H04N 2201/04744 by detecting the scanned beam or a reference beam
• CPC Class Codes: H04N 2201/0476 using an optical, electro-optical or acousto-optical element
• CPC Class Codes: H04N 2201/04765 using a solid-state deflector, e.g. an acousto-optic deflector
• CPC Class Codes: H04N 2201/04786 Controlling a start time, e.g. for output of a line of data H04N2201/04784 takes precedence
• CPC Class Codes: H04N 2201/04794 Varying the control or compensation during the scan, e.g. using continuous feedback or from line to line

Abstract

A beam scanning system for scanning an imaging surface includes a phase shifter for issuing phase signals, a radiation emitter for emitting a beam of radiation and a deflection element, such as an acousto-optic modulator or translating lens, for deflecting the radiation beam. Depending on the implementation, the emitter can be configured to phase shift the radiation beam and/or the deflection element can be configured to deflect the radiation beam in accordance with the issued phase signals. By emitting and/or deflecting the radiation beam in accordance with the phase signals, the length of the scan line formed on the imaging surface can be controlled. A deflector, such as a spin mirror or rotatable prism, is provided to direct the radiation beam to form a scan line on the imaging surface.

Claims

1. A beam scanning system for scanning an imaging surface, comprising:

a phase shifter configured to issue phase signals;

a radiation emitter configured to emit a beam of radiation in accordance with the issued phase signals;

a deflector configured to direct the emitted beam to form a scan line on the imaging surface.

2. A system according to claim 1, wherein the emitted beam is phase shifted by tan θ

/2 in accordance with the issued phase signals where θ

is an angle of rotation of the deflection element.

3. A system according to claim 1, wherein the issued phase signals control a length of the scan line formed on the imaging surface.

4. A system according to claim 1, further comprising:

a deflection element configured to deflect the emitted beam upstream of the deflector;

wherein the phase signals are first phase shift signals;

wherein the phase shifter is further configured to generate the first phase shift signals and second phase shift signals in accordance with an identical function;

wherein the deflection element deflects the emitted beam in accordance with the second phase shift signals.

5. A system according to claim 4, wherein the deflection element is one of an acousto-optic modulator and a translating lens.

6. A beam scanning system for scanning an imaging surface, comprising:

a radiation emitter configured to emit a beam of radiation;

a deflector configured to direct the radiation beam to form a scan line on the imaging surface;

a phase shifter configured to issue phase signals; and

a deflection element configured to phase shift the radiation beam by tan θ

/2 in accordance with the phase signals, where θ

is an angle of rotation of the deflection element.

7. A system according to claim 6, wherein the deflection element is one of an acousto-optic modulator and a translating lens.

8. A system according to claim 6, wherein the phase shifting of the radiation beam controls a length of the scan line formed on the imaging surface.

9. A beam scanning system for scanning an imaging surface, comprising:

a radiation emitter configured to emit a beam of radiation;

a deflector configured to direct the radiation beam to form a scan line on the imaging surface;

a phase shifter configured to issue phase shift signals; and

a translating lens configured to deflect the radiation beam in accordance with the issued phase shift signals.

10. A system according to claim 9, wherein the phase shift signals represent a phase shift of tan θ

/2, where θ

is an angle of rotation of the deflector.

11. A system according to claim 9, wherein the deflection of the radiation beam in accordance with the phase shift signals controls a length of the scan line formed on the imaging surface.

12. A beam scanning system for scanning an imaging surface, comprising:

a radiation emitter configured to emit a beam of radiation;

a deflector configured to direct the radiation beam to scan the imaging surface;

a detector configured to detect a location of the radiation beam at the deflector and to issue detector signals corresponding to the detected location of the radiation beam; and

at least one of (i) a phase shifter configured to direct phase shifting of the radiation beam in accordance with the issued detector signals and (ii) a deflection element configured to deflect the radiation beam in accordance with the issued detector signals.

13. A system according to claim 12, wherein the detector is configured to detect the location of the radiation beam and to issue the detector signals, the phase shifter is configured to direct phase shifting of the radiation beam in accordance with the detector signals, and the deflection element is configured to deflect the radiation beam in accordance with the detector signals, without the radiation beam being directed to form a scan line on the imaging surface.

14. A system according to claim 12, wherein:

the deflector has a spin axis; and

the detector is a quadrature detector configured to detect a geometric relationship between the radiation beam and one of another beam of radiation and the spin axis of the deflector.

15. A beam scanning system for scanning an imaging surface, comprising:

an emitter configured to emit a beam of radiation having a first circularly polarized beam component and a second circularly polarized beam component;

a beam splitter configured to separate the first beam component from the second beam component;

a deflection element configured to deflect only the first beam component;

a beam combiner configured to combine the deflected first beam component and the second beam component to form a combined radiation beam;

a quarter wave plate configured to phase shift a wavelength of the combined radiation beam;

a spin element configured to direct the phase shifted combined beam of radiation to scan the imaging surface; and

a collimator configured to project the phase shifted first beam component to a first location on the spin element and to project the phase shifted second beam component to a second location, different than the first location, on the spin element.

16. A system according to claim 15, wherein:

the spin element has a spin axis; and

the second location is the spin axis of the spin element.

17. A system according to claim 15, wherein the phase shift is 90°

.

18. A system according to claim 15, wherein the beam splitter is one of a multi-layer dielectric coated mirror and a grating element.

19. A system according to claim 15, wherein the phase shifted first beam component and the phase shifted second beam component have circular polarizations of opposite states.

20. A beam scanning system for scanning an imaging surface, comprising:

at least one emitter configured to emit a first beam of radiation and a second beam of radiation;

an offset element configured to offset the first radiation beam by a first fixed offset angle and the second radiation beam by a second fixed offset angle; and

a spin element configured to receive the offset first radiation beam at a first location corresponding to the first fixed offset angle and the offset second radiation beam at a second location, different than the first location, corresponding to the second fixed offset angle, and to direct the received first radiation beam to form a first scan line on the imaging surface and to direct the received second radiation beam to form a second scan line on the imaging surface.

21. A system according to claim 20, wherein the first and the second fixed offset angles are equal angles in opposed directions.

22. A system according to claim 20, wherein the offset element is one of a dual channel acousto-optic modulator and a beam combiner.

23. A system according to claim 20, wherein the first and the second fixed offset angles are set so that the first scan line and the second scan line are separated by one pixel.

24. A method for scanning an imaging surface, comprising the steps of:

issuing phase shift signals;

emitting a beam of radiation from an emitter which is phase shifted based on the issued phase shift signals; and

directing the phase shifted beam to form a scan line on the imaging surface.

25. A method according to claim 24, wherein:

the phase shifted beam is directed to form the scan line by rotating a deflection element; and

the emitted beam is phase shifted by tan θ

/2, where θ

is an angle of rotation of the deflection element.

26. A method according to claim 24, wherein the phase shifted emitted beam controls a length of the scan line formed on the imaging surface.

27. A method according to claim 24, wherein the phase shift signals are first phase shift signals and further comprising the steps of:

generating the first phase shift signals in accordance with a function;

generating second phase shift signals in accordance with the function; and

deflecting the phase shifted beam in accordance with the second phase shift signals upstream of the imaging surface.

28. A method for scanning an imaging surface, comprising the steps of:

emitting a beam of radiation;

deflecting the radiation beam so as to phase shift the radiation beam by tan θ

/2; and

forming a scan line on the imaging surface with the deflected radiation beam;

wherein the scan line is formed by rotating a deflection element to further deflect the deflected radiation beam, and θ

is an angle of the rotation of the deflection element.

29. A method according to claim 28, wherein the phase shifting of the radiation beam controls a length of the scan line formed on the imaging surface.

30. A method for scanning an imaging surface, comprising the steps of:

emitting a beam of radiation;

issuing phase shift signals;

translating a lens to deflect the radiation beam in accordance with the issued phase shift signals; and

forming a scan line on the imaging surface with the deflected radiation beam.

31. A method according to claim 30, wherein:

the issued phase shift signals represent a phase shift of tan θ

/2;

the scan line is formed by rotating a deflection element to further deflect the deflected radiation beam; and

θ

is an angle of the rotation of the deflection element.

32. A method according to claim 30, wherein the deflecting of the radiation beam in accordance with the issued phase shift signals controls a length of the scan line formed on the imaging surface.

33. A method for scanning an imaging surface, comprising the steps of:

emitting a beam of radiation;

detecting a position of the radiation beam;

performing one of phase shifting and deflecting the radiation beam in accordance with the detected position; and

forming a scan line on the imaging surface with the phase shifted or deflected radiation beam.

34. A method according to claim 33, wherein the detecting is performed without forming the scan line on the imaging surface.

35. A method according to claim 33, wherein the radiation beam is directed by a spin element having a spin axis and the detecting includes detecting a geometric relationship between the radiation beam and one of another beam of radiation at the spin element and the spin axis of the spin element.

36. A method for scanning an imaging surface, comprising the steps of:

emitting a beam of radiation having a first circularly polarized beam component and a second circularly polarized beam component;

separating the first beam component from the second beam component;

deflecting the first beam component;

combining the deflected first beam component and the second beam component to form a combined radiation beam;

phase shifting a wavelength of the combined radiation beam;

projecting the phase shifted first beam component to a first location on the spin element and projecting the phase shifted second beam component to a second location, different than the first location, on the spin element; and

directing the phase shifted first beam component from the spin element to form a first scan line at the imaging surface and the phase shifted second beam component from the spin element to form a second scan line at the imaging surface.

37. A method according to claim 36, wherein the second location is a spin axis of the spin element.

38. A method according to claim 36, wherein the phase shift is 90°

.

39. A method according to claim 36, wherein the phase shifted first beam component and the phase shifted second beam component have circular polarizations of opposite states.

40. A method for scanning an imaging surface, comprising the steps of:

emitting a first beam of radiation and a second beam of radiation;

offsetting the first radiation beam by a first fixed offset angle and the second radiation beam by a second fixed offset angle;

receiving the offset first radiation beam at a first location corresponding to the first fixed offset angle and the offset second radiation beam at a second location, different than the first location, corresponding to the second fixed offset angle; and

deflecting the received first radiation beam to form a first scan line on the imaging surface and deflecting the received second radiation beam to form a second scan line on the imaging surface.

41. A method according to claim 40, wherein the first and the second fixed offset angles are equal in magnitude and different in direction.

42. A method according to claim 40, wherein the first and the second fixed offset angles are set so that the first scan line and the second scan line are separated by one pixel.