Rotating disc optical synchronization system using binary diffractive optical elements

• US 5,258,862 A
• Filed: 12/10/1992
• Issued: 11/02/1993
• Est. Priority Date: 12/10/1992
• Status: Expired due to Fees

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Harris, Ellis D.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/988,504
• Time in Patent Office: 327 Days
• Field of Search: 359/17, 359/18, 359/565, 359/566, 359/569, 235/457
• US Class Current: 359/17
• CPC Class Codes: G02B 26/106 having diffraction gratings as scanning elements, e.g. holographic scanners holographic optical elements G02B5/32, holography G03H

Abstract

An optical synchronization system uses a stationary binary diffractive optical element and a rotating disc with alternating binary diffractive optical elements and blocking elements to create a moire pattern of a synchronization signal for a pixel clock.

Claims

1. An optical synchronization system for a rotating disc comprising:

a light source for emitting a coherent light beam,

means to collimate said coherent light beam,

a first stationary binary diffractive optical element to alternately block and diffract said collimated light beam,

a plurality of alternating second binary diffractive optical elements and blocking elements disposed circumferentially on said rotating disc such that said diffracted light beam from said first stationary binary diffractive optical element is alternately blocked by said alternating blocking elements and diffracted by said alternating second binary diffractive optical elements as said rotating disc rotates,

reflecting means to reflect said diffracted light beam from said second binary diffractive optical elements on said rotating disc, such that said reflected light beam is alternately blocked by said alternating blocking elements and diffracted by said alternating second binary diffractive optical elements on said rotating disc as said rotating disc rotates, and said diffracted reflected light beam is alternately blocked and diffracted by said first stationary binary diffractive optical element, and

focussing means to focus said double diffracted, reflected light beam onto a photodetector to generate a synchronization signal for rotation of said rotating disc.

2. The optical synchronization system for a rotating disc of claim 1 wherein said first stationary binary diffractive optical element and said plurality of alternating second binary diffractive optical elements and blocking elements have the same diffraction pattern.

3. The optical synchronization system for a rotating disc of claim 1 wherein said means to collimate said coherent light beam and said focussing means to focus said double diffracted, reflected light beam are the same optical element.

4. An optical synchronization system for a rotating disc comprising:

a light source for emitting a coherent light beam,

means to collimate said coherent light beam,

a plurality of alternating first binary diffractive optical elements and blocking elements disposed circumferentially on said rotating disc such that said collimated light beam is alternately blocked by said alternating blocking elements and diffracted by said alternating first binary diffractive optical elements as said rotating disc rotates,

a second stationary binary diffractive optical element to alternately block and diffract said diffracted light beam from said first binary diffractive optical elements,

reflecting means to reflect said diffracted light beam from said second stationary binary diffractive optical element, such that said reflected light beam is alternately blocked and diffracted by said second stationary binary diffractive optical element, and said diffracted reflected light beam is alternately blocked by said alternating blocking elements and diffracted by said alternating first binary diffractive optical element on said rotating disc as said rotating disc rotates, and

focussing means to focus said double diffracted, reflected light beam onto a photodetector to generate a synchronization signal for rotation of said rotating disc.

5. The optical synchronization system for a rotating disc of claim 4 wherein said plurality of alternating first binary diffractive optical elements and blocking elements and said second stationary binary diffractive optical element have the same diffraction pattern.

6. The optical synchronization system for a rotating disc of claim 4 wherein said means to collimate said coherent light beam and said focussing means to focus said double diffracted, reflected light beam are the same optical element.

7. An optical synchronization system for a rotating disc comprising:

a light source for emitting a coherent light beam,

means to collimate said coherent light beam,

a first stationary binary diffractive optical element to alternately block and diffract said collimated light beam,

a plurality of alternating second binary diffractive optical elements and blocking elements disposed circumferentially on said rotating disc such that said diffracted light beam from said first stationary binary diffractive optical element is alternately blocked by said alternating blocking elements and diffracted by said alternating second binary diffractive optical elements as said rotating disc rotates, and

focussing means to focus said double diffracted light beam from said plurality of alternating second binary diffractive optical elements onto a photodetector to generate a synchronization signal for rotation of said rotating disc.

8. The optical synchronization system for a rotating disc of claim 7 wherein said first stationary binary diffractive optical element and said plurality of alternating second binary diffractive optical elements and blocking elements have the same diffraction pattern.

9. An optical synchronization system for a rotating disc comprising:

a light source for emitting a coherent light beam,

means to collimate said coherent light beam,

a plurality of alternating first binary diffractive optical elements and blocking elements disposed circumferentially on said rotating disc such that said collimated light beam is alternately blocked by said alternating blocking elements and diffracted by said alternating first binary diffractive optical elements as said rotating disc rotates,

a second stationary binary diffractive optical element to alternately block and diffract said diffracted light beam from said first binary diffractive optical elements, and

focussing means to focus said double diffracted light beam from said second stationary binary diffractive optical element onto a photodetector to generate a synchronization signal for rotation of said rotating disc.

10. The optical synchronization system for a rotating disc of claim 9 wherein said plurality of alternating first binary diffractive optical elements and blocking elements and said second stationary binary diffractive optical element have the same diffraction pattern.