Extended resolution light deflector using surface acoustic waves

• US 4,370,030 A
• Filed: 05/27/1980
• Issued: 01/25/1983
• Est. Priority Date: 05/27/1980
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Sprague, Robert A.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): SCOTT JR, LEON
• Application Number:
  US06/153,380
• Time in Patent Office: 973 Days
• Field of Search: 350/356, 350/358
• US Class Current: 359/311
• CPC Class Codes: G02F 1/33 Acousto-optical deflection devices circuit or control arrangements therefor G02F1/113

Abstract

A light modulator/deflector which uses acoustic surface waves wherein an illuminating beam 10 enters the side of and strikes the active surface 18 of a transparent and electrooptic acoustic substrate 12 near the grazing angle of incidence and is reflected off that surface 18 through the remaining portion of substrate 12 and out the other side thereof into at least a zero order undiffracted direction and a first order diffracted direction. The light 10 is collimated so that it interacts with as much of the acoustic wave 20 as possible. A set of interdigital electrodes 16 is evaporated on this surface 18 so as to launch acoustic waves 20 in a direction normal to the plane of incidence of the light. Along the path of the travelling acoustic wave in the same substrate are placed one or more repeater acoustic wave sources 72, 74 to boost the decaying acoustic wave 62 back to its original power level.

Claims

1. In an acousto-optic device comprising a piezo-electric substrate (12) having relatively flat sides, a first set of interdigital electrodes (60) on one side of the substrate (12), said electrodes introducing on the surface of said substrate acoustic waves (62) in response to a predetermined electrical deflector signal (80, 82) applied to said interdigital electrodes, an illuminating light beam (10) introduced into said substrate (12) through a side adjacent to the side with said interdigital electrodes (60), said beam directed at said side at an angle such that the light beam suffers total internal reflection near grazing incidence off the active surface where the acoustic waves (62) are generated, in a plane perpendicular to the direction of travel of the acoustic waves, the output beam being reflected from the active surface containing the acoustic waves and leaving said substrate through the remaining portion of said substrate in a zero order undiffracted direction (92) and a first order diffracted direction (90), wherein the improvement is characterized by:

a second set of interdigital electrodes (72) on the same side of said substrate as said first set of interdigital electrodes (60) and in the path of said acoustic waves introduced on the surface of said substrate by said first set (60) of interdigital electrodes, said second set of interdigital electrodes being positioned in said path of said acoustic waves so as to introduce new acoustic waves of the same frequency and in phase with and thereby amplifying the acoustic waves (62) introduced by said first set of interdigital electrodes.

2. An acousto-optic device as set forth in claim 1, further including;

additional sets (74) of interdigital electrodes on the same side of said substrate as said first (60) and second sets (72) of interdigital electrodes and in the path of said acoustic waves introduced on the surface of said substrate by said first and second sets of interdigital electrodes and positioned in said path of said acoustic waves so as to introduce new acoustic waves in phase with and thereby amplifying the acoustic waves introduced by said first and second sets of interdigital electrodes.

3. The acousto-optic device as set forth in claim 2 wherein the electrical signals (80,82) to the interdigital electrodes (60) vary in frequency between predetermined limits so as to provide a predetermined angular scan of the diffracted output light beam from said substrate.

4. The acousto-optic device as set forth in claim 2 wherein the additional sets of interdigital electrodes operate in response to an electrical signal time delayed and in phase with the original electrical signal.

5. The acousto-optic device as set forth in claim 1 or claim 2 further including another set of interdigital electrodes (64) directly adjacent the first set of interdigital electrodes for introducing on the surface of said substrate second acoustic waves (66) in a second parallel path to and at the same frequency as the original acoustic waves (62), an additional set of interdigital electrodes (68) in the path of said second acoustic waves and directly adjacent to said second set (72) of interdigital electrodes for detecting the phase relationship of said second acoustic waves, and means (70) coupled to said additional set of interdigital electrodes (68) to generate an electrical signal to energize the corresponding set (72) of interdigital electrodes to introduce said new acoustic waves in phase with and amplifying the acoustic waves introduced by said first set of interdigital electrodes.

6. The acousto-optic device as set forth in claim 1 further including a third set of interdigital electrodes (64) directly adjacent said first set of interdigital electrodes for introducing on the surface of said substrate second acoustic waves (66) in a second parallel path to and the same frequency as the original acoustic waves (62).

7. The acousto-optic device as set forth in claim 6 further including a fourth set of inter-digital electrodes (68) in the path of said second acoustic waves and directly adjacent to said second set (72) of interdigital electrodes for detecting the phase relationship of said second acoustic waves, and means (70) coupled to said fourth set of interdigital electrodes (68) to generate an electrical signal to energize said second set of interdigital electrodes (72) to introduce said new acoustic waves in phase with and amplifying the acoustic waves introduced by said first set of interdigital electrodes.

8. An acousto-optic device comprising a piezo electric substrate (12), a first set of interdigital electrodes (60) on one side of said substrate (12), and a second set of interdigital electrodes (72) on the same side of said substrate (12) as said first set of interdigital electrodes (60) aligned in a first direction with said first set of interdigital electrodes, the fingers of said second set of interdigital electrodes being parallel to and spaced apart from said first set of interdigital electrodes.

9. The acousto-optic device as set forth in claim 8, further including additional sets (74) of interdigital electrodes on the same side of said substrate as said first (60) and second (72) sets of interdigital electrodes aligned in said first direction as said first and second sets of interdigital electrodes, the fingers of said additional sets of interdigital electrodes being parallel to and spaced apart from the fingers of said first and second sets of interdigital electrodes.

10. The acousto-optic device as set forth in claim 9, further including another set of interdigital electrodes (64) directly adjacent said first set (60) of interdigital electrodes aligned in a second direction with said first set of interdigital electrodes, the fingers of said another set of interdigital electrodes (64) being parallel to and spaced apart from said fingers of said first set (60) of interdigital electrodes.

11. The acousto-optic device as set forth in claim 10 further including further sets of interdigital electrodes 68 aligned in a third direction parallel to said first direction and including said another set of interdigital electrodes (64), said further sets of interdigital electrodes (68) being directly adjacent to said second set (72) of interdigital electrodes, such that there are at least two rows of sets of interdigital electrodes.