Electrocrystallochromic display and element

• US 4,982,184 A
• Filed: 01/03/1989
• Issued: 01/01/1991
• Est. Priority Date: 01/03/1989
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: General Electric Company
• Inventors: Kirkwood, John M.
• Primary Examiner(s): Oberley, Alvin E.
• Assistant Examiner(s): Popovici, Dov
• Application Number:
  US07/293,039
• Time in Patent Office: 728 Days
• Field of Search: 340/763, 340/764, 340/757, 340/783, 340/701, 350/163, 350/360, 350/486
• US Class Current: 345/84
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G02B 5/284 of etalon type comprising a resonant cavity other than a thin solid film, e.g. gas, air, solid plates etalons for fibre optic multiplexing G02B6/29358; etalons for spectral measurement G01J3/26
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field

Abstract

A display changes the color of reflected light in response to the value of electrical potential applied to individual pixels of the display. Each pixel includes an array of light reflectors mounted on a corresponding array of electrostrictive elements. In the absence of energization, all the light reflector lie on a common plane and reflect light of all colors. The electrostrictive elements of each pixel in one embodiment are connected to be driven in common by a single potential. Each electrostrictive element of the array of each pixel has an effective length which differs from that of the adjoining elements so that the common voltage results in a differential expansion or contraction. The differential movement results in a separation between adjacent reflectors. When the separation is λ/4 at the wavelength of a color of light, destructive interference cancels that color, whereby physiological effects change the apparent color of the reflected light. In a second embodiment, the voltages applied to adjacent electrostructive elements differ.

Claims

1. A device for controlling the color of light reflected in response to illumination by a polychromatic source of light, comprising:

a reference reflective surface facing said source of light, said reference reflective surface having first and second dimensions, at least said first dimension being on the order of a wavelength of visible light, said reference reflective surface being oriented to reflect light from said source of light;

a first electrostrictive element including a second reflective surface having first and second dimensions, said first dimension of said second reflective surface being on the order of a wavelength of visible light, said second reflective surface being located contiguous with said reference reflective surface, said first electrostrictive element including first and second electrodes adapted for receiving electrical potential, said first and second electrodes being located and spaced on said first electrostrictive element for causing said second reflective surface to move, in response to application of potential across said first and second electrodes, in a direction having at least a component lying along a line joining said source of light with said second reflective surface; and

a controllable source of potential coupled to at least said first and second electrodes of said first electrostrictive element for controllably causing striction of said first electrostrictive element for thereby controllably setting the position of said first reflective surface, said spacing of said first and second electrodes being selected in conjunction with the range of magnitude of said potential so that, at a first magnitude of said potential, said first reflective surface is at the same distance from said light source as said reference reflective surface for thereby reflecting all of said polychromatic light, and also being selected so that if said polychromatic light is white, and if said first reflective surface is caused to be displaced in the direction of said component relative to said reference reflective surface by one-quarter wavelength of red light at a second magnitude of said potential, a tendency to cause destructive interference of red light results in reflection of light of a predominantly blue-green color, if said first reflective surface is caused to be displaced in the direction of said component relative to said reference reflective surface by one-quarter wavelength of green light at a third magnitude of said potential, a tendency to cause destructive interference of green light results in reflection of a predominantly violet color, and, if said first reflective surface is caused to be displaced in said direction of said component relative to said reference reflective surface by one-quarter wavelength of blue light at a fourth magnitude of said potential, a tendency to cause destructive interference of blue light results in reflection of a predominantly yellow color.

2. A device according to claim 1 wherein said polychromatic light is white.

3. A device according to claim 1 wherein said reference reflective surface is mounted on a second electrostrictive element, said second electrostrictive element including first and second electrodes adapted for receiving electrical potential, said first and second electrodes of said second electrostrictive element being located and spaced on said second electrostrictive element for causing said reference reflective surface to move, in response to application of potential across said first and second electrodes of said second electrostrictive element, in a direction having at least a component of motion lying along a line joining said source of light and said reference reflective surface.

4. A device according to claim 3 wherein said controllable source of potential is coupled to said first and second electrodes of said second electrostrictive element for applying said potential thereacross, said relative location and spacing of said electrodes of said first and second electrostrictive elements being selected as between said first and second electrostrictive elements so that the color of light reflected is controlled in response to the magnitude of said potential.

5. A device according to claim 4 wherein the spacing between said first and second electrodes of said second electrostrictive element is less than the spacing between said first and second electrodes of said first electrostrictive element.

6. A device according to claim 1 wherein said electrostrictive element is crystalline.

7. A device according to claim 6 wherein said crystalline element is quartz.

8. A color-controllable reflective display, comprising:

a plurality of arrayed individually addressable pixels, each of said pixels comprising a plurality of electrostrictive elements, each bearing at least one reflective surface to form an array of reflectors, each of said electrostrictive elements also including first and second electrodes, said first and second electrodes of each of said electrostrictive elements being located and spaced thereon in a manner which differs as between mutually adjacent electrostrictive elements, such that application of the same electrical potential between the first and second electrodes of said mutually adjacent electrostrictive elements results in differential motion of said reflective surfaces borne thereby; and

control means coupled for applying electrical potentials across said first and second electrodes of at least some of said electrostrictive elements of each of said pixels, said potentials applied across said first and second electrodes of said electrostrictive elements within any one pixel being equal, and the potentials applied across said first and second electrodes of electrostrictive elements being independently selectable from pixel to pixel for control of the color reflected thereby.