DEFLECTABLE MEMBRANE OPTICAL MODULATOR

• US 3,746,785 A
• Filed: 11/26/1971
• Issued: 07/17/1973
• Est. Priority Date: 11/26/1971
• Status: Expired due to Term

• Current Assignee: George W. Goodrich
• Original Assignee: George W. Goodrich
• Inventors: Goodrich, George W.
• Primary Examiner(s): Richardson, Robert L.
• Application Number:
  US05/202,432
• Time in Patent Office: 599 Days
• Field of Search: 178/7.3D,7.5D,7.85,7.87,7.88 350/16R,162R,161
• US Class Current: 348/771
• CPC Class Codes: G02B 26/0816 by means of one or more reflecting elements
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field
• CPC Class Codes: H04N 5/66 Transforming electric information into light information scanning details H04N3/00

Abstract

A deflectable membrane optical modulator with an improved substrate for support of the deflectable member is described. The improved substrate supports the deflectable member in close proximity to a parallel contiguously conductive electrode with an array of dielectric pillars of sufficient number and geometrical arrangement so that the supported light reflective deflectable membrane, in the absence of electrostatic forces, forms a mirror with the required optical qualities. The deflectable member is a dielectric membrane and is made reflective by the application of light reflecting materials to its external surface in a manner spatially preserving the dielectric characteristics of the membrane to the same order of magnitude as the spatial resolution defined by the geometrical pattern of the supporting dielectric pillars.

Claims

1. A modulator for modulating incident radiant energy comprising:

a substrate having at least one substantially flat face, and a plurality of dielectric pillars protruding from said substantially flat face, the tops of said pillars defining an optically flat surface;

conductive means along said substantially flat face; and

a continuous, dielectric deflectable member supported on the tops of said pillars, said deflectable member having means along at least one surface of said member for reflecting said incident radiant energy.

2. The modulator of claim 1 further including a perimetrical rim surrounding said substantially flat face for supporting the edge of said deflectable member.

3. The modulator of claim 1 wherein said pillars are arranged in a systematic pattern along said flat face, and the spacings between said pillars exceed the cross-sectional dimensions of said pillars.

4. The modulator of claim 3 wherein said spacing between adjacent pillars is greater than twelve times the wavelengths of the incident radiation.

5. The modulator of claim 4 wherein said spacing between adjacent pillars is approximately twice the cross-section of said pillars.

6. The modulator of claim 4 wherein the distance from the tops of said pillars to said substantially flat face is greater than one half the wavelength of said incident radiant energy so that said deflectable membrane may deflect up to a distance equal to one-half wavelength of the inciDent radiant energy whereby a phase shift up to 360* may be obtained between energy reflected from a deflected area and energy reflected from a nondeflected area.

7. The modulator of claim 6 wherein the distance between the tops of said pillars to said substantially flat face is one to two micrometers.

8. The modulator of claim 6 wherein said substrate is a composite base of chemically resistance rods fused in a matrix of etchable glass with the longitudinal axes of chemically resistant glass rods substantially parallel to each other and wherein said substantially flat face is a chemically etched face of said composite base, said face being substantially normal to the longitudinal axes of said chemically resistant rods, and said dielectric pillars are the unetched sections of said chemically resistant rods protruding from the etched face.

9. The modulator of claim 8 wherein said conductive means along said substantially flat face is a metallic film.

10. The modulator of claim 3 wherein said pillars are positioned at the intersections of perpendicular grid lines.

11. The modulator of claim 3 wherein said pillars are positioned at the corners of a close packed hexagonal pattern.

12. The modulator of claim 1 wherein said dielectric deflectable member is an aluminum oxide membrane.

13. The modulator of claim 12 wherein said reflective means are metallic islands, systematically arranged along the surface of said aluminum oxide membrane, having spacings between said islands small compared to the size of the island.

14. The modulator of claim 13 wherein said metallic islands are substantially equal in area to the smallest area defined by at least three adjacent rods protruding from said composite base.

15. The modulator of claim 13 wherein said metallic islands are less than the area defined by at least three adjacent rods protruding from said composite base.

16. The modulator of claim 15 wherein spacing between said metallic islands is less than one fourth the effective diameter of said metallic islands.

17. The modulator of claim 13 wherein said metallic islands are squares having side lengths approximately four times the spacings between said metallic islands.

18. The optical modulator of claim 1 further comprising:

a source of radiant energy for illuminating the deflectable member;

a vacuum enclosure having at least one optically flat window;

means for emitting a beam of charged particles;

means for modulating said emitted beam of charged particles; and

means for deflecting said modulated beam of charged particles across said deflectable member whereby said beam of charged particles modulated by electrical signals from an external source, deflected across the deflectable member in a predetermined pattern, spatially deposits electrostatic charges on the member causing said member to deflect in the areas where electrostatic charges are deposited and radiation from said radiation source reflected from the deflected area of said deflectable member to be modulated with intelligence representative of the electric signals controlling said beam of charged particles.

19. The optical modulator of claim 18 wherein said source of radiant energy is an incoherent monochromatic light source.

20. The optical modulator of claim 18 wherein said source of radiant energy is a laser.

21. The optical modulator of claim 18 wherein said means for emitting a beam of charged particles is an electron gun.